AWB doesn't work for DSOs

[donboy]

I know we have discussed this in the past but there is still no resolution. Many of us have the same issue with our ZWO cameras in that we can't get a color balance using the the Auto White Balance buttons. It use to work way way back and hasn't for a long time. Yes if one puts up a daylight image it works fine, but not astronomical images.

I have pointed this out to Sam (ZWO) and nothing resolved. https://zwoug.org/viewtopic.php?f=21&t=7116

So why in past it worked and why do other cameras and software are able to provide a continuous AWB? DSLRs can do it. Sharp Cap use to be able to do it. Frustrating.

Don

[admin]

Hi Don,

as you are aware, the AWB function is part of the ZWO SDK, so SharpCap just provides the button to press, not the implementation of what it does...

I can however offer some ideas that might help

* Perform AWB on a nice flat grey field of view in daylight and note down the final white balance values, then re-use those values manually for astrophotography. As long as you are not using different filters then this should give you fairly natural colours.

* Use the flats functionality in SharpCap Pro - when you take a flat of a colour camera you have the option to create a mono flat (that just fixes vignetting, dust spots, etc) or a colour flat that also will have the effect of correcting the white balance

* Hold off, leave the WB controls at default and fix the WB in post-stack processing - this will have the least impact on image quality.

cheers,

Robin

[donboy]

Robin. I had a several hour session with ZWO software tech on TeamViewer last night to tackle the non functioning AWB with ZWO color cameras. We did this live on Nightskiesnetwork.com. They tried changing the an asicamera2.dll and no change. They finally concluded that SC uses a Snap Mode white balance adjustment and that only works with exposures that are less than 500msec. Thus, DSO imaging uses longer exposures and the AWB mode of the ZWO cameras won't work in SC for longer exposures of 500msec or greater.

So what can be done to get you and ZWO to get AWB to work for longer exposures of 500msec and longer?

Don

[admin]

Hi Don,

Ok, so at least we understand the issue now. SharpCap needs to use Snapshot mode for longer exposures as it provides a much better mechanism for cancelling a long exposure in progress than video mode - that means that if you decide to change from 30s to 90s exposures, SharpCap can pretty much instantly stop the current exposure and get on with a new 90s exposure, so that means that the AWB provided by ZWO isn't going to be available for use in SharpCap on longer exposures.

I think that in a future version (3.2) I will be adding an auto-white balance button for the white balance controls in the live stacking, but I have no plans to add AWB for normal capture if it is not provided by the camera (it's my strong belief that it's best to capture images without this sort of processing and to apply this *after* stacking).

cheers,

Robin

[donboy]

Robin,

Thanks for your response.

I am a little concerned about those that use your software for EAA or live streamed color camera stacking. It is extremely frustrating and I've watched many give up because of this AWB issue. Due to the AWB issue I personally prefer to capture images with SC and feed .fits files to a stacking program like DSS. Mono imaging is a different story and SC live stack works well for this mode.

Thanks,
Don