130mm Truss Tube Refractor

[Jones]

Uses the 130mm f/7 -53 triple from TS Optics Germany.
Wanted to have this mount up on the Stellarvue M2 mount and did not think their completed scope at 22 pounds would work. So this is the result at 14 pounds so far.

[Jones]

Uses the William Optic synta replacement focuser, plumbing fitting as the focuser flange, plywood frame baffles , dslr rods direct from China on ebay, lens cell sandwiched between wood discs, no collimation adjustable yet. We will have to see if my construction skills resulted in a square assembly.

[Lady Fraktor]

Very nice adaption Jones, what do you use for stopping stray light?

[Jones]

Have not thought that far ahead, still trying to figure out how to do dovebar mount, maybe slide completed assembly into a cardboard tube and put rings around that, but big aluminum rings weigh alot and cost much. A work in progress.....

[Lady Fraktor]

Sliding the assembly into a tube is a common method though the exposed baffles give it a unique look.
Perhaps some L shaped brackets connected to the two middle baffles to attach a dovetail to?
Good luck going forward, it should be fun

[DeanD]

Have not thought that far ahead, still trying to figure out how to do dovebar mount, maybe slide completed assembly into a cardboard tube and put rings around that, but big aluminum rings weigh alot and cost much. A work in progress.....

Gabby's L-bracket idea sounds like a good one, but as another option rather than cardboard which has a limited life span, what about a piece of pvc down-pipe? You could mount the dovetail bar directly to this.

It does look like a bit of fun. Good luck,

Dean

[pakarinen]

Brilliant! I never would have thought of a TTR. It will be very interesting to see how it works out. Good luck!

[Unitron48]

Intriguing concept! Looking forward to performance details!!

Dave

[Unitron48]

Here is an interesting thread from CN: https://www.cloudynights.com/topic/5080 ... refractor/. Also one from I-Star Optical: http://www.istar-optical.com/perseus-tcr-150-12.html.

Dave

[helicon]

That's a really interesting telescope design. I have never envisioned a truss-tube refractor...

[Lady Fraktor]

This was the standard way to make long focal length refractors centuries ago to keep them lightweight.
Here is a illustration of Johannes Hevelius 45.7m (150') long refractor from 1641.

Many people still build homemade refractors this way as well before placing inside a tube.
Easy to tweak your f/l and baffle placement.

[Jones]

Loaded up the ota with all needed junk to observe.
Purpose to find balance point and mount bar placement.
Looks like I will use angle brackets to bolt mount bar to wood frames. Weight is now 16 pounds. Think the limit of M2 mount is 18 pounds.

[John Baars]

I came across this picture the other day. I instantly thought about your refractor. The rings that hold the trusses and at the same time act as baffles need to be quite thick for ruggedness. Being so they still bounce not wanted light into the eyepiece. A dark mat painted tin ring cut out of a lemonade can with scissors, attached to the wooden rings, could do the job.
https://www.cloudynights.com/topic/1737 ... -question/ post #13

[Jones]

Been waiting on a roll of flocking from Protostar, but after 2 weeks decided to use what is left over here. Going to go with bare naked framework and a tapered tube of flocking inside the frames. Now do not have any flocking left over for a dew shield. Maybe painted card board for that.

[John Baars]

Quite a surprising solution. I like it!!

[Lady Fraktor]

That is a unique solution! Well done

[Jones]

Scope works great, even the Chinese can build a good dash 53 triple. BUT, at 18 pounds and 32 inch long it does not handle well on the sv m2 mount. Too unsteady at over 300 power on Mars.

[DeanD]

Scope works great, even the Chinese can build a good dash 53 triple. BUT, at 18 pounds and 32 inch long it does not handle well on the sv m2 mount. Too unsteady at over 300 power on Mars.

I am not surprised. The M2 is a good little mount, but the emphasis is on "little". It copes with my 150mm f5 refractor, but I never go over 100x with that one. I have made a wooden alt-az which does the job even better, based on the thought that I would love a 6" discmount, but can't justify the cost...

The mount has a sort of modified Dob bearing but single arm. It is ugly (prototype only!), but it works: very smooth and has a damping time of less than 1 second with the 150 refractor. Cost ~ $40...

I have attached a couple of images: if you are interested in doing something similar feel free to send me a PM and I will give some more details.

All the best,

Dean

[Jones]

It is so hard to get the smooth action of the M2 in a home build. The roller bearing washers under the tension knobs let's you crank in enough stiffness to prevent movement while changing Eyepieces yet still allow easy starting movement. Guess will have to knock back expectations of what it will handle.

[pakarinen]

BUT, at 18 pounds and 32 inch long it does not handle well on the sv m2 mount. Too unsteady at over 300 power on Mars.

Don't remember the M2C specs, but I'm surprised. Moment arm (?) too long?

The mount has a sort of modified Dob bearing but single arm. It is ugly (prototype only!), but it works: very smooth and has a damping time of less than 1 second with the 150 refractor. Cost ~ $40...

I have attached a couple of images: if you are interested in doing something similar feel free to send me a PM and I will give some more details.

Hey Dean, may I suggest you post something under DIY? That could be an interesting project.