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Guiding after meridian flip (new setup)

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#1 whirlpoolm51

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Posted 25 June 2022 - 12:00 PM

I have finally got everything running pretty smooth with the new scope!! I have had a couple of nights to do some imaging, and in doing so i have noticed but guiding error on RA almost doubles after a meridian flip.

Before the flip error is roughly 0.35 to 0.4 and after its 0.58 to 0.60.

 

The highest spikes in RA after the flip though have a noticeable effect on the stars, even though I only lost about 4 subs i still know there is in issue and it's for sure not seeing related

 

This didn't happen on my old setup with the 12" rc truss. I have re did all my models and pec training per software bisque when mounting a new setup and all that lines up with recent runs, so I know I did that right Haha

 

Right now, I'm running the ME2 with a 14.5" ago idk and guiding with a zwo 174mm ( binnned 2x2) and a zwo XL OAG.

Here are the logs from last night. i downloaded the log viewer but i figured i would see what you guys thought.

 

My guess is, it's a balancing issue or gear mesh

 

https://1drv.ms/t/s!...SjDxtg?e=0xY5kg

 

https://1drv.ms/t/s!...oeDLyw?e=ecmyzq

 

Pretty sure the larger file is the one after the flip, I'm not sure as I tried stopping guiding and changing a few things a couple times to see if that helped to no avail.


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#2 DirtyRod

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Posted 25 June 2022 - 12:22 PM

In my experience it's balance and sometimes 3rd axis balance. Both my CGEM2 and CGX-L were always bad pointed South or West until I got a dovetail weight kit and balanced the 3rd axis. Before balancing the 3rd axis my guiding was always worse before the flip.  

 

Do you run East Heavy? If so, are you re-adjusting after the flip?


Edited by DirtyRod, 25 June 2022 - 12:24 PM.


#3 whirlpoolm51

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Posted 25 June 2022 - 12:31 PM

Yes I run east heavy and I thought hey maybe I should try shifting the weight down a little after the flip , but I honestly never had to do that with the 12”
I did go out and try shifting one of my weights down a bit after flip but without unlocking the clutches I didn’t really know how far to go.

I have Dec slightly imbalanced also , and I’m also using one of those losmandy dovetail weights setups , but I used it at the back of the scope to help balance Dec.

I’ve read about using a weight on a string that will cause slight imbalance so you don’t have to move the weight after every flip but that seems like it would cause more problems then help haha
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#4 whirlpoolm51

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Posted 25 June 2022 - 12:34 PM

I also find it funny that right below my guiding issue post is the Richard wright “ guiding needs to die” post hahaha
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#5 kathyastro

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Posted 25 June 2022 - 12:50 PM

The problem is backlash, so anything you can do to reduce backlash will help.

 

I no longer balance east-heavy because my CEM-60 requires perfect balance.  But back in the day, with my HEQ5, I would first balance it perfectly (as near as I could tell), then move the counterweight half an inch outward to make it east heavy for the eastern half of the sky.  At the flip, I would move the counterweight inward one inch: half an inch to remove the original bias, and another half inch to make it east-heavy again for the western half of the sky.


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#6 whirlpoolm51

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Posted 25 June 2022 - 01:00 PM

I figured it was a combo of the two , SB recommends you adjust the spring plungers ( gear mesh) every time you switch setups , I might not have adjusted them enough for the weight increase even thought it’s a 220Lb capacity mount with only around 90 on it haha

#7 PirateMike

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Posted 25 June 2022 - 01:13 PM

Yes I run east heavy and I thought hey maybe I should try shifting the weight down a little after the flip

 

 At the flip, I would move the counterweight inward one inch

Kathy has got it right... The weights should be moved up (not down) towards the head after a flip... if they are to be moved at all.

 

 

Miguel   8-)

 

 

.


Edited by PirateMike, 25 June 2022 - 01:15 PM.


#8 whirlpoolm51

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Posted 25 June 2022 - 01:32 PM

My bad that’s what I was saying scope heavy all the time

#9 DirtyRod

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Posted 25 June 2022 - 01:32 PM

, I would first balance it perfectly (as near as I could tell), then move the counterweight half an inch outward to make it east heavy for the eastern half of the sky.  At the flip, I would move the counterweight inward one inch: half an inch to remove the original bias, and another half inch to make it east-heavy again for the western half of the sky.

Pretty much with I do for my CGX-L when it’s facing East or South. When it’s facing North it doesn’t need it. My CGEM2 prefers neutral with my light RedCat on it but guides better east heavy with my SCT.

 

One day someone will come up with counterweights that can be adjusted through automation.



#10 whirlpoolm51

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Posted 25 June 2022 - 01:36 PM

There has got to be a better way to do it. Maybe like a sliding weight you can adjust so when the flip happens it slides by itself to the correct spot

#11 Ken Sturrock

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Posted 25 June 2022 - 01:42 PM

I admit that I'm having a bit of trouble following this.

 

You have two log files from PHD.

 

PHD2_GuideLog_2022-06-23_212652

PHD2_GuideLog_2022-06-24_210754

 

and they are from two different days, so conditions are potentially different.

 

Now, looking at those files (in chronological order as above):

 

52.png

 

54.png

 

I fully admit that I'm not a PHD guy, so I get a bit lost and I'm sticking my neck out, here.

 

I see the spikes caused by dithering (right?) usually more prominent in Dec than RA. I can also eyeball the RMS statistics (not shown above) which for Log #52 show RA: 0.26, Dec: 0.27, total: 0.38 - which are nicely matched between the axes. For the second log, #54 - a different day, I see RA: 0.23, Dec: 0.23, total: 0.33. Again, Log #54 is pretty well balanced. How did you derive your stated RMS values?

 

I just don't see a lot of difference between the log files - aside from the timing and sizes of the dithers. Moreover, I don't see anything particularly different between axes - again, aside from the dithers. Finally, I don't see anything that stands out as matching the ME2's 2:29 worm period. To my eye, there's no real smoking gun - just dithering and random noise.

 

When do you think the flip occurred in the above logs? What was the target? Was it near the pole? Can you, on the same night, collect a guiding log from the east, then flip the mount and do the same from the west at the same declination and approximately mirrored hour angles (say, an hour angle before and after meridian?)

 

It may be worth adjusting the worm mesh but it's rare for Paramounts to need any sort of "weighting" to compensate for backlash. Just good balancing - especially with a bigger OTA like yours. Before you adjust anything, though, have you started a thread on the Bisque forum? They will want to see tracking logs (probably more useful for diagnosing a mount issue because they don't have the extra confounder of guider corrections) collected from within the SkyX, versus PHD. You should probably step through the entire Imaging System Analysis algorithm.

 

Sorry, that's all I've got.



#12 PirateMike

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Posted 25 June 2022 - 01:45 PM

Here's another way to do it, even though it still requires manual help. I use to do this and it worked quite good.

 

 

1. Set the scope up east heavy while the scope is on the east side and pointing west.

2. Move the scope to the west side pointing east and add magnets to the weights until east heavy once again.

3. Start your imaging run and after the flip remove the magnets.

 

 

Miguel   8-)

 

.



#13 whirlpoolm51

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Posted 25 June 2022 - 01:59 PM

I admit that I'm having a bit of trouble following this.

 

You have two log files from PHD.

 

PHD2_GuideLog_2022-06-23_212652

PHD2_GuideLog_2022-06-24_210754

 

and they are from two different days, so conditions are potentially different.

 

Now, looking at those files (in chronological order as above):

 

attachicon.gif52.png

 

attachicon.gif54.png

 

I fully admit that I'm not a PHD guy, so I get a bit lost and I'm sticking my neck out, here.

 

I see the spikes caused by dithering (right?) usually more prominent in Dec than RA. I can also eyeball the RMS statistics (not shown above) which for Log #52 show RA: 0.26, Dec: 0.27, total: 0.38 - which are nicely matched between the axes. For the second log, #54 - a different day, I see RA: 0.23, Dec: 0.23, total: 0.33. Again, Log #54 is pretty well balanced. How did you derive your stated RMS values?

 

I just don't see a lot of difference between the log files - aside from the timing and sizes of the dithers. Moreover, I don't see anything particularly different between axes - again, aside from the dithers. Finally, I don't see anything that stands out as matching the ME2's 2:29 worm period. To my eye, there's no real smoking gun - just dithering and random noise.

 

When do you think the flip occurred in the above logs? What was the target? Was it near the pole? Can you, on the same night, collect a guiding log from the east, then flip the mount and do the same from the west at the same declination and approximately mirrored hour angles (say, an hour angle before and after meridian?)

 

It may be worth adjusting the worm mesh but it's rare for Paramounts to need any sort of "weighting" to compensate for backlash. Just good balancing - especially with a bigger OTA like yours. Before you adjust anything, though, have you started a thread on the Bisque forum? They will want to see tracking logs (probably more useful for diagnosing a mount issue because they don't have the extra confounder of guider corrections) collected from within the SkyX, versus PHD. You should probably step through the entire Imaging System Analysis algorithm.

 

Sorry, that's all I've got.

See , this is what I was unsure of with the logs , I images last night till about 1am , I thought the 06/24 was the right one for last night but it doesn’t reflect the whole night of imaging it seems??

 

I honestly couldn’t find where it went bad in the log but i for sure saw it while guiding after the flip. The rms values I shared in my post where from the guiding session , Dec was about 0.30 and Ra leveled out at around 0.55

 

I was imaging ngc 5907 in Draco so , while closer to the pole not right next to it

 

its clouding up the next couple of days so I won’t be able to gather anymore data till Wednesday but I have the tracking logs from my PEC i could post in SB , as nothing has changed since then

 

im going to look in my log folder to see if I missed something because I took a total of 40 subs last night and I should of had a longer log file



#14 whirlpoolm51

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Posted 25 June 2022 - 02:06 PM

I admit that I'm having a bit of trouble following this.

 

You have two log files from PHD.

 

PHD2_GuideLog_2022-06-23_212652

PHD2_GuideLog_2022-06-24_210754

 

and they are from two different days, so conditions are potentially different.

 

Now, looking at those files (in chronological order as above):

 

attachicon.gif52.png

 

attachicon.gif54.png

 

I fully admit that I'm not a PHD guy, so I get a bit lost and I'm sticking my neck out, here.

 

I see the spikes caused by dithering (right?) usually more prominent in Dec than RA. I can also eyeball the RMS statistics (not shown above) which for Log #52 show RA: 0.26, Dec: 0.27, total: 0.38 - which are nicely matched between the axes. For the second log, #54 - a different day, I see RA: 0.23, Dec: 0.23, total: 0.33. Again, Log #54 is pretty well balanced. How did you derive your stated RMS values?

 

I just don't see a lot of difference between the log files - aside from the timing and sizes of the dithers. Moreover, I don't see anything particularly different between axes - again, aside from the dithers. Finally, I don't see anything that stands out as matching the ME2's 2:29 worm period. To my eye, there's no real smoking gun - just dithering and random noise.

 

When do you think the flip occurred in the above logs? What was the target? Was it near the pole? Can you, on the same night, collect a guiding log from the east, then flip the mount and do the same from the west at the same declination and approximately mirrored hour angles (say, an hour angle before and after meridian?)

 

It may be worth adjusting the worm mesh but it's rare for Paramounts to need any sort of "weighting" to compensate for backlash. Just good balancing - especially with a bigger OTA like yours. Before you adjust anything, though, have you started a thread on the Bisque forum? They will want to see tracking logs (probably more useful for diagnosing a mount issue because they don't have the extra confounder of guider corrections) collected from within the SkyX, versus PHD. You should probably step through the entire Imaging System Analysis algorithm.

 

Sorry, that's all I've got.

I figured it out, since I stopped and resumed guiding a few times, it made a few sub logs in that folder that you should be able to click through in the log viewer, that's where you will find when it went bad.

Use the 06/24 log

 

see in the top left where you can choose between guiding stops and starts

Attached Thumbnails

  • 2022-06-25 (1).png

Edited by whirlpoolm51, 25 June 2022 - 02:08 PM.


#15 whirlpoolm51

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Posted 25 June 2022 - 02:07 PM

sorry, this is what I found in the log where it went bad

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  • 2022-06-25 (3).png


#16 whirlpoolm51

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Posted 25 June 2022 - 02:24 PM

honestly, this looks like some form of backlash with overcorrection?? I posted to the SB forums but like I said I can't find my log files from Pec runs. I used the train pec wizard for the first time and the only associated files I could find were test pec fit files



#17 Ken Sturrock

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Posted 25 June 2022 - 03:07 PM

This does look like a fairly violent movement in RA with whiplash but all the other larger movements across the session seem confined to dithers. There is a little more movement after the following dither - but not much.

 

Screen Shot 2022-06-25 at 14.02.43.png

 

Notice, though, that when you add the Dec error back into the chart, a Dec error occurs at the same time so I wouldn't think that it's an issue confined to the tracking/RA axis because the Dec axis shouldn't be moving at all - something else is moving it (or the seeing is causing a star to jump diagonally).

 

Screen Shot 2022-06-25 at 14.02.55.png

 

It's certainly big, but it's still not much to go by. Nothing that appears related to the mount's gearing/period. Wind gust? Aircraft? Varmint? Loose cable? Some other mechanical clunk related to the stack?

 

If you think that there's a genuine issue pre- and post-flip then the simplest way to show that would probably be to collect a tracking log (no guider corrections - like what used to be standard for programming PEC) for a twenty minutes, or so, before and after a flip. Preferably close to the celestial equator to maximize visible movement in RA.



#18 whirlpoolm51

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Posted 25 June 2022 - 03:13 PM

This does look like a fairly violent movement in RA with whiplash but all the other larger movements across the session seem confined to dithers. There is a little more movement after the following dither - but not much.

 

attachicon.gifScreen Shot 2022-06-25 at 14.02.43.png

 

Notice, though, that when you add the Dec error back into the chart, the Dec error echos the RA error so I wouldn't think that it's an issue confined to the tracking/RA axis because the Dec axis shouldn't be moving at all - something else is moving it (or the seeing is causing a star to jump diagonally).

 

attachicon.gifScreen Shot 2022-06-25 at 14.02.55.png

 

It's certainly big, but it's still not much to go by. Nothing that appears related to the mount's gearing/period. Wind gust? Varmint? Lose cable? Some other mechanical clunk related to the stack?

 

If you think that there's a genuine issue pre- and post-flip then the simplest way to show that would probably be to collect a tracking log (no guider corrections - like what used to be standard for programming PEC) for a twenty minutes, or so, before and after a flip. Preferably close to the celestial equator to maximize visible movement in RA.

I found the logs from my pec training and I'm talking with tom over at SB now. 

thanks for taking a look at it.

 

see, when I was guiding, dec would jump a little but the error was still way less than RA, but if you look at the scatter plot it for sure shows the jumps diagonally. like the whole mount wobbles. I'm pretty confident that it's not a gearing issue though. watch it be some small setting I didn't check or something about the calibration.

 

I'm going to recalibrate phd on the bad side of the mount and see what i get



#19 whirlpoolm51

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Posted 25 June 2022 - 03:26 PM

now that I think about it, the only thing that changed was me getting a new scope and focuser and if both axes get worse after the flip, then something might be loose in my imaging train or focuser??

does this track right with you??

 

You know what sometimes hunting down the causes of these issues is kind of fun, not so much while imaging though lol



#20 Ken Sturrock

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Posted 25 June 2022 - 10:08 PM

Yes. I suspect that something loose/flexible with the payload may be the issue. I also agree that solving problems is part of the fun but it does get old. Especially when bending upside down in the dark with a flashlight between your teeth.



#21 whirlpoolm51

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Posted 26 June 2022 - 12:33 PM

Yes. I suspect that something loose/flexible with the payload may be the issue. I also agree that solving problems is part of the fun but it does get old. Especially when bending upside down in the dark with a flashlight between your teeth.

here is a 12-minute guiding assistant run from last night. other than my PA not being as good as usual I'm not seeing anything that stands out??

do you??

 

 

my drift rates are around -0.40 for both axis and PA error of 2.0"

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#22 Ken Sturrock

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Posted 26 June 2022 - 06:50 PM

No, I don't see anything odd, but I'm not knowledgeable about PHD or when/where you ran this. Like we discussed, I think the mount is probably fine and that you have something mechanical that moved at some point after the flip or something random happened which caused the guider to chase a squirrel.



#23 whirlpoolm51

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Posted 26 June 2022 - 07:01 PM

Thanks ken, I took some tracking logs for tom over on the SB forums just to be sure it's not the mount, but he even thinks it's something else also I just can't find anything Haha




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