My second parallelogram mount

[Per167]

Finally managed to finish my p-mount tonight! This was actually the second attempt. The first failed quite miserably and I'd rather not go into the details. "Wobbly" and "inherent lack of stability" are the first words that come to mind when I think back upon it. Anyway...

My latest attempt is based on the design by Graham Wood that can be found here: http://web.archive.o...ino/binonet.htm

I also needed I tripod to go with it so I took a lot of inspiration from here:

http://www.cloudynig...hp?item_id=1309

I can thoroughly recommend both designs! Although I haven't been able to try it out for real yet - no darkness on my latitudes for another month - it seems quite stable actually. Maybe I wouldn't call it rock solid but the main source of vibration seems to be the black piece of metal used to attach the binocular to the wood.

I learnt a lot during this project. I don't mind woodworking but I really do not have a lot of experience. I think the amount of time I put into this project is around 30-40 hours including planning and shopping for parts. The price of the wood and other bits and pieces is probably in the area of 100GBP. Oak is quite expensive - at least here in Sweden.

Graham Wood gives no specific dimensions in his plans but the length of the main beams are 110cm on my mount. The height of the tripod is 115cm. The plan was to be able to use the tripod legs for my Nexstar 5SE mount as well but in order to make the legs tall enough for this mount they are slightly too high to be a good match for the Nexstar.

Where I stepped away from the original design is the counterweight. At the moment I have a pair of Celestron 15x70 but I am considering upgrading to Apollo Helios or the like. As these are a bit heavier I wanted to be able to adjust the counterweight easily. As you can see in the second picture this can be made by letting the screw holding the counterweights (hidden under a piece of wood) slide in the elongated hole.

It's not really evident from the picture but I used teflon+ebony star for the bearing on the top of the tripod. Really, really smooth.. For the other joints I just cut out plastic washers from a plastic food box. Seems to do the job as well.

What really appealed to me with the design is that you can make it really stable without using a lot of heavt material just by making it wide - approximately 25cm between the main beams and 25 cm from the main beam to the parallel arm.

So what's next? The dark nights will not be back for yet another month here. Don't worry - a 6 inch mirror blank is on it's way and I'm reading up on mirror grinding!

EDIT: Sorry for the lousy quality of the images. I only had the iPhone at hand. Will try to take better pictures with a real camera and post later.

/Per

[swamp thing]

Hi Per

I hope this one is more stable for you. It looks good to me from the pics.

[Breitling1884]

Nice job.