Problem Graduation banding

[Jkulin]

Hi All,

I have a problem when previewing an image when framing and focusing, there is a large graduation at the top of the image and no matter how I stretch it, it is always there.

Now my first 10 min sub for framing and focus was as shown below: -

It doesn't matter how short or how long I take the test image for or how little or great I stretch it, I always appear to have this gradient.

So I thought in for a penny and took a proper sub, nothing different apart from sequencing the image and I have the following image: -

Both have been stretched in the standard STF of PI, I'm at a loss really, it doesn't seem to matter whether I am using APT of SGP the result is the same, now the other night I couldn't get any image without the graduation and I was shocked when the last one came down without any gradient.

Someone tell me I am being stupid and missing something fundamental.

On Friday night I even took a preview with the lens cap on the camera without it being attached to the Scope and got the same gradients.

I'm totally confused.

Appreciate your thoughts and call me what you will as what little hair I have has now gone!

 

[Jkulin]

Not had any comments but thought I would update the thread, I spoke to Vince at Atik and he says that it is to do with Pre-Charge Subtraction and that most developers should switch this off but APT and SGP apparently don't which is what causes the problem, he claims that although you may think that it is is switched off, that it actually isn't and that the best way forward is to use Artemis Capture and because that is their software that you can be sure that it is switched off and that it might be easier to use that for the initial focus and then once done use the other software, he also advised that MaximDL is compliant with these procedures.

So lets wait and see as the previews last night were abysmal. as below: -

So will try this tomorrow night if it stays clear.

[Thalestris24]

Hi

Are you sure you don't have any light leakage? How do your calibration frames (darks, flats, bias) come out?

Louise

[Jkulin]

Hi Louise,

Yep 100% sure there are no light leaks, I sent the images to FLO where the scope was purchased from and they said it is the camera, contacted Vince at Atik and he says it is the software.

I made sure that there are no light leaks by ensuring that the complete focusing tube was wrapped up in black material so that there was no chance of any light entering.

All of my flats, bias's and darks are perfect as are my subs, it just seems to be when the images are stretched when using live view, Vince at Atik said it is the fault of the software developers not switching off the pre-charge subtraction, if it is clear tomorrow then will try using their Artemis Capture software.

[Jkulin]

oops sorry posted in the wrong place.

[Bukko]

Hello John,

Good to know you have resolved the banding. Never personally suffered from it, so could not help. On the focus, I see in your sig that you have a motor focus on the esprit, is it under autofocus control, or "manual" through a hand controller? The autofocus should deal with any issues you have, if manual, I assume you have a Bahtinov mask to suit? If not, then I reaally recommend them.

Only other thought is the seeing conditions limit the sharpness obtainable. With enough subs, the deconvolution tool in PI will help, but personal opinion, this is often overused, making the image look over-processed.

Hope this helps.

Gordon.

[Jkulin]

Hi Gordon,

Sorry my post above yours was posted in the wrong place.

No the banding isn't resolved when viewing, it is still prevalent.

According to Vince at Atik the problem exists because of the software doing a "Pre-Charge Subtraction", he advises that their software Artemis doesn't do this and that for viewing it would be better to use that. APT isn't as bad but SGP does seem to be the worse for it, indeed I could mess with the standard stretching, but it is still there.

After capturing some more images on Thursday night, I tend to always try and get the auto option working before resorting to manual with a Bahtinov mask. The seeing conditions were good on Thursday night

I agree about the deconvolution tool in PI, I don't use it at the moment as I agree overuse can make the image look false.

As you can see the Ha image below does not show any graduations and this image has just been stretched and nothing else, focusing isn't bad either, it is just a PITA to get focus whilst using the viewing option: -

Thanks once again for your comments.

[Starflyer]

I'm confused by this, I'm using SGP with my Atik 460EX and I don't see any gradient. I'm using the Atik Ascom driver, maybe this is the difference.

I'd be disappointed by Atik's response if it were me. SGP is used by thousands of people now and of there is a problem then Atik should be working with the SGP devs to get it fixed, they're quick to get problems fixed.  I wouldn't move away from SGP, and if he'd said that to me I'd take it as him saying "If you want to remotely image then buy a different camera brand"!

[Jkulin]

The gradient is only visible when you use the Frame and focus option and you have to stretch using either low,medium or high stretch, these are standard stretches.

I have just set it up in my dining room to try and see if there were any settings wrong and taking a 3s image with the lens cap on resulted in this with a high stretch: -

@RayD thought the culprit might have been the Ascom settings set as high priority, you can only show this when the camera is disconnected as below: -

Indeed if you enable the high priority then the gradients are even worse as below: -

I am really at a loss, running Atik Artemis all I got was a very noisy image with no banding.

[RayD]

John open up your profile manager and look under the camera tab (not ASCOM, just the camera setting in SGP). There is a check box at the bottom called high speed download. Make sure that is unchecked. It is only used for framing and focus and not during a sequence. That causes the issue you are having. 

[Jkulin]

Ray, I owe you a very large beer, unchecked it in the Equipment profile and the results speak for themselves in SGP: -

x

So it would appear that SGP ignores whether it is switched off within the ASCOM  program but, with APT it accepts it the check box as below: -

Well one very pleased person, thanks for everyone's help and especially you Ray.

[RayD]

Great stuff, glad it's sorted John