Quote:
Originally Posted by bigjoe
Some of these Barlow types have tradeoffs.
Shorties...their compact and easier to manage, but may cause vignetting in longer focal length say 32mm eyepieces , and even add some astigmatism in the periphery and other problems with such a rapidly changed lightpath...a reason I gave up on the cheapy shorties years ago.
The longer ones ..not so many problems.
bigjoe.
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Hi Rick,
Joe is pretty close to correct. The Orion Shorty Plus (also sold as the Celestron Ultima) was one exception. This was a high quality Japanese made 3 element Short Barlow which worked very well. It had 23mm clear aperture which compares to some other short barlows like the University Optics Klee which only has about 18mm clear aperture and vignettes quite badly with longer focal length eyepieces. The Orion Shorty Plus isn't the same as the Orion Shorty Barlow which is Chinese made POC.
The Orion Shorty Plus is quite good but the longer Barlows like Televue, Dakin, Baader/Zeiss and Astrophysics are slightly better, with the Dakin and Zeiss being the best IMO and just in front of the other two. That having been said, you need good seeing conditions, a high quality telescope and a skilled observer to pick them apart. I owned an Orion Shorty Plus for many years in company with a 1.8x TV Barlow, a 2x TV Barlow and a 2.5x TV Powermate. It compared quite well if just a fraction behind the others.
These are still around 2nd hand and work well in a refractor. I wouldn't recommend any other short Barlow.
Cheers
John B