Autofocus fails with Sesto Senso


I have having issues with achieving auto focus with SGPro and Sesto Senso.

If anyone else have a similar setup I would love to know what settings you have chosen to make it work.

My equipment;

Telescope - SW Esprit 80
Focuser - Sesto Senso 2
Filters - Astrodon LRGB and Ha OIII SII
Camera - QSI 683

Im grateful for any help :slight_smile:

since I don’t know how much experience you’ve had with this setup, I would like to pose a few basic questions.

Have you used this setup successfully before?
Did you change anything lately?
Have you tried to calibrate the focuser again?

I have similar setup and when I have focusing issues, it’s usually one of the following:

There’s a cable obstructing the Crayford tube or R&P or the lock screw has been tightened.
The mounting clamp is too tight, or I’ve not used the three additional screws to attach the clamp to the scope.
I’ve not focused the stars enough before starting the auto focus routine.
Depending on which filter you’re using you may want to increase the exposure time.
Lately I’ve not had much luck with the ASTAP focusing function, so I’ve reverted to the HFR method. Seems to be more reliable.
The Sesto Senso 2, when using high movement speeds, can introduce “slippage” even when the axis connection is as tight as possible. According to Prima Luce you need to slow the movements down. My camera is light and I have a rack & pinion focuser and I still get slippage when the movement speed is too high, so I’ve set mine to Heavy and Slow and that seem to have solved that issue.

Hope some of this helps.


Hello Allen,

Thank you so much for the feedback.
To answer your questions.
1 and 2. This is a completely new setup
3. Yes I recalibrated the focuser before starting.

When I have clear skies again I will configure Sesto Senso to heavy and slow.How about the startup seed and run ? do you set it as low as 1?
DO you compensate for this slippage in SGP? What are your numbers?

Kind regards

Hi Roger,
what you can do to home in on the parameters for the Sesto, is to work with the Sesto Senso Focus Manager software. Connect the focuser in the software, choose a setting and run the focuser out and in a few times. After a few times, set the focuser to position 0 and have a look at the physical position of your focuser tube…
If your settings are to aggressive for focuser, your tube might not be physically at the 0 position although the software thinks it is… Play around with the settings until the software 0 equals the physical 0 position.

The next thing I did was to use the SGP focusing, on a clear night, to home into the best focus I can get and then start the Autoofocus function and watch the resulting graph. Adjust the number of steps, I’ve found 7 or 9 to be usefull and the step size and then rerun the autofcus… My experience has been, that if the grapgh shows a “dog ear” on the left side, then my step size is too big. The step size and the number of steps should be large enough for the focus to change noticably, but not so large that the stars go totally out of focus.

If you’re still having issues after this, I would suggest you link the log file, so that more knowledgeable members can have a look at that, to see what’s going on.

Best of luck and CS,

Hi Allan,

Thank you for the help. I did as you suggested and its pretty much in focus now :slight_smile:
Took my first test shot too and it looks very good.

Thank you :slight_smile:

Glad I could help. Have fun and clear skies.

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