live stack could not align when changing time of pose

[Opmc73]

Hi,

I have observed than if I set a pose time of 4s (or shorter) and start live stacking to take the 1st frame , then I stop live stacking , change to 60s and then restart the stacking and do a clear, SC shoot the 1st frame and then it is not able to align the other.
In such a case I have to restart to total new live stacking and sometime I have no other solution that close and restart the camera.

I experienced this issue several time because sometime I forget to rest the coorect stackingexposure time after having done a verification with a small exposure. Each time I have the same thing : no alignement found. It seems something is not reset when changing the exposure time even ifwe do clear.

Kind regards
Olivier

[admin]

Hi Olivier,

if this sort of thing happens, look at the 'Alignment' tab in the live stacking area - you will see an indication of how many stars are being detected in both the stack so far and in the new frame SharpCap is trying to add. I suspect that the short exposure initial frame may be darker than usual and therefore have very few detected stars, causing a failure to align the new frame with the stack.

You might be able to correct this with adjustments to the star detection settings, but it would be far better just to reset the stack so that it starts with a full length frame - the inclusion of a frame with a different exposure will cause unwelcome effects like the histogram peak gradually moving as the longer frames are added and start to outweight the values from the initial shorter frame.

cheers,

Robin

[Opmc73]

Hello Robin,

I understand.

I was reporting this because I though that when I do Clear stack SC was reseting everything like starting a new initial stack from scratch. But it does not work this way apparently and if the initial frame was 2s by example, then I , set exp time to 60s , redo live stack and do "clear stack" instead of resume, it seems to keep the 2s initial stars counted instead of starting with the new 60s 1st image of stars count.

Also , sometime I don't understand why ,even with 1 to 4s exposure by frame, it does not find enough stars to align because the initial frame often contains visually more than 20 stars that are brigth enough visualy. The Frame is not all black with one or 2 stars in my case (I am using a RC10 + reducer open 5.3 and an IMX571 cooled so I have stars really quickly).

Ps: I am using default setting "15 stars to align"

kind regards
Olivier

[admin]

Hi,

one thing that can be misleading is that you often end up viewing either the frames or the stack with a significant amount of stretching applied to the displayed image. This can make stars visible on screen that are actually vary faint in the raw, unstretched image. In the star detection settings in Live stacking there is an 'Optimize for faint stars' tickbox - ensure that box is ticked, as it ensures that the star detection is also done on a stretched version of the image, usually giving better results if the stars are rather dim. Even with that ticked, it's worth checking the image from the camera with no stretch to make sure you are not being deceived as to the brightness of the stars.

I think I understand now what you mean about stopping and restart live stacking not resetting the stack - this is actually deliberate. If you close the live stacking area and then re-open it within 60s, it will just carry on without clearing. This helps protect against accidentally clearing the stack - perhaps by opening the histogram tool or some other tool.

If you leave stacking closed for more than 60s, it will reset when re-opened - otherwise a manual reset is needed.

cheers,

Robin

[Opmc73]

...
I think I understand now what you mean about stopping and restart live stacking not resetting the stack - this is actually deliberate. If you close the live stacking area and then re-open it within 60s, it will just carry on without clearing. This helps protect against accidentally clearing the stack - perhaps by opening the histogram tool or some other tool.

If you leave stacking closed for more than 60s, it will reset when re-opened - otherwise a manual reset is needed.

cheers,

Robin

Hi Robin,

when I reopen before the 60s and I need to do a new stack because the previous one was started with a wrong exposure time, I do clear stack and this is when I have that issue. Is that meain that clear stack does not do a manual reset and I have something else to do ?

Regards
Olivier

[admin]

Hi Olivier,

yes, pressing the 'Clear' button is the right thing to do in this situation (when re-opening after less than 60s and you want a new stack rather than to continue).

cheers,

Robin