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Anyone use a big OTA on a GM-8?

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#1 Lane

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Posted 25 October 2012 - 04:20 PM

I am on a never ending search for a very quiet mount to use when I am camping in parks. I realized on my last vacation that even my very quiet Orion Sirius is still to loud.

I remember using a Tak 102 on a GM-8 one night many years ago, it had no goto just tracking and DSC's which is exactly what I need. If I remember correctly it was noise free. What I don't know is whether it could handle my C11 or my AT152. I would be using the vibration pads Losmandy sells and would want 2 seconds or less of vibration damping time.

#2 WadeH237

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Posted 25 October 2012 - 06:24 PM

Have you considered an Atlas? I don't know how much noise a GM-8 makes, but the Atlas is very quiet. It makes a very soft whine that is unlike any other mount I've heard. Every time I see one slew, it amazes me how little noise it makes. Also, it would be able to handle your OTAs.

-Wade

#3 mdowns

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Posted 25 October 2012 - 09:22 PM

I used to have a non-goto gm8 and I mounted a meade 10" sct on it.Though I felt it maxed the mount out the gm8 performed perfectly with the load.I'd wager that the meade 10" with its internal weights was every bit as heavy as the c11 I have now.Good luck!

#4 Mirzam

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Posted 26 October 2012 - 06:28 AM

The nice thing about a GM-8 is that it is clutched. If you don't want goto capabilities a clutched mount is much more convenient than loosening and tightening shaft locks every time you move the scope.

JimC

#5 RAKing

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Posted 26 October 2012 - 02:57 PM

I used a C925 and a TMB 130 on my GM-8, but I think anything bigger might be pushing it a bit too much.

My Atlas was the quietest mount I owned.

Cheers,

Ron

#6 hottr6

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Posted 26 October 2012 - 03:37 PM

Biggest I have used is a 4" f/13, and the G8 manages it.... barely. That tube is loooooong.

#7 Gord

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Posted 26 October 2012 - 06:59 PM

I must be more tolerant than most... I don't have a G8, but have many others. The G8 is like a scaled down G11.

The G8 is a step up from the CG-5's, and those have been used to carry 6" refractors (F8), C11's, and even the C10. I have much experience with the C10. Not ideal, but it will work on the EQ5. A G8 would be a cake walk by comparison.

I would expect the G8 to be very quiet. More so than an Atlas I would imagine since the Atlas has to make some noise when the motors are slewing.

I have the EQ6 and it's silent. The G11 is mostly as well. There is a little noise from the motors (gearboxes I think...) in my very old sample that is known about them. I think the newer ones don't have that.

And with clutches, you can just swing the thing whereever you want as fast as you want, and no noise. The noise of the motors was one of the things I didn't like about the AS-GT.

Clear skies,

#8 jrbarnett

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Posted 26 October 2012 - 07:19 PM

I used a 5" f/10 D&G on a GM-8. IMO the mount was not up to the mass plus moment arm of that OTA (visual use). The weakest link of the GM-8 is a somewhat flimsy tripod. If you move the head to a G-11 tripod, it's a much more capable mount.

The non-Gemini GM-8 is indeed a very quiet mount, though. If stealth mode is you thing, it might be a good choice, though honestly for just a little bit more you can get the non-Gemini G-11 which is a much better mount, and also silent as they come.

- Jim

#9 Lane

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Posted 27 October 2012 - 01:06 AM

Thanks guys,

I guess I will go with a G11 instead because it sounds like it is probably a better match for these scopes, I was trying to get as portable as possible, which is why I was thinking G8. The whole point here is camping out and I carry a lot of other junk with me on vacations.

The Atlas is just as loud as the Sirius when slewing around. They are both quiet compared to most other mounts but they are still to loud for some of the parks I camp at. They just don't put enough distant between the campsites in most parks, especially in national parks. So what I want is something that is push-to instead of go-to, so the only noise heard will be the tracking motors.

I was originally thinking about a DiscMount DM8 with the DSC's, but I think I would miss the tracking especially at high powers.

#10 Cabrillas

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Posted 27 October 2012 - 03:17 PM

I had a TEC 140 on a GM8 (Gemini), only for visual. It was a very stable setup, even under moderate winds. Better than my TEC 160ED (looong tube)on the G11.

Carlos.

#11 CityAstronomer

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Posted 29 October 2012 - 10:35 PM

Carlos,

I am looking at the GM-8 as a portable EQ mount to hold a future Tec 140 purchase. What tripod are you using to keep the scope stable?

Sam

#12 blueman

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Posted 29 October 2012 - 11:19 PM

I have not put the TEC 140 on my GM-8, mainly because I use the NP-101 on it. But I am sure that it would handle it for visual.
Blueman

#13 Lane

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Posted 30 October 2012 - 01:50 PM

I have been emailing with Ed at DeepSpaceProducts about the T-Rex mount. I am thinking that is going to be a better way to go than a GM-8 or a G11 for my purposes. Scott says a 6" like my AT152 or the C11 will not be a problem at all on the T-Rex. I have also discovered that the Sky Commander is totally compatible with SKY-FI, so I can use Sky Safari on my iPad to find objects. I don't like the 3K price tag much, but the T-Rex appears to be a lot more Grab-n-Go than the GM-8 or the G11.

#14 Cabrillas

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Posted 30 October 2012 - 04:16 PM

Carlos,

I am looking at the GM-8 as a portable EQ mount to hold a future Tec 140 purchase. What tripod are you using to keep the scope stable?

Sam


Hi Sam.

It was the standard GM8 folding tripod. About portability...well, of course a lot more portable than the G11, but it takes two trips (head, tripod, counterweights), at least for average people.

Carlos.






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