Astro-Physics 155 F/7 Starfire EDFS APO Refractor vs. Takahashi FS 152 F/8 APO Refractor

https://www.cloudynights.com/articles/cat/user-reviews/telescopes/140mm-refractors/astro-physics-155-f7-starfire-edfs-apo-refractor-vs-takahashi-fs-152-f8-apo-refractor-r866

The Current 'Big Guns':

This is a review and comparison of two of the larger and better currently available "APO" refractors. There are others that can be ordered, such as the Meade 6 and 7" APOs, but they have not fared well when viewed by others and do not command the respect of these two telescopes. The TMB refractors are coming on line, but only a handful of the 6" and larger TMB scopes are in this country, and none are currently available for testing. That leaves these two 6" APOs as the 'top of the heap' in refractors one is apt to encounter for sale, or to view at a star party. They are, in addition, both remarkably alike yet quite distinct at the same time.

Physical Description:

The Takahashi FS 152 is an air-spaced doublet, with the outer element composed of Fluorite and a focal length of f/8. The OTA is supposedly 54.75", but measured closer to 58" from the end of its rigidly mounted dew cap to the compression ring at the end of the focuser when I checked before I purchased a custom case. All of the 152s come with a rotating, 4" focuser. The OTA weighs 24 pounds.

The files with the photos of the 152 became corrupted, so I can't post a photo as part of this review. Picture an FS 102 or a 128 in your mind and then fatten and lengthen the tube. The tube is gloss white and the focuser, tube rings (a massive and expensive double ring and bridge assembly) and other mechanical parts are anodized in the traditional Takahahsi lime green.

The Astro-Physics 155 is an oil-spaced triplet, using super ED glass and a focal length of f/7. The OTA measures 41" with the dew cap stored in its retracted and reversed position. The OTA weighs 23 pounds in the EDFS version with the 2.7" focuser. (The EDF version uses a 4" focuser and comes standard with a field flattener. That version weighs 27 pounds.) The mechanical parts are black anodized, as can be seen in the attached pictures.

The difference in length is not as great as the statistics would indicate. The extra length of the Takahashi is caused in part by its fixed, non-removable and non-retractable dew cap. Once extended, the only real difference in length between these two 6" APOs is found in the slightly shorter, 'faster' focal length of the AP.

'Hefting' both scopes with the dew caps extended, there is little to chose from in feel. The slightly longer Tak feeling more nose-heavy even with the doublet objective versus the triplet lens assembly at the front of the AP. The Tak seemed a tad more awkward to maneuver than the AP, noticeable in mounting and dismounting the scope.

Fit and finish on both scopes was hard to fault. The AP I own is one of the older models with the smooth, glossy white finish. Compared to my 130 f/6 with the 'new' pebble-grain white finish, I prefer the older, smooth style. While both scopes look great, I would give the Tak the edge in ultimate finish, paint and mechanical, but with the AP nipping at its heels.

The Tak end cap is a piece of relatively heavy, cast (?) aluminum, with a removable disk at the center to let you 'stop down' the scope if you wish. The AP uses a plain, black- anodized end cap. While the Tak is wonderful to look at, it is overkill, and justs adds to the nose heavy feel of the scope. Point to AP for substance over style on this one. (Again, personal preference issue.)

The AP comes in a vinyl-covered, wooden case. A focal extender and 1.25" adapter comes with it. The Tak, a lot more money to start with, requires you to buy the case extra.

Use - Mechanical and other Non-optic Issues:

The Tak focuser is the clear winner here. Even though the AP is smooth, and I prefer the 2.7" for non-photographic use, the Takahashi 2.7" as I used on my 102 and 128 was simply more precise in feel than the excellent AP 2.7. The Tak 4" and the 4" AP (which I tried on a friend's EDF) are both noticeably more 'stickly' and take more effort to use, with the Tak coming on top here by a still-slim, but slightly more distinct margin.

The Tak uses the more traditional compression rings on the standard extension tubes. The AP offers its brass, internal compression rings on the standard 2"/1.25" adapters. Point for the AP. (I used an AP Maxbright 2" diagonal on both scopes, so the everyday use was a tie.)

The AP mounts with the traditional 'clamshell' rings, quite easy to use in an EQ mount or in the Gr-2 (Standard) as shown in the picture. Getting the OTA in and out is simplicity itself. Rings are fairly inexpensive.

The Tak uses an elaborate double ring, 'bridge' setup that is nearly $700 (!) and quite heavy. Getting the tube in and out, particularly at night, is a comparative nightmare , since the rings need to be carefully opened, the tube lifted out, and the entire assembly unnecessarily complex. Another point for the AP.

I owned the Takahashi first, trading the FS 128 and an EM 200 mount for the larger 152 and an NJP mount (having been told that the EM 200 was marginal for the longer and heavier Tak 6".) The NJP is a superb mount, and for photography with the 152, a clear 'win' for the Tak. However, I am purely a 'visual' guy and, courtesy of Uncle Sugar and the good ole US Army circa 1969, my back is not up to hefting anything too heavy. The NJP and the 152 was a beast to move and setup. The 152 tended to be used quite little since I was not usually in the mood to 'rassle' 50 or 60 pounds of mount, tripod, and then 24 pounds of scope out for a night of observing. Given my touchy back, I wanted an easier 6" to set up and use.

I acquired the 155 for some smaller scopes a friend wanted and cash. The idea was to get a 6" scope that I could use on an EQ mount if necessary (I have a G-11 and a Mi-250) or on an Alt-Az if I could find one that would hold a 6" and work reasonably well for visual.

That chance came a week after I got the 155. Shown below is the AP 155 set up on the APM Gr-2 (Standard) mount as reviewed elsewhere on this site. The mounting plate was purchased from Anacrotes, who sells it as a plate to use with their WYO refractors. I bought several, and have them set up with tube rings for my TMB 100 f/8, the AP 130 f/6, the TV 140, and the AP 155. As you can see from the photo, the plate attaches to the mounting head and goes on and off with two 7mm Allen bolts. Switching or mounting a scope is a two-minute job. Bolt in the appropriate plate and rings, open the rings, put in the OTA, and away you go.

The standard version of the GR-2 mount is rated at 25 pounds. The 155 worked fine, although it was clearly at the limit of what the standard version of this mount would hold. (I noted more vibration and a general 'touchy' feeling with the 155 that was absent when the lighter AP 130 and the TV 140 was used on this mount. It worked fine, but needed a second to settle down with a load at the ep end. It did settle down very quickly, however. The Deluxe version that is on its way to me should handle the 155 much better and will, according to what I have been told, be less sensitive to vibration as it is rated at 50 to 60 pounds rather than half that weight for the standard version.)

So the 155 would be a better scope for me to own for purely personal reasons. Now, what about the real test - optics?

Outside and Test:

(I acquired my 152 over the Winter, and had the chance to test it on the Gas Giants. The 155 arrived after they were long gone, so this commentary will restrict itself to deep sky and lunar.)

The Takahashi doublets have been treated with disdain by some as having 'too much color', lacking in the ultimate optical ability of the AP triplets, and otherwise simply not 'in the same league' as the Astro-Physics products. Starting out here, rather than at the end, I can say that whether the 152 I owned was an exception, and others are 'worse', I found the Tak to be an outstanding performer. I say that after having spent enough time using the AP 155 to compare these two scopes. As the 155 AP I now own was previously in the hands of a more experienced observer (who said it was a great example of the 6" AP) and as this same scope had been tested by a well-known optical designer at AstroFest a few years ago, and given his 'seal of approval', I know I don't own a 'dog.' So, assuming my Tak was typical of the 'breed', lets have a dog show.

The Tak does indeed cool down faster. Ed Ting's observations are correct. The AP has a fair amount of glass up there, and the oil-spaced objective needs a lot of time to come to equilibrium. Star testing the AP when the Tak was cooled down showed tube currents waffling through the image. Once both are 'ready', it is tough to pick one over the other.

Deep sky is also a toss-up. Both split doubles with contemptuous ease. Double Double and the Ring Nebula show almost the same through the same eps. Both scopes reach 'deep.' In comparison to a 5" scope (using the FS 128 I owned before and the 130 AP I own now as a benchmark) there is a better image scale and 'reach' that is very real and very noticeable. While neither scope can match a good Dob (my 11 EL Starmaster kicks both of these scopes in the chops on deep sky) deep sky, clusters, and doubles are sensational compared to smaller aperture refractors.

* * *
[A quick digression on aperture in refractors:]

Let me stop here to address the common rubric that while the step up from a 4" to a 5" refractor is quite noticeable, the step up from a 5" to a 6" is not the same magnitude. I agree as to the former, having experienced it myself when getting the FS 102 alongside the FS 128. However, and I am sorry to disappoint you when I say this, but while the difference in cost moving from a 5" to a 6" is a big step, so is the improvement in image scale and 'reach.' I have had the two AP scopes side by side, and the 155 is visually FAR more impressive than its smaller 5" brother. (The issue becomes muddied when the TV 140 comes into the mix. Yes, it has more 'oomph' than the 130, as I noted in my review. Does the 155 'walk on it?' No. There is a difference, but not as great as between the 130 and the 140 in a 'side by side.' Too tough to call.) Of course, as the price difference between the Tak 128 and the Tak 152 is nearly double, if not more, then the scorecard may indeed shift the decision back to the 5". The AP 5" and 6" are much closer in price, so the equation shifts the other way in that test, IMHO.
* * *

Lunar? AP wins. 'Sharpness' and contrast are a tossup. Both give stunning views and soak up stupid amounts of magnification. (Both would hold a 5mm Takahashi and a 2.5 Powermate on Plato. If I did my numbers right that is 695X for the Tak (1390 divided by 5 times 2.5) and 542 for the AP (1085 divided by 5 times 2.5 And that was condition limited, not optically limited.) Both scopes took magnification well. Contrast on both scopes was outstanding.

Why then does the AP 'win'? On really bright nights, the AP shows no color at or off the edge of the lunar disk. Stars just beyond and behind the Moon stand out with no 'bleed over.' The Tak did show just a trace at the edge.

Optically, the only real difference is that the Tak is a hair easier to snap into focus. Perhaps it is a characteristic of an oil-spaced versus an air-spaced system, but I noticed the same thing testing the TV 140 setup next to the AP 130 f/6. Neither AP is difficult to bring to focus, but the ari-spaced Takahashis and the TVs seem to snap in more 'crisply'. It is a bit easier to go past focus and then have to come back in the AP than the Tak. (I noticed the same testing my air-spaced triplet TMB 100 f/8, so I assume this is in fact simply something inherent in an air-spaced versus an oil-spaced design.) Having said that, however, it is indeed a completely minor point, and not a problem in 'real world' observing. Just a nit to pick, not a problem at all.

Conclusion:

Two great scopes. Everything you have heard about the 155 AP is true. However, forget all of the nonsense you heard about the 'big' Takahashi, it is bull. Both are comparable performers. I traded my 152 as part of the deal that brought the TV 140 to me. My decision to trade it, and acquire the AP in its place, was personal and not related to 'better' or 'worse' at all.

If you have read any of my other reviews, you know that I am fixated on mounting the largest possible refractor on an AltAz mount. The AP 155 EDFS is just a scoosh (yes Brian, it is a 'David' word, not to be found in the dictionary) smaller and lighter than the Tak - albeit attributable almost entirely to the nature of the dew cap and because of the smaller focuser. When a chance to get the TV 140 came up, and the other guy wanted the FS 152, I traded what could be replaced if I wanted to for something a whole lot harder to acquire. And, once the 155 was 'up and running' in the Gr-2 (and with the Gr-2 Deluxe on its way in) the 152 is simply a fond memory. But it is indeed a fond memory, and a scope you should consider if the opportunity arises.

The AP 155? Great scope. I am a novice in comparison to Todd Gross and Ed Ting. I echo everything they say about this remarkable 6" refractor. Also a scope you should consider if the opportunity arises.

It has been a privilege to own two of the best. I would be pleased to own either one again if the situation arose, and would urge the same if any of you find yourself in the market for a superb refractor.

As always, thank you for listening to my ruminations.