light dark flat frames

[Carl]

Hi folks
having a go at stacking with Deep sky stacker.
So far looks pretty easy to use with auto register and stack. But what are light, dark and flat frames. and how to I take them with a dslr?
Regards Carl

[Striker]

Hi Carl.

I will be brief.

Lights= your exposures of the target you are imaging
Darks= Same length exposure as your lights but with the cap on
Bias= is the shortest possible exposure you can take with the cap on probably 1/4000-1/8000 of a sec
Flats= are the hardest technicaly where you take an image of all your inperections of the scope...this needs to be gone throw in depth and there is many methods to do so..it is also the most important part of calibration followed closely by Darks then Bias.

[Dennis]

What Striker said, as well as:

Temperature: Make sure the light frames (e.g. your galaxy images) are taken at the same temperature as your dark frames (your image with the scope cap on).

Flats: Ideally, if you were to take an image of a perfectly smooth, white wall, you should get a nice, white, evenly exposed rectangle on your computer screen. But you won’t! You’ll probably see:


Vignetting; where the flat field is brighter in the centre and tends to fall off in brightness towards the edges.
Gradients; where there may be a small but gradual non-even illumination across the frame.
Blotches; which are dust specks on the optical surfaces near the ccd chip that get magnified into blurry doughnuts.
Any other imperfections in the optical train, such as finger prints, hairs, etc.

Using the software, you can more or less eliminate all these "problems" and end up with a nice looking final image.

Cheers

Dennis

[jase]

Tony and Dennis have things well covered, but I thought I'd also point you to the IIS article by Eddie Trimarchi - http://www.iceinspace.com.au/index.php?id=63,211,0,0,1,0

Another excellent resource for beginners - http://starizona.com/acb/ccd/ccd.aspx

Enjoy:thumbsup: