With this viewtopic.php?t=7454 , I just about made a couple of craterlets in Plato (honest). This was with the Skyris 618M (5.6µm) and no Barlow.
plato.JPG (10.43 KiB) Viewed 463 times
I have had very little success with my Barlow. I have some unique weather conditions. I live on the top of the Pennines. It is not unusual to see clouds moving in from the East and from the West but being stationary overhead.
No harm in giving it a try. I have been reading about that camera on Cloudy Nights, some turmoil caused there.
I think that all of these data are consistent with theory ?
At D=200 mm the Dawes or Raleigh limit says the best possible resolution could approach 0.6-0.7 arcsec (with 2-3X sampling). With f = 2000 mm and 5.6 um pixels the image scale of your setup is about 0.6 arcsec/ pixel - insufficient to maximise resolution but still sufficient (~2x sampling) to resolve two points (say the two sides of a crater) subtending 1-1.2 arcsec.
A craterlet 1.5 miles across subtends 1.25 arcsec and therefore your setup should be able to resolve it - as indeed it clearly has. The 'big 4' larger craterlets in Plato are in this size range and indeed bigger up to 2.7 mile (estim).
Also tbh - a thing like craterlet size can't really be that exact ? Aside from measurement uncertainty there is also the question of the size of the ramparts and the length of shadow cast by a low sun which will increases the apparent size. It is presumably tougher to detect the smaller and flatter ones.
The original images I posted up using the 12 inch and sampling the maximum resolution by 4X were really not that great in terms of SNR and image depth -- but I would contend did exhibit greater raw resolution showing not only the larger craterlets but also some of the smaller ones estimated to be only 0.6-0.7 miles across (i.e i and j) implying a higher resolution as is consistent with the physics of the set up.
Of course -- having said all of that -- imaging at a finer image scale may be the technically correct thing to do but - in practice - overly optimistic if - even with lucky imaging and many frames - sky conditions are usually limiting anyway.
thanks for testing more things for me - I had thought that you would be able to use the 'Custom' ROI option to get 512x512 or similar, but unfortunately that custom option is deliberately disabled on the 294MM as the interaction with the 2 different read modes is rather complex.
Can you confirm if you have found the pattern issue to be present if the camera is running at full area in 46Mp mode? I assume the problem is not there, but it will be good to know for sure.
There is also a suggestion in the CloudyNights thread that Firecapture does not have this issue - it would be interesting to confirm or deny that (ideally at an exactly matched ROI to one tested in SharpCap - ie both at 800x600, pan=0, tilt=0).
If FireCapture is free of the problem then there are two main possibilities
1) It's a ZWO bug in the SDK version used by SharpCap that isn't there in the version used by FireCapture - it may be possible to test by copying the SDK DLL across (provided it is the right version in terms of 32/64 bit)
2) SharpCap is setting up the camera differently and triggering the bug somehow
If we could distinguish between those two possibilities then it would be good.
Seems to be a simple answer in the end? The effect goes away when you don't record in high speed mode! Example below but seems a robust finding which is a relief and makes things easy. You can see the effect live at high zoom while recording as you toggle the high speed option on and off.
I wonder if Sharpcap is now almost too flexible in use so that it is too easy for the unwary to pick inappropriate combinations and then run away with the wrong idea that there is an inherent software problem ? Anyway maybe some way of conditionally disabling the high speed option ?
thanks for that - really helpful! I wonder if there is any use case for high speed mode in combination with the 46Mp mode (maybe it is OK at full resolution?), or should I just set the code up to disable high speed more (and hide the control) if the 46Mp mode is in use?
Actually, does the high speed mode actually increase the frame rate on this camera in 46Mp? If it doesn't do that, it can be disabled even if it is harmless at full resolution.
It does increase speed at 46 Mb -- but at the price of adding noise which most would find unacceptable. I have not tested the effect at 11Mb because all of those images looked fine anyway. Probably best to disable it at 46 Mb only?
