Takahashi FS102 Fluorite Apochromat - I
[ARTICLEIMGR="1"]I love to compare scopes from one to the other, but here I lack comparable instruments; I don't have resources to own at the same time two (2) 4" apochromatic refractors. I also put as many pictures as I could, because I love to look at telescope pictures (after all, car magazines show more pictures of cars than of roads) and I guess I’m not the only one drooling on equipment pictures.
I bought the scope second hand in France; the scope is about a year old. It is obviously the older model, not the new one with retractable dew shield.
From reading other reviews, it looks like all those 4" APOs from AP, TV, TMB, Tak and Vixen all have outstanding optics and that you would need 1- a very discriminating eye and 2- having the scopes side by side for a test to tell which is best optically. So it seems that one's preference will be made on the fit and finish and the "user friendliness" of the scope; I will try to focus on those little details, which can make an observing session relaxing or maddening. As for myself I did not pick the Takahashi out of preference among the major APO manufacturers; it is just that I had made up my mind on buying a 4" APO and that this opportunity came up.
I thought I would be in love with the scope at first sight. Well, no. The tube does not look like an f/8 refractor, more like an F/6 or F/7: it's quite beefy. The dew shield, 5 1/2" wide, adds to this effect. I made a little chart of scope dimensions to make things clearer than in text (if you can't read it, the ruler is measured in centimeters and the red digits are the 10cm increments)
Unnecessary Rambling on Optical Tube aesthetics
The ancient Greeks had two pillar "types" for the temples and other major buildings: the Doric Style, with a 6-1 proportion between height an girth, and the Corinthian style, which was 8-1. While evolving from the Doric to Corinthian style was the result of improved engineering capabilities, the Greeks thought the Doric had "male" proportions and the Corinthian has "female" proportions and was more elegant. I feel the same about pillars, and the same about telescopes. I cannot call the FS102 "She", only "He".
Once this is said, the tube does not look pretty, but it looks perfect. There is nothing to complain about in the paint or the mechanical assembly. It's the kind of scope, you feel you need to wash your hands before using it. The tube is pure white; other parts are the famous "Takahashi Lime Green". Here's what it looks like, from top to bottom:
Dust Cap:
There used to be a description of Tak dust caps as "man hole covers". Sorry but the myth is cancelled. It is lime-green metal, felt-lined inside, but it's not that stiff: if I press on the center with my thumbs it flexes a little. Which is OK with me as I don't intend to fire bullets at it. So it's perfectly built, but not overbuilt. Right now it fits perfectly on the dew shield , with just the right amount of friction - not too tight and not too loose.
Dew shield:
It's 8" long and 140mm (5" 1/2) in diameter, all metal of course. On this model it does not retract but can be unscrewed for collimation only. You can’t take away the dewshield for transport for instance, as the dust cap would not fit at the top of the OTA, and because the thread is slightly greased.
Tube:
It's well, huh, white, and no, I am not going to hit mine with a hammer to see how solid it is. The inside has a number of knife-edge baffles; 10 according to the brochure but I can’t see all of these. It looks like the baffles are by groups.
Clamshell:
One overbuilt piece of equipment. The retaining screw is locked (useful), and the (ARTICULATION) is double; I don't know what the use of this is, but it works well. The shell is felt-lined in green.
You can fit the clamshell either on a photo-tripod style head, or use the two 10mm holes. I put mine on a Meade LX500 mount, it works fine.
This is a good thing to know when you plan to buy a telescope, as an adaptor can cost you in the area of $100 extra. Scrooges could, in theory, sell the clamshell on astromart, buy a pair of 4 1/2" rings for their mount, and win a few bucks in the process, but it's in theory only, you will never let this clamshell go away, it's so well engineered it looks like a work of love.
Focuser:
The focuser has a lock screw (which I do not use) and a little casing to adjust the stiffness. The focuser has two 40mm alloy wheels. It is extremely smooth, but a little stiff in my mind (the effort you need to make to turn the knob is a little taxing for my flimsy mount). It has 85mm (3 3/8") of travel. I have a complaint about the focuser: it is greased, and every now and then I grab the tube by the protruding part of the focuser drawtube, and invariably end up with that grease on my fingers, however excellent it my be. So what I do now is use permanently both extension rings, so the drawtude does not have to protrude by more than a fraction of an inch.
Finderscope mount:
This part drives me crazy. Attaching the finderscope bracket to the OTA takes two tiny Allen bolts, with tiny-tiny-tiny washers. If you plan on leaving the scope all assembled it's no big deal, but if for storage or travel you need to disassemble the whole thing now and then you will be wishing for another system, or at least for some kind of thumbscrews.
As for attaching the finderscope, same story. It's the classic 6-screw setup: but the top three are nylon tipped thumbscrews (perfect), the bottom three need a screwdriver, and are of the type that does not protrude out of the bracket. Again, if you move often with the scope you will not like this feature. Scopeguard is selling quick release brackets to adapt on these for $69, so I'm obviously not the only one to complain.
Finderscope:
Mine is the 7x50 finder. It weighs 600g (20 oz) with its bracket. It has a decent dewshield (the dewshield on the 6x30 is all of 2mm long), about 2"; it has a well-working (maybe a little too smooth) helical focuser and, notable difference with the Intes finders I know, you can have both the stars AND the crosshairs in focus. The eye relief is a little short in my mind: I like to be able to look through the finder from a couple inches behind. I guess this is the inevitable drawback of having a finder with a wide field (advertised at 6.3°).
The crosshairs have a nice touch: they actually don't cross, the center is "open" meaning that the star you are aiming at is not hidden by the cross. The crosshairs are also very thin: it is not a problem in my garden where the sky is deep brown / maroon at best, but under dark skies you have trouble distinguishing them from the dark sky background. Optically, under the night sky the finder is sharper than any 8x50 finder I have used (especially those Chinese 8x50s which have a curved field with terrible star images on the field edge, the "edge" here being far too close to the center in my opinion) , but it is not perfect: it seems like the stars on the edge of the field are not really in focus when the center of the field is.
You might say that a 2" finder on top of a 4" scope is a little overkill, and I agree, but once you have it, it's hard to part from... I have mixed feelings about this finderscope and its mount. It's perfectly built, but the design is subpar, not very user friendly.
Eyepiece adpator:
As on all tak scopes, there is a plethora of adaptor rings and extenders. Mine has two extenders for 1 1/4" eyepieces, obviously allowing everything from a binoviewer to straight-through viewing (for the not-faint-of-spine), and in my case allows to place my barlow before the diagonal and still have enough back focus. The eyepiece holder is a retaining-ring type which I love: not only does it avoid scratches on the diagonal barrel, it also keeps the diagonal (or eyepiece, or barlow...) straight: in eyepiece holders, the inner diameter is much wider than the outside diameter of the accessory you plug inside, meaning that there is some play and the alignment of the optics is not very good.
Putting it on top of a mount, the scope weighs 3.8 kg. With clamshell, finder, diagonal and all you are more in the department of 5kg (11 lbs). You know if your mount will handle that or not. An EQ3-2 class, or Super-Polaris type mount will handle it but be a little short-handed. On a scope like this, you are "entitled" with steady views, especially if you want to use every ounce of the high powers it is capable of (my short experience with a Sky 90 had been kind of ruined by a very inadequate mount). I use a second-hand LX500 which does just fine.
Click here for more about the Takahashi FS-102II Fluorite Apochromat OTA Only. -Ed.
I bought the scope second hand in France; the scope is about a year old. It is obviously the older model, not the new one with retractable dew shield.
From reading other reviews, it looks like all those 4" APOs from AP, TV, TMB, Tak and Vixen all have outstanding optics and that you would need 1- a very discriminating eye and 2- having the scopes side by side for a test to tell which is best optically. So it seems that one's preference will be made on the fit and finish and the "user friendliness" of the scope; I will try to focus on those little details, which can make an observing session relaxing or maddening. As for myself I did not pick the Takahashi out of preference among the major APO manufacturers; it is just that I had made up my mind on buying a 4" APO and that this opportunity came up.
I thought I would be in love with the scope at first sight. Well, no. The tube does not look like an f/8 refractor, more like an F/6 or F/7: it's quite beefy. The dew shield, 5 1/2" wide, adds to this effect. I made a little chart of scope dimensions to make things clearer than in text (if you can't read it, the ruler is measured in centimeters and the red digits are the 10cm increments)
Unnecessary Rambling on Optical Tube aesthetics
The ancient Greeks had two pillar "types" for the temples and other major buildings: the Doric Style, with a 6-1 proportion between height an girth, and the Corinthian style, which was 8-1. While evolving from the Doric to Corinthian style was the result of improved engineering capabilities, the Greeks thought the Doric had "male" proportions and the Corinthian has "female" proportions and was more elegant. I feel the same about pillars, and the same about telescopes. I cannot call the FS102 "She", only "He".
Once this is said, the tube does not look pretty, but it looks perfect. There is nothing to complain about in the paint or the mechanical assembly. It's the kind of scope, you feel you need to wash your hands before using it. The tube is pure white; other parts are the famous "Takahashi Lime Green". Here's what it looks like, from top to bottom:Dust Cap:
There used to be a description of Tak dust caps as "man hole covers". Sorry but the myth is cancelled. It is lime-green metal, felt-lined inside, but it's not that stiff: if I press on the center with my thumbs it flexes a little. Which is OK with me as I don't intend to fire bullets at it. So it's perfectly built, but not overbuilt. Right now it fits perfectly on the dew shield , with just the right amount of friction - not too tight and not too loose.
Dew shield:
It's 8" long and 140mm (5" 1/2) in diameter, all metal of course. On this model it does not retract but can be unscrewed for collimation only. You can’t take away the dewshield for transport for instance, as the dust cap would not fit at the top of the OTA, and because the thread is slightly greased.
Tube:
It's well, huh, white, and no, I am not going to hit mine with a hammer to see how solid it is. The inside has a number of knife-edge baffles; 10 according to the brochure but I can’t see all of these. It looks like the baffles are by groups.
Clamshell:
One overbuilt piece of equipment. The retaining screw is locked (useful), and the (ARTICULATION) is double; I don't know what the use of this is, but it works well. The shell is felt-lined in green.You can fit the clamshell either on a photo-tripod style head, or use the two 10mm holes. I put mine on a Meade LX500 mount, it works fine.
This is a good thing to know when you plan to buy a telescope, as an adaptor can cost you in the area of $100 extra. Scrooges could, in theory, sell the clamshell on astromart, buy a pair of 4 1/2" rings for their mount, and win a few bucks in the process, but it's in theory only, you will never let this clamshell go away, it's so well engineered it looks like a work of love.
Focuser:
The focuser has a lock screw (which I do not use) and a little casing to adjust the stiffness. The focuser has two 40mm alloy wheels. It is extremely smooth, but a little stiff in my mind (the effort you need to make to turn the knob is a little taxing for my flimsy mount). It has 85mm (3 3/8") of travel. I have a complaint about the focuser: it is greased, and every now and then I grab the tube by the protruding part of the focuser drawtube, and invariably end up with that grease on my fingers, however excellent it my be. So what I do now is use permanently both extension rings, so the drawtude does not have to protrude by more than a fraction of an inch.
Finderscope mount:
This part drives me crazy. Attaching the finderscope bracket to the OTA takes two tiny Allen bolts, with tiny-tiny-tiny washers. If you plan on leaving the scope all assembled it's no big deal, but if for storage or travel you need to disassemble the whole thing now and then you will be wishing for another system, or at least for some kind of thumbscrews.
As for attaching the finderscope, same story. It's the classic 6-screw setup: but the top three are nylon tipped thumbscrews (perfect), the bottom three need a screwdriver, and are of the type that does not protrude out of the bracket. Again, if you move often with the scope you will not like this feature. Scopeguard is selling quick release brackets to adapt on these for $69, so I'm obviously not the only one to complain.
Finderscope:
Mine is the 7x50 finder. It weighs 600g (20 oz) with its bracket. It has a decent dewshield (the dewshield on the 6x30 is all of 2mm long), about 2"; it has a well-working (maybe a little too smooth) helical focuser and, notable difference with the Intes finders I know, you can have both the stars AND the crosshairs in focus. The eye relief is a little short in my mind: I like to be able to look through the finder from a couple inches behind. I guess this is the inevitable drawback of having a finder with a wide field (advertised at 6.3°).
The crosshairs have a nice touch: they actually don't cross, the center is "open" meaning that the star you are aiming at is not hidden by the cross. The crosshairs are also very thin: it is not a problem in my garden where the sky is deep brown / maroon at best, but under dark skies you have trouble distinguishing them from the dark sky background. Optically, under the night sky the finder is sharper than any 8x50 finder I have used (especially those Chinese 8x50s which have a curved field with terrible star images on the field edge, the "edge" here being far too close to the center in my opinion) , but it is not perfect: it seems like the stars on the edge of the field are not really in focus when the center of the field is.You might say that a 2" finder on top of a 4" scope is a little overkill, and I agree, but once you have it, it's hard to part from... I have mixed feelings about this finderscope and its mount. It's perfectly built, but the design is subpar, not very user friendly.
Eyepiece adpator:
As on all tak scopes, there is a plethora of adaptor rings and extenders. Mine has two extenders for 1 1/4" eyepieces, obviously allowing everything from a binoviewer to straight-through viewing (for the not-faint-of-spine), and in my case allows to place my barlow before the diagonal and still have enough back focus. The eyepiece holder is a retaining-ring type which I love: not only does it avoid scratches on the diagonal barrel, it also keeps the diagonal (or eyepiece, or barlow...) straight: in eyepiece holders, the inner diameter is much wider than the outside diameter of the accessory you plug inside, meaning that there is some play and the alignment of the optics is not very good.
Putting it on top of a mount, the scope weighs 3.8 kg. With clamshell, finder, diagonal and all you are more in the department of 5kg (11 lbs). You know if your mount will handle that or not. An EQ3-2 class, or Super-Polaris type mount will handle it but be a little short-handed. On a scope like this, you are "entitled" with steady views, especially if you want to use every ounce of the high powers it is capable of (my short experience with a Sky 90 had been kind of ruined by a very inadequate mount). I use a second-hand LX500 which does just fine.
Click here for more about the Takahashi FS-102II Fluorite Apochromat OTA Only. -Ed.
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