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#1 AlienRatDog

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Posted 17 February 2009 - 11:50 AM

Hey guys, so I have a Vixen portamount, I complained about its stability so I tried the Orion Altaz, lets just say I like the slow motion controls, sure the Orion was stable but was jerky and I kept over shooting while trying to track by hand...the portamount has beautiful slow motion controls that don't make me miss having a clock drive (more altaz mounts should have em!)...problem is it is jiggly! I think the aluminum legs suck, I was thinking about getting wooden legs from Handsonoptics....has anybody tried and do they make a difference, btw the scope is a C100ED...

#2 TheMenace

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Posted 17 February 2009 - 12:07 PM

What is the weight of the 100 ED?
Seems like a lot of scope for the porta mount,IMHO.

:question:

#3 AlienRatDog

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Posted 17 February 2009 - 12:11 PM

I do not remember the weight of the 100ED but it is pretty much the limit of the portamount, the thing is for me to use an Altaz I must have slow motion controls, I can deal with vibrations but dangit its a lot now, I just wanna reduce the vibrations....but yea its a lot of scope for the mount...

#4 StargazerBill

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Posted 17 February 2009 - 12:15 PM

Try some vibration suppression pads. they actually work. Won't eliminate vibration but will reduce by about 50%.

#5 TheMenace

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Posted 17 February 2009 - 12:20 PM

I'm thinking upgrading the legs would help,but a long heavy tube(porta mount wise),might be stressing the mount head itself.

#6 AlienRatDog

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Posted 17 February 2009 - 12:27 PM

It does, sometime the slow motion controls on the azimuth dont work...I would love a heavier duty mount but like I said, I want the slow motion controls....

#7 AlienRatDog

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Posted 17 February 2009 - 12:27 PM

The thing is I already own the mount...

#8 TheMenace

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Posted 17 February 2009 - 12:34 PM

I Don't want to sell you anything,but I don't want you to wear out your mount before it's time.
But...you could probably pick up a Orion short tube 80mm scope off e bay for about $100.

:whistle:

#9 AlienRatDog

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Posted 17 February 2009 - 01:32 PM

Good point, is the AT Voyager better, looking up specs, the portamount shouldnt have more than 10lbs on it...oops, lol...but the AT voyager has a 20lbs load rating...I was wondering if the tripod legs were better and would I still need to upgrade to wood (hey I like wood, good dampening properties)...

#10 AlienRatDog

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Posted 17 February 2009 - 01:46 PM

Ya know I also have a spare CG5 mount and the Voyager can mount on that tripod...hmmmmm

#11 Waduino

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Posted 17 February 2009 - 04:02 PM

I've tried the wooden legs, but just for 2 or 3 nights so far. They help, BUT in my case I think some of the jiggling is coming from the play in the azimuth bearing of the Porta. Others have this issue. Some don't. Mind you 100mm seems a tad big for the mount.
I'm starting to seriously think about a different mount.
Wad.

#12 ngc2289

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Posted 18 February 2009 - 04:37 PM

I was just on VixenOptics web site and 20lbs max load is listed for the Portamount. The max load for mini portamount is listed as 10lbs. So from what you are saying the figures listed on Vixens web site are a little overly optimistic? :ooo:

#13 AlienRatDog

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Posted 18 February 2009 - 04:46 PM

extremely optimistic...I think OPT lists the Portamount at 10 lbs and the mini at 8....but yeah, I think I am going to sell off the mount, the 100ED is too much, I mean like 15 sec dampening times, I am thinking of a Voyager on my CG5 tripod...

#14 ngc2289

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Posted 18 February 2009 - 05:32 PM

I hate to rain on your parade but the load limit on the Voyager is probably closer to 12 to 13lbs. With a better tripod add 2lbs. The build quality at least on mine is so so. My Voyager is a very early model so the ones they are making now may be much better. :shrug:

#15 mathteacher

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Posted 18 February 2009 - 08:16 PM

Abe, I totally understand your reason for wanting to sell the Porta. It's not ideally mated for the 100ED. Forget ideally, it's not even a decent match.

My scope came with the Porta, and at first I was appalled by it's vibrations after using my previous XT dob. I did lots of experiments on damping time. Near 200x, it took between 3 and 4 seconds to dampen. Focusing at high power is still difficult.

I still have my 100ED on the Porta. Why? because it's a light setup and it's easy to use, and the slo-mo controls are so nice. I've gotten used to the shakes; they don't bother me. Here's what I did to mitigate the vibrations:

1. I observe on pavement, so I need VSPs. However, I don't like the idea of picking them up every time I move my setup, so I cut open tennis balls and stuck them on the tips of my tripod. I dunno if they work as well as VSP, but they cut settle time by around 1s.

2. I ditched the stock accessory tray. I replaced it with an aluminum pie tin. I actually don't think this helps much, but actually bolting the accessory tray to the three arms of the spreader (a la Manny Miles) seems like a good idea.

3. I keep my scope light. I use a 1.25 diagonal and EPs. I do have a 9x50 finder, with is a big help in LP, so I keep it. Extra weight hanging off your scope just makes things worse.

Wooden legs: I have a Vixen SP tripod with wooden legs. I swapped them on once, and they surely improved the mount. Focusing was much better. I took them off because they were bulky and harder to set up. Starlighter has the HO legs, he like them a whole lot.

Other 'fixes' I've heard of:
Put weight in your accessory tray, or attach weight to the tripod hub and hang it through the acc. tray (extra weight, I pass).

Use some kind of tensioning device to spread out the tripod legs. I may tinker with this one. The idea is to insert a triangular piece of wood or metal between the legs and pull up on it, so it forces the legs outward against the spreader legs. This is supposed to stiffen the tripod significantly.

Bottom line: The porta is too light for the 100ED. If your mount weighs 3x your scope, then it will be steady. The Porta weighs almost the same as the 100ED OTA. Another way to go, cobble up some way to attach the porta mount to a heavy homemade tripod or pier (4x4). I bet that works.

#16 Waduino

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Posted 18 February 2009 - 10:31 PM

A few more comments on the Porta...

Its strengths are the slo-mo controls which work very well. The tripod isn't bad, appropriate I would say.

Its weaknesses are the plastic knobs, easily swapped for set screw type, and something that some of us have been focused on - some jiggling. I've tried the wooden legs. I think they may help a bit. I've switched back to see. But the real culprit in mine is the play in the azimuth bearing. It can be tightened up, but only so much before the friction gets high for slewing.
Next I'm going to check the balance of my scope and keep the az friction fairly high and see how it does but this is with an 85mm f/7.
I think 100mm is pushing the capacity a bit.
Wad.

#17 ngc2289

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Posted 19 February 2009 - 01:26 AM

I made my own tripod using red oak. I added a tensioner to the tripod to stiffen things up. I hope you can see what I did from the picture.

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#18 mathteacher

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Posted 19 February 2009 - 02:22 AM

Mike, nice mods to the tripod! :waytogo:

Guess what? An unexpected improvement to my porta mount was my... focuser :) I increased the diameter of one of my focus knobs using sections of bike inner tube. It takes a lighter touch to focus, which results in a lot less shaking. The porta almost pleasant to use! At 150x it took around 3s to dampen from a hard tap at the diagonal. I had a great time setting up Saturn with the slow motion knobs and watching it drift through the FOV for a minute at a time.

#19 Wildthing

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Posted 20 February 2009 - 09:19 AM

The weight support area of the 2 bearing surfaces in the PortaMount is just not large enough in my opinion to adequately support anything but a very light OTA. The overall bearing design is poor in my opinion and could have easily been improved upon during its initial design eliminating most if not all of these issues.

The most leverage is placed on the Az bearing due to the length of the arm. Also the staked bearing post or stud in the Az bearing will sometimes develope some movement... :(

Wish I had never bought mine!

#20 Waduino

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Posted 20 February 2009 - 09:31 AM

>> The most leverage is placed on the Az bearing due to the length of the arm.

I'm wondering if a thin spacer ring would help the az bearing. It would just prevent the tipping that occurs. If it worked, it could make a big difference, I think.
Anyone more mechanically inclined out there care to comment?
Wad.

#21 GaryML

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Posted 24 February 2009 - 12:51 PM

Hey guys, so I have a Vixen portamount, I complained about its stability so I tried the Orion Altaz, lets just say I like the slow motion controls, sure the Orion was stable but was jerky and I kept over shooting while trying to track by hand...the portamount has beautiful slow motion controls that don't make me miss having a clock drive (more altaz mounts should have em!)...problem is it is jiggly! I think the aluminum legs suck, I was thinking about getting wooden legs from Handsonoptics....has anybody tried and do they make a difference, btw the scope is a C100ED...


I had a Porta mount and had the same problems with my Vixen ED100sf (the same size as your scope). By tightening all the bolts on the Porta, using fairly high friction on both bearings, and sinking the legs well into the dirt, I could get the settle time down to about 3-4 seconds. But there was so much jiggling when trying to focus that it was nearly impossible to focus the thing.

I thought about the wood legs from HandsOn Optics, but I knew that in the long run I would never be happy with this mount. So I sold it and bought a William Optic EZ Mount with the tripod. This completely solved the problem. Incredibly stable with a settle time of 1/2 second or less. Easy to focus. I do miss the slow motion controls but with the tube well balanced on the WO mount I can keep objects in view with a light touch on the tube or diagonal, even at high power. The head is very well made and fairly small (but heavy). The tripod is a bit crude but it works well. And you can add a second telescope (or binoculars or camera) to the mount by adding an extra dovetail base on the other side). For $500 I think it is the best in this class.

#22 Waduino

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Posted 24 February 2009 - 01:54 PM

I swapped the wooden legs out, put the aluminum ones back, and... very jiggly. So the wooden legs do help somewhat. I put them back on. Somewhat better. Still a bit of a guess when focusing.
Not the right mount for a 100mm, IMHO.
Wad.

#23 Darren B

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Posted 24 February 2009 - 02:19 PM

When I first got mine, viewing above x100 was a pain due to vibration. VSP helped a great deal, but now I have fitted a wooden tripod. It's a lot better now. I had no real problems with the slo-mo controls apart from the altitude one that falls off when viewing towards the zenith. I do have a twin speed focuser so that does helps. Maybe the 100ED is to long and heavy for it.






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