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Vixen VMC110

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#1 nightfisher

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Posted 14 August 2014 - 02:51 PM

Ok, so i have just bought a new vmc110, this will be used on my AZ supertrack mount for Solar system obs and imaging, it will be interesting to see how it performs, i only got it because my lady told me to treat myself..................so i did  :grin:

 

What are peoples opinions on this light weight little Mak/Cass/Klev


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#2 tomjones

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Posted 14 August 2014 - 08:05 PM

SEND IT BACK!  SEND IT BACK!

Maybe ok for low power pics, it's a disaster for visual at anything over 130x.

Sure is pretty though.



#3 jhayes_tucson

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Posted 14 August 2014 - 10:41 PM

Interesting...I have a VMC95L that I use for a guide scope and the imaging is quite good.  It does not appear to be a very thermally stable scope and requires a bit of time to stabilize but once there, the imaging appears to be about what I'd expect from a 95 mm scope with pinpoint stars.  I haven't tried it so maybe the 110 mm version isn't as good.

John



#4 kkokkolis

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Posted 15 August 2014 - 04:16 AM

I always liked the way it looked and it's price but never tried it worrying about the thick spider my C4 lacks. I'm still curious about how it compares with a classic MakCass though. I know somebody that filed his VISAK's spider to thin the imaged spikes. 



#5 jhayes_tucson

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Posted 15 August 2014 - 11:04 AM

You certainly lose some energy to the thick spikes but I don't think that it's a big deal.  If I wanted better imaging, I'd just get a bigger scope.  For me, the built in flip mirror is the real advantage of these little Vixen scopes.  It makes them absolutely ideal for use as a guide scope.  To be clear, I don't spend a lot of time observing with my VMC95L.  However, I do look at star images up close with my guide camera and they are very small and very round.  That's a fundamental requirement for good imaging.  It's not the only thing thing that is important, but it's a good start.  I give the appearance, the mechanics, and the features an A+.  The optics (on mine anyway) appear to be "good enough", but there may be scopes in this size range that are better.  I just don't know. They aren't that expensive so I'd personally consider buying another one to try it out.

 

John


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#6 nightfisher

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Posted 15 August 2014 - 01:05 PM

Thanks for the replies so far, please bear in mind i have only got this for Lunar A-focal and or webcam 



#7 bicparker

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Posted 16 August 2014 - 10:04 AM

First, I have a VMC110L, so this isn't about what I've heard or think it may be.  Second, I'm a visual observer, so I can't really comment on any imaging efforts.

 

I bought this scope with the notion that it was small, but had around a 4" aperture, which were features for which I was looking.  It was also relatively inexpensive.  Nothing is free, however, and assumed that there was a potential for some corners being cut somewhere.  So I was going into this more as a grand experiment (well not that grand, but I thought it would fun).

 

The overall build quality of the tube is good.  It is all metal with a very well done fit and finish.  The diagonal and spider is all metal, as well (the flat black color and its shape makes it look like it is possibly plastic, but it is not).   It has two attachment points for the included dovetail bar, one on the side and one on the bottom, so you can easily attach it to a conventional mount or certain side mounts (such as the Vixen Porta II, what a coincidence) and maintain its orientation.  There are two control knobs on the back, the focus knob and the flip mirror knob.  They are both mechanically sound, the focuser having a nice smooth action with just enough resistance that you can tell it is working (this is really an important thing to understand, especially when you are in the dark).  There wasn't any slop in my focuser, in other words, when I changed direction of focus it changed immediately without any detectable take-up (this was confirmed in actual optical use). The flip mirror control works well with what feels like a cam controlled positive click in both mirror positions.

 

Sometimes I hear comments about clean lines and it isn't always clear what that means.  Outward appearances are a nice aesthetic, but that does not always add to function.  Well, in this case, the VMC110L has very clean lines, which makes it an easy form factor for packing, so its appearance does add to the function.

 

So, generally the build, fit, and finish are pretty good, and if you could base the value of the telescope on those aspects alone, then the price charged is actually a very good deal indeed.  But this is a telescope and ultimately the optics are what really counts.  Related to the optics are the mechanics, the stuff that lets you adjust the optics.

 

The short story, the straight through optics are quite good, but the built in flip diagonal mirror is a major weak point that compromises an otherwise fairly decent optical system.  Additionally, the collimation adjustment screws are there, but they are compromised by the fact they are glued in place.  The focuser is indeed smooth and responsive, but there is a slight mirror shift when you change focusing directions.  I will take each of these separately.

 

The main problem with the flip diagonal is that it isn't collimated, nor is it easily adjustable.  Because of its misalignment, you cannot collimate the scope through the flip mirror. However, the straight through collimation (with the mirror up out of the optical path) was actually quite good in the model as it came (checking with a Cheshire and an autocollimator and then later with a star test).   So I put a diagonal on the back and use it only in the straight through configuration.  But I still wanted to have the ability to fine tune my collimation.

 

The collimation screws are push/pull pairs in 3 spots found in the back of the OTA.  Two pair are behind fitted rubber gaskets and the third pair is behind the flip control knob, which is actually pretty easy to remove.  The screws are glued, are deep in a well in the back of the scope, and they are Phillips head aluminum, so don't try to force them loose or you will strip the heads and have a more difficult situation to fix.  In my case, I poured a few drops of 91% alcohol into each of the wells and let them soak for a while.  Then I used the best fitting Phillips head screwdriver I had and began to gently rock each screw until it broke loose.   If you go to the Vixen Optics USA web site, the US distributor for Vixen, you can download an augmented instruction manual (not the standard one provided from Vixen) for the VMC110L that describes all of this with some pretty good pictures showing the collimation points and how to make adjustments using the push/pull screws.

 

If you want to replace the screws with something less easily strippable, made of stainless, you will be looking for #4-48 screws, which are not standard at your box hardware stores (you will find #4-40 if you find anything in a #4 size, and they won't work at all).   Likely, you will have to order these online unless you have a specialty hardware source that stocks these (fortunately, San Antonio is a nearby city for me and one of the manufacturers of these screws is there).

 

The collimation can be fine tuned quite well and if you are willing to work with the adjustments, you can actually make this telescope sing well optically.  Before I tweaked the collimation, Saturn view started to degrade at around 150x.  After tweaking, I was able to take the magnification up to 172-207x pretty comfortably.   It seems to hold the collimation well, also.  So if you willing to invest a bit of time, you can have an instrument that will yield some very nice views.

 

A couple of additional notes - There has been some talk about the larger central obstruction and thicker curved spider vanes causing a degradation of potential contrast (a lot of these posts on various boards have been from non-owners, by the way, though I have seen that comment from at least one person who owned one).  When properly collimated and using a good quality eyepiece, this instrument yields a very nicely contrasted image (with no spikes, which means the spider design works, of course).  I suspect that a lot of perceived contrast degradation came from collimation problems more than actual contrast reduction from the secondary and spider.

 

As many owners of this scope have mentioned, the cap for the scope is a bit of a tight fit, but I really haven't had any problems with it.

 

Also, the supplied single reflex finder is mechanically a piece of junk in my opinion.  It is simply a poor design that looks a bit cobbled and it does not hold its adjustment well.  The switching mechanism also failed early on in its life (after I had already decided to replace it with something better).  A reflex finder is all you really need with this scope, so just find a good dot finder that uses a finder dovetail and you will be in great shape.

 

So, in summary, overall this is a good scope for the price (at least in my opinion), and if you are willing to spend a little bit of time on its adjustments, you can make this a great portable scope for lunar/planetary work and some of the brighter DSO's.  It is a very packable design and the optics, when tuned properly, are very good.  However, I would not count on using the built-in diagonal and you will need to replace the finder.   So you will still be out the additional cost of a good quality 1.25" diagonal and a reflex finder.   I am really enjoying this scope and it is a great grab and go instrument, but if you are looking for something that is a bit more turn-key there are other options to consider.

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#8 nightfisher

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Posted 16 August 2014 - 12:26 PM

David, many thanks, your post is very comprehensive, i have only bought this little mak as a portable scope, this should work well, i do have better scopes to use in anger, but this Vixen should be a lot of fun, i had a very brief first light last night just to check collimation, and it seems pretty good



#9 Glenilacqua

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Posted 23 January 2015 - 12:31 PM

I'm considering buying this scope for use on a small dovetail tracking mount. I have an f6.5 102mm Apochromat that I use for wide field viewing. I'd like to use the Vixen VMC110L for the moon, planets and higher magnification applications. I have a wide range of eyepieces from elaborate 8-element widefied designs, medium priced plossls, and even some very nicely made Kellners. I'd love to hear a long-term report of your satisfaction and what eyepiece configurations do best with this model. Any advice is welcome!

 

Thanks

 

Glen



#10 DaveG

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Posted 23 January 2015 - 01:12 PM

I've personally never used the VMC110, but I've read a few reviews that it's ok up to about 100x. Higher than that, and the images get pretty soft. IMO, I think you would be better off with your apo at higher powers.



#11 desertlens

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Posted 23 January 2015 - 01:42 PM

Thanks to David for the valuable info. There's a lot to like about this little package and now I have a better sense of how to collimate it. The Vixen info seems pretty straightforward. The screw cementing and thread size info is especially useful. The attached photo of the recent eclipse and AR2192 was done with the VMC110L, Baader solar film and a DSLR on a Porta II (the perfect AZ mount for this scope). I thought it did pretty well.

 

eclipse10_23_14blg.jpg


Edited by desertlens, 23 January 2015 - 01:44 PM.

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#12 Glen A W

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Posted 24 January 2015 - 08:54 PM

Nice pic!  People told me my Vixen 260 would suffer from low contrast for the same reasons, and then it turned out to be a treasure for the planets, and light and portable, too.  I love Vixens and if I were starting over, I'd probably not have two small refractors and would have one scope like yours instead.

 

Glen



#13 james101

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Posted 25 February 2015 - 08:07 AM

Yes this scope can be a bit on the duller side but well collimated it actually is a great little scope... But like all things I like to tinker.  So if you want to improve things here are some facts and some options:

 

Scope opening/primary mirror 110mm (actually my callipers say 111mm, yippie 1mm for free

Secondary obstruction is 44mm (16% of opening)

4 curved spiders at 3.8mm thickness of 36mm length each (more on this below) creating an additional 6.5% obstruction all up.

 

Total obstruction area is nearly 22% stock.  But if you thin or remove, yes remove vanes (more on this later) you can drop total obstruction area to about 19%.  If you removed two vanes and thinned the remaining vanes you may even get a bit better, but I likely wouldn't recommend that... so more on the vanes:

 

Ok the vanes on these are cast aluminium, thick and deep.  It is so overkill it could hold my motorbike together!  Being an engineer I had to prove the facts about structurally adequacy of making these vanes thinner. So, the stock vanes have the following strength (units mm):

 

Area of Section 98.8
Section Modulus Zxx 428.1 
Section Modulus Zyy 62.57

 

Now when compared to a normal Newt very thin spider of say 0.8mm the Vixens have way more strength being over 500% Zxx and 2340% in Zyy.  When compared to a 1.5mm thick spider they have 275% and 665% more strength respectively.  When you consider that the secondary holder is part of the same cast piece with the spider the additional strength would be off the scale!!

 

Ok, remember these thick over engineered spiders are also only having to extend a very short distance compared to larger scopes where thinner spiders are often used. People have machined their 8" vixens down to around 0.8mm successfully that proves this...So these are very strong!!

 

Its therefore very safe to drop the vane thickness to 1.5mm, or less...in fact I would still call it over engineered.  But this is alot of grinding with a dremel, a royal pain in the arse.... But it occurred to me that if you just cut two spiders off with a small cut-off disc (which is much quicker) you get the same effect in reducing obstruction area but will look nicer.  2 vanes produce 2 diffraction spikes BUT because of the curved vane you don't even get that!!  Bonus...

 

Do this,don't use the stock diagonal, let it cool for at least 45min, get a really good diagonal, use a good eyepiece, whack it on a EQ5 AND make sure it is collimated well and your on your way to some really nice viewing for a superbly mobile and cheap package.

 

No I don't have images... but it certainly is picking up a little more detail on Jupiter, better at higher magnifications, stars seem a bit brighter and everything pops a little more.  Its subtle, not bam this makes a huge difference.  But considering it costs nothing... well you decide..


Edited by james101, 25 February 2015 - 08:07 AM.


#14 HandyAndy

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Posted 21 April 2018 - 05:46 AM

Hi

 

I am looking to use this for a solar scope.

 

I need to know how far back the focus point is for the nearest object/mirror focussed to the limit.

 

Point telescope out of room with curtains partially drawn at sky. Rack focus right back out. Use a white card or eye to find the brightly lit virtual exit pupil and measure how far back.

 

Thanks in advance.

 

Andrew.




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