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10" RC on a Losmandy G-11??

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#1 Jeff in Austin

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Posted 19 April 2011 - 06:27 PM

Ok, my question about the Atlas carrying the 10" RC has generated several responses on both sides. What about the G-11? It's rated for 60 lbs and the 10" RC is 34 lbs without imaging gear. Any concerns with this combination, or still too under-mounted??

#2 saadabbasi

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Posted 19 April 2011 - 06:59 PM

Based on my limited expierence with the ATRC8 and G11, I would not recommend it. Here my reasons:

While I have not lost an exposure to poor tracking, the weight of the ATRC8 + various accessories is quite a bit. I think wind is the biggest problem. With wind, the guiding graph in PHD is very rough (but I still manage to get round stars). Without wind, its much smoother. Typically within 1 pixel.

At first glance, the ATRC8 setup doesn't look that heavy. But I have a motorized moonlite focuser, OAG, filterwheel and a camera attached at one. This makes the scope very back heavy. I then needed to have a 2.5KG weight attached at the front of the scope. Without this additional weight, balance was impossible in declination.

I expect that with the ATRC10 you'll likely be exceeding the imaging capacity of the G11.

Note though, all of this entirely depends on your imaging scale. Unbinned, I have a scale of 0.62"/pixel. I'm glad my G11 is able to keep up at this scale *knock on wood*

I don't know if your camera's pixels will yield a lower imaging scale or not, but if it depends up around 1"/pixel or so, you'll have slightly more tolerance.

#3 David Lane

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Posted 19 April 2011 - 07:18 PM

I have a G11 and I think it would handle it with ease. Depends on what you add obviously but I think no problems with a G11.

#4 jrcrilly

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Posted 19 April 2011 - 07:19 PM

I'd feel pretty good about trying it on a G-11 - certainly more likely to please than the Atlas. The only firm data point I can offer is that an NJP does it very well! ;)

#5 Jeff in Austin

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Posted 19 April 2011 - 09:03 PM

Saad, I'm seeing the same thing with my AT8RC, I have to add the extra weight in the front to make it balance in DEC. I also see the wind effect show up on the tracking graph. But with that much wind, I usually pack it in anyway. I'm planning an 8300 based camera soon but I'll probably be 2x2 on an 10" RC.

I think you hit it on the head with "imaging capacity" but those values are top secret and unpublished. We hear the rule of thumb where imaging capacity is half of rated capacity but I tend to think some mounts do better than this estimate. I have no evidence to support this so that's the purpose of my questions, looking for others experiences.

#6 Jeff in Austin

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Posted 19 April 2011 - 09:07 PM

I have a G11 and I think it would handle it with ease. Depends on what you add obviously but I think no problems with a G11.


David, thank you. I see you also have the Titan...do you think that would be overkill for a 10" RC?

#7 Jeff in Austin

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Posted 19 April 2011 - 09:09 PM

I'd feel pretty good about trying it on a G-11 - certainly more likely to please than the Atlas. The only firm data point I can offer is that an NJP does it very well! ;)


John, what is the rating on the NJP? I can't seem to find it anywhere.

#8 jason_milani

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Posted 19 April 2011 - 09:18 PM

I think the NJP is rated around 70 lbs. I've seen John's and it's a beauty, but also a lot more expensive than a G-11. Takahashi rates their mounts conservatively as do most Japanese manufacturers.

#9 David Pavlich

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Posted 19 April 2011 - 09:21 PM

I have a G11 and I think it would handle it with ease. Depends on what you add obviously but I think no problems with a G11.


I agree. One of our imagers here, Dwight, used to produce some nice stuff with a 14" Meade LX200 on his G11. Unless you added some lead weights to the AT10RC, you wouldn't come close to the 70+ pounds of the 14" Meade.

David

#10 jrcrilly

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Posted 19 April 2011 - 09:39 PM

Takahashi rates their mounts conservatively as do most Japanese manufacturers.


Yes, The NJP rating is for imaging load; it's much beefier than a G-11 even though the stated ratings are similar. The EM-200 is rated at an honest 40 pounds and I'd put any imaging load on one of those that I'd put on a G-11.

That's a thought - with an OAG instead of a guidescope I bet an EM-200 would be a great AT10RC mount...

#11 mish

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Posted 19 April 2011 - 09:54 PM

Ok, my question about the Atlas carrying the 10" RC has generated several responses on both sides. What about the G-11? It's rated for 60 lbs and the 10" RC is 34 lbs without imaging gear. Any concerns with this combination, or still too under-mounted??


You should have no problems. The G11 handles loads well. I use a C11, two refractors, tube counterweights, a camera, and an LCD screen sitting on the G11, and the biggest problem I have is with seeing in the upper atmosphere, not with the mount on the ground.

#12 Rusty

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Posted 19 April 2011 - 11:12 PM

The NJP is rated at 55 lbs., but that's VERY conservative, even for imaging. With my imaging train on the not-svelte TOA-130S (around 40 lbs.), the mount makes the autoguider fall asleep, even in a wind.

I agree with jcrilly about the EM-200 (based on my experiences with others' -200s and my NJP). An alternative could be the CGEPro, but that's getting into EM-200/NJP price territory.

That said, careful balancing in all three axes can make a mount thought to be marginal actually serviceable.

And THAT said, an imaging train can't be overmounted...:grin:

#13 Tandum

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Posted 20 April 2011 - 08:30 AM

Lots of imagers down under are using the GSO RC10 on a G11 without issue. It seems all of them have replaced the focuser however.
I run an RC8 on my EM-200 and the results are fine. The 10 would be way too heavy for me.

#14 alpal

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Posted 20 April 2011 - 09:34 AM

All this talk about balancing a telescope -
tube counter-weights -
are people talking about a counter weight to the focuser & camera
on the other side of the OTA tube?

Also - putting the guide scope on the other side of the tube rings.

I often thought that the tube would tend to twist in one direction
without that which would cause tracking problems.

#15 Tandum

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Posted 20 April 2011 - 10:19 AM

These RC scopes are arse heavy and can be hard to balance. I do have a weight to hang off the front but here is how I got around it instead.
I think they made the tube too short, there is an acre of space hanging in the breeze out the back. I've since added another spacer out the back to rake the focuser in. Still it makes better pics than my vc200L which is its closest relative.

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