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Re: Meridian flip sanity check please?
OK, after posting on the discord and not getting a workable answer I think I figured it out for myself.? This is not a NINA or Gemini issue.? It is a misunderstanding of the settings and process on my part.? When NINA decides it is time for a meridian flip it does the flip simply by issuing a GOTO to the same target.? The reason my NINA flips were failing was because when NINA triggered a flip, the target was PAST the meridian but it was NOT past the western GOTO limit so the scope correctly decided the target was still reachable from the same side of the pier and the NINA's GOTO did not trigger the flip.? At that point, the flip has been triggered and failed and the mount will simply continue tracking until it hits the western safety limit.? Happened a couple times.?? After some head scratching and experimentation, I set my western GOTO limit equal to my western safety limit minus 90 (95-90=5 degrees in my case).? This causes Gemini to perform a meridian flip for any GOTO to a target any amount west of the meridian.? To prevent a race condition, I set NINA to trigger a flip one minute (0.25 degree) PAST the meridian.? Set this way, a flip is triggered when the current exposure ends with the object at least one minute past the meridian.? With the object one minute (or more) past the meridian, NINA issues a new GOTO which causes the scope to flip and Paul is a happy astronomer ;)?? The takeaway is to make sure that NINA is configured so that any flip is triggered with the object PAST the western GOTO limit but of course NOT past the western safety limit.? In my case, there is a 5 degree overlap (20 minutes) and since I never use more than a 10 minute exposure, a flip will always be triggered before the mount hits the western safety limit.?? Paul |
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Re: Gemini-2 momentarily went haywire
That's a new one on me.?? I've not heard a motor at a high speed, not even at the fastest slew speed,? "scream."? I think you get this kind of gear scream when the driven side is stuck and the drive side has only got a frictional connection.?? The only sense the Gemini has for motor movement is the optical encoder in the motor.? If the optical encoder signal is not received? ?then the Gemini will continue to put DC voltage to the motor until it "sees" the optical encoder move.? If the motor can't move because of a stall condition (axis can't turn), then the Gemini should stop trying to move the motor, because throwing more power into a stuck motor would only burn out the motor.? The Gemini would then tell you "Stall".?? So I'm at a loss to understand how your drive would be screaming (meaning it's still getting power to the motor).? That implies the motor shaft is still moving (so Gemini thinks the motor is still free to turn), but some other gear is possibly loose and that is rubbing and screaming from friction.? Suspects would be the two transfer gears (their setscrews can work loose...if you have tucked motors), or the Oldham coupler ends (those would not scream).? The pinion gear at the end of the motor shaft is glued on (like super glue)...I suppose that could come loose but I've never seen that.?? Let us know when you discover the cause of your trouble.? We can all learn from this experience...and it's cure.?? Very best, Michael On Mon, May 3, 2021, 9:24 AM <papagordygrapes@...> wrote: When I mean "screaming", I'm actually talking about the servo motor screaming at high speed. |
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Re: Gemini-2 momentarily went haywire
?papagordygrapes,
Hope you scope did not bottom out and collide with anything. My issue with this also seems to have returned after being quiet for a week or two. The Dec motor runs at super high speed after touching any Dec button, either on the Hand Controller or the Virtual Controller. This occurs right after startup. If I can get past that by restarting, then I am ok. But whether it happens or not seems completely random. But once it does, my model is lost and I must return to CWD and do a Cold Start. I have traced this to the Dec output on the Gemini 2. I wonder if replacing the Gemini board is the critical step. But my next attempted fix is going to be to reload the firmware. We'll see what happens after that. John John |
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Re: Editing posts - please don't
Previously I was looking at what was on the webpage. There I did not see all email addresses. However, they are visible in the distributed emails from the group. I would agree with you Alan, that an option to suppress that information for those who want it would be nice.?
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Re: OnStep G11 First Light - 119 Second PE?
¿ªÔÆÌåÓýHi Brian, Thanks for your insight here. I do occasionally see DEC side move in sympathy to RA.?? As for
something slipping, I'm quite certain everything is tight.? The
helical focuser on the guidescope does not rotate the camera, and
it was pinned tightly with the set screw before I calibrated.??
Ive also seen this before with the the meade.? As best I can
figure, its simply wind.? I was carrying a 127mm f9 refractor
which has quite a long moment arm, and even a gentle breeze can
cause significant error with such a long lever.? The weird part is
that it seems to largely coincide with the repetitive guide
error.? That has me scratching my head a bit, so I'm not 100% sold
on wind, but lack any better theory. Yes, I will certainly run GA to see what it suggests.? As
mentioned, I just took the numbers from the previous mount to get
a quick headstart.? I'll run GA for numbers specific? to this
mount before my guiding performance really means anything.? As for
polar alignment, I use sharpcap which shows I was pretty close.?
I'm still temporarily using a tripod on a brick patio which could
possibly shift a few arc-sec over the course of the night, but
probably not arc-minutes. I'll take your suggestion on moving backlash comp max to 1500.?
Not sure it's run long enough to fully learn yet, but I just
checked and seems it had landed on 189ms most recently.? I'm
running the worms tight, very close to binding at the high points
of the wheel. I will certainly try to iron out the error by mechanical means
first and foremost.? I'm hoping the helical coupler will do the
trick.? If not, I may swap worms and blocks between the axes as a
next troubleshooting step.? I dont believe I can use the oldham
couplers due to different shaft sizes, at least not without boring
the motor side out.?? Once I can get the mechanical error toned
down a bit, I should be able to increase my exposure length to
reduce seeing variances, even though the multi-star guiding does a
pretty good job IMO. Great to hear you and my father has such a good report.? Yes, his
imaging is really coming along nicely.? He's been doing his own
processing for some time now.? Once in a while I may help him with
some gradients or something. He has some really nice skies by new
york standards, bortle 2 I believe, so he doesn't often have to
deal with gradient removal.? I'm in bortle 6 and anything to the
south (or past meridian) is even worse.? Gradients are life. Thanks again for your help and suggestions,
On 5/2/2021 10:12 PM, Brian Valente
wrote:
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Re: Gemini-2 momentarily went haywire
Screaming (by the Gemini, not the owner) often says the mount reached an RA safety limit.? So check to see if you were near the Western limit.? You can change limits, of course. Best of luck, Michael On Mon, May 3, 2021, 8:10 AM <papagordygrapes@...> wrote: Update:? mount was working perfectly for several nights.? No runaway slews or anything. |
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Re: Gemini-2 momentarily went haywire
Hi Mike You updated your case on this, i sent you a response via email On Mon, May 3, 2021 at 7:10 AM <papagordygrapes@...> wrote: Update:? mount was working perfectly for several nights.? No runaway slews or anything. --
Brian? Brian Valente portfolio |
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Re: Gemini-2 momentarily went haywire
Update:? mount was working perfectly for several nights.? No runaway slews or anything.
A couple nights ago I set up and polar aligned.? Slewed to a target.? Once it finished slewing, I went back inside for ~5 minutes? (leaving the mount running).? I came back out and I immediately heard the mount screaming.? Ran over and shut it off.?? So because this occurred during tracking, it tells me this is an RA issue.?? Also I just re-snugged the cables and resumed using it (while monitoring).? I strongly suspect this is a connector issue.? I guess my next step is to attempt to reproduce the problem again while jiggling the RA cables/connector. |
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Re: OnStep G11 First Light - 119 Second PE?
Hi Tony i have just a couple observations for you - sounds like you have a good handle on things so just the highlights: - your long guiding run looks quite good. RA and DEC seem to have a lot of movement in common, which makes me think it's either a calibration orthagonality issue (which it isn't based on your calibration run) or perhaps something is slightly slipping or rotating in your guide setup - your min moves might be a bit high, there's a lot of wandering about in there.?
you might do a Guiding Assistant run here for recommendations as well as measuring your polar alignment, which seems a bit off as well - i would increase your backlash compensation max move to 1500.? - definitely see what you can do about that 2x error. You can also use PPEC and target that period directly, but it's easier and more effective to do mechanically Your dad is awesome, I think you are doing processing for him? some pretty impressive stuff so far On Sun, May 2, 2021 at 3:59 PM GuitsBoy <guitsboy@...> wrote:
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Brian? Brian Valente portfolio |
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Re: Dec "drifts" randomly, after meridian flips...
John- ? Thanks for the input, responses embedded below... ? On Sat, May 1, 2021 at 10:07 PM, John Kmetz wrote:
Dec drift could come from PA which is off somehow. I usually start with PoleMaster, but double check with PHD2 drift align, the gold standard. These can differ to some degree. If your image frame is moving in one direction during the evening, that would confirm a PA issue.The thing is that PHD2 is essentially showing bad PA, (through GA), but the "pulling" (while guiding), or drift (while doing GA) that would be indicative of bad PA, (potentially), dissipates after about 15 minutes. I have not run GA after that, (because I am busy imaging), but it is probable that GA would show decent PA then. Additionally, I have run the same PA for multiple nights, (mount is on a pier), and gotten good PA results on consecutive nights. Additionally, sometimes the start of an imaging run is fine, but this phenomenon happens for 15+/- minutes after a meridian flip, but then settles. I assume you have tried recalibrating PHD2, especially if you are changing between two scopes. Using the right focal length in the brain settings is important. Any flexure in the guide cam, are the screws tight, focuser rack locked down? The clutches can wear over time. Perhaps replace with new Losmandy ones or the Michael Herman high friction ones.I always recalibrate if changing scopes or any orientation of the guide scope or OAG. In the examples log above, I had been using the previous nights calibration, and ran another after confirming PA with Polemaster as a sanity check. I got a similar bad PA alignment result from PHD2 GA, but if you read through my list of actions, and check the corresponding logs, you'll see how the issue exhibits as a temporary issue, almost if PHD2 is fighting some issue with the mount until it gets it under control. I like the idea of clutch slipping, but I am pretty certain it's not that for numerous reasons. It would? be a simple solution, however. Focal length is extremely diligently set per plate solving and calculating from that. Yes to all of your other suggestions. Do the Star Cross test in PHD2, see if the scope is moving as expected.Although I haven't done the Star Cross test, as I mention PHD2 is controlling the mount pretty well and the mount is responding appropriately. If I was not guiding (see guide logs showing GA runs), the Dec wanders off in one direction, but only temporarily. (15+/- minutes.) You'll probably have to just keeping working the problem to see if it is software or hardware. Yes, like everything else in this hobby! Thanks for the thoughts. |
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Re: OnStep G11 First Light - 119 Second PE?
¿ªÔÆÌåÓýHi Brian - Thanks for your response.? Since you asked, I will provide the logs, however your time would certainly be better spent helping others who have already reached the end of their own troubleshooting.? I certainly dont want to take time away from those would could really use you.? Like my Dad. :)? This was merely a shakedown run, and I haven't had a chance to do any tweaking yet.? With the clouds, I wasn't expecting much.? I didnt even run the calibration in a suitable location,? and I didnt bother running the guiding assistant yet.? When I get some better conditions, I certainly will, but this was just to get a quick and dirty baseline. Thanks for your document.? I'm familiar with just about all of the stuff you cover in there.? Most of which, I knowingly skipped over or cheated in the interest of beating the heavy clouds.? Since the final gearing ratio of the direct drive G11 (1:360) is reasonably close to my meade LXD650 (1:405) I reused many of the settings and tactics that I learned over the last year with the meade.? Again, willfully cheating in the interest of time. As for PEC prep, I'm not using it in the normal way.? I'm simply using it as a tool to show the period of the error while guiding, since visually, you can see its very regular.? I just wanted it to clue me in on where the error resides in relation to the worm period.? While yes, some of the guide error is reactionary in nature, there still must be a regularly occurring glitch in the drivetrain.? At 120 seconds, I have to suspect the coupler.? Had it been 240 or 75 seconds, Id suspect the worm or bearings.? Could still be, but for now, I switched out the rigid coupler to a flexible helical coupler to see if things improve next time. Please don't spend any time analyzing some quick and dirty logs
from an unfamiliar control system, especially since it was nothing
more than a test run to make sure things were working correctly.??
Truthfully, I'm already quite impressed with the mount having done
as well as it did, especially through the clouds.? Diagnosing,
tweaking and improving is all part of the fun.? I'll be sure to
run guiding assistant next time to see where the native unguided
PE lands.? Unguided performance really isn't terribly important
for me in particular.? Simply getting any abrupt drivetrain
defects down to where they can be guided around is my ultimate
goal.? I was mostly just curious if the 119-120 second periodic
error rang a bell for anyone. Thanks again for your help and suggestions,
On 5/2/2021 5:01 PM, Brian Valente
wrote:
Hi Tony |
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Re: What vintage Gemini-1 do I have?
Pete my guess is your mount is circa 1992, especially with the Celestron branding If you are considering the Gemini 2 upgrade, you might want to call Tanya at the main shop number. She may extend the special rebate on a retro-fit kit to you, I think it's worth checking out Brian On Sun, May 2, 2021 at 2:10 PM Pete <pete.ingram@...> wrote: Mount serial number? HGM9211145 It is branded Celestron? --
Brian? Brian Valente portfolio |
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Re: What vintage Gemini-1 do I have?
Hi Pete RJ style connectors preceded?the DIN-style connectors (which are still in use today in the Gemini 2) What is the serial number of your mount? On Sun, May 2, 2021 at 12:10 PM Pete <pete.ingram@...> wrote: My posts here are beginning to look like a game of "Guess the Gear."? However I am new to the Losmandy universe so please bear with me, than you.?? --
Brian? Brian Valente portfolio |
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Re: OnStep G11 First Light - 119 Second PE?
Hi Tony
Can you share the guidelogs from your screen caps? i'm assuming if you have not yet done the unguided output, the PECPrep is a residual error, and not the raw periodic error of the mount I have seen the 2x be a function of the coupler. It could be slightly off-kilter but if you've moved to the oldham, it would be the same thing. You can try to measure the distance between the coupler and the plate beneath it using an improvised measurement (like a hex wrench or stick) and just make sure it's consistent all the way across? Getting a solid 30-45 minute unguided run from guiding assistant in PHD is a great idea (i recommend the latest 2.6.9 dev 4 release). Here are steps for a baseline guiding which I always recommend people start with to eliminate a lot of inadvertent variables in the setup https://www.dropbox.com/s/os1thorvswmzaul/How%20to%20create%20a%20baseline%20for%20guiding%20results%20using%20OpenPHD2.pdf?dl=0 Brian |
Michael Herman
Pete