Thermal Equilibrium. The OTA must be as thermally equalized as possible. To my non-mechanical-engineering way of thinking, this means: all critical parts of the OTA should thermally equalize at the same rate. If they didn't, the two mirrors of the Newtonian would become closer together and less accurately aligned as the temperature goes down. If all parts of the OTA lost their heat at the same rate, the mirrors would stay aligned during the thermal process. I could be wrong. But assuming I'm not wrong, the implication of this is: all parts of the OTA should be of the same proximate material: aluminum, or composite. This means 1) aluminum tube, mirror cell, spider, and focuser. OR 2) carbon tube, carbon cell and spider and carbon focuser. There is ONE exception I can think of at the moment: Blacklite tubes (fancy cardboard) probably have C.T.E. close to that of carbon. So an OTA of 3) Blacklite tube / carbon cell, spider, focuser might be good. Economically, the carbon solution is orders of magnitude more expensive than aluminum, right now. But I'll investigate both. There is one company I know of making carbon primary cells, I have to find that company and email.

Today I ordered my PRIMARY MIRROR for the GalaxyBuster.

I ordered an 8" f/4 conical primary (3.3 lbs) from RF. Royce in Connecticut.

I sent a $100.00 deposit, for a mirror that will cost $795 and take a few months to get here.

Just ordered the tubing from Hastings!

I ordered 4' of 10.0 O.D. .064" tubing.

That makes an inner diameter of (10.0 - .064) = 9.936", which is OK for the primary mirror cell that I'm going to order soon.

Now I'm going to --gasp-- order my primary mirror.

I'm going to order an 8" f/4 conical cross section primary, center spotted with normal coatings (those 'enhanced' coatings never pan out for me--too difficult to remove) from RFRoyce in CT. Everything I've read is good about rfroyce. I'm going to take a chance on him. He wants a down payment of $100 and residual $695 when mirror is done, about 3 months from now.

The Idea was born months ago

I had the original idea months ago: a fast Newtonian that's good for galaxy observation. Of course I love Saturn's rings and Jupiter's Great Red Spot as much as the next guy, but for me, the absolute wonder is in the galaxies. Looking in the eyepiece at a galaxy, some barred spiral galaxy, so far away that it actually fits in my eyepiece yet is physically big enough to match our own Milky Way, is just mind-numbing to me.

Currently I own and have been using a Celestron C9.25 on the CGEM mount. I don't like it. There are many reasons I don't like it, but many, many people DO love that telescope. I'm going to sell mine to someone who will appreciate it. Then I have to obtain, somehow, the telescope I WANT: an 8" f/4 Newtonian, lightweight conical mirror, aluminum tube, etc....I'm only going to find this one place: my workshop. I can't BUY this. It's not sold anywhere. Most of these fast Newtonians, billed as "imaging" Newtonians, are made in China and use cold-rolled steel tubes, cheap steel parts like primary mirror cells, etc...they're not precise instruments, with parts matched for inter-dependent excellence. The parts are matched for monetary profit on the unit.

I have also been pondering a UNIQUE and maybe STUPID saddle mechanism to mate my Newtonian to my CGEM, which will allow fairly easy tube rotation and lighter saddle weight than a $550.00/ 10 lb. pair of rotating rings (which must be mated to the tube with bolts).

First step is the idea. That step is done.

Second is the realistic appraisal of success: That is done. I'm likely to fail at this, but I'm trying anyway.

Third: Start the parts.

So, TODAY: I'm calling Hastings Irrigation in hope of ordering the tube(s) I need.

I plan to get 3' of 10" tubing for my main Newtonian, and a secret second tube for my super secret saddle mounting project.

Enough! Off to work.