Posts Made By: P. Lee Stock

I've done both. No problems except to check your focuser to ensure you don't cut off a drawtube stop that prevents the drawtube from racking completely out--there might be nothing to prevent it from coming out and smacking the ground with your eyepiece in it. The other issue is how to finish the hole you cut in your optical tube assembly if you put the focuser on the inside since you will be able to see the ragged edge. If you can properly address these two issues, then go for it.

I've been slowly piecing together a simple, but elegant (I hope) 6" f/5 truss scope. The idea is to make a truss assembly that can be used in a couple mount variations:

1) A highly portable and very lightweight travel/packing telescope, and
2) A nifty rotating truss tube, RA tracking telescope.

The optics are first rate--I've seen more crisp detail in Jupiter and Saturn than with any other scope I've owned. I know a lot of amateurs wouldn't consider a fast, small newtonian much more than a beginner scope, or a toy, but I think that is misguided thinking ;^).

I plan to finish the travel version first, then I'll work on the artistic wooden and electric/electronic mount second. What is shown is the interchangeable portion almost complete. It is very simple, made mostly from leftover stuff , but I like it thus far.

All thoughts/comments/complaints welcome...

Here's a photo of a StarBlast bucket tripod I made for my 6-year old son's new telescope (which is an amazing buy for $119, by the way). We dressed it up a bit with Formica and rubber T-molding, but the essentials are a wooden top with three rubber feet to keep the StarBlast from slipping off and three (ugly) wooden legs screwed to the inside of the open end of the bucket to serve as tripod legs. I may add some nicer legs to the outside of the bucket to widen its stance, but we found in practice that the scope doesn't really want to tip, though you tend to exercise a little bit of care. It is stable and doesn't shake, and you can fill it with goodies on the way to the observing sight.

Time has been hard to come by the past couple months, I finally got a couple days off to wrap this up, hopefully will have it complete by Saturday.

A 6" f/5 like this one is a tiny little thing. I don't have a total weight yet, but I hope it comes in at less than 12 lbs when I'm finished. The tripod will be carried over from a previous project--so I just have the azimuth "ring" and altitude bearings left.

The entire thing should easily fit in overhead storage in an airplane with room for 2 day's worth of clothing in the same suitcase.

I had the exquisite mirror that will be going into this telescope in a previous telescope and decided there is something wrong with the prevailing attitude that a small to medium aperture reflector of short f/ratio can't be worth looking through--I've looked through a LOT of premium scopes and views through these 6" f/5 optics on planets is up with the best. Plus it is also a wonderful widefield instrument with enough aperture to go DSO hunting from a dark site--happily pursued since everything, observing stool included, will fit in a small bag.

I don't think I could make telescopes without a router, a small metal lathe and a Dremel tool. Practically every small part was either made on or found it's way onto my 7x10 lathe for modification.

The spider vanes are steel banding strap. The center hub is nylon turned on the lathe. Upper ring cut with a router. Truss poles are 5/16" aluminum arrow shafts. Bottom connectors are tent snaps/buttons screwed onto more nylon I turned on the lathe glued onto the shafts. They don't come unsnapped--I've shaken the entire assembly violently and it doesn't unsnap, or loosen--it's tight.

Upper trusses slide into nylon I shaped on a bandsaw and are wedged apart by carefully cut and bent steel banding strap. Works great and cost nothing.

Primary centering and side support is accomplished with rubber stoppers I cut in half--squeezing down on them with hex grommets fattens them until they perfectly center the mirror. Velcro tabs mate with sticky-backed Velcro on the mirror's side for safety. Both mirrors are easily and quickly removed for safer transport.

Fan power for ultra-fast cooling (already fast with the open structure). Dual 9v pack switches the 2 batteries from series to parallel to run the fan at high power for fast cooling and then 1/2 speed for thermal maintenance.

Focuser is a heavily modified Celestron unit I almost threw away, but it was lightweight and not sloppy, so I reconsidered its potential for this project. Cut off the curved base and lowered the profile to less than 2" tall. It is mounted immediately off the light cone, so while it is still nearly 2" tall, it is equivalent to being inside the tube on a typical newt and still has about 1" of travel.


More to come tomorrow or Saturday...

Being very short on time lately while still wanting to mount and use my new 8" f/6 Bob Royce refigured mirror, I purchased a Starhopper listed for local pickup here in Salt Lake City so I could use the mount. (I put my “Tent Snap Telescope” project on hold so I could finish the Starhopper project this weekend).

Swapping mirrors, I got the immediate gratification I desired (and found my Royce mirror to be excellent), but quickly discovered all of the Starhopper's shortcomings. So I went to work overhauling the Starhopper into a real telescope, with excellent results:

1) Stiffened the rocker box with aluminum C-channel

2) Moved the azimuth bearing pads from an inadequately tiny radius on the ground board to the corners of the rocker box and applied Ebony Star to the top of the ground board

3) Replaced the pitiful nylon altitude bearing tape with Teflon. Soon found this made altitude movement too smooth with the small Starhopper trunnions, so I added Velcro (loop side) to one trunnion--now I can switch eyepieces without having to rebalance and the alt movement feels just right

4) Better feet from nylon rod turned on my lathe--there were originally six short rubber "feet" that hardly kept the ground board off the ground

5) Made new azimuth pivot assembly

6) Rounded over rocker box corners and applied rubber T-molding to prevent abrasion that happens during transport

7) Swapped tubes for one I had stored away—new tube is covered with countertop laminate on the outside and black velvet on the inside (I had stored it because it was an early attempt at gluing velvet and it had some areas that didn’t stick well—oh well, perfect for this).

8) 2-inch focuser

9) Secondary holder assembly: nylon turned on lathe, steel banding strap for the vanes

11) Three comfortable handles—one for the tube and two for the rocker box to aid in repositioning as necessary during observing

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And he "threw in" a Glatter collimator for the $600 asking price too? ;^) Lucky buyer!

PS - In case the ad gets deleted: 8" Zambuto Starsplitter, JMI Focuser, Rigel, Glatter Collimator. $600 + shipping.

When I've used silicone to mount a secondary mirror in the past, I've always given it a good 1.5 to 2 days to cure--always seemed a good precaution.

That said, I used silicone to attach a 1.52" secondary to it's nylon holder this morning at 4am and am considering hanging it over my primary mirror tonight--maybe 16 hours later.

Whad'ya think? Am I pushing it? Would YOU do it (especially if you knew it would be at least a week before you could go out observing again)? ;^)

"Premification" of the Starhopper continues...

I made a tube-length sliding balance system yesterday using a 7/16" OD dowel--it was light and cheap and was right in front of me at the store.

It works great, but I want something either pure black or unfinished aluminum in color. Because you slide weights up and down it, painting it seemed out of the question, so I blackened it using wood dye-stain, but I can still see a bit of underlying wood color. Maybe Sharpie marker ink?

Better yet, do any of you keen thinkers know of a ready source for 3/8" to 7/16" OD hollow, lightweight, aluminum rod without going to sources like McMaster-Carr and Texas Towers? I confess I'm being cheap with this and grunging it out in the true spirit of ATM'ing ;^)--I know I could spend $25 on a piece of aluminum rod and be done with it.

P.S. I drilled out and filled the nylon counterweights with BBs. Ever hefted a small carton of BBs?

For an 8" mirror, the price difference is negligible between standard protected aluminum and IAD enhanced coatings (only available from one vendor?).

So while I am not certain the benefits of this enhanced coating are significant, for only $20 or so more, I merely wonder if the potential drawbacks of this particular coating are known to anyone. Specifically, what is the nature of this coating and its potential harmful effects to a mirror's figure. And how difficult is it to remove later on?

Finally, can anyone speculate on the best way to remove paint from a mirror's surface--my mirror was amateur made about 13 years ago and was refigured by Bob Royce in '99, who fought to remove a wide TDE, diminishing it to a narrow ring that has been blackened with paint. Do you think it will come off when the aluminum underneath it dissolves, or will the coater curse me for not removing it first? If the latter, who can recommend how to best take it off? Acetone? Paint thinner? I obviously don't want to do any damage.

Thanks!

Last week I would probably have sworn all the world needed was a better understanding of the half-nut; today, threaded rod couldn't be straight enough and I'd have given anything for a .316" reamer .

This is an untested EQ platform concept, as of yet, but I wanted to show you guys what I came up with.

So, as it goes, I had decided there really wasn't a good reason why a tangent driven EQ platform with instant reset couldn't exist (does it??--I've never seen one) and set about to rectify the problem of having to rewind the drive nut to start position and other such silliness with a concept that's been in my head for the past few months. I powered it up today and, while I'm sure it will work, I may be surprised, or not, to find periodic error unacceptable. The difficulty lies in the linkage between the motor and threaded rod... and perhaps the straightness of the threaded rod itself.

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