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Post your Pixinsight Processing Flow!

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#176 Hawkdl2

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Posted 12 June 2020 - 02:49 PM

Chris,  Your workflows were very helpful for a mosaic I completed with data from last year, but I've only just started collecting DarkFlats to use instead of Bias frames for my ASI1600mm, and I am a  bit confused after trying to understand their application as described in your workflow.   If DarkFlats are essentially the same as a bias frame, as you point out, why do you then use them as a Master Dark in flat frame calibration, rather than as a Master Bias frame in ImageCalibration  (see your Figure 11). 

 

Larry



#177 cfosterstars

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Posted 14 June 2020 - 11:41 AM

Chris,  Your workflows were very helpful for a mosaic I completed with data from last year, but I've only just started collecting DarkFlats to use instead of Bias frames for my ASI1600mm, and I am a  bit confused after trying to understand their application as described in your workflow.   If DarkFlats are essentially the same as a bias frame, as you point out, why do you then use them as a Master Dark in flat frame calibration, rather than as a Master Bias frame in ImageCalibration  (see your Figure 11). 

 

Larry

This issue here is understanding what each of the types of calibration steps do. If you use a master bias on the lightframe, then you need to subract that from the flat and the dark frames or you will remove it twice. The thing is you only want to subtract the bias information from the light frames once. If you use the flatbark and calibrate the flat with it then you are removing both the small about of dark current (since its such a short exposure) and the bias offset since it also in the flatdark. So your master flat has both the dark and bias information removed when you divide the light by the flat. With a flat dark, you dont remove the bias from the dark, you just integrate them. You also dont scale the dark frame - they have to be the same exposure, temperature and gain as the lights. That why when you subract the dark from the light, you also remove not only the dark current, but also the bais. If you do this incorrectly, you can end up subracting the bias twice or dividing the light by the bias - both of which are a bad calibration. Does this make since to you?

 

HEre is another like from the deepskystacker website that has some flow charts:

 

http://deepskystacke...htm#Calibration

 

I think I will add something like this to my book.


Edited by cfosterstars, 14 June 2020 - 12:27 PM.


#178 Hawkdl2

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Posted 14 June 2020 - 03:20 PM

Chris,

 

Thanks for the explanation.  I might not have explained my questions well.  I have a pretty good understanding of calibration and calibration frames, at least I thought so.  Let me try again:

 

Until now, I removed bias signal from my flats with a Master Bias, but not from either Lights or Darks.  My Master Dark, therefore, contains bias and dark current, and therefore removes both from the Lights when the Master Dark is subtracted from the Lights.  As I understand it, that is the fairly common approach to calibration.  However, since my ASI1600 suffers from the odd bias frame issue I decided to try the FlatDarks approach, instead of using a Master Bias.  My uncertainty is over whether that FlatDark should be treated as a [modified] Master Bias or as a "short" Dark.  Since Bias frames technically do contain a small amount of dark current, albeit a very small amount, and dependent on the minimum exposure time of the camera, in my mind Biases, FlatDarks and Darks are essentially all the same - they all contain bias and varying amounts of dark current.  There are a number of lengthy threads on FlatDarks debating more or less that point, and making the argument that the amount of DC subtracted from Flats with a 0.1sec (or so) FlatDark would have no practical effect when that calibrated flat was subsequently divided into the Light frames, and therefore a FlatDark can be treated as a Bias.  If those points are true, then it seems that treating the FlatDark as a Bias makes sense and I can see why one would assume that the FlatDark should be added to PI's "ImageCalibration" for Flats as a Bias, and not as a Dark, though I'm not entirely certain it matters.  I can't find any thread where this point is raised, but noticed you add it as a dark. Hence the question in my earlier post - why as a Dark Rather than as a Bias?

 

Larry


Edited by Hawkdl2, 14 June 2020 - 03:25 PM.


#179 cfosterstars

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Posted 14 June 2020 - 05:52 PM

Chris,

 

Thanks for the explanation.  I might not have explained my questions well.  I have a pretty good understanding of calibration and calibration frames, at least I thought so.  Let me try again:

 

Until now, I removed bias signal from my flats with a Master Bias, but not from either Lights or Darks.  My Master Dark, therefore, contains bias and dark current, and therefore removes both from the Lights when the Master Dark is subtracted from the Lights.  As I understand it, that is the fairly common approach to calibration.  However, since my ASI1600 suffers from the odd bias frame issue I decided to try the FlatDarks approach, instead of using a Master Bias.  My uncertainty is over whether that FlatDark should be treated as a [modified] Master Bias or as a "short" Dark.  Since Bias frames technically do contain a small amount of dark current, albeit a very small amount, and dependent on the minimum exposure time of the camera, in my mind Biases, FlatDarks and Darks are essentially all the same - they all contain bias and varying amounts of dark current.  There are a number of lengthy threads on FlatDarks debating more or less that point, and making the argument that the amount of DC subtracted from Flats with a 0.1sec (or so) FlatDark would have no practical effect when that calibrated flat was subsequently divided into the Light frames, and therefore a FlatDark can be treated as a Bias.  If those points are true, then it seems that treating the FlatDark as a Bias makes sense and I can see why one would assume that the FlatDark should be added to PI's "ImageCalibration" for Flats as a Bias, and not as a Dark, though I'm not entirely certain it matters.  I can't find any thread where this point is raised, but noticed you add it as a dark. Hence the question in my earlier post - why as a Dark Rather than as a Bias?

 

Larry

THe MasterFlatDark is both a master Bias and short MasterDark. Did you look at the link? There are many way to calibrate the data that are mathematically equivalent. In the Image calibration the bias and the dark are subtracted from the LIght. SO the darkflat could go either place, but it depends on how you calibrate or not your darks or flats. The FlatDark is a dark and not a bias since it can be as long a 10 s vsl 0.001s or less for a true bias. IT is NOT really a bias and should not be treated as such. 



#180 cfosterstars

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Posted 11 July 2020 - 04:23 PM

I have received feed back that my images are too poor resolution. This was an effect of reducing the file size and compressing the images. I will go back to previous versions and try and replace the images with the originals, but this will take a lot of time. However, It will be worth it. I ami working a several wide field mosaics at the moment that I took with a Canon 135mm lens in both RGB and Ha/OIII/SII. I also have two galaxy sets from my SCT for M63 and M101 to finish. I am also about to receive my ASI6200MM-PRO full frame mono CMOS camera. If there  are any new things I find as I am completing these projects, I will add them to the book. Any other suggested topics, let me know.



#181 Linwood

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Posted 21 July 2020 - 07:49 AM

 

The book is now 297 pages with 384 illustrations and screen captures. I also include my basic process icon set.

 

THANK YOU!

 

I can't tell you how happy I am to stumble across this.  I think I must be the only person in the world who hates video tutorials, and still loves the written word. While there's great content in videos, people talk so darn slowly, and spend so much time on belaboring pointless stuff (I must have spent 2 minutes in one video while someone just dragged and dropped shortcuts around the screen to show it could be done). 

 

I have been trialing Astro Pixel Processor and wanted to try Pixinsight, and needed some kind of recipe book to get started.  I am just starting to look through it, but it's a BOOK and for that, many thanks!

 

PS. To all who make videos, I know there are some who love them, indeed who have trouble reading.   I mean no offense.  it's just that I am surprised how almost uniformly astrophotography tutorials are video vs written.  Maybe it's the Youtube ad money.



#182 MikeCMP

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Posted 21 July 2020 - 08:16 AM

I agree - I am using APP and Startools, but have been looking at this "book" to maybe trial PI. the written word to me is sop much easier - i can go at my pace, and go back easily. 

 

Really appreciate the effort that has gone into this. 

 

Mike


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#183 cfosterstars

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Posted 21 July 2020 - 11:25 AM

THANK YOU!

 

I can't tell you how happy I am to stumble across this.  I think I must be the only person in the world who hates video tutorials, and still loves the written word. While there's great content in videos, people talk so darn slowly, and spend so much time on belaboring pointless stuff (I must have spent 2 minutes in one video while someone just dragged and dropped shortcuts around the screen to show it could be done). 

 

I have been trialing Astro Pixel Processor and wanted to try Pixinsight, and needed some kind of recipe book to get started.  I am just starting to look through it, but it's a BOOK and for that, many thanks!

 

PS. To all who make videos, I know there are some who love them, indeed who have trouble reading.   I mean no offense.  it's just that I am surprised how almost uniformly astrophotography tutorials are video vs written.  Maybe it's the Youtube ad money.

 

 

I agree - I am using APP and Startools, but have been looking at this "book" to maybe trial PI. the written word to me is sop much easier - i can go at my pace, and go back easily. 

 

Really appreciate the effort that has gone into this. 

 

Mike

Thank you. I am also available to answer questions and help out. I am still working on this and adding new parts to it. Right now I am processing multiple mosaic images that is very time consuming. I actually have seven data sets to finish. I also just got a new ASI6200MM-PRO with Chroma 3nm filters for my SCT and will be adding anything new I learn with that camera. I have also been doing a lot of wide field with Canon lens and that is really fun.


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#184 Linwood

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Posted 21 July 2020 - 11:32 AM

I have also been doing a lot of wide field with Canon lens and that is really fun.

My most interesting attempts so far have been with a Sony camera lens and body, not anything specifically astro other than a mount.  I'm astounded what you can "see" as you pile up the exposures.  It's one area I struggle in figuring stuff out, as a lot of the info online assumes you are shooting with filters and separate color/lum exposures, though the OSC introduction made that better.

 

I'm going through a (probably not) final pass through APP, then going to try a trial of Pixinsight and work through your book, then probably loop back to DSS.  I need to PICK ONE and stop jumping around, but it's tough.



#185 cfosterstars

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Posted 21 July 2020 - 08:33 PM

My most interesting attempts so far have been with a Sony camera lens and body, not anything specifically astro other than a mount.  I'm astounded what you can "see" as you pile up the exposures.  It's one area I struggle in figuring stuff out, as a lot of the info online assumes you are shooting with filters and separate color/lum exposures, though the OSC introduction made that better.

 

I'm going through a (probably not) final pass through APP, then going to try a trial of Pixinsight and work through your book, then probably loop back to DSS.  I need to PICK ONE and stop jumping around, but it's tough.

I started with Images plus and photoshop. I made the plunge to PixInsight and have never looked back. I did this image with PI and a 50mm Canon Lens in Narrowband with a ASI1600MM-COOL camera:

OrionWF LSHO SMI

 

 

 


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