Guide to Preprocessing of Raw Data with PixInsight

bulrichl

PTeam Member
Nov 2, 2016
1,444
226
La Palma, Canary Islands
The current version of my guide is a PDF file which is appended, because the text size grew beyond the allowed limit in this forum.

This is the structure of the text:

1. Setup and Properties of Digital Cameras used for Astrophotography
2. File Formats for Image Acquisition, Camera Driver, Image Acquisition Software, Gain and Offset
3. Why Do We Perform Image Calibration?
4. Types of Calibration Frames
5. Settings and Conditions for Image Acquisition of Calibration Frames
6. Generation of Master Calibration Files
7. Light Frame Calibration with PixInsight's ImageCalibration Process
8. Inspection and Judgement of the Calibration Result
9. Post-Calibration Preprocessing Steps
10. Automation of Preprocessing: WeightedBatchPreprocessing (WBPP) Script

Bernd
 

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russp

Member
Mar 13, 2014
15
0
Great guide - very useful, can I ask what debayer pattern you're using for your ASI294 ? I've been using RGGB but I'm not entirely sure it's correct as it's giving me really noisy blotchy backgrounds even after DBE.
 

lage

Active member
Mar 24, 2017
27
0
Very informative and helpful, thanks.
I have one question though, that I haven't found the answer to;
I only use DSLR's for my astrophotography. Shooting lights and darks under the same circumstances is understandable, but how about flats and biases? Can you have one set of these for all your lights and darks, or do you need different sets for different ambient temperatures, ISO settings etc?

Best regards,
Lage
 

sn2006gy

Well-known member
Jun 10, 2020
53
20
I have one question though, that I haven't found the answer to;
I only use DSLR's for my astrophotography. Shooting lights and darks under the same circumstances is understandable, but how about flats and biases? Can you have one set of these for all your lights and darks, or do you need different sets for different ambient temperatures, ISO settings etc?
Many people create a master bias and use that (or a super bias as it's called) and it can be done at any time and any temperature. Typically, I do flats using nina flat wizard at the end of observing (using sky flats during morning hours). Nina will calibrate the flats to optimum exposure. Goes so quick I haven't tried to do master flats and save them. Plus, I move my telescope around a lot so dust won't necessarily always stay in same place long enough for masterflats sets to remove motes reliably.
 

sn2006gy

Well-known member
Jun 10, 2020
53
20
What are people doing with their ASI533? There is no real ampglow to speak of. I've seen a lot of discussions of people not using darks and some even dropping bias if they have good dark flats, flats and lights. I'd love a similar capable monochrome to the 533... would simplify processing.
 

umasscrew39

Well-known member
May 4, 2019
154
65
Orlando, FL
www.astrobin.com
For the ASI533MC (and its big brother, ASI2600MC), I've have had great success with darks, dark flats, flats but no bias. I now use WBPP with minimal PP. I started out just testing it with no flats and darks and the images were truly amazing, due to low noise and no amp glow, especially considering nothing was done with the lights. Of course, if your optics are dirty, the image will look nasty. So, not a good practice.
 
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JPetruzzi

Well-known member
Jun 18, 2020
68
49
I did some tests w/my 533, tried it with just darks, no dark optimization, no bias, then calibrated the same frames in the standard PI workflow, i.e. bias, and calibrated and optimized darks. Resulting frames were nearly indistinguishable. Pretty sure the sensor is so good it won't matter what route you take. :)
 

umasscrew39

Well-known member
May 4, 2019
154
65
Orlando, FL
www.astrobin.com
Let's just say, compared to when I used SX CCD cameras, which are very good, the 533 and 2600 CMOS are very forgiving cameras. They make the hobby much more enjoyable, in my opinion. Especially so, when you do not (like me) have a lot of clear nights to experiment and keep tweaking things.
 
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JPetruzzi

Well-known member
Jun 18, 2020
68
49
Let's just say, compared to when I used SX CCD cameras, which are very good, the 533 and 2600 CMOS are very forgiving cameras. They make the hobby much more enjoyable, in my opinion. Especially so, when you do not (like me) have a lot of clear nights to experiment and keep tweaking things.
Glad to hear it--my ASI533MC-Pro is my first cooled camera, looks like I started with a good one. :)
 
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sn2006gy

Well-known member
Jun 10, 2020
53
20
Been happily just processing with Flats, Flat darks and Lights using WBPP. Super simple. Love this camera!
 

Fegato

New member
Sep 11, 2020
2
0
Thanks for this. As an ASI294MC Pro owner, this really helps pull a lot of things together. Hopefully I can improve my calibration results now - have already removed the amp glow which wasn't completely, and look forward to some clear nights to see how everything else goes!
 

Gerard Ford

New member
Nov 13, 2020
1
0
This article is exactly what I was looking for. In clear language, it described the WBPP processes with supporting information. Often we hear-read of how complicated Pixinsight is to learn. I've struggled with Photoshop for years, obtaining inconsistent results and not understanding why. I simply do not "get" Photoshop. In comparison, Pixinsight (although challenging) makes sense to me. My challenge over the past few months (through much reading and video watching) has been to understand the basic, sequential steps for processing OSC CMOS pictures. Your article has put a lot of my mis-understanding in context and scope.

Thank you much for this! Now on to learning post processing!

- Jerry
 

BenKolt

Member
Feb 9, 2014
14
0
I'm late finding this document. It's a very nice, thorough write-up, Bernd! Thank you for posting it.

Ben
 

mjpost1

Member
Oct 30, 2017
6
1
Very useful guide - thanks!

But I tried using Local Normalization files in ImageIntegration and cannot. You say to load the .xnml files created by LN into ImageIntegration together with the aligned files via the Add Files button. I can load the aligned files just fine. But when I navigate to the folder where the .xnml files exist, PI sees no loadable files and does not recognize the .xnml extension. How can I load the .xnml files into ImageIntegration? I checked the forum and found nothing useful.
 

pfile

PTeam Member
Nov 23, 2009
7,748
477
did you click the "Add L. Norm Files" button in ImageIntegration? you need to use that button so that II recognizes the extension.