dddhgg
sage
Reged: 08/03/07
Posts: 265
Loc: The Netherlands
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Hello ladies and gentlemen,
while browsing the internet I noticed that many 8" SCT users who have a CG5 mount use only one standard 10 pound counterweight instead of two. Is this OK, or should two be used really? My mount came with two such weights, and I used them both this weekend. I did notice some stiffness in RA though. Could this be due to too much weight on the counterweight side? If one suffices, how high should the dovetail rail approximately be placed in the saddle?
Thanks for any replies!
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Meade 8" SCT (an older white-tubed version)
Celestron CG5 (non-GOTO)
Teleskop-service 30 mm WA
Teleskop-service 7-21 mm zoom
GSO 2" standard star diagonal
Edited by dddhgg (09/03/08 03:53 PM)
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GlenM
Pooh-Bah
Reged: 05/20/07
Posts: 1061
Loc: 53° 36'N 2° 06'W
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Kim,
set the scope up with it 'East' heavy. This will make the tracking a little more accurate.
Not sure if this website may help also www.astronomyboy.com
Hope this helps a little.
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Glen
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gordianknot
sage
Reged: 09/04/05
Posts: 447
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The key thing is checking of the scope is balanced per the CG-5 manual's directions. This means loosening RA clutches, testing the balance and moving the counterweights until there's no rotation and then doing the same for the dovetail on DEC. Again, see the manual for details (pages 13 and 14 on the version I downloaded) for details.
It is true that for many scope you can balance with two counterweights or one on the counterweight shaft. In theory, using two counterweights should be slightly advantageous because it slightly decreases the moment of inertia of the system thus making it easier for the motors to slew to targets, however I wouldn't worry about that very much.
In my experience, DEC balance on the CG-5 is very important, especially for long refractors because the DEC motors are relatively easy to overpower due to imbalance. I think this is probably less of an issue for an SCT because it is shorter, so its center of mass is more likely to be centered over the mount's head.
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 1744
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I have used C8 on CG5 many times, and have tried using two weights higher on the shaft, and one weight lower on the shaft.
To me, I didn't really see any difference. Sometimes while focusing, I think the extra weight might have made mass enough to slighly resist a bit of shaking when touching the focuser, but whatever improvement seemed pretty small to me.
In the end, I went to a single counterweigth. Just one less thing to fuss with. I only use two weights on my CGE1400 because it is REQUIRED to balance. ON everthing else including my 6" refractor on the giant LXD750, I use one. They all seem to work fine.
The easist thing to do is try it! You won't hurt anything. And if you can't tell the difference, then you have your answer!
As for the doveetail rail, the use of one or two weights will not affect the position of the telescope in the saddle.
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
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Middle Age Man
member
Reged: 07/12/07
Posts: 34
Loc: Northern NJ
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I used to use two weights on my LXD75 with a C-8 on top but to have a correct balance both of the weights had to be close to the mount head and depending on which direction the scope was pointed the mount screws would routinely knock out the power connector. I have been using one weight for a while and it is much farther away from the mount head and I don't have to worry about losing power.
I only use two weights if I have my guide scope attached and even then they are far enough away from the power connector that I don't have to concern myself about it.
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Hardin 10" DSH
Celestron C-8
Celestron Nextar 8 GPS
William Optics 66SD
Meade 2080
Meade LXD-75
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dddhgg
sage
Reged: 08/03/07
Posts: 265
Loc: The Netherlands
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Thanks, people, for all the help. I'll give it a try with only one counterweight and will let you know how it went.
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Meade 8" SCT (an older white-tubed version)
Celestron CG5 (non-GOTO)
Teleskop-service 30 mm WA
Teleskop-service 7-21 mm zoom
GSO 2" standard star diagonal
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pbnelson
newbie
Reged: 09/05/08
Posts: 1
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I'm wondering if I should upgrade my old Meade 2080 system with this Celestron CG-5 mount.
How do you attach your Meade 8" SCT to it?
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dddhgg
sage
Reged: 08/03/07
Posts: 265
Loc: The Netherlands
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Quote:
I'm wondering if I should upgrade my old Meade 2080 system with this Celestron CG-5 mount.
How do you attach your Meade 8" SCT to it?
I bought it used, and it just came with the Synta/Vixen-style dovetail that fits the CG5 saddle. But if you don't have such a dovetail already installed directly onto the OTA, maybe you could get tube rings for it, and install the dovetail to those. Good luck!
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Meade 8" SCT (an older white-tubed version)
Celestron CG5 (non-GOTO)
Teleskop-service 30 mm WA
Teleskop-service 7-21 mm zoom
GSO 2" standard star diagonal
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gordianknot
sage
Reged: 09/04/05
Posts: 447
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If yours didn't come with a Vixen style dovetail, Losmandy (and probably others) make them for the 8" Meade SCT, so you wouldn't need tube rings.
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 1744
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Well, maybe.. Maybe not. I am not sure if all of the old Meades were pre-drilled to accept dovetails.
I mean you can BUY a dovetail, sure... But if there aren't already screw holes, it might prove daunting to have them drilled and tapped into the Corrector cell and mirror housing.
Probably should ask on the SCT forum to see if someone that owned one of these can confirm that it has the necessary holes...
I owned a 2080 LX3 about 20 years ago, and I don't recall that the Cells were drilled and tapped for rails at that time...
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
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Jeff Lee
sage
Reged: 09/17/06
Posts: 389
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I think your meade tube weighs a lot more than a C8. My C8 with the stuff I normally use is probably 15 lbs, I think the stock meade is 18 to 20. A single weight works fine with my C8 on an LXD75 fairly far down the shaft.
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Jeff Lee
C90,C5,C8, 10 x 50's
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RogerRZ
Whatta you lookin' at?
Reged: 01/09/06
Posts: 2165
Loc: West Collette, NB, Canada
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The Meade tube weighs more, but I still think one weight would do the trick. Right now, I'm using two 11lbs weights, about one inch from the end of the fully extended shaft of my EQ6, and on the other end sits an ADM D-series saddle, holding a 15" Losmandy dovetail plate, two Vixen saddles, a 8" Meade OTA, a Celestron 127mm SCT, a 66mm f/6 refractor, and a Telrad.
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-Roger Pitre-
1 X 7 binocular
Meade 2080 LX10
5" Celestron SCT
Skywatcher Equinox 66
Starblast OTA
EQ6 Pro mount (spiffed up with ADM stuff)
8X42 Bushnell binos (pretty decent for 25$)
Canon Rebel XT (AKA 350D)
Starshoot autoguider
Tolerant Spousal Unit (AKA The Lovely Mrs. RogerRZ)
----------AJP Observatory----------
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DL Sharp
member
Reged: 10/05/05
Posts: 20
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I use a Meade SC-8AT with an LXD75 mount. I've found that if I use just the stock meade stuff on the visual back (1-1/4 diagonal, meade series 4000 plossl), I only need one 10 lb. counterweight near the end of the shaft. When I start loading more and heavier stuff such as an SCT crayford, 2" diagonal, and Baader Hyperion eyepieces, I really need to rebalance with 2 10 lb. counterweights.
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David
Meade LXD75 SC-8AT, AR5
Hardin Optical DSH-8 f/6 Newt
Baader Hyperion 8,13,17,24mm
GSO Superview 30,42mm
Cincinnati, Ohio
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