AutoStar CCD Photometry A Step-By-Step Guide by Jeffrey L. Hopkins Hopkins Phoenix Observatory Phoenix, Arizona and Gene A.
Copyright © 2007 Jeffrey L. Hopkins and Gene A. Lucas All Rights Reserved Reproduction or translation of any part of this work [except where specifically noted] beyond that permitted by sections 107 or 108 of the 1976 United States Copyright Act, without permission of the Copyright Owner, is unlawful. Requests for permission or further information should be addressed to: HOPKINS PHOENIX OBSERVATORY, 7812 West Clayton Drive, Phoenix, Arizona 85033-2439 U.S.A.
AUTOSTAR CCD PHOTOMETRY i Preface There are at least two avenues to CCD photometry. First is for someone who knows precisely what they want and digs into learning how to achieve their goal. If they have previous experience with single-channel photometry, the learning curve is much easier. Another avenue to CCD photometry is for the astronomer who starts with visual observing, moves to astrophotography and then to CCD imaging.
ii AUTOSTAR CCD PHOTOMETRY When purchasing a DSI Pro camera, the AutoStar Suite™ telescope control and imaging software is included at no additional cost. While there are other CCD software packages on the market, we decided to see just how useful the AutoStar software would be. Although the Autostar documentation serves to get started in astro imaging, it lacks detail in explaining what is needed to perform photometry; and our first impressions were that we should probably look to other programs.
AUTOSTAR CCD PHOTOMETRY iii TABLE OF CONTENTS Page PREFACE 1. Introduction 1.1 Learning Stages 2. Data Acquisition 2.1 Telescope and Camera Setup 2.2 Software Setup 2.3 Setting Directories 2.4 Taking Dark Frames 2.5 Taking Stellar Images 2.5.1 Imaging Procedure 2.5.2 Flat Fields 3. Raw Data Reduction 3.1 Arranging the Files 3.2 Calibrating the Images 3.3 Differential Magnitude 3.3.1 Setting the Reference Magnitude 3.3.2 Aperture Diameter, Annulus, and Centering Box Size Settings 3.3.
iv AUTOSTAR CCD PHOTOMETRY TABLE OF CONTENTS – APPENDIXES Page A. Modifying a DSI Pro Camera Introduction The Affordable Meade Deep Sky Imager (DSI) Monochrorme Deep Sky Imager Pro (DSI Pro) Adding a Filter Wheel – Installing The Nose Piece Adapter Filter Wheel CCD Photometric Filters Cooling the DSI Pro TEC Cooler Mods Parts List DSI Pro TEC Cooler Modifications Wiring and Schematics Conclusion List of Suppliers for Filters and Cooler Mods B.
AUTOSTAR CCD PHOTOMETRY v TABLE OF CONTENTS – APPENDIXES (Contd.) Page E. Determining BVRI Color Coefficients Introduction Air Mass Terms and Definitions Observational Data Instrumental Magnitude Calculation Extra-Atmospheric Calculations Standard Star Magnitudes Color Transformation And Zero Point Calculations Coefficient Determination Summary F. Least Squares Method Introduction Equations Plotting a Graph and Drawing the Straight Line G. FITS Header Image Information Header Details H.
vi AUTOSTAR CCD PHOTOMETRY LIST OF FIGURES Page 2-1. Meade AutoStar Suite Planetarium Screen -- Selecting DSI Imaging. 2-2. AutoStar Envisage Screen -- Selecting Settings. (Camera Not Connected or Inoperative). 2-3. Settings Window. 2-4. Selecting "Take Darks". 2-5. Take Darks Window. 2-6. Dark Frames Complete Window. 2-7. Envisage Screen With CCD Camera Operating. 2-8. Exposure Setting Window. 2-9. Deep Sky Image Process Window. 2-10. Save Process Window. 2-11. Quality and Evaluation Count Window. 2-12.
AUTOSTAR CCD PHOTOMETRY vii LIST OF FIGURES (Contd.) Page A-5. Standard UBVRI Johnson-Cousins Photometry Filter Passbands. 39 A-6. Views Inside the DSI Pro with Cold Finger (White Square) and Nylon Mounting Screws Shown. 41 A-7. Modified DSI Pro with Focal Reducer, Filter Wheel, TEC/HeatSink/Fan Assembly and Foam Insulation. 42 A-8. Mechanical Modification Drawing and Electrical Schematic.43 B-1. Illustration of a Star's Air Mass (Accounting for Curvature of the Earth’s Atmosphere). 46 B-2.
viii AUTOSTAR CCD PHOTOMETRY LIST OF TABLES Page 3-1. ImageInfo Log Text File Example. B-1. Part of a MICA Table Created for LST at HPO (Phoenix, Arizona) for the Month of October 2005. C-1. Sample Raw ADU Total Flux Data from M67. C-2. M67 BVRI Standard Magnitudes. D-1. Example I and R Observational Data for Star M67-081. D-2. Example V and B Observational Data for Star M67-081. D-3. Calculated Instrumental Magnitudes. E-1. Observational Star Counts. E-2. Instrumental Magnitude Calculations Summary. E-3.
AUTOSTAR CCD PHOTOMETRY 1 1. Introduction Astronomical photometry performed with Charge Coupled Devices (CCDs) has the big advantage of being able to acquire simultaneous data on multiple stars. The sensitivity of the CCD allows short exposures on the brighter stars, and also the ability to work with very faint stars. One disadvantage is the low dynamic range of the CCD camera, compared to single-channel photometry such as using photon counting methods.
2 AUTOSTAR CCD PHOTOMETRY 3. Practicing Photometry – Once you have mastered the imaging steps, you are ready to practice photometry. Pick some stars that are high in the sky when they cross the meridian. The closer to the zenith, the better. The further from the meridian the poorer quality the images will be and thus poorer photometry. Try to plan your observing so that the star is to the East of the meridian and will cross during the observing session. 4.
AUTOSTAR CCD PHOTOMETRY 3 2. Data Acquisition Before any photometry can be done on the star, you must first take suitable images. The following steps describe the procedures developed at Hopkins Phoenix Observatory (HPO) using the Meade® AutoStar Suite™ software and a DSI™ Pro or DSI Pro-II monochrome CCD cameras to acquire photometric images. 2.1 Telescope and Camera Setup Set up the telescope and DSI camera, and connect the cables to your PC. Power up the telescope and align it for tracking.
4 AUTOSTAR CCD PHOTOMETRY The AutoStar Envisage window will then open (Fig. 2-2). After a few moments, if there are problems and the camera image doesn't show up, check the USB connection to the DSI camera. You should use a powered USB 2.0 interface, even though the DSI camera will work marginally with USB 1.0. If problems persist, try another USB cable. Note: A maximum length of 12 to 16 feet (3.5 to 5 meters) is recommended for the USB 2.0 cable connection to the DSI camera. Figure 2-2.
AUTOSTAR CCD PHOTOMETRY 5 2.3 Setting Directories Before going further, you may wish to set the Settings for the image acquisition program (Envisage) for your setup. Select the Settings pull-down menu (Figure 2-3). Figure 2-3. Settings Window. For the Image Directory and Dark Frames Directory, use the default settings or create new ones. (To avoid confusion until you have gained experience, it is suggested to use the default directories.
6 AUTOSTAR CCD PHOTOMETRY 2.4 Taking Dark Frames The following procedure should be performed each evening, prior to starting the imaging. Let the equipment stabilize and adjust to the ambient temperature for at least 15 (ideally 30) minutes before doing this. Dark Frames are used in the software to subtract the inherent noise in the camera electronics from the images. 1. From the Image Process menu select Take Darks. (Fig. 2-4.) Figure 2-4. Selecting "Take Darks".
AUTOSTAR CCD PHOTOMETRY 7 Note: There will be one Master Dark Frame for each exposure 1.0 second or greater (for the times used). You cannot take Dark Frames for exposure times less than 1.0 second; and indeed they normally are not needed for such short exposures. Filters do not enter in for Dark Frames. Since Bias data is part of the Dark Frame, there is no need to take separate Bias Frames. The filter selected does not matter.
8 AUTOSTAR CCD PHOTOMETRY You now have a set of Master Dark Frames for the desired exposure times. These are stored in a folder called Darks located in the Meade Images folder (unless you designated a different folder). 2.5 Taking Star Images When taking stellar images for photometry, one of the great features of CCD imaging with the Autostar Suite software is the ability to automatically take multiple short exposure images and stack them. The images can also be automatically aligned with the software.
AUTOSTAR CCD PHOTOMETRY 9 Figure 2-7. Envisage Screen With CCD Camera Operating. 2. Determine exposure time(s) that allows reasonable maximum count values for the stars of interest, but less than 65,535 counts. (See Fig. 2-7.) This includes both the program and comparison stars, and in each filter. Do not worry if some of the other field star images are saturated. As long as they are not of interest (in the photometry program) and do not overlap the stars that are of interest, it will not matter.
10 AUTOSTAR CCD PHOTOMETRY Figure 2-8. Exposure Setting Window. Note: Live Exp exposure times can be set shorter than 1.0 seconds; and Long Exp times can be set to steps of 1.0, 1.4, 2.0, 2,8, 4.0, 5.7, 8.1, 11.3, 15, .... seconds. You can use the Live exposure time for short exposures (up to 15 seconds). For times greater than 1 second, we suggest using Long Exp. Leave the Live button clicked for now. 4. Check the dark field subtraction box (Dark Sub).
AUTOSTAR CCD PHOTOMETRY 11 6. File Naming -- Note: CCD photometry imaging creates an enormous amount of data very quickly. Each image will be over 1.2 MB. It is very important to develop a systematic approach to handling the data and naming of the files. The following procedures is what is used at HPO and is just a suggestion. You can develop your own technique as long as it works for you. In the Object Name field (Fig.
12 AUTOSTAR CCD PHOTOMETRY 8. Unless the sky is exceptionally steady, leave the image quality (Min Quality %) at 30 and evaluation frames (Evaluation Count) at 5. These default values seem to work well. Check the Combine box. (Fig. 2-11.) Figure 2-11. Quality and Evaluation Count Window. Make sure the images are saved as FITS files and Normal Operation is selected (see Fig. 2-12). Click the Save Procedure button. Figure 2-12. Save Procedure Window. 9.
AUTOSTAR CCD PHOTOMETRY 13 Note: If an Alt/Az mount is used, a second box can be drawn around another star to derotate the field when stacking (combining) the images. Again, do not worry about anything in the Stats Area at this time. That is mostly useful for astro imaging (not photometry). (Fig. 2-15.) Figure 2-15. Stats Area – (May Be Ignored for Photometry). 10. If a long exposure (greater than 1 second) is used, make sure the Long exp check box is selected. (Fig. 2-16.
14 AUTOSTAR CCD PHOTOMETRY 11. Select Start. (Fig. 2-17.) Figure 2-17. Start Button. 12. After at least 10 images have been combined, select Stop. If longer exposure times are used, a lesser number can be stacked. Only images meeting the Min Quality % will be included in the combined stack. If the seeing is poor, it may take several minutes to get 10 good images, even with exposures of just a few seconds. 13. Repeat Steps 11 and 12 two more times to produce a set of three stacked image files.
AUTOSTAR CCD PHOTOMETRY 15 17. Repeat Steps 1 - 16 for each additional set of data points desired (for a time sequence, for instance). Note: Unless changed, the image files will be stored in a folder called Meade Images. Find it and make a shortcut to it and put the shortcut folder icon on the desktop for easy use later. 2.5.
16 AUTOSTAR CCD PHOTOMETRY Note: It is very important that the optical train is not changed between imaging and taking the Flat Fields. This means no moving or adjusting of the camera relative to the telescope and only minor focusing. This is why it is usually best to take flats at the end of a session. If the optical path is not identical for the Flat Field images and the star images, the flat fields will be of no value, as they will calibrate against the wrong pixels.
AUTOSTAR CCD PHOTOMETRY 17 3. Raw Data Reduction This is the stage where the photometric data is extracted from the images. When getting the data from an image, the data will be automatically logged into a text file called ImageInfo.txt. The software does a great deal of the work automatically. 3.1 Arranging the Files The following procedure steps are just suggestions, and you can develop your own scheme, as long as it makes sense and works for you.
18 AUTOSTAR CCD PHOTOMETRY 3.2 Calibrating the Images 1. Click on one of the image files in the new folder. The AutoStar Image Processing program will open the file. 2. Close the file, but not the image processing program. To make working on similar files (taken with the same filter) easier, a Group can be created that will have all of the calibration steps done on the members of the Group automatically. 3. Click on the Group pull-down menu and select New. (See Fig. 3-1.) Figure 3-1.
AUTOSTAR CCD PHOTOMETRY 19 4. Select all the images of a given filter (e.g., the V filter images in the V Raw Data folder). (See Fig. 3-2.) Figure 3-2. Selecting Filter Files to Calibrate with Flat Field. Note: This will create a new text file called ImageGroup.lst. Do not move or rename this file. This is not a text file and cannot be opened. Just let it be, as it defines the files in the Group. 5. From the Group pull-down menu, select Calibrate. (Fig. 3-3.) Figure 3-3. Calibrate Selection.
20 AUTOSTAR CCD PHOTOMETRY 6. A Calibrate window will be displayed (Fig. 3-4) where you can select and include a Bias, Dark Frame, and a Flat field image. If you have used the Auto Dark Subtraction option while taking images, or if the exposure time is less than 1 second, you do not need to use another dark frame. If you have used a dark frame when taking the images, the Bias image is not needed. Figure 3-4. Calibrate Window. Note: This will create a new file called NewImageGroup.lst.
AUTOSTAR CCD PHOTOMETRY 21 Figure 3-5. New Calibrated Image Files. 9. To organize the calibrated files, make a new folder within the current folder. Call this folder “Cal Filter Name Data” (or “Cal V” for the V filter calibrated images). 10. Repeat steps 3 through 9 for each of the other filters. You now have sets of calibrated data ready to have the star magnitudes determined. 3.
22 AUTOSTAR CCD PHOTOMETRY Note: AutoStar automatically adjusts the monitor display contrast; so even if the images look faint, the data should be okay. If the star image is too faint to be easily seen, you can adjust the contrast manually. The adjustment only affects the display. You can also expand the image to full screen if it helps. 3. Start by drawing a small box around the Comparison star. There will be a diagonal line across the (inner) box.
AUTOSTAR CCD PHOTOMETRY 23 You will see the term “centroid” appear many times when reading about CCD photometry. This is a bit of software “magic”. The centroid of a star image is essentially its center of gravity or center of brightness. The CCD software can find this center very precisely. This is important, because when selecting the star for processing, you do not need to select it exactly.
24 AUTOSTAR CCD PHOTOMETRY Note: This will set the Reference magnitude for the Comparison star. This action must be performed with each image. The other star measurements will now produce magnitude values referenced to the Comparison star Reference magnitude that was entered. This will create a new text file in the folder called ImageInfo.txt. All the data that is acquired from the images will be logged into that file.
AUTOSTAR CCD PHOTOMETRY 25 Figure 3-10. Magnitude Determination Window. 8. Click on OK. Do not click on “Log”, as the data will be logged twice. Just click OK. 9. Repeat Steps 1 - 8 for each Program star you wish to know the magnitude of. 10. As a double-check and a way to indicate where you are in the Log file, determine the magnitude of the Comparison star as the last measurement. It should be the same as what was set earlier for the Reference magnitude.
26 AUTOSTAR CCD PHOTOMETRY 12. Repeat Steps 1 - 11 for the other filter images. A text log file called ImageInfo.txt will be created. 3.4 ImageInfo File The ImageInfo.txt file is a text file that is automatically created when determining the magnitudes of the stars. Table 3-1 shows a screen shot of a sample file. Table 3-1. ImageInfo Log Text File Example. The X and Y Center data helps identify which star the data applies to.
AUTOSTAR CCD PHOTOMETRY 27 4. Additional Data Reduction The raw magnitude data now must be used to calculate the average magnitudes and data spread or standard deviations, in addition to calculating the Air Mass and Heliocentric Julian Date (HJD). A Mean time for the set of exposures is also calculated. There are various ways to do this, but since it is time-consuming, it is best to use a computer program.
28 AUTOSTAR CCD PHOTOMETRY This program was created quickly and saves a great deal of work when summarizing the data. The white data fields are data entry fields and the green and black shaded entries are calculated data fields. Data fields have been created for up to 4 program stars. Data fields shaded in blue are global fields used for all the records. The RA and Dec star position values are used in determining the Air Mass and HJD (Heliocentric Julian Date).
AUTOSTAR CCD PHOTOMETRY 29 5. Advanced Data Reduction 5.1 Reducing the Raw Magnitudes to Standard Magnitudes So far all or our work has produced raw (instrumental) magnitudes that are unique to the equipment used to produce them. Raw magnitudes are fine, if you are only interested in changes. Many times, data may be desired to be combined with data taken with other equipment. Calibrating the data to a standard will allow it to be useful. Once calibrated, your data will represent true magnitudes.
30 AUTOSTAR CCD PHOTOMETRY Extinction Coefficients (Not needed for differential photometry) k'vi for (v – i) k'v for v k'vr for (v – r) k'bv for (b – v) k'ri for (r – i) Zero Points (Not needed for differential photometry) ζvi for (V – I) ζv for V ζri for (R – I) ζbv for (B – V) Note: While Extinction and Zero Points are not needed for differential photometry, they are needed to determine the color transformation coefficients.
AUTOSTAR CCD PHOTOMETRY 31 APPENDIXES A. Modifying the DSI Pro Camera 33 B. Calculating the Air Mass 45 C. Determining Standard Star Data 55 D. Determining BVRI Extinction Coefficients 59 E. Determining BVRI Color Coefficients 67 F. Least Squares Method 85 G. FITS Header 89 H. Light Box Design and Construction 91 I. Suggested Projects 99 J.
32 NOTES AUTOSTAR CCD PHOTOMETRY
AUTOSTAR CCD PHOTOMETRY 33 APPENDIX A Modifying the DSI Pro Camera Introduction The color versions of the Meade Deep Sky Imager (DSI) CCD camera cannot be used for astronomical filter photometry, but the monochrome DSI Pro (and DSI Pro-II) can. To do serious work requires some simple modifications to the camera. These modifications include replacing the stock filter slide with a filter wheel (or turret), and adding a simple thermoelectric cooler (TEC).
34 AUTOSTAR CCD PHOTOMETRY The Affordable Meade Deep Sky Imager (DSI) While CCD cameras for astronomical use have been around for more than a decade, it has only been recently that affordable and easy-to-use CCD devices have been made available to the amateur market. Some of the first of these were digital web cams. Some folks figured them out and made modifications that produced surprisingly high-quality results.
AUTOSTAR CCD PHOTOMETRY 35 The set of standard RGB astro imaging filters is provided at extra charge. The advantages of using the DSI Pro with the external filters are that the monochrome camera is more sensitive, and provides better resolution, as well as allowing use of different filters. While the included filter slide could be used to hold photometric filters, it quickly becomes apparent that is not a good idea.
36 AUTOSTAR CCD PHOTOMETRY Note: There are four hex-head screws at the corners of the camera. The hex-head screws hold the camera together. Do not remove those screws for this modification. Figure A-2. DSI Pro Camera with Filter Slide (left) and Low-Profile and Original Nosepiece Adapters (Right). Filter Wheel With the low-profile nosepiece adapter installed on the DSI Pro, the next step is to add a filter wheel. There are several available on the market, ranging from under $100 to over $1,000.
AUTOSTAR CCD PHOTOMETRY 37 Figure A-3. Disassembled ATIK Filter Wheel. CCD Photometric Filters For most photometry, special filters must be used. The red, green, and blue (RGB) astro imaging filters supplied for the DSI Pro and DSI Pro-II cannot be used as photometric filters. These are color interference layer coated (dichroic) filters.
38 AUTOSTAR CCD PHOTOMETRY Figure A-4 shows the ATIK filter wheel disk with BVRI filters installed in positions 1, 2, 3, and 4, respectively. Position 5 could be used for a U filter, but because the CCD camera chip is insensitive in that band, the Meade IR blocking (“Clear”) filter is used, for deep sky imaging or “white light” photometry. Figure A-4. Filter Wheel Disk with BVRI Photometric Filters.
AUTOSTAR CCD PHOTOMETRY 39 Figure A-5. Standard UBVRI Johnson-Cousins Photometry Filter Passbands. Cooling the DSI Pro The DSI series cameras use ambient air cooling. The camera case is equipped with an internal “cold finger” that transmits heat from the CCD chip to the backplate, which acts as an efficient heat exchanger. With cool night time temperatures, these units perform well. However, Dark Frames must still be created and subtracted from each image to get rid of “hot” pixels and thermal noise.
40 AUTOSTAR CCD PHOTOMETRY This cooling modification can be used on all the DSI series cameras. In addition to reducing dark current, electronic cooling increases the camera's sensitivity. TEC Cooler Mods Perhaps the most effective way to cool the CCD is by using a Peltier Junction Thermoelectric Cooler (TEC). Peltier Junction TECs are fascinating devices. They consist of a sandwich of semiconductors connected in parallel, between two metallic plates.
AUTOSTAR CCD PHOTOMETRY 41 Parts List The following List of Parts, available from All Electronics is recommended. (Catalog prices listed are as of Spring 2007): Part Name 40 mm 12VDC Thermo Electric Cooler Heat Sink with 12 VDC Fan 12 VDC, 3.5A Power Supply Tube of Thermal Grease P/N PJT-7 CF-215 PS-1231 TG-20 Price $14.75 $7.50 $15.85 $4.25 You will also need several 6-32 x 1 inch nylon (non-conducting) screws, some wire, and a power connector.
42 AUTOSTAR CCD PHOTOMETRY Now place the center of the TEC (against the camera back) so it is directly opposite the cold finger (on the inside of the case). Drill and tap 2 (or 4) matching holes through the camera case and into the heat sink. Make sure the hole spacing is sufficient to clear the TEC. Use two nylon (or non-conductive) screws to hold the heat sink/TEC to the back of the camera.
AUTOSTAR CCD PHOTOMETRY 43 Wiring and Schematics The polarity of the TEC is a bit ambiguous, but you can’t damage it by reversing the connections. After connecting the power supply, check to verify which side gets “hot” and place that side against the finned heat sink (away from the camera back). Don't forget to apply ample thermal grease between the TEC plates and the camera back, and also to the finned heatsink.
44 AUTOSTAR CCD PHOTOMETRY Conclusion With the addition of BVRI photometric filters and a few simple modifications, the monochrome DSI Pro and DSI Pro-II CCD cameras can be used for serious astronomical photometry. Beware, photometry can be addictive, but very rewarding. List Of Suppliers for Filters and Cooler Mods (Note: This list is provided for information only.) Low-Profile Nose Piece TEE Thread Adapter, from Scope Stuff: http://www.scopestuff.com/ss_dsif.
AUTOSTAR CCD PHOTOMETRY 45 APPENDIX B Calculating the Air Mass Introduction The listed corrected magnitudes of stars are given as they would be seen outside the Earth's atmosphere. These values are the values found in books and tables that list a star's extraterrestrial magnitude. When starlight passes through the Earth's atmosphere, it is diminished by a variable factor. This attenuation, known as atmospheric extinction, is caused by absorption of some of the starlight by the atmosphere.
46 AUTOSTAR CCD PHOTOMETRY Getting Started A star's Air Mass, X, is the effective path length of air through which starlight has passed to reach the observer. By definition, X = 1.00 at the Zenith (straight overhead) and increases as one observes stars closer to the horizon. Letting Z be the angular distance of a star from the Zenith (0° ≤ Z ≤ 90°), then the simplest relationship is: X = sec Z This would be correct if the Earth and its atmosphere were flat.
AUTOSTAR CCD PHOTOMETRY 47 Two equations are in common use that take into account not only the curvature, but also the refraction, of the Earth’s atmosphere: X = secZ (1 – 0.0012 (sec2Z – 1)) X = secZ – 0.0018167 (secZ – 1 ) - 0.002875 (secZ – 1)2 – 0.
48 AUTOSTAR CCD PHOTOMETRY Similarly, a star situated at the South Celestial Pole (SCP) would have δ = –90°, while those between that pole and the celestial equator have declinations of –90° ≤ δ ≤ 0°. NCP + o +30 o o Eq ua to r +90 0 -30 o+ o -90 C 0 el es tri a l Earth o SCP Figure B-2. Illustration of a Star's Declination. Determining a Star's Hour Angle (HA) As illustrated in Figure B-3, The observer's celestial meridian is the north-south line passing directly overhead (i.e.
AUTOSTAR CCD PHOTOMETRY 49 Where: LST is the local sidereal time and α is the star's Right Ascension. The LST is simply the Right Ascension of a star on the observer's celestial meridian at the time of the observation. + 0 hr + East Observer's Meridian (North -South Line) 1.5 hr + West 3 hr Observer's Southern Horizon Figure B-3. Illustration of Star's Hour Angle for Northern Hemisphere Observers Facing The Southern Horizon.
50 AUTOSTAR CCD PHOTOMETRY Where: GMS0hUT is Greenwich Mean Sidereal Time at UT = 00:00:00. Long is the Longitude of the observer’s site converted from degrees to time from GMT. UT is the Universal Time of the observation. The factor 1.00274 is to convert UT solar time to UT sidereal time. Note: Convert all times to decimal hours: (Hours + minutes/60 + seconds/3600). For example: Kitt Peak National Observatory has a (geodetic) longitude of: –111° 35m 52s or –111.59777778 degrees.
AUTOSTAR CCD PHOTOMETRY 51 It is better to have just one LST per date and location at UT = 00:00:00 and then add or subtract the (UT * 1.00274) to get the LST. This table can be created using the U.S. Naval Observatory Multiyear Interactive Computer Almanac (MICA) 1800 - 2050 program available from Willmann-Bell, Inc. (URL: http://www.willbell.com). Table B-1 shows a sample list of data from MICA. The date and observation location (a different table is needed for different locations) are specified.
52 AUTOSTAR CCD PHOTOMETRY LST Example For 21 October 2005 at UT = 07h 10m 00s or 7.166667 hours. Using the MICA printout shown in Table B-1, the Local Mean Sidereal Time for 21 October 2005 for HPO (Phoenix , Arizona) at Longitude = 112° 13m 22.0s West and Latitude 33° 30m 06.0s North is 18h 29m 16.1843s or 18.487829 hours. LST = 18.4897829 + 1.00274 * 7.1666667 LST = 25.674132 hours Note: To test and adjust LST: If (LST Lookup + UT * 1.00274) ≥ 24, Use: (LST Lookup + UT * 1.
AUTOSTAR CCD PHOTOMETRY 53 Alternatively, the hour angle of a star can be determined directly from the telescope's right ascension setting circle (if so equipped) by noting the difference in right ascension between the star and the meridian. Because the celestial equator intersects the observer's horizon at the due east and west points, a star with δ = 0° (on the celestial equator) is above the horizon for exactly 12 hours; the star rises with HA = –6 hour and sets with HA = +6 hours.
54 AUTOSTAR CCD PHOTOMETRY An example of a FileMaker Pro program printout used at HPO for calculating Air Mass is shown in Figure B-4. Figure B-4. HPO FileMaker Pro Program for Calculating Air Mass.
AUTOSTAR CCD PHOTOMETRY 55 Appendix C Determining Standard Star Data Observing Standard Stars in M67 (NGC2682) To determine color transformation coefficients, the first thing that must be done is to image some standard stars whose BVRI magnitudes are known. During the winter and spring, the open cluster M67 (NGC 2682) provides a good grouping for this purpose. It is best to plan your observing session so that you can observe M67 twice over a long time period during the evening.
56 AUTOSTAR CCD PHOTOMETRY Figure C-1 shows a wide field view of M67, from the First Palomar Sky Survey (POSS I). (Ref: R. Miles, JBAA 108 p. 65, 1998.) The smaller rectangle near the bottom is where the stars of interest lie. The epoch 2000 coordinates for star cluster M67 (NGC 2682) are: RA = 08h 51m 21s , and Dec = +11d 46m 18s. The epoch 2000 coordinates for the area of interest in M67 are: RA = 08h 51m 44s, and Dec = +11d 46m 32s. Figure C-1. M67 Open Cluster Photograph.
AUTOSTAR CCD PHOTOMETRY 57 Figure C-2. M67 CCD Image Taken at HPO. Table C-1 shows sample raw ADU Total Flux counts for the standard stars in M67. These data were taken with 15-second exposures in each filter (sky counts have been subtracted by the software). Table C-1. Sample Raw ADU Total Flux Data from M67. Star ID B M67-081 418581.7 M67-108 162246.7 M67-117 16926.3 M67-124 32157.9 M67-127 7160.0 M67-130 16492.3 M67-134 27774.8 M67-135 38165.5 Filter V R 672151.8 550120.0 816575.1 1321557.5 816575.
58 AUTOSTAR CCD PHOTOMETRY Figure C-3. M67 Finder Chart for Star Identifications. BVRI Standard Magnitudes in M67 Table C-2 lists the BVRI standard magnitudes of the stars in M67 to be used for the calibration. Table C-2. M67 BVRI Standard Magnitudes. Star 081 108 117 124 127 130 134 135 B V B–V R V–R I R–I V–I 9.944 10.024 –0.080 10.064 –0.040 10.092 –0.028 –0.068 11.081 9.711 1.370 10.064 0.707 8.360 0.644 1.351 13.409 12.625 0.784 12.159 0.466 11.721 0.438 0.904 12.576 12.
AUTOSTAR CCD PHOTOMETRY 59 APPENDIX D Determining BVRI Extinction Coefficients Introduction Different photometric equipment and telescope combinations can produce different responses to the same star. For accurate data and data that can be combined with that taken by other observers with other equipment, it is important to use a calibrated photometric system. This means knowing the color transformation coefficients of the system for the equipment.
60 AUTOSTAR CCD PHOTOMETRY Terms and Definitions It is very important to define terms and keep them straight. The following is a list of definitions used in the equations for extinction determination. Measured Data (Standard Star) I Star Counts V Star Counts R Star Counts B Star Counts Calculated Data (Corrected for 1.
AUTOSTAR CCD PHOTOMETRY 61 Where: io, ro, vo, and io are magnitudes corrected for extinction k'vi = (v–i) Extinction Coefficient k'v = (v) Extinction Coefficient k'vr = (v–r) Extinction Coefficient k'bv = (b–v) Extinction Coefficient k'ri = (r–i) Extinction Coefficient X = Air Mass for the observation The BVRI system defined here uses one simple magnitude, V, and four simple color indices, (V – I), (V – R), (R – I), and (B – V).
62 AUTOSTAR CCD PHOTOMETRY One of the suggested stars is labeled M67-081. Tables D-1 and D-2 list the observed counts for M67-081. Note: The following data is used as an example and is not necessarily “real” data. Table D-1. Example I and R Observational Data for Star M67-081. UT 04:55:15 04:58:36 06:15:33 07:21:39 08:15:45 I Filter X 1.0768 1.1055 1.1266 1.2781 1.5278 i Counts 183962 177526 172358 149238 113238 UT 04:50:57 05:11:16 06:10:23 07:16:35 08:10:40 R Filter X r Counts 1.0775 550120 1.
AUTOSTAR CCD PHOTOMETRY 63 Table D-3. Calculated Instrumental Magnitudes. UT 04:55:15 04:58:36 06:15:33 07:21:39 08:15:45 I Filter X 1.0768 1.1055 1.1266 1.2781 1.5278 i –10.2216 –10.1829 –10.1509 –9.9945 –9.6948 UT 04:50:57 05:11:16 06:10:23 07:16:35 08:10:40 R Filter X 1.0775 1.0771 1.1195 1.2617 1.4971 r –11.4109 –11.4074 –11.4010 –11.3809 –11.3563 UT 04:46:24 05:29:26 06:06:26 07:12:15 08:05:45 V Filter X 1.0786 1.0830 1.1145 1.2484 1.4691 v –11.6284 –11.6218 –11.5267 –11.4157 –11.
64 AUTOSTAR CCD PHOTOMETRY Figure D-1. Plot of i versus X. Figure D-2. Plot of r versus X.
AUTOSTAR CCD PHOTOMETRY Figure D-3. Plot of v versus X. Figure D-4. Plot of b versus X.
66 AUTOSTAR CCD PHOTOMETRY The slopes are then determined and are equated to the filter band's extinction coefficient. Summary of Extinction Determination Δ i / Δ X = k'i 0.9000 / 1.5250 = 0.590 k'i = 0.590 Δ v / Δ X = k'v 0.6400 / 1.4690 = 0.436 k'v = 0.436 k'vi = 0.436 – 0.590 k'vi = –0.154 k'vr = 0.436 – 0.549 k'vr = –0.113 Δ r / Δ X = k'r 0.0615 / 1.500 = 0.041 k'r = 0.041 Δ b / Δ X = k'b 0.1880 / 1.1439 = 0.131 k'b = 0.131 k'ri = 0.041 – 0.590 k'ri = –0.549 k'bv = 0.131 – 0.436 k'bv = –0.
AUTOSTAR CCD PHOTOMETRY 67 APPENDIX E Determining BVRI Color Coefficients Introduction Different photometric equipment and telescope combinations can produce different responses to the same star. For accurate data and data that can be combined with that taken by other observers with other equipment, it is important to use a calibrated photometric system. This means knowing the color transformation coefficients of the system and at least an average set of extinction coefficients for the observatory.
68 AUTOSTAR CCD PHOTOMETRY Terms and Definitions Note: (V – I) is used in the following equations, but is actually not necessary, as final values for (V – I) can be determined from the (V – R) and (R – I) values. Observational Data I Star Counts = i counts R Star Counts = r counts V Star Counts = v counts B Star Counts = b counts Calculated Data (Corrected for 1.
AUTOSTAR CCD PHOTOMETRY 69 Because of the volume of data involved, it is suggested that a computer program be developed to handle the calculations. As mentioned earlier, FileMaker Pro is an easy-to-learn database program ideally suited to these tasks. Figure E-1 shows a screen shot of a database developed at the Hopkins Phoenix Observatory (HPO). Figure E-1. Example FileMaker Pro Observational Data Calculations.
70 AUTOSTAR CCD PHOTOMETRY Figure E-2 shows a screen shot of another part of the FileMaker Pro program used at HPO, illustrating the resulting Transformation Coefficient Calculations, ready to plot. Figure E-2. Example FileMaker Pro Transformation Coefficient Calculation.
AUTOSTAR CCD PHOTOMETRY 71 Instrumental Magnitude Calculations Table E-2 lists a summary of the instrumental magnitude calculations. Table E-2. Instrumental Magnitude Calculations Summary. Star ID X i r v b M67-081 1.0809 –10.2216 –11.4109 –11.6284 –11.1142 M67-108 1.0809 –11.8701 –12.3625 –11.8398 –10.0852 M67-117 1.0809 –8.3691 –9.1195 –8.8522 –7.6312 M67-124 1.0809 –8.4447 –9.3652 –9.3191 –8.3280 M67-127 1.0809 –7.9447 –8.8185 –8.6591 –7.6461 M67-130 1.0809 –7.7314 –8.6686 –8.6189 –7.6030 M67-134 1.
72 AUTOSTAR CCD PHOTOMETRY Table E-4. Equations and Extinction Values. Equation Extinction from Appx. D (r–i)o = (r–i) – k'ri * X k'ri = –0.5490 (v–i)o = (v– i) – k'vi * X k'vi = –0.154 (v–r)o = (v – r) – k'vr * X k'vr = –0.113 Vo = v – k'v * X k'v = 0.436 (b–v)o = (b – v) – k'bv * X k'bv = –0.
AUTOSTAR CCD PHOTOMETRY 73 Color Transform and Zero Point Calculations Tables E-6(a), (b), and (c) list the Color Transformation and Zero Point Calculations. These Tables are from a FileMaker Pro database program developed at HPO. Table E-6(a). (R-I) Color Transformation Plot Calculations. Star ID M67-081 M67-108 M67-117 M67-124 M67-127 M67-130 M67-134 M67-135 (R – I) – (r – i)0 0.5698 0.5449 0.5969 0.6070 0.6103 0.6377 0.5424 0.5556 (R – I) –0.0280 0.6440 0.4380 0.2780 0.3280 0.2920 0.3250 0.
74 AUTOSTAR CCD PHOTOMETRY Color Transform Coefficient Equations ((V – I) – (v – i)o) ((V – R) – (v – r)o) ((R – I) – (r – i)o) (V – vo) ((B – V) – (b – v)o) = = = = = (1 – 1 / α) * (V– I) + ζvi / α (1 – 1 / β) * (V – R) + ζvr / β (1 – 1 / γ) * (R – I) + ζri / γ ε * (B – V) + ζv (1 – 1 / μ) * (B – V) + ζbv / μ Where: α is (V–I) Transformation Coefficient β is (V–R) transformation Coefficient γ is (R–I) transformation Coefficient ε is V Transformation Coefficient μ is (B–V) Transformation Coefficient ζv
AUTOSTAR CCD PHOTOMETRY 75 Coefficient Determination Determining α and ζvi A plot of ((V – I) – (v– i)o) versus (V– I) has the slope (1 – 1 / α) and intercept ζvi / α, from which the values for α and ζvi can be calculated. This may seem like a strange technique to find the coefficients, but it maximizes accuracy and makes the independent variable a known standard value. The slope (1 – 1 / α) has a value near zero and can be determined more accurately than the simple slope α.
76 AUTOSTAR CCD PHOTOMETRY Figure E-3. ((V – I) – (v– i)o) versus (V– I) Plot. Slope = (1 – 1 / α) (1 – 1 / α) = [Δ((V – I) – (v– i)o)) / Δ(V – I)] Δ((V – I) – (v – i)o)) / Δ(V – I) = –0.260 / 1.800 (1 – 1 / α) = –0.1444 α = 1 / (1 – (– 0.1444)) α = 0.8738 α is (V – I) Color Coefficient Y-Intercept when MX = 0 is ζvi / α. Y-Intercept = ζvi / α ζvi = α ∗ Y-Intercept ζvi = 1.3400 ∗ 0.8838 ζvi = 1.
AUTOSTAR CCD PHOTOMETRY 77 Determining β and ζvr A plot of ((V – R) – (v – r)o) versus (V – R) has the slope (1 – 1 / β) and intercept ζvr / β, from which the values for β and ζvr can be calculated. The slope (1 – 1 / β) has a value near zero and can be determined more accurately than the simple slope β. Table E-8 lists the data and Figure E-4 shows a plot of the data. The equations are in the form of an equation for a straight line: ((V–R) – (v–r)o) = (1–1/β) * (V – R) + ζvr /β Table E-8.
78 AUTOSTAR CCD PHOTOMETRY Figure E-4. ((V – R) – (v – r)o) versus (V – R) Plot. Slope = (1 – 1 / β) (1 – 1 / β) = [Δ((V – R) – (v – r)o)) / Δ(V – R)] Δ ((V – R) – (v – r)o)) / Δ (V – R) = – 0.1400/1.200 (1 – 1 / β) = –0.1167 β = 1 / (1 – (–0.1167)) β = 0.8955 β is (V – R) Color Coefficient Y-Intercept when MX = 0 is ζvr / β Y-Intercept = ζvr / β ζvr = β * Y-Intercept ζvr = 0.1375 * 0.8955 ζvr = 0.
AUTOSTAR CCD PHOTOMETRY 79 Determining γ and ζri A plot of ((R – I) – (r – i)o) versus (R – I) has the slope (1 – 1 / γ) and intercept ζri / γ, from which the values for γ and ζri can be calculated. The slope (1 – 1 / γ) has a value near zero and can be determined more accurately than the simple slope γ. Table E-9 lists the data and Figure E-5 shows a plot of the data. The equations are in the form of an equation for a straight line: ((R – I) – (r – i)o) = (1 – 1 / γ) * (R – I) + ζri / γ. Table E-9.
80 AUTOSTAR CCD PHOTOMETRY Slope = 1 – 1 / γ) (1 – 1 / γ) = [Δ((R – I) – (r– i)o)) / Δ(R – I)] Δ((R – I) – (r– i)o)) / Δ(R – I) = –0.3200/1.2000 (1 – 1 / γ) = –0.2667 γ = 1 / (1 – 0.2667) γ = 0.7895 γ is (R – I) Color Coefficient Y-Intercept when MX = 0 is ζri / γ Y-Intercept = ζri / γ ζri = γ ∗ Y–Intercept ζri = 0.6860 * 0.7895 = 0.5416 ζri = 0.5416 ζri is (R – I) Zero Point Determining ε and ζv Plotting (V – vo) versus (B – V) produces the slope which is ε and the Y–intercept ζv.
AUTOSTAR CCD PHOTOMETRY Figure E-6. (V – vo) versus ε * (B – V) Plot. Slope = ε ε = Δ(V – v)o / Δ(B – V) Δ(V – v)o / Δ(B – V) = –0.076/1.800 ε = –0.0422 ε is V Band Color Coefficient Y-Intercept when MX = 0 is ζv Y-Intercept = ζv ζv = 22.
82 AUTOSTAR CCD PHOTOMETRY Determining μ and ζbv A plot of ((B – V) – (b – v)o) versus (B – V) has the slope (1 – 1 / μ) and intercept ζbv / μ, from which the values for μ and ζbv can be calculated. The slope (1 – 1 / μ) has a value near zero and can be determined more accurately than the simple slope μ. Table E-11 lists the data and Figure E-7 shows a plot of the data. The equations are in the form of an equation for a straight line: ((B – V) – (b – v)o) = (1 – 1/μ) * (B – V) + ζbv /μ Table E-11.
AUTOSTAR CCD PHOTOMETRY Figure E-7. ((B – V) – (b – v)o) versus (B – V) Plot. Slope = (1 – 1 / μ) (1 – 1 / μ) = [Δ((B – V) – (b – v)o)) / Δ(B – V)] Δ((B – V) – (b – v)o)) / Δ(B – V) = 0.275/1.800 = 0.1528 (1 – 1 / μ) = 0.1528 μ = 1 / (1 – 0.1528) μ = 1.1803 μ is (B – V) Color Coefficient Y-Intercept when MX = 0 is ζbv / μ Y-Intercept = ζbv / μ ζbv = μ ∗ Y – Intercept ζbv = –0.9210 * 1.0871 ζbv = –1.
84 AUTOSTAR CCD PHOTOMETRY Summary Table E-12 gives a summary of the BVRI Color Transformation Coefficients, and Table E-13 summarizes the BVRI Zero Points. Table E-12. BVRI Color Transformation Coefficients. (1 – 1 / α) (1 – 1 / β) (1 – 1 / γ) ε (1 – 1 / μ) -0.1444 -0.1167 -0.2667 0.0422 0.1528 α 0.8738 ζvi / α 1.2400 ζvi 1.21843 β 0.8955 γ 0.7895 ε 0.0422 Table E-13. BVRI Zero Points. ζvr / β ζri / γ ζv 1.3750 0.6860 22.0085 ζvr 0.1231 ζri 0.5416 ζv 22.0085 μ 1.8030 ζbv / μ -0.09210 ζ bv -1.
AUTOSTAR CCD PHOTOMETRY 85 APPENDIX F Least Squares Method Introduction While it is possible to graphically plot data for extinction and color transformation coefficient determination, sometimes it is difficult to decide exactly where to draw the straight line plot.
86 AUTOSTAR CCD PHOTOMETRY Table F-1. Sample Data. N 1 2 3 4 5 6 7 8 9 10 11 Data xi 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 xi2 1.00 1.21 1.44 1.69 1.96 2.25 2.56 2.89 3.24 3.61 4.00 Data yi 0.47 0.43 0.39 0.36 0.33 0.29 0.25 0.21 0.16 0.15 0.12 (xi * yi) 0.470 0.473 0.468 0.468 0.462 0.435 0.400 0.357 0.288 0.285 0.240 N= 11 Σ xi = 16.5 Σ xi2 = 25.85 Σ yi = 3.16 Σ (xi * yi) = 4.346 Calculations: (Σ xi )2 = 272.25 N = 11 Σ xi = 16.5 xiavg = Σ xi / N = 16.5 / 11 = 1.5000 Σ yi = 3.
AUTOSTAR CCD PHOTOMETRY 87 Plotting a Graph and Drawing the Straight Line Figure F–1 shows a manually-plotted line used to determine the slope (b) and Y–intercept (a) values. Figure F–1. Manual Data Plot. From the Graph: Slope: b = ΔY / ΔX = –0.725 / 2 = –0.3625 ΔY / ΔX means the change (delta) in Y divided by the change in X. Y-Intercept: a = 0.
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AUTOSTAR CCD PHOTOMETRY 89 APPENDIX G FITS Header Introduction Images saved as FITS images (.fts files) will have a header automatically created. This header contains useful information about the image. FITS stands for Flexible Image Transport System. Image Information To view an image’s FITS header, open the image and from the Tools pull–down menu select Image Information. (Fig. G-1.) Figure G–1. Image Information.
90 AUTOSTAR CCD PHOTOMETRY Header Details From the Autostar Image Processing menu, at the lower right of the Image Information window, select View FITS Header to see the information for the selected .fts image. (Fig. G-2.) Figure G–2. FITS Header.
AUTOSTAR CCD PHOTOMETRY 91 APPENDIX H Lightbox Design and Construction This section briefly discusses the need for flat fields, alternate methods of imaging flat fields, and the design and construction of a light box.
92 AUTOSTAR CCD PHOTOMETRY (2) "Tee Shirt" Flats – A variant technique employing a white cloth stretched over the front of the telescope, to diffuse the light source. As with dome flats, the light source must not be allowed to shine directly into the telescope. A second stretched cloth diffuser might also be placed over the light source. One advantage is the method may be used during daytime, provided that no light is allowed directly into the optical train.
AUTOSTAR CCD PHOTOMETRY 93 The joints may be attached together using a hot glue gun, or tape (fabric duct tape or packing tape). RTV or silicon adhesive (bathtub caulk) could be used, but the advantage of hot glue is that it dries rapidly, thus the panels don't need to be supported in position for very long. Some attention should be paid to access to the interior, for adjustment of the lights or cleaning. Perhaps a side panel or the top should be arranged for easy removal.
94 AUTOSTAR CCD PHOTOMETRY Light Sources – Small incandescent battery–operated lamps or LEDs are typically preferred, although some heavy–duty designs for larger telescopes in observatories have employed AC lamps and/or fluorescent tubes. Wiring and Electrical Supply – Batteries or low–voltage AC transformer adapters may be used, with the lamps or LEDs wired either in series or parallel. Some designs feature adjustable voltage to control the illumination.
AUTOSTAR CCD PHOTOMETRY 95 Plans and Further Details Details of light box construction are shown in the photographs following, and a suggested layout plan may be seen on the HPO web pages. (URL: http://www.hposoft.com/Astro/astro.html ) A web search on “CCD light box flats” will yield a number of examples of light boxes successfully used in CCD imaging that will be useful for photometry.
96 AUTOSTAR CCD PHOTOMETRY Joins in the cardboard material have not given any problem in the flat field images. The box is just large enough in width to accommodate the 13.25 inch (33.65 cm) outside diameter front cell of the LX200 telescope corrector lens. The inside length is approximately the same as the width (a cube). Three small spring wire feet slide into the cell to hold the light box in place when taking flat field exposures.
AUTOSTAR CCD PHOTOMETRY 97 Attached on the inside corners of the bulkhead are four small incandescent lamps with attached power wires. (Fig. H-3.) Small pieces of white paper in the corners serve to block the light from impinging directly upon the diffuser sheet, and help direct the light upward, inside the box. The wiring for the four lamps is soldered together and connected to a 9VDC battery, which is simply hung on the outside of the box, and unplugged when not in use. No voltage regulation is used.
98 AUTOSTAR CCD PHOTOMETRY Figure H-4. Typical Light Box Flat Field (V Filter), Showing Artifacts Due to Dust Particles on the Optical Train. Figure H-5. Typical Twilight Sky Flat, Showing Mostly Uneven Illumination, But Some Artifacts Are Also Present.
AUTOSTAR CCD PHOTOMETRY 99 APPENDIX I Suggested Projects Introduction There are many types of astronomical photoelectric photometry projects. Some of the projects an amateur might consider are Lunar photometry, solar photometry, planetary photometry, planetary satellite occultation photometry, asteroid photometry, comet photometry, deep sky photometry (including Novae, Supernovae, and galactic photometry), and several varieties of stellar photometry.
100 AUTOSTAR CCD PHOTOMETRY Lists of the brighter lunar occultations occurring during the year are published in SKY and TELESCOPE magazine and the RASC Observers Handbook. The International Occultation Timing Association (IOTA) is another good source of information about upcoming events and techniques. (See the References section of this book for more information.) Solar Photometry Solar photometry offers some unique challenges. Certainly only a small telescope is needed.
AUTOSTAR CCD PHOTOMETRY 101 Comet Photometry With each appearance of a new comet, interest in comet photometry is revived. This is a very specialized form of photometry, and special filters are usually needed to acquire data on the gaseous emissions. The photometrist with a UBV or BVRI photometer can still make valuable observations, however. Before getting too far into comet photometry, it is advisable to contact some of the comet photometry experts. (See the References section.
102 AUTOSTAR CCD PHOTOMETRY Eruptive Variables The eruptive variables tend to produce sudden, unpredictable outbursts of energy. Examples are Flare stars (Cataclysmic Variables), Novae, and Supernova types. Amateurs have done yeoman duty in coordinating ground-based observations with professionals, as sort of an “early warning” network to help schedule space satellite observatories. Extrinsic Variables These stars exhibit light variations caused by external reasons, e.g.
AUTOSTAR CCD PHOTOMETRY 103 APPENDIX J References Reference Miles, R., “UBVRI photometry using CCD cameras,” JBAA 108 2, 1998, pp. 65-74. (Reference magnitudes and finding charts for M67.) Books and Software Beginning to Intermediate Level Note: The following books and software listed are available from Willmann-Bell, Inc. URL: http://www.willbell.com. Astronomical Photometry - Arne Henden and Ron Kaitchuck. A classic, comprehensive text. (Recently out of print.
104 AUTOSTAR CCD PHOTOMETRY Web Resources AAVSO Julian Day Calculator - On-line JD conversion. http://www.aavso.org/observing/aids/jdcalendar.shtml Eclipsing Binary Star Predictions - On-line elements generator. (J.M. Kreiner, 2004, Acta Astronomica, 54, 207-210) http://www.as.ap.krakow.pl/ephem/ORI.HTM SIMBAD - On-line astrophysical object reference data source. http://simbad.u-strasbg.fr/simbad/ Smithsonian/NASA-ADS Astrophysical Data Service On-line library of abstracts and scanned journal articles.
AUTOSTAR CCD PHOTOMETRY 105 HPO - Hopkins Phoenix Observatory Epsilon Aurigae 2009 Campaign http://www.HPOSoft.com/Astro/astro.html Newsletter and coordination of observations of Epsilon Aurigae during upcoming 2009-11 eclipse season, headed by Dr. Robert Stencel, U. of Denver and Jeff Hopkins, Hopkins Phoenix Observatory. IOTA - International Occultation Timing Association http://www.occultations.org On-line lunar and asteroid occultation predictions, maps, expedition/observing coordination.
106 AUTOSTAR CCD PHOTOMETRY RASC - Royal Astronomical Society of Canada http://www.rasc.ca Publishers of annual Observers Handbook with occultation predictions. Variable star section observing programs, charts. RASNZ-VSS - Royal Astronomical Society of New Zealand Variable Star Section. http://www.rasnz.org.nz/vss/vss.html Active coordination of variable star observations in southern hemisphere. SAS - Society for Astronomical Sciences. http:www.socastrosci.
AUTOSTAR CCD PHOTOMETRY 107 INDEX Page(s) A B C a, Y-Intercept Value 85 α (alpha) – see Right Ascension 48 α (alpha) – see Transformation Coefficients 29 AAVSO (American Association of Variable Star Observers) 103 Adirondack Astro Video 36, 44 Adapter, threaded, low profile nose piece 35 ADUs (analog-to-digital units) 10 Advanced Data Reduction 29 Air Mass, X 45, 53, 59, 67 All Electronics (parts supplier) 41, 44 Alt/Az (Altitude/Azimuth) Mounting 1, 13 Annulus, Setting 24 Aperture, Setting 24 Arrangin
108 AUTOSTAR CCD PHOTOMETRY INDEX (Contd.
AUTOSTAR CCD PHOTOMETRY 109 INDEX (Contd.
110 AUTOSTAR CCD PHOTOMETRY INDEX (Contd.) Page(s) H I J K L HA (Hour Angle) 47, 48, 52 HAD (Hole Accumulation Diode) CCD 34 HJD (Heliocentric Julian Date) 27, 28 Histogram 15 HPO (Hopkins Phoenix Observatory) 3, 68, 69, 95, 104 Image Directories 5 Image Files 17, 89 ImageGroup.lst file 19 ImageInfo.
AUTOSTAR CCD PHOTOMETRY 111 INDEX (Contd.
112 AUTOSTAR CCD PHOTOMETRY INDEX (Contd.
AUTOSTAR CCD PHOTOMETRY 113 INDEX (Contd.) Page(s) Stop Command Checkbox Supernova (SNe) Suppliers, List of T U V W X Y Z 14 102 44 Table of Contents iii Take Darks Command 6, 7 Taking Stellar Images 8 TEC (Thermoelectric Cooler) 33, 40, 41, 44 Tee Shirt Flats 92 TEE Thread Adapter, Camera Nosepiece 35, 44 Temperature Conversion Box 5 Tracking Box 12 Tracking Reference Star 12 Transformation Coefficients 29 Twilight Sky Flats 91, 98 U Band, Filter Not Needed with CCDs USB 2.
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AUTOSTAR CCD PHOTOMETRY NOTES 115
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