Amp Glow with ASI183MM in PI Using Calibration Frames

[bulrichl]

I wonder where it comes from. I can't se it in the "telescope" settings:
View attachment 22592
Although I can't find any mention of it in the manual, it is possible that it gets written as part of the consequences of an (optional) plate solution.

Maybe you overlooked the last entry (at the bottom, right): 'Scope focal length'?

Bernd

 

[fredvanner]

Maybe you overlooked the last entry (at the bottom, right): 'Scope focal length'?

Oops! I must be going blind - since it is exactly what I was looking for, and could barely believe that it wasn't there. (I think I'll blame it on old age, not carelessness).

 

[bulrichl]

SGP writes XPIXSZ and YPIXSZ keywords in the FITS header if the configuration is complete, although this is not mentioned in the documentation (my frames captured with SGP contain XPIXSZ and YPIXSZ).

This statement refers to a SGP version that was up-to-date in December 2019, presumably v3.1.0.295 or the like.

Bernd

 

[dugstruble]

I ran all your files through WBPP, default settings except for auto pedestal (which didn't actually make much difference, but there were some zeros in the master without it). The focal length or pixel size is apparently wrong in the headers, so the pixel scale was wrong and didn't let Solver work, but I manually entered 0.7"/pixel and it solved fine. No sign of amp glow (or gradients) in the output as all. Looks great to me.

UPDATE: Looking at your raw lights, the header lacks your camera pixel size of 2.4μm. You should make sure that SGP is configured to include that key.

I was talking to Adam Block today. He suggested turning on astrometric solution box. I tried two tests. One at default and this one with me entering all the values in manually. That didn't help. I still had amp glow. I think I had that turned off at some point because I was having a problem some time ago, but I don't recall what it was. I sprained my ankle and am on some pain meds that have been making me rather loopy last couple days. lol It must be a different setting. I am going to try and reset WBPP next and try it again.

 

[dugstruble]

I ran all your files through WBPP, default settings except for auto pedestal (which didn't actually make much difference, but there were some zeros in the master without it). The focal length or pixel size is apparently wrong in the headers, so the pixel scale was wrong and didn't let Solver work, but I manually entered 0.7"/pixel and it solved fine. No sign of amp glow (or gradients) in the output as all. Looks great to me.

UPDATE: Looking at your raw lights, the header lacks your camera pixel size of 2.4μm. You should make sure that SGP is configured to include that key.

I give up. I tried running WBPP again with the same files I gave you after doing a factory reset AND manually entering all the specs in Image Solver with forcing the values. Still have amp glow. Perhaps it is a bug running PI on a Mac. I really don't know. I am not sure what the Image Solver would have anything to do with calibrating the dark frames with the lights to begin with. I guess I will just continue to deal with it in post processing.

 

[cloudbait]

I give up. I tried running WBPP again with the same files I gave you after doing a factory reset AND manually entering all the specs in Image Solver with forcing the values. Still have amp glow. Perhaps it is a bug running PI on a Mac. I really don't know. I am not sure what the Image Solver would have anything to do with calibrating the dark frames with the lights to begin with. I guess I will just continue to deal with it in post processing.

Using or not using ImageSolver will make no difference. I ran the files again with astrometric solution disabled. Didn't matter. As I'd expect. If the output pedestal is set to zero (the default) I do see a tiny residual bit of amp glow, although I wouldn't consider it enough to be a problem. Setting the output pedestal to automatic almost completely eliminates even that tiny residual. IMO the calibration here is about as good as it can ever be with a sensor producing a strong amp glow. And it is always recommended to set the output pedestal to automatic when processing narrowband images.

 

[pfile]

While that dialog is called "Telescope" it seems to be about the mount. Not the optics. Software I've used distinguishes between the two. Relevant to Juan's comment above about metadata, I think including the focal length, aperture diameter, and aperture area are pretty important!

i think this is just One Of Those Things - ASCOM refers to the mount and telescope together as Ascom.Telescope so i guess the SGP authors just carried the nomenclature to their dialog box.

i suppose this comes from the days of buying a telescope with some kind of mount included in the box? at any rate i think it's just a historical accident.

 

[fredvanner]

i suppose this comes from the days of buying a telescope with some kind of mount included in the box? at any rate i think it's just a historical accident.

Actually I think it comes from the days when the main users of ASCOM were observatory telescopes, where the telescope and mount were regarded as a single entity.

 

[pfile]

Actually I think it comes from the days when the main users of ASCOM were observatory telescopes, where the telescope and mount were regarded as a single entity.

could be, yeah.

 

[cloudbait]

Actually I think it comes from the days when the main users of ASCOM were observatory telescopes, where the telescope and mount were regarded as a single entity.

Regardless of how they want to categorize things, not being able to include the aperture diameter and area in the header is a problem. If you're doing photometry, you need those things, and shouldn't have to keep track of them outside the files.

 

[dugstruble]

Using or not using ImageSolver will make no difference. I ran the files again with astrometric solution disabled. Didn't matter. As I'd expect. If the output pedestal is set to zero (the default) I do see a tiny residual bit of amp glow, although I wouldn't consider it enough to be a problem. Setting the output pedestal to automatic almost completely eliminates even that tiny residual. IMO the calibration here is about as good as it can ever be with a sensor producing a strong amp glow. And it is always recommended to set the output pedestal to automatic when processing narrowband images.

I was looking around for the output pedestal in WBPP and can't find it. Do you know where it is at? Keep in mind that was only 10 lights I had uploaded. I have almost 300 lights. The amp glow seems to grow stronger with the more lights I run and becomes pretty obnoxious.

 

[bulrichl]

I was looking around for the output pedestal in WBPP and can't find it. Do you know where it is at?

Output pedestal:
In the ImageCalibration process: section 'Output Files'.
In WBPP: 'Calibration' tab, select a lights group (it will be highlighted in orange color), section 'Output pedestal Settings'.

You have two options, either

1) Output pedestal mode: 'Literal value', Output pedestal (DN): a value of 200 normally should be sufficient. If not, normally a calibration issue occurred (in this case most probably: not matching dark frames).

or

2) Output pedestal mode: 'Automatic', Auto pedestal limit: the default parameter of 0.00010 should be OK.

Bernd

 

[dugstruble]

Output pedestal:
In the ImageCalibration process: section 'Output Files'.
In WBPP: 'Calibration' tab, select a lights group (it will be highlighted in orange color), section 'Output pedestal Settings'.

You have two options, either

1) Output pedestal mode: 'Literal value', Output pedestal (DN): a value of 200 normally should be sufficient. If not, normally a calibration issue occurred (in this case most probably: not matching dark frames).

or

2) Output pedestal mode: 'Automatic', Auto pedestal limit: the default parameter of 0.00010 should be OK.

Bernd

Thanks! I'll give that a try.

 

[dugstruble]

Weird. Using automatic made the stars on the right look a bit blurry. I am going to try Literal Value and change the value to 200.

 

[dugstruble]

Output pedestal:
In the ImageCalibration process: section 'Output Files'.
In WBPP: 'Calibration' tab, select a lights group (it will be highlighted in orange color), section 'Output pedestal Settings'.

You have two options, either

1) Output pedestal mode: 'Literal value', Output pedestal (DN): a value of 200 normally should be sufficient. If not, normally a calibration issue occurred (in this case most probably: not matching dark frames).

or

2) Output pedestal mode: 'Automatic', Auto pedestal limit: the default parameter of 0.00010 should be OK.

Bernd

'Literal Value', Output pedestal (DN): a value of 200 seemed better with the stars, but see a bit of amp glow. I am going to try that on all 310 SII lights and see how that goes. I am presuming it will have an additive affect, though, with the amp glow.

 

[bulrichl]

Weird. Using automatic made the stars on the right look a bit blurry.

Please take a look at the FITS header of a frame that was calibrated in Output pedestal mode: 'Automatic': which Output pedestal value was used (IIRC this is documented in a comment of the FITS header).

Bernd

 

[dugstruble]

Please take a look at the FITS header of a frame that was calibrated in Output pedestal mode: 'Automatic': which Output pedestal value was used (IIRC this is documented in a comment of the FITS header).

Bernd

It says "ImageCalibration.outputPedestal: 568". I had to rerun it again in automatic, as I deleted the file, and seems better the second time around for some strange reason. Stars don't look blurry on the right side. Maybe because I am manually using a reference frame as opposed to automatic and I just randomly picked one of the 10 lights. There is a specific reason I run that manually, though. Maybe I should run the output pedestal at Literal Value (DN) at a higher value than 200?

 

[dugstruble]

I ran all my 310 SII lights with a 'Literal Value', Output pedestal (DN): a value of 200. Seems like the amp glow has an additive affect with the amp glow unfortunately. Perhaps running the (DN) value higher? Again this doesnt happen with the OIII and Ha. My guess is because there is more signal in those master lights.

 

[cloudbait]

I ran all my 310 SII lights with a 'Literal Value', Output pedestal (DN): a value of 200. Seems like the amp glow has an additive affect with the amp glow unfortunately. Perhaps running the (DN) value higher? Again this doesnt happen with the OIII and Ha. My guess is because there is more signal in those master lights.

Are you classifying that glow on the center left edge as amp glow? The amp glow is on the right edge, and is well corrected. The glow on the left is from a star just off the frame (SAO 114317) and obviously will not be corrected by calibration.

 

[dugstruble]

Are you classifying that glow on the center left edge as amp glow? The amp glow is on the right edge, and is well corrected. The glow on the left is from a star just off the frame (SAO 114317) and obviously will not be corrected by calibration.

Wouldn't it show up on both sides depending on how much I captured on each side of the meridian flip? In this case, most of my lights subs were on one side due to most of my lights being captured after the meridian flip. Also, if it is a star out of frame, wouldn't it show up in my Ha and OIII as well?