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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