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8" f/5 Ideas

Started by Brad, 05/17/2002 11:22PM
Posted 05/17/2002 11:22PM Opening Post
I'm collecting parts for an 8" f/5 travel scope. Although a 1.25 focuser would probably be adequate, I do have a couple of 2" ep's, so I'll probably build or buy a light weight 2" unit. (Any thoughts on this would be appreciated.)

One unique idea I have is to try to pivot the axis of the dob style mounting near the eyepiece in order to allow a comfortable sitting viewing position no matter whether viewing near the horizion or straight up.

This would require an odd looking balance system hanging out in front of the scope. I've never seen anything like this but I believe it would be possible. As long as it could be detached for transportation.

Has anyone done this?

Posted 05/18/2002 04:28AM #1
If you get a copy of Berry and Kreige's book, The Dobsonian Telescope, the appendix has plans for a very nice 8" f/6 dob. I have made several from this plan and it is an excellent design and easy to make. I think you will find that with an 8" f/5 you can rotate the tube in the tube cradle to such an angle that the eyepiece is comfortable from a setting position from about 30* to the zenith. I would mention that if you use sonotube (the thicker construction grade) just several good coats of a quality latex is really all you need to make it sturdy, especially for such a short tube, so the Kydex wrap is overkill.
Posted 05/18/2002 09:24AM #2
Almost anything's possible, but you have to pay the piper. It implies a much taller rocker box, and it tends to make the OTA longer compared to its width, leading to more problems with vibration. I suspect after all is said and done you will need many more pounds of more beefy construction, not to mention the weights themselves, to achieve this with a standard Newt design.
Posted 05/18/2002 02:00PM #3
Thanks guys. Maybe it wasn't such a good idea after all:-)

Mike, how do you like the helical focuser on your 7"? I'd stick with a 1.25" but I've got a couple of 2" ep's I'd like to use.
Posted 05/18/2002 02:38PM #4
When you say 8" "travel scope" I think you mean truss-style that will collapse into a tiny box. I did see a web site a couple years back about someone who made an 8" f5 for a trip to Australia. It fit into a carry-on size for an airplane. I'll see if I can find it again and post a link.


Fort Lewis Observatory: (37.238, -108.052) ~2360m (7744 ft.) elevation.
Darkness - typically 6.5+
Scope - Meade 16" LX200; f6.3 focal reducer
Focus - JMI Smart focus
Camera - SBIG ST-10XE; (~.5"/pixel)
Guiding - AO-8 and/or Meade 5"/DSI/PHD