First Light For Stringscope

[stringscope (Ian)]

Well my stringscope achieved 1st light tonight (2nd light for mirror). I had to recheck focal plane position before fabricating the "string" truss assembly. What better way than starlight from Alpa Centauri.

Jobs completed:

Upper tube assembly.
Mirror box.
Electrical panel.

Major jobs outstanding:

1. "String" truss assembly.
2. Altitude bearings
3. Recoat primary mirror.
4. Rocker box.
5. Lots and lots of little jobs.

Cheers,

[astro_south (Andrew)]

Nice one Ian

Must be satisfying to reach this stage of the construction (must have been fun aligning alpha Centaurii that way too!!)

Can't wait to see the finished product.

[[1ponders] (Paul)]

Wow Its amazing what you can do with a bit of string Ian

[mch62 (Mark)]

Great job and excellent to see another ATM on the forum.
Have you seen Mel Barlels and Dan Grey from the states string scopes and spiders?

http://www.bbastrodesigns.com/tm/tm.html
http://www.siderealtechnology.com/28inch/

Mark

[Orion]

Hello Ian, Great stuff! Love to see home built telescopes.
Are you trying to determine the truss assembly length in that photo?

[mch62 (Mark)]

Orion that's the fun part i remember from making my truss scope.
As a double truss with a mid mounting point getting the balance made it even more fun
There are programs around that have been written to calculate the lengths and balance points for truss scopes but i found them even harder to work out .
I used Newt 2.5 first to get the overall length and then using a weight set set up a balance beam and mounted components on the beam except for the mirror and just adjusted every thing untill I got the balance while keeping the over all length the same.
This workd out for me.
But every one has there idea that they hope will work for them.
Good luck with scope.
Mark

[stringscope (Ian)]

Thanks for your words of encouragement guys.

I first became aware of the "stringscope" concept from Dan Grays web site. There are quite a few of them out there now from Graig Colvin (6") to Dan Gray (28").

By conducting a star test, I was working on the basis of measure twice and cut once, at least thats my excuse. In fact the truss length is not super critical as I have 60mm of available mirror cell travel on the collimation rods. The reality was I couldn't wait, I just had put it together and see if it all worked.

I have attaced an image looking down into the mirror box.

Cheers,

[Striker (Tony)]

Nice one Ian....

OMG your telescope is invisible...hehe

[mch62 (Mark)]

That look like you can adjust your collimation from the top?
That would make the task easier.

[mch62 (Mark)]

Why go any further .
Who needs a tube when a big beam will do
This looks like your scope

[Orion]

That's the way!
A couple of mirrors and a pole and you have a telescope.

[stringscope (Ian)]

Mark,

Wow...... is it a "beamscope"?? what is it??

yes, front collimation access. This design feature allowed me to locate the batteries and electrics at the very rear of the mirror box to provide greatest counterweight effect. They are thermally isolated from the mirror by a sheet of plywood and there are 2 80mm fans for mirror ventilation.

Some of the inspiration for this design came from the Portaball and Teleport scopes; front collimation access, single ring UTA, accessories drawer in rocker box and carry bag.

Photo of mirror box internals. Electrics next post.

Cheers,

[stringscope (Ian)]

Rear electrics panel.

[ving (David)]

man that looks weird!

great job mister!

[iceman (Mike)]

Awesome Ian, top stuff! Looks great.

Aside from portability and the "made it yourself" kick, what are the other benefits of that design? Wouldn't you get a lot of off-axis light bouncing off the mirror?

[mch62 (Mark)]

Hay ice I might be able to shed some light on that question

You have seen my avatar and see that my mirror is even more exposed , no box at all.
I don't have a problem with stray light , even from the street light near my home.
The only time it becomes a problem is when the light is coming from directly behind or the front of the scope.
It then will get onto the secondary or primary and cause problems and for that I have a black felt shroud that can go around the scope once it has cooled down real quick.
The most important part that need to be protected all the time is directly behind the focuser .
You need to have some thing to block the light going directly into the focuser , either a full tube for the end or a baffle opposite the focuser.
I can shine a torch beam straight through the side and it has no effect or little.
You have to remember your physics and the angle of incident and reflection stuff to relize what it will take for light to get into the focuser and eyepiece.
If you have light coming from the side of a scope onto the mirror it is going to bounce off out the other side depending on angles , and for it to make it's way to a focuser at right angles to the mirror ---well
You don't see many research scopes with a full tube , not even shrouds just a darkened area.
A full tube will of coarse be better if you surronded by city street lights.
Hope this helps.

Go Trusses

[Starkler (Geoff)]

Originally posted by mhodson
Hay ice I might be able to shed some light on that question

You have seen my avatar and see that my mirror is even more exposed , no box at all.
I don't have a problem with stray light , even from the street light near my home.

I imagine that you would have to keep that mirror scrupulously clean though, being able to scatter light from most any direction back toward the focuser.

[ving (David)]

just one word.... dust particles!

well, ok 2 words. you would have to clean more often wouldnt you?

[mch62 (Mark)]

What don't you guys keep your mirrors clean
It's very easy to clean with out having to remove the mirror and possible loss collimation.

[ving (David)]

yup a bit of steelwool and industrial cleaning agent 'll do the trick hey!

(this is a joke to all newbies out ther)