DSLR image downloads time out when long exposure NR is used

I recently used my old Canon XS with SGPro (latest). I’m enabling the camera’s long exposure noise reduction because it’s difficult to get accurate dark frames at the same temperature.

This means that SGPro has to wait for a long time for the image download. At 5 minute subs I do get the image but frequently see errors about timeouts. When I tried a 10 Minute sub the sequence aborted.

Is there any way to configure the length of the timeout? Or to let SGPro know that long exposure NR is on so that it can extend the timeout?

Richard Sewards

There is not, but I am fairly certain the timeout is 5 minutes. Are you seeing download times longer than that?

Yes, the download will be at least as long as the exposure when long exposure noise reduction is enabled. The camera takes a dark frame after the exposure. So, with a 10 minute exposure the download will take at least another 10 minutes.


I don’t know if it’s possible, but can you detect if long exposure noise reduction is enabled through the camera API? If you can, then perhaps the timeout can be adjusted.


Richard you might consider disabling that feature and just shooting one set of darks for all your frames? I don’t see any advantage to shooting w/ long exposure noise reduction. The disadvantages are you are reducing your imaging time by 50%, and you aren’t taking advantage of any noise rejection algorithms when creating a dark master.

I used to do that. Recently I’ve read that letting the camera do dark subtraction gives better results (see The Backyard Astronomer’s Guide, 4th edition). With SLRs it’s hard to control dark frame temperatures and some cameras do some additional processing under the hood before you get the raw image.

Better results than what?

Have you tried comparing the results? I think if you looked at the actual processing results, particularly when comparing in-camera dark frames to processing apps that use rejection algorithms, flat frames, and dark frame scaling the results would be better using a traditional in-camera thermal noise removal.

Plus you have the added benefit of twice the number of light frames, which would decrease noise by a factor of 2 by itself.

Well, this attempt was my first taking a lot of subs using this method. I intended to compare results with the other techniques. And noise reduces by the square root of the number of images, so twice as many images improves SNR by ~1.4.