Vertical Bars, how to minimize or eliminate?

[gbarr56]

Is there anyway to get rid of the two vertical lines on the left hand side of the image? Attached is the image. It's strange as I don't see these in my LRGBO images but I see it faintly in my Ha image. I'm not sure what it is but wondering what suggestions there are to make this more uniform. I tried DBE and ABE but it doesn't seem to have an affect. Any suggestions/comments. I have an SBIG STF8300M camera.
This is a calibrated master run through the WBPP script with 60 Sii Subs.

Any ideas what would cause this?
Any suggestion on how to minimize or eliminate the vertical thick bars on the left of the image?

 

[pfile]

hi - there was no attachment. hard to say without seeing it but 'messed up' edges in astroimages is common if you are dithering your subexposures. at any rate please post the image...

rob

 

[gbarr56]

Ok, I saw my file was too large. I just added it successfully.

 

[oldwexi]

Where ????

 

[gbarr56]

uh boy....it's there now. Or at least I hope it is.

 

[pfile]

i see it - yeah that's something else than what i was thinking of. not sure what that is...

 

[bulrichl]

Any ideas what would cause this?

Check the calibrated Ha frames for clipping of data in the low range. If this is the case, apply an appropriate output pedestal.

Bernd

 

[gbarr56]

I'm really sorry, how do you apply an output pedestal and how do you know if it's appropriate? Sorry for the basic question but a newbie.

 

[pfile]

if you apply the Pixelmath expression $T==0 to a calibrated subexposure, and the result image has a bunch of white pixels all over the place, then you need an output pedestal.

however, i wouldn't necessarily expect the pixels that have been clamped at 0 by the calibration process to all fall on one side of the image. usually they are peppered all over the place and you see a "moire" pattern in the integrated image. still it is worth a try to investigate if the problem is calibration or not.

rob

 

[robyx]

Is there anyway to get rid of the two vertical lines on the left hand side of the image? Attached is the image. It's strange as I don't see these in my LRGBO images but I see it faintly in my Ha image. I'm not sure what it is but wondering what suggestions there are to make this more uniform. I tried DBE and ABE but it doesn't seem to have an affect. Any suggestions/comments. I have an SBIG STF8300M camera.
This is a calibrated master run through the WBPP script with 60 Sii Subs.

Any ideas what would cause this?
Any suggestion on how to minimize or eliminate the vertical thick bars on the left of the image?

I had a similar issue in one processing session months ago. Considering that the background irregularity is almost distributed in columns
I corrected it creating a background model an I used it to flatten the image this way:

1. clone the image and generate a starless image (first image of backgroundModelGeneration.png)
2. remove the first 5 wavelet layers, this generates an image with almost no stars containing a smooth version of the background (second image of backgroundModelGeneration.png)
3. select a row that is representative of the background issue (I picked the one highlighted in the third image of the sequence)
4. I used pixelmath with this formula "pixel($T, x(), xxx)" where xxx is the row number that you've selected (forth image of the sequence)
5. rename the latter image as BCKMODEL
6. use PixelMath with the formula "$T/BCKMODEL*avg(BCKMODEL)" to correct your defected image, see the resulting bafore/after comparison attached

Depending on the severity of the issue on the real image this could require adjustments but maybe this process works sufficiently on your eyes. The remaining small halos could probably be flattened with DBE.

I hope this helps,
Robyx