Why would you need mirror lock? There is no light involved with darks so whether the mirror is flipping up or down during the "exposure" is of no importance, right?
Thanks for the reply. I am interested how do you take "darks",with a DSLR, in real time ? especially if you are using a remote obsys ?
Maybe I am wrong if so please correct me - Taking "darks" I thought was (quote) "Dark frames are images taken with the cap over the aperture of the telescope so no light can get in" - is this not correct ?
Yes this is correct. However, mirror lock refers to flipping up the mirror so the sensor becomes exposed before starting an exposure. The idea is that this way, the optical train has time to stop vibrating before the exposure time starts. What you probably mean is to enforce the mirror to stay shut when taking an exposure with the purpose of preventing light from coming in. First of all I am not sure if this is possible with any DSLR camera (they are designed to let light enter after all). Secondly I am not sure if keeping the mirror down actually blocks all light. Interesting thought though!
I knew what the normal "mirror lock" process was for but I was interested to see if the method could be over ridden to keep the mirror down not up - No idea if the "closed " mirror would block all light. Just a thought as the mechanism is there. Back to my black filter in a filter wheel idea then Thanks for replying.
I assumed that you knew but I wanted to be clear anyway
Many modern DSLR cameras support taking darks immediately following a light (in my EOS 700D I think it is called Long Exposure Noise Reduction though I may be wrong) and perhaps this functionality is available via an API as well. That may be another possibility but this would very likely not be available for all DSLR cameras, if available at all.
LNR exists and works on Windows software (Canon API) but stops exposures working correctly using Gphoto/Indilib so had to be switched off - on my Canon 100d.