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PortaMount-Vibration Damping times

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#1 Terrance

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Posted 30 April 2009 - 05:35 PM

In an attempt to be more scientific, and to kill time on a cloudy day, I timed vibration damping times for my Vixen Portamount in several different configurations.

I used a Orion Starblast 6" reflector OTA (6" f/5 newt, 12 pound OTA, 28" long tube) with a 6x30 Orion finder as the only added accessory on the tube. I mounted that on the Vixen PortaMount, (the old regular stock version-not the "mini" or the Porta II) and then slapped the tube at its mirror end, and then a leg between the brace and the top of the leg, with legs unextended and then extended to the brace point, on concrete and ground, with and without VSPs (Celestron Vibration Suppression Pads).

I also had a standard Orion/Vixen metal triangular ep tray with screws reversed dropped into the holes in the leg braces, because that is the way I always observe. Note this may provide some extra stability beyond the cheezy plastic circular tray that attaches only to the center that the mount came with, because the triangular tray attaches directly to each of the 3 leg braces, providing additional support for each leg.

I counted off seconds to myself. I used a 7mm TMB ep which would give a mag of 107x. I did each slap 3 times.

Legs unextended on Pavement: 3 seconds to damp out for both tube slap and leg slap. With VSPs, about 2 seconds for both tube and leg slap.

Legs unextended on Ground: 2.5 seconds both tube and leg, and with VSPs 1.5 seconds for both leg and OTA slaps.

Legs Extended out to where sliding inside leg was at level of braces between legs: Pavement 3.5 secs for leg, 4 secs for tube--With SVP's 2.5 for leg, 3 secs for tube.

Legs Extended on Ground: 3 secs for leg, slightly over 3 secs for tube. (Did not try with VSPs)

It has been noted by some that "slapping" the scope may not be a real world test, unless, of course, the neighborhood bully routinely comes into your back yard and slaps your scope around. However, this is the best I can do.

Conclusion: Extending legs increases vibration somewhat, pavement creates more vibration than ground, VSPs reduce vibration somewhat...Well, duh, ...I could have predicted that!

Anyway if you need more testing, go slap your own scope around, as mine has suffered enough!

#2 Starlighter

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Posted 01 May 2009 - 02:28 PM

Do yourself a favor. Dump the aluminum legs and get wooden ones from Hands On Optics which sell for $79. They will decrease vibration time. In fact, I found they cut it in half. They're very easy to install.

GTO Mounts

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#3 Terrance

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Posted 04 May 2009 - 05:46 PM

I am getting an Astro-tech Voyager mount shortly. I will do the same tests on it when it comes.

In the fullness of time, if I get bored again, I will then put the wood tripod from Hands-on back on the PortaMount and test it again. I am still surprised Starlighter had such good results with that tripod on his PortaMount, when I did not get such good results when I tried it on mine. :confused:

#4 Waduino

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Posted 04 May 2009 - 09:00 PM

I also have the wooden legs, and I wasn't sure how helpful they were until I put the aluminum legs back on. They didn't stay on for long. One thing I don't like about the GTO legs is that it's a pain to loosen 6 wingnuts to change the leg adjustment in the field, especially since I tighten them up fairly tight.
Wad.

#5 Starlighter

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Posted 04 May 2009 - 11:34 PM

Well, I like have double sets on each leg. Keeps me reassured they won't suddenly come loose. I had a single leg held by one nut come loose on my Celectron Nexstar 6ES. Fortunately, I was standing right next to it as it began to telescope inward with the mount starting to fall over. I caught it just in time.

I use an adjustable observing chair so I never have to adjust the height of the tripod. It's much quicker to adjust the seat even with a mount that has a single nut on each leg.

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#6 Waduino

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Posted 13 May 2009 - 07:11 PM

So I picked up my Starbound observing seat today. Now I'm all set. Could have used it last night observing at the zenith. Silly me.
Wad.

#7 Waduino

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Posted 15 May 2009 - 07:26 AM

I gave the Starbound its first go last night. Really nice improvement over the three legged stool I was usinng before. Very comfortable and very easily adjusted. Especially nice for near zenith obs with the refractor on an alt-az.
Wad.






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