The stringscope will have a shroud made of black ripstop nylon. This will assist with stray light control onto the primary mirror dust particles, stray light entering the focuser and help keep dew off the mirrors. There will also be a removable (400mm) dew shield attached to the UTA, this will complete the dew protection for the secondary and stray light control for the focuser.
Yes I will be using a black ripstop nylon shroud over the outside of the truss (classic Dob). I am planning on a 400mm dew shield attached to the front of the UTA ring. I will probably use 5mm black closed cell foam for the dew shield.
I have made some progress with the stringscope. All components (except shroud and carry bag) now complete. All have been checked for fit and function and I have just carried out a final check laying it all out on the garage floor.
Remaining tasks:
All wood components to be painted.
Primary Mirror bonded to cell.
Secondary mirror bonded to cell.
Teflon pads drilled and countersunk for fixing screws.
Accessories drawer foam insert cutouts for eyepieces etc.
Then.......put it all together......
While I had the camera out .......... a photo of one of the Canberra Astronomical Society hire scopes. This scope has been allocated to the introductory group (I am one of the coordinators) it has been out on hire for the lst 3 months but I couldn't convince anyone to hire it at the last meeting.......oh well I will just have to use it myself for the month. It is a great scope, 4" F10 and really sharp. Comes with a set of orthoscopic eyepieces and is great for the moon and planets. Perfect height to use seated and the whole thing can be picked up and carried one handed.
Originally posted by stringscope While I had the camera out .......... a photo of one of the Canberra Astronomical Society hire scopes. This scope has been allocated to the introductory group (I am one of the coordinators) it has been out on hire for the lst 3 months but I couldn't convince anyone to hire it at the last meeting.......oh well I will just have to use it myself for the month. It is a great scope, 4" F10 and really sharp. Comes with a set of orthoscopic eyepieces and is great for the moon and planets. Perfect height to use seated and the whole thing can be picked up and carried one handed.
ps. It also carries John Dobson's signature 1995.
Cheers,
The wood work on this telescope looks like a work of art. Who built it?
seeker372011, The circles I cut out of wood are made with a router and a jig and they come out as perfect circles.
seeker372011, yep Ed is correct.....router with circle cutting radius arm. Makes cutting circles really easy. The only circles I have cut with the router to date are the ones in the photos. The ID for the altitude bearings was too small for the radius arm so I cut them free hand........not quite so good.
Ed, the little 4" dob is one of my favourite scopes. I believe it was built by a past CAS member who was also a musical instrument maker. I think the tube in particular is a work of art. Very light weight. Sides are 2mm ply wood with an internal frame including baffles and some sort of textured fabric lining glued to the inside. This scope exhibits excellent contrast.
I made some additions and matched the staining as closely as possible:
Holder for star atlas and instruction manual.
Holder for tube end caps.
Eyepiece drawer (extended in the photo).
Small accessories box (opposite side of mount to eyepiece drawer and out of photo).
Steering handle under front of tube.
All stringscope components have now been painted/coated as required.
Outstanding tasks:
A very minor balance issue to resolve. I can either move the altitude bearings 5mm or I could use a light virtual spring counter weight. If I use a virtual counter weight, then I could also fit a 50mm finderscope!!!!!
Azumuth bearing a little too firm.....still thinking on this one. I might replace one of the teflon pads with a roler bearing. I thought I might have some issues with this and the ground board it only temporary pending final design.
Protrctive covers for both mirrors.
I decided not to have the mirror recoated at this stage pending some detailed star testing. (I was never able to do a proper star test in the original Celestron Starhopper due to secondary mount and focuser issues. Star test last night between cloud bands and in pretty ordinary seeing indicated the mirror is probably worth keeping.
Shroud and dew/light shield to be fabricated.
Equipment drawer foam liner to be cut out for EP's, filters etc.
Erecting and collapsing the truss takes about 30sec each way in daylight and taking some care not to drop one of the segmented tension tubes onto the primary mirror.
It appears to hold perfect collimation between assemblies, bearing in mind this is an F6 system. I have only run it through 3 assembly cycles and a collimation check using a cheshire collimator indicated it returned to the previous collimation setting each time.
When complete assembly steps will be:
1. Removal from car.
2. Remove scope from carry bag.
3. Extend truss.
4. Attach finderscope and eyepiece.
5. Collimation check.
6. Attach shroud and dew shield.
7. Place carry bag back in car.
8. View.
I guess from removal out of the car to viewing should be no more than several minutes.
The craftsmanship on the telescope seems to be first class. Well done!
I like the blue and the black those colors always work well together. Great paint job. I am just curious on the preparation of the wood before the paint, how many coats does it have, it looks like it's been sprayed on .Very nice indeed.
You know Ian, you guy's are fantastic! you build these dobs and they end up looking better and working better than bought ones! Im talking about you too ED!
The wood is Hoop pine ply wood. Interier flat black acrylic. Exterior sanded down to 240 grit with an orbital sander. One undercoat followed by 4 coats of "marine blue" epoxy enamel. "Sanded" between coats with a kitchen scourer. Trouble is, I didn't count on the mirror finish showing ALL (and I mean all!!) the blemishes.........sigh.......I haven't done any thing like this before. I will know better next time!!
Elapsed time was about one week.
The painting is all brushed. I do have a spray gun but the thought of setting up a spray booth in the garage was all too much.
I am just doing a few minor mods, should have its first serious observing session next weekend.
You know Ian, you guy's are fantastic! you build these dobs and they end up looking better and working better than bought ones! Im talking about you too ED!
Louie
Thanks Louie,
Telescope making for most of us ATM's is a work of love. Last night George came over and we were star testing a new secondary for my telescope till 1pm now thats dedication.
The craftsmanship on the telescope seems to be first class. Well done!
