When to debayer?

[Diane Miller]

That's the frustrating (and, really, inexcusable) thing about PI -- how does someone get the right information?  I can respect the difficulties that it is an evolving piece of code, and that people are trying to help with tutorials that are more accessible than "official documentation" but it would be nice to have more officially vetted and up-to-date information.  It should be easily accessible from a sticky at the top of this General section.

I've been trying to put together a workflow from about 6 different sources, most of whom use CCD cameras and have legitimately different workflows than for a SLR.

I could just do the BPP and hope for the best -- ignoring the dire-sounding warning.  But here's the quandary:

Is my data good enough that I should go to the extra trouble of doing things with the most control I can, or is it bad enough that it doesn't matter and I should quit worrying. 

Well, no, the real quandary is:  How do I know?

[pfile]

well with respect to BPP, the warning is meant to convey the notion that you need to fine tune the integration settings beyond how ImageIntegration is set up by BPP. I do agree that the warning is worded in such a way as to cause unnecessary "panic". the rest of the BPP flow (making masters, calibration, CC) is pretty much the same as you would do it by hand. so you're not giving up anything by using BPP...

rob

[Diane Miller]

OK -- so back to pendulum at 0.  How do I know how to fine-tune the integration settings?  And can I do it within the BPP dialogs ?  Or do I just use it for calibrate only?

Sorry for sounding like a broken record... and thanks for the patience.

[pfile]

that's OK.

i can't remember if you can fine-tune ImageIntegration settings in BPP (i don't actually use it.) there are probably tutorials out there regarding this, but essentially what you're trying to do is optimize the pixel rejection parameters so that you're rejecting the right amount of pixels from the stack. pretty much the only way this can be done is to examine the rejection maps that come out of ImageIntegration and fiddle with the sigma low/high sliders (assuming you are using a sigma-based rejection method, which you should if you have enough subexposures.) if the rejection maps show nothing, you're not rejecting anything and that's bad. if the rejection maps show a hint of the structure of what you're stacking, you're rejecting too many pixels. also, i've noticed that sometimes i'll have a couple of bad frames in there with really high backgrounds which seems to have fooled the normalization, and this is the cause of too many pixels being rejected. for my camera and projects i find that the proper settings for the sigma high and low are around 3. you can try using that as a starting point and see what you see.

anyway after BPP has done it's thing, it will have left _c_cc_d_r files laying around somewhere in a subdirectory of the output directory you chose. you simply need to open the ImageIntegration process and load those files, then start messing with the rejection parameters. all of the rest of the ImageIntegration settings are correct for Light integration by default, so you don't need to mess with those.

the "true purpose" of the BPP script is to handle the drudge work of calibrating all the lights from all your different filters when using a mono camera. as you can imagine, it gets kind of old repeatedly creating flat masters for 4 or 5 filters, then running ImageCalibration 4 or 5 times each with a different flat master, etc. so yeah, essentially it's purpose is to calibrate your files. obviously when using an OSC there are a lot fewer steps, but still enough to warrant letting a script handle the calibration.

rob

[Geoff]

OK -- so back to pendulum at 0.  How do I know how to fine-tune the integration settings?  And can I do it within the BPP dialogs ?  Or do I just use it for calibrate only?

Sorry for sounding like a broken record... and thanks for the patience.

You can't fine tune integration settings with BPP. The integration is just there to give you a reasonable preview of the integrated images--just to check that everything is OK. Once you have the registered images you can move onto integration. Have a look here for a tutorial on this http://www.astrosurf.com/jordigallego/articles.html
Look for the article headed "Image integration techniques...."
Geoff

[Diane Miller]

OK -- thanks!  A few more pieces falling into place. 

a) brew more coffee
b) settle down for some reading and note-adjusting

With my modest camera, I'm happy to run things the hard way.  I don't even want to think about the work involved with a ccd camera and 4-5 filters.  But the images are drop-dead gorgeous!