Checking my understanding

[NeilG]

Robin,

there has finally been a couple of clear nights where I've been able to use the latest Sharpcap 3.1.

A few things have come to my attention that I need to check with you.

Background:-
I'm using a ZWO ASI1600MM-Cool attached to an f6.5 127mm APO for DSO imaging - mostly - for planetary work its attached to an f/10 Celestron C11.
Up until now I've only been using exposures in the 4 - 12 sec range on the brightest DSOs - so that I can familiarise myself with the camera, Sharpcap and the post processing in Pixinsight.

Situation 1:-
A couple of nights a go I decided that I wanted to check how good the tracking of my mount (Skywatcher EQ8) was and so I started some test exposures - capturing a sequence of 5 frames at each of 4, 8, 15, 30 secs - I was intending to go much further - up to 5 mins or more, but I noticed that above 15 secs I was getting a lot of dropped frames (~50% or more). This was using the 'native' ZWO driver that gets used if I select rhe first instance of the ASI1600 in the drop down list of cameras. So I tried playing with the USB bandwidth - it was initially on 'auto' but I kept reducing it all the way down - but it did not improve matters. I left that part of my evening and went back to my short exposure imaging.
Googling the isue the next morning indicated that I should actually be using the ASCOM driver for longer exposures.
I tried this the follwoing evening and hey presto - no problem - was able to capture sequenbces of frames up to 5 mins, with no drop outs.- didn't need to go any further - started to get some trailing @ 5mins.

Question: - is this the correct behaviour - I must use the ASCOM driver for long exposures?

Situation 2:-
Following on from the above. i had originally performed sensore anlysis on the ASI 1600 using the native driver - seemed to work well and the Brain had been recommending exposures between 8 and 15 seconds - so I had not been seeing any dropped frames in my imaging runs. When I switched to the ASCOM driver - which identifies itself as ASCOM 1 and tried to use the Brain - it told me that I had to perform the sensor analysis again.

Question - I'm guessing that when using the ASCOM driver it is not possible to identify the camera and use the 'other' sensor analysis from the native driver? (My workaround is to switch back to the native driver, measure the background and get the Brain recommendations - then switch back to ASCOM and use the recommended settings - good idea?)

Question - I have 3 ASI cameras - how can I tell Sharpcap which one is being used with the ASCOM driver so that it can use the correct sensor analysis file?

Situation 3
Just an observation really. When doing sensor analysis the measurement sequence is 'camera uncovered', 'camera covered' then 'camera uncovered' again. I'm sure there is a reason for that - or would it be possible to complete all the uncovered measurements in one go, followed by the covered measurement - or vice-versa?

Situation 4.
More of an enhancement request - when using live stacking the individual frames are saved using the generic 'framexxx.' filename - would it be possible to add a timestamp to the name, or provide a customisation feature like you have for other filenames?


Thanks for producing such agreat piece of software.
Regards
Neil

[admin]

Hi Neil,

Q1 - no, you shouldn't need to use the ASCOM driver at all in SharpCap for long or short exposures, but maybe there is a bug with longer exposures that I need to investigate here. Please let me know as much as possible about your setup (PC specs, camera settings, output format, etc) so I can repro your situation as closely as possible with my 1600MM-cool.

Q2/Q3 - SharpCap can't tell between different ASCOM devices unless the ASCOM driver implements the SensorName property, which unfortunately the ZWO driver doesn't, so SharpCap has no real way of working out which ZWO camera it's talking to - as you suggest this is a problem for the sensor analysis if you have more than one camera.

Q4 - The last part of the sensor analysis (measuring the amount of gain each gain setting applies) needs you to know figures that come out of the dark measurements to do it properly, which is why there is a light/dark/light sequence. I suppose it would be possible to do the dark measurements right at the beginning, but you still have to cover then uncover the sensor to run them

hope this helps,

Robin

[NeilG]

Robin,
thanks for the prompt responses.

I'll pop out if and when it stops raining to check my laptop spec and I'm prerty sure the log file might still be hanging around.

and for the other 3 questions - you confirmed my thinking.
thanks
Neil

[admin]

A quick follow up question - do you get dropped frames only when capturing or do they get dropped when just viewing? Also USB2 or USB3 connection?

I've had my ASI1600MM sitting here running frames up to 240s in MONO16 mode on both USB2 and USB3 cables and had no problems with dropped frames at long exposures yet (I do get dropped frames when tinkering with the parameters or on USB2 at short exposures).

cheers,

Robin

[NeilG]

I'll check if frames are dropped only when capturing tomorrow.

[NeilG]

Robin,

I've managed to do some further tests and hopefully the problem is now much more obvious.

Setup was as per previous - APO127-> EFW-Mini-> ASI1600 -> 1m cable -> powered hub -> 5m cable -> into X220 laptop.

Test 1:-
Test 1
Sharpcap v 3.1.5027

Camera start up in MONO8, full frames, select FITs as save file type
- All preview frames ok - non being dropped
- Test exposure1 - 30secs via capture sequence, gain 139, offset 21,
- capture stopped after 6 frames -no drops

Switch to MONO16
- All frames being dropped in preview mode
- Test stopped

Checked the 'save settings' box so that cam would restart in MONO16 mode

Test 2
Restart SC
Camera start up in MONO16, full frames, select FITs as save file type
- first frame dropped in preview mode, but OK afterward
- Test exposure1 - 30secs via capture sequence, gain 139, offset 21, MONO16, full frame, FITs capture
capture stopped after 6 frames -no drops

Switch to MONO8

- initially says -1 frames dropped then All frames OK in preview mode
- Test exposure1 - 30secs via capture sequence, gain 139, offset 21, MONO16, full frame, FITs capture
, all frames being captured
•
Switch to MONO16
• frames preview OK - no drops

I've attached to log files

So it seems to be that if the camera starts in MONO8 mode and is then switched to MONO16, frames get dropped. Also - did a quick check with 4 sec exposures - got same problem?

any thoughts - my workaround obviously is to always start the cam in MONO16 mode?

Neil

[NeilG]

Further test indicates that there is no problem with 2sec exposure or less - problem seems to start at 4sec.

Replicated the problem on a second PC with a direct connection from the camera to USB 3 port via a 1m cable - 2nd PC is a core i7, 3.4Ghz, 16Gb and 480Mb SSD.

Now I am confused

[admin]

Hi,

thanks for the further details - I think the 2s to 4s thing is actually revealing - if you have the 'Output Format' control set to auto then it changes from capturing video at 2s to capturing stills at 4s, so I suspect that this is why the problem is occuring only at 4s exposures and above. Would you be able to test to see if this is the case? ie:

* Test at 2s with the output format set to FITS or PNG and auto off - does this work if you change from MONO8 to MONO16

* Test at 4s with the output format set to SER - does this work if you change from MONO8 to MONO16?

I still get no problems running through your series of steps - ie

* Start camera in MONO8
* Capture 5 frames
* Switch camera to MONO16
* Capture 5 more frames

I did see a dropped frames number of -15 at one point (oops) but it didn't affect the outcome - frames captured successfully.

What settings do you have for your file naming? Maybe some combination of different naming settings causes this?

cheers,

Robin

[NeilG]

Thanks robin,

i'll test on Friday morning- now that I know its not the obsy setup - I can do the tests in the warmth of my office.

As I said, there is a workaround - I'll just make sure that the camera starts in MONO16 and only switch to MONO8 if the Brain thinks its a good idea.
Reards
Neil

[NeilG]

Robin,

Results of my tests this morning:-

Default settings on SC startup
SC version 3.1.5029
show tips - checked
automatically connect to camera - not checked
automatically restore camera setting - NOT checked

preferred video format - SER
preferred still format - FITS

Organise captured files into subfolders:-
first by - Date then by - Target name

Use sortable date format - checked


Test 1:-
start SC, select camera
colour space - MONO8
Capture Area - 4656 x 3520
Binning - 1
output format - Auto (SER file)

Exposure - 50ms on startup
Frame rate - maximum, turbo USB - Auto (100), high speed mode - off
Gain 139, brightness 10

Change exposure to 2 sec - using quickpick list
Output format changes to FITs
no frames being dropped in preview
Capture 5 frames - OK

Change to MONO16
Output Format stays at FITS
preview - initially dropped 2 frames then stabilised to previewing all frames OK
Capture 5 frames - All OK

Close SC - to ensure clean log file, renamed log file Test 1.....



Test2
start SC, select camera
colour space - MONO8
Capture Area - 4656 x 3520
Binning - 1
output format - Auto (SER file)

Exposure - 50ms on startup
Frame rate - maximum, turbo USB - Auto (100), high speed mode - off
Gain 139, brightness 10

Change exposure to 4 sec - using quickpick list
Output format changes to FITs
no frames being dropped in preview
Capture 5 frames - OK


Change to MONO16
Output Format stays at FITS
preview - all frames being dropped
Capture 5 frames - All frames being dropped
capture aborted

Closed SC, renamed log file to Test2.......



Test3
start SC, select camera
colour space - MONO8
Capture Area - 4656 x 3520
Binning - 1
output format - Auto (SER file)

Exposure - 50ms on startup
Frame rate - maximum, turbo USB - Auto (100), high speed mode - off
Gain 139, brightness 10

Change output format - switch off auto, select png
Change exposure to 2 sec - using quickpick list
no frames being dropped in preview
Capture 5 frames - OK


Change to MONO16
Output Format stays at png
preview - 1 frame dropped initially, otherwise preview OK
Capture 5 frames - OK

Closed SC, renamed log file to Test3.......



Test4
start SC, select camera
colour space - MONO8
Capture Area - 4656 x 3520
Binning - 1
output format - Auto (SER file)

Exposure - 50ms on startup
Frame rate - maximum, turbo USB - Auto (100), high speed mode - off
Gain 139, brightness 10

Change output format - switch off auto, select png
Change exposure to 4 sec - using quickpick list
no frames being dropped in preview
Capture 5 frames - OK


Change to MONO16
Output Format stays at png
preview all frames being dropped
Capture 5 frames - aborted - no frames being captured

Closed SC, remaned log file to Test4.......


Test5
start SC, select camera
colour space - MONO8
Capture Area - 4656 x 3520
Binning - 1
output format - Auto (SER file)

Exposure - 50ms on startup
Frame rate - maximum, turbo USB - Auto (100), high speed mode - off
Gain 139, brightness 10

Change output format - switch off auto, select SER
Change exposure to 4 sec - using quickpick list
no frames being dropped in preview
Capture 5 frames - OK


Change to MONO16
Output Format stays at SER
preview all frames being dropped
Capture 5 frames - aborted - no frames being captured

Closed SC, renamed log file to Test5.......





Other Notes - looks like the AUTO output format change from video to still occurs between 1sec and 2sec, not between 2 and 4?


Log files attached.

hope this helps
Neil