My G11 decided to have a guiding hissy fit at Snake Valley and as a result I got zero imaging done. So I have totally stripped the mount cleaned all the bearings, worm and gears and re lubed. Set up both worms and gear with feeler gauges and still it is carrying on. RA looks fine, but Dec is the pits. I have confirmed I have slight movement between worm and gear, as I thought it may have been too tight and binding. When I lubed the worm and gear, I gave the whole gear a complete turn each way and there was no binding at all. This has me stumped.
Have just parked the mount and CWD is spot on, but the scope instead of pointing South is pointing East. Something is seriously amiss with the dec.
Any ideas on the one chaps, I am tearing my hair out....
Not really Pete sorry, but the undulating is too regular to be much else. I can never read the PHD graphs (I use Maxim), but the feeling is some form of "periodic error".
What is "CWD"? Your second to last sentence has me stumped as well, (not the hair tearing), why is the scope pointing east instead of south?
Gary
Couple of questions Pete. What's the image scale on your guider set-up. I mean what are we looking at? +/- what? Regardless DEC has to be as tight as you can get it without binding. Too much backlash in DEC is not advisable. Your graph indicates a very rapid shift in DEC with PHD bumping the mount real hard on a periodic basis.
That can be a tight spot in the worm or a balancing issue or a bad alignment causing a shift too rapid in DEC, or as simple as a greasy clutch disc, but the drift would be random and continuous.
To diagnose these things the first thing you need to do is disable the guide output in PHD, do a basic drift alignment and see what happens without guiding then take it from there. There are too many variables to try to diagnose everything at once and you need to go through a process of elimination.
Forget what you did on the night thinking I've already checked that. You probably were tired, frustrated, wanted to start imaging asap and missed a lot of things. Been there done that.
Thanks chaps. CWD= counterweight down. I know balance is not an issue as I spent quite a while getting that correct. My guidescope is an ED80, and the guide camera is the Orion Starshoot Autoguider.
Marc, not sure as the what you mean relating to the image scale +/-??
I know the clutches are dry and clean as I did them with the service. Drift alignment should be pretty good as I have registration marks on my pier/mount, so it is just a matter of plonking the mount back on the pier and aligning the registration marks. If it is out, it would only be a poofteenth, and should definitely be able to be corrected by guiding. Also the fact that the mount does not end up in the proper parked position has me stumped as well.
My guidescope is an ED80, and the guide camera is the Orion Starshoot Autoguider.
Ok - I guided on an Orion ED80 with a Q-guider so you have an image scale of approx. 1.8asp. Looking at your graph then the amplitude of the jumps is not excessive.
Quote:
Originally Posted by Exfso
I know the clutches are dry and clean as I did them with the service. Drift alignment should be pretty good as I have registration marks on my pier/mount, so it is just a matter of plonking the mount back on the pier and aligning the registration marks. If it is out, it would only be a poofteenth, and should definitely be able to be corrected by guiding.
So what happens when you graph in PHD and let the mount track with the guide output disabled?
Quote:
Originally Posted by Exfso
Also the fact that the mount does not end up in the proper parked position has me stumped as well.
Different issue. You might have your limits or home position set wrong. I wouldn't worry about that right now. Are you using Gemini?
Yeah Marc, using Gemini. I have not changed the limits at all and up until last week it used to park home position CW down pointing at SCP.
Re disabling the guide output, I will try that tonight after I re check drift alignment.
Yeah Marc, using Gemini. I have not changed the limits at all and up until last week it used to park home position CW down pointing at SCP.
Re disabling the guide output, I will try that tonight after I re check drift alignment.
No worries. That will give you a good indication if it's mechanical or software related. Get the mount to track as good as it can first then start guiding and see what happens. Might be good to do a cold start in the CWD position and erase any model so you start afresh as well.
Thanks Marc, I have been only doing cold starts since I got back from camp. I reset the home position today from the hand controller, that should fix one problem, but if you start the mount cold from the CWD position and scope pointing at SCP, it should recognise that as the parked position.
Thanks Marc, I have been only doing cold starts since I got back from camp. I reset the home position today from the hand controller, that should fix one problem, but if you start the mount cold from the CWD position and scope pointing at SCP, it should recognise that as the parked position.
Indeed it should. But don't worry about that yet. That won't effect your tracking.
I got the home position all sorted. Did a check on polar alignment tonight using the drift method, no star movement in 10 mins, so I reckon I am pretty well polar aligned.
The PHD graph is still shocking. I disabled the guide output and the dec and ra graph chased themselves off the scale.
Beginning to think it is either my Gemini guider port, dodgy starshoot autoguider, or a cable issue. I have a toucam which I will connect tomorrow night via gpusb and see if that will work ok. Beginning to clutch at straws now.
Pete,
look on the bright side, if you can track for 10 minutes, then at least on good nights you can image, just need shorter subs.
OK, take it one step at a time. Try the whole new setup for guiding (ToUcam, GPUSB, another cable) then slowly mix and match the existing parts.
Does the Gemini have an "optimum" guide speed, and if so was that set. I know that with my EM200 I use the guide speed, but for quick slewing or centring I use the H/S setting. Now if I forget to return to the guide setting it goes wild.
Gary
I got the home position all sorted. Did a check on polar alignment tonight using the drift method, no star movement in 10 mins, so I reckon I am pretty well polar aligned.
The PHD graph is still shocking. I disabled the guide output and the dec and ra graph chased themselves off the scale.
Beginning to think it is either my Gemini guider port, dodgy starshoot autoguider, or a cable issue. I have a toucam which I will connect tomorrow night via gpusb and see if that will work ok. Beginning to clutch at straws now.
When the PHD guide output was disabled you say the dec and ra graph chased themselves off the scale. Just oscillations? No drift correct? Because if you are polar aligned well enough to have no drift in 10min then you should have a fairly straight PHD graph.
That's the part I couldn't understand. Slowly and surely off the graph perhaps, but not chasing/oscillating.
Gary
Well I assume that if you have no star movement in 10min after drift alignment that would show as a very minimal drift in PHD over a significant period of time.
When you disable the guide output all you're left with is the worm noise. I have had instances in bad seeing when by disabling the PHD output my RA and DEC flat lined because the mount was tracking better than chasing the seeing while guiding.
If there are still problems in DEC and RA with the guide output disabled then it is a mechanical problem. Meshing, balance. Could be anything. A G11 well polar aligned should give you a very narrow graph in PHD with a small amplitude over 1 min at least at this image scale.
Marc, I tried so many things last night, you are correct, the dec line was dead flat along the centre, but the ra was still jumping about. (from memory)
Marc, I tried so many things last night, you are correct, the dec line was dead flat along the centre, but the ra was still jumping about. (from memory)
Ok. Now we're getting somewhere. Double check your clutch discs to make sure they're not greasy. Check your meshing in RA to make sure it's not too tight and check your balance as well until you got smooth RA. Is your RA motor hot when you touch it? Change the RA cable as well to make sure it's not the cable. (swap with the DEC cable). Then you can start guiding again and see what happens. I'm pretty sure it'll be all good.
John and Doug pulled Pete's mount apart at Snake Valley. Everything was cleaned and regreased.
Pete, I still think you should remove one/all of your finderscopes and retry. Humour me.
H
Hi H, yeah I saw that. If it tracks badly on its own in RA it can be only a number of things and they're all mostly mechanical. Unless the cable's bad ( I had that) or the motor has overheated and is misbehaving now. I haven't seen a picture of the rig so hard to tell what's on it too.
I have spoken to Pete this morning and I am getting him to remove everything bar the OTA and to attach his guider to that and do another test, also as he has another guider I have asked him to put that on and do an identical test as well, pending the results of this test it should eliminate whether it is mechanical/hardware or software related.
My original thoughts were a balance problem but that was eliminated at SV with a very careful rebalance of everything.
