Posts Made By: George Kiger

There's an Abbe Ortho being auctioned. I know these are legendary, and have proven themselves in the field. My question is why are they so good?

I would think that modern makers could surpass the orthoscopic design, and that modern coatings would make things even better. Why is it (if that is true) that this old eyepiece is tops?

The seller's claims of besting a variety of high-end instruments, including some more recent AP offerings made a fun read. It also made me think about TMB's 'AP brief history' article and his description of the launch of Astro-Physics as a full time endeavor for our hero.

"The August 1986 issue of Sky and Telescope might have been the most impressive ad for its time. Seven apochromatic refractors were listed, and the most impressive was the 6" f/12 Super Planetary for $1540. The ad read: "Our new long focus refractors are designed for the most discriminating Lunar/Planetary observer who does not want any compromise in performance... The Lunar limb and the disks of the planets are sharply outlined against black sky, resembling charcoal drawings."
- from http://www.tmboptical.com/itemsGrid.asp?cat_id=28

The specs show coma = 0.1734 and very little astigmatism - I thought the RC was designed to have zero coma and a fair amount of astigmatism.

It is well known that malaria is a significant problem in some parts of the world, but did you know that it is Global Warming that causes the spread of malaria!!!

KOLKATA, India—After the fumigation of the streets and a leafleting campaign, people turn up at one of the 60 state-run clinics for malaria treatment, 2004. About 160,000 people die every year from the effects of global warming, which include malaria and malnutrition. This number could nearly double by 2020.
© Donovan Wylie / Magnum Photos

--Caption on a photo in Slate.com's pictures-of-the-day section.

Light gathering in terms of point sources (stars, for example) will be the same. For extended objects, the f# is just like on a camera - the lower the number, the faster you can record the object - a 4-inch f/6 will record and extended object 4x faster than will a 4-inch f/12 (but the f/12 will have a larger image scale - the object will, at the image plane, occupy 4x more area in the f/12 system). I suppose this is another way of saying that a 4-inch gathers as much light as another 4-inch.

In the right angle set, why would the prism be aluminized?

You would never see the difference, but with that CZ primary I could not bring myself to go with the lesser option.

Great question and lots of interesting responses.

I was using a 60mm, f/15 refractor (don't remember the brand), but my 'dream scope' was a 5-inch Unitron.

You'll get better advice if you also include what telescope(s) you are using.

I will echo the others comments on Barlow/Powermate - no need to avoid if you get a good one. You might want to try the TMB 1.8X Barlow - one of the very best, and only about $180.