Posts Made By: Keith Lawson

The six screws on the primary housing and the power plug (located inside the handle) are the only evidence of the stirring cooling system installed on the last C-9.25 I owned.

Keith

Here is my mod to a C-14 using the "spinning" method.

Here is a close-up of the fan assembly.

Here is a rear view of the fan installation.

I have purchased two scopes from Mark and his customer service is first rate. He always answers questions promply and he knows what he is talking about concerning the products he sells. No hype! Pure high performance!

Keith

I've owned my share of long focus Newtonians in my decades long quest for Newtonian planetary perfection As with all things, there is no free lunch. Observing from a ladder or step stool is tolerable for a time but for me grows old. I much prefer sit down observing.

If I could find a lens maker that wouldn't charge "through the roof" in the fabrication of a 40mm cemented doublet I would have a nice solution for a planetary Newtonian.

Though the idea is not new, a permanently mounted telenegative amplifier (barlow) would solve a lot of issues concerning constructing a planetary Newtonian.

1. A long focal ratio scope could be achieved with a relatively short tube.
2. The obstruction could be easily kept to 20% while fully illuminating a 1/4 degree FOV.
3. Common glasses in the barlow/corrector would keep the cost of glass low.
4. Performance of the barlow/corrector would have a diffraction limited field of 23 arc minutes (almost 1/2 degree).
5. Visual high performance could be achieved with "standard" eyepieces.
6. The resulting large image scale would be good for planetary CCD photography.

I produced such an instrument many years ago. It performed quite well but I would like to take it a step higher by using a lens designed specifically for the optic concerned thereby attaining even better on and off axis performance. Here is a 12 inch F/14 Newtonian using a standard F/5 primary. Any lens makers out there?

Keith

I ran some experiments on a scope of similar design and here are my results:

1. The diffraction limited field should be at least .6 degrees (full moon).
2. The distance between the meniscus and the primary is not critical.
3. Centralization of the primary vs the meniscus must be held within 2mm (.078").
4. Both curves on the meniscus must be held within .2mm (.008")of the design specification.
5. The meniscus tilt must be held within .2 degrees.

I think these tolerances can be accomplished with modern CNC machines and optical equipment. IMO quality control will be the final issue. I'm looking forward to the first review by a fellow Amarter. If anyone can think of any other constraints I would be glad to run them.

Keith

Maybe they just want to upgrade to the new models and need scope funds

Keith

I always thought it was a way of saying mint condition but in a slang/cool way. Like: So, what is the condition of that scope? Minty baby 8)

Thanks for the heads-up! I will be out with my mounted 11X80'S

Keith