Hey Brian - Ain't ragging on the mount.? I love mine.? I have always used slow slew speeds as I think everything is happier that way.? I also use a higher voltage power supply.
All I'm sayin' is try it.? Throw a gearbox in the freezer and then report back (Pretty sure you all have a few lying around).

All the best,
Dave

On Thu, Feb 18, 2021 at 02:06 PM, <altuttle@...> wrote:

This is probably too involved, but I've been struggling for months with a decision and need some help.
?
I've been considering upgrading from my venerable CGE to a new mount... One that can carry more weight, and be less fussy with getting guiding smoothed out (I can get the old CGE down to?±1" but it's always a struggle).? My current setup is a permanent pier in a small observatory on a hilltop not far from home (totally off-grid though).? I'm at a fairly high latitude (~47deg) so I don't get too much imagining time.? In the winter snow prohibits access, and the summer nights are short.
As an aside I also have a GM8 which I use for traveling & lighter gear, so I'm familiar with Losmandy & Gemini1.?

I've been looking at the Paramount, 10Micron, and the AP offerings, and of those the AP mounts seem to suit my situation well.? However they are pricey, and each have their good & bad points from my POV.? Great modeling or pointing alignment is not critical to me....? I do AP and usually work only one target a night, so as long as the polar alignment remains good, my typical startup is very simple (with plate-solve now it's faster yet).

However, mount strength, stability, gear backlash & smoothness are very important, as are the reliability/robustness of the control system and computer interface.

So, all that said:? I'm thinking the G11T or even the G11G might be suitable for my needs.? I like the 75lb weight limit on the G11T but am a little worried with not having the spring loaded worms.? Would tracking/guiding performance be competitive with one of the AP mounts.? I've also read of some problems with the Gemini2.? Are they worked out now?? Although I'm always near the mount, I'm not where I could stop a runaway.?

Any comments to help with the decision would be greatly appreciated.
Thanks,
al

I'm familiar with a couple of older AP mounts and if money were no problem I'd buy an AP mount no question. But seeing how I am not rich, money is a problem and I'm also naturally cheap. So given the options out there IMO the only real choice without wining the lottery is a Losmandy mount if the payload capacity is going to work for your use.?

Many people commenting here will be coming from the place of having and using older Losmandy mounts, many purchased used myself included - mounts before the worms were carried in a one-piece assembly and spring loaded. I call these pre-enlightenment mounts Losmandy classic straight drivetrain mounts. There are also some hot-rodded versions with various upgrades and even a precursor Gen-1 OPW (One Piece Worm block) upgrade part which never made it into production mounts because at retail they added $700 to the cost of a Classic mount. This Gen-1 OPW was not sprung but was a superior design and?led to the simplified Gen-2 sprung OPW which traded a bit of geometric advantage for the much higher value advantage of consistent minimal backlash hot or cold AND much lower production cost. More than a fair trade IMO as it became standard on all mounts without a price increase.?

But the changes made around three years ago now - namely the tucked-in servo motors, spring-loaded Gen-2 OPWs, extending the RA and DEC and other detail changes have pushed the Losmandy GM8G and G11G into head to head competition with AP on the lower payload ranges. Suddenly a G11G was able to be used for imaging with similar PE results as similar AP mounts costing twice as much money similarly equipped. And the more compact lighter weight and lower payload GM8G has no competition in this payload class.? ??

I started out buying an older Losmandy G11 #492 digital drive and over the years I personally rebuilt, updated and upgraded to all the latest parts. I did this for several people, fellow club members, people I knew and even a few strangers or three met on web while?chasing better PE for imaging (which when it was good was incredibly good BTW - down in the 0.3" RMS range) and finally got to the point where the last and ultimate upgrades required Scott to do some machine work to install the last bit that propelled the G11G into the master class of mounts. This was the change over from the Classic straight 2-piece worm block drivetrain to the then new tucked-in servos and un-sprung Gen-2 OPWs which once the spring loaded design details were finalized were installed by Scott on a later trip back to the shop.?

So having said all that you know where I'm coming from and IMO?if $10,000 is a sum you can spend without thinking too much about it then IMO you should order a new AP Mach2 and a lot of accessories and be done with it. But do yourself a favor, while you are waiting for your AP Mach2 to come up in the AP lottery call Tanya up and buy a new Losmandy G11G to use while you are waiting the year or two for your number to come up on that AP Mach2. The G11G is a relatively inexpensive mount, easy to re-sell on the used market and you can image with a G11G right out of the box, just add counterweights and spend a few hours learning how the Gemini-2 works. In all honestly you will probably need to make a few adjustments to the spring pressure and worm adjustments but once you hit the right spot you won't touch them again. That part that Brian is always saying is true.?
?
--

Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

?

?

Hi Mark,

Good points.? Some thoughts...?a long email.??

Until now I have ignored the gearbox as an area that could "freeze up".? I just bought 2 new gearboxes at the factory this week. These are my first two brand new gearboxes.? I do live these days in a very benign climate that never freezes.? Denver is calling to me, however...

?In turning the output shaft of the new gearboxes by hand, at 78F temperature (a nice warm February day in Burbank!!!) the rotation was notably slow and viscous.? The new units have a cellophane type tape over the motor pinion gear entry port to prevent particles from entering, and prevent lube from flowing out on a hot day in storage.? My old gearboxes spin very loosely and freely by comparison.??

If you were in a freezing climate, could you clean that viscous lube out and put in Superlube, say??

Maybe a soak in alcohol or WD40 would dilute the internal grease, and you could easily pack in lighter Superlube.? The parts are plastic (ABS maybe?) Maybe brass and stainless?steel inside?? Can't use a harsh solvent like Berryman B-12 "Chemtool" as it might soften the plastic.? Can't insert anything in the gearbox that might leave a fiber or particle.??

My old gearboxes, all on used mounts,? had essentially zero lube left in them.? The gears spun freely and loosely.? I never got a new gearbox til now to tell they are intended to have lube packed inside.? I'd try the Superlube that is advertised, and astronomy tested, to go to very low temperature.??

The stock gearbox does not disassemble...it is sealed by rivets.? The McLennan gearboxes from Element14 do disassemble with 4 tiny flat head screws.? But not the McLennan gearboxes from RS components...those have a sealing paint over the assembly screws.? If you can disassemble the gearbox it helps in replacing the greases of course.?

____

Always experiments to try...some other notes...

____

On the possible overloading the worm bearings Mark raised:

On my G11 and GM8 worm bearings I use a single R4 Belleville spring washer (in each axis) to preload the axis (under the far worm bearing that I polish down til it will slide).? Fully compressed by hand (not crushed!) a single spring provides up to 7 pounds of axial force on both worm bearings and keeps the worm in position at the gearbox end bearing, at all temperatures.? ?But that's my mod...not the factory recommended component.??

If the worm blocks were compressed (say really super tight by using a C-clamp !) at daytime temperature, then bolted down hard,... then cooled down at night the aluminum contraction on the brass worm could really tighten down on the little R4ZZ bearings as you mention.? Aluminum expands and contracts slightly faster than brass... so the OPW or mounting flange would compress the worm bearings most at low temperature.

On the G11T, I asked at the factory how much to torque down the far 4-hole end screw that preloads the big Titan worm bearings (30 mm OD diameter bearings).? Mr Losmandy said..."just touch".? That is, screw in the endcap until? the cap just touches the bearing end.? I think that means put no torque on the screw cap.? That is for the Titan and G11T worm RA drives.? (See picture of that part.? In that photo I have a simple spanner wrench to tighten down the end cap....before getting the recommendation this week. ). I'll try that looser approach this coming week when I get home.??

Lots of factors to consider on the slippery road to perfection.? Every idea must get tested out to see how it improves or worsens PE.? What is the level you need for your imaging work?? Getting good tracking with autoguiding and maybe PEC too? Keep shooting!??

I'm very happy with my existing G11 and GM8 and GM811 mounts.? They have gotten down to about 1 to 1.5 arcsec RMS PE...with no PEC used.? That could go lower with PEC, and Brian urges the use of PEMpro to generate the PEC curve.? He reports excellent results on his mounts, and he goes a lot of imaging.??

But at present I'm working on a difficult case with a G11T mount, carrying a massive C14HD f/11 focal length like 3900 mm and piggyback 80 mm guide scope/finder scope on top.? (even with 0.7 FL reducer, the long FL and mass of scope and heavy counterweights is a tough challenge).? I'm getting good suggestions from the factory and other G11T and Atlas owners.? Some owners got very good PE results and I'll be happy to replicate their achievements.? ?When I get "there"...I'll let you know what worked in my case.?

Best,

Michael

On Thu, Feb 25, 2021, 7:46 AM Mark Christensen <mjcw500@...> wrote:

David,

Kudos for you doing this engineering experiment.

A friend is bringing over his Celestron AVX next week because it became unmovable in our last cold spell here in Northern Illinois.

I'm expecting to find frozen grease along with overtightened bearings and gears - he bought it used and I'm betting the prior owner overdid the backlash adjustment. That or the factory did in response to persistent complaints about backlash by customers who don't know how to work with less than perfect stuff. I've seen multiple mounts which had the RA and DEC bearing thrust pre-load nuts way too tight. I suspect the assemblers read the automotive spec for the bearings and used that pre-load.

The problem is rampant: Unsuitable grease installed by Sun Bathers in America and China. Same mentality that puts electronic parts only spec'ed to 0 deg C in telescope mounts, as Meade has done in the past.

A decade or so ago a friend of mine had to install heaters on the bearing housings of an early production Paramount because of grease and bearings seizing in the cold. It was installed (as it should be) in an unheated dome in western Michigan. I once installed a small 12V heater pad on a 120V synchronous motor such as we used in the old days pre-servo and stepper.

Things like this bring to mind the Eastern Front in the winter of 1941. Maybe the companies should hire a few engineers from Novosibirsk?

To me I'd worry about excessive wear on the first few gears, even if the mount functions as others have said.

But perhaps there is nothing to be done about it aside from keeping an eye on it.

Again, Kudos.

Mark Christensen

I am looking to setup an EAA rig for live stacking at outreach events (I am new to astrophotography). I am leaning toward using an autoguider to maximize the number of usable frames and allow for longer exposures (probably won’t want to go beyond 4 minutes at outreach events). I am considering getting a Losmandy mount for this setup. Based on the datasheets it appears that the GM811 and G11 have better unguided tracking performance than the GM8. Does this translate to significantly better tracking when guided? What would be a typical level of performance for each of these mounts when guided? Is it reasonable to expect sub-arcsecond performance from a guided GM8G?

David,

Kudos for you doing this engineering experiment.

A friend is bringing over his Celestron AVX next week because it became unmovable in our last cold spell here in Northern Illinois.

I'm expecting to find frozen grease along with overtightened bearings and gears - he bought it used and I'm betting the prior owner overdid the backlash adjustment. That or the factory did in response to persistent complaints about backlash by customers who don't know how to work with less than perfect stuff. I've seen multiple mounts which had the RA and DEC bearing thrust pre-load nuts way too tight. I suspect the assemblers read the automotive spec for the bearings and used that pre-load.

The problem is rampant: Unsuitable grease installed by Sun Bathers in America and China. Same mentality that puts electronic parts only spec'ed to 0 deg C in telescope mounts, as Meade has done in the past.

A decade or so ago a friend of mine had to install heaters on the bearing housings of an early production Paramount because of grease and bearings seizing in the cold. It was installed (as it should be) in an unheated dome in western Michigan. I once installed a small 12V heater pad on a 120V synchronous motor such as we used in the old days pre-servo and stepper.

Things like this bring to mind the Eastern Front in the winter of 1941. Maybe the companies should hire a few engineers from Novosibirsk?

To me I'd worry about excessive wear on the first few gears, even if the mount functions as others have said.

But perhaps there is nothing to be done about it aside from keeping an eye on it.

Again, Kudos.

Mark Christensen