8" Travel Scope Nearly Complete

[barx1963]

Well as this project is nearing completion I though I would pop a new thread and highlight some things I have done with it.
Basic construction is now done. the ground board is complete and I have installed teflon pads on it. Inserted a brass bushing left over from the Astrosystems pivot kit that I used on the 20" to install in the rocker box. A major change from Gary's design is that he made a jigger to allow him to attach the scope to a plain camera tripod. I have built a tripod to get the scope off the ground. I made 3 legs from 25mm dowell, drilled an 11mm hole in the end then dropped a 6mm bolt witha couple of nuts (too keep it square) down the holes with a bit of JB Weld epoxy. Then I fashioned pads for the ground board and cut angle in them, drilled holes in the angled areas and popped threaded inserts in them. Works like a dream! The scope now sits at an easy height for normal use or I can remove the legs and use it as a table top dob.
Once I setup the stowage system with all the rings sitting inside the rocker box, the 3 legs will simply sit in the corners, I will put inserts in the corners so the can be stowed safely.
At this stage I haven't used Ebony Star at all. I have simply varnished the parts and that appears to give a very nice surface on the teflon, the action is very smooth and it doesn't move. So I may not even bother with the laminate and just use it as is.
The other thing I have done is made 4 little aluminium "tabs" that are are attached just inside the teflon pads to stop the scopes OTA moving side to side and potentially slippng of the rocker when pointing low.

Malcolm

[mental4astro]

Lovely stuff, Malcolm.

I like the touch of the little aluminium tabs to control the lateral side, ;)

I hope you get many, many good hours with it.

Mental.

[GraemeT]

Malcolm, a great job. I've been pondering the problem of keeping the Altitude rings on the bearings, and the idea of tabs is a good one. Depending on the depth of the rocker box cutout, the side struts should keep the scope from sliding sideways, but with the relatively shallow cutout you've used, you need the tabs. This will also allow the rocker box to be lighter.
Obviously, solving a design problem can be done in a number of ways, and yours is a more elegant solution than my original idea of using a stepped ring.
I also like your idea of the dowel tripod. The only advantage of a photo tripod that I can see would be the ability to level the ground board on an uneven surface.
I'll post some photos of my attempt in a few weeks, as I should have my workshop up and running in our new house by then.

[mercedes_sl1970]

Looks good - and some good ideas - eg the removable legs. I've been pondering (for a while...) something to get my single strut 8" dob up off the ground.

Andrew

[AstralTraveller]

Very nice. The idea of a travel scope has been on my mind recently. I'll be interested to see it packed up.

[barx1963]

Thanks for the replies guys.
Graeme. I originally considered a stepped ring, but it was going to be a complicated solution, and it would probably rub against the side of the rocker bos making it noisy and also mean the whole box needs to be that little bit bigger. The shallow curve were done specifically to reduce the overall height of the box.
Andrew. The only isue with the legs is that the mirror box is only 275mm high (at least is is now, I pulled it apart tonight and reduced it by 25mm) so the legs will stick up 125mm. I have tried to think of a way of making the legs themselves collapsible, but haven't come up with an idea yet.
This weekends project is to work out how it will all pack away. Should be fun!!

Malcolm

[barx1963]

Some more progess.
After procrastination I have glued the Ebony Star to the bottom of the rocker box. Contact cement is no fun to work with but it worked out fine in the end. As the piece of laminate I had was slightly larger than the width of the box by about 40mm, I had to work out a way to trim it. Found a cheap set of router bits at the hardware store that cost about $30 and included a laminate trimming bit. Worked like a dream, really neat job.
Also popped laminate on the alt trunions. That was a little trickier as the laminate was 3/4" with the trunions are 18mm so they are 1mm narrower than the laminate strips. With contact cement there is very little margin for error so I didn't let the glue dry completely, just left it to partially set for 10mins then put the laminate on. I could then adjust it. The problem was that I needed to clamp it, which is obviously not possible with a round disc. So I just grabbed an old occy strap and wrapped that around to hold laminate in place.
I have also cut out part of the base of the rocker box and the front board of the box to reduce weight. Jigsaw made easy work of the laminate surface and finish was nice and clean.
I then rebuilt the rocker box as I was not happy with how square it was then reassembled the entire scope.
Did some observing with it tonight and all working well. Ebony star worked a treat. I was able to use not just the 15mm superview but also my 10, 13 and 17 Ethoi, which I really pleased about. The 21 Ethos and 41 Pan were just too heavy however.

Next jobs
1 Finalise the packing system
2. Final sand and varnish of the rocker box and ground board
3. Glue the teflon pads in place.
4. Decide on paint colour. I was orginally going to just use clear polyurethane varnish all over, but I am considering painting the rocker black to reduce light bounce onto the primary
5. Decide if it needs dew protection or not and if so how
6. Decide if I want to install encoder etc for Argo. I have a set of 4096 encoders that should be OK for a short focal length scope like this

Malcolm