Specifications

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. For accurate CCD
photometry, the comparison and program stars must be within one
or two magnitudes of each other. Photometric imaging is very
similar to regular astro imaging, except the images are taken
through special photometric filters.
1.1 Learning Stages
1. Learning the equipment – telescope, mount, camera, and
software. While most any telescope can be used, reflectors are
favored. For the telescope mounting, a fork mount will be superior
to a German Equatorial Mount (GEM). This is because the best
photometry is performed near the meridian (straight overhead) and
that is where the GEMs are weakest, as they must do a “meridian
flip” to continue tracking past the meridian. A fork mount has no
such problem. A polar/equatorial mounted telescope is preferred to
an altitude/azimuth (Alt/Az) mount, although it is certainly
possible to do photometry with an Alt/Az mounted telescope. A
permanent setup is preferred. If the telescope and camera/filter
equipment is removed each night, setting up and aligning can take
a fair amount of time. Some protection against wind and stray light
is useful. But horizon-to-horizon visibility is not needed. At the
most, plus and minus 60 degrees (a cone of 120 degrees with the
telescope at the vertex) from the zenith would be fine. In fact, plus
and minus 30 degrees will work well most of the time, as that is
the best region for photometry.
2. Learning to take good images of star fields involves taking
Dark and Flat Fields and using them to calibrate the images.