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PixInsight => General => Topic started by: alanrock on 2018 August 15 20:13:22

Title: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 15 20:13:22
I've got an image which seems to resist all my attempts with DBE to get an even background. I am pretty new to PI and am wondering if I could get some help with this. The image was taken with a ZWI OSC camera and I have applied flats, darks, and bias frames. The lights are 600 seconds ea and there were 14 of them. It's an RGGB camera, and the image has an obvious green color cast to it, but that's rather easy to remove, however, after running it through DBE or ABE, the resulting image is very splotchy and I cannot seem to flatten out the background. Any tips would be appreciated.
Title: Re: Splotchy background after DBE
Post by: pfile on 2018 August 15 20:18:10
you'll have to upload the xisf to google drive or similar and post a link here, the only way to give advice is to work the image...

rob
Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 15 20:20:55
Is there someplace where I can upload the image, or do I need to share it some other way?

https://drive.google.com/file/d/1ds08Rk-6CszPcTOVoKNjBAWf-9gWm0k3/view?usp=sharing
Title: Re: Splotchy background after DBE
Post by: pfile on 2018 August 15 21:33:34
part of the problem here is that you seem to have skipped the debayering step - you need to check "CFA images" in the BPP interface.

rob
Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 16 04:03:42
I have not skipped that step—it’s been debayered.
Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 16 06:44:50
Here's what the image looks like after a dynamic crop to clean up the edges and one pass of ABE.
Title: Re: Splotchy background after DBE
Post by: pfile on 2018 August 16 08:32:38
someone else has to check me then - there's something wrong here; the image has a screen-door look which is characteristic of some kind of debayering problem.

rob
Title: Re: Splotchy background after DBE
Post by: msmythers on 2018 August 16 11:27:55
rob

I've got the same thing as you. It looks like a debayer problem. I zoomed in 3:1 on the original and channel separated images and they all show the same thing which was expected. I also opened 2 of my own integrations with no other processing and the same zoom level. No screen-door. I tried a number of different debayering parameters on my own raw images and could not replicate the screen-door effect.

Could this be a split cfa type issue or drizzle cfa maybe? Another thought was all calibration and integration done in PI? Just throwing question out there.


Mike
Title: Re: Splotchy background after DBE
Post by: sharkmelley on 2018 August 16 11:43:08
It's definitely using the wrong debayer mask for the files you have, that's why you seeing that blocky effect.  What format are your original files?  For instance with FITS there is always the confusion about whether or not the acquisition software saves them as "bottom-up" or not.  The "Up-bottom FITS" flag in the BatchPreprocessingScript can take care of that.  If you are not using BatchPreprocessing then try different combinations of debayer mask - I suggest GBRG first of all (the up-bottomed version of RGGB), then maybe GRBG, then perhaps BGGR.

Mark
Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 16 13:49:29
Well, the camera reports it’s RGGB, so that should be correct. I’m not seeing the screen door effect that you folks are seeing. Do you see the splotchy effect I’m talking about? Some areas in the image have a red/pink tint to them.
Title: Re: Splotchy background after DBE
Post by: sharkmelley on 2018 August 16 14:07:33
Quote from: alanrock
Well, the camera reports it’s RGGB, so that should be correct. I’m not seeing the screen door effect that you folks are seeing. Do you see the splotchy effect I’m talking about? Some areas in the image have a red/pink tint to them.

Yes the camera might report it is RGGB but this only works if the acquisition software has not flipped the raw data before saving it into the file.  FITS, for instance, is notorious for being flipped by some software.

What acquisition software are you using and what file format does it use?

To see the screen door effect perform a ChannelExtraction then do a ScreenTransferFunction on each channel - view them at a scale of 2:1 or more to make it more visually obvious.

Until you debayer correctly then the colours will be incorrect.  This is the problem that needs to be fixed before anything else.

Mark


Title: Re: Splotchy background after DBE
Post by: srecaldin on 2018 August 16 15:22:10
The debayer pattern for zwo cameras, I think is GRBG.
Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 16 18:14:02
I'm using Sequence Generator Pro and it's producing FITS files.
Title: Re: Splotchy background after DBE
Post by: bulrichl on 2018 August 17 01:57:34
According to the pixel resolution (w=5496 h=3672) the camera seems to be a ASI183MC. The bayer pattern for this camera model is RGGB ( https://astronomy-imaging-camera.com/product/asi183mc-pro-color , Tab 'Specification').

I guess Mark is perfectly right: if the image is flipped vertically for some reason, the bayer pattern changes from RGGB to GBRG:

Code: [Select]
R G        G B
      ->
G B        R G

SGP was used for image acquisition(FITS files). So the correct setting in PixInsight would be 'Coordinate origin': 'Upper left corner (up-bottom)'. This has to be set in FITS format preferences (Format Explorer/FITS) and in BatchPreprocessing, if used.

Bernd

Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 17 06:10:20
I’ve used the up-bottom choice in Batchpreprocessing (I already was, that is). When I turned it off and left the debayering at RGGB, I got a very BLUE image, and the darks didn’t do their thing, so that wasn’t a good choice. I also switched it to GRGB and got the same as my original result. No luck here.
Title: Re: Splotchy background after DBE
Post by: sharkmelley on 2018 August 17 07:06:08
Quote from: alanrock
I’ve used the up-bottom choice in Batchpreprocessing (I already was, that is). When I turned it off and left the debayering at RGGB, I got a very BLUE image, and the darks didn’t do their thing, so that wasn’t a good choice. I also switched it to GRGB and got the same as my original result. No luck here.

I think we need to take a look at your FITS files.  If you use Google Drive to upload one each of the light, dark, flat and bias files then I'm sure we can work out the correct settings.

Mark
Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 19 18:39:15
Here you go--thanks in advance!
https://drive.google.com/open?id=15wKi7OebRUzOuz-_5utSH3yHyFzlEWbL
Title: Re: Splotchy background after DBE
Post by: msmythers on 2018 August 19 20:24:20
Just wanted to take a look at the frame 8 light sub for screen door effect. All I did was debayer(RGGB,VNG), ABE,PCC,HT and curves with mask. I didn't try hard with ABE since this was just a single frame without calibration as the amp glow on the right shows. Colors look fine and no screen door effect.

I'll let others talk to the calibration.



Mike
Title: Re: Splotchy background after DBE
Post by: pfile on 2018 August 19 21:16:30
same flow here, RGGB/superpixel + up-bottom, no problem debayering; no screen door, color seems correct. maybe there is a problem with the calibration?

rob
Title: Re: Splotchy background after DBE
Post by: alanrock on 2018 August 20 06:47:10
OK, so maybe we should talk about my settings in Batch Preprocessing. Do I need to use the same rejection algorithm for Darks, lights, Bias and flats, or does it depend on the number of files for each? I'm using Winsorized Sigma Clipping for everything although I do not have the same number of files for everything (obviously). Also, I am using Sigma High and Sigma Low of 3.0 for everything but lights--that was different. Any other settings I should be looking at for things to adjust? Would it be helpful to share a log file?
Thanks again, hopefully we can figure this out!
Here's the log file: https://drive.google.com/open?id=1vjlNwSsflnRfZuQaD1tXZ3HIfAKS2Csp
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 20 09:12:40
i guess what would be instructive is if you posted one of the _c_d and _c_d_r files from the batch preprocessing folder, that would show whether or not BPP did the right thing along the calibration and registration steps.

as long as you have enough frames (~10 - ~15) windsorised sigma clipping should be OK for all frames. 3.0 is pretty reasonable for Hi/Lo sigma. if you open the masters that BPP creates i think it will show the rejection maps and you can see if too much was rejected (or not enough)

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 12:48:32
I uploaded a c_d and a c_d_r file into the shared folder. Interestingly, when I open the c_d_r file and do an ABE on it, it does NOT look splotchy all. What do you think that means?
The files are in this folder: https://drive.google.com/open?id=15wKi7OebRUzOuz-_5utSH3yHyFzlEWbL
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 20 14:27:25
well so the _c_d and _c_d_r files you posted appear to be undebayered. although of course they should be, or at least the script thinks it attempted to debayer them or else it would not give the suffix "_d".

one thing that strikes me as odd is that the amp glow in the dark file appears on the left side of the frame, while it appears on the right in the light frame. this could indicate some incompatibility between the calibration frames and the lights with respect to how they were written out to disk (up-bottom vs. bottom-up). the filenames for the flats/bias/dark look like they were generated by Maxim to me. if so, that's likely your problem right there - maxim is writing out the fits files differently than SGP and so they are not compatible with one another (though i suspect with some massaging you could make them compatible.) so it could be that the files are debayered, but because the bayer matricies are reversed between the calibration frames and lights, the debayered data is coming out looking weird. in particular i can see that in the flat that the green channel is much weaker than the other two channels, which might end up leaving a checkered imprint even on the debayered data.

anyway one way to test this theory is to debayer, align and integrate the lights without calibrating them and see what you get. i suspect it will work fine and you'll need to recapture your calibration frames.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 14:49:33
When I look at the c_d_r file though, it's quite green which would seem to indicate it's been debayered, wouldn't it?
I'll have to look at my calibration files again though. I could've sworn they're all created in SGP, but when I look at the FITS header, it says Maxim for some of them. I probably shouldn't mix and match them.
And, if the c_d_r file looks fine (not splotchy), wouldn't that seem to indicate that it's the step after that that's the problem? And the step after that is...?
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 20 15:03:16
c_d_r (and c_d) are indeed green but the tell is the checkerboard pattern when you zoom in... that's not normal. ordinarily this is what an undebayered file looks like but in this case i think it's because the dark (and more importantly the flat) bayer pattern is reversed from the lights when read in to PI.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 20 15:12:39
well now i'm pretty confused - for fun i used your flat/dark/bias subs to calibrate the light sub you posted and it's coming out "fine" in the sense that the debayered file looks proper, with no screen door effect. so either your calibration masters are really different from the subs you posted, or my theory about the flat is wrong.

if you can manually calibrate and debayer the images OK with the 3 masters indicated in the log, then all i can guess is that for some reason, the BPP script has failed to debayer the images, despite calculating a filename that indicates it was debayered. i have never seen that before though.

but for sure the dark sub you posted does not match properly since the amp glow does not match.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 15:15:17
I just started to run the BPP again using the darks that were created in SGP, even though the only flats I have were created in Maxim, and I noticed that the last time I ran it I had the debayer set to BGGR, probably because I've tried so many different things. Ugh. Anyway, I'm running it again right now even though the flats are from Maxim. When it's done, I'll repost those files.
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: sharkmelley on 2018 August 20 15:27:05
Quote from: alanrock
I uploaded a c_d and a c_d_r file into the shared folder. Interestingly, when I open the c_d_r file and do an ABE on it, it does NOT look splotchy all. What do you think that means?
The files are in this folder: https://drive.google.com/open?id=15wKi7OebRUzOuz-_5utSH3yHyFzlEWbL

On the contrary, your a c_d and a c_d_r files DO have that same grid pattern.  Look at them at a scale of 4:1 (not 1:4) and you'll see the pattern.  For the avoidance of doubt, I'm looking at the files ngc7320_600sec_1x1__frame14_c_d.xisf and ngc7320_600sec_1x1__frame14_c_d_r.xisf.

However, your light file (ngc7320_600sec_1x1__frame8 copy.fit) and flat file (Flats-0015F1 copy.fit) provide the key to this mystery.  These two files are not compatible i.e. they have not been created with the same settings.  The CFA pattern RGGB works fine with the light frame but not with the flat frame.  The flat frame seems to need GBRG or GRBG.  The problem is that when you calibrate the light frame with the incompatible flat frame you end up with a mess that no single CFA pattern can possibly debayer successfully - you will always have a grid pattern.

In addition, if you examine the dark frame the "starburst" amp glow is on the left hand side but in the light frame it is on the right hand side.  So the dark frame is also definitely incompatible with the light frame.  With the bias frame it is impossible to tell.

You need to re-examine your acquisition of light frames and calibration frames to determine what has caused this left/right flip.  Were these files all shot at the same time with the same software?  Did you change some settings somewhere?

Mark
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 15:53:39
So it sounds like I need to resolve this screen door effect before I need to even bother caring about the splotchy effect I was talking about in the beginning, is this right? As previously stated, my flats were created with Maxim, but my bias, darks, and lights were created in SGP. When conditions permit, I'll redo my flats in SGP (I'm using a Hyperstar on a C9.25, so I cannot just create flats any time I want to-conditions need to be right). When I zoom in on a light, I see a checkerboard effect which I assume is normal, but when I zoom in on a c_d_r file, I guess I'm seeing the screen door effect. Check out the attached files. I guess I shouldn't bother wasting my time until I get new flats done, does that sound right?
And to reiterate, the screen door effect and the "splotchy" overall look are two different issues, although they may be related.
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 15:54:51
Screen?
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 20 16:08:46
here is what i see. the top left is the raw light you posted, uncalibrated. the top right is debayered using RGGB and viewed under STF with channels unlocked. below that is the _c_d file you posted viewed under STF with channels unlocked. with channels locked it would look green. the _c_d file should look like the top right file, but for some reason it does not.

i believe that the splotchyness is a byproduct of this problem and it needs to get solved before worrying about anything else.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: sharkmelley on 2018 August 20 16:23:46
Quote from: alanrock
my bias, darks, and lights were created in SGP.

Are you sure?
If so, why does the dark frame have the "starburst" amp glow on the left hand side but in the light frame it is on the right hand side?  What I'm saying is that your example dark is incompatible with your example light even though you say both were created in SGP.

Your example flat is also incompatible with your example light.

This is why we are seeing that grid/chequerboard/screen door problem from the calibrated files, once they are debayered.  It is not normal to see this pattern in a debayered file.

Mark
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 19:01:23
Let me clarify. The images I just posted (checkerboard and screen) were captured from pix produced while using darks, bias and lights created with SGP and flats created with Maxim, although the files I had posted earlier used darks which were created with Maxim. Also, the darks I used this last time were 300 sec @ -10º instead of 300 sec at -15º (because as I went through my darks, I saw that these were the ones I had created with SGP)--I just wanted to see if that helped, but I'm guessing that until I get flats created with SGP I'm going to have this same problem. Make sense?
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 20 19:13:59
i think so. but what happens if you just run without flats? if the debayered files look OK (like my 2nd image in the screenshot) then you'll know it's the flats that are causing the problem for sure.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 19:15:04
Will BPP run without the flats?
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 20 20:05:24
OK, I think you folks have figured it out for me. I just ran BPP without flats, but WITH Bias, Darks and Lights all created in SGP, and the screen door effect is gone! Here's the final result with no flats applied: https://drive.google.com/open?id=1X6dinyZxcoxHjm0_5AJ_XEhhVFfKsPui
The image looks quite correct I think (other than the fact that it needs flats!). What do you think?
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 20 22:02:44
yes that looks proper.

on the subject of the darks, i think when you have amp glows you need to avoid dark scaling (optimization). so for this sensor it would be best to make darks that match the lights in duration, and then calibrate without bias frames making sure "optimize" is unticked.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 21 02:04:13
Thanks. I didn’t actually have the optimize button checked, but I also didn’t have 600 sec darks because I’d never done 600 sec lights before, I’ll have to build up my library. Are you saying that I don’t need to use bias frames if I’m using appropriate darks with this camera? Thanks again for all your help!!
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: sharkmelley on 2018 August 21 03:25:07
Quote from: alanrock
Thanks. I didn’t actually have the optimize button checked, but I also didn’t have 600 sec darks because I’d never done 600 sec lights before, I’ll have to build up my library. Are you saying that I don’t need to use bias frames if I’m using appropriate darks with this camera? Thanks again for all your help!!

Looking at the example files you provided, the light and dark both have the "starburst" amp glow but the bias did not.  So to calibrate out the starburst you need closely matched lights and darks (i.e. same length exposure and same temperature) and you must disable dark optimisation (which you have done).  But you still need bias frames in order for the flats to work correctly.

Mark
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: sharkmelley on 2018 August 21 05:43:40
Quote from: alanrock
Thanks. I didn’t actually have the optimize button checked, but I also didn’t have 600 sec darks because I’d never done 600 sec lights before, I’ll have to build up my library. Are you saying that I don’t need to use bias frames if I’m using appropriate darks with this camera? Thanks again for all your help!!

Looking at the example files you provided, the light and dark both have the "starburst" amp glow but the bias did not.  So to calibrate out the starburst you need closely matched lights and darks (i.e. same length exposure, same temperature, same offset and gain) and you must disable dark optimisation (which you have done).  But you still need bias frames in order for the flats to work correctly.

Mark
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 21 09:15:16
So this probably isn’t a PI question, but does anyone know of any way to make my flats usable?
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: sharkmelley on 2018 August 21 09:43:21
Quote from: alanrock
So this probably isn’t a PI question, but does anyone know of any way to make my flats usable?

Run the FastRotation process on them - either Horizontal Mirror or Vertical Mirror or both.

Mark
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 21 10:40:41
Thanks! I guess I’ll try horizontal, then BPP again and if that doesn’t work I’ll run the vertical mirror and try again.
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 21 11:39:48
you should be able to tell what transform you need for sure by loading one of your lights with the fits reader set to up-bottom and then loading the same light set to bottom-up and see what transform you need to make them match.

but dont forget to set the reader back to whatever it was set to when you are done!

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 21 17:13:52
Well, I did a vertical mirror based on the advice above, but for some reason when I save the file and re-open it, there's a new file with an _thumbnail suffix appended. When I tried running BPP with the newly saved files, it blew up, I believe because of the thumbnails, which incidentally don't show up as separate files.
I got this:

Calibrating target frame 1 of 28
[2018-08-21 21:31:30] Loading target frame:
[2018-08-21 21:31:30] /Volumes/Astronomy Pix/Pictures/Astronomy/ZWO_Flats/Flats-0001 copy.fit
[2018-08-21 21:31:30] * Subimage 1 of 2
[2018-08-21 21:31:30] Reading FITS image: 16-bit integers, 1 channel(s), 5496x3672 pixels: done
[2018-08-21 21:31:31] 46 FITS keywords extracted.
[2018-08-21 21:31:31] * Subimage 2 of 2
[2018-08-21 21:31:31] Reading FITS image: 8-bit integers, 1 channel(s), 400x267 pixels: done
[2018-08-21 21:31:31] *** Error: Incompatible image geometry


Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 21 17:44:53
format explorer > double click fits > untick "thumbnail image" in 'override embedding settings' section, click OK.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 21 18:26:23
Well, I think I have somehow rendered my flats completely useless now. After mirroring them vertically and running BPP, the resulting finished product looks very blue. The c_d_r files look good if I run it without the flats though.
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 21 18:38:04
well the flats were weak in one channel and that can definitely produce a color cast, but it doesnt matter - you need to do color calibration (or at least view with STF channels unlocked) to see if the data is OK.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 21 19:02:38
Well, what makes the data “ok”? We don’t know if it’s flipped or whatever, at this point, do we? There’s no screen door effect in the flats of course, but maybe I don’t know what makes them good or bad. I thought it was just the orientation that was the problem.
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 21 20:27:34
OK, so this is interesting. I created some new darks, although they are only 300 seconds, not 600 like the lights. Here's the result of a BPP with the new darks and the mirrored flats. I'm a bit surprised at the amount of amp glow, but when I just do a straight STF (click the button in the toolbar), the result is actually not terrible, although there seems to be a serious gradient. Not sure how I'd go about fixing it. https://drive.google.com/open?id=1VHBdPMUqyLMmcfA6mqKcpRoQroub7har
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 21 21:32:13
well by OK, i mean that the colors seem somewhere in the ballpark (galaxies are white/tan, stars don't look insane), there's no vignetting or dust bunnies (if the flats are upside-down and you have dust, you'll definitely see that.).

anyway the right thing to do is just redo all the calibration frames in SGP; i consider trying to fix the calibration frames kind of a hack (but fun to try)

i processed the image you posted and the colors seem correct. the gradient is removable with DBE. i'm also seeing some  'typical' OSC + refracting optics problems - the blue channel is not well-focused while the red and green seem OK. or, the blue channel might just be suffering from "blue bloat" which i guess is normally taken care of with a UV filter.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 22 09:18:38
Perhaps this is a bit off topic, but can you give me some hints on removing the gradient with DBE? I've watched all the tutorials and read the book, but the settings in DBE are still a bit mysterious to me. Thanks!
A
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 22 10:40:43
the main gradient here is pretty well behaved so i just put a few samples in the corners and in the middle of each side, and a few along diagonals near the center of the image. i had to increase the tolerance to 2 to make sure all 3 channels were being picked up.

after extraction there is something of a large-scale blotchiness in the image but that's not super unusual if you're shooting in LP (and perhaps also the flats don't perfectly match).

the amp glow is still there on the right, indicating that the darks are not right though.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 22 10:44:00
I ran ABE on the image, saw the large scale blotchiness, and didn't go any further since my darks didn't match and I need to reshoot my flats. If I still have the blotchiness after the calibration files are corrected, is there any way to deal with _that_?
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 22 11:25:37
well, DBE gives finer control so there is a chance you can get a better background model by carefully placing samples.

there is a trick to eliminate background color gradients which is essentially to mask off the foreground and then use AtrousWavelets in chrominance mode and remove the largest scales, or some subset of larger scales. see this post:

https://pixinsight.com/forum/index.php?topic=5498.msg37760#msg37760

over the years alejandro has posted a lot of tutorials and flows here:

https://pixinsight.com/forum/index.php?action=profile;u=3800;area=showposts;sa=topics;start=0

also he has a website here: http://pixinsight.com.ar/ with lots of good stuff.

rob
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: alanrock on 2018 August 22 20:34:15
I finally got my 600 sec darks done today. I'm happy to report that when I used BPP without flats, all the amp glow is gone. Here's the result after an ABE, a DBE using Division(in an attempt to flatten out the background), and a couple of passes with Histogram Transformation. I didn't do any color correction or anything else, but I feel like I'm finally on the right track. Thanks for all your help!
Title: Re: Splotchy background after Batch Preprocessing and DBE or ABE
Post by: pfile on 2018 August 22 21:38:29
you're welcome, glad that is sorted out. hopefully you can get the new flats soon.

rob