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Disappointed with Vixen A105MII. Alternatives?

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#26 db2005

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Posted 21 May 2020 - 01:12 AM

Re the suggestion that the OP gets a good ED scope instead:

 

The closest contender is probably the SW ED100 f/9 which I also happen to own. IMO the mechanical quality and finish of my Vixen scopes is somewhat better. Yes, the ED100 has a crayford-like focuser but I find the R&P focuser on the Vixen is more enjoyable to use and less fiddly to adjust. Paint-job on the Vixen is somewhat better too. As for optical quality, the ED100 has noticeably less false color (although it still has some), but optical quality is not in entirely the same league as high-end optics: Expect some SA and less clearly defined splits of tight doubles. Also I find the contrast is not entirely on par with high-end optics. I found the same to be true with my 80ED: very modest CA, some SA and decent optics that were still noticeably outperformed by my SD81S. Now, don't get me wrong: the ED100 is very nice for what you pay, just don't expect world-class optical quality for a fraction of the cost.

 

IMO you are doing well to go for optical quality and you are right to expect excellent optics when paying a price-premium for Japan-made optics by Vixen. And in my own experience you are not likely to get optical quality on par with that if buying an entry-level ED scope instead. I've owned a handful of Chinese-made scopes over the years (all bought from new), and not one of them has performed at the same high level as my Vixen/Tak scopes.

 

If I were In your shoes I would hold off making a decision to abandon the A105M for a bit longer. It seems more sensible to first verify that there indeed is a problem with the scope's optics (and be sure to eliminate all other factors, like diagonal, thermal issues, seeing, problems with your own eye-sight, etc). You may also consider to do an in-doors artificial star test, looking for the ragged/non-circular diffraction discs reported in the OP. And if there indeed is an optical problem, make sure to give your dealer a chance to set things right.


Edited by db2005, 21 May 2020 - 08:50 AM.

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#27 Littlegreenman

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Posted 21 May 2020 - 01:54 AM

gamma_ari posted:

 

"The screws for tightening the tube clamps are made out of cheap plastic with a bad look and feel. In a 850 Euro scope I would have expected metal screws or at least plastic with a better finish."

 

Note that metal bolts with a plastic knob on top, is an off-the shelf part with many variations made by a variety of manufactures around the world. It is also possible that Vixen ordered a version made to their specs. I have some metal bolts with a plastic knob on top and the knob looks the same as the one in your picture.

 

The knobs, of course, allow for tightening things by hand without having to use a tool. Which is why people use them. They are not unique to astronomy, where they have been used since at least the 1970's.

 

It is possible but unlikely the bolt under the plastic know is also plastic. It's also possible that a cheaper plastic knob came with your telescope that looks and feels cheap. Bolts with metal knobs are also available off-the shelf, and of course could be made to order. Those are uncommon in the level of astronomy equipment.


Edited by Littlegreenman, 21 May 2020 - 10:35 AM.

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#28 gamma_ari

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Posted 21 May 2020 - 05:21 AM

Thanks to everyone for your replies, you guys are great! Last night I repeated the star test straight through. The test was performed after 1 hour of cool down. Diffraction rings were deformed. This time they looked slightly triangular. The triangle didn't seem to change orientation by 90 degrees when I compared inside and outside focus. Could this be a case of pinched optics?

 

In terms of the scope's mechanics, maybe my expectations were too high. I'm spoiled by my Vixen A62SS, every single part of which looks and feels fantastic. Ironically the little achromat is manufactured by Long Perng grin.gif I'm also spoiled by my all-metal TS ED 102 f/7, which is far superior to the A105M in terms of mechanics.

 

As for optical quality, the ED100 has noticeably less false color (although it still has some), but optical quality is not in entirely the same league as high-end optics: Expect some SA and less clearly defined splits of tight doubles. Also I find the contrast is not entirely on par with high-end optics.

That's one reason why I chose the A105M over the ED100. I was looking for premium optics. I already have a TS ED 102 f/7. While I'm happy with its optics, I feel double stars could be split even cleaner. Maybe I should have a close look at Takahashi's offerings. You have an FC-76Q and an SD81S, could you write a few words on how they compare in terms of optics and mechanics?

 

Thanks you,

Viktor


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#29 25585

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Posted 21 May 2020 - 05:39 AM

Found thus thread yoy might like https://www.cloudyni...ixen-sd-103-ed/


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#30 Hesiod

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Posted 21 May 2020 - 07:20 AM

If the telescope has a bad star test, then should return it.
As for the focuser, I think that "Crayford" units are often overlooked and sometimes are just awful.
Good R/P such as those installed by Takahashi are very effective, to the point that never felt the urge for the dual speed upgrade or for a third part replacement.
Apparently at Vixen can do great jobs, at least when they want, and I learned this by purchasing the FL55ss which is as good as my Tak except that has a better R/P focuser and a far superior photographic kit which, in my humble opinion, Tak should "clone" for their smaller refractors...
Vixen seem however really prone to missteps, such as with the hideous RDF

#31 db2005

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Posted 21 May 2020 - 07:34 AM

You have an FC-76Q and an SD81S, could you write a few words on how they compare in terms of optics and mechanics?

 

Comparing the FC76DCU and Vixen SD81S I found the two scopes to be optically much more similar than different. With the Q extender module the FC76DCU becomes a different scope with flat field and out-of-this-world color correction.

 

Optical differences:

  • The SD81S is 81 mm vs 76 mm aperture for the Tak.
  • The SD81S has a slight (the instrumental word being slight) amount of CA (a pale yellow/cream tinge when focusing on Vega). The Tak renders Vega as a more pure white.
  • Contrast, resolution, optical quality is almost a toss-up, possibly with a slight nod to the Tak. With the Q module added, the Tak's color correction is visibly better (IMO, if one is paying for the FC76DCU getting the extender module as well is practically a no-brainer because it improves the performance so much). But in terms of splitting challenge double stars (one of my favorite pastimes under my skies) both scope seems to show me the same things, and noticeably better than my ED100.

 

Mechanical differences:

  • The Vixen is somewhat heavier than the Tak in terms of build and wall thickness. Overall the Vixen feels like the most sturdy scope, stronger paint, and the Tak feels like the most refined scope of the two.
  • The Vixen has a 2" focuser and plenty of focus travel. The Tak is natively 1.25" but can be changed (with optional adapter) to 2". Very limited focus travel on the Tak means changing between 1.25" and 2" accessories has left me scratching my head looking for a good solution.
  • Vixen's focuser is quite strong, the Tak's is quite petite and the dratube rotates a bit when focusing. Just a minor niggle, but still.
  • Focuser knobs on the Vixen are nice, black-anodised metal. Focuser knobs are made of plastic on the Tak. I have chosen not to regard this as a cost-cutting move, but as a means of saving weight. The DCU has been marketed as a airline-portable scope, so weight does matter.
  • Paint-job is excellent on both scopes, with a nod to the Tak.
  • Mounting a finderscope on the tak either requires Tak's (again: optional, and pricey) quick release bracket or using tools to remove the finder scope.
  • The Tak's finder scope (again: optional) is the best finder scope I've looked through. Bright, generous eye relief, contrasty, unbelieveably sharp. The Vixen comes with a plastic RDF on a standard Vixen finder scope base. The Vixen has one clear advantage though: The visual back allows mounting another finder scope with an optional finder scope shoe. I use mine with an RDF and a 50 mm RACI finder. Perfect. Mounting two finders on the Tak isn't as straight-forward.
  • The dust cap is thin metal on the Tak, plastic on the Vixen.

To the best if my knowledge, the SD103S is every bit as good as the SD81S, both in terms of build quality and optical performance. The FC76DCU is currently my most used scope but my SD81S isn't going anywhere. Both are great scopes with each their own "personality".


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#32 GOLGO13

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Posted 21 May 2020 - 07:41 AM

Sounds like pinched optics. I wonder if this scope was already returned before. It sounds so weird and unlike Vixen.

Maybe try a new dealer also. But for sure return it.

#33 SeattleScott

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Posted 21 May 2020 - 08:08 AM

Pinched optics would be highly unusual for a Vixen refractor given the lenses are cemented in place. There are no collimation adjustments so there is nothing to pinch unless the scope has suffered some sort of trauma.

What magnification were you using for the star test? At low power it could be astigmatism from your own eye. I always use at least 100x.

And there is still the question of the diagonal. Obviously you have other scopes with other diagonals. Use one of your other diagonals and use at least 100x magnification for the star test after at least a half hour of cooling. If you are still seeing the odd star test, then I would say there is something wrong. It is conceivable that the missing spot of paint near the lens cell is the result of a mishap at the factory or during shipping.

So it sounds like you want premium optics rather than mass produced, hence you got the A105M even though you have the TS Apo. There aren’t really any other premium achros on the market, so you can see if you can sort out the optical issue (swap diagonal or whatever), return it for a replacement if the optics really are bad, or get a premium brand Apo. The premium Apo will obviously be more expensive, with Vixen being generally the cheapest (beginning of the high end) at $2k or so for the SD103S.

As for the build quality of your 62mm achro being better, consider that it doesn’t cost much less than the A105M.

Scott
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#34 gamma_ari

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Posted 21 May 2020 - 08:17 AM

Comparing the FC76DCU and Vixen SD81S I found the two scopes to be optically much more similar than different. With the Q extender module the FC76DCU becomes a different scope with flat field and out-of-this-world color correction.

 

Optical differences:

  • The SD81S is 81 mm vs 76 mm aperture for the Tak.
  • The SD81S has a slight (the instrumental word being slight) amount of CA (a pale yellow/cream tinge when focusing on Vega). The Tak renders Vega as a more pure white.
  • Contrast, resolution, optical quality is almost a toss-up, possibly with a slight nod to the Tak. With the Q module added, the Tak's color correction is visibly better (IMO, if one is paying for the FC76DCU getting the extender module as well is practically a no-brainer because it improves the performance so much). But in terms of splitting challenge double stars (one of my favorite pastimes under my skies) both scope seems to show me the same things, and noticeably better than my ED100.

 

Mechanical differences:

  • The Vixen is somewhat heavier than the Tak in terms of build and wall thickness. Overall the Vixen feels like the most sturdy scope, stronger paint, and the Tak feels like the most refined scope of the two.
  • The Vixen has a 2" focuser and plenty of focus travel. The Tak is natively 1.25" but can be changed (with optional adapter) to 2". Very limited focus travel on the Tak means changing between 1.25" and 2" accessories has left me scratching my head looking for a good solution.
  • Vixen's focuser is quite strong, the Tak's is quite petite and the dratube rotates a bit when focusing. Just a minor niggle, but still.
  • Focuser knobs on the Vixen are nice, black-anodised metal. Focuser knobs are made of plastic on the Tak. I have chosen not to regard this as a cost-cutting move, but as a means of saving weight. The DCU has been marketed as a airline-portable scope, so weight does matter.
  • Paint-job is excellent on both scopes, with a nod to the Tak.
  • Mounting a finderscope on the tak either requires Tak's (again: optional, and pricey) quick release bracket or using tools to remove the finder scope.
  • The Tak's finder scope (again: optional) is the best finder scope I've looked through. Bright, generous eye relief, contrasty, unbelieveably sharp. The Vixen comes with a plastic RDF on a standard Vixen finder scope base. The Vixen has one clear advantage though: The visual back allows mounting another finder scope with an optional finder scope shoe. I use mine with an RDF and a 50 mm RACI finder. Perfect. Mounting two finders on the Tak isn't as straight-forward.
  • The dust cap is thin metal on the Tak, plastic on the Vixen.

To the best if my knowledge, the SD103S is every bit as good as the SD81S, both in terms of build quality and optical performance. The FC76DCU is currently my most used scope but my SD81S isn't going anywhere. Both are great scopes with each their own "personality".

Excellent write-up, thank you! Seems both are great scopes for the price.


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#35 gamma_ari

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Posted 21 May 2020 - 08:24 AM

Pinched optics would be highly unusual for a Vixen refractor given the lenses are cemented in place. There are no collimation adjustments so there is nothing to pinch unless the scope has suffered some sort of trauma.

What magnification were you using for the star test? At low power it could be astigmatism from your own eye. I always use at least 100x.

And there is still the question of the diagonal. Obviously you have other scopes with other diagonals. Use one of your other diagonals and use at least 100x magnification for the star test after at least a half hour of cooling. If you are still seeing the odd star test, then I would say there is something wrong. It is conceivable that the missing spot of paint near the lens cell is the result of a mishap at the factory or during shipping.

So it sounds like you want premium optics rather than mass produced, hence you got the A105M even though you have the TS Apo. There aren’t really any other premium achros on the market, so you can see if you can sort out the optical issue (swap diagonal or whatever), return it for a replacement if the optics really are bad, or get a premium brand Apo. The premium Apo will obviously be more expensive, with Vixen being generally the cheapest (beginning of the high end) at $2k or so for the SD103S.

As for the build quality of your 62mm achro being better, consider that it doesn’t cost much less than the A105M.

Scott

I did the test at 125x. This is definitely a faulty unit. You're right, this may well be connected with the peeled off paint near the lens cell. I'm sending the scope back. 

 

I noticed that you have an A105M alongside an ED103. Does it offer you anything that the ED103 doesn't? Just being curious.



#36 GOLGO13

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Posted 21 May 2020 - 08:53 AM

If you can find a 103s used it's a great scope.

 

I've had two of them and my current one is crazy good. The previous one was also really good. 

 

But not sure how much they come up used in Germany.

 

I got mine used for $750. I swapped the focuser for a Moonlite (it was on my 81s before that). It's a really good scope:

 

103s

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#37 dmgriff

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Posted 21 May 2020 - 11:05 AM

Sorry to hear the OP is so dissatisfied with the Vixen A105M II.

 

I compared my Vixen A105M with my SW ED100 on the moon. The eps were Tak Abbe orthos and Brandons.

 

End result, I prefer the A105M to the ED100. Nicer core image with the A105M imo. The chromatic aberration on the Vixen is very slight to my old eyes.

 

I did not expect to keep the flip mirror or the rdf. Bought a Vixen (Japan) 2in star diagonal at the time of purchase, and had 9x50 and 6x30 racis already.

 

If the focuser tension plastic screw annoys the OP, suggest they buy a comparable metal screw with a plastic tip (will not mar the drawtube).

 

Good viewing,

 

Dave



#38 SeattleScott

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Posted 21 May 2020 - 11:41 AM

I did the test at 125x. This is definitely a faulty unit. You're right, this may well be connected with the peeled off paint near the lens cell. I'm sending the scope back.

I noticed that you have an A105M alongside an ED103. Does it offer you anything that the ED103 doesn't? Just being curious.

The problem with the ED103S is it grew a camera. Since I like to keep the camera and WiFi adapter semi-permanently attached with wires zip tied down and such, it became a hassle trying to use it for visual GNG. So I got the A105M for GNG. I didn’t feel like I could justify the cost of two Vixen Apos to the wife.

Scott

#39 SeattleScott

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Posted 21 May 2020 - 12:19 PM

Sorry to hear the OP is so dissatisfied with the Vixen A105M II.

I compared my Vixen A105M with my SW ED100 on the moon. The eps were Tak Abbe orthos and Brandons.

End result, I prefer the A105M to the ED100. Nicer core image with the A105M imo. The chromatic aberration on the Vixen is very slight to my old eyes.

I did not expect to keep the flip mirror or the rdf. Bought a Vixen (Japan) 2in star diagonal at the time of purchase, and had 9x50 and 6x30 racis already.

If the focuser tension plastic screw annoys the OP, suggest they buy a comparable metal screw with a plastic tip (will not mar the drawtube).

Good viewing,

Dave

This was kind of my thinking too. After relegating the Vixen Apo to EAA, I needed a new 4” refractor for GNG. I had a 100ED before and it was fine, but the Vixen kind of spoiled me, and I wanted that optical precision but didn’t feel like I could justify the cost of a second Vixen Apo. So I got the achro instead and am happy with my choice. The CA is surprisingly low compared to other achros I have used, as long as the Moon isn’t too full. If the Moon is mostly full, then maybe I get the Apo out or the Mak. Or maybe I just don’t go out if the Moon is nearly full. Depends a lot on how recently I have gone out.

It sounds like the OP just got a faulty unit, maybe the lens cell got dropped at the factory, and initially the OP had a bit unrealistic expectations regarding the build quality but is more on board now.

Scott

#40 Jon Isaacs

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Posted 22 May 2020 - 12:45 PM

The top Apos on the market come with R&P focuser. I had a 100ED with crayford focuser. I much prefer the R&P on the Vixen scopes.

 

 

Truthfully, the top of the line rack and pinion Focusers are completely different in design. The Vixen Focuser bears a strong resemblance to the Synta rack and pinion Focusers.

 

https://www.highpoin...rake-ftf3025b-a

 

I would try a diagonal of known quality.

 

Jon

 

Jon



#41 daquad

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Posted 22 May 2020 - 01:47 PM

Truthfully, the top of the line rack and pinion Focusers are completely different in design. The Vixen Focuser bears a strong resemblance to the Synta rack and pinion Focusers.

 

https://www.highpoin...rake-ftf3025b-a

 

I would try a diagonal of known quality.

 

Jon

 

Jon

He did the star test straight through and found the pattern to be triangular (post #28).  He should send it back.

 

Dom Q.


Edited by daquad, 22 May 2020 - 01:48 PM.


#42 SeattleScott

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Posted 22 May 2020 - 05:21 PM

Truthfully, the top of the line rack and pinion Focusers are completely different in design. The Vixen Focuser bears a strong resemblance to the Synta rack and pinion Focusers.

https://www.highpoin...rake-ftf3025b-a

I would try a diagonal of known quality.

Jon

Jon

Yes not saying Vixen R&P are premium but one shouldn’t shy away from a scope because it has R&P focuser. Haven’t used a Synta R&P. Have used a Synta crayford and a couple affordable Meade R&Ps and prefer the Vixen focuser to any of them.

But yes there appears to be an issue with the optics so it should indeed go back.

Scott

#43 markb

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Posted 24 May 2020 - 11:02 PM

I agree with all the above comments on the optics, pinched or defective and you should return it for a new scope. Not the norm for vixen.

 

I recently bought two used 'take offs' of this vixen focuser. The Synta of the 90s and later was a poorly done copy, but also massively benefited from the changes, below. I actually did these modifications on the Synta first, and when I got the Vixen I was disappointed with the lack of smoothness so I applied the same fixes.

 

I located 5 mil UHMW tape on Amazon and put thin strips over the guide rails inside the focuser body after removing the knob and pinion shaft and sliding the rack and tube out. I also put a narrow strip on the top nylon or ptfe pressure bar. There was adequate clearance for the tape, the thinnest made by 3M to the best of my knowledge. I also removed the grease on the rack and pinion (the Synta one had the usual glue), and, after research on cloudy nights, replaced it with super lube synthetic grease with Teflon, not the silicon-based super lube that I already had. This instead of Grease did much better under the stresses of the rack and pinion. I ended up with a wonderfully smooth focuser, and even the Synta ones I had done before were smoother than the unaltered vixen focuser, but not as good as the altered Vixen.

 

UHMW tape, and the even thinner Kapton tape (I get mine from watch materials houses) are close in friction coefficient to pure Teflon.

 

I'm surprised Vixen has not updated this focuser. The latest gso r&p are much smoother.

 

But the clear aperture through the focuser tube is the reason i looked for one.

 

As for the knobs, my 20year old Vixen ring and dovetail set that once held my Jaeger's 4" long fl tube were, I think, identical. Worked fine, nicely shaped and finished.


Edited by markb, 25 May 2020 - 07:12 PM.


#44 donadani

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Posted 24 May 2020 - 11:44 PM

You could buy a used 102M. For the price you payed you will get a GP mount, tripod and some eyepieces on top.

 

Plastic parts and paintjob on these oldies is much better then on the actual generation. No cheapish "Made in China" parts included - instead they had a very good 6x30 finder and a nice "Made in Japan" glas prism diagonal. 

 

Had some of the Vixen Achromats from that time 80L, 90M, 90L, 102M - all had good to very good optics - worst I´ve seen with them was some light spherical abberation in a grade that in no way decreased the views. Some of them had really outstanding good optics.

 

Focuser is about the same as the one you have - if you don´t need 2" equipment take one with the 1,25" focuser - I found them more even and stable over the time then the 2" ones.

 

cs

Chris


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#45 beanerds

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Posted 25 May 2020 - 05:58 AM

Did a Google and the only Vixen A102M is this one an oldie but definatly a goodie ,,, Zero on the A105MII  ? 

 

Beanerds .

Attached Thumbnails

  • Vixen SP 102M.jpg


#46 SeattleScott

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Posted 25 May 2020 - 03:20 PM

Yeah I have three Vixen scopes including a A105M but never heard of a A105MII. I assume it was a typo or something.

Scott

#47 gamma_ari

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Posted 25 May 2020 - 03:43 PM

Not a typo, the current version is called A105MII:

 

https://global.vixen...roduct/26071_3/

 

Best,

Viktor



#48 SeattleScott

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Posted 25 May 2020 - 04:00 PM

Ah so it is. Vixen Optics wasn’t showing the new model. Apparently it isn’t updated as often as the Japan site. It looks exactly like the A105M and costs exactly as much so I’m not sure what the difference is. Says less color fringing (less than what?). Conceivably they might have respaced the lenses so more red is out of focus than blue. Or it could be exactly the same scope.

Scott

#49 Nippon

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Posted 25 May 2020 - 06:31 PM

The Vixen flip mirror is not a top quality item. I got one with an A 105M I bought in 2012. It was badly astigmatic. I put my TV Evebright in and star tested and the test was perfect. The missing paint looks like where the dew shield slides on not where the objective cell screws on. Those are the same plastic tube ring knobs with 6mm metal screw that Vixen has been using for decades. Want to see grease stripes on the focuser drawtube just like your Vixen? Look at any Takahashi refractor. Vixen focusers are adjustable and can be tuned to nice performance. Personally I'd star test it with a good diagonal and If it tests really well I'd slide the dew shield off, fix the missing paint with a little flat black model paint and call it a day. I'd rather have a scope with real excellent optics and a very fixable blemish than a cosmetically prefect scope with so so optics. My 105's optics were so good I gave it to my grandkids and bought the Vixen ED 1003s which also has a perfect star test.



#50 Nippon

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Posted 25 May 2020 - 06:56 PM

Pinched optics would be highly unusual for a Vixen refractor given the lenses are cemented in place. There are no collimation adjustments so there is nothing to pinch unless the scope has suffered some sort of trauma.

What magnification were you using for the star test? At low power it could be astigmatism from your own eye. I always use at least 100x.

And there is still the question of the diagonal. Obviously you have other scopes with other diagonals. Use one of your other diagonals and use at least 100x magnification for the star test after at least a half hour of cooling. If you are still seeing the odd star test, then I would say there is something wrong. It is conceivable that the missing spot of paint near the lens cell is the result of a mishap at the factory or during shipping.

So it sounds like you want premium optics rather than mass produced, hence you got the A105M even though you have the TS Apo. There aren’t really any other premium achros on the market, so you can see if you can sort out the optical issue (swap diagonal or whatever), return it for a replacement if the optics really are bad, or get a premium brand Apo. The premium Apo will obviously be more expensive, with Vixen being generally the cheapest (beginning of the high end) at $2k or so for the SD103S.

As for the build quality of your 62mm achro being better, consider that it doesn’t cost much less than the A105M.

Scott

They are not cemented in place. It is an air spaced Fronhaufer doublet I had to remove a spider web from the back of the objective. The lenses are held in place with a retaining ring and is not screwed down tight at all. 




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