再转帖一篇TMB4"的评测,里面有 VS FS102的内容:
1) TMB Fluorostar 4" f/8 APO (4" f/8 triplet refractor, 7X50 finder, $2300-$2800)
From Thomas Back comes a fine new line of apochromatic refractors.
I saw Back's 6" version of this scope at Astrofest this year (1999) and
was dutifully impressed. Along with Roland Christen's expensive glass
in the adjoining booth, these were among the most popular items at the
show on both nights. I received the 4" version as a review sample,
and couldn't wait to put it through its paces.
Another great 4" refractor -- the TMB Fluorostar
The mount is the GM-8
These scopes carry optics from Russia, while the optical tube assemblies
are sourced from Taiwan. The optics are designed by Thomas Back and
made in Russia by a Zeiss subcontractor. Back does final bench testing
and star testing on each lens here in the US. If they don't meet his stan-
dards, he sends them back. The Taiwanese connection tends to raise some
eyebrows, but you shouldn't worry. The machining and finish work are first-
rate. The focuser is massive, and carries huge focusing knobs, which look
just like the AP focusers, only larger. A chrome bat-wing handle serves as
the focus lock. The scope comes with a 70 mm extension tube that you can
remove to accomodate a binoviewer without a barlow, if binoviewers are your
thing.
The entire tube is finished in a nice metallic pearl-white, with tasteful
gold (yes, real gold) accents. The scope is huge for a 4". If you told
someone it was a 5" refractor, they would probably believe you. The mech-
anical tolerances are very tight. When you extend the dew shield or focus
your eyepiece, a whoosh sound escapes from the tube. The tube is very
heavy, but will work on a GM-8 with only one 7-lb counterweight. For those
looking to save money, the same optics are available in a Vixen-based
mechanical assembly. If you buy this scope, however, you want the
nicer mechanical assembly. Believe me. You just do.
According to Back, these new scopes are true apochromats which are "highly
corrected for chromatic and spherical aberration..." I tend to agree. Two
of us present could not detect any errors in a star test on Vega at 164X.
Detail on the massive focuser
The optics use SD (super low dispersion) glass as the center element, with
two matching hard crown elements as the outer elements. All surfaces are
multi-coated. Light throughput is said to be 96%. Another innovation is
the use of a temperature compensated cell, which is said to maintain precise
collimation and reduce stresses on the lens elements on the objective during
large temperature swings.
We compared this telescope to a Takahashi FS102, which has the same
aperture and focal length. We also had several duplicate sets of eyepieces
on hand, so side-by-side comparisons were easy.
The first thing you notice is that the Fluorostar is impressively well-
corrected for chromatic aberration. I could see no false color at all,
no matter how high I pushed the magnification. I never thought I would
say this, but in comparison, the FS102 almost looks like a semi-apo-
chromat. Really.
About the only detriment I could find on the Fluorostar is a slight contrast
loss when looking at bright objects. The sky is not quite as dark as in
the Takahashi. Mind you, the effect is mild. According to Back, this is
an inevitable result of having an air-spaced triplet. You win on color
correction but you lose a little on contrast. It all depends on your
priorities. I'll take the superior color correction any day, but the slight
loss in sky blackness caused one observer present to say that he pre-
ferred the Takahashi by a small margin. I also noticed that there are only
three baffles in the Fluorostar, while the Takahashi has eight. (According
to Thomas, he is investigating adding another baffle of some sort, probably
near the eyepiece end.)
Other than that, there isn't much to talk about. The Fluorostar is a
world-class refractor, right up there with the AP, Takahashi, and
TeleVue apochromats. We split some doubles and looked at the
popular early-fall deep sky objects. Both scopes did wonderfully well.
Later in the evening, both the Fluorostar and the FS102 were delivering
stunning images of Jupiter. Again, we noticed the Fluorostar had better
color correction, while the Tak had a blacker background.
While it's hard to predict the future, Thomas Back appears off to an
auspicious start. The Fluorostar feels more like a mature product from a
company that's been around the block a few times than a first effort from
a new company. The scopes are currently available through APM in Europe
or from Thomas himself.
Recommended for discriminating refractor lovers.
Update, 3/26/00: Newer versions of these TMB telescopes are said to
have superior baffling inside the tube, and improved multicoatings. Owners
tell me that these new TMBs have superb contrast. One reader, who also
owns an FS102, says the TMB actually beats the Tak on contrast. While I
have not verified this for myself, if this is true, then these newer TMB tele-
scopes could be really special. |
置顶卡
变色卡
千斤顶
显身卡