ASI1600 and 130PDS - about to give up, need help

[vlaiv]

4 hours ago, markse68 said:

Hi Vlaiv, I never heard this before- is it really true? Is it something that can be turned off? Seems a really bad feature if if it's true! 

I don't know - I'm poking in the dark really.

I do remember some people having issues with flat calibration when using automatic flats in APT. Once they switched to "lights" mode for taking their flats and manually selected exposure length - flats started working.

In general, I distrust any sort of automatic feature unless I'm 100% percent sure that I know how it is working. Some software can automatically calibrate subs (like SharpCap for example), and given that I mistook out of focus stars for inverted dust particles - I assumed (without any real foundation - except for that automatic flat issue - which might not have anything to do with APT itself, but rather non linear / clipping camera data, and knowledge that some software has this feature) that something weird is going on.

In light of those features being out of focus stars - I'd say that it is highly unlikely that it is software fault, but I do still think that ASCOM drivers should be used over native ones, just in case.

That is actually very easy to figure out - set of darks, and bias is taken with each driver and compared. If they are the same, then either driver is ok, but if mean ADU values or noise levels are different - I'd investigate further or simply use ASCOM as it is know to work well.

[markse68]

That’s a relief Vlaiv- I use ATP and I think any issues i have with gradients are to do with light reflections within the optical train rather than the program. I’m using ASCOM drivers and didn’t even know there was an auto flat function- I do it all manually apart from running the plans.

Mark

[Yoddha]

Hi Vlaiv,

The APT's CCD Auto Flat determines what exposure time is needed to take the desired flat frame. It is not applying the flats to the light frames. It is part of the processing. APT is not doing processing...

When APT takes an image it stores the data unchanged on the disk. If you are using the Histogram it is stretching only the screen preview.

[vlaiv]

3 hours ago, Yoddha said:

Hi Vlaiv,

The APT's CCD Auto Flat determines what exposure time is needed to take the desired flat frame. It is not applying the flats to the light frames. It is part of the processing. APT is not doing processing...

When APT takes an image it stores the data unchanged on the disk. If you are using the Histogram it is stretching only the screen preview.

I think there is some sort of issue with ASI294MC on certain gain settings that makes sensor non linear - it saturates on values lower than 65535 (around 50000, I believe). This might be the cause of issue with auto flats that I encountered (well, I just helped diagnose and mitigate it - I did not actually use the software or have the camera).

 

[Budgie1]

33 minutes ago, vlaiv said:

I think there is some sort of issue with ASI294MC on certain gain settings that makes sensor non linear - it saturates on values lower than 65535 (around 50000, I believe). This might be the cause of issue with auto flats that I encountered (well, I just helped diagnose and mitigate it - I did not actually use the software or have the camera).

 

The ASI294MC seems to be a special case. When using NB filters with this camera on unity gain (120) you do get gradients which don't always calibrate out, no matter how long the exposure on the flats is.

As I understand it; changing the gain to 200 on the ASI294MC takes the sensor out of a non-linear state and allows the flats to work correctly. With my own ASI294MC Pro, I use APT's auto-flats tool, with ADU set at 26,000 and the last flats I shot were 0.4375s exposure and worked fine with the Askar Dual-Band filter. For a light source I use a Samsung Tap A3 with an app called "LightBox" and 4 layers of white t-shirt.

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