Image Calibration Tutorials

[DaveLeeNC]

New user diving into PixIS mostly through 'Harry's Tutorials". After a basic understanding of registration, stacking, and Histogram/Screen transformations, the next obvious step is Image Calibration (application of darks and flat frames).

I see the IC Process, but surprisingly I don't see any tutorial from Harry's site or the PixIS site on IC and (per PixIS) the IC tool has no documentation. What is the best way to start here? While I understand the concepts involved, I don't understand how PixIS manages calibration frames whose parameters (ISO, time, temp, etc) don't match the applicable light frames.

How do I start here? Thanks.

dave

[pfile]

the BatchPreProcessing script can handle all of this for you.

as for matching ISO, you are correct, for bias and darks the ISO should match the lights. for flats the ISO does not have to match the lights, however, the flats must be calibrated with matching bias frames at the least. to be clear i'm not sure if BPP can do this (handle 2 sets of bias frames with different ISO)

the temperature of your darks should match the lights for best results.

just about the only place where it's 'okay' for there to be a mismatch is in the duration of the darks. dark current scales linearly with time, so it's possible to do this:

light - bias - ((dark - bias) * tlight/tdark)

and get a properly calibrated frame.

when you turn on dark optimization in IC this is what happens, except that PI does not scale the darks using exposure time. it scales the dark until the noise in the calibrated frame is minimized.

[DaveLeeNC]

Thanks for the quick response.

I vaguely recall reading somewhere that the Batch script for pre-processing doesn't work without flats. Is that right? I'm just in learning mode right now and don't have any flats (I'm not currently concerned with the fact that this means that I won't have anywhere close to optimum results - but that isn't the point right now.

dave

[DaveLeeNC]

Just stumbled into this (it wasn't obvious to me on Harry's site, but maybe I just missed it).

http://tinyurl.com/ov4yb5k

Note that it is a tutorial on the batch pre-processing script, rather than a tutorial on 'raw calibration'.

dave

[Josh Lake]

Batch Preprocessing should work fine without flats, I do it all the time!

[astropixel]

http://pixinsight.com/tutorials/master-frames/en.html is this what you are looking for, David? It is the official calibration tutorial. The BatchPreprocessing script will do everything you need. As I recall it needs at least bias or dark frames - min 3.

[DaveLeeNC]

AP, that would appear to be what I was expecting. I thought that I had looked at this and it was something else. My error. Thanks.

dave

[troypiggo]

In the PI docs there is an excellent article on ImageIntegration that helps understand what's going on too:
http://pixinsight.com/doc/tools/ImageIntegration/ImageIntegration.html

[DaveLeeNC]

Troy - thanks.

dave

[jerryyyyy]

If you are collecting tutorials, this is a nice soup to nuts overview by a person in Silkicon Valley.  Very understandable. 

http://www.lyric.com/astro/intro-to-astro-image-processing-talk/assets/fallback/index.html