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Vixen VMC 200L - Opinions?

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#76 Charlie B

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Posted 08 September 2018 - 06:50 AM

My VMC200L arrived yesterday evening, but I didn't get it unpacked until after work today -- thanks to Tom for a very thorough packing job, it made it from Cali to Alabami with zero damage.  The collimation was close, and I tweaked the primary to get it closer to dead center, but I didn't have time for a push-me/pull-you with Allen wrenches -- I had to get it in the shed to temp adapt (high today was 92F / HE 101F).  Also, I noticed that the collimation point on the laser shifted very slightly as I racked the focuser in & out, so that'll have to be tightened up. 

 

It has the built-in long dovetail, so I put a pair of Sheldon's machined aluminum couplings on my TAK EM-1S + the large counterweight (I'll try to get a photo of the rig posted tomorrow), which is on a vintage Filotecnica wooden surveyor tripod.  With the spikes pressed in it's a very stable platform, and the TAK tracks near perfectly when the load is balanced.

 

Star Tests:  I started with Arcturus.  It was lower than I prefer, but I needed to align the 50mm finder.  Took longer than usual -- that thing fought me!  Used a UO HD OR9mm.  Tight rings, but very very slightly off center -- as expected.  Lots of wash that low, so I spun over to Sadr, which was nearing the meridian.  Much more stable image, but same pattern.  I really can't blame the scope, I knew the collimation wasn't perfect. I expected the stars to be smeared at focus, but they were small & tight.  Not the micro-dots of my Vixen 80mm fluorite, but not blobs, either.

 

Seeing:  Gordon saturated the ground, and it was clear & HOT today, so The Swamp had its usual haze band from the horizon to 15* - 20* -- variable thickness.  The Vixen 80 was out to confirm seeing.  Jupiter was already in the mire, but Saturn was well placed, with practically no haze.  Still, seeing hopped between 6 & 8, so magnification went from 98x to 260x.

 

First of all, Saturn was bright -- about like my APM 152 F8 ED.  At 98x, besides Titan, I spotted 3 other moons -- and possibly a 4th in the variable seeing.  I ran most of my 1.25" eyepieces through first, and had no problem reaching focus while using a Baader prism diagonal.  It was while I was testing my vintage spectros Plossls that I got a long period -- at least 15 minutes -- of 8/10 seeing, which is when I topped out at 260x with the 7.5mm.  These are Swiss-made .965" eyepieces that I think are very close to my Zeiss for quality.  I got my best views of Saturn's disk at 195x with the PL10 - one of my favorites in the set.  Saw 4 belts.  IIRC, from the EQ, colors were subtle, gray-green, pale yellow-tan, very light rose, &  dark gray (I didn't make notes, so the order my be off).  Pewter to gray polar region.

 

Switched to DSO mode.  Truth:  I toted the complete rig from the north end to the center of the back yard -- at least 60 feet -- without pain or injury.  Swapped the Baader for a GSO 2" dielectric mirror + vintage UO Erfle 32mm for 61x.  Set the Vixen 80 close enough to compare views, with the Baader + vintage Jaegers Erfle 16mm for 40x.  M57 is a true smoke ring in the VMC with a black center.  M56 is brighter & larger than in my 6" reflectors, but no better resolved.  Star colors in the VMC look a bit redder than in the V80 fluorite, which to me has the most natural colors of any of my scopes -- really saw this with Sadr.  Naturally, all my favorite star fields from Sadr to Deneb are richer in this 8" scope.

 

Overall, I'd call this a good first sky test.  With exact collimation, I think the planetary views could compete with my 6" APO at equivalent powers, but I doubt this CAT can stay sharp at 80x per inch like the frac.  OTOH, it's a good choice when I don't feel like hauling out that much heavier rig -- that is not mobile at all.

Weather still bad!  Gordon sent lots of clouds my way.  Did not even try the star party, since I hate camping in the rain.  Good report and fair skies.

 

Regards,

 

Charlie B


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#77 payner

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Posted 08 September 2018 - 09:19 AM

Good first impression report, Bomber. Enjoyed the read.  Our skies are thick clouds/rain beginning yesterday and forecast into Monday with the remnants of Gordon.  Anyway, enjoy the Vixen and look forward to hearing more once you have some more time with it.

 

Randy


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#78 Peter Besenbruch

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Posted 10 September 2018 - 12:04 AM

Seeing:  Gordon saturated the ground,

Glad you survived Gordon. Nice report.


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#79 Bomber Bob

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Posted 13 September 2018 - 03:42 PM

For a while I owned a vintage Kenko 125C  (Corrected Dall-Kirkham Cassegrain), and this VMC200L reminds me a lot of that scope.  The 125C was an F8 system, and it had better resolution than a similar age Celestron C5 white tube spotter.  Collimating the 125C was also critical, but its correcting lens assembly was in the primary mirror baffle, so tilting that mirror cell affected both optics.

 

We're forecast to have clear skies this weekend.  Got my fingers crossed -- I'd like to have better seeing for sky testing than the first night out.



#80 Bomber Bob

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Posted 15 September 2018 - 03:46 PM

Worked on the VMC this morning.  First, I stiffened the focuser with the two tiny grub screws on top.  No slop now in the focus tube.  Next, I used both my Cheshire and LASER to nail alignment.  Finally, I removed dust from the optics and the tube interior.  

 

Right now, seeing will be near ideal tonight for planetary.  I'm hoping Florence won't dip or slip SW too much.  Based on yesterday's forecasts, the cold front was supposed to start tugging it north and away from the Carolinas, but not seeing that so far.


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#81 Bomber Bob

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Posted 15 September 2018 - 07:42 PM

VMC200L versus APM 152ED APO

 

Temperature [0030Z]  85°F (29°C)

Heat Index 93°F (34°C)

Humidity 70%
Wind Speed W 6 mph
Dewpoint 74°F (23°C)

 

Jupiter:  Both scopes at 100x, and the APM handily beats the VMC for resolution -- more belts visible, and sharper.  Both show the GRS.  It's brighter & redder in the VMC.  Galileans are tiny disks in the APM, small but fuzzier in the VMC.

 

Florence is sending thin streamer clouds from north to south, so I'm taking a cool-down break before tackling Saturn & Mars.

 

Saturn:  Started at 100x in both, then 200x, and ended at 300x -- the VMC got soft, the APM did not.  Saturn was in an area of volatile air, and seeing bounced between 6 & 7.  Cassini was blacker in the APM, and at 100x the rings seemed to float in space -- not a 3D effect but close.  Both showed 3 belts with similar colors, which were more intense in the VMC, but sharper in the APO.  Besides Titan, the APM showed 1 other moon, the VMC 2.

 

Mars was at the meridian, and I turned to it with the VMC first.  Yes!  It'll win this one for sure!  Nope.  Again, the APM resolves finer features at the same magnification.  Seeing was steady at 7, and the VMC stayed sharp at 300x -- the APM was good at 400x, but it's done better than that.  The disk had more orange in it than the APM, which agreed with what I saw with my own eyes.  

 

DSOs:  Here the VMC exceeded expectations, and soundly whipped the APM.  M13 is spectacular in this 8" CAT, with at least twice as many stars glittering in the much smaller field than the 6" APO.  And this was in moonglow!  M57 & M27 were larger, brighter, and more detailed in the VMC.  M29's familiar pattern was almost lost in all the faint background stars.  Naturally, the F8 APO has a wider field for Milky Way sweeping, but in all other categories, the CAT is where it's at.

 

The APO is also better for double stars; but honestly, this is subjective, and I'm a long-time refractor guy.  I found the VMC's spikes distracting with these; but on individual stars like Sadr, the effect was pretty.

 

Overall:  I bought the APM primarily for traditional refractor targets, and it excels as a planet killer.  But it takes a lot of effort to set up, and is not mobile (had to break it down to move it from the north end to the center of my back yard!).  The VMC is a DSO killer that's okay for casual planetary observing.  It's also easy to tote around the yard as needed, and rides on my very best EQ mount -- a Takahashi EM-1S on a Filotecnica wood surveyor tripod.  As such, I'm more likely to use it on work nights, which means it'll give me more views in the long run.
 


Edited by Bomber Bob, 15 September 2018 - 10:10 PM.

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#82 Bomber Bob

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Posted 16 September 2018 - 08:54 AM

After two sessions with this scope, I wish that I had a C8 for comparisons.  I have a vintage C5 that is very good, but the VMC isn't an SCT.  It's similar to the Kenko 125C, but I sold that scope.  The VMC has better optics & mechanics than the Kenko.

 

Initial balance is easy with the scope pointed north.  But in moving between hemispheres, the fixed dovetail means the 50mm finder & bracket throw that off.  I attached a 2 lb weight to the mount plate last night, but if I keep the scope, I'll find hinged rings for it.

 

Unlike the examples in the Vixen collimation guide, my VMC doesn't have exposed screws on the secondary cell -- a blue disk with the logo appears to be glued over those.  So the only accessible ones are for the primary mirror & focuser.  It makes fine alignment corrections trickier.  But the extra effort is worth it for the improved views.



#83 Charlie B

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Posted 16 September 2018 - 09:43 AM

 

Initial balance is easy with the scope pointed north.  But in moving between hemispheres, the fixed dovetail means the 50mm finder & bracket throw that off.  I attached a 2 lb weight to the mount plate last night, but if I keep the scope, I'll find hinged rings for it.

 

I added a Losmandy long dovetail to the bottom of the VMC. This makes balance much easier and is cheaper than split rings.  The existing dovetail has 2 1/4-20 holes that make mounting the dovetail easy.

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#84 payner

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Posted 16 September 2018 - 12:02 PM

Glad you are finding the Cat a useful tool in your arsenal of telescopes.  I can tell you, the diffraction spikes from the spider does not annoy me the least in my Mewlon.  I tend to agree, except for wide field view, the refractors have little on a very good catadioptric scope.  I can go deeper, gain noticeable resolution, brighter images, and as easy or easier to set up with substantially larger aperture Cat or reflectors.  Much less hassle on an inch-for-inch basis.

I have learned not to be rash in my decisions, but I do wonder about the true benefits in the five inch and larger refractors.  Perhaps what so many say around these parts is indeed correct, a refractor to about four inches has its place, for larger needs, other designs can be preferable.

 

Randy



#85 Bomber Bob

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Posted 16 September 2018 - 12:56 PM

I do wonder about the true benefits in the five inch and larger refractors.

 

High power planetary.  For folks observing in town, these large ED refractors are a great solution.  The lack of mobility isn't a handicap.  If we were staying at this house, I'd put a fixed pier & mount in the backyard, and all I'd have to carry out would be the OTA.

 

(If my tone is negative, 2018 has been the cloudiest year I can remember; and we've been in an extremely hot, humid, & cloudy summer for 4+ months.  The few nights out have been miserable.) 

 

The weather has forced me to value quick & portable.  The Vixen VMC200L is a big lightweight scope that delivers good planetary and excellent deep-sky views -- even in town.  I don't care for Dobs, and large Newts on EQ mounts aren't a good fit for my conditions -- even though I like them.  A C8 is an alternative, but by the time you add a wedge & tripod, it's not as mobile as my rig.

 

Also, I put the APM and VMC in my shed at the same time yesterday -- about an hour before sunset.  Both were ready at sundown.  I generally don't report on lunar comparisons, but neither scope had any thermal issues.


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#86 Bomber Bob

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Posted 16 September 2018 - 01:39 PM

I think the biggest issue for this scope is the price.  No way I'd buy a new one.  I got my used one for about half, and that's about what it's worth to me.  But I have lots of other scopes.

 

If I had zero scopes, and lived in town...  I'd give this scope serious consideration.  Pair it with an 80mm / 100mm APO, and you'd have most of the bases covered -- and they could share the same mount.

 

BIF:  Y'all should've seen these two big rigs together last night, about 8 feet apart, tracking the same objects like two robo-cannons locked on & ready to fire.  Saturn was in about the worst air, yet the refractor dealt with it better than the CAT.  Something that's been posted by others, I saw myself.  To keep the images in the VMC similarly sharp, I had to use about half the magnification of the APO.  Even in the frac, the air would boil occasionally, which is why I didn't spend much time observing it.

 

The 50mm finder is excellent.  Its bracket keeps its alignment after it's been removed & reinstalled from the quick release base -- another factor when you're rushing to have a brief after-work session.  Takes me maybe two minutes to set up / take down this rig.  It's not a grab & go (assembled, it's too tall to fit under my shed doors), but depending on your mount, it's a pretty easy 8" scope to deal with.  

 

The spider vanes don't bother me, but I like Casses & Newts -- the ones I have and the others I've used.  I did see some glare while observing the Moon, but if I keep the VMC, I'll flock the interior & blacken any shiny hardware in / near the light path.  That helped my other folded scopes.


Edited by Bomber Bob, 16 September 2018 - 03:21 PM.

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#87 Gregory

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Posted 16 September 2018 - 03:09 PM

To the OP:

 

If you have the urge to experiment, just order one of these:

 

https://www.astronom...escopes_c2.aspx

 

 

Gregory

 


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#88 sdufoer

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Posted 17 September 2018 - 07:18 AM

Unlike the examples in the Vixen collimation guide, my VMC doesn't have exposed screws on the secondary cell -- a blue disk with the logo appears to be glued over those.  So the only accessible ones are for the primary mirror & focuser.  It makes fine alignment corrections trickier.  But the extra effort is worth it for the improved views.

You have to get the sticker off, and then reattach it when secondary collimation is ok.  The glue comes loose.  The VC200L has the same "system".

I collimated like this:

1) Focuser with laser to the central hole in spider (you need to remove secondary).
2) Secondary collimation with returning laser beam.
3) Primary on startest and central obstruction.



#89 Bomber Bob

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Posted 17 September 2018 - 12:04 PM

You have to get the sticker off, and then reattach it when secondary collimation is ok.  The glue comes loose.

 

I don't like that.  Vixen should've made a thread-on cover -- like my 40 year old Dynamax 8 -- the owner shouldn't have to risk tearing / breaking something to perform routine maintenance.



#90 payner

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Posted 17 September 2018 - 05:45 PM

I do wonder about the true benefits in the five inch and larger refractors.

 

High power planetary.  For folks observing in town, these large ED refractors are a great solution.  The lack of mobility isn't a handicap.  If we were staying at this house, I'd put a fixed pier & mount in the backyard, and all I'd have to carry out would be the OTA.

 

(If my tone is negative, 2018 has been the cloudiest year I can remember; and we've been in an extremely hot, humid, & cloudy summer for 4+ months.  The few nights out have been miserable.) 

 

The weather has forced me to value quick & portable.  The Vixen VMC200L is a big lightweight scope that delivers good planetary and excellent deep-sky views -- even in town.  I don't care for Dobs, and large Newts on EQ mounts aren't a good fit for my conditions -- even though I like them.  A C8 is an alternative, but by the time you add a wedge & tripod, it's not as mobile as my rig.

 

Also, I put the APM and VMC in my shed at the same time yesterday -- about an hour before sunset.  Both were ready at sundown.  I generally don't report on lunar comparisons, but neither scope had any thermal issues.

Well, my pondering the 5-inch+ refractor was really rhetorical in nature.  I understand the personal preferences and nuances that go into folks' determination about what works for them.  It is just that other designs are often more efficient (e.g. size, cost to inch of aperture), and with high optical quality (relative to the same in the refractor), greater details may be achieved through those designs given one cannot usually afford, maintain and house a 7, 8, or 9 inch refractor.  Yet for example, a 10-inch DK (or similar) can easily be used and even considered portable by many.  But, I have a 5-inch refractor and see the benefits, though if I could not afford or otherwise have all the telescopes I have, then I believe for me (and likely many), a 4-inch refractor for what they do best, and the long(ish) focal length and sizable aperture Cat or reflector, would be the way to go.

 

Randy



#91 Bomber Bob

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Posted 17 September 2018 - 09:23 PM

All scopes involve compromises, and we make our purchase decisions based on those, plus our individual preferences & circumstances.

 

I've liked Casses ever since I got to see & use one as a teenager.  Folding a reflector, making a long scope compact, and putting the eyepiece in the traditional refractor location made sense to me -- what could be better?

 

I was an APO skeptic, but first my Vixen fluorite, and now this China-made ED have changed my opinion.  My APM 152 is shorter & lighter than my old D&G 5" F10 -- and presents truer colors with no fringing at the limb.  But an 8" F8?  No way!  Imagine the OTA mass + the mount to carry it!!  Maybe 30 years ago...

 

CATs like this VMC are a great compromise in size, weight, temp change, & cost.  A brand new one runs 1/2 to 1/3 the price of my 6" ED.  It can't take more than about 40x per inch, but on a summer night at The Swamp, I'll take it as it is.  And enjoy the views.

 

Would I be happier with a C8?  Based on my C5, probably not.  The VMC performs more like a refractor, and once I'm done improving it -- already found a set of hinged rings for it (thanks to Steve) -- it should easily outperform the Edmund 4" F15 Cass that I built, and my Tinsley 6" F20 -- a Cass that opens the curtains on M31's core, and shows the subtle beautiful colors of Saturn's disk.   


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#92 terraclarke

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Posted 18 September 2018 - 06:45 AM

I always liked the look of the VMC200s and almost bought one a few years ago. The big central obstruction, thick vanes and reported difficulties in collimation deterred me. There are a lot of comparison of them with C8s here on CN and elsewhere. I think Rolo did one, and so did Clamchip. The C8s always seem to either hold their own or win. The lack of the corrector plate and the traditional focuser and non-moving primary is a big draw but the simplicity of the tried and tested SCT design seems to win out. I’m happy with my two oranges.


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#93 Bomber Bob

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Posted 18 September 2018 - 02:29 PM

The C8s always seem to either hold their own or win. The lack of the corrector plate and the traditional focuser and non-moving primary is a big draw but the simplicity of the tried and tested SCT design seems to win out.

 

That is the consensus, and I read those threads before buying the VMC.  I know the 125C isn't the same design as the VMC, but in my SxS tests between the Kenko & a white-tube C5 spotter, the Corrected D-K performed more like a refractor on planets & double stars than the SCT, and that's why I decided to give the VMC a try.  Gotta give some kudos to Vixen for attempting an SCT challenger.  But collimation is trickier to me than with an SCT, and as critical to best performance -- maybe even more so.  As I posted earlier, the wobble in the focus tube was tiny, but caused big shifts in the laser that I no doubt saw during the first session.

 

However, the c. 1976 orange C5 Astro that I own now would probably match / beat the Kenko 125C on most object types.


Edited by Bomber Bob, 18 September 2018 - 02:47 PM.

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#94 Nippon

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Posted 18 September 2018 - 07:58 PM

I had a VMC 200 and a C8 XLT at the same time and while the VMC was properly collimated and showed a very good star test the C8 was better on planets. I figured the reason was the VMC's larger central obstruction and the thick spider vanes. However every once in a while it seemed the VMC would equal the C8 on planets so I began to suspect the VMC is prone to tube currents since the tube is only about an inch larger than the primary.


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#95 Bomber Bob

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Posted 18 September 2018 - 08:40 PM

I began to suspect the VMC is prone to tube currents since the tube is only about an inch larger than the primary.

 

I wonder...  I started with the waxing crescent Moon right at sundown, and moved to Saturn about a half hour later, and the first cool-down probably was in progress.  Got to Mars probably an hour after sunset.  I attributed the great views to Mars' position near the meridian, but the air inside the tube was probably stabler by then.  My Edmund 4" Cass is in a 5.5" tube, and the primary cell is steel -- it's not plagued with tube currents.  I figured the VMC would be like it, only double the size, but its cell is solid, whereas the Edmund's has 4 small ventilation holes around the edge.

 

But SCTs are sealed, so wouldn't the VMC adjust faster, and be less likely to have currents?


Edited by Bomber Bob, 18 September 2018 - 08:40 PM.

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#96 Exnihilo

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Posted 18 September 2018 - 08:59 PM

I began to suspect the VMC is prone to tube currents since the tube is only about an inch larger than the primary.
 
I wonder...  I started with the waxing crescent Moon right at sundown, and moved to Saturn about a half hour later, and the first cool-down probably was in progress.  Got to Mars probably an hour after sunset.  I attributed the great views to Mars' position near the meridian, but the air inside the tube was probably stabler by then.  My Edmund 4" Cass is in a 5.5" tube, and the primary cell is steel -- it's not plagued with tube currents.  I figured the VMC would be like it, only double the size, but its cell is solid, whereas the Edmund's has 4 small ventilation holes around the edge.
 
But SCTs are sealed, so wouldn't the VMC adjust faster, and be less likely to have currents?

Did you defocus and look at the diffraction pattern? Might try that next time.

#97 Bomber Bob

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Posted 18 September 2018 - 09:10 PM

I did star tests on Arcturus & Altair, straight-through / no diagonal, and got 3-rings.  Inside focus was more symmetrical than outside, but very much improved compared to the first session -- where I left collimation at close enough.  Before the second session, I got the alignment as precise as my laser device measures.  I've seen "comet" stars in my other Casses when collimation is even slightly off.  Stars were very close to pinpoints at focus -- VMC split my favorite Delphinus Doubles beautifully.

 

I have a DSO camera now; when it gets cool enough at night, I'll make some star test images and post them, rather than try & describe what I see.


Edited by Bomber Bob, 18 September 2018 - 09:15 PM.

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#98 Bomber Bob

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Posted 22 September 2018 - 12:14 PM

VMC200L on TAK EM-1S + Filotecnica surveyor tripod:

 

VMC200L S03- EM-1S Mount.jpg VMC200L S05- EM-1S Mount.jpg VMC200L S07- EM-1S Mount.jpg


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#99 Paul Sweeney

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Posted 23 September 2018 - 01:25 PM

Hi Bob,

 

I have the VC200L, which is similar in build. It will cool faster than an SC, which may not always be an advantage. The SC, being a closed system, cools slowly, minimising tube currents but taking longer to cool. The VC200L cools quicker, but the cooling causes tube currents. The mirror cell doesn't help, because it traps warm air behind it. When you cool it aim it straight up. The mirror will cool evenly that way. If you put your hand over the opening, you can feel the warm air rising. Do not cool it on it's side or at an angle. The warm air behind the mirror will rise, keeping the top part of the primary warm while the bottom cools. This will give you all sorts of image issues, which gradually disappear as the mirror stabilizes. Even after hours outside, I still get occasional tube currents if the temperature starts dropping. That is the price for having a dew-proof telescope.


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#100 Bomber Bob

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Posted 29 September 2018 - 10:15 PM

Vixen Slug Out:  VMC200L versus FL80S

 

Temperature  75°F (24°C)

Humidity 94%
Wind Speed Calm
Dewpoint 73°F (23°C)

Seeing:  5 - 7 variable (river smog / haze / mid-level thin stripe clouds)

 

Two sweaty hours of fantastic views, and not one complaint with either Vixen.  Saturn & Mars:  Both were much much brighter in the VMC, but sharper in the APO, at the same magnifications.  Saturn was painfully close to the light pollution dome, which limited magnification to 200x.  Mars at the meridian took 300x from the APO, and 400x from the VMC.  Its markings are still muted compared to its last appearance, but at this point in the season, I was thrilled to see anything.  I didn't find the VMC's vanes distracting with either planet.

 

DSOs:  Both scopes wowed me.  I found M57 at 1920CT (0020Z) in both at about 30x.  I observed double stars near the zenith until the skies got darker.  In every field, the VMC's 8" mirror showed multitudes of faint stars that eluded the 80mm fluorite, but it's individual stars were microscopic compared to the VMC's pinpoints.  The Dumbbell is huge in the VMC, and several stars peek through the fringes; whereas the nebula isn't large enough to see this in the APO.  From Aquila to Cygnus, the VMC revealed so many faint clusters that I lost count.  It's like having a compact Newtonian with a refractor focus position -- best of both types.

 

The tube rings let me rotate the scope to put the finder in the most comfortable positions, and balance the load -- I also trust rings over dovetails -- my heavy 4" Jaegers RFT broke loose from its dovetail clamp one night, and smacked my knee before it hit the ground.  So I prefer metal rings bolted to the mount.  Functionally, my VMC rig is almost as easy to use as my APO.  It's heavier, of course, but I moved both from the north edge of the yard to the center without injury.


Edited by Bomber Bob, 29 September 2018 - 10:15 PM.

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