#1  
Old 16-09-2018, 11:14 AM
boz_m (Alexander)
Registered User

boz_m is offline
 
Join Date: Jun 2018
Location: Sydney, Australia
Posts: 19
Differential flexure

I have a Celestron 8” EdgeHD and I am having trouble with my guiding. In PHD2 I get pretty good results (under 1 RMS error usually) but my subs move slightly frame to frame. Eg each 1 min sub moves consistently to the left. It does t rotate just slowly moves one direction.

The problem seems to be that my guide scope locks on fine but that doesn’t exactly align to the OTA. Is this differential flexure? I have heard long FL setups and SCTs can have this issue.

My guide scope has a pretty flimsy connection to the OTA and I can easily see movement if I give it a wiggle (not loose movement as the screws are tight, just not fully secure). If this is the issue would beefing up the connection fix the issue?

I want to avoid using an OAG. I tried it but Have issues then with the correct backfocus (I posted yesterday about this), interrupts the FOV too much and harder to get guide stars. Also my Guide camera has issues with spacing to get the same focus as the OTA. So if possible want to try to keep the guide scope rig
Reply With Quote
  #2  
Old 16-09-2018, 03:42 PM
kens (Ken)
Registered User

kens is offline
 
Join Date: Oct 2014
Location: Melbourne, Australia
Posts: 314
OAG is the best option but if you want to continue to use a guide scope then you really need to tighten up everything. We're talking micrometres of movement here so you'll never see it by eye. It could even just be things sagging rather than moving.
Also make sure you've locked your mirror.
A photo of your rig might help.
Reply With Quote
  #3  
Old 16-09-2018, 04:06 PM
boz_m (Alexander)
Registered User

boz_m is offline
 
Join Date: Jun 2018
Location: Sydney, Australia
Posts: 19
Thanks ken. Yeah I just gave everything a good tighten and changed out the connection between the guide scope and the OTA for a more secure setup. Another thing that might have been an issue was the chords from the back of the guide camera so a fastened that also to the OTA so the chord is slack going to the guide camera. Will give it a whirl tonight and hopefully that has done the trick. Cheers
Reply With Quote
  #4  
Old 16-09-2018, 06:18 PM
doppler's Avatar
doppler (Rick)
Registered User

doppler is offline
 
Join Date: Nov 2012
Location: Mackay
Posts: 1,656
Hi Alexander, I am using an OAG and have the same drift in RA. In my case it's very slight and only noticeable when zoomed right in. I'm leaning towards PE, as the drift has become less noticeable since I did a belt mod to my mount and tightened the worm drive a bit. Here's a link to a discussion on the subject.

https://stargazerslounge.com/topic/2...r-drift-in-ra/
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 05:13 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement