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8" F/9 on a CGEM with a Hargreave Strut?

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#1 De Lorme

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Posted 12 September 2013 - 10:22 AM

I posted this first in equipment. I should posted it here first, sorry. I'm looking to put together a 8"f9{8" F6 if I have to} on my CGEM. Was told by Eddie and Brian{in equipment} that the weak link is the tripod. If I install heavy wooden legs plus a Hargreave Strut system would that make the difference in the flexure problem? My concern is would I damage the RA and DE motors or any other component's over a period of time. The weight for the F/9 is approximately 33lbs and 30lbs for the F/6.
Things that you should know are, I'm a visual only and I have a roll of roof that keeps me out of the wind.
I once had a 10" Astro Tech reflector on my CGEM that rode well so I thinks a 8" f/6 would also. But I would prefer the 8" F/9 if it's possible.
Thanks for the advice I really appreciate it. De Lorme

#2 WesC

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Posted 12 September 2013 - 01:43 PM

So you are visual only? I think the CGEM as is, is just fine for what you are doing.

My Edge 11 with all the extra gear on it runs about 32lbs, and for visual its perfectly fine with my CGEM straight out of the box. Unless you are planning an unusually long moment arm, but even then, if you balance carefully you should be just fine for visual. The best way to keep the tripod flex to a minimum is not to raise it up on the legs and use isolation pads. If I do raise mine, its never more than 10-12 inches, which is plenty.

I've only found the tripod to flex when I extend the legs all the way.

AP? That's a whole different story... ;)

#3 De Lorme

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Posted 12 September 2013 - 09:50 PM

WesC, Right now I have a CR6" with the legs extended all
up to about the last 3" inches. It's been that way since I've had it. Even at this height it only takes a second
for the telescope to dampen down. The focuser hit the leg once, but I might have bumped it when it did.
I've found an inexpensive way to make a spreader bar. With
this and a Hargreaves Strut{and a height extender} I think
this will work. Still concerned that this will put to much pressure on the motors. Do you know anybody who's pushed
their CGEM with bad results? Thanks for the advice. De Lorme

#4 A. Viegas

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Posted 12 September 2013 - 10:00 PM

My 150mm R30 istar weighs like 28 lbs. it is also 1200mm so quite long. With tips legs extended 12-15inches it takes a second or two for vibrations to die down at 70-150x mag... At over 150x it's more like 3 sec and less than 70 mag it is not very noticeable...

Picture here Istar bazooka

Al

#5 De Lorme

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Posted 12 September 2013 - 10:08 PM

That a nice scope! Heard nothing but good about Istar.
What a great time we live in! De Lorme

#6 T1R2

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Posted 12 September 2013 - 10:12 PM

Its not the weight of the F/9 scope, 33lb, its the length of the ota, 1800mm I believe, you'll have focusing jiggles but after that you might be ok if you don't bump the ep when looking through it, I personally would not put anything over 5" F7-ish refractor on that mount, but it could work for you.

#7 De Lorme

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Posted 12 September 2013 - 10:34 PM

T1R2, I've had a CR6" on it for the last 3 years and it works really great! Probably not for AP though. Do you think
that the Hargreaves Strut and the spreader bar won't make a difference? Do you know of anybody who's put a 8"F/9 on a CGEM with the added up grades and ruined a motor? Would like to know now rather then learn it the hard way. I know the 8"F/6 would work.
Any advice is welcome. Thanks for the help. De Lorme

#8 T1R2

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Posted 12 September 2013 - 11:58 PM

Sorry D, I just don't think you'll be happy with the size of that scope on that mount, I really don't think the strut and the spreader will make a difference with a scope of that size, I have a 08" CGE mount(not PRO) and its bigger than the CGEM, and I would not go over a 150mm F/8-ish refractor even on that. Best bet is to look at them on that mount, if it looks like the scope is bigger than the mount and it looks funny, then its under mounted, if you look at it and it's in proportion with each other and it makes you say "that looks real good", then your good to go. We all hate to make changes, specially if we have our minds set on something or already have a certain mount or ota, ideally the mount should look more robust than the telescope. hope this helps a little.

Edit: I know of no one who use that set-up.
not sure about hurting the motors






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