Celestron 100ED Spotter tested

http://www.buytelescopes.com/product.asp?t=&pid=7092&m=

This second sample has significant coma like the first. I would describe it as usable on terrestrial targets, but the coma counts it out for astro use. Too bad, the color correction is very good, glass is very clean and well-coated, and there are no other issues.

The view through the prism cluster with the ocular removed does not appear square to the objective--exactly like the first sample, presumably giving rise to the coma. Not sure if this is inherent or coincidence. No obvious way to adjust the prism cluster as you can with binos.

The objective cell and prism housing appear to be glued in place, not obviously removable. The objective lens is installed in the front with a retaining ring, removal would certainly void the warranty, but it gives rise to the question: if the objective lens alone was good, would it be worth $569?

Doug, thanks for that report. I for one was waiting on that information. It seems a shame that Celestron is so close but not quite on with this scope. Do you plan to pursue it any further? I look forward to any other info you come up with. Thanks again.
Harry

Saw this model listed a few weeks ago. The product concept is most interesting to me: 100ED spotter with angled EP under 20 in for under $600!!

Considering the Pentax 100ED with straight EP cost 3 times as much, The Orion 100ED refractor is $1k for the OTA alone. The Zeiss 85mm FL is also ~1,500. It would be a major break thru if a top notch 100ED spotter can be had for $1000 with zoom EP. For $600 it would be just short of a miracle! I had an inkling it may be too good to be true.

Erik D

Just to give you an idea what I'm seeing--outside of focus the fresnel rings are oval, inside the same rings in the same direction, coma, no spherical. At the plane of focus, approximately 3 diffraction rings laterally on one side of the airy disk, none on the other. Perhaps a half wave of coma?

At 66x the image on terrestrial sources is sharp, if for no other reason than the aperture advantage. At 22x my own eye abberations dominate--this may well be a good RFT, a super monocular, with a standard-thread low power Erfle.

There is some small violet fringing the fresnel rings, this certainly is a very good color correction result at the price and justifies the ED label. It is far better than the so-called semi-APOs. In focus, there is no sign of the swimming in color that an achromat would exhibit. So colors are saturated and accurate.

The body appears to be plastic, but substantial, not flimsy. The zoom is a wanna-be, easily replaced, too much spherical abberation of the exit pupil, not a good thing in a daytime scope.

Nevertheless, if it were not for the coma, this indeed would have been the dream come true, a bigger, badder Orion ED80.