Date: Thu, 30 Mar 2006 19:11:04 -0600
From: "Brad Walter" <bwalter
	k2V1B6Bt019357
Cc: 

 
With regard to #3, I have found that it is wise to take flats before and
after the zenith flip, particularly if you are still using a camera
connected with a (stiff) parallel cable. It is very easy to get some
camera rotation during the flip. If you haven't taken flats beforehand
and the camera rotates, you can't get accurate measurements from the
runs, I consistently noticed a significant light curve discontinuity
that occurred right at the flip . When I started taking flat sets for
each side of the flip, the discontinuity disappeared. It is very
discouraging to see hours of data and hours of analysis wasted for lack
of 15 minutes worth of flats that I could easily have taken if I had
thought a little more about how Mr. Murphy's law could manifest itself
yet again.
Koppelman
Sent: Thursday, March 30, 2006 2:43 PM
Cc: chris
(MentoringRequired)

Since we are discussing the basics let me throw in a couple quick rules
of thumb.

1. Take a lot of bias frames. This is essentially a dark frame at zero
time. You may not need these but you'll be glad you have them if you do.

2. Take a lot of dark frames. If you scale darks, you just need them at
your longest exposure (or longer). If you don't scale you need to take
darks for every exposure length from the night. I've found you can get
away with less darks if they are longer. For example, for 180 second
darks between 5 and 16 is plenty. For 10 sec darks, go ahead and take
25+.

3. Take flat fields in each color. Do this at the end of the night after
flat screen or a light box or the clouds or the twilight/ dawn sky for
your flats. Do more than one method if you have time and divide one by
the other and notice differences.

4. Take more than one (read: many) exposures of each object. If you do
this you gain a lot of benefits such as eliminating cosmic rays, being
able to average the observations, being able to calculate the deviation
of the standard stars, etc.

The two (2) golden rules for me are:

1. Take your time: this is science. Be careful, thoughtful and precise.
2. Have fun! This is for your personal growth. The data points are a
side benefit.

This is not the gospel according to Michael by any means, just some
brief thoughts on what has worked for me.

Michael
http://www.lolife.com/astronomy/


On Mar 30, 2006, at 2:10 PM, BailyHill

> We rely on the commercial tools.   Ones that are most popular are  
> Maxim,
> AIP4Win, IRAF and Mira.

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