Plinthley:

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No need for a driver. In fact, there never was a driver.

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The guiding works via the good old trusty ST4 interface. It connects at the port (miss) marked "CCD".

The marking goes back to the days when the only auto guiders used CCDs and you paid a lot of cash (to SBIG) for them.

Like thousands of dollars.

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The ST4 interface is pure electrical - One pin is ground and the four directions (N/S/E/W) are on other pins. It is not a messsage-based

interface. It is the same electrical interface as the hand control for the Model 492 drive system. In fact, you can swap them.

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Now any autoguider camera you'll buy (typically under $200) comes with an ST4 connection and cable, plus a camera-specific

driver that will work with the popular (free) guiding software packages such as PhD2 via USB. The camera and guiding software

talk via USB messages but the mount itself is driven by the purely electrical signals of the ST4.

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PhD(2) lets you select an "On-Camera" option if your camera has a built in ST4 interface, as most autoguiders do now.?

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But, again, the mount itself doesn't have or need a driver.

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If you're happy with non-GOTO operation then go ahead. Just be aware that, like any used purchase, you may need

to do some maintenance and repairs. Thankfully Losmandy is very good about that.

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It will guide just fine with the tangent arm. In fact, the tangent arm should guide better than most worm drives because it should have minimal

backlash and a finer thread pitch.

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In the pre-GOTO days it was very common for even high end mounts (such as the early AstroPhysics) to have only

a tangent arm in DEC. I manually guided from 1965 thru around 2000 with a tangent arm DEC drive on Edmund (now I'm dating myself)

and Meade GEM mounts.

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Before the 1980's it wasn't uncommon for users to even have tangent arm drives on the RA axis.? A gent named Wolf here in ChicagoLand

sold them. The only other option at the time for fine pitch gearing was Ed Byers 6 and 8 inch worm drives from Barstow, California.

His offspring have restarted the business. At that time few could afford it.

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Some of the very early SCTs had large spur gears in RA instead of worm gears because of the cost. It was a big deal when Celestron started

offering Ed's gears on their deluxe models. Then Meade started offering their own (straight cut gear) models. And many of the earlier SCTs

had tangent arms in DEC.

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The economics of mounts along with the expectations of users have changed a lot since then.

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Have fun.

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Mark Christensen

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Generally all of the Losmandy mounts are similar and the needs for maintenance is very similar.??If you are using good grease which to me means Superlube with Teflon NLG1 grease, the pure synthetic oil base, NOT the silicone oil base, for thrust bearings, axle bearings, worms and worm gears OR the Losmandy supplied grease in the maintenance kit.? I would not do any lubrication of the the mount unless there is an issue with movement or noise.? When I say movement I mean tracking degrades or gets noticeably noisier on the correction graph, you can feel a change in smoothness of movement, and/or it becomes jerky when being manually pushed etc.? Noise means the lube is contaminated or the worm bearings are finished.? If you use translucent food grade lube like Superlube you can see a change in color or contamination in the grease then it may be time to degrease and relubricate.

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IME there is no reason to service the worm bearings of these mounts.? It is much more cost effective to just remove and replace them.? ??

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492DD systems….the only fail is the main switch! ? Pretty much. ? ? Losmandy still sells Digital drives and will support his old mounts.?

DD is much loved by many users who like push to and it will track very well. ?

As Homer poster a “Y” telephone splitter is needed for guiding (yes. Know you want visual….but that bug bites”!) . ?A forum search will show others using such. ?It’s basically a G11 so yeah it’ll be a steal for that price.

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cheers

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Brendan

On Wed, May 7, 2025 at 09:45 PM, plinthley wrote:

Thanks, it has the 492 controller.?

The Losmandy #492 is well known and not hard to find a good used example to put on the shelf as a backup if you are worried about its age. A complete working #492 system with controller, steppers and the simple hand controller can usually be found used for maybe $300 or less.?

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It is often cheaper to just buy a used backup system than to ship to a paid repair person and the backup is available immediately to test and diagnose any suspected issues.? This is what I would, actually have done in the past.? But IME it is rare that they fail and I never had to use my backup and I have other Losmandy mounts to use if it fails.? So after many years I just sold it.? I still have an great GM8s pluging away for visual with Astro Devices encoders and Nexus DSC.? It's my favorite visual mount and it can carry most any scope up to a M10"/C11.??

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Does the GM100 have a 360 or 180 tooth RA worm wheel? As along as the 492 works, it's fine, but parts are getting hard to find and unless you are handy, electronics repair is costly.? With simple tools and little skill one can build a OnStep based 492 controller replacement for $20 in parts. Want to gild the lily and encoders and and have push to guided by a planetarium map on a tablet. These mounts can last for gyrations. Just up date the electronics every couple decades. Some options.

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厂迟别辫蝉/°	Steps	?Steps	GR1	G2	TR
3600	48	1	150	180	1.25
7200	48	1	150	360	0.62
23680	400	32	3.7	180	0.48
25600	400	32	1	360	0.62
28800	48	4	150	360	0.37

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Thanks, it has the 492 controller.?

I have a Titan that I love but I'm curious about how often I should pull maintenance on the lubing of the RA/DEC gears.

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Kenn

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Not everyone needs or wants a GOTO system.? I know some folks like to use their steppers on Losmandy mounts in a direct drive configuration which has the advantage of slew speed and mounting simplicity. But the price is lower resolution and accuracy.??

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But in a non-GOTO system as the OP has chosen the standard #492 Digital Drive has much smoother movements due to the gearbox on the stepper.? One of the limitations of the original #492 was that the slew speed is low but for a Porter slip clutch mount designed for PUSH-TO operation this is perfect.??

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A direct drive stepper at best has 400 real steps per motor revolution.? The stock #492 geared stepper motors effectively have 3,600 steps per output shaft revolution or about 9 time the theoretical (I say this due to gearbox backlash, stepper resolution, quantum position etc.).? I don't think the OP can do better than what he has found for a purely visual use medium high capacity mount to sit on a pier.? And if you consider the price I doubt he could do better any time soon.??

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As I posted above the OP should jump on it.?

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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.

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The tangent arm limit the possibility of goto, but a well polar aligned mount doesn't need more then 15° of Dec correction.?

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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° step angle NEMA16 motors.?

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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.?

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Thanks, Brendan. I don't intend to image, so it should work out for me.?

But that is cheap and will do its job. ? I posted before thinking….again

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cheers?

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Brendan

The only drawback is it has a tangent arm on DEC so limited imaging ability?

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it’d cost too much to bring to a full DEC like G11. ?I’m only guessing?

cheers. ?FWIW?

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Brendan

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.

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Regards,

Daniel

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.

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?

Thanks for the info and confirmation George and Mark.?

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Avi?