I disagree to Bob Freeze's statement below:
> Don't worry about the 'flat'
> unless you are doing photometry.

If you have ever observed the Moon or a planet through a telescope with a
attached surveillance camera you could have noticed if the object moves, how
strong the dark spots which don't move on the screen, are. This are tiniest
particles of dust on the CCD chip, protection window or filter.
A flat field is divided from the image with a formula where the brightest
pixel's are 1 and all dimmer less than 1. Example: After the calculation te
pixel with a dust spot which had the value 0.5 will brighten the value of
the star on real image by 2.
Vignetting is also corrected the same way as are density errors of filters.
It doesn't matter which telescope or CCD camera you use.
Use the 'vital' flat fields!
Nevertheless if you use a Meade field derotator (I vever liked them anyway)
a flat will bring you more errors than good. You would need to turn the
whole telescope to use 'flats'.

Renato

View index by [date] [author] [subject]
Previous message: [M]: Re: Re: OT: Pentax K1000 and Astrophotography -Reply, Philip Freeman
Next message: RE: [M]: RE: Magellan II - LX50 Questions, David W. Bonnell
Previous message in thread: [M]: Re: Meade 416xt and Dark Frames, Bob Freeze