SGP and USB_Nstep on TS Optics 80mm triplet with 2.5" R&P focuser

Sequence Generator Auto Focus
1

Hi
Does anyone use the Rigel usb_nstep focus system with a TS Optics(photoline) 80mm triplet and 2.5" R&P focuser?
I am looking for guidance with setting up the focuser in Sequence Generator Pro.
Many thanks in advance.

Gary

2

I’ve used the nstep on a couple of OTA’s. It is fairly easy to set up and configure.

The hardest part is finding the right ‘step’ size, and exposure duration required for your setup.

Also manually focus first so it is at least close to being focused before you engage the motor and start tying a focus run.

1 Like
3

Many thanks. One further question if you don’t mind? How about backlash compensation with a 2.5" R&P focuser, any tips for that? Cheers.

4

I honestly don’t bother with backlash compensation and there should not be very much in a R&P type.

If you do run into it the main thing is to make sure that it pulls inward for the final focus, against gravity as it were then just try different values for the compensation.

But at first don’t even worry about it!

Start at the in focus position and then try running the routine with different step sizes till you get a curve that resembles a V. 9 steps total 4 should be inside focus, then ‘hopefully’ the focus point, then another 4 running further out. If that makes sense.

The first ‘inside’ focus point (of 9) should be somewhere around 4 to 6 times the ‘ideal’ focus number. Your mileage may vary.

My crayfords usualy end up around 100steps per point give or take some.

1 Like
5

R&P focusers always have backlash. This has to be compensated. The backlash of your focuser should be determined and the backlash correction has to be set up (Control Panel/Focus/Other: direction IN, Compensation step size: the determined value + a little extra).

You can try without backlash compensation first. If you experience that your “V-curves” don’t look as they should at their right limb, you have a strong indication of backlash that has to be compensated.

Bernd

1 Like
6

Thanks again, greatly appreciated.

7

Cheers, just waiting for my power box for the dovetail bar and I’ll dive into it. Feeling pretty confident now.