Posts Made By: Keith Lawson

I have more but I will end here with a "stirred" cooled C-9.

I don't claim to be an expert, experienced maybe but no expert. I have not had the pleasure of using an NS but my CPC-1100 is excellent both mechanically and optically. If I had to rate the optics compared to the five C-11s I have owned this current system would tie at the top with an Ultima I rebuilt some years ago. A 250 line grating at 3 bands (outside focus) are straight and well defined with a clean edge. Out of focus patterns are very close to identical and on nights of good seeing the airy disk is well defined and of "textbook" quality.

I don't know if the optics were made in America but the Bob's Knobs I installed were metric. GOTO's are incredibly good. Tracking is superb.

Lunar/Planetary views are very good as long as the scope is cooled to ambient temperature and well collimated.

Hope this helps.

Keith

Check this out: http://intane-optics.com/products/apo-152-f-8-57-catalog-1.html

I would be interested in a 7" F/10. Estimated cost?

Keith

Good looking project 8) Nice woodwork. Can't wait to see it finished and hear your observing report

Keith

**1, inexpensive 6"F/8 Doublet ED as replacement for Skywatcher, celestron, Meade 6"F/8 achromat lenses**

Markus,

You can put my name on the list for one of these if they become availiable. [email protected]

Keith

Looking forward to your report on the finished OTA 8) Keep us posted on how the progress goes and please give us all the details

Keith

Sweet 8) Looking forward to your "field tests".

Keith

All,
As we all know, you can tell how good a company is not by what they sell but how well they support you after the sale, especially if there is a problem with their product. As with most companies, a lemon can slip through the production process from time to time. I had planned on giving a report on the 203mm F/9 lens that I received from Istar Optical but there was a problem with the lens. Instead of blasting the company with a bad report on the web I decided to wait and see how they would respond to the issue concerning the lens since I had plans on buying more lenses in the future.

Ales of Istar Optical answered all of my e-mails promptly and apologized for the inconvenience. He spent all the time needed to work with me on resolving the issue. I do admit that I was a bit nervous since the company was fairly new and I had spent all my hobby funds for the lens purchase, but my fears were unfounded.

Through our e-mail discussions, Ales and the optician had a clear understanding of the lens problem. I was informed of the time required for a new replacement lens. They were true to their word and delivered the new lens in a timely manner. Even though Ales was traveling back to Germany, his representative in Arizona made sure e-mail communications remained open and shipped the product on time. Now that’s customer service! I can’t say I have always had this type of service with other companies I have purchased from over the years. I would rate Istar’s customer service as first class. Communications were clear, prompt and they completely resolved the problem. Would I buy another lens from them? Yes, without hesitation. They stand behind their products and care about their customers.

Now, on to the lens test:

My original test involved an optical bench using an artificial star placed at 150 feet. During the “down time” waiting for a new lens I constructed a “rail scope” that allowed me to do my tests using the night sky. Here are my results:

The weather has not been kind with wind, bad seeing, rain and high clouds.

Ronchi Test (250LPI Glass grating at 2 to 3 bands): Edge clean, bands straight and of high contrast.

Star test: About 1/6th wave. The visual test matches the interferogram. (.168PV .014RMS)

Mars (9arc sec): Details clearly seen on the globe.

Saturn: Crisp and well detailed when the seeing allows.

Multiple Stars: I have not had a night good enough to “go the limit” but stars like Eta Gemini are child’s play. Zeta Orion is clean split even in sorry (2-3/10) seeing. All six stars in the trapezium are very easy.

Chromatic Aberration: I was expecting a lot of color but was surprised how little there was considering the focal ratio.

The seeing has not allowed me to push the telescope hard but eventually I will. The lens is a very good one. For the refractor purists, yes, I will install the lens in an enclosed tube. Currently I’m having fun with the rail scope.

Keith

Well... Had a couple of fairly decent nights and this lens ranks as one of the better ones I have ever owned. Last night I split 78 Ursa Major in 5/10 seeing. I could detect .5" Zeta Bootes under the same conditions. I could see the polar cap on Mars and the melt line as well.

Tonight I was able to see Rhea only 1.9" away from Saturn's globe (144x). 5 moons visible. I also beat my personal record of over a decade ago when I could see the Cassini division in Saturn's ring as a well defined arc through a 12.5" F/8 reflector with Saturn's rings only tilted 3 degrees. Tonight I could see the division as a black arc with the rings only tilted 2.5 degrees (360x TMB 5mm Planetary Eyepiece/Williams Optic 2" 99% diagonal). Seeing tonight about 6/10. Division seen multiple times during moments of steadiness (about 1 sec). Seeing gauge: Airy disk visible but faint rings broken up by the seeing (Zeta Orion). Can't wait for a good night.

The limiting visual magnitude here in Lancaster, CA is 4.5 ( I live in the middle of town with many street lights in my area). I was able to see a 13th magnitude star last night. So the light transmission is quite good.

I would have spent more time but I have to work tomorrow. Man! I hate daylight saving time > Having fun

Keith