ASI294MM Exposure Bug at 1 Second

psparky

While trying to shoot some flats with my ASI294MM, I discovered a bug in the camera at 1 second exposures. For example, while shooting my flats target at 0.5 Seconds I get and average output value of 20,400. Then setting the camera to 1 second exposure and expecting to get a value around 40,800 I get an output average of 59,156. This was using Sequence Generator Pro and the latest ZWO ASCOM driver. I also tried it with SharpCaps native driver, and ASI Studio and I get the same behavior. This graph shows the average output for exposure from 0.5-1.2. Something incorrect is definitely happening at 1 second as either the camera becomes more sensitive, or the exposure is wrong. This is with Binning set to 2X2.

I have a friend with the same camera and he has the same issue, so it it definitely an issue with the 294MM.

iddan

I am another that was shooting flats with the ASI294MM Pro at different gains with SGP the past week and confirm I saw this same weird jump in response at 1 second exposure. Bug?

Tech@ZWO

Hello

We have verified the linearity of the ASI294MM

Take example on your test data （gain 0）
0.5 5444
0.6 6288
6288-5444=824（the increase of 0.1sec）
Theoretical value of 0.8 sec =0.5+0.13= 5444+8243=7916（close to your data）

There is some few difference between 1S and 0.999sec
1S was not based on 0.5 or 0S

psparky

I don't think that you understand my graph. The response is linear and as expected from .5 sec to .95 sec. However, there is a step increase in response at 1 second. Just take exposures of the same light source from .5 to 1.5 seconds. Something is happening at 1 second. Either the camera sensitivity increases about 1 second, or the exposure time is not accurate.

iddan

@tech@zwo#43391 There is some few difference between 1S and 0.999sec
1S was not based on 0.5 or 0S

Agree with psparky that there appears to be a misunderstanding between us. I quoted tech@zwo's response to point out there is not "some few difference between 1S and 0.999sec". Instead the data shows there is a very large difference in response recorded between those two exposures. Whether a feature or a bug it would be best to know to expect that and why and that all is well. Or maybe there is a driver problem or something to be changed here? Which is it?