Advice needed: guiding problems

[Mr Thingy]

Hello SGL,

I'm looking for a bit of help on diagnosing a problem that's emerged recently, leading to spoilage of about 50% of my images in my last 2 sessions. The effect are stars that either have a line coming from them in specific direction, like when the mount is jolted, or they appear with a second image above each star, like it lost position for a short period before correcting. Stupidly I junked the pictures so I have no samples to share.

What is strange is that some images are absolutely fine.

I'm looking for some advice on where to start looking for a diagnosis - maybe some of you have experienced and fixed this?

Some info:

- polar aligned via a Polemaster so I'm confident it was well aligned

- I noted in the title that I have a guiding issue but I don't rule out a mechanical issue. An option I have is to try without guiding to see if the issue continues.

- HEQ5 (belt upgrade). Guiding with PHD2.

- Clear skies - no interference on guiding from clouds.

TIA

-Thingy-

[malc-c]

Shame you ditched the images as that would help the guiding gurus on the forum.  However if you could upload the PHD2 guide log files that would be useful as it will show what movements the mount made and those experienced in deciphering the logs might be able to give you some idea of what went wrong.  If you could also list the specs of the equipment used (main scope and guidescope, and cameras used) that would be useful too.

[Varavall]

1 hour ago, Mr Thingy said:

Hello SGL,

I'm looking for a bit of help on diagnosing a problem that's emerged recently, leading to spoilage of about 50% of my images in my last 2 sessions. The effect are stars that either have a line coming from them in specific direction, like when the mount is jolted, or they appear with a second image above each star, like it lost position for a short period before correcting. Stupidly I junked the pictures so I have no samples to share.

What is strange is that some images are absolutely fine.

I'm looking for some advice on where to start looking for a diagnosis - maybe some of you have experienced and fixed this?

Some info:

- polar aligned via a Polemaster so I'm confident it was well aligned

- I noted in the title that I have a guiding issue but I don't rule out a mechanical issue. An option I have is to try without guiding to see if the issue continues.

- HEQ5 (belt upgrade). Guiding with PHD2.

- Clear skies - no interference on guiding from clouds.

TIA

-Thingy-

Hi.

I have the same mount as you. Have you tuned out the backlash of the worm drives? I had a similar problem once and there were of a couple of things: 1) a cable snagging on the head of the mount RA circle locking screw; I found that by slewing the mount to stars in opposite sides of the meridian and carefully watching what was happening to the cables; and 2) a counterweight thumbscrew was grazing the declination adjuster screw head. As said above, a picture and a log is worth a thousand words!

[Mr Thingy]

Thanks for the responses. It's due to be clear tonight so I'll send some pics if it happens again.

I've attached a PHD log. Not sure if this is what's needed but was the only log I could find.

Regarding specs:

Imaging scope: Evostar 72ED + ZWO 183GT

Guide scope: Evoguide 50ED + ZWO 120 MM mini

 

cheers

PHD2_DebugLog_2022-02-25_183403.txt

[malc-c]

Thats the debug log not the guide log....

[Mr Thingy]

23 hours ago, malc-c said:

Thats the debug log not the guide log....

Doh! I'll try to figure out how to find/generate a proper log.

Strangely, the effect was absent in my session last night. Thinking about what was different, I was shooting at about 30 degrees from the horizon, whereas in the problem session I was closer to the zenith at about 70 degrees. Not sure why that would create an issue though...

Looks like another clear night tonight, so I will see if it happens in this session.

[malc-c]

Could be a balance issue, backlash issue or something else such as cable drag... posting the log files would help rule out or confirm possible causes

[AstroMuni]

23 hours ago, Mr Thingy said:

in the problem session I was closer to the zenith at about 70 degrees. Not sure why that would create an issue though...

It could be a balance issue as suggested already. I have same mount as you without belt mod and there are a few areas close to zenith where the mount struggles. Good luck finding the exact cause

[Mr Thingy]

On 28/02/2022 at 17:23, AstroMuni said:

It could be a balance issue as suggested already. I have same mount as you without belt mod and there are a few areas close to zenith where the mount struggles. Good luck finding the exact cause

I shot the same target again a couple of nights ago but rebalanced the rig a bit and all the subs were perfect. I guess it was indeed a balance issue.

I assumed balanced problems would manifest in a more regular disturbance of the tracking, rather than occasional large errors. 

Anywho, thanks to all for the guidance.