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Old 11-10-2019, 10:45 AM
Pepper (Steve)
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Guiding issue. Help !

Having this seemingly random issue when guiding.
Iíve attached a pic of what happens.
Everything seems to be going ok when all of a sudden the dec will drop into oblivion and beyond. Takes about 25sec to come back.
When it happens I see a sudden movement in the PhD window then mount goes nuts to recover.
Any ideas what is causing this?
Thanks in advance.
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  #2  
Old 11-10-2019, 11:02 AM
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that_guy (Tony)
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check cabling and connection. Sometimes the camera will drop out for a frame or two which causes the star to drift x amount. Cable snag on the DEC axis can also cause something similar.
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Old 11-10-2019, 11:16 AM
Pepper (Steve)
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ive had a check of the connectors, changed a few but still get this downward spike.
the movement I see on the screen is more than merely a few frames, its almost like the guidescope gets bumped it moves that far.
all the screws are tight and on the surface there doesent really look like a chance of slipping.
I get an error when phd calibrates warning me of minimal south movement guiding may be affected. this must be related, but how?
ive got a suspicion that somehow the counterweight supplied(5kg) is too heavy and is mucking with it somehow.... I had all intentions of trying with something lighter but the clouds came over and shut me down.
should I just make sure my PA is spot on and switch off dec corrections?
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Old 11-10-2019, 11:48 AM
Imme (Jon)
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How often does it occur?

You may be looking at a bit of crap on one of your gears and every complete cycle of the gear it 'hops' over the piece of crap......only way to fix it is pull down and clean I'd suggest.

Best way to test this would be to time how often it 'randomly' occurs. If the random occurrence is the same timing between events then this is definitely the issue.

Oh.....and if it is a piece of crap on the gear you don't have a guiding issue.....guiding is working awesomely!
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Old 11-10-2019, 11:54 AM
Pepper (Steve)
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happens anywhere between 6-10min. sometimes get an "aftershock" a min or so after a event.
should have mentioned I spent a day pulling the dec axis apart, cleaned with wet and dry, and relubed with lithium grease. seems smooth enough, gears don't seem to do anything funny when I manually slew. ring and worm were also thoroughly cleaned. both looked to be in good shape.
really got me in a funk as im constantly chucking subs.
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Old 11-10-2019, 12:50 PM
kens (Ken)
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Can you post the guide log?
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Old 11-10-2019, 12:52 PM
Imme (Jon)
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Scrap my idea then!


Quote:
Originally Posted by Pepper View Post
happens anywhere between 6-10min. sometimes get an "aftershock" a min or so after a event.
should have mentioned I spent a day pulling the dec axis apart, cleaned with wet and dry, and relubed with lithium grease. seems smooth enough, gears don't seem to do anything funny when I manually slew. ring and worm were also thoroughly cleaned. both looked to be in good shape.
really got me in a funk as im constantly chucking subs.
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Old 11-10-2019, 03:43 PM
Pepper (Steve)
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ken, ill try to find it


edit.
here is the zipped guidelog.
or did you mean the debuglog?
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File Type: zip PHD2_GuideLog_2019-10-09_201057.zip (169.1 KB, 7 views)

Last edited by Pepper; 11-10-2019 at 04:02 PM.
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  #9  
Old 11-10-2019, 07:48 PM
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RobF (Rob)
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You might also want to sit very close to the mount for a couple of full worm cycles. You can sometimes hear little clicks and bumps if you worm/gear settings aren't quite right.
Or you might catch a cable slipping then grabbing as Tony suggested.
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Old 12-10-2019, 02:38 PM
kens (Ken)
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The issues are on the dec axis. It looks like a large backlash with some stiction. Check the gear mesh on the dec axis.
In addition the calibration is suspect although that is not causing your problems. But it could indicate something going on. Every second calibration step is almost adjacent to the one before. That is on both axes.
You've also got quite a big drift on your dec axis. Could be poor PA or flexure from a loose fitting somewhere

edited to add:
A photo of your rig may shed some clues
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Old 12-10-2019, 07:26 PM
Pepper (Steve)
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Thanks mate, just partying at the moment, will take pic of rig when I get home.
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Old 13-10-2019, 03:18 PM
Pepper (Steve)
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Ugh, big night last night. Paying for it today.
However as grim as that is, had a fiddle with the mount for a few hours.
Played with balancing and worm gear meshing, as I noticed when turning when tilted it would kinda jutter.
Anyhoo that all seems cleared up now, Iíll give it a test among the clouds tonight.
Pic below.
My guidescope I have mounted to the side, itís like that to clear my garage door.
Hope that isnít a possible cause, be my next port of call to change to top as much as I donít want to.
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Old 14-10-2019, 05:27 PM
kens (Ken)
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Guidescope on the side is not a problem but does make balancing in all directions more difficult. That could explain the judder and also the occasional big guide jumps.
The pic also shows you are using guide rings with three positioning screws. Proper clamps would be better but at least make sure they are very secure.
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Old 21-10-2019, 12:14 AM
Pepper (Steve)
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Good news. I think I have it sorted out.
Thanks everyone for their words of wisdom.
So, I took mount apart today and took the ring gear drum completely off.
Itís the only thing I didnít remove as it was quite tight when it got halfway off.
Hit the friction surfaces with wet and dry, give a good grease and put it back together.
Spent a bit of time with the worm adjustments as well. Happy to say it runs and sounds like new. And more importantly the nasty dec spikes have disappeared. One other thing of note I did was to run the guide cam off the USB2 port and the dslr into the usb3 port. I had them in each of the usb3 ports previously.
Happy nights.
Polar alignment still needs work as it was working a bt much with corrections to south.
Anyways, main issue sorted.
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