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IS THERE SOME FALSE INFO ON THE GM 11 PRE 2000YEAR SUPPORT!

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#1 DanPB

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Posted 18 May 2009 - 03:37 PM

I have an ad for my Losmandy G11 EQ Mount with HD Tripod on this site. I have had numerous email stating that this mount will NOT support a particular 6" refractor due to scopes LENGTH .
I called Losmandy and spoke to Scott Losmandy himself who refers any/all questions about how much this mount I am selling(G11-pre year 2000) will support without wobbles, misses, gasps, unbalance whatever due to length.
Please direct any misgivings to Losmandy Tech Support@Jim who is familiar with my problem.
I have had the AP 4,5,6 " refractors on, a 10, 12, SCT on the mount/drive AND have had both a 4"refractor and a 5" SCT on dual scope plate for Hale-Bopp and not 1 problem. Also "piggybacked refractors whose length was well over 4-5'ft.
I am not sure who is and what thread this misinformation is being posted on here on CN but it is not factual in any case I or Losmandy is aware of.
Thanks!
Dan :confused:


#2 RogerRZ

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Posted 18 May 2009 - 04:41 PM

A 16" SCT on a G11? Looks nice, but I'll pass...

Losmandy quotes a 60lbs capacity for the G11, and a bare 16" weighs at least 75lbs, with no finder, diagonal, eyepiece, dew shield/heater.

I've had a 6" f/8 refractor on an EQ6/AMD saddle setup, and for my likes, it was borderline undermounted. Some people say it's fine on a LXD55. Go figure...

#3 LLEEGE

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Posted 18 May 2009 - 04:48 PM

I had my TEC160 on a late model G-11. It was borderline.

#4 jrcrilly

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Posted 18 May 2009 - 05:48 PM

I have had the AP 4,5,6 " refractors on, a 10, 12, 16" SCT on the mount/drive AND have had both a 4"refractor and a 5" SCT on dual scope plate for Hale-Bopp and not 1 problem. Also "piggybacked refractors whose length was well over 4-5'ft.
I am not sure who is and what thread this misinformation is being posted on here on CN but it is not factual in any case I or Losmandy is aware of.


Different folks have differing tolerances for stability and settledown time. That said, none of the loads mentioned above are anywhere near the load class of a 6" F/15 refractor (except the 16" SCT - and that claim I don't believe. The only 16" SCT with which I'm familiar runs way over 100 pounds and would be a joke on a G11-class mount). A mount that can handle refractors 6 feet in length could well have big problems with one 9 feet in length.

#5 DanPB

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Posted 18 May 2009 - 06:04 PM

The 16" SCT post was in error sorry for that. We are not talking about WEIGHT here. BUT the G-11 WILL handle over 60lbs pretty ok. I am 62yrs young and have seen more years of astronomy than I care to remember(age wise only, viewing...wow!) but I do. I have NOT seen an instance on the G-11 of length a determining factor in the slewing of the scope unless pointed in a downward manuveur.From 180degress horizon to horizon never.
But I could and have been wrong and others may have seen this.

#6 jrcrilly

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Posted 18 May 2009 - 06:13 PM

I have NOT seen an instance on the G-11 of length a determining factor in the slewing of the scope unless pointed in a downward manuveur.From 180degress horizon to horizon never.


Slewing's not a problem. Holding the thing still is the hard part. ;)

#7 LLEEGE

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Posted 18 May 2009 - 07:33 PM

And stopping a slew.

#8 RogerRZ

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Posted 18 May 2009 - 07:58 PM

And focusing at 200x.

#9 Charlie Hein

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Posted 19 May 2009 - 08:31 AM

I don't remember seeing the thread you're referring to Dan - hopefully someone will chime in if they remember it.

#10 rsbfoto

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Posted 19 May 2009 - 10:43 AM

I have an ad for my Losmandy G11 EQ Mount with HD Tripod on this site. I have had numerous email stating that this mount will NOT support a particular 6" refractor due to scopes LENGTH .
I called Losmandy and spoke to Scott Losmandy himself who refers any/all questions about how much this mount I am selling(G11-pre year 2000) will support without wobbles, misses, gasps, unbalance whatever due to length.
Please direct any misgivings to Losmandy Tech Support@Jim who is familiar with my problem.
I have had the AP 4,5,6 " refractors on, a 10, 12, SCT on the mount/drive AND have had both a 4"refractor and a 5" SCT on dual scope plate for Hale-Bopp and not 1 problem. Also "piggybacked refractors whose length was well over 4-5'ft.
I am not sure who is and what thread this misinformation is being posted on here on CN but it is not factual in any case I or Losmandy is aware of.
Thanks!
Dan :confused:


Hi Dan,

You are misunderstanding the whole enchilada. The main problem is as many others already said that the moment of inertia produced by such a long telescope. Any slight breeze will move the scope and so the mount.

I have a Mewlon 250 and FS-78 on a G11 and that means about 66pounds of equipment + 66 pounds of counterweight. The Mewlon 250 is quite short with 800mm and even protected by the walls of an Observatory when a slight wind is blowing I can see it in my guider scope.

So and coming now to the talk of Scott Losmandy do not forget he is a sales man :grin:

#11 rsbfoto

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Posted 19 May 2009 - 10:46 AM

I don't remember seeing the thread you're referring to Dan - hopefully someone will chime in if they remember it.


Hi,

I think he means this one

#12 Charlie Hein

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Posted 19 May 2009 - 12:05 PM

Ahhh, I see. I don't venture into the refractor forum very often.

Charlie

#13 jrbarnett

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Posted 19 May 2009 - 12:19 PM

I believe the advice you're referring to was that a 6" f/15 achromat would not be happy on a G-11. Short OTAs like SCTs (even big ones) and medium length OTAs like 5" and 6" APO refractors, are much easier for a mount to manage than a very long OTA as a 6" f/15 would be.

On the advice of D&G I initially mounted my old 5" f/10 D&G Achromat on a Losmandy GM-8. In my opinion, despite the scope maker's suggestion and Losmandy's loading specifications for the GM-8, that combination was not optimal and in fact barely adequate to me.

A 5" f/10 is a much shorter scope than a 6" f/15, and while the G-11 is a much larger mount than the GM-8, the advice to the effect that the G-11 would not be adequate sounds correct to me. I would hate to have someone do as I did and purchase a Losmandy mount "by the numbers" only too be disappointed by its inability to handle the demands of a large moment arm.

I happily use the GM-8 with shorter OTAs. It is a good mount and a good value for the cost, but based on my experiences with the GM-8 + 5" f/10 combination would not buy a G-11 for a 6" f/15 achromat.

Regards,

Jim

#14 Svezda

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Posted 26 May 2009 - 09:50 AM

I have NOT seen an instance on the G-11 of length a determining factor in the slewing of the scope unless pointed in a downward manuveur.From 180degress horizon to horizon never.


Slewing's not a problem. Holding the thing still is the hard part. ;)

That's my experience. I was trying to use a big 8" f/6 Newt. (heavy duty Parallax OTA - about 45-48 pounds loaded with rings, big eyepiece, finder, radial tube balance weight, etc.). One of the first times I was using it the Losmandy G-11 gave me a scare when something moved very obviously, like a shift in balance and I didn't know what it was. At first it wasn't obvious what was happening, but it turned out that it was the mount-to-tripod connection holes which were allowing the mount/scope combination as a whole to slip around within the holes. They designed these holes very poorly. Instead of threaded holes in the tripod accepting the threaded hand knobs (holes for which do have threads in the mount part, obviously), the holes are not threaded but rely simply on your hand strength to be able to tighten the knobs enough to press the knob's washer up against the outside wall of the tripod. Not only that, but the holes aren't even holes - they are elongated slots, which appear to have been made that way in order to make the tolerance in lining up the knobs from mount to tripod easier. This works 'ok' for loads up to about 25-30 pounds but I can't use the G-11 for scopes heavier than that. Possibly I will see if I can get a machinist to make me some proper threaded holes at the same height but slightly offset radially from the original holes, but the work piece (the tripod) is oddly shaped and it might be difficult to machine. Any suggestions?






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