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Vixen VMC 110L with binned flip mirror and new Takahashi prism fitted

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#26 nirvanix

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Posted 23 September 2019 - 11:00 AM

For the flocking I didn't remove the secondary - didn't feel it necessary. By tube ring you mean the plastic part containing the spider vanes? I can't remove mine - Perhaps it's glued into place?

 

I tried doing a quantitative analysis on the results of flocking and found that in my moderately light polluted back yard I was able to pick out stars .5 mags dimmer.



#27 Magnetic Field

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Posted 25 September 2019 - 12:18 PM

For the flocking I didn't remove the secondary - didn't feel it necessary. By tube ring you mean the plastic part containing the spider vanes? I can't remove mine - Perhaps it's glued into place?

 

I tried doing a quantitative analysis on the results of flocking and found that in my moderately light polluted back yard I was able to pick out stars .5 mags dimmer.

 

Yes the black big ring. Though I am not sure mine is plastic.

 

1/2 a magnitude is actually quite good.**

 

What I never understand with manufacturers: why don't they use better (I mean really, really black) paint. There must be paint around which has the same absorption qualities than say a bog standard velour material. I know good paint is expensive but I doubt it would cost them more than the paint they already use.

 

** Do the prism. Maybe you get another 1/4 of a magnitude out of it.


Edited by Magnetic Field, 25 September 2019 - 12:20 PM.

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#28 nirvanix

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Posted 26 September 2019 - 03:28 PM

Yes, I was tickled to see all the extra stars in several open clusters. Some clusters have a lot of stars in the 10.5 to 11.5 mag range.

 

I've flocked all of my telescopes because they all had that same shiny charcoal paint in them. Maybe one of the manufacturers will eventually grab a clue and give themselves a competitive edge by advertising a better paint or flocking.

 

I spent several days using the VMC straight through and found the view to be equal to but not qualitatively superior to my flip mirror, so I think I've got a decent mirror; I just don't like the housing it's in. You may have had a poor sample of mirror.



#29 Magnetic Field

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Posted 28 September 2019 - 05:17 AM

Yes, I was tickled to see all the extra stars in several open clusters. Some clusters have a lot of stars in the 10.5 to 11.5 mag range.

 

I've flocked all of my telescopes because they all had that same shiny charcoal paint in them. Maybe one of the manufacturers will eventually grab a clue and give themselves a competitive edge by advertising a better paint or flocking.

 

I spent several days using the VMC straight through and found the view to be equal to but not qualitatively superior to my flip mirror, so I think I've got a decent mirror; I just don't like the housing it's in. You may have had a poor sample of mirror.

This is the problem: the rubbish flip mirror was never aligned with the optical axis.

 

The cross-hair in my  Cheshire collimation eyepiece aligns now with the optical axis. The cross-hair  is pretty much in the centre (of the prism)  after I have collimated the main mirror with a real star (the Cheshire eyepiece on its own is useless for collimation and I only used it for a sanity check and out of curiosity).

 

Compqre this to the flip-mirror. Even after I have collimated the main mirror with a star the cross-hair centre was always fairly far off from the centre of the flip-mirror. This was a tell tale sign that the flip mirror was never meant to be part of the optical train. Very well done Vixen.

 

Btw: Even if the flip mirror were fully aligned with the optical train the prism is still worth a shilling because it  reduces scatter around planets.


Edited by Magnetic Field, 29 September 2019 - 04:02 AM.

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#30 nirvanix

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Posted 30 September 2019 - 03:02 PM

Couldn't agree more about the flip mirror housing - it's a shabby thing. Since the planets are so low at my location I've taken to straight through viewing them with the VMC and my refractor. That trumps any diagonal. For the next year or so their elevation is the limiting factor in my views.



#31 nirvanix

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Posted 31 October 2019 - 03:02 PM

I managed to get the front end/secondary holder off.  It's cast aluminum and threaded on. Not sure why it came off readily now after trying quite forcefully in the past. The spider vanes are nearly 4mm thick at the back (2mm at the front):

 

secondary.JPG

 

I filed them down to 1.5 mm straight across from front to back. Performance results are spectacular, to say the least. Even in daytime use contrast/clarity is improved.

 

vmc95l.JPG


Edited by nirvanix, 31 October 2019 - 03:04 PM.

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#32 Magnetic Field

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Posted 02 November 2019 - 10:34 AM

I managed to get the front end/secondary holder off.  It's cast aluminum and threaded on. Not sure why it came off readily now after trying quite forcefully in the past. The spider vanes are nearly 4mm thick at the back (2mm at the front):

 

attachicon.gif secondary.JPG

 

I filed them down to 1.5 mm straight across from front to back. Performance results are spectacular, to say the least. Even in daytime use contrast/clarity is improved.

 

attachicon.gif vmc95l.JPG

Very good.

 

I'd like to ask: did you use a bog standard needle file or some mini tool hand machinery?

 

How long did the job take?



#33 nirvanix

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Posted 02 November 2019 - 04:19 PM

Hi MF. I used a bog standard medium coarse file with rounded/flat sides and about 3/4 inch across, but I also had a fine needle file to do a little touching up. Job took about 1.5 hours because I went kinda gentle with it, but I imagine it could be done in a half hour. I just finished painting her up this morning (Rustoleum Painter's Touch Ultimate flat black primer) so here's a shot of the finished piece:

 

IMG_0972.JPG

 

I left the ends of the vanes a little wide for structural integrity.

 

Had the scope out again last night and am genuinely amazed at the performance upgrade this produces. Delta Cygni (mag 3) at 175x in good seeing is just the airy disk and first diffraction ring - nothing else there except black space. Gone is the scatter and diffraction "swirls". Prior to this mod I needed 175x to split Izar, but it now splits at 127x. The Pleiades no longer have an artificial Merope nebula - just the stars, and Saturn no longer has a glowing atmosphere.

 

Thick curved spider vanes should not be used in a telescope. Straight thick ones are ok as you just get spikes not a haze of scatter. This is a game changing mod, but it's a big-boy mod so if you do it:

 

Put alignment marks on the OTA and front end so you know where to thread it back,

Tape over the secondary holder very well with masking tape,

Don't apply tons of force, let the file do the work.

 

 


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#34 Magnetic Field

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Posted 03 November 2019 - 09:29 AM

Hi MF. I used a bog standard medium coarse file with rounded/flat sides and about 3/4 inch across, but I also had a fine needle file to do a little touching up. Job took about 1.5 hours because I went kinda gentle with it, but I imagine it could be done in a half hour. I just finished painting her up this morning (Rustoleum Painter's Touch Ultimate flat black primer) so here's a shot of the finished piece:

 

attachicon.gif IMG_0972.JPG

 

I left the ends of the vanes a little wide for structural integrity.

 

Had the scope out again last night and am genuinely amazed at the performance upgrade this produces. Delta Cygni (mag 3) at 175x in good seeing is just the airy disk and first diffraction ring - nothing else there except black space. Gone is the scatter and diffraction "swirls". Prior to this mod I needed 175x to split Izar, but it now splits at 127x. The Pleiades no longer have an artificial Merope nebula - just the stars, and Saturn no longer has a glowing atmosphere.

 

Thick curved spider vanes should not be used in a telescope. Straight thick ones are ok as you just get spikes not a haze of scatter. This is a game changing mod, but it's a big-boy mod so if you do it:

 

Put alignment marks on the OTA and front end so you know where to thread it back,

Tape over the secondary holder very well with masking tape,

Don't apply tons of force, let the file do the work.

 

What baffles me is the following: you mentioned the thickness of the vanes is differential (2mm vs 4mm) and differs by more than just machining tolerances.

 

Vixen did go all the way to introduce additional machining costs instead of milling vanes with a flat 2mm.

 

I am wondering if they did it in on purpose. I don't know what it would be though (thermal stability, collimation is better held in place with stout spider vanes, etc.).



#35 nirvanix

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Posted 04 November 2019 - 04:33 PM

They are cast aluminum so they didn't have to mill them, just pour them into a mold. The Japanese seem to like thick cast aluminum for spiders, both Vixen and Tak. I think they should go to thin steel ones, such as the AstroSystems spider on my 13" dob. The vanes are 0.7mm thick.

 

Why Vixen choose to "hide" the thickness at the back I'm not sure. I think the way I've filed them they are still quite strong. Have had it out in -10C without any collimation changes. At some point I  might even acquire some sub-millimeter steel strapping and make 3 straight vanes for it and J-B Weld them into place. It would be an interesting experiment.


Edited by nirvanix, 04 November 2019 - 04:34 PM.


#36 nirvanix

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Posted 07 November 2019 - 04:16 PM

I had the VMC out on Tuesday night with temps probably -15 C or colder. Performed beautifully on some doubles. Warmed up on Meissa and beta Mons, then got a clean split of iota Leo at 175x.  That's a first for this scope. Also, the Orion nebula was twice as large as it usually looks with the scope because of reduced haze.

 

I think the stock VMC95 and 110, because of diffraction "haze", cannot be considered serious astronomical telescopes. Good for birding, looking at the moon, some mag 4-5 doubles and moderately bright open clusters, but everything else is washed out. It's a design flaw really. Now after this mod, flocking, and fixing the flip mirror and secondary mounting I finally have the scope that I wanted. It's a keeper. smile.gif


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#37 nirvanix

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Posted 13 November 2019 - 03:35 PM

Have split delta Cygni twice over the past week, and the split was confirmed by my refractor which I had out at the same time. Speaking of refractors, the little VMC seems to think it's one after modding the spider vanes. If you put it in a black box with the eyepiece sticking out, and an opening for the front of course, and then had people look through the eyepiece they might well guess it's an apo.

 

I'm waiting for some good seeing to how how close I can get to the Dawe's limit (about 1.2 arcsec)  for this scope.


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#38 photoracer18

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Posted 15 November 2019 - 04:34 PM

I pretty much doubt the 95mm LOMO has something to show for it when we talk about deep sky observing (due to the small aperture). I once owned a Meade ETX-90 and by all means it was completely useless for everything.

 

Even with the rubbish flip mirror the Vixen VMC 110L is an excellent deep sky performer (pin point stars at least for visual observing).

I used to work for a Vixen dealer for a number of years. I have owned something like 7 or 8 of their scopes including refractors, Newtonians, and Cats. Notice I don't currently own any. Last one was a Vixen FL-80S Fluorite, by far the best of the bunch overall. 2 things that eventually dropped it from my quest for the perfect travel scope, in spite of the optical performance, was it was F8 and had a non-retractable dew shield (same things that knocked out small Taks).

As for the VMCs I agree the flip mirror is junk and I applaud your project to work around it.  Like the Meades I don't like the pseudo- Questar mechanicals. As for the LOMO 95 we sold all the ones we had left in stock to a bunch of long range shooters who found they could clearly see .30 cal. bullet holes in the black of paper targets at 1000 yards. They bought one and then came back and bought all the rest. I had to buy mine from one of our former customers to get one.

We were LOMO dealers also (and Meade, Celestron, Takahashi, Stellarvue, Pentax, Zeiss, Intes/Intes Micro, and Skywatcher).


Edited by photoracer18, 15 November 2019 - 04:37 PM.

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#39 Magnetic Field

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Posted 06 January 2020 - 05:56 AM

I used to work for a Vixen dealer for a number of years. I have owned something like 7 or 8 of their scopes including refractors, Newtonians, and Cats. Notice I don't currently own any. Last one was a Vixen FL-80S Fluorite, by far the best of the bunch overall. 2 things that eventually dropped it from my quest for the perfect travel scope, in spite of the optical performance, was it was F8 and had a non-retractable dew shield (same things that knocked out small Taks).

As for the VMCs I agree the flip mirror is junk and I applaud your project to work around it.  Like the Meades I don't like the pseudo- Questar mechanicals. As for the LOMO 95 we sold all the ones we had left in stock to a bunch of long range shooters who found they could clearly see .30 cal. bullet holes in the black of paper targets at 1000 yards. They bought one and then came back and bought all the rest. I had to buy mine from one of our former customers to get one.

We were LOMO dealers also (and Meade, Celestron, Takahashi, Stellarvue, Pentax, Zeiss, Intes/Intes Micro, and Skywatcher).

That is the reason why I want a Borg 89ED f6.7.***

 

Travelling with my Vixen VMC 110L (110mm aperture though 5" tube) in a backpack can be done. But some overhead lockers in smaller aircrafts are fairly small. The Borg 89ED would be ideal in my laptop backpack (because the objective lens item can be separated from the main tube).

 

80mm is too small and I haven't found a 90mm ED refractor that can be stowed away as hand luggage in a laptop backpack (currently a Ogio Renegade RSS). Also it should work with a Vixen Mini Porta (that fits into my checked in Ogio Terminal Travel Bag); this means no more than 2.5kg (which only the Borg would fulfill).

 

Funny though. It is completely random if they ask me to open my backpack while going through security at airports. Today, I think they asked me to open it to show to an apprentice what it is.

 

***The Borg 89ED f6.7 is out of production (confirmed by Astro Hutech in private communication). The Borg 90FL fluorite though has only f=500 (I would need special oculars or a barlow lens). But I have no luck on astromart UK. If anyone from the UK wants to sell me his Borg 89ED please contact me. Thanks.


Edited by Magnetic Field, 06 January 2020 - 06:19 AM.

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#40 Magnetic Field

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Posted 06 January 2020 - 06:42 AM

Have split delta Cygni twice over the past week, and the split was confirmed by my refractor which I had out at the same time. Speaking of refractors, the little VMC seems to think it's one after modding the spider vanes. If you put it in a black box with the eyepiece sticking out, and an opening for the front of course, and then had people look through the eyepiece they might well guess it's an apo.

 

I'm waiting for some good seeing to how how close I can get to the Dawe's limit (about 1.2 arcsec)  for this scope.

There is a new challenge: https://www.cloudyni...vixen-vmc-110l/

 

Although I think it has been solved (post #11 in the above link) and I mistook a close background star for the companion. This has to be double checked when I am back in the UK though.


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#41 nirvanix

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Posted 06 January 2020 - 04:08 PM

Nice post in the doubles forum MF. I've got a list of tight doubles to try, just awaiting plausible seeing conditions. Over the last few weeks can barely split Meissa (~ 5 arcsec). In all my scopes the stars are looking like fuzzballs. Never encountered a stretch of bad sky like this.

 

Have you tried the triple 12 Lynx? Think it would be a nice one for your 110L.



#42 Magnetic Field

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Posted 09 January 2020 - 03:24 AM

Nice post in the doubles forum MF. I've got a list of tight doubles to try, just awaiting plausible seeing conditions. Over the last few weeks can barely split Meissa (~ 5 arcsec). In all my scopes the stars are looking like fuzzballs. Never encountered a stretch of bad sky like this.

 

Have you tried the triple 12 Lynx? Think it would be a nice one for your 110L.

Can someone please have a go on Delta Ursae Minoris. I thought I split it easily. However, zooming in on the 0.5 degree field of view in Skychart shows a second star close the Delta Ursae Minoris and I wonder if the situation is similar to Iota Ursae Majoris.

 

The double star companion of Delta UMinor is only 11.8 mag if we believe Skychart. My observing place in the valley in the Alps as I mentioned in the double star post is probably a Bortle 3 sky (but you would surprised of the amount of light pollution even in a little village; I am always just too lazy to drive up to skiing resorts which only would take me 50 minutesnor to higher grounds; funny though in summer I do it often with my road bicycle).

 

I will try it in the UK.

Delta UMajor 2.jpeg

 

Delta UMinor.jpeg


Edited by Magnetic Field, 09 January 2020 - 03:25 AM.



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