Short Exposure Times

I’ve been having a problem taking my flats and dark flats using sequence generator pro. Here are the details of the relevant equipment that I am using:

SGP Version:
Camera: Canon EOS Rebel T3i, modded by Gary Honis

I notice that SGP supports typing in many different exposure lengths, mostly in seconds. It even supports a half-second by typing in 0.5s. However, through testing with BackyardEOS (my prior software of choice), the appropriate exposure length for my flats is 1/10 of a second, or 0.1s, at ISO 100. While this is a valid exposure length in the Canon software, in SGP I get the following error:

Canon: Error in EdsSetPropertyData (PropID_Tv) Error: EDS_ERR_DEV_BUSY

Furthermore, I take bias frames, which DeepSkyStacker asks for and uses. For these, my appropriate exposure length is the shortest possible, 1/4000 sec (0.00025s). I want to be able to capture ALL of my frames in SGP if possible.

Thank you!


This seems to be something specific to exposure of 0.1s. 0.125 works fine as does 0.25, but I have the same issue with my 60D. I’ll look into this more…it’s rather odd especially since we get these values from the camera!

Also for bias just enter 0 for the exposure time and SGP will use the fastest exposure that your camera can take. When you select bias as the “Type” SGP doesn’t even allow you to enter an exposure and will set it at 0.


Sounds like a plan. However, I only get four frame types (Light, Dark, Flat, Bias). I normally take and stack five frame types in Deep Sky Stacker (Dark Flats is the missing one).

Dark Flats are just Darks taken at the same exposure as your flats, you shouldn’t need a separate type to accomplish this.


Good point - it’s just semantics. Didn’t even think about that. Thanks for the response!


Thought I’d follow up on this - in a day or so I’ll be taking my gear down, so I’ll need to know whether I can take my flats using SGP or if I’ll have to use BackyardEOS for the time being. Thank you!


There likely won’t be a release that addresses this for a week or so.


I found that having such fast exposures for flats causing shutter shadowing problem and flats not get exposed very well. I don’t know how you make your flats, but I use EL panel which is very bright, so I had to place a couple of layers of white t-shirt in between and using ISO200 I do 3 second flats. Now my flats are perfect. It won’t be a problem for SGP to take 1-2-3 seconds flats and dark-flats, just rise your exposures by dimming the incoming light somehow.
Hope it helps.