ASI 1600MM Cool won't capture images

This is an odd one. My ASI1600 suddenly won’t capture images (darks, bias) using SGP. It works normally with ASICAP and SharpCap on all gains, offsets and exposure lengths. I have captured hundreds of images with the camera/SGP before. The really odd thing is that the frame is captured, sort of, but is is blank. There is no pedestal and all image statistics reads 0, except minimum which reads 65536. And that does not make any sense. If I shift the USB cable over to my ASI294 it takes “normal” images with SGP.
I hope there is a simple solution, but I can’t see it.
I also downloaded and installed the latest prod version, just to be sure.

Im having the same issue. I noticed it last weekend when I tried to capture an image and it came up blank. I disconnected the camera in SGP, reconnected and it was fine. Then it happened again during an auto focus run. Yesterday I was taking darks indoors (5 min darks) and after 34 images, the rest were all blank images. There’s an image saved but it is completely black, no data.
Power is good at 13.8V DC, good cable (different one than was used the first time it happened) and nothing else is connected or happening on the computer. In using the ZWO native driver.
I’m trying again with NINA to see if it happens there as well.

Please use the ZWO ASCOM driver instead.

OK, I have changed all my sequences to use the Ascom driver for both ASI1600 and ASI294. I have used this driver before, but I encountered some problems. It is so long ago that I don’t remember what it was. If still there it will probably show.

I think the only reason I haven’t used the ASCOM driver is that it doesn’t allow me to set the offset manually; doesn’t have as much adjust-ability…I think. I’ll look at it again.

You shouldn’t need to adjust the offset dynamically right? This is the opinion of the ASCOM platform team anyhow. Offset is a parameter that should be handled dynamically within the camera’s internal software.

Either way, we will likely end support for ASI native drivers soon.

That’s disappointing but I agree that stability should come first.

I had a similar issue the other night with version 405. I was shooting darks and it stopped downloading images (ZWO ASI183MM with Native driver). I restarted SGP and it finished running the sequence.

I can live with not changing offsets but with CMOS cameras it’s pretty important to be able to set gain on a per event basis. Many imagers, including me, use higher gain for narrowband imaging and lower gain for LRGB on the same target. If gain can only be set in the equipment tab it’s going to be a big step backwards.



It’s only 2 versions behind the latest Native SDK, since 2016, I would still recommend to schedule the SDK implementation.

Not sure I understand this. There is no difference in how the native driver or ASCOM driver sets gain. What do you mean by “backwards” here?

Sure, this is generally agreed upon… that said, it seems like what you are saying is not really “per-event”, but “per-filter”. These cameras are pretty new and I am trying to resolve when one would want to modify gain. The problem with “event” level variation is that there is no correlation to an event in an equipment profile… looking for permutations of an imaging train that can define a specific gain.

Ken, This is the problem with the Ascom driver:
You can set the gain for a specific event, but not the Offset value.
Normally doing LRGB you might use unity gain/offset, but moving to narrowband like Ha and OIII you can not change the Offset, only the gain. This is simply said not acceptable. It can be changed using the native driver though.
If you plan to leave the native driver, this is something you need to fix somehow.


Whether or not this is something that needs dynamic behavior, I don’t agree that this is something SGPro is responsible for or something that we “need” to fix. The ASCOM team has very strong opinions on values they expose and, after some conversation with Bob Denny, it is clear that this is not something they intend on supporting because this behavior should not be pushed onto consumers or the the software that controls cameras. In my opinion, viable paths forward are:

  • Convince ASCOM that offset is required to change based on properties of your imaging train. In this case, because we support ASCOM, we will implement this in SGPro.
  • Convince ZWO that offset should be handled dynamically within their hardware / software.

OK, that’s your stance, but all problems experienced during imaging do not implicitly fall in the lap of SGPro to fix.

We won’t remove native support for ZWO cameras, but we will likely not support them if they are unstable or act a little wacky.

I find this very strange because in the driver setup screen the gain/offset is fully configurable. You can select any combination of gain and offset you prefer. And that is how it should be for CMOS cameras.
But it cannot be done in the pre event settings. Why is that?

Because ASCOM does not expose the Offset for the camera. When using the ASCOM driver we have to abide by the ASCOM specification. And we can’t set something if it’s not exposed. Here’s the standard:

You’ll notice there is no Offset property. But Gain does exist.

The ASCOM Camera Setup dialog allows you to set other things if you choose. But SGP can’t access them.


I don’t use CMOS. In understand you would want to change Gain but I’m less sure why changing offset is that important. A good amount of feedback over at Cloudinights seemed to suggest that offset 40 of 50 worked with different gains (for broadband and narrowband). Thanks

This is perhaps a better discussion for ASCOM forum than here (or with camera manufacturer/author of the ASCOM driver). I wonder if it is the camera ASCOM driver that doesn’t expose the offset, or if it is the ASCOM interface that doesn’t pass it along?

I’m not so familiar with ASI but reading the QHY document (I have a QHY128C) “Setting GAIN and OFFSET on cold CMOS camera”, it seems to imply that the end user needs to determine the best offset: “There is no such thing as the best value for OFFSET. This is how you should set the OFFSET value: Take the bias frame and dark frame at a certain GAIN value, then study the histogram of the frames …”.

Maybe other camera manufacturers intend to handle offset differently (ie. let driver determine offset based on the chosen gain?). I tried finding some discussion on this in the ASCOM forum but no luck. On the face of it, seems to me like a disconnect between the camera manufacturer and ASCOM (ie. who sets offset - end user or driver/automatic)? Maybe I’ll try reaching out to QHY.


The ASCOM interface does not expose it. Please see above.

This tends to vary by camera manufacturer. For instance SBIG doesn’t allow you to set the gain or the offset of their cameras as they are set from the factory at specific values. With DSLR you can set the gain (ISO) but have no control over the offset.


The trends is somehow disappointing. Since both QHY and ZWO are encouraging software developers implement their SDK than using ASCOM drivers, and famous softwares are going to support their Native Drivers, there’s still my requirement about further support and regular update for native SDK or drivers.

Due to economic choice, the users for both cameras are large, if the camera support is bad, may lose some potential users and they are aiming for alternative choice.

I may suggest again with future SDK upgrades in SGP @Ken.



Perhaps it was my incorrect understanding that with the ASCOM driver you could only change the gain in the camera equipment tab, not in the sequencer. From the screenshots in this thread, it appears that it is possible to select different gain in a given target for each filter/event. I can live without setting offset per event and fixing it according to the camera driver. Dynamic range changes very little because of that. All I need to do is reshoot the dark library.



The offset is not about dynamic range. It is about preventing pixels clipping to black because of noise.
Using the ASI1600 as example, at gain 0 you use offset 10, at unity gain you use offset 21 and at gain 200 and over you use offset 50, all not to clip pixels to black.
Most users use unity gain or lower to shoot LRGB, but as soon as NB filters are in the chain you might want a higher gain/offset combination.
But with the Ascom driver you can not change the offset for an event within a sequence. You can’t have LRGB and NB in the same sequence unless they use the same gain. And you don’t wont to use different gain unless you can change the offset correspondingly.
I would not mind if the offset was dynamically set in the camera and we would not have to think about it. But until it is, we need the possibility to set both gain and offset pr event.

To adjust this statement a bit: A higher offset will reduce the dynamic range, but that is not why it is used. That is a consequence of the higher offset.