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Alt-Az Mount for AT90ED

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#1 mad_hungarian

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Posted 28 February 2009 - 09:43 AM

Hi,
I'm looking for an Alt-Az mount head for an AT90EDT refractor (15 lbs with finder, EP and diag; 21" long). I'd like to mount the head on a standard, heavy duty (rated to 20 lbs) 3/8" X 16 camera tripod which I already have.
I've tried the Portamount and Astro-Tech Voyager both are a little too heavy for my intention of using the scope as a grab-n-go. I 've also tried the Universal Astronomics Unistar which seems to be the closest to meeting my needs. I liked the idea of the slow motion controls of the Porta and Astro, though. My budget is $250 for the head.
Thanks

#2 Erik D

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Posted 28 February 2009 - 10:31 AM

The UA Macro Star is rated for 25 lbs. The 28X110 bino shown is about the same length as your OTA:
http://www.garrettop...-p/ua-01601.htm

Most heavy duty photo tripods use 3/8-16 mounting bolt.

The side saddle type mount such as the UA Uni and Macro/Micro mounts require you to balance the load carefully in Alt. A sliding dovetail plate is a must.

ERik D

#3 Jim7728

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Posted 28 February 2009 - 10:38 AM

I vote for a used Unistar, light version will be "too light" ,imo,for that ota.

Macrostar looks like a great choice, as long as tripod has elevator column for ota to clear legs when viewing near zenith.

DesertSky mounts may also be a good match.

http://www.desertsky...com/Mounts.html

#4 mad_hungarian

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Posted 28 February 2009 - 12:20 PM

Thanks Jim,
Those Desert Sky mounts look pretty nice. Do you have any experience with them or know of anyone that has?
Also, thanks for pointing out my typo. The thread is 3/8" X 16, not 20 as I wrote.
Have a great night!
Ted

#5 Mike Sandy

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Posted 28 February 2009 - 01:54 PM

If you haven't looked at the Half Hitch yet, you might think about it:

http://www.halfhitchtelescope.com/

I haven't used one yet, but I was so taken by the design and the discussions I've had with other owners that I bought two of them (they are on their way to me now).

I realize the price for the current production of the Mark II is out of your range, but if you contacted the owner (Charles, a very helpful guy) he may have an early pre-production model left that might be close to your budget. There was one that popped up on Astromart recently selling for close to your budget as well.

#6 Jim7728

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Posted 28 February 2009 - 03:39 PM

Those Desert Sky mounts look pretty nice. Do you have any experience with them or know of anyone that has?



No first hand experience, a Cloudy Nights forum google search will give you an impression of the mount.

Desert Sky Astro

The 90EDT maybe pushing the Desert Sky mount to it's limit. If I had that ota on my Giro 3, I'd definitely have a counterweight on the other side of the head to smooth out the azimuth motion. Again, the Unistar maybe a better choice in that the ota will be over the center of the azimuth pivot and will not need a counterweight on that axis. The Voyager head also has the ota located over the center of the tripod rather then off to the side. ;)

#7 islandsteve11

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Posted 28 February 2009 - 10:18 PM

Depending on your tolerance for settling times, it's very likely that you'll find your 20lb rated capacity photo tripod isn't sturdy enough for a 15lb OTA plus the few pounds of a mount head.

The general rule of thumb with photo tripods and telescopes is that you want a tripod rated for at least twice the weight of the OTA. The reason for this is that cameras are generally used close to horizontal and the tripod's center of gravity (with generally short & light lenses), while telescopes are not. Naturally, YMMV.

For light weight, compactness and vibration dampening, carbon fiber photo tripods are probably the ultimate G&G tripods, but you pay a BIG premium for it.

Clear Skies

EDIT: There are some good reviews of Universal Astronomics, Giro and other alt-az mounts in the CN Reviews section on the CN homepage. Unless you buy used, you may need to increase your $250 mount head budget.






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