New autofocus algorithm

Sequence Generator Auto Focus
1

Hi,
Since the new autofocus algorithm was implemented and I unknowingly updated my SGP, it became super frustrating to use it. It fails almost every time, and I have to rerun AF multiple times until it hits that arbitrary magical 90% fit. Why can’t I adjust that number? what’s wrong with 89% and why does it fail? Can I revert back to the old algorithm without reverting whole SGP?

Moonlite focuser, Skywatcher Explorer 250PDS, SX694-Trius

These are my AF settings:
image

2

You can set the focus quality threshold, see SGP 3.1 Autofocus .

Bernd

3

I may be wrong but with an exposure time of just 2 sec’s your going to be hard pushed to get any success at all, try pushing up your exposure time to around 6 sec’s and see what you get then.

Regards
Paul

1 Like
4

Thanks. I wonder why is this nowhere in documentation (or as something editable in settings). What other magic variables exist?

5

I have duration set filter-by-filter, so what you see is unused. but 2s is enough for LRGB, always worked with older algorithm.

6

You have ‘Auto Focus with Filter’ set to ‘L’ but the box is not checked to use the ‘L’ to focus, surely this checkbox should be checked ? ? ? ?

Paul

7

Temperature compensation threshold, see 353: Temp Comp - Set Min Threshold? .

Bernd

8

There is a great tutorial in the SGP Help file regarding autofocus, specifically a formula to determine a good ballpark step size (I think yours may be too small as well as your exposure length). I followed the instructions there and have consistently achieved a good V-shaped curve and an accurate focus setting.

9

What is your V-curve looking like?

10

Try increasing your step size. I had similar troubles when the new algo was introduced and tried relaxing the quality threshold which helped a bit but in the end I doubled the step size and now get a good parabolic fit every time.

11

Yeah, I get excellent results on my SCT using 7 steps but a step size of 80 and using L primarily with an exposure of 2sec. I would think that a step size of 11 is too small for pretty much any focuser. I get it that it worked before, but you had to be on the edge and dependent more on the star quality and number in the FOV. Use a higher step size (dependent upon your focuser) and reduce the steps to 9 or 7 and you’ll get better results. Additionally, enable backlash compensation if not already done.

12

The step size seems small. I have a ML Nitecrawler and started my step size at 1500 to rough it in and after trial and error I have it down to 475.