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Re: Photographic Load Capacity for G8 Mount


Jul 23, 2010

 


----------------------------

#46523 Jul 23, 2010

Jim,



I can only tell you my experience. My GM-8 had some difficulty handling a Celestron 9.25 inch SCT. It was ok visually but it was clear the scope was a bit much for the mount. It only weighed 20lbs but the length plus being heavy at the ends made it a bit unsteady. I have imaged very successfully with a setup weighting 20 lbs at a focal length of 660 mm. My current set up weights about 18 lbs and the focal length is 735 mm, and I am very happy with it. I get a few frames with bad tracking, but I think that might be due to a misalignment between the gearbox and worm. Because of the misalignment I am going to add the one piece worm block for the GM-8 when it becomes available about mid August.



Here is my opinion of the bottom line on the weight issue. The mount can probably do over 30 lbs visually even with a big scope, but for astrophotography, I believe the limiting factors are both weight and focal length. Here is my best guess. The GM-8 can handle more weigh than 20 lbs at focal lengths of less than 700 mm, or it can go to longer focal lengths if you keep the weight down to 20 lbs or less. Of course bigger scopes with longer focal lengths are going to weigh more. My original scope was a 110 mm refractor that weighed 11 lbs. My current scope is a Stellervue 105 mm carbon fiber Raptor that weighs less than 10 lbs. My guess is that a 115 mm refractor might be pushing things a bit and almost certainly 120 mm is too much for astrophotography. It would be good to hear from someone who has some experience with that size scope on the GM-8.



Later this year I am going to sell my Meade 8 inch SCT and buy a Celestron 8 inch Edge SCT. I suspect that the total weight will be about 22 lbs with everything on the mount. I suspect that with out a focal reducer the mount would be over its limit, more because of the 2000 mm focal length than the weight. However, reduced to 1000 mm and at 22 lbs I suspect the mount will do fine, especially after adding the one piece worm block.



One further consideration is the tripod that comes with the GM-8. In order to have a stiffer setup I ordered the Losmandy 12 inch pillar for the tripod. With the pillar, I only have to extend the legs far enough to level the mount. This arrangement is plenty stiff, and I would recommend it to any one with the GM-8 tripod, especially if they are considering a heaver setup.



Steve

----- Original Message -----

From: jwaters125

To: Losmandy_users@yahoogroups.com

Sent: Friday, July 23, 2010 12:53 PM

Subject: [Losmandy_users] Photographic Load Capacity for G8 Mount







What's the upper limit on the photographic weight capacity for a G8 mount? I have been told not to go past 20 pounds. I have also been told that scopes past 28" are problematic due to oscillations. Is this true?



Jim











[Non-text portions of this message have been removed]



----------------------------

#46524 Jul 23, 2010

I have an 8 inch vixen RSS and visually it is okay but not photographically. It does not weigh that much either and is short. Around 10 pounds. I have a Takahashi FS 102, and it is marginal photographically. I am going to try a maxim motor on the declamation due to the long telescope. The G. 11 is much more robust. ----- Original Message -----

From: Steve

To: Losmandy_users@yahoogroups.com

Sent: Friday, July 23, 2010 5:39 PM

Subject: Re: [Losmandy_users] Photographic Load Capacity for G8 Mount







Jim,



I can only tell you my experience. My GM-8 had some difficulty handling a Celestron 9.25 inch SCT. It was ok visually but it was clear the scope was a bit much for the mount. It only weighed 20lbs but the length plus being heavy at the ends made it a bit unsteady. I have imaged very successfully with a setup weighting 20 lbs at a focal length of 660 mm. My current set up weights about 18 lbs and the focal length is 735 mm, and I am very happy with it. I get a few frames with bad tracking, but I think that might be due to a misalignment between the gearbox and worm. Because of the misalignment I am going to add the one piece worm block for the GM-8 when it becomes available about mid August.



Here is my opinion of the bottom line on the weight issue. The mount can probably do over 30 lbs visually even with a big scope, but for astrophotography, I believe the limiting factors are both weight and focal length. Here is my best guess. The GM-8 can handle more weigh than 20 lbs at focal lengths of less than 700 mm, or it can go to longer focal lengths if you keep the weight down to 20 lbs or less. Of course bigger scopes with longer focal lengths are going to weigh more. My original scope was a 110 mm refractor that weighed 11 lbs. My current scope is a Stellervue 105 mm carbon fiber Raptor that weighs less than 10 lbs. My guess is that a 115 mm refractor might be pushing things a bit and almost certainly 120 mm is too much for astrophotography. It would be good to hear from someone who has some experience with that size scope on the GM-8.



Later this year I am going to sell my Meade 8 inch SCT and buy a Celestron 8 inch Edge SCT. I suspect that the total weight will be about 22 lbs with everything on the mount. I suspect that with out a focal reducer the mount would be over its limit, more because of the 2000 mm focal length than the weight. However, reduced to 1000 mm and at 22 lbs I suspect the mount will do fine, especially after adding the one piece worm block.



One further consideration is the tripod that comes with the GM-8. In order to have a stiffer setup I ordered the Losmandy 12 inch pillar for the tripod. With the pillar, I only have to extend the legs far enough to level the mount. This arrangement is plenty stiff, and I would recommend it to any one with the GM-8 tripod, especially if they are considering a heaver setup.



Steve



----- Original Message -----

From: jwaters125

To: Losmandy_users@yahoogroups.com

Sent: Friday, July 23, 2010 12:53 PM

Subject: [Losmandy_users] Photographic Load Capacity for G8 Mount



What's the upper limit on the photographic weight capacity for a G8 mount? I have been told not to go past 20 pounds. I have also been told that scopes past 28" are problematic due to oscillations. Is this true?



Jim



[Non-text portions of this message have been removed]











[Non-text portions of this message have been removed]







----------------------------

#46525 Jul 23, 2010

I mount my Intest Micro Alter M603 on a Losmandy GM8 and use it for

astrophotography. This scope is an F10 at 1500mm focal length and

weighs about 13lb including scope, camera and guidescope. If I don't

guide I can reach 2 minute exposures before trailing is too much of a

problem. If I autoguide I can expose to 20 minutes without a problem

but I think I'm about at the limit at this focal length. Balancing is

absolutely crucial to prevent guiding problems and I generally find

that the use of a focal reducer to bring the f-ratio down to about 6.3

makes things much easier. While some people say you can go to 20lb

photographically I think it would have to be a fairly fast scope to

make it worthwhile. I think it's best not to go above 15lb. When

calculating your payload you don't need to include the counterweights.



Regards



Simon



On 24 Jul 2010, at 01:08, " Scott Mefferd" smff@...> wrote:



> I have an 8 inch vixen RSS and visually it is okay but not

> photographically. It does not weigh that much either and is short.

> Around 10 pounds. I have a Takahashi FS 102, and it is marginal

> photographically. I am going to try a maxim motor on the declamation

> due to the long telescope. The G. 11 is much more robust.

> ----- Original Message -----

> From: Steve

> To: Losmandy_users@yahoogroups.com

> Sent: Friday, July 23, 2010 5:39 PM

> Subject: Re: [Losmandy_users] Photographic Load Capacity for G8 Mount

>

> Jim,

>

> I can only tell you my experience. My GM-8 had some difficulty

> handling a Celestron 9.25 inch SCT. It was ok visually but it was

> clear the scope was a bit much for the mount. It only weighed 20lbs

> but the length plus being heavy at the ends made it a bit unsteady.

> I have imaged very successfully with a setup weighting 20 lbs at a

> focal length of 660 mm. My current set up weights about 18 lbs and

> the focal length is 735 mm, and I am very happy with it. I get a few

> frames with bad tracking, but I think that might be due to a

> misalignment between the gearbox and worm. Because of the

> misalignment I am going to add the one piece worm block for the GM-8

> when it becomes available about mid August.

>

> Here is my opinion of the bottom line on the weight issue. The mount

> can probably do over 30 lbs visually even with a big scope, but for

> astrophotography, I believe the limiting factors are both weight and

> focal length. Here is my best guess. The GM-8 can handle more weigh

> than 20 lbs at focal lengths of less than 700 mm, or it can go to

> longer focal lengths if you keep the weight down to 20 lbs or less.

> Of course bigger scopes with longer focal lengths are going to weigh

> more. My original scope was a 110 mm refractor that weighed 11 lbs.

> My current scope is a Stellervue 105 mm carbon fiber Raptor that

> weighs less than 10 lbs. My guess is that a 115 mm refractor might

> be pushing things a bit and almost certainly 120 mm is too much for

> astrophotography. It would be good to hear from someone who has some

> experience with that size scope on the GM-8.

>

> Later this year I am going to sell my Meade 8 inch SCT and buy a

> Celestron 8 inch Edge SCT. I suspect that the total weight will be

> about 22 lbs with everything on the mount. I suspect that with out a

> focal reducer the mount would be over its limit, more because of the

> 2000 mm focal length than the weight. However, reduced to 1000 mm

> and at 22 lbs I suspect the mount will do fine, especially after

> adding the one piece worm block.

>

> One further consideration is the tripod that comes with the GM-8. In

> order to have a stiffer setup I ordered the Losmandy 12 inch pillar

> for the tripod. With the pillar, I only have to extend the legs far

> enough to level the mount. This arrangement is plenty stiff, and I

> would recommend it to any one with the GM-8 tripod, especially if

> they are considering a heaver setup.

>

> Steve

>

> ----- Original Message -----

> From: jwaters125

> To: Losmandy_users@yahoogroups.com

> Sent: Friday, July 23, 2010 12:53 PM

> Subject: [Losmandy_users] Photographic Load Capacity for G8 Mount

>

> What's the upper limit on the photographic weight capacity for a G8

> mount? I have been told not to go past 20 pounds. I have also been

> told that scopes past 28" are problematic due to oscillations. Is

> this true?

>

> Jim

>

> [Non-text portions of this message have been removed]

>

> [Non-text portions of this message have been removed]

>

>





[Non-text portions of this message have been removed]



----------------------------

#46528 Jul 26, 2010

Did you try the HD tripod with your g8/9.25? That's a recommended intermediate measure to get more stability.



I've always thought that the price increase for the G11 was such that people with any doubts at all should go for the G11.



regards

Greg N

--- In Losmandy_users@yahoogroups.com, "Steve" bullfox@...> wrote:

>

> Jim,

>

> I can only tell you my experience. My GM-8 had some difficulty handling a Celestron 9.25 inch SCT. It was ok visually but it was clear the scope was a bit much for the mount. It only weighed 20lbs but the length plus being heavy at the ends made it a bit unsteady. I have imaged very successfully with a setup weighting 20 lbs at a focal length of 660 mm. My current set up weights about 18 lbs and the focal length is 735 mm, and I am very happy with it. I get a few frames with bad tracking, but I think that might be due to a misalignment between the gearbox and worm. Because of the misalignment I am going to add the one piece worm block for the GM-8 when it becomes available about mid August.

>

> Here is my opinion of the bottom line on the weight issue. The mount can probably do over 30 lbs visually even with a big scope, but for astrophotography, I believe the limiting factors are both weight and focal length. Here is my best guess. The GM-8 can handle more weigh than 20 lbs at focal lengths of less than 700 mm, or it can go to longer focal lengths if you keep the weight down to 20 lbs or less. Of course bigger scopes with longer focal lengths are going to weigh more. My original scope was a 110 mm refractor that weighed 11 lbs. My current scope is a Stellervue 105 mm carbon fiber Raptor that weighs less than 10 lbs. My guess is that a 115 mm refractor might be pushing things a bit and almost certainly 120 mm is too much for astrophotography. It would be good to hear from someone who has some experience with that size scope on the GM-8.

>

> Later this year I am going to sell my Meade 8 inch SCT and buy a Celestron 8 inch Edge SCT. I suspect that the total weight will be about 22 lbs with everything on the mount. I suspect that with out a focal reducer the mount would be over its limit, more because of the 2000 mm focal length than the weight. However, reduced to 1000 mm and at 22 lbs I suspect the mount will do fine, especially after adding the one piece worm block.

>

> One further consideration is the tripod that comes with the GM-8. In order to have a stiffer setup I ordered the Losmandy 12 inch pillar for the tripod. With the pillar, I only have to extend the legs far enough to level the mount. This arrangement is plenty stiff, and I would recommend it to any one with the GM-8 tripod, especially if they are considering a heaver setup.

>

> Steve

>

> ----- Original Message -----

> From: jwaters125

> To: Losmandy_users@yahoogroups.com

> Sent: Friday, July 23, 2010 12:53 PM

> Subject: [Losmandy_users] Photographic Load Capacity for G8 Mount

>

>

>

> What's the upper limit on the photographic weight capacity for a G8 mount? I have been told not to go past 20 pounds. I have also been told that scopes past 28" are problematic due to oscillations. Is this true?

>

> Jim

>

>

>

>

>

> [Non-text portions of this message have been removed]

>







----------------------------

#46529 Jul 26, 2010

Greg,



My main reason for sticking with the GM-8 is portability. I rarely observe in my back yard and almost always go out to a dark sky site. I am retired and I want to go along time before the equipment gets too heavy for me to deal with. The problem with the 9.25 is that the extra inertia of the scope made go to's unreliable. The tripod, the way I have it set up, is not a problem, as far as I can tell. I tend to go with what looks right, and the 9.25 just looked too big for the mount. The other reason is that the GM-8 does the job adequately at the weights and focal lengths I am using. However, I do loose a small percentage of subs due to bad tracking, and I am hoping the one piece worm block will help with that problem.



Steve ----- Original Message -----

From: gnowellsct

To: Losmandy_users@yahoogroups.com

Sent: Monday, July 26, 2010 1:39 PM

Subject: [Losmandy_users] Re: Photographic Load Capacity for G8 Mount







Did you try the HD tripod with your g8/9.25? That's a recommended intermediate measure to get more stability.



I've always thought that the price increase for the G11 was such that people with any doubts at all should go for the G11.



regards

Greg N



--- In Losmandy_users@yahoogroups.com, "Steve" bullfox@...> wrote:

>

> Jim,

>

> I can only tell you my experience. My GM-8 had some difficulty handling a Celestron 9.25 inch SCT. It was ok visually but it was clear the scope was a bit much for the mount. It only weighed 20lbs but the length plus being heavy at the ends made it a bit unsteady. I have imaged very successfully with a setup weighting 20 lbs at a focal length of 660 mm. My current set up weights about 18 lbs and the focal length is 735 mm, and I am very happy with it. I get a few frames with bad tracking, but I think that might be due to a misalignment between the gearbox and worm. Because of the misalignment I am going to add the one piece worm block for the GM-8 when it becomes available about mid August.

>

> Here is my opinion of the bottom line on the weight issue. The mount can probably do over 30 lbs visually even with a big scope, but for astrophotography, I believe the limiting factors are both weight and focal length. Here is my best guess. The GM-8 can handle more weigh than 20 lbs at focal lengths of less than 700 mm, or it can go to longer focal lengths if you keep the weight down to 20 lbs or less. Of course bigger scopes with longer focal lengths are going to weigh more. My original scope was a 110 mm refractor that weighed 11 lbs. My current scope is a Stellervue 105 mm carbon fiber Raptor that weighs less than 10 lbs. My guess is that a 115 mm refractor might be pushing things a bit and almost certainly 120 mm is too much for astrophotography. It would be good to hear from someone who has some experience with that size scope on the GM-8.

>

> Later this year I am going to sell my Meade 8 inch SCT and buy a Celestron 8 inch Edge SCT. I suspect that the total weight will be about 22 lbs with everything on the mount. I suspect that with out a focal reducer the mount would be over its limit, more because of the 2000 mm focal length than the weight. However, reduced to 1000 mm and at 22 lbs I suspect the mount will do fine, especially after adding the one piece worm block.

>

> One further consideration is the tripod that comes with the GM-8. In order to have a stiffer setup I ordered the Losmandy 12 inch pillar for the tripod. With the pillar, I only have to extend the legs far enough to level the mount. This arrangement is plenty stiff, and I would recommend it to any one with the GM-8 tripod, especially if they are considering a heaver setup.

>

> Steve

>

> ----- Original Message -----

> From: jwaters125

> To: Losmandy_users@yahoogroups.com

> Sent: Friday, July 23, 2010 12:53 PM

> Subject: [Losmandy_users] Photographic Load Capacity for G8 Mount

>

>

>

> What's the upper limit on the photographic weight capacity for a G8 mount? I have been told not to go past 20 pounds. I have also been told that scopes past 28" are problematic due to oscillations. Is this true?

>

> Jim

>

>

>

>

>

> [Non-text portions of this message have been removed]

>











[Non-text portions of this message have been removed]



----------------------------

#46552 Jul 29, 2010

My results have been mixed using Orion 8" RC (1630 fl) with Stellarvue F60 as guidescope , heavy SBIG ST-6B , and G11 tripod. Careful attention must be applied to balancing, even then, pointing toward nadir results in slightly elongated stars. Photometry is primary use.



The selling point of the GM-8 is its accuracy for the price range and portability. No regrets since it is so portable. I must set-up each session. Being able to move the mount/tripod (with counter weights removed) as one item from inside my shed to outside is quite a convenience.



Bottom-line: Concur with others that 20 lbs is about the max for photographic capacity. Less photographic capacity if looking toward nadir. Attention required for adequate balancing.



[Non-text portions of this message have been removed]



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