BatchPreprocessing in PixInsight: combining different imaging sessions

[oymd]

Evening everyone

A few days ago I started a thread about my struggles with combining data from different imaging sessions using a OSC.

What made my issue worse was that the two sessions had different orientation, and DSS could not manage to produce a stacked image using groups. It was a mess.

 

 

Was advised to try PixInsight's BPP, so read the book chapter  and did some research on the net. WBPP is new, and not mentioned in the book.

I thought I would write this guide, just in case there are other newbies like me looking for a solution, and might find this helpful.

I  stumbled upon a few tutorials which explain exactly that, especially with DARK FLATS in case of CMOS OSCs.

I was initially told to add the Dark Flat files along with the Flats, and PI will process them in BPP. This turned out to be wrong.

Was also told that Dark Flats can go into the BIAS group, but this is also wrong.

 

Here's what needs to be done (according to my research, and what worked for me)

 

BPP needs to be done separately for each imaging session.

ie:

Imaging session day 1:

in BPP:

1-Darks & Dark Flats go into the Darks group. BPP will separate them according to exposure time, and match the Flats with the Dark FLats as they share the exposure.

2-Flats go into the Flats group.

3-Lights into the Lights group

4-With OSC, tick CFA so as FITs get debayered, Do not tick "Optimise darks", and in FLATS, DO NOT tick "Calibrate with dark flats only". This last setting is for when BIAS files are used.

5-For the registration file, choose ANY of the lights, preferably a good one. Blink can help with that (I did not use it).

6-Choose output folder and RUN BPP.

You will be left with FOUR FOLDERS:

calibrated, logs, master & registered.

The registered files will have c_d_r in case of OSC, or c_r in case of mono. (d for debayered)

DO NOT DELETE THE REGISTERED files, you will need them to produce the final image.

In the Registered folder, pick a registered sub, and copy it to a NEW FOLDER, and name it something like "Original Registered Light"

This will be the registered sub to use in every subsequent BPP for the next sessions

 

Imaging session day 2:

in BPP:

Repeat steps 1-4 for the new subs, assuming:

a- you took new flats and dark flats, as you might have removed the camera after the first session.

b- assuming you have a Dark library matching exposure and temperature of your Light subs

Here is the important part:

For the registration file, the file you saved separately from the first imaging session, the one we called : "Original Registered Light"

Choose output folder and RUN BPP.

You will be left with FOUR FOLDERS:

calibrated, logs, master & registered.

 

Imaging session 3 and so...repeat as you wish, but ALWAYS use the INITIAL REGISTERED FILE that you saved as the REFERENCE file.

Finally, to produce your COMBINED MASTER LIGHT:

Use ImageIntegration, and combine ALL files in ALL the REGISTERED folders from all the sessions.

Remember to SAVE the final image, as it is not automatically saved.

Hope this can be of help to all the newbies out there. I worked very well for me.

Here's the combined M63 that I took. It's not anything to write home about, but I'm very proud of the work that went into it!! My image processing is a different story.!!

Best regards

Ossi

 

[wimvb]

Nice write up. You may find this link useful. 

 

[oymd]

28 minutes ago, wimvb said:

Nice write up. You may find this link useful. 

 

Thanks Wim!

[MarkAR]

Well done, glad you finally sorted out all the confusion.

[Marmo720]

Hi @oymd - just wanted to say thank you for this write up. I was able to align subs taken from different telescopes and cameras and process them after. Couldn't find out how to do this with any other software and PI was confusing to follow. So your guide was really helpful! 

[oymd]

On 16/11/2020 at 16:30, Marmo720 said:

Hi @oymd - just wanted to say thank you for this write up. I was able to align subs taken from different telescopes and cameras and process them after. Couldn't find out how to do this with any other software and PI was confusing to follow. So your guide was really helpful! 

Apologies, I missed your post and just saw this!

You're more than welcome! I'm happy the guide helped you!