Re: GM100: Is this a good deal?
Again it really depends on the control system that comes with it. Some had the 492 digital system, but there was an earlier drive that I assume was based on an R-C and 555 IC. The GM100 can carry a heavier payload than the G11.
?
The tangent arm limit the possibility of goto, but a well polar aligned mount doesn't need more then 15¡ã of Dec correction.?
?
The supports tangent are control and permits use of higher resolution motors and drive systems. This is my ex-492 GM-8 with 0.9¡ã step angle NEMA16 motors.?
?
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Re: GM100: Is this a good deal?
For a visual only, non imaging mount on a fixed pier as long as the Digital Drive is actually working and the mount is mechanically sound this is an excellent deal.? You should jump on it.?
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
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Re: GM100: Is this a good deal?
Thanks, Brendan. I don't intend to image, so it should work out for me.?
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Re: GM100: Is this a good deal?
But that is cheap and will do its job. ? I posted before thinking¡.again
?
cheers?
--
Brendan
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Re: GM100: Is this a good deal?
The only drawback is it has a tangent arm on DEC so limited imaging ability?
?
it¡¯d cost too much to bring to a full DEC like G11. ?I¡¯m only guessing?
cheers. ?FWIW?
--
Brendan
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Re: Irregular lurches in RA -- what to look for?
In my case, the front lens of the guidescope (which focuses by moving its front lens) was loose.? Since then I have only been able to test in rather unsteady air, but I've had no lurches larger than 4", and all of them were on both axes, looking atmospheric, so I'm optimistic.
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Re: Irregular lurches in RA -- what to look for?
I had a similar experience last summer with non periodic sudden error peaks of about 20" all in the? same direction within a guiding session. It turned to be clutch slippage due to oil migration that contaminated the clutch disks. Cleaning the disks with isopropanol helped a lot but for this season I may try high friction disks or simply replace them with new stock disks.
?
Regards,
Daniel
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Re: GM100: Is this a good deal?
Plinthly,
No driver required as it is not a goto controller.
You point it using push-to and can guide but need to an interface cable between a computer and the handset socket.
If you need to guider and use the hand controller you will need a phone splitter.
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On 6 May 2025, at 1:53?pm, plinthley via groups.io <pootco@...> wrote:
Looking at buying a blue GM100 mount head, serial number in the 008x range. Appears to be in pristine condition. Has motors and Losmandy digital drive system but seller says it needs Losmandy driver (still available?). No tripod, but i have a pier.
Intend to put a 10" mak-newt on it. Is $650 a good price for the GM100?
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GM100: Is this a good deal?
Looking at buying a blue GM100 mount head, serial number in the 008x range. Appears to be in pristine condition. Has motors and Losmandy digital drive system but seller says it needs Losmandy driver (still available?). No tripod, but i have a pier.
Intend to put a 10" mak-newt on it. Is $650 a good price for the GM100?
|
Re: Irregular lurches in RA -- what to look for?
It will be a few days before I can test under the stars, but...
- Almost all the lurches were westward, i.e., moments of RA not tracking fast enough.
- I found the RA motor cable plug about 1 mm short of being fully inserted. High resistance there may have been the problem.
I am going to go over everything and look for something loose. I'll keep you posted.
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Re: PEC with GM8 492 Controller
Thanks for the info and confirmation George and Mark.?
?
Avi?
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Re: PEC with GM8 492 Controller
Meade had PPEC, but I think first with the the 1992 LX200, which used a Motorola 68000 type MCU. Pin INT2 got a signal from a Hall effect IC on the RA worm. It was processed and stored in an external 4092 BIT EEPROM. The Ultima used Hall effect feed back to monitor motor speed, but the Celestar Deluxe used SAIA step motors and no other sensors..
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Re: PEC with GM8 492 Controller
The 492 was a development of the Celestron 1990 Ultima PEC System. It was a microprocessor quartz controlled closed loop system. For the G11 and Celestar Deluxe mounts the feedback loop was dropped and step motors were employed. All three mounts had PEC, but I don't believe they were PPEC (permanent PEC) with a memory. The Celestar Dlx was notorious?for failing to even record the?error stream. PPEC requires about 1-2K to store.
As you can see the 492 has an Intel 80C52 MCU. IIRC it had 256 bytes of internal memory and could support up to a 16K EPROM. The 64K EPROM couldn't be used for on-board programming.?
When I look at the 492, I remember?the first mainframe I worked on in the late '60s, it also had 64K main memory. That required 30+ ferrite bead plates each with 4,092 hand woven iron beads, more than 6 months work for a weaver. And barely over 20 years it's all reduced?to this.
The I-8051/2 design is still widely?copied, used and greatly?reduced in size and flash memory is now up to 2T in SD and smaller formats.
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Re: PEC with GM8 492 Controller
Avi,
?
Your understanding is correct: The PEC table evaporates when the power is cycled. So you must redo the PEC each session.
?
Part of the reason is because of the memory technology used in the older drives.
?
Another part of the reason is that the 492-equipted mounts do not have any feedback from the motor/worm assembly (aka encoder or PEC sensor).
?
At one point Meade and Celestron (if my old memory isn't failing) used the term PPEC for Permanent PEC.
?
Best regards,
?
Mark Christensen
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Re: Irregular lurches in RA -- what to look for?
Right, those are basically all the things to check!? It will be a
week before we have another clear night for testing.? I was
wondering if any specific cause jumped out at anyone, and in
particular if it was associated with the firmware upgrade
(although I can't see how a firmware problem would cause random
lurches).
Could it be too little DC voltage (12.6 V)?? My main power supply
has to stay under 13.0 because that's the limit for my Altair
camera.? I do have a 19-volt power supply I can use with the
GM811G.
It may still have been cable management -- something dragging
that I didn't catch.? In that case it won't recur next time.
On 2025-04-30 09:08, Paul Kanevsky
wrote:
Hi Michael,
?
Difficult to diagnose from a distance. A 12" jump sounds like
something beyond seeing conditions, unless you had clouds
passing through. Here are the things I'd check, in this order:
?
1. Check that everything is tightened down, nothing is loose
in the imaging/autoguider system
2. Check motor cables, make sure they are clean and making
solid contact
3. Reset Gemini to HGM default settings, to clear out any odd
settings, then reenter all the correct settings
4. Check for backlash in RA worm/gear, adjust if necessary to
reduce (adjustment depends on whether you have spring-loaded
worm or not). Large temperature swings can also result in some
issues with both, binding, and increased backlash.
5. Try moving to a different part of the worm-wheel: start in
CWD. Loosen the clutches, move the RA axis 90 degrees by hand,
tighten the clutches. Then, using Gemini HC arrow buttons,
rotate the axis back to CWD, or -90 degrees. Restart Gemini
using cold start from CWD position. This should move the mount
to use a different portion of the worm wheel, just in case there
were some problems or dirt on the part where you had trouble.
6. Check that your gearboxes are attached properly, possibly
swap gearboxes to see if the RA problem goes away
7. Check the oldham coupler and tighten the screws on both
sides if anything is loose
8. Check/clean/relube the worm -- there may be dirt or
particles that are in the way that are causing sudden jumps.?
9. Try reverting to a previous version of firmware to see if
that would make a difference
?
Regards,
?
? -Paul
?
?
On Tue, Apr 29, 2025 at 10:26 PM, Michael A. Covington wrote:
Last night my GM811G gave really poor autoguiding
with a setup that had
previously worked very well all the time.? C8 EdgeHD, iGuider
guidescope
bolted to the side of the mount saddle, PHD2, NINA.? Normally
this setup
gives me approximately 0.7" RMS guiding at my site.
Last night, though, there were frequent large irregularities
and lurches
(2" to 12"), mostly in RA, somewhat in declination too (enough
to
deflect suspicion away from the RA drive but not totally
exonerate it).?
They were at very irregular intervals, 30 to 90 seconds apart,
and a few
were bad enough to produce multiple images of stars.
My first thought was that a cable was dragging, but
rearranging the
cables a couple of times didn't fix it.? Nor did the
guidescope or guide
camera appear to be loose in any way, though I'm going to take
them off
and put them back on carefully the next time I have the mount
out.
I had just upgraded the Gemini firmware, and I made sure that
its PEC
was turned off.
I made sure the RA clutch was tight enough but not too tight.
I had PHD2 recalibrate, just in case it had been mistaken
about the
guidescope, and tried a couple of different guiding
algorithms.
The air didn't *look* unsteady, but could this be an
atmospheric problem
after all?? An effect of the slight east breeze (4 mph)?
Or does my RA drive require cleaning and lubrication or
something?? The
mount is 3 years old and has been used lightly.
Thanks!
--
Michael A. Covington, Ph.D.
Consultant, Covington Innovations, Athens, Georgia, USA
--
Michael A. Covington, Ph.D.
Consultant, Covington Innovations, Athens, Georgia, USA
|
PEC with GM8 492 Controller
Hello All,
?
I have a non-goto Losmandy GM8 with the 492 digital drive that is working quite well for me.?
?
I have been running some guiding "tests" over the past week just to see what kind of tracking performance I get w/ and w/o guiding, w/ and w/o PEC etc. I am actually quite happy with the results and I am seeing further improvements with PEC applied.?
?
My assumption was that once generated the PEC is stored within the 492 and would automatically get applied to the next session. But from what I can tell, that does not appear to be the case. Is that true? Does the PEC generation protocol need to be re-run each time I start up the controller??
?
Sequence of events:
?
1. After successful guide calibration with PhD2, I started autoguiding
2. After ~10 mins of autoguiding, I hit the PEC button on the 492 panel and the red LED started flashing telling me that it was in recording
3. After ~8 mins (worm period on GM8), the red LED stopped flashing telling me that the PEC had been applied.?
4. I continued autoguiding with PEC turned on and I saw an improvement to an already good tracking performance.
5. After wrapping up my tests, I turned the 492 unit off and turned it on again.?
6. PEC light was off by default (I was thinking it would remain ON since I had already gone through PEC generation). When I hit the PEC button, it started flashing again.....so effectively restarting PEC generation?
?
I really don't mind redoing it (I need to redo guide calibration each time anyway, so an additional 8 mins is no big deal), but just wanted to understand how the system works. The manual does not provide much information about this.?
?
Many thanks!
?
Avi
?
?
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Re: Problem with Gemini 1
?Hi John,
?
Did you ever get your G1 servo motor issues resolved???
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: Irregular lurches in RA -- what to look for?
Hi Michael,
?
Difficult to diagnose from a distance. A 12" jump sounds like something beyond seeing conditions, unless you had clouds passing through. Here are the things I'd check, in this order:
?
1. Check that everything is tightened down, nothing is loose in the imaging/autoguider system
2. Check motor cables, make sure they are clean and making solid contact
3. Reset Gemini to HGM default settings, to clear out any odd settings, then reenter all the correct settings
4. Check for backlash in RA worm/gear, adjust if necessary to reduce (adjustment depends on whether you have spring-loaded worm or not). Large temperature swings can also result in some issues with both, binding, and increased backlash.
5. Try moving to a different part of the worm-wheel: start in CWD. Loosen the clutches, move the RA axis 90 degrees by hand, tighten the clutches. Then, using Gemini HC arrow buttons, rotate the axis back to CWD, or -90 degrees. Restart Gemini using cold start from CWD position. This should move the mount to use a different portion of the worm wheel, just in case there were some problems or dirt on the part where you had trouble.
6. Check that your gearboxes are attached properly, possibly swap gearboxes to see if the RA problem goes away
7. Check the oldham coupler and tighten the screws on both sides if anything is loose
8. Check/clean/relube the worm -- there may be dirt or particles that are in the way that are causing sudden jumps.?
9. Try reverting to a previous version of firmware to see if that would make a difference
?
Regards,
?
? -Paul
?
?
On Tue, Apr 29, 2025 at 10:26 PM, Michael A. Covington wrote:
Last night my GM811G gave really poor autoguiding with a setup that had
previously worked very well all the time.? C8 EdgeHD, iGuider guidescope
bolted to the side of the mount saddle, PHD2, NINA.? Normally this setup
gives me approximately 0.7" RMS guiding at my site.
Last night, though, there were frequent large irregularities and lurches
(2" to 12"), mostly in RA, somewhat in declination too (enough to
deflect suspicion away from the RA drive but not totally exonerate it).?
They were at very irregular intervals, 30 to 90 seconds apart, and a few
were bad enough to produce multiple images of stars.
My first thought was that a cable was dragging, but rearranging the
cables a couple of times didn't fix it.? Nor did the guidescope or guide
camera appear to be loose in any way, though I'm going to take them off
and put them back on carefully the next time I have the mount out.
I had just upgraded the Gemini firmware, and I made sure that its PEC
was turned off.
I made sure the RA clutch was tight enough but not too tight.
I had PHD2 recalibrate, just in case it had been mistaken about the
guidescope, and tried a couple of different guiding algorithms.
The air didn't *look* unsteady, but could this be an atmospheric problem
after all?? An effect of the slight east breeze (4 mph)?
Or does my RA drive require cleaning and lubrication or something?? The
mount is 3 years old and has been used lightly.
Thanks!
--
Michael A. Covington, Ph.D.
Consultant, Covington Innovations, Athens, Georgia, USA
|
Irregular lurches in RA -- what to look for?
Last night my GM811G gave really poor autoguiding with a setup that had previously worked very well all the time.? C8 EdgeHD, iGuider guidescope bolted to the side of the mount saddle, PHD2, NINA.? Normally this setup gives me approximately 0.7" RMS guiding at my site.
Last night, though, there were frequent large irregularities and lurches (2" to 12"), mostly in RA, somewhat in declination too (enough to deflect suspicion away from the RA drive but not totally exonerate it).? They were at very irregular intervals, 30 to 90 seconds apart, and a few were bad enough to produce multiple images of stars.
My first thought was that a cable was dragging, but rearranging the cables a couple of times didn't fix it.? Nor did the guidescope or guide camera appear to be loose in any way, though I'm going to take them off and put them back on carefully the next time I have the mount out.
I had just upgraded the Gemini firmware, and I made sure that its PEC was turned off.
I made sure the RA clutch was tight enough but not too tight.
I had PHD2 recalibrate, just in case it had been mistaken about the guidescope, and tried a couple of different guiding algorithms.
The air didn't *look* unsteady, but could this be an atmospheric problem after all?? An effect of the slight east breeze (4 mph)?
Or does my RA drive require cleaning and lubrication or something?? The mount is 3 years old and has been used lightly.
Thanks!
--
Michael A. Covington, Ph.D.
Consultant, Covington Innovations, Athens, Georgia, USA
|
Re: Off Topic: Convert PT Pier into something more permanent.
Simpler yet, drill and tap some holes at the top and as far down as you can and still hit the inner square tube. Four bolts per side. Then screw in clamp bolts. That way you still have the option of moving it up and down later on. Dunno how thick the aluminum is so best maybe to use a fine thread. And small bolts. Like 1/4" x 28. As many threads engaged as you can.
?
Also has the option that it's cheap and easily reversible. 16 bolts and maybe an hour with a drill and tap. Or give it to me! (Grins).
?
Mike
?
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Chip Louie
plinthley
Paul Kanevsky