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Posts Made By: Keith Lawson

July 1, 2007 11:59 PM Forum: Pictures of Me and My Telescope and........

New Toy

Posted By Keith Lawson
I'm writing this just in case anyone was wondering about what kind of performance I'm getting from the 7" F/15 Russian MAK. Since I can't draw well, I've attached a simulated photo that shows what I'm getting at the eyepiece. The color and resolution are exactly the same as what I can see through the scope on an average night. I have yet to have a night of great seeing but the performance of the scope has been stunning. I've looked through a lot of scopes over 30 years and this one stands out in my "top 5" as far as high resolution performance is concerned 8)

I have resolved stars to the diffraction limit with just average seeing (.67"). For me that's impressive for a "CAT" smile

I have also found the light throughput to be quite good. From my home location I can see naked eye to mag 4.2. I have seen stars to mag 12.2 in the scope. This would equate to about mag 14 in an average (6.2 visual) dark sky. Not bad at all smile There must be some truth to the enhanced coatings on the mirrors (95%) and the high transmission multi-coatings on the corrector (96%-97%)

As you can tell, I'm having fun "playing" with my new toy grin

Keith

September 2, 2007 06:49 AM Forum: Telescope Making

Where to buy 3"ID teflon pipe?

Posted By Keith Lawson
Try here: http://www.mcmaster.com/

Teflon in this shape and size is somewhat expensive. I could only find 3" ID with a 1/2" wall thickness so it will have to be machined to 3.5"OD. What's the application if I may ask?

Keith

October 7, 2007 11:51 PM Forum: Telescope Making

From Test Bench to Scope

Posted By Keith Lawson
Front End.

October 7, 2007 11:52 PM Forum: Telescope Making

From Test Bench to Scope

Posted By Keith Lawson
Focuser.

November 13, 2007 05:46 AM Forum: Telescope Making

How did I live without this ? (Bandsaw)

Posted By Keith Lawson
Dave,

I'm looking forward to seeing the nice scopes you're going to build/finish in the near future using your new toy 8)

Keith

January 10, 2008 06:42 AM Forum: Equipment Talk

Whoa!

Posted By Keith Lawson
All,

My concern is that beginners will read such things as gospel and think that they have to spend 10K in order to do good planetary observation. In my experience, all quality instruments have their place. My first 60mm refractor provided me with many pleasant hours of "ignorant bliss".

A rant like this reminds me of Lowell's extreme view that reflectors were useless for planetary work. Pickering's remark that apertures smaller than 5" are useful for nothing other than the study of variable stars shows that even the knowledgeable can be ignorant.

Anyone that has ever used a JSO SCT or a nulled Celestron knows that this guy is full of poop. I have found that optical designs, when well made, are always good performers if you keep them cooled and collimated 8)

Keith


January 27, 2008 12:59 AM Forum: Equipment Talk

Worth $2500??

Posted By Keith Lawson
All,

I just called him and he didn't know the maker, model, size or focal length of the instrument. He said that it was given to him for a job he did. My guess is that he is not trying to rip anyone off. I think that he is selling it for what he was told it was worth by the person that gave it to him. We shall see. He is supposed to call me back with the info.

Keith

May 3, 2008 06:39 AM Forum: Equipment Talk

Will an 180mm Mak be and upgrade to 8" SCT in imag

Posted By Keith Lawson
Hi,

I can't speak for the Orion MAKs but the Intes Micro 180 MAKs are a cut above 8" SCTs as far as high resolution observing goes. If you like tight star images that rival a good APO of the same aperture then a good MAK is the way to go. I had a IM 180 F/15. I was so impressed with it's optical performance that I upgraded to a IM 200DX F/15 for my retirement scope.

I'm using the 200 right now and though the sky is not the best as far as seeing is concerned I can still use 350X on Saturn and the image comes up crisp. Izar is easily split at 122x in this kind of seeing. I ran the scope up to 350x and even though the diffraction rings were a blur on both components because of the seeing, the airy disk was visable and the stars were a very wide split and still tight. I could even get repeated glimpses of Zeta Bootes (.8") in seeing this bad.

I'm trying not to get too wordy here but there is a difference between commercial SCTs and high end MAKs when it comes to high definition observing. I've owned both up to 14 inches. The really good (optically corrected) SCTs are butt kickin' but in my experience they are rare. Hope this helps.

Keith

May 7, 2008 06:17 AM Forum: Maksutovs

305mm f/12.5 Astro-Physics Maksutov-Cassegrain

Posted By Keith Lawson
You're breaking my heart cwy It's like looking at an expensive exotic car knowing that from your vantage point it will always remain an untouchable dream. BTW, you left some drool on the focuser grin

Keith

May 9, 2008 05:29 AM Forum: Equipment Talk

Mak-casses or SCTs optimized for cooling down?

Posted By Keith Lawson
I agree with Roland as far as the removable coolers are concerned. They don't work well where I live. Once you remove the cooler the plume comes back though the plume is much less than not using one. My temperature drops can be as high as 10 degrees per hour (what I call sunset shock).

In my experiments insulating blankets work for moderate temperature drops in the order of 2 to 4 degrees per hour.

My best solutions have been to use recirculating cooling systems in SCTs. The photo shows a C-11 that was modified with a re-circulating cooling system.

I have made mods to C-8s, C-9.25s, C-11s, and a C-14. I have experimented with passive, active and stirred cooling. I found the stirred cooling to be the best bang for the buck.

Keith

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