ZWO ASI294MC Pro issues and tests

[The Thing]

The 3 darks have had the same Auto Stretch function applied. Left is ASICAP, middle is APT using the ASCOM driver, right is SharpCap. The ASCOM driver is obviously doing something different, the other two programs are using the Native driver.
The settings were the same for each (middle of sets of 30 subs) except the camera offset was 30 in the ASCOM driver (the default) and 28 in the Native driver.

I think I need to try some subs using the native driver...

[The Thing]

SharpCap settings were:
[ZWO ASI294MC Pro]
Debayer Preview=Off
Pan=0
Tilt=0
Output Format=FITS files (*.fits)
Binning=1
Capture Area=4144x2822
Colour Space=RAW16
High Speed Mode=Off
Turbo USB=80
Flip=None
Frame Rate Limit=Maximum
Gain=120
Exposure=300
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=50
Brightness=28
Temperature=0
Cooler Power=24
Target Temperature=0
Cooler=On
Auto Exp Max Gain=285
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Mono Bin=Off
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1
TimeStamp=2019-02-18T13:26:23.9626724Z
SharpCapVersion=3.2.5897

[The Thing]

ASICAP settings were:
[ZWO ASI294MC Pro]
Auto Exp Max Exp = 100ms
Auto Exp Max Gain = 285
Auto Exp Target Brightness = 100
Bin = 1
Brightness = 28
Capture Area Size = 4144 * 2822
Colour Format = RAW16
Debayer Preview = ON
Exposure = 300000000us
Flip = None
Gain = 120
Hardware Bin = OFF
High Speed Mode = OFF
Mono Bin = OFF
Output Format = *.FIT
Raw Foramt = ON
StartX = 0
StartY = 0
Temperature = -0.3 C
Timestamp Frames = OFF
Turbo USB = 80
White Balance (B) = 50
White Balance (R) = 50

[The Thing]

APT FITS file header information:
DATE-OBS= '2019-02-16T09:16:10' / The UTC date and time at the start of the expo
HIERARCH CAMERA-DATE-OBS = '2019-02-16T09:16:10' / The UTC date and time at the
EXPTIME =                 300. / The total exposure time in seconds             
CCD-TEMP=                   0. / Temperature of CCD when exposure taken         
XPIXSZ  =                 4.63 / Pixel width in microns (after binning)         
YPIXSZ  =                 4.63 / Pixel height in microns (after binning)       
XBINNING=                    1 / Binning factor in width                       
YBINNING=                    1 / Binning factor in height                       
XORGSUBF=                    0 / Sub frame X position                           
YORGSUBF=                    0 / Sub frame Y position                           
EGAIN   =     1.00224268436432 / Electronic gain in e-/ADU                     
FOCALLEN=                  615 / Focal Length of the Telescope in mm           
JD      =     2458530.88978009 / Julian Date                                   
SWCREATE= 'Astro Photography Tool - APT v.3.65' / Imaging software             
SBSTDVER= 'SBFITSEXT Version 1.0' / Standard version                           
SNAPSHOT=                    1 / Number of images combined                     
SET-TEMP=                   0. / The setpoint of the cooling in C               
IMAGETYP= 'Dark Frame'         / The type of image                             
SITELAT = '+00 00 00.000'      / The site Latitude                             
SITELONG= '-00 00 00.000'      / The site Longitude                             
HUMIDITY=                75.39 / The Humidity                                   
TAMBIENT=                 8.87 / The Ambient Temperature                       
GAIN    =                  120 / The gain set (if supported)                   
END   

[RobertM]

What do they look like if you apply the same stretch to all three (rather than auto-stretch them individually) ?

Anything obvious looking at the histograms ?

Robert

[The Thing]

Hi Robert, I have applied the same stretch to all three using the right click menu function... I need to get some stats, also try Nina as that uses the Ascom driver.

[RobertM]

I understand that the 294 implements on chip hdr - could this be part of the problem ?  If that is the case then it's likely your flats and probably darks are all wrong.

Robert

[The Thing]

I understand that the 294 implements on chip hdr - could this be part of the problem ?  If that is the case then it's likely your flats and probably darks are all wrong.

Robert

The real peculiarity vs. other cameras sensors is that each bayer pixel group is composed of four very small bayer pixel groups which get binned apparently. This could give you an 8K sensor but apparently Sony has locked out that capability (ZWO says so). As you say this enables Quad Bayer Coding HDR . I hope that's not enabled! Otherwise there is a lot of on chip processing going into every calibration frame! Maybe that explains the grey dark from the ASCOM driver (using APT and NINA)  - could it be it's not controlling that mode properly so I have been getting HDR darks :{.

Hopefully tonight I can get some subs to test using the native driver using ZWOs ASICAP and SharpCap, forecast is good but the Moon is rampant.

[The Thing]

Well. I've takn some subs (E300s G120 O28 T0C) in ASICAP and the histogram is well off the left hand side, in APT there was only ever a hint of a gap whatever the exposure. The subs look better on screen even though ASICAP has no screen stretch function. I've run them quickly through DSS and there seems to be an improvement. Now I only need some flats taken with ASICAP so I can do a calibrated stack.

I've switched to SharpCap but I suspect those subs will be washed out as the Moon is now well up.

So there may be hope yet.

[RobertM]

I was thinking earlier that you might need quite a gap to the LHS of the histogram to get you off the high gain part of the HDR curve.  Perhaps the way to approach it but it may not be as easy to replicate that in all circumstances.

Fingers crossed.

Robert

[The Thing]

Discovered something new today from a neighbour funnily enough. This area has a mains supply renowned for microsecond power dropouts, the neighbour had to get UPS devices for his PC and several other things which kept crashing or just acting up.  I suspect there are also spikes caused by agricultural machinery and the local shellfish processing plants. The oysters and mussels tend to be processed at night at times when the tides are right for harvesting so they can be shipped out fresh to market in the morning. I can hear the hum of the machinery from the observatory when the wind is right. Maybe I should invest in a 12v battery after all...

[Carole]

I don't know much about electricity, but would a regulated power supply help with this?

Carole

[MarkS]

Discovered something new today from a neighbour funnily enough. This area has a mains supply renowned for microsecond power dropouts, the neighbour had to get UPS devices for his PC and several other things which kept crashing or just acting up.  I suspect there are also spikes caused by agricultural machinery and the local shellfish processing plants. The oysters and mussels tend to be processed at night at times when the tides are right for harvesting so they can be shipped out fresh to market in the morning. I can hear the hum of the machinery from the observatory when the wind is right. Maybe I should invest in a 12v battery after all...

It's not a stupid idea.  I run my entire observatory off trickle charged 12v car batteries.  I do the same at DSC and did the same at Astrofarm, just in case someone accidentally unplugs me!  Any power glitch just means the battery stops trickle charging for a while.

But it won't sort your ASI294MC issues, I'm sad to say.

Mark

[RobertM]

Duncan,

Since this is a camera that can switch between normal and hdr modes I'm wondering if there is a gain setting beyond which it switches in.  If so then perhaps that might indicate an answer or at least a pointer.  Have you tried much lower ADU values for your flats ? I know it's far from ideal but that might be worth trying. 

Actually... looking at the ZWO web site, the high gain switch seems to be at gain 120 - are you using values above or below this ?  If the camera does have two modes then you should probably steer clear of the HDR mode at least till you can get stability and understand what's going on.

In any case have you made any progress ?

Robert

[The Thing]

Hi Robert,

Thanks for the thoughts. I use unity gain 120 all the time except for target alignment etc. What I have found is setting the driver Offset value to 4 instead of the default 30 seems to fix a lot of the problem. It was the suggested setting after a SharpCap smart histogram measurement. It also suggested gain 121and exposure 119 so I've done a whole load of sub's at that setting and am now trying to process them in PI. I'm having to relearn masks and noise reduction techniques as its been a while since I had sub's worth processing that far. Looking hopeful.

Duncan