Guiding interface: very faint star even with a maximum gain

Browndog

Hello ZWO community ! :-)
I sent a request to ZWO support but I also wanted your opinion

I had a surprising guiding problem last night.

On the ASIair's guiding interface, I could see very few stars, even at full gain (I try différent exposures too). (ie. Screen)

So I did a test by replacing the main camera with the guiding camera and with the gain at 90 I could see lots of stars... (i.e. Screen)

I tested the guidance camera alone (ASI174MM mini) and it works, I see lots of stars)

This is the first time I've had this type of issue.
Before this last update I had a normal display of stars with a gain of 90, and I didn't have any particular guidance problems so far.

A friend of mine told me that it was an ASIair bug that he'd also encountered and that I needed to reinstall the firmware, which I'm going to do this morning.

Note : just before starting my session, I got an ASIair update.
The seeing was good.

Do you know of such a bug?

My configuration:
C8 Edge HD + 0.7 reducer + OAG
Main caméra : ASI533MC pro
Guiding caméra : ASI174MM mini
Mount iOptron CEM40
ASIair last update

PMTeam@ZWO

Browndog Hello. The screens of the same camera in the preview and guiding interface are inconsistent because the histogram stretching algorithm is inconsistent. However, it will not affect the guiding function, because the histogram stretching only affects the display of the image. In fact, the guiding uses the unstretched image for star selection and guidance.

Browndog

PMTeam@ZWO Thank you for your answer.

Ok for the stretching answer.

How do you explain that I had such faint stars and especially that the guidance was so bad. (Even with the gain at around maximum) The autoguider was losing the guide star every 3 minutes, my RMS was around 1'30'' whereas normally I have a guiding between 0.40 and 0.70. Above all, I've already done this target, and I've never had this issue about guidance and really faint stars.

During this session, I tested guidance in other areas and always had very faint stars and very poor guidance.

A friend of mine had the same kind of problem one evening after an ASIair update: he could hardly see the stars via his camera and the guidance interface, and his guidance was no good. The only solution was to reset the firmware and everything was back to normal.

I added to my configuration that I was using an L-pro filter. My target was M51.

I did some test guiding around Mizar around the North Star and also pointing at the target I wanted to image, the seeing seemed good, I could see the stars well and I'm under a bortle4 sky. I'd also like to mention that I've already pointed at this target with the same setup and I hadn't had this type of issue…

w7ay

Browndog

Not saying it is your case, but inconsistent dark frames (for example, something captured with a different camera offset) can cause this. Since ZWO has never been upfront of what the changes are for each firmware update, we won't know if they have changed the offset for your guide camera. But, if you are using dark frames for guiding, it might be worth retaking the darks, just in case.

Chen

Browndog

w7ay Thank you Chen for your answer.
I've never set the offset on the ZWO cameras because I've never found where to set it...
Can you tell me where I can find this setting?

So far I've never needed to perform dark for auto guidance. I'll give it a try by activating dark.

I've also thought of another possible explanation for these faint stars:

-> I didn't check whether the guiding camera was correctly positioned in relation to the OAG prism. As the guiding camera sensor is rectangular, it may have been positioned vertically or diagonally, hiding part of the field.

I'm going to reinstall the firmware to factory settings, then download the latest updates and see if I still have this situation.

w7ay

Browndog

It is in the Guide Settings, under Guiding Advanced Settings. In the Guiding Advanced Settings window, you will find a switch for Dark Library. When you turn it on, it will create the dark frames that it needs. Takes a couple of minutes.

Since you have not turned it on, it cannot be your problem, but once you get things to work again, it may be a good thing to turn on, especially if your background is gray instead of black. Gives you a bot more dynamic range to work with.

I didn't check whether the guiding camera was correctly positioned in relation to the OAG prism. As the guiding camera sensor is rectangular, it may have been positioned vertically or diagonally, hiding part of the field.

Usually, if you orient the OAG so that the prism is on the long axis of the main camera sensor, it can be pushed closer to the optical axis without vignetting the ray bundles to the main sensor. But you have a square sensor, so you can choose any of 4 orientations :-).

Good luck.

Chen