4 replies to this topic

[Yomamma]

I just got my WD20 mount and I am very pleased with it's performance so far but it seems no matter what telescope setup I put on the mount PHD2 guide assistant will always recommend backlash compensation on DEC.

 

I was under the impression that backlash in this unit should be very low, but when I mount my Esprit 100 with OAG and camera(about 23 pounds) I consistently get backlash recommendations of >300ms.  When I mount my Meade 8" SCT with OAG and camera(about 20 pounds), I consistently get backlash recommendations of > 700ms.

 

There are no dangling cables and everything is zipped tight against the telescopes so they are a compact unit with nothing sticking out.

 

I apply the recommendations and my guiding is pretty good.  I run 1/2 second guide subs and high gain with a ASI174mm mini.

 

I have contacted Warp Aston and they gave me the dragging cables/etc..speil but I told them I would do some more testing and get back.

 

Have any other WD20 owners gotten similar results from PHD2 guide assistant?  If not, what do you get?

 

Thanks

[Arcueid]

WD20 user here. Haven't run Guide Assistant before and been using 0.5 sec exposure time. Since I usually get RMS of 0.2 or 0.3ish it seems fine, can't measure it now as the sky is covered with clouds.

[dx_ron]

PHD Guide Assistant backlash measurement is often flaky. The better measure is to look at the actual amount of backlash compensation PHD is using after a few hours of guiding (it adjusts based on how the mount reacts).

[ForeverNewbie]

PHD guiding assistant gives weird results for strainwave drives. My AM5 (and many others) gives very erratic results, up to 8000 msec with the advice to skip dec guiding!.Nevertheless, guiding is very acceptable when I ignore the advice, usually between 0.5 and 0.8 arcsec.

[dswtan]

Interesting to hear about the Guiding Assistant (GA) issues with Strainwaves. I've been getting 0.5-0.6" at best on my WD-20, but using the GA diligently (my past indoctrination). If ~0.2-0.3 is possible, I'm going to try a more direct approach!

 

I'm not sure how to report what backlash comp settings I'm getting, per OP. PHD sets it differently for each session and I'm not sure where the original GA data is (I looked). In runs, I'm seeing anything from 42ms to 156ms or similar.

 

BTW, I see Chris Woodhouse's manual (15 Feb 2025 version, p28) is recommending the following, which I'm now going to try!

 

• 50-mm guide scope or better (200mm focal length)

• CMOS guide camera, USB3/C with small pixels ~2.5 μ 

• PHD2 settings - single star, subframe on, 0.5 second exposure, pulse-guide (rather than ST4) 

• RA algorithm set to PPEC, 80/75 predictive/reactive weight, minimum move set to 0.02, period 359 sec-onds, auto adjust enabled 

• DEC algorithm set to Z-filter, factor 8, min move 0.05 pixels

• Enable reverse DEC after meridian flip

 

Update: I switched from 1sec to 0.5sec tonight for the first time, and I'm now getting ~0.4" without changing anything else. Nice!

Edited by dswtan, 19 March 2025 - 01:10 AM.