I hope someone can help me on this. We are using a Apogee U55 16 bit, back illum CCD on our telescope. The datasheet for the camera spec. give it a LFW of 400 000 electrons and a dynamic range of 93 dB. It does not however give estimates of the gain and read-noise.
If someone can help me on these numbers. I need them for the photometry pipeline that i am building for our observatory. Rough calculations that I did from equations of the internet gives a gain = 7 epadu and a read-noise = 10 e.
It is amazing the number of tasks and packages available in IRAF. Stumbled apon one while trying to find a procedure/experimental process on how to measure the gain and readnoise for the camara your using.
Task called "findgain" in the noao.obsutil package. For someone learning IRAF it is difficult to know about all these tasks. I expect that if there is time you can go through every package and discover what is available.
These is a Q in there. Is there a site that list all the tasks available and what they do?
Joined: 10 Feb 2006 Posts: 135 Location: Flagstaff
Posted: Thu Jun 07, 2007 1:34 pm Post subject:
You might also gain (no pun intended) by looking through the various IRAF users guides in the documentation. Although written to help people reduce their KPNO and CTIO data, there is a fair amount of general information here as well.
I tried the task several times, using different combinations of images. The results are well different each other.
My questions are:
1) Should I use the same exposure time and filter for the flats?
2) Can I use sky flats instead of dome flats?
3) How do you define the "section" in which the flats are really "flat"? To me, I looked visually at DS9 (color code: b) to define the flattest (i.e. having the same color) region in my flat images.
4) What is the reasonable range for gain and readnoise? My typical findgain result for my CCD is g=0.65 r=1.04 whereas the instrument datasheet provides r=10~15 (I'm trying to determine the gain here).
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