asi120mm exposure duration in maximdl using vbs

tylerjw98

I'm noticing some strange behavior when using a Maximdl vbscript to execute exposures on a asi120mm. The script will call for varying exposure duration (between 1 and 60 seconds to evaluate the linearity of the ccd response), but then after just a few seconds (much shorter than the commanded duration), the exposure has ended and starts to download. I've run the same script on other astro cameras with no problem. Is there a known timing problem with the ASCOM v1.0.1.17 ? I'm using MaximDL 6.11 in win10x64

Thanks-

Tyler

Sam@ZWO

can you tell us how to repeat?

tylerjw98

Sam, I sent you a separate message with the script that I used to capture the images. You'll need MaximDL and an adjustable illumination source (since the script is intended to evaluate the linearity of the ccd). When running the script, you'll notice that the requested exposure duration shows up correctly in MaximDL camera status, but is often cut short (for example: the requested duration might be 15 sec but only lasts 2 seconds...) . I've run the script successfully a number of times with a starlight xpress camera so I'm fairly confident it works... (but realize some of the ascom drivers have varying capabilities...)

Let me know if you need any other details-

Thanks.

tylerjw98

Sam,

Just following up.... I tried using your latest ASCOM driver (V1.0.1.20 ) and still see the same issue / bug where the exposure duration is different than requested. I'm able to work around this successfully by taking a second exposure with the same requested duration and discarding the first. So not a big deal for me, but would appear to make guiding a challenge since many software packages will take an initial exposure to select a star and then continue imaging with this exposure while guiding.... In this case your first image wouldn't be a good representation of what to expect. Let me know when this fix gets incorporated into an updated driver and I'd be happy to test. Thanks-

Tyler

From our previous discussion:

"Hi, I have tried your VBScript and the issue does exist, we will try to fix that, for you the fastest solution is discarding the first frame after changing the exposure time, which returns much shorter than the requested duration."

yang

Hi Tyler,

Please test this version, it seems that the return time of the first frame after exposure time is changed is correct. I re-run the VBScript that you sent to me, the linear of the data is pretty good.

tylerjw98

Sam,

Works well. Thanks for making the update. Did you build this beta on top of ASCOM v1.0.1.20? If so, will this updated be part of your next release (presumably v1.0.1.21). Thanks-

Tyler