StarChaser 4

Its an IRF90 rotating focuser.

 

Colin - here is a link to a share on my Google drive.

https://drive.google.com/drive/folders/1X84epL5Uxlt506nTchw6sL1pMYSug7ii?usp=sharing

There are 2 videos and one image.
The image shows a successful calibration of the mount with the guider binned 1x1 - as previously stated, both drive and AO calibration works when the guided is binned 1x1.
Video1 - shows calibration failure when the guider is binned 2x2, 3x3 and 4x4. As I have previously reported, along with others, in these modes the calibration starts at some (seemingly fixed) point in the upper left of the sensor.
Video2 - shows the star jumping which remains a major problem. In the video, which is only a couple of minutes long, I have also captured the tracking on the mount so that you can see that the jumping is not related to a sudden deviation of the mount. Please also note that the OTA fans are turned off. You can ignore the small deviations which are of course driven by seeing. Watch carefully for the large deviations where the guide star literally jumps from the center to the edge of the sensor and seemingly always in the same direction.

Of course, I (we) still need to understand why the mount is bumping in the opposite direction.

HTH
Martin

 

That is exactly what I have been seeing. Haven't had a chance to test 7.2 yet because of weather but that is the result with prior versions and the SC3/AOX.

 

I have exactly the same observation.
For my part, I manage to calibrate the AO in bin 1 / 2 / 3 / 4, I don't calibrate the mount because I only guide with the AO, I don't send any commands to the mount (it's an L350). The automatic calibration data indicates almost similar values in X and Y.
Tracking is going well (I had guide stars with an SNR of 150, even 180). But there are guide star jumps like in your video (every minute or so). I tried lowering the aggressiveness and the max move, but it doesn't change anything. I don't think it's a hot pixel problem that could have been resolved by increasing the SNR. I give up, I think the problem is something else: an order given to the AO lens by mistake. I removed the AO from my optical train again, I stay with a classic soft guiding with an OAG (every 10s to avoid drift of the mount if the polar alignment is not optimal), or without guiding if the polar alignment is perfect. I very much regret this purchase, and I do not understand how we can sell these accessories (SC4 / AO-X) on the market at a significant price without having tested them first!!! They have never worked for anyone to date. Very disappointed.....I give up

 

I don't want to send an order to the mount but only to control the AO lens. My mount has no periodic error, so the guide star remains largely within the AO field over a 10-minute period. And in any case, even when I calibrate the mount, the guide star jump problem remains constant. I told you that the calibration of my mount is not a problem in my previous messages and the calibration of the AO has never been a problem. The guide star jump is not related to the calibration.

 

I have never had a bump problem, except in the context of a star jump, and in any case when there is a bump, there is still the jump which is not corrected. The amplitude of this jump and its suddenness is not linked to seeing or to a flexion problem

 

around 10 to 20 pixels

 

around 5,5 to 11 arc sec

 

Have you viewed the videos I uploaded for you Colin

 

For information, I have never had an indication in the AO debug when there is a similar jump

 

Colin - what progress on the calibration issue?

 

Colin....I have had the opportunity to go back and redo the test, this time with an AO log and image.

From the log you will note that I tried to calibrate the AO 3 or 4 times before it was successful. As you know, with each calibration vector, a fresh image is produced. But what happens, about half the time, is that one of those images is a tiny subframe containing just white noise and no calibration star, and because of this the calibration routine records a a near 0 X/Y location of the guide star. So it has to be repeatedly calibrated until a proper image is produced, showing the guide star, at each calibration vector, then the AO is correctly calibrated.

Process:
Mount calibrated fine, bin 1x1
AO calibrated fine (on 3rd or 4th attempt), bin 1x1
switched to bin 4x4 tracking
AO guiding performing correctly, until the large star jumps occur.
During this time I took a 5 minute image. Wander values were very low 0.05 or less. Tilt less than 6%. Very high SNR, guiding at about 13hz.
I also had the OTA fans turned off and I monitored the tracking of the mount during the 5 minute period. There were no jumps at all when the star jumping occurred.

The attached image is a central crop of that 5 minute exposure. You can see little tails off the brighter stars....this of course is camera recording those star jumps in high resolution! It does mean of course that the data is smeared and unusable.

Martin

 

Martin, just out of curiosity, do you see the guide images that are just noise frequently?

I've had this problem for years with two different STi guide cameras and the STT filter wheel with the built in guide camera which all share the same chip. I started a thread several years ago but never got the problem resolved, partially do to my just giving up on trying to get it fixed. Perhaps I should have persisted but I started having other hardware problems with my imaging setup, life got in the way such as building a house etc. I hot back into imaging more seriously a couple of years ago and I still have the problem but thankfully my mount tracks well enough that I can just live with it but it would be nice if the problem wasn't there. Since my camera is now considered "obsolete" I don't expect a fix will ever happen but it would be interesting if the same or similar thing is happening with your setup even though your hardware is much newer and makes me wonder if maybe the problem has been software all along if you are seeing something similar?

If you are curious here is the thread I started, I was not the only one that experienced this problem.

https://forum.diffractionlimited.co...causing-guiding-problems-and-star-fades.3344/

And these threads describes something similar,

https://forum.diffractionlimited.com/threads/stt-8300m-fw8g-stt-guiding-glitches.4227/

https://forum.diffractionlimited.com/threads/periodically-noisy-guider-images-with-stt-8300m.2766/