Telescope Reviews: Celestron 25x100 Skymaster Binoc

Celestron 25x100mm Skymaster and 15x70mm Skymaster - Long-term review.

I have owned my 15x70mm Skymasters since Christmas of 2004. My wife got them for me
after I dropped some hints that stargazing might be a positive way to get me out of
her space while she paints and crafts. Of course, neither of us anticpated the case
of raging apeture-fever that those 15x70 Skymasters brought on. By the time our income
tax refund came the following April, we bought the 25x100mm Skymasters in an effort to
quench my thirst for more light and more power. Now that I have owned the 15's for
six months and the 25's for three months, I have noticed a few idiosyncracies that
bear mentioning. My first review of the 25x100mm Skymasters was posted on Cloudy Nights
shortly after I received them. At that point in time, I had only used them to stargaze
on a few brief occasions. That review, which is linked here, was mostly based on my
first impressions of the binoculars. This review will provide a summary of my thoughts
and observations since that time. Also, I will include my thoughts on the 15x70mm
Skymasters, which I have not officially reviewed up until now. Lastly, I will comment
on quality-control on these Chinese-made binos and "fit and finish" issues.

I want to state, first and foremost that I am pleased, overall, with my purchases from
Celestron. In terms of "bang for the buck", these giant binos cannot be beat. Having
said that, prospective owners of these bargain binos should be aware of a few niggling
issues that come with the cheap price. These issues are not deal-breakers, but whether
or not an owner can tolerate them will decide whether these binocs are good buy.

1) The diopters are loose. At first, the left diopter was tight and the right was
slightly loose but barely noticeable. Over time, the right has gotten very loose
and the left has come loose as well. By loose, I mean there is a good bit of play in
the focusing wheels. Also, the "shroud" around the left diopter that has the focus
indicator on it is loose and it now revolves independent of the focusing wheel it is
attached to. So the left diopter is now the worst - it wiggles in place and the
marker piece is loose as well. I worry that the lack of fit between the focusers and
the eyepieces may mean that the eyepiece-assemblies are not sealed well. This could be
a potential intrusion route for humidity. As of yet, this has not happened. The diopters
still function well, but the right eyepiece still does not have the clarity that the left
has. I find it hard to get a good, crisp, clean focus. Again, the focus issue is not
so bad as to be prohibitive, but it is a source of nagging doubt.

2) The integrated tripod mount is not tight and there is a persistent wiggle between the
stabilizing bar and the mounting base-plate. No matter how hard one tightens the big
knurled knob on top, the binocs will wiggle. This is due to a tiny screw that keeps coming
loose on the binoc housing where the tripod-stabilizer bar joins the binoc body. When the
screw is tightened, the wiggle disappears. But inevitably, the screw works itself loose and
the wiggle will return for the next night's session of stargazing. I have gotten into the
habit of keeping a tiny screwdriver in my goodie-bag just for the purpose of keeping this
screw tightened. This is not a major issue, but it is another one of those bothersome
things that I wish would go away.

3) The image quality is inconsistent across the FOV. This is to be expected with the so-called
"bargain binocs", but I find it particularly bad on my 25's. The centermost area of the FOV is
crisp and clean. But the quality fades quickly as one moves away from the center. A rough
guess on my part is that about 1/3 of the FOV is essentially unusable for serious observing.
These binocs, and my smaller 15's, have a "sweet spot" which in the case of the 25's is slightly
above and left of the FOV-center. This is where I try to position my viewing targets. Oddly, the
FOV appears to be better on my smaller and less expensive 15x Skymasters. I attribute this to
poor quality-control in the Chinese production factories - more on this later.

4) There is a noticeable amount of chromatic abberation present in the FOV. I really noticed this
when I viewed Venus recently. There was a distinct and bright presence of green and yellow that
changed as one's angle of view moved. However, I will say that any false color is far less noticeable
when viewing stellar targets and DSO's. The false color has only been noticeable when doing planetary
viewing. Another strange thing I noticed about the chromatic abberation on these binocs, is the lack
of said abberation while viewing in the daylight. I have heard numerous times that astronomical binoculars
produce a lot of false color during daytime viewing. I have not encountered this problem on the occasions
where I used these binocs for bird watching and looking at distant targets at the beach.

5) The dew shields are too small. Perhaps it is the overwhelming humidity in my local area, which
southern coastal Louisiana is infamous for, but I found the objectives were dewing up very quickly on
nights where the humidity was otherwise marginal. I concluded that large objective lenses like the 100mm
present a lot of glass-surface to the open air, and thus attracting dew like mad. I solved this problem
by making a set of custom dew-shields from PVC fittings (4-inch collars) which extended the factory
dewshields by almost 200%. This completely eliminated my dew problem. I cannot understand why binoc
manufacturers do not include bigger dew shields in their designs. The materials and plans I used to make
the dew shields can be found at this message-thread on Cloudy Nights.

Ok, those are the issues about the 25's I do not like. All of these problems can be attributed to one or
two factors : quality control in the manufacturing process, or "fit and finish". And example of the quality
control issue is the optics quality. My smaller 15x70mm Skymasters have a more consistent and crisp FOV than
my 25's. The 15x70's focus easier and cleaner and there is no discrepancy from one ep to the other as is
present on the 25x100's. Also, the "sweet spot" in the 70mm is larger as a percentage of the total FOV than
in the larger 100mm model. Given that the 100mm model cost more than double what the smaller 70mm sells for, it
only stands to figure that the production batch of my 70mm models were superior in optical quality than the
batch of 100mm binocs that my other model came from. Both were likely made in the same factory, using the
same overall process, so one must question the quality control of the optics.

Secondly, the fit and finish on the 15's is superior to that of the 25's. This is not just a personal
preference of mine for the rubber-armor on the 70mm over the "skin" that covers the 100mm model. The bigger
binocs have a "looser" overall feel that has not gotten better with time - example, the screw in the tripod
adapter that keeps working loose. In comparison, my 70mm Skymasters have held up well. The ep's are still
tight, the diopter is tight and focuses well.

Such issues as quality control and fit-finish are realities of the binocular market. And that is the main
difference between 100mm binocs that sell for $200.00 versus high-end 100mm binocs that sell for $1000.00.
Wiggly screws, false color, "sweet spots", and loose diopters are not to be expected on Fujinons or other
Japanese-made binocs of comparable size. But if you can live with such issues, then the Celestron Skymasters
are a good bargain. I believe that a giant pair of 100mm Celestron binocs will allow you to see more
stars and "deeper" into space than a smaller pair of optically-superior and more expensive binocs. The difference
lies in the CRISP and BRIGHT views that are seen in high price binocs that are consistent across the vast majority
of the FOV (or the entire FOV in some cases).

At any rate, I plan on sending my pair back to Celestron at some point in the very near future to either have
the replaced or serviced to fix the diopter issues and address the poor quality optics present in my particular binoc.
My experience with taking them up on their "No Fault Lifetime Warranty" will hopefully be the source of a future
report that is more positive and satisfying.

MikeG

--------------------
Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.

Galactic Stone & Ironworks - Buy/Sell/Trade Meteorites, Moon Rocks, Mars Rocks, & 35 different falls and types!

Edited by Bebs (07/07/05 08:38 PM)