Teetering..

[david_taurus83]

The last few nights out now I get these random hiccups with guiding. All was going great last night with average guiding at around 0.6" RMS until I performed a meridian flip. After the flip and 3 or 4 frames into the next filter the RA went off the chart. It recovered and was fine again for a minute and then went off the chart again. My cure was to pause imaging, stop guiding and go outside and slide the counterweight further down the shaft. Scope was pointing up high at M45. For a while now I've had to offset the balance as if I set it right I get funny calibration results in PHD. When I first got the mount all the tolerances were bang on and everything was fine but after 6 months or so of use I noticed these issues creeping in. Do the drive belts, gears, worm etc need a little adjusting? Any way to check the tolerances?

[fireballxl5]

here in the NW it was quite breezy and my guiding was affected for a long period. It settled down around midnight and was fine after this. Maybe you had similar problems?

maybe I didn't get enough sleep - the symptoms clearly don't fit with this cause, doh!

[Craney]

Is there not a technique for balancing the mount where you make the rig slighty  'East Heavy' and 'something else heavy' so that the mount motors  are continually pushing the scope and not allowing a free-wheeling unweighted glide to occur......   just a guess ???

[Thalestris24]

33 minutes ago, david_taurus83 said:

The last few nights out now I get these random hiccups with guiding. All was going great last night with average guiding at around 0.6" RMS until I performed a meridian flip. After the flip and 3 or 4 frames into the next filter the RA went off the chart. It recovered and was fine again for a minute and then went off the chart again. My cure was to pause imaging, stop guiding and go outside and slide the counterweight further down the shaft. Scope was pointing up high at M45. For a while now I've had to offset the balance as if I set it right I get funny calibration results in PHD. When I first got the mount all the tolerances were bang on and everything was fine but after 6 months or so of use I noticed these issues creeping in. Do the drive belts, gears, worm etc need a little adjusting? Any way to check the tolerances?

There is a meridian flip calibration tool in PHD2 which you can run if you expect to be doing a meridian flip. Also it may be that your setup is unbalanced after doing the flip. Maybe run the guiding assistant on the flip side. Otherwise maybe an eqmod setting?

Hth

Louise

[david_taurus83]

You know, I'm really not sure if it's backlash, wide tolerance in the mount. I've caught PHD doing funny things. For example, last night it was guiding fine and all of a sudden it said star lost and started blinking. The funny thing was the preview in PHD had moved and the box around the star stayed in the same place where the star was but with no star! I had to stop and loop again and the preview was back to where it was in the first place. It's not the first time it's done that.

[Thalestris24]

19 minutes ago, david_taurus83 said:

You know, I'm really not sure if it's backlash, wide tolerance in the mount. I've caught PHD doing funny things. For example, last night it was guiding fine and all of a sudden it said star lost and started blinking. The funny thing was the preview in PHD had moved and the box around the star stayed in the same place where the star was but with no star! I had to stop and loop again and the preview was back to where it was in the first place. It's not the first time it's done that.

That can certainly happen with a low snr star and/or (thin) clouds passing over

Louise

[david_taurus83]

15 minutes ago, Thalestris24 said:

That can certainly happen with a low snr star and/or (thin) clouds passing over

Louise

That is possible but I always pick a good signal star and 4 second exposures. Even with high cloud it can see through it. It doesn't explain why the preview screen shifts. I will have to try and take a picture of before and after to try and explain.

[Jkulin]

2 hours ago, Thalestris24 said:

There is a meridian flip calibration tool in PHD2 which you can run if you expect to be doing a meridian flip

Hi Louise, that's the first I have heard of that, where do you find that?

[Thalestris24]

11 minutes ago, Jkulin said:

Hi Louise, that's the first I have heard of that, where do you find that?

In 'Tools'  

[Thalestris24]

47 minutes ago, david_taurus83 said:

That is possible but I always pick a good signal star and 4 second exposures. Even with high cloud it can see through it. It doesn't explain why the preview screen shifts. I will have to try and take a picture of before and after to try and explain.

Hmm… Maybe it's something to do with the mount? Sometimes mounts continue to move for a short time after you think they've arrived at a spot. When does it happen - only after meridian flips? Looking at your screen grab it seems the mount has moved just out of range of the guide star. You could always just try changing the search distance in guiding -> search pixels, though that's just a fix really. Is there any unexpected RA drift if you run guiding assistant before or after a flip? Is the az-eq6 belt driven? If so, it shouldn't need 'east-heavy balancing' or anything - just good dynamic balance on both sides of the meridian.

Louise

[david_taurus83]

6 minutes ago, Thalestris24 said:

Hmm… Maybe it's something to do with the mount? Sometimes mounts continue to move for a short time after you think they've arrived at a spot. When does it happen - only after meridian flips? Looking at your screen grab it seems the mount has moved just out of range of the guide star. You could always just try changing the search distance in guiding -> search pixels, though that's just a fix really. Is there any unexpected RA drift if you run guiding assistant before or after a flip? Is the az-eq6 belt driven? If so, it shouldn't need 'east-heavy balancing' or anything - just good dynamic balance on both sides of the meridian.

Louise

No, not necessarily after a flip. I first noticed it at a Star party last month. I had just started imaging and it happened. There's 2 separate issues here I'm talking about. The PHD issue is when it looses the star because the preview changes. That happened at the star party and both RA and Dec go off the chart. I think thats definitely a software issue. I might do a fresh install to clear any dud setting that might cause it.

 

The second issue is to do with the screenshot above. It was guiding fine as you can see by the flat graph. It generally guides very well, I don't get the saw tooth effect. But I watched as the star shifted dramatically over 2 exposures to either right and left side of the crosshair. It moved a lot faster than it would if I simply stopped tracking. Though as I said, the fix was to go outside and offset the counterweight a bit more. So possibly excessive play in the mount but due to the issue described above I can't rule out PHD. I'm on 2.6.5 and I think thats the latest version as well.

[Thalestris24]

2 minutes ago, david_taurus83 said:

No, not necessarily after a flip. I first noticed it at a Star party last month. I had just started imaging and it happened. There's 2 separate issues here I'm talking about. The PHD issue is when it looses the star because the preview changes. That happened at the star party and both RA and Dec go off the chart. I think thats definitely a software issue. I might do a fresh install to clear any dud setting that might cause it.

 

The second issue is to do with the screenshot above. It was guiding fine as you can see by the flat graph. It generally guides very well, I don't get the saw tooth effect. But I watched as the star shifted dramatically over 2 exposures to either right and left side of the crosshair. It moved a lot faster than it would if I simply stopped tracking. Though as I said, the fix was to go outside and offset the counterweight a bit more. So possibly excessive play in the mount but due to the issue described above I can't rule out PHD. I'm on 2.6.5 and I think thats the latest version as well.

My first thought would probably be cable snagging or wind gust. Second thought would be interrupted data via usb i.e. connection or cable probs. 

Louise

[Jkulin]

39 minutes ago, Thalestris24 said:

In 'Tools'  

Sorry Louise but there's nothing in my version of PHD2 about Meridian flip unless I am missing something: -

[david_taurus83]

2 minutes ago, Thalestris24 said:

My first thought would probably be cable snagging or wind gust. Second thought would be interrupted data via usb i.e. connection or cable probs. 

Louise

I checked for cable snag and no sign. I've started routing all cables now down through the mount as there's room with an AZEQ6 to route by the polar scope.

 

Also, I've had the same issue with a Startech USB hub with my Canon, same issue with USB repeater cables and last night to rule the above out, I left the laptop by the scope in a plastic box with direct connection and still the same issues.

[Thalestris24]

1 minute ago, Jkulin said:

Sorry Louise but there's nothing in my version of PHD2 about Meridian flip unless I am missing something: -

Ah,sorry, you need the development version

[david_taurus83]

8 minutes ago, Thalestris24 said:

Ah,sorry, you need the development version

Is this free to download for all? Stable?

 

Edit: Found it. Will give dev6 a twirl?

[Thalestris24]

2 minutes ago, david_taurus83 said:

Is this free to download for all? Stable?

Of course. I think it's ok - I've not had any problems with it. I doubt it'll solve your issue though.

Louise