ICEINSPACE
Most Read Articles
Moon Phase
CURRENT MOON Waxing Crescent
39%
The Sun Now
Time Zones
Sydney*
1:09 am
Perth
10:09 pm
Auckland*
3:09 am
New York*
10:09 am
Paris*
4:09 pm
GMT
2:09 pm




Go Back   IceInSpace > Beginners Start Here > Beginners Equipment Discussions

Reply
 
Thread Tools Rate Thread
  #1  
Old 13-09-2018, 09:26 PM
Cimitar (Evan)
Evan Morris

Cimitar is offline
 
Join Date: Dec 2006
Location: Gunnedah, NSW
Posts: 235
DEC calibration issue with OAG guiding

Evening folks,

I'm having a bit of trouble with a DEC guiding issue on my Meade LX200 ACF 8" when using an OAG.
For the past couple of years I've been successfully using an Orion SSAG and guidescope. This has worked well, however, I thought I'd make the move to OAG due to my longer focal length and SCT.

My specific problem is I can't seem to get PHD to calibrate because it won't move the mount sufficiently in DEC axis. RA movement appears to be fine.
PHD calculates the calibration step at 200. This number appears to be fine for RA because it completes that part, however, when it attempts to move North/South the star barely moves. I'm using an Orion TOAG and ZWO ASI174MM. Everything is focused properly and the balance is good. I tried clearing the backlash, adjusting the guide rate setting etc. sadly to no avail.

When I switch back to the guide scope, the mount is fine and PHD happily guides in RA/DEC.
This makes me think it's a user issue with the software. Perhaps I'm missing a specific setting somewhere in PHD?

Cheers, Evan

Last edited by Cimitar; 14-09-2018 at 09:04 AM. Reason: Updated for clarity purposes. I wrote the OP when I was rather frustrated!
Reply With Quote
  #2  
Old 13-09-2018, 11:15 PM
Cimitar (Evan)
Evan Morris

Cimitar is offline
 
Join Date: Dec 2006
Location: Gunnedah, NSW
Posts: 235
I had another look at PHD and the calculated calibration step size is set at 200. I manually increased this to 500 (as a guess) and the mount successfully moved North/South.
The calibration succeeded, however, what I'm not sure of is why the mount can readily move in RA (with a step size of 200) but not in DEC?
My first thought is backlash in the DEC axis, but then why wouldn't this affect the guide scope?

Last edited by Cimitar; 14-09-2018 at 09:05 AM. Reason: Updated info and to correct spelling.
Reply With Quote
  #3  
Old 19-09-2018, 10:03 PM
Cimitar (Evan)
Evan Morris

Cimitar is offline
 
Join Date: Dec 2006
Location: Gunnedah, NSW
Posts: 235
Just wanted to share the solution to my 8" Meade LX200 DEC guiding issues with the OAG, in case it's useful to someone else in the future:

1. The scope was ever so slightly out of balance in DEC, with a tendency for the corrector plate to drift to the South. I corrected this, and made it so the scope (corrector plate end) was ever so slightly imbalanced towards the North.
2. I disabled all anti-backlash settings in the hand controller (RA & DEC). I did this by setting the percentages to 0%
3. I enabled the DEC backlash option in the PHD2 guide settings.
4. I still wasn't happy with the recommended 200 calibration step size, so I manually entered 400. This worked fine.

The mount happily moved in RA & DEC, and after a bit of fiddling with the guide settings I was able to achieve the attached guiding graph. Pretty happy with the star plot as well.
Still a bit of movement in RA that I need to sort out, however, I shot a 600sec ISO800 exposure on the Eagle Nebula (Canon 600D DSLR) and the stars look alright

The only thing I wasn't sure of was my Tot RMS error. It seems a tad high. However, I was using a guide scope previously and the RMS error there was always below 1.
I wonder if the image scale might have changed due to the OAG though? If it has, it might be distorting the figures?

Cheers, Evan
Attached Thumbnails
Click for full-size image (Guiding.jpg)
161.5 KB10 views
Click for full-size image (600sec_ISO800.jpg)
162.3 KB8 views

Last edited by Cimitar; 19-09-2018 at 10:24 PM.
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 12:09 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Advertisement
SkyWatcher 2018 Catalogue
Advertisement
Lunatico Astronomical
Advertisement
SkyWatcher WiFi Adaptor
Advertisement
Bintel
Advertisement
NexDome Observatories
Advertisement
Interest Free Finance
Advertisement
Atik Horizon
Advertisement
OzScopes Authorised Dealer
Advertisement
FLI Cameras and Imaging Accessories
Advertisement
Astronomy and Electronics Centre
Advertisement