Glass circle

[Orion]

I decided to cut the secondary for the 24" today.
Being a three mirror telescope the secondary was cut in a circle which was a lot easier than cutting glass at a 45 degree angle as I normally do for the secondary.
The cutting tool was easy enough to make just a round bit of ply and thin galvanized ion screwed around the edge.
I made a dam on the glass around the tool to keep the slurry from going all over the place and away I went.
The only grit I had was 220 but it seemed to do the job nicely and it took two hours to cut all the way through stopping once in a while to add grit.

[cristian abarca]

Hi Ed . a few questions. What type og glass is it how thick and what size is the circle you cut out.

Regards Cristian

[Orion]

Its plate glass 12mm thick and 180mm dia.

[[1ponders]]

:bowdown: Ed, I take my hat off to you home mirror makers. :bowdown: I'm flat out cutting glass in a straight line, let alone cutting a circle. :scared: What skill and patience.

[janoskiss]

Wow! That's impressive. That's going to be one hell of a scope! :eyepop:

[RB]

Ditto to what Paul said Ed.
Amazing stuff.

Thanks for sharing and keep us updated.

[h0ughy]

pretty ordinary effort Eddie;) ! will you cut the leftovers for the 3rd mirror:P ?

so who is missing a window?

I george getting this one this weekend?:)

[Orion]

Thanks guys.
I cut the blanks and build the telescopes but George grinds and figures the mirrors.
This telescope is going to be a challenge.... but I like that.

[Orion]

[QUOTE=h0ughy]pretty ordinary effort Eddie;) ! will you cut the leftovers for the 3rd mirror:P ?

QUOTE]I already have (from a different project) several squares of class in different thicknesses which have been laminated together with melted wax in between the class. These squares are put in a suitable wooden box at a 45 degree angle and then cement is pored in locking the class in place.
A pipe is used to drill straight in the top of the box through the cement and the glass resulting in beautiful elliptical secondaries or in this case tertiaries.

[Astroman]

Do you have drawings with dimensions for this little baby? If so where can I see them. Where did you come up with the design?

[ving]

your seconday is as big as my primary!!!! :eek:

[Orion]

The only drawrings I have are on my computer. Here are some pics but I'm sorry for the quality it's the best I can do.
When the telescope is standing straight up the focuser will be 1660mm from the ground, just right cosidering I am 5'6.

[h0ughy]

[QUOTE=Orion] :bowdown: :bowdown: :bowdown: :bowdown: :jawdrop:

[Astroman]

OKay gonna ask a stupid question or two here now.. Is the Secondary a flat or convex? Also is the tertiary mirror held in by a spider aswell?

[Orion]

Convex and yes tertiary is held by a spider.

[Satchmo]

Hi Ed

Excuse me for needing to play the Devil's advocate here ;)

I don't understand why you want to go so thin ( 12mm ) for your 180mm folding flat ? Your optical system is only as good as the weakest link, and if going for commonly available material like plate glass I would recommend at least 19mm if not 25mm thick , to give yourself any hope of a rotationally symmetric figure . I'd say that making a 12mm thick X 180mm soda lime glass spherical 'flat' that would be of any use is a very difficult task because of its flexability and low thermal inertia.

Mark

[Orion]

Oh well, we'll see what happends if the 12mm dosen't work we will make another untill it does work.;)
It's all good fun.
Thanks for the advice Mark.:thumbsup: