Posts Made By: Keith Lawson

Installed and operational. This mod is not for deep sky observing but for lunar/planetary/multiple star observing. This mod is not worth it for average optics. Tonight's testing (very average seeing) revealed cleaned up images. No more temperature spikes and moving undulations from a warm primary and secondary. Looking at the out of focus star tests, the boundary layer on the primary is non-existent. The temp plume from the secondary, non-existent. Even when the seeing is bad, the stars remain round. Six moons of Saturn, easy. Visually split the .9" double next to Procyon at a mere 140x. That would be tough with a good 6" to 8" refractor at that magnification. The testing will continue...

No outside air is introduced into the system. Dust is a non-issue. The system is recirculating so no filters are needed.

That's just sinful (WOW!!!) There are dreams, and then there are DREAMS Forgive me, I didn't mean to get drool on it!

Keith

John,

Here are the numbers from ATMOS using your information. I don't think your mirrors are close enough to each other. Hope this helps.

Keith

I only needed three pieces of felt but the six are shown for clarity of the idea. It's a nice slip fit. Be careful not to be too aggressive while inserting it. Otherwise you will have to collimate the secondary. This is for C-11's only.

I have one. I wouldn't recommend it for critical testing any optic faster than about F/6. At F/6 or less it will only reveal gross errors (surface roughness, turned up/down edge, zones, etc.). The grating is not fine enough for critical tests of any short focus telescope IMO (faster than F/6). A 250lpi glass grating eyepiece is better for more serious testing. At F/5 or less I would recommend a 300lpi grating. The picture shows the result of using a 133lpi grating with a 8" F/5 mirror telescope at the focuser. Pretty straight bands at 1/4 wave

Many years ago I used to think that any grating was ok for testing any telescope. I was wrong. I used my Coulter "telescope tester" at star parties and thought I knew how good or bad some telescopes were. A 1/4 wave F/5 Newtonian and a 1/10th wave F/15 refractor look a lot alike with a 133lpi eyepiece grating :S I only found out later that the grating chosen must be fine enough work with the focal ratio of the instrument it is testing.

A 1/4 wave F/5 Newtonian and a 1/4 wave F/15 refractror look quite a bit different at the eyepiece using the same eyepiece grating. The view would cause you to praise the Newtonian as "nicely corrected" and condemn the refractor as inferior even though the wavefront of both would be identical.

As is well known, a 1/4 wave telescope at F/5 is much less forgiving in critical optical performance than a 1/4 wave telescope at F/15.

Keith

Bob,

I would go with the C11 if I had a CGEM. There is a lot to be said concerning Push-To vs GO-To. In my experience 1 inch of aperture does not make much difference in scopes this size. There are many other factors to consider in your choice as well. Ease of setup. How often and how far are you going to have to transport the scope if at all? What are your favorite deep sky targets? This would determine how much field of view you need. Do you live in an area where dew might be a problem? How often are you willing to collimate you scope for best performance? Newtonians tend to go out of collimation more often then SCT's. I could go on but if I were you, I would write a list of things I want the telescope to do (observing and mechanical) and see which one fits the bill the best.

BTW, I did own a C11 and an Orion XT12g (recently) at the same time.

For what it's worth,

Keith

OK. I'm not trying to cause any trouble but since no one else has asked: Are you claiming this is a "new" telescope design or a "new to you" telescope design?

Curious about your "C5 uncoated air spaced super achromat". Who made the lens and why do you call it a super achromat? What's so special about it?

Keith

Well... I thought I was getting a great Cave mount when I purchased it on Amart. Everything was fine except that the motor drive was dead. Anyone who has spent the time trying to find a replacement motor for a 40 year old Cave mount can feel my pain. I wish the seller had mentioned that in the ad. Anyway... I really liked smoothness of the all ball bearing Cave mount and happened to have a spare drive from a Meade Starfinder mount that I had modified with a "floating" worm carrier. I was able to attach this to the Cave mount. Everything went together quite well 8)

I plan on buying a "modern" motor and making the needed bracket so I can put the original gearing back on the mount.

The scope is more of a mutt now than before. Scratched up OTA mounted to a Celestron CGM dovetail plate, attached to a Cave mount with a Meade Starfinder drive :S

Keith

I had the 8" and 12". They were great performers for all types of observing. As far as the drives were concerned, I had both for over a year each and the drives worked well with no failures. I did have to adjust the friction clutches (the 12) but after that no issues. The clutch on the base is much more of a chore to get to though. Orion support has PDF files for the clutch adjustments if needed. As far as creaking noises, I only noticed it sometimes when I was hand slewing the scope (the 12) and the "noise" was minor to me. BTW, the hand slewing is not Dobsonian smooth since you are working with friction clutches installed on each axis. IMO, the scopes are designed to use the drives for all motion.

Hope this helps.

Keith

Is this what you are talking about?

Keith