31 replies to this topic

[Scott in NC]

A friend sent me two nice Vixen refractors to test this weekend, a FL102S and 130SS. I haven't had the opportunity to observe with them yet, but got a chance to DPAC test them this morning.

 

I started with the Vixen FL102S. This is a fluorite doublet similar to the Takahashi FC-100 from that era (probably late 1990s) with lenses in the Steinheil configuration (fluorite element in back). It has a focal length of 900 mm (f/8.8), and as such is a little slower than the f/8 FC-100 and FS-102.

 

Here's the FL102S set up on my dining room optical bench.

 

[Scott in NC]

And here are the Ronchigrams from the FL102S:

 

[Scott in NC]

Spherical correction appears to be quite nice in all three colors, nearly identical in red and green, with blue just a little farther off. Chromatic aberration is fairly low for a doublet, and the slow fluorite optics help with this. Color fringing is really only evident on the outermost Ronchi bands, with purple on the edges of the leftmost band and green on the rightmost.  I see a shallow center zone and a thin edge zone.

 

Its been said that these are optically on par with the Takahashi FC-100s and FS-102s of the same era, and I can say that this compares very favorably with the two FS-102s that I've had the opportunity to test. Spherical correction is actually a little better in this scope than in the two FS-102s that I've tested.

 

I do like the mechanics and fit/finish of the Takahashis that I've tested a little better than the Vixens, but optically the Vixens give up nothing to the similarly spec'd Takahashis.

[Scott in NC]

Next, I set the Vixen 130SS up.  This is a faster 130mm f/6.6 ED doublet, and so I expected it to exhibit a little more CA on white light testing.  It appears to be from the same era as the previous scope.

 

[Scott in NC]

When I took my first look, I could immediately tell that something was wrong.  But what?

 

[Scott in NC]

I'm going to stop here and get something to eat.  While I'm gone, I'd like to hear your guesses as to what's wrong with this picture.

[columbidae]

Is the focuser impinging on the light path?

[Souldrop]

Loose flocking?

[Scott in NC]

Is the focuser impinging on the light path?

Something is impinging in the light path. Now I had to figure out what.  It's got a flat edge, so I didn't think it was the focuser, and my first thought was that maybe it was the edge of my optical flat holder. I took a look at the objective end of the scope and the optical flat, and that wasn't it, as everything seemed to be in perfect alignment. So now I knew I needed to take a look inside the OTA.

[Scott in NC]

Loose flocking?

As I mentioned in my last post, I ruled out a light path obstruction external to the OTA, so now needed to take a look inside. And it wasn't flocking, as this scope had none, but you're very close.

[Scott in NC]

Now I was wondering if maybe something was wrong with one of the baffles, but I couldn't understand how that would generate an obstruction with a flat edge, unless maybe a baffle was lying on its side.

 

Here's what I saw when I looked through the objective into the scope.

 

[Scott in NC]

Time to perform a little surgery. I unthreaded the dew shield and lens cell, tipped the scope front end down, and out fell these two pieces of foam. Now how in the world did those get there??? 

 

[Alan S]

Scott,

 

This happened to me! I had just plucked some new foam in an eyepiece case, one of the pieces apparently stuck to a 1.25” adapter I was using and the next time I used the scope I discovered it

[Scott in NC]

I called my friend (the scope's owner) to discuss my puzzling findings, and he recalled that he had never observed through the scope, but when it arrived from Italy he noted that the open tube had been packaged separately from the lens cell. So apparently some foam from the packaging had made its way into the tube, and when he threaded the lens cell on to the tube that had trapped the foam inside. He had never observed through the scope, so had never noticed this.  Mystery solved!!!

[Scott in NC]

Whew! Now after that amusing little detour I was able to get back to the testing procedure. And finally, some Ronchigrams:

 

 

 

[Scott in NC]

This scope appears to be under corrected in red and green, and over corrected in blue. It's hard to say for sure, but spherical aberration might actually be lowest in blue. The white light images show significantly more chromatic aberration than were seen with the first Vixen, but that was a slower f/8.8 fluorite doublet with less aperture, and this scope is a faster f/6.6 ED doublet with greater aperture, so that's to be expected.  The edges appear to be better corrected on this scope than with the previous scope, but there is a more pronounced central zone.

 

Overall, not a bad scope. Not perfect, but not bad either.  The first of the two scopes I tested today is clearly superior optically, but as has been said before, it's much harder to make a large fast refractor than a smaller slow refractor.

 

Now I'm eager to test both of these scopes out under the stars! More later...

[Kitfox]

Personal attack warning! Mods beware…

 

What kind of fool would reassemble a scope with not one, but two chunks of foam inside?  Geez…

 

I sure hope no one ever finds out who did that…he/she would be sooooo embarrassed.  Scott, please don’t reveal the identity of this poor soul. 

 

Scott did tell me offline that the individual who owns this scope has two examples of the 130ss, and this one had never been used.  Although I suspect anyone this lacking in attention would have never known the difference. 

[Scott in NC]

I guess it could happen to the best of us.

[Dave Novoselsky]

Spherical correction appears to be quite nice in all three colors, nearly identical in red and green, with blue just a little farther off. Chromatic aberration is fairly low for a doubt, and the slow fluorite optics help with this. Color fringing is really only evident on the outermost Ronchi bands, with purple on the edges of the leftmost band and green on the rightmost.  I see a shallow center zone and a thin edge zone.

 

Its been said that these are optically on par with the Takahashi FC-100s and FS-102s of the same era, and I can say that this compares very favorably with the two FS-102s that I've had the opportunity to test. Spherical correction is actually a little better in this scope than in the two FS-102s that I've tested.

 

I do like the mechanics and fit/finish of the Takahashis that I've tested a little better than the Vixens, but optically the Vixens give up nothing to the similarly spec'd Takahashis.

Interesting since earlier today there was some discussion about how the optics of the Vixen fluorite refractors, including the FL102S compared to the contemporary Takahashi. I have the last and slightly ‘slower’ version of the FL102S, the f9 vs the earlier f8.8, as well as a very crisp FS102. I too find they perform as virtual clones although the tone in the Vixen is, as others have also noted, a hair deeper.  Hold a gun to my head and I’d definitely pick the Vixen.  And I find that the lighter build of the Vixen is simply that, while the fit and finish, the traditional glossy white and green/gray mechanical finish gives up nothing to the Takahashi.  They both unfortunately should be ashamed of their focusers which do not exhibit the same quality as the rest of the scope —something that continues with the current models.

 

I also have a Vixen ED 130SS which I have been wringing out we my better sighted friend pretty extensively.  While not put through your test, our older method of visual testing (star test, splitting doubles, bright lunar, Mark 1b eyeball has found this scope to be extremely well corrected etc and deserving of the stellar reviews it has previously recede several pretty meticulous reviewers.  Wonder if the one you tested was a Monday morning or late Friday afternoon example?

Edited by Dave Novoselsky, 13 July 2024 - 11:48 PM.

[Scott in NC]

I also have a Vixen ED 130SS which I have been wringing out we my better sighted friend pretty extensively.  While not put through your test, our older method of visual testing (star test, splitting doubles, bright lunar, Mark 1b eyeball has found this scope to be extremely well corrected etc and deserving of the stellar reviews it has previously recede several pretty meticulous reviewers.  Wonder if the one you tested was a Monday morning or late Friday afternoon example?

That’s hard to say. As was mentioned above, I believe my friend has two samples of this scope, and I’m eager to test out his second sample for comparison some day. But regarding this current sample’s DPAC results, it’s definitely not perfect, but it’s not exactly horrible either. Scopes with DPAC results like this can still put up pretty nice views. It might take high magnification planetary viewing or tight double star splitting in order to see much of a difference between this one and one with more perfect optics. But this is just an educated guess based upon my experience testing and viewing through many other scopes, as I’ve still not had a chance to visually observe through this particular one.

[Dave Novoselsky]

That’s hard to say. As was mentioned above, I believe my friend has two samples of this scope, and I’m eager to test out his second sample for comparison some day. But regarding this current sample’s DPAC results, it’s definitely not perfect, but it’s not exactly horrible either. Scopes with DPAC results like this can still put up pretty nice views. It might take high magnification planetary viewing or tight double star splitting in order to see much of a difference between this one and one with more perfect optics. But this is just an educated guess based upon my experience testing and viewing through many other scopes, as I’ve still not had a chance to visually observe through this particular one.

I think we are on the same page. Your comment that it “might take high magnification planetary viewing or tight double star splitting in order to see much of a difference between this one and one with more perfect optics” is how my friend and I generally evaluate a scope’s optics and our opinions are formed on that basis, although the opportunity to do planetary lately has been limited by availability.  Still, if you get the chance to try that second example I would appreciate hearing your evaluation.

Edited by Dave Novoselsky, 14 July 2024 - 12:12 AM.

[stevew]

I've never looked through a Japanese Vixen refractor I didn't like.

Nice job, thanks for posting.

[Highburymark]

More interesting DPAC tests to add to the list - thanks. I’m hoping we’ll see Vixen’s current EDs tested at some stage.

[CHASLX200]

Looks good to me. Never a bad V out of 30 or so i have had.

[Kitfox]

At the risk of outing the individual who owns these scopes, I know he ran the FL102 up against a 1986 FC100.  “He” said the Vixen gave a slightly better star test, but they were indistinguishable from one another on the lunar terminator. “His” comments that the scopes had nearly identical “color temperature” appearance on bright objects didn’t surprise me; similar designs and optic sources. 
 

“He” is excited to try the two 130s side by side after Scott tests the second example. This may end up being a BT. 
 

And he was quite adamant in his overwhelming love for Vixen and Tak fit, finish and single speed focusers!