Telescope Reviews: Vixen Portamount...

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.

Edited by mathteacher (02/18/09 08:23 PM)