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exercise4

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astrojim54624
exercise4

i am just getting started in photometry so i do not really have a procedure. so here is how i think it should go.

open dome in late afternoon and start up electronics

about 1.5 hours before sunset start camera cooling

take twilight flats as soon as possible

start taking data images when the sky is dark enough

if observations are run all night take dawn flats

i plan on making a master dark library and replacing these every 3 months or so

dark subtracting and flat fielding with ccdsoft

final analysis is going to be with aipwin or mpo canopus/photored

as i said in the beginning i am new to this so if anybody has any suggestions i'm all ears!

HQA
HQA's picture
camera cooling

With most small-chip cameras and TEC cooling, you don't need 1.5hrs to cool the camera down.  The chip reaches operating temperature within a few minutes.  I'd say a half-hour is sufficient; experiment a bit.  Otherwise, your scheme sounds reasonable.  The trick with twilight flats is calculating the exposure time properly.  ACP has a built-in routine to do this, but typically, I usually pick the filter that can be imaged first (usually B or Ic, or if you are really a glutton for punishment, U), choose a good exposure time (like 5 seconds for SBIG/photometric shutter, or 10 seconds if iris shutter), and keep taking exposures without saving them.  When the typical ADU gets to about half well, start saving exposures, and increase the exposure time by about 5% per image (you'll figure out the appropriate increase for your setup).  Twilight takes some practise, which is one reason why you might use both dusk and dawn to get all of the images that you need.  Good luck!

Arne

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