Tim A.
professor emeritus
Reged: 09/19/07
Posts: 663
Loc: 40 30'N 105 3'W
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I have a CR150-HD, a nice 6" f/8 achromat on a CG5-GT mount. I have to take care to keep my eye off the EP to afford the most stable views. I've been wondering if a longer dovetail bar might make things more rigid. The stock dovetail is 13", and the longest replacement I've seen is the AstroTech 15" dovetail bar.
Would the extra dovetail length make any difference?
-- Tim
Colorado
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Tim -- Colorado
12.5" f/5 Dob (Starbucket)
Celestron CPC800
Celestron CR-150 HD on CG5-GT
Galileoscope
Oberwerk Deluxe II 20x80 & Ultra 10x50
Celestron Regal LX 8x42
Bio-binoculars 1x6
"Me? Crazy? Oh, yeah. Crazy like an ox!"
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Karl_Bonner_1982
sage
Reged: 05/13/09
Posts: 442
Loc: Springfield, Oregon (4.5ish ma...
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The three main factors are tube weight, tube length and distribution of weight. A compact tube with an even weight distribution will be more stable than a long skinny tube that's heavy at both ends.
I'm beginning to think that my Meade-2 mount is a little weak for the Mak...or maybe the bearings are just a bit loose?
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Current equipment:
Orion 8x40 fully coated binocs
Orion 90mm f/10 achro refractor
Celestron 102mm f/5 rich field refractor
Eyepieces: 25, 20, 12.5, 10, 7.5 (all plossls), borrowing 40mm Plossl and 2x shorty barlow
"We're here, we love refractors, get used to it!"
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stevew
Pooh-Bah
Reged: 03/03/06
Posts: 1356
Loc: Vancouver
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Quote:
The stock dovetail is 13", and the longest replacement I've seen is the AstroTech 15" dovetail bar.
Would the extra dovetail length make any difference?
-- Tim
Colorado
A 2 inch longer dove tail would make no difference.
Try a bigger mount, or just stronger legs on your CG5 mount.
Steve
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So long, and thanks for all the fish....
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CHASLX200
Carpal Tunnel
Reged: 09/29/07
Posts: 2094
Loc: Tampa area Florida
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The CG5 will never be any good for a 6" F8 Achro. You need a bigger mount like the G11.
Chas
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Luigi
Postmaster
Reged: 07/03/07
Posts: 5272
Loc: MA
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A longer dovetail can be counterproductive. The dovetail flexes more than the tube of the telescope and a longer one will flex even more easily. Shortening the distance between the tube rings will help, as will getting a stiffer dovetail. Better yet, do both.
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17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha.
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins
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Phil Cowell
professor emeritus
Reged: 05/24/07
Posts: 520
Loc: Southern Tier NY
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Quote:
The CG5 will never be any good for a 6" F8 Achro. You need a bigger mount like the G11.
Chas
A CGEM does the job just as well for a lot less money and zero learning curve, the HC is identical to the CG5.
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If it'll fit on a sig you don't have enough
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Steve Fisher
"Curmudgeon in Training"
Reged: 08/12/06
Posts: 1907
Loc: Utah
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We have looked several times at the possibility of building a Hargreaves strut for my friend Bills C6R that he mounts on an Atlas.
We have been stopped by the tapered cell that the C6R uses. I had the thought several months ago that a strut could be mounted from the dewshield to the counter weight shaft.
I'll guarantee that if you can devise a strut it will be more than usable with the CG 5 but a larger mount would be best.
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Steve
8" f/12 D&G Achromat Refractor Delivered 08/27/09
6" D&G f/12 Achromat Refractor
66mm f/6.1 William Optics Petzval
6" f/8 Celestron Starhopper
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"Never try to teach a pig to sing, It wastes your time and it annoys the pig". (Robert Heinlein)
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Phil Cowell
professor emeritus
Reged: 05/24/07
Posts: 520
Loc: Southern Tier NY
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Quote:
We have looked several times at the possibility of building a Hargreaves strut for my friend Bills C6R that he mounts on an Atlas.
We have been stopped by the tapered cell that the C6R uses. I had the thought several months ago that a strut could be mounted from the dewshield to the counter weight shaft.
I'll guarantee that if you can devise a strut it will be more than usable with the CG 5 but a larger mount would be best.
Hi Steve,
I run a C6R on an Atlas and at times on my CGE Pro. Mine has a Losmandy D Dovetail and on the rare occasions I use it on my AS-GT I use the ADM Vixen to Losmandy adapter and it's rigid. Almost like a double thickness Dovetail.
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If it'll fit on a sig you don't have enough
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Bill Cowles
Pooh-Bah
Reged: 04/16/06
Posts: 1093
Loc: Utah
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Here is my C6-R on an Atlas with an ADM saddle, plus more weight to the back. The Atlas or CGEM are much better than the CG-5 and the CGE would be even better. Going to the CGE will be double the cost and greater weight to transport and setup.
Bill
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Lunt LS60TS50DS/B1200/FT (on order)
TV Gensis/Solarmax 60 filter
PST DS/Herschel Wedge/C4-R
C6-R /Atlas Goto/Moonlite CF2
12" LightBridge/Round Table
MCHP/8" Orion OTA/Ultima 2000
10" Discovery /Celestron SE-4
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Bill Cowles
Pooh-Bah
Reged: 04/16/06
Posts: 1093
Loc: Utah
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The longer dovetail can help, but it's better to have a longer and better saddle. Here is my new ADM dual saddle compared to the stock Atlas saddle, big difference and more secure and steadier.
Bill
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Lunt LS60TS50DS/B1200/FT (on order)
TV Gensis/Solarmax 60 filter
PST DS/Herschel Wedge/C4-R
C6-R /Atlas Goto/Moonlite CF2
12" LightBridge/Round Table
MCHP/8" Orion OTA/Ultima 2000
10" Discovery /Celestron SE-4
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Bill Cowles
Pooh-Bah
Reged: 04/16/06
Posts: 1093
Loc: Utah
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I have also replaced the stock dovetail with a solid one.
Bill
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Lunt LS60TS50DS/B1200/FT (on order)
TV Gensis/Solarmax 60 filter
PST DS/Herschel Wedge/C4-R
C6-R /Atlas Goto/Moonlite CF2
12" LightBridge/Round Table
MCHP/8" Orion OTA/Ultima 2000
10" Discovery /Celestron SE-4
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cuzimthedad
Just Be Cuz
Reged: 04/09/06
Posts: 3856
Loc: Sonoma, Northern California
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Hi Steve,
I agree with Phil. If you are willing to upgrade to a beefier mount then go with the CGEM. I had the Meade equivalent of yours, the LXD75 AR-6, and did something a bit different. I upgraded the ota with an Antares 1529. It's a shorter tube achro, f/6.5, than the CR150 so the moment arm is more stable allowing a shorter damping time. It is acceptable. However, at some point in time I will probably upgrade to the CGEM.
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Dan
20" f/5 Obsession
Antares 1529
Various Naglers, Ethos, UO Orthos
Gone but not forgotten: Meade 5K UWAs & Plossls, WO UWANs, TV Plossls & T6 Naglers, Tak LEs, 13 & 17 Ethos, Vixen LVWs, Orion Stratus, Meade 12" LX200R, TV Genesis and TV102, Meade AR6, WO 80SD. All these helped to get me to what I own today.
The Off Fisher Lane Irregulars
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AV in CMH
professor emeritus
Reged: 11/07/05
Posts: 529
Loc: Columbus Ohio
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Tim,
For what it is worth, I had a CR6 on a CG5 and I found that if the OTA is very carefully balanced and everything is tight, starting with the Legs to hub connections the setteling time is 1 or 2 at most.
I replaced the tripod legs with very solid wooden legs and this made the biggest difference of all.
Good luck, don't give up,
Anthony
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cuzimthedad
Just Be Cuz
Reged: 04/09/06
Posts: 3856
Loc: Sonoma, Northern California
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Another help would be the use of anti vibration pads.
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Dan
20" f/5 Obsession
Antares 1529
Various Naglers, Ethos, UO Orthos
Gone but not forgotten: Meade 5K UWAs & Plossls, WO UWANs, TV Plossls & T6 Naglers, Tak LEs, 13 & 17 Ethos, Vixen LVWs, Orion Stratus, Meade 12" LX200R, TV Genesis and TV102, Meade AR6, WO 80SD. All these helped to get me to what I own today.
The Off Fisher Lane Irregulars
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Tommy5
Carpal Tunnel
Reged: 03/28/04
Posts: 1989
Loc: Chicagoland
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My Cr-150 with the CG-5 and vibration pads is fine for visual as long as there is no wind, the only time the view wobbles is when i touch the focuser to move it, an helical focuser worked wonders for me, a motor focuser is also a great idea to get a decent focus in real time. A larger mount is a nice luxury but i would rather spend the money on a larger/better optical scope, it is usually better to buy a scope and a mount together much cheaper then buying separate.
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John Fitzgerald
In Focus
Reged: 01/04/04
Posts: 2167
Loc: AR
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After a year, I sold the CG-5 that came with my CR150 HD and bought an Atlas mount from Orion. IMO it's the perfect match for the OTA for visual observing. That was six years ago and it's still going strong.
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letimotif
No Complaints
Reged: 05/20/07
Posts: 2446
Loc: No Idea, but I know my speed!
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Some things that might help:
1. An Orion Skyview Pro Mount Extension will fit the CG5-GT. That'll let you keep the tripod legs collapsed and the mount a bit more sturdy.
2. Orion's Electronic Accu-Focuser is an inexpensive add on. It will not eliminate image shift with the stock R&P focuser, but you can velcro the controller to the tripod legs or the mount extension above, and while using it keep your mits off the OTA when you focus. Works great.
3. Right now, if you go to Highpoint Scientific's ebay site you'll see a CGEM mount on sale for $1,150 (new open box) or $1,199, both with free shipping. These are fine deals on the mount if you can swing the price.
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Ah, but a man's reach should exceed his grasp, or what's a Heaven for?
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Tim A.
professor emeritus
Reged: 09/19/07
Posts: 663
Loc: 40 30'N 105 3'W
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First, thanks to all for the flurry of answers! Never at a loss for words, we CNer's, are we?
I suppose I should have known there would be calls to put a bigger horse under this caballero. I'd love to. Ain't gonna happen. (Contract work dried up & blew away this year.) In truth, this isn't that bad a problem; I can live with it. (Again, this is a CG-5GT on a steel-tube tripod.)
But it's good to know that a longer dovetail bar wouldn't help. Now that I think about the mechanics, of course it wouldn't help!  At least that's 50 bucks I don't need to throw into the pit! I'd also thought of a longer saddle plate, but I don't think that's an option on this mount.
Quote:
Some things that might help:- An Orion Skyview Pro Mount Extension will fit the CG5-GT. That'll let you keep the tripod legs collapsed and the mount a bit more sturdy.
- Orion's Electronic Accu-Focuser is an inexpensive add on. It will not eliminate image shift with the stock R&P focuser, but you can velcro the controller to the tripod legs or the mount extension above, and while using it keep your mitts off the OTA when you focus. Works great.
- Right now, if you go to Highpoint Scientific's ebay site you'll see a CGEM mount on sale for $1,150 (new open box) or $1,199, both with free shipping. These are fine deals on the mount if you can swing the price.
Well, I've already taken care of the first two items. The power focuser (it ain't "electronic") makes a huge difference, especially at higher magnifications. The mount extension is good for the reason you mentioned, plus it completely eliminates any chance of collisions with the tripod during slews.
As for the CGEM, I'd love to, but needs must, you see. Wind, yeah, that can be an issue, but I bet this sail would flap a little even on a CGEM.
Anyway, when everything is tight and well balanced, it's easy to get good views with this rig. In fact, I used it on Halloween to treat neighborhood ghosties to views of the moon from the driveway.
-- Tim
Colorado
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Tim -- Colorado
12.5" f/5 Dob (Starbucket)
Celestron CPC800
Celestron CR-150 HD on CG5-GT
Galileoscope
Oberwerk Deluxe II 20x80 & Ultra 10x50
Celestron Regal LX 8x42
Bio-binoculars 1x6
"Me? Crazy? Oh, yeah. Crazy like an ox!"
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