Hi,

Just thought that I would add some new comments to this topic.
For me the current comments with White balance work for the colour balance and restore the final images after integration to what is expected i.e. green colour cast (removable with DBE). 50 and 50 for both. I agree with the idea of this being fixed as there is no point in changing it.
Offset for this camera should be 30 (recommended by ZWO). Not sure how much this changes things as I had been using 8. I think this again could be fixed as it is what is recommended by the manufacturer.
The other main issue for me has been in creating flats and calibrating light frames.
When I did all the things suggested in Bulrichi's tutorial I was getting awful clipping with unusable results even setting a pedestal to prevent negative values creeping in.
Anyway it has finally dawned on me that the main issue with this sensor is it's non linearity with very short exposures ( there are a few posts in Cloudy Nights exploring this issue in detail).
This makes using master bias a problem. I would suggest to always use dark flats as suggested in the tutorial referenced above. Unfortunately I was also using an EL panel for my flats and this resulted in very short exposures (0.07 sec) and hence the non linearity problem resurfaced. This I think resulted in the clipping I was getting.
So my humble advice for anyone in this situation with this camera would be.
Take flats with an exposure of at least 3 seconds
Use dark flats instead of bias in the calibration of flats and darks.
Do simple integration of darks and all master frames (without calibration and calibrate at lights calibration as per the tutorial)
I am in the process of redoing all my master reference frames and will test this approach in the next few days and hopefully report back.
I think that people who are using longer exposure for their flats will likely not experience much problem and this may account for the wide variation in opinions on this camera.

Hope that this helps

Mike

Hi Mike!

Thanks, real helpful!

I recognize the challenges of using an EL panel for flats. It needs to be very much dimmed to allow these longer exposures. So how to you solve that? My current solution is to dim it with a white t-shirt folded twice. But the t-shirt risks introducing new color shifts (it is white, but....)..... so good ideas are very welcome!

Just to illustrate: same sub calibrated with EL panel and different numbers of folded t-shirt + dimming acrylate in between, and different settings on the panel:




Magnus

Hi Magnus interesting isn't it. I am using several pieces of photocopy paper and using tuning by the number of sheets to arrive at a flat exposure of about 4 secs. For my panel this is about 6 sheets. My panel is not able to be eIectronically dimmed. I have not been able to properly check all the changes suggested by Bulrichi in his tutorial but it all makes sense. Because I have changed the offset I don't have any lights with that offset that I can test so the jury is out currently. My current work flow for my other lights is not using flats as I just find the end calibrated lights are too badly clipped to be usable. However another weekend looms so more testing is in prospect. Hopefully all of us with this camera will be able to share a standardised workflow that works and results in nicely calibrated lights. I am going to try to at least stick with the Gain 120, Offset 30, and calibrate flats with Master flat darks. I did try using a master bias with a slightly longer duration of 0.2 sec to calibrate lights (as per the suggestion for the Panasonic sensor) but the result was no different.
I will post results of testing to share with others. Still if it was easy it wouldn't be fun eh?
Stay in touch
Mike

Mike

Hi All,
I have written a short guide to starting up with this camera containing my insights from over a years use. I have attached it as a file. All I can say is this workflow works for me and also give solutions to common problems I have encountered. My apologies all the calibration and processing tips are using Pixinsight. I have put links to useful tutorials and on line resources.
It is an excellent value camera but sometimes can cause frustration in new users. Hence the guide.

Cheers

Mike