Dithering

Discussion of using SharpCap for Deep Sky Imaging
Post Reply
TimothyTim
Posts: 6
Joined: Fri Jan 25, 2019 12:00 am

Dithering

Post by TimothyTim » Wed Mar 06, 2019 1:03 am

Hello;

I'm not sure if I'm missing something, but I've been having issues with dithering and it's really a nuisance when doing narrowband long exposures. Every time a dither is issued I'm having to lose a frame for it. This is fine when doing 30s-120s exposures losing a frame for the good of the data, but when I'm running 10 minute exposures this can be aggravating... is there a way for SharpCap to pause imaging when dithering between frames? Maybe have it do 5-15 second exposures between dithers and discarding the result.

User avatar
admin
Site Admin
Posts: 2853
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Dithering

Post by admin » Wed Mar 06, 2019 8:34 pm

Hi,

At the moment there is no way to stop the frames during the dithering. So SharpCap discards any frames that occur while the dithering is in process. I hope to be able to address this in a future version.

Cheers, Robin

TimothyTim
Posts: 6
Joined: Fri Jan 25, 2019 12:00 am

Re: Dithering

Post by TimothyTim » Thu Mar 07, 2019 3:41 am

Robin;

Just imagine how much of a pain it is to discard a 10 minute frame because of that and use that as motivation to release that ASAP, thanks :)

User avatar
admin
Site Admin
Posts: 2853
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Dithering

Post by admin » Thu Mar 07, 2019 9:46 pm

Hi,

Well I have to admit that 10 minute sub exposures are somewhat longer than I expected people to be using with live stacking!

I wonder if a simple workaround would be to have SharpCap set the exposure down to say 5 seconds during the dinner operation and then set it back to the normal value when the dinner has settled. Most camera brands can treat a change in exposure as a request to cancel any long exposure in progress which should be fine. I would have to make sure that the shorter exposures captured during dithering could not make it into the stack although in an extreme case like yours I expect that if a short exposure did accidentally start being processed for stacking it would simply fail to align because the stars wouldn't be bright enough.

I will think about this one further.

Cheers, Robin

TimothyTim
Posts: 6
Joined: Fri Jan 25, 2019 12:00 am

Re: Dithering

Post by TimothyTim » Thu Mar 07, 2019 11:34 pm

Robin;

I've been using SharpCap for 10m+ exposures for over 6 months now, your facebook group shared many of my long exposure images.

I think if the dithering function in SharpCap is changed from based on time to based on how many frames at the preset exposure already defined during the live stack, where for example if you are doing live stack with 5 minute exposures, you tell the dithering function to dither once every X frames, and it gives you the ability to specify the settling variable in seconds and that frame is set to be dropped, this would be immensely helpful! I could at that point set for 10 minute exposures telling the system to dither every 4 frames, and would only lose 10-30 seconds instead of 10 minutes. Even if the frame is stacked I would be fine with that since I'm usually deleting the frame during the processing anyways.

poolemarkw
Posts: 73
Joined: Mon Mar 26, 2018 5:49 pm
Location: Indialanatic, FL

Re: Dithering

Post by poolemarkw » Mon May 06, 2019 3:42 pm

Hi Robin,

Do you have an idea as to when the Dithering function will be modified to only consume the amount of time required to actually do the dither, rather than consuming the entire frame exposure time?

Thanks,

Mark

AstroNutz
Posts: 2
Joined: Sat May 18, 2019 11:47 pm

Re: Dithering

Post by AstroNutz » Sat May 25, 2019 11:36 pm

admin wrote:
Thu Mar 07, 2019 9:46 pm
Hi,

Well I have to admit that 10 minute sub exposures are somewhat longer than I expected people to be using with live stacking!

I wonder if a simple workaround would be to have SharpCap set the exposure down to say 5 seconds during the dinner operation and then set it back to the normal value when the dinner has settled. Most camera brands can treat a change in exposure as a request to cancel any long exposure in progress which should be fine. I would have to make sure that the shorter exposures captured during dithering could not make it into the stack although in an extreme case like yours I expect that if a short exposure did accidentally start being processed for stacking it would simply fail to align because the stars wouldn't be bright enough.

I will think about this one further.

Cheers, Robin
I of course understand that with a lot of time and patience there is a workaround for dithering frame by frame in SharpCap, but I think the point is frankly there shouldn't have to be. In the general "start capture" menu there should be an option to set up dithering control in PHD2 and it should be a simple to use "Dither every X number of frames" and "Settle for X number of seconds" control panel. It shouldn't take but a few days of coding to make this happen, but you will make your users loyal for years to come.

Thank you.
Best,
Alan

Post Reply

Who is online

Users browsing this forum: No registered users and 0 guests