not reading fits data?

Main forum about Astroart
Post Reply
Forum_2015
Posts: 358
Joined: 07 Dec 2018, 15:04

not reading fits data?

Post by Forum_2015 »

I went to try preprocessing but immediately hit two real problems. Firstly, with my main camera it is advisable to not use darks for limited exposures (eg 5 - 10 minutes). However, this means wanting to use raws+bias frames. I often don't needs flats with the smaller scope. As far as I can see from the pre-processing screen, such options to use raw+bias are not possible. Does this mean multiple arithmetic subtractions on all raws?
Second problem:I took a series of dark/bias images for the guider with comparable filenames because the info is of course in the header. When I went to load the files into the pre-proc I realised that this wasn't possible without pre-examining each one......

Have I missed some other facility?

Lawrence

Forum_2015
Posts: 358
Joined: 07 Dec 2018, 15:04

Re: not reading fits data?

Post by Forum_2015 »

I guess you are using DSLR camera.
Then if you don't use darks or flats you don't need bias.
If you use flats then you need to use bias.

I don't understand your second problem.
Are you trying to stack images from your guide camera ?
Don't you have separate light files, dark files and bias files ?
Then you need just to put the light frames in the right place and dark files in the right place - don't need bias files.

Forum_2015
Posts: 358
Joined: 07 Dec 2018, 15:04

Re: not reading fits data?

Post by Forum_2015 »

Clarification: main camera SX M25c low noise=no darks. Hence raw+bias only. Smaller scope has good field=no flats. Hence question.
Guider=Lodestar. Series of darks+bias needed because of noise. However, because fits data includes bias/dark I do not write these in filename. AAv5 requires advance knowledge of each file - hence my question (why can it not get this info from the header?)
Lawrence

Forum_2015
Posts: 358
Joined: 07 Dec 2018, 15:04

Re: not reading fits data?

Post by Forum_2015 »

Hello,
1) Just put the bias frames into the box for dark frames.
2) The SBIG fits extensions are not supported, so you will need to name the sequence with a "human-readable" name, which will help you in the future to reuse the files.
Fabio.

Forum_2015
Posts: 358
Joined: 07 Dec 2018, 15:04

Re: not reading fits data?

Post by Forum_2015 »

Thanks. BTW SBIG is not relevant here. These are Starlight Xpress cameras and FITS is the astronomical standard.....

Lawrence

Forum_2015
Posts: 358
Joined: 07 Dec 2018, 15:04

Re: not reading fits data?

Post by Forum_2015 »

In the FITS standard there are no Keys to indicate if an image is a flat, bias or a dark.

http://fits.gsfc.nasa.gov/fits_documentation.html

A program which writes them is out of the standard.

Forum_2015
Posts: 358
Joined: 07 Dec 2018, 15:04

Re: not reading fits data?

Post by Forum_2015 »

OK, I follow that. In my other program this data is set in the exposure plan and appends the info within the header (as light/flat/dar/bias).

Post Reply