Unguided Periodic Error with SW SA gti? - Forums

Topic starter

Oct 31, 2022

My initial test reveals significant periodic movement in RA direction. I see a period of about 7 minutes. Is this the worm period? I had to reduce the exposure to 30 seconds to make stars less elongated. That led to 540 subs and a very long time to stack. Do all GTIs have this problem? Are there any things to do to get rid of this?

I will use guiding and guess the problem will be solved by that.

Hint: To test, go quickly through your subs at largest zoom and watch star movement and elongation.

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Paulito99

Oct 31, 2022

I have noticed this also,. can manage up to 40sec unguided,. also the Goto is quite a bit out,. i thought it might be polar alignment but last nights was pretty spot on,. also going to go guided soon but was looking forward to longer subs,. going to retest with a bang on polar nexct opportunity,.

Gustav Lundby

Topic starter

Oct 31, 2022

I had close to perfect PA using Kstars Ekos PA with plate solve against southern part of sky. DEC had no drift and I had no rotation during 6 hour. The variation was only in RA and clearly periodic. Since there is no PEC possibility in this mount, if no tuning kit with new worm, then guiding must be the solution.

Paulito99

Oct 31, 2022

Probably too early for a tuning kit however it would not surprise me if the same internals as star adventurer 2i maybe,. Anyway guiding probably best solution,. Agree

David Quattlebaum

Feb 5, 2023

Gustav Lundby:
I had close to perfect PA using Kstars Ekos PA

Curious, I am also using Kstars/Ekos Are you using the Skywatcher EQ GTI Wifi adapter? I started by trying to use the EQMod connection over hand controller serial port, but the signals being sent to the mount were doing crazy things. The Wifi option is not ideal for me as I would like to control my laptop remotely over the Wifi, but that adapter for sure worked well.

This was my test, first out with the mount: https://www.astrobin.com/50wjc3/

Gustav Lundby

Topic starter

Feb 5, 2023

I gave up my SW SA gti, but I used it from Kstars-Ekos-INDI using USB cable. It came without hand controller, so I plugged into its USB connector. I had to configure the USB as Serial in the Windows app and I tweaked the settings for timeout and retries to the double to get rid of errors in INDI.

I'm now using IOptron Sky Hunter in stead. Not good either. Total RMS about 5" guided. But in this case the error is not periodic and I hope to be able to tune it to behave better (backlash?)

TiffsAndAstro

May 1, 2024

Just for context my stock gti does about 0.2(1.4) auto guiding but can also see a big periodic error. Stars look round with longer exposures so im ok with it i guess.