Last updated: 4 January 2006
Subject:	Eyepiece review
Sent:	Sunday, January 1, 2006 21:17:48
From:	The Brown Family (chrisbrown4@cox.net)
Here's my latest attempt to make my ETX-90 M into a deep-sky instrument!

Celestron E-Lux 40mm vs Celestron 40mm Kellner.

I guess I just don't give up easily. When I heard that the ETX-90 wasn't
well suited to deep-sky work, I took exception...After I hauled my
telescope to the darkest of dark sights (see Galaxy hunting with the
ETX-90 ra, User observations.), I have been bent on proving that the
little "90" was a viable deep-sky instrument...I was bent enough to
convert a 2-inch 38mm Erfle to a 1.25 inch format just to prove my

Once again I found myself in the high desert of Yucca Valley on New
Years eve, just east enough to avoid the upcoming storms of the season.

My goal, to test 40mm eyepieces, under dark conditions...

I recently acquired a circa 1980's Celestron 40mm Kellner (circle-T)
which I had high hopes for, seeing the low glass count, which may let in
just a little more details in faint objects. I also had a modern Plossl,
the 2005 Celestron 40mm E-Lux, with it's 31mm eye relief and 43 degree
apparent field, not to mention modern coating technology.

The targets, M42, M78 and M1,(try finding these Nebula in the city!),
and the 3 little stars that skirt Alcyone, in the Pleiades,which I chose
to test the limits of magnitude for the little 90mm.

The results: M1 remained averted vision only, but both eyepieces
performed identically on this faint object. M78 was slightly brighter
than M1, but again, I couldn't discern a difference in the eyepieces!
The triangle by Alcyone has a dim component that blinks in and out with
direct vision, on both eyepieces, again a draw...

On M42, I could just see a little more detail with the E-Lux, possibly
due to better seeing in a slightly turbulent atmosphere.

Despite the seeming equal performances of the eyepieces, I must give the
nod to the E-Lux, and here's why...

The E-Lux had a very wide FOV, easily framing the 7 sisters with no
distortion at the edge, or obvious black-outs at comfortable eye relief
levels...The Kellner, however, had a much narrower FOV, and the eye
relief was non-existent...I have a hollowed-out barlow that I use that I
use as an extension with my high power Orthoscopic eyepieces to keep my
nose out of the stock finder...this was the first time I had to use this
extension on a 25MM-plus  eyepiece!

Bottom line, the vintage Kellner was a match for a more modern eyepiece
in terms of resolution, the Kellner was pin-sharp right to the edge of
the field...at a price, but why settle when you can have the best of
both worlds, a wide FOV, great eye relief, and sharp views?

Chris Brown

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