Overcoming ASI294MC Flats problems.

[PadrePeace]

I thought I’d chime in to offer my experiences with the ASI294MC when used with my Dual band filter for deep sky imaging. Particularly, I want to share how I have overcome the notorious Flats issue for which this sensor seems to have a reputation. 

Firstly, I find the 294MC is a very capable camera for OSC which I love using and I have never had any calibration issues in this mode. 

Secondly, for me the Flats issues really only occur with my Dual band filter which specifically exposes the apparent non-linear response of the sensor between 117-190 gain settings. I personally tried many different exposure, ADU, temperature Flats combinations at my preferred gain of 121 and just could not find flats that worked. That all changed once I read the SharpCap article on the 294MC sensor here: https://forums.sharpcap.co.uk/viewtopic.php?t=3855

I now avoid the 117-190 gain window when using my dual band filter (I shoot at 200 gain 30 offset) and have immediately found that my matched flats now work perfectly. The loss in stops due to shooting at 200 gain vice 120 gain is not that significant so I’d commend this fix to anyone struggling with their Flats for a 294MC /Dual band filter combo. Note that it seems that each sensor/dual band filter combination seems to offer a different looking Flat image, in the way that fingerprints are different. 

Finally, here is my latest image shot with this combo (L-extreme Dual) which used the flats shown very successfully as you can see. 

Hope this helps, clear skies

 

Edited February 13, 2022 by PadrePeace

[scotty38]

Nice image full stop!

[Chefgage]

1 hour ago, PadrePeace said:

I thought I’d chime in to offer my experiences with the ASI294MC when used with my Dual band filter for deep sky imaging. Particularly, I want to share how I have overcome the notorious Flats issue for which this sensor seems to have a reputation. 

Firstly, I find the 294MC is a very capable camera for OSC which I love using and I have never had any calibration issues in this mode. 

Secondly, for me the Flats issues really only occur with my Dual band filter which specifically exposes the apparent non-linear response of the sensor between 117-190 gain settings. I personally tried many different exposure, ADU, temperature Flats combinations at my preferred gain of 121 and just could not find flats that worked. That all changed once I read the SharpCap article on the 294MC sensor here: https://forums.sharpcap.co.uk/viewtopic.php?t=3855

I now avoid the 117-190 gain window when using my dual band filter (I shoot at 200 gain 30 offset) and have immediately found that my matched flats now work perfectly. The loss in stops due to shooting at 200 gain vice 120 gain is not that significant so I’d commend this fix to anyone struggling with their Flats for a 294MC /Dual band filter combo. Note that it seems that each sensor/dual band filter combination seems to offer a different looking Flat image, in the way that fingerprints are different. 

Finally, here is my latest image shot with this combo (L-extreme Dual) which used the flats shown very successfully as you can see. 

Hope this helps, clear skies

 

I have the same camera. Is this issue just with the L-extreme or does it extend to the L-enhance as well? I ask as I don't seem to have a problem with flats using the L-enhance and the asiair setting the exposure time in auto mode.

[PadrePeace]

31 minutes ago, Chefgage said:

I have the same camera. Is this issue just with the L-extreme or does it extend to the L-enhance as well? I ask as I don't seem to have a problem with flats using the L-enhance and the asiair setting the exposure time in auto mode.

If you are not having flats calibration issues with the L-enhance then I guess it’s fine. I don’t think the exposure time of the flats is the issue. I tried a lot of different flats exp times none of which fixed the fact that my flats actually added to my subs rather than subtracting artefacts. To be clear I used the Flats tool in NINA to produce both those flats that didn’t work at 121 gain and those that did work at 200 gain.

Perhaps you might consider posting an image of your L-enhance master flat and a calibrated image with the camera capture settings you used for both images in order to record your experience here for others?

Edited February 13, 2022 by PadrePeace