Most
amateur astronomer would agree that Televue has set and been the gold
standard in premium quality wide field eyepieces, offering superbly
crafted, well corrected, flat field, chromatically sound eyepieces at
a premium price. Al Nagler and company have consistently produced
eyepieces that amateur astronomers have used for comparing all other
eyepieces to. So, it should come as no surprise that when Explore
Scientific introduced its 14mm 100 degree eyepiece to the world of
amateur astronomy that it would be compared to the 13mm 100 degree
Televue Ethos.
However,
before we get into all of that let me say that this is a review of a
premium 100 degree AFOV eyepiece and that although I purchased the ES
14mm, I also own the 4.8mm and 7mm Televue Naglers as well as the
University Optics 32mm MK-80 and 25mm MK-70, in addition to the 8mm
and 3.5mm Orion Stratus eyepieces. So, I can honestly say that I do
not have any particular preference to one brand over another. Like
most amateur astronomer, I purchase and use those eyepieces which
give the most pleasing views for the price I can afford.
Now
let’s get to my initial impressions; the ES 14mm is a large 2
inch eyepiece that weighs 2 lbs; it has a clean ergonomic overall
design that fits nicely in your hand with a wide nubbed rubber grip
band that provides for confident handling. Since the ES 14mm is
advertised as being nitrogen purged and waterproof, I should probably
mention that this is feature has merit, promotionally it makes the
eyepiece unique, but more importantly by sealing the eyepiece and
purging the air with a dry inert gas like nitrogen it should increase
the life of the coatings and prevent dust or condensation from
forming on the interior surfaces and elements. The eyepiece comes
package in a sturdy box lined with high density die-cut foam that
holds the eyepiece firmly in place during shipping; both ends have
dust caps that fit securely. The rubber eye-guard is rolled down when
the dust cap is attached. The 2 inch barrel is smooth but slightly
tapered narrower at the housing end that should provide a little
assurance that the eyepiece will not accidentally slip out of the
focuser. Each eyepiece has a unique serial number and comes with a
mail in registration form for its 5 year transferable warranty. Upon
close visual inspection I found it to have no defects, scratches, or
fingerprints, the elements are fully multi-coated as advertised and
there was no visual flaws noted. I mention these facts in detail to
illustrate the care and high quality attention to detail that Explore
Scientific takes.
I
purchased my ES 14mm from Astronomics out of Norman, OK from
non-other than Pete Kron, who incidentally is the original builder of
my 18” f/4.5 truss-tube Dobsonian. As you all know, anytime one
purchases something for our astronomy hobby (addiction, obsession …)
the weather gremlins send you cloudy skies. This time was no
exception, almost immediately after I hung up the phone with Pete our
weather here in SE Michigan began to change from clear skies to
cloudy, raining and windy. But here in Michigan we have a saying, “if
you don’t like the weather, wait a minute and it will change.”
So, I waiting and after a few days the skies threatened to clear,
well at least clear enough to do a little initial testing. As it
turns out, my good friend and observing buddy John Causland was
having a picnic party on Friday, July 3rd
at his house to watch the fireworks his home owner’s
association puts on to celebrate Independence Day and new eyepieces.
(Okay, they didn’t know about my new eyepiece) John owns a 24”
f/4.5 Starmaster and as luck would have it a 13mm Televue Ethos, that
we will use to do some side-by-side comparisons with. After the
fireworks, a small group of my club (The University Lowbrow
Astronomers) gathered around my 18” f/4.5 a.k.a. the PK-457 to
put the new eyepiece thru its paces.
Before
I get into the results of our testing I need to point out some
caveats; first of all none of us are optical designers or engineers,
we are simple but experienced amateur astronomers that have looked
thru enough scopes and eyepieces to know what to look for and what we
like. Secondly, these initial tests were conducted under less than
ideal conditions, the skies were rather hazy (7/10) and somewhat
unsteady (7/10) and with a moon that was 4 days from being full. But
since both eyepieces would be used under the same conditions I feel
that any comparisons are still valid.
Prior
to these observations under the night sky, we did take the
opportunity to do a little day light testing of the ES 14mm in Jim
Forrester’s 4” f/6.5 Astro-Physics Apo. We focused on
some power lines a few hundred yards away. The first thing I noted
was that the entire length of the power line was spot-on in-focus
across the entire field, everyone concurred. The next thing I looked
for was any fringe color or hint of it, there was none, and again
everyone concurred. Jim mentioned that the power line which was
running horizontally thru the FOV appeared to be curved, I pointed
out that the power line did sag a bit on its own, but Jim thought
that it appear more curved than it should. So, to test if the ES 14mm
was causing this I nudged the scope a little bit to put two power
lines in the FOV, one of the power lines running thru the top half of
the FOV and one running thru the bottom half. If there was any field
curvature (like a fish-eye lens would produce) the power lines should
show different amounts of curve, there was no difference visually
evident in the two power lines, both had the same sag, and Jim
concurred.
Okay,
lets move on to the night sky testing, as I said before the sky
conditions were not the best, but here in SE Michigan you have to
take what you get and make the best of it. Due to these less than
perfect conditions we confined our testing to brighter objects. The
side-by-side comparisons of the ES 14mm to the Televue 13mm Ethos
were blind to everyone one but myself and we only used the PK-457
scope for our testing. We tested with and without a Paracorr and the
consensus is that neither eyepiece needed the Paracorr. Our test
targets included the Moon, M13 and M11 here are the results and
impressions. Tester involved were Jim Forrester, Mike Radwick,
Charlie Nielsen, Chris Sarnecki, Dave Snyder, Paul Walkowski, John
Causland and myself.
Moon
with an Orion Variable 2” Polarizing Filter:
Both
eyepieces showed an equal apparent field of view, a gorgeous 100
degrees. Both fields were very flat and were sharp right to the field
stop. Resolution appeared equal, but as time progressed the Moon
began to edge into a tree and made this difficult to judge. A very
slight yellowish rim around the non-terminator edge of the Moon with
the ES 14mm was noted by one of the observers. The Televue 13mm Ethos
showed a very pale blue tint to the same edge, and it spilled across
the face somewhat this may have been induced by the polarizing
filter.
M13:
Resolution
to the core, very tight stars, good contrast considering the
Moonlight. Again, both eyepieces were sharp right to the field stop.
No appreciable difference between the eyepieces was noted. Blind
results: 4 preferred the ES 14mm, 1 preferred the Televue 13mm Ethos
and the rest including myself felt there was no difference.
While
observing M13 I nudged the scope a bit to see if I could fit M13 and
NGC 6207 in the some FOV and the answer is yes. Now with M13 on one
edge and NGC 6207 (a small spiral galaxy) on the other edge of the
FOV any everything across the field in focus at 170x, this was not
only a beautiful view, but a nice test of the eyepieces. Even on the
very edge of FOV the core stars of M13 were still clearly resolvable
and the galaxy’s shape and structure were wonderfully evident.
M11:
Tack
sharp stars with no pin-cushion effect noted in either eyepiece, all
of the field stars were perfectly focused right to the edge. Contrast
was very good and even across the field. Blind results: 4 preferred
the ES 14mm, 1 preferred the Televue 13mm Ethos and the rest
including myself could not decide.
The
overall impressions of those who looked thru both eyepieces was that
they are of the highest quality and well corrected to produce flat
even fields, tack sharp focus with no visual evidence of any type of
optical aberrations. I am anxious to do some additional testing under
better conditions. One thing that was noted by everyone was the
eye-relief of the ES 14mm is noticeably longer than that of the
Televue 13mm Ethos; this made the ES 14mm a more comfortable eyepiece
to use. The ES 14mm is noticeably heavier than the Televue 13mm
Ethos, and is only available in 2” format (the Televue 13mm
Ethos is both 1.25” and 2”). With all of this being said
and when you look at both eyepieces side-by-side and the views they
give, the only real conclusion I can draw is that there is no optical
/ performance difference in these two eyepieces. That leaves price,
both eyepieces are not cheap, however the Explore Scientific 14mm 100
degree is introductory priced over $200 dollars less than the regular
price of the Televue 13mm 100 degree Ethos. My only question is when
will Explore Scientific begin production on additional focal lengths
… I could use an 8 or 9mm and a 19 or 20mm for my collection.
|
