Clash of the Titans II:
Takahashi's Revenge
The AP155 Takes on the Takahashi FCT150
by Ed Ting
Updated 5/7/01
(Complete Version)
(Note:Read Part One first if you haven't already)
The AP155 and the FCT150
(Mounts: AP400, AP900)
It was NOT a dark and stormy night. In fact, it was a clear, calm, steady
one. Night had settled in like a cool blanket under late March skies, ready
for inspection by two of the finest -if not THE finest- six inch telescopes in
the world today. Would the AP retain its crown? Or would the new kid, a
high-zoot hand made upstart from Japan, walk away with the prize? Which
would win?
I get letters. BOY do I get letters. Ever since the publication of the Ultimate
Refractor Clash last November, in which the AP155 narrowly but unanimously
defeated the FS152, I've heard a steady stream of complaints from the Takahashi
faithful. It was not fair (goes the argument) to compare a conventional doublet
like the FS152 to the AP155's triplet design. The FCT150 is said to be the more
fair comparison. It doesn't seem to matter that I never thought I would get within
a hundred miles of an FCT150, or that the FS152 already costs twice what the
AP155 does. Inquiring minds demanded to know, which would win in a direct
shootout?
I am the luckiest man in the world. I had the use of an FCT150 for two weeks
under decent skies here in NH. Besides the FCT150 and the AP155, I had
a Traveler, 7", 10" and 11" Starmasters, the AP 10" Mak, Meade's 178ED, and
the 20" Obsession. Trying to make the most of this time I arranged a comparison
with the mighty AP155 with multiple observers over several nights. It was as
if the FS152, having lost, had gone home and returned with its bigger brother.
By the way, many of you out there seem fascinated by the goings-on here at
Scopereviews Central (otherwise known as my garage and den.) We're often
seen as a bunch of guys who have the time and energy to talk about telescopes
all day and observe with them all night. How I wish this were true! Reality
is more sobering. We have jobs, families, commitments. We are landscapers,
engineers, public defenders, salespeople, construction workers. Putting
together these comparos is a huge undertaking involving days (sometimes weeks)
of planning. Equipment and people have schedules that sometimes conflict, and
then there is the weather. According to the latest data, the Manchester, NH
area gets about 92 clear nights a year, which gives us a 1 in 4 shot of getting
these comparos in on schedule. Some of the observing sessions you read about
here are, in fact, the only times during the entire year when all of us are
together.
The AP155 on the AP400 mount
I point this out because as much as I try to control the variables on these
tests, they can be decidedly unscientific. The tests were conducted over
several evenings, of varying seeing quality, and not all the observers were
present at all of the sessions. Several other scopes were present besides
the AP155 and the FCT150, but not all of them were around on all the nights,
and one of them wound up taking an early exit (more on that later.)
We put the AP155 ($5,400) on AP's excellent AP400 Goto ($3590+) mount. The
AP400 is designed to carry 4" and 5" refractors, but it turned out to be just fine
for the 6" as well, even at high powers. The Takahashi FCT150 ($17,995) was
mounted on the AP900 Goto ($5950+), which is fast becoming my favorite near-
heavyweight equatorial mount. Both mounts performed flawlessly, and in the private
e-mail surveys that were returned to me, there was just as much admiration
expressed for the mounts as there was for the scopes themselves.
Several observers gathered around for the first night under clear, dark skies.
Right away we noticed the Takahashi had trouble setting down thermally,
something I learned to compensate for on subsequent nights (I started
dragging it outside as soon as I got home from work.) A 6" hunk of fluorite
is a big load to bring down to thermal equilibrium.
These are beautiful telescopes to look at as well as through, and everyone
admired the craftsmanship from AP and Takahashi. In the "lust" department
though, there was a clear preference for the Tak, which has an astonishing
level of fit and finish. Simple tasks like pulling off the dew cap, or racking
the focuser, are palpably sensual. In the final tally, six of the seven
observers said they preferred the Tak's appearance and mechanics.
It was convenient that the two scopes have almost identical focal lengths,
and eyepiece matching was simply not an issue as we have multiple sets of
Naglers, Panoptics, and Plossls at our disposal. AP Maxbright diagonals
were used.
Right away we all knew that the FCT150 was going to put up a much bigger
fight than the FS152 did. The Takahashi has a better star test than the AP,
which is very slightly overcorrected. But you have to get up pretty high in
power to see the spherical aberration in the AP155, near 350X. No color was
noted in either lens, a testament to their engineering. Collimation was
dead-on in both scopes.
On Jupiter and Saturn, you could have fooled me into thinking I was looking
through either scope. It didn't seem to matter what powers we used, or what
objects we looked at. The planets were razor sharp against an inky black
background. Cassini's Division was seen all the way around Saturn. Dim,
low-contrast festoons were just as visible in the Tak as in the AP.
On deep sky, both refractors are stunners. Looking at M37, M36, M38, and
M35 will make you forget all your worries for a while. The stars were diamonds
on velvet. The Eskimo at high power seemed to smile at us while we were
looking at it. On object after object, just when I thought I'd found some
dim feature that couldn't possibly be seen in the other scope, I'd wander
over and...there it was.
I ran a limiting magnitude test on both scopes using M67. This is exacting,
tiring work, but it can reveal a great deal. In theory, an air-spaced triplet
like the Tak's should transmit very slightly less light than the oil-spaced
unit in the AP, which has only two air-to-glass surfaces. On the AP155, I
was able to hold the 13.94 magnitude star with direct vision about 75% of
the time. On the FCT150, I was only able to hold the same star with direct
vision about 25% of the time. So they are very close, in the 13.9 region,
with a slight edge given to the AP. Recall that any time you get over 13.0
with a 6" scope, you are doing very, very well.
Takahashi's lusty FCT150
There was only one slight difference I could detect between the two scopes,
and it relates to the discussion above. After several hours of observing, I
began to notice a tiny, tiny loss of contrast in the Tak, compared to the AP.
The effect is minimal, but once I trained myself to see it, I could see it on
almost any object.
Looking at the scopes later in the garage revealed one possible explanation.
The older FC series featured an uncoated fluorite internal element, air spaced
(the newer FS series solved this problem, with the fluorite element out front,
and multi-coated - what'll they think of next??) Shining a flashlight into the
FCT150's lens does reveal two reflections that are slightly brighter than
the others. On the AP155, all of the flashlight's reflections were dim, even
dark, indicating almost no light scatter and reflectivity.
I have to be careful how I express differences like this, since these statements
are often blown out of proportion. It took me a good three hours of steady
observing through both scopes, side by side, before I could see this difference
in contrast. Once learned, it was steadily more visible. But under casual,
semi-serious, and even most serious study, this teeny tiny contrast difference
is practically invisible, and not meaningful in any way. I only mention this
because the FCT150 is intended as a cost-no-object product, and should be
treated as such in a review. In the surveys that came back, Dan S seemed to
be the most vocal about this contrast issue, and myself probably the least so.
To close these thoughts, it should be pointed out that the lens design on the
FCT150 is from an earlier generation. There's nothing wrong with it, it's just
older. I'll point out that earlier AP refractors, from the era which includes
the fine Star12ED, also used this uncoated internal element design. All of
Meade's current ED refractors also employ this arrangement.
Starmaster's 7" Oak Classic nearly matched the views on the refractors. On
a tracking equatorial table, it's more difficult to justify the megabucks needed
for one of the apos. The only downside of the little Newt was its secondary
diffraction spikes on bright objects like the planets. The 10" EL fared even
better, with big, bright views on deep sky and planetary views that were very,
very close to the refractors. The Starmasters got everyone's vote in the
"value" category.
Mike's 178ED has already been through a lot (details elsewhere) but unfortuna-
tely its troubles weren't over. Several people noticed that its views didn't seem
up to par. Later that evening, returning home with the scope, Mike noticed
that one of the welds holding a baffle inside the tube had broken, and the
baffle was now sitting loose against the focuser. It's on its way back to
Meade.
The real competitor, however, came in the form of the imposing 10" AP Mak-
sutov. Only about a dozen of these exist in the world today, and its $9800
price tag makes it the most expensive AP ever (it is still cheaper than the
FCT150 though.) Under the right conditions, the big Mak took no prisoners;
it was the best of them all. Seeing Jupiter with a pair of 32 mm Plossls
in the binoviewer is something you have to experience. But it will not do
low power, wide field views like the refractors will.
As the nights went on, we became less critical and began to enjoy the scopes.
I made mental notes about the comments being made, and in general observed
the behavior of the club members. The lines were just as long for the FCT
as for the AP. When I wanted to find something, I would just as soon wander
over to one scope as the other.
I e-mailed questionnaires to the participants soon after the observing sessions.
Observers are asked to rank the scopes and make comments. A "no ties" rule is
in effect and I ask that the results be e-mailed back to me only (not to the group)
so that we do not influence each others' opinions. After I got the responses
back, I printed them out, grabbed a cup of hot chocolate, and sat on the couch
to digest the information.
Judging from the talk at the sessions, I'd have guessed that the Tak would get
the nod for its mechanics, its star test, and the lust-factor, while the AP won
slightly on contrast. Which would win? This was gonna be close. I just KNEW
this was gonna be close...
The Observers Speak (AP155 vs FCT150):
Herb B: We really needed to devote another night or two or three (how about
a week?) to this process. However, assuming everything was equal (ie, eye-
pieces, diagonals) I would rank the AP first and then the Tak. Verdict: AP155
Chase M: I got the best views through the AP. Money wise, the AP is a
better deal. The Tak would not be an option even if I had the money. Hope I
can make it tonight. Work continues to get in the way! Verdict: AP155
Dan S: AP winner. AP better in contrast. Did not see color in either
scope. The Tak does not provide Bang for the Buck. Verdict: AP155
Dave Sh: I liked the AP best, the Tak a very, very close second.
Verdict: AP155
John P: The FCT150 star tested better. The AP's contrast was better.
The more I look through the AP the more impressed I am by it. For the price
of the Tak OTA you could have the AP155, AP900 mount and have enough left
over for a Starmaster EL! Go figure? Verdict: AP155
Mike T: The Tak had a better star test. But the AP gives better views.
AP makes great stuff. The 155 is hard to beat. Verdict: AP155
Ed T: OK, who's the idiot who came up with the "no ties" rule? Uh...that
would be me. They are so close, but I have to pick one, and I'm taking the AP.
Verdict: AP155
Postscript
Well, well well.....lookee here! Another clean sweep. The AP not only keeps the
crown, it does so unanimously again. I need to stress that the differences between
the scopes are very small, and probably not meaningful in 95%+ of observing uses.
But this is an "ultimate" comparo, and the AP was everyone's favorite. Yet another
tip of the hat goes to the fine folks in Rockford, IL. Well done!
The Winner (Again): The AP155
Takahashi-philes may resume sending me hate mail.
March 30, 2001: It was a dark and stormy night. Although I didn't know
it yet, a foot of heavy snow would soon blanket the yard, and I would lose
power for the rest of the evening due to the storm. I didn't mind; Mother
Nature had blessed this area with blissfully clear and steady seeing for
most of the month, during which time I wound up spending time with some
of the best telescopes on earth.
Now the scopes and the observers had parted, and at least four days of
rain were in the forecast. I appreciated the break in the observing and
am going to use the time to relax a bit. Just as I sat down read a book,
the phone rang. A local club member just got a new telescope, one that
hasn't been reviewed yet in these pages. Would I be interested in coming
over to have a look? Why, now that you asked...
-Ed
End Ultimate Refractor Comparo Part II
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