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Zeiss semi apo

Started by Paultricounty, 05/11/2002 04:17PM
Posted 05/11/2002 04:17PM Opening Post
Is their anybody that has experience with the Zeiss AS100/1000 and AS80/1200 Semi apochromatic refractors. How are the views {visually} with this type of scope? How do these scopes rate visually and mechanically with some of the good achromats and ED refractors on the market today? I know for the price of one of these scopes one could buy a decent 4" apo. {Their is a collecting consideration in mind} How pleasing would the optics be on contrast and sharpness?
Any information is greatly appreciated. Thanks.
Posted 05/12/2002 07:13PM #1
Hi Paul. I've owned several scopes in this size range and currently use an AS80/1200 for my "small" scope. There's no question that it's the sharpest and most contrasty of any scope of this size I've owned or looked through (including a Tak FS-78) and provides more detail on Jupiter, the Moon, etc. Also, although it's termed a "semi-apo", it might as well be called an apochromat... I looked at Venus the other day and saw no blue color. On the limb of the Moon, there's just a smidgeon of color off axis but none on axis. No more "extra color" than in my Tak FS-78.

Having said that, it has some drawbacks. An f/15 refractor, even an 80mm, has a lot of torque and needs a pretty good mount to hold it solidly. I use a GM-8 now and am happy with it but have tried smaller mounts and found them too shaky. Also, the field of view is limited to about 2.17 degrees with 2" eyepieces. Most folks want an 80mm to provide them with a wider field of view. Finally, it only shows what an 80mm scope can show. The light-gathering ability is clearly limited and resolution maxes out at 1.5 sec. Also, as sharp and contrasty as it is, a top-notch 100mm will show more lunar/planetary detail (though a less than top-notch one won't).

My particular tube was made in the 60's by Zeiss and I've seen at least one other tube like it on Astromart (APM had one for sale several months ago). Usually, though, I think the AS80/1200 shows up for sale as an objective and you can build the tube (or get it built) to your specs.

Hope this is useful.

John

Posted 05/17/2002 05:48AM #2
Paul, there is an AS100/1000 objective for sale in the German-language section of eBay. The item number is 1353461446 and if you search on that number you'll reach the auction. (This note is placed on the 17th of May and there are still 9+ days left to the auction.)

Cheers,
John