Johnsonian Type 5 Platform

Has anyone tried the Johnsonian Type V Platform? I would like to hear your overall impressions. I am planning on using it with my Discovery 13.1" dob, and my new Astrosky 10" dob. I look forward to all your comments. Thanks.

Best,

Joe

Joe, it has been recommended by the Yahoo group that a flat plywood board be bolted to the top, for the scope to sit on. I have been meaning to do mine, but work has kept me from it (I really should sell it).

The design itself is super-clever, great for someone who travels to different latitudes.

-- William

Hi Joe,

Drop Dave Bush a line. He had one of these for a brief time for his 12.5" PDHQ, and would probably love to hear from you. I've got a Type IV, and it works fine, but is a back breaker to lug around. There is a Type VI in the works also for smaller (6"-10") Dobs.

Hugh

I bought one used off astromart 1 1/2 years ago and I use it all the time. I don't do photography and my scope is an Orion XT8 (my first and only--so far). The Type 5 came with a top made by the previous owner and I always use it.

The toughest part is getting the drive wheels into the correct slot. It is easy to miss the slot or worse yet, get the two wheels into different slots. With the platform properly polar aligned, I use a compass and adjust for variation, I have had Saturn filling the viewfinder at 420X, the highest power I can attain. This was at a star party for my daughter's first grade class and with about 15 viewers, I had to adjust the scope once.

The best part about the Type 5 is that if I want to sell it again, latitude is not an issue, it can go anywhere.

Joe Morey said:

Has anyone tried the Johnsonian Type V Platform? I would like to hear your overall impressions. I am planning on using it with my Discovery 13.1" dob, and my new Astrosky 10" dob. I look forward to all your comments. Thanks.

Best,

Joe

Hi Joe,

I bought a used Type V on Astromart last summer. I've only used it for visual (not photography). It tracks well, except when the batteries get low. I've used it with magnifications up to about 350x and could see very little drift. This was as good as expected, since I usually align it by setting the platform in the yard in the daytime and aiming towards where I think Polaris should be.

I've had a few problems. Mainly with the hand controller and with the platform "jumping it's track". The hand controller problem may have been because the batteries were low. The track-jumping problem I think can be attributed to a long moment arm on the telescope and not enough weight over the tracks. I have a 16" scope that weighs less than 60 lbs. This happens when I slew too quickly from one place to another. I think I've solved that problem by adding a pivot post to the platform, moving the weight toward the tracking wheels, and replacing the PFA pads with Teflon.

Hope this helps,
Kevin Beebe