Orion VX120
Gary Harwell
Dustin Smith
model, or just a simple achromat? If it's an achromat, I would opt for
the Vixen 102 line of scopes, preferrably the flourite model. They also
carry an ED model of the same scope for a few hundred bucks less.
-Dustin
William Rison
Look at Vixen's web page http://www.vixen.co.jp/english/index_e.htm and
click on
New Astronomical Telescopes to see there new line of NA and ED refractors.
When I inquired Vixen about purchasing one of there new ED refractors
because Orion
does not carry them they sent me the following email.
Attn : Mr. William Rison
Thank you very much for your interest in our new ED refractors. We
understand fully
that you are unhappy with Orion's incomplete offerings of Vixen
products.
We are now requesting Orion to commence dealing in the new line of Vixen
refractors
including ED, and we hope you will be able to get information on pricing
for these from
Orion in the very near future. Thank you for your patience for a while
in this matter.
Best regards,
T. Kawai, Sales Dept.
Vixen Optical Industries Ltd.
William Rison
Bill McHale
: I don't have much knowledge of this scope, but is it a Flourite or ED
: model, or just a simple achromat? If it's an achromat, I would opt for
: the Vixen 102 line of scopes, preferrably the flourite model. They also
: carry an ED model of the same scope for a few hundred bucks less.
Well the VX120 is an achromat, but not a simple one. Instead of the normal
two element, 1 group objective in a normal achromat it has a 4 element, 2
group objective. The first group acts like a long focus refractor and the
second element serves to shrink the Focal Length and to flatten the field
of view. As a result the VX120 gives far better performance than an
traditional achromat its size and focal length could ever hope to give.
I own one and I am very pleased with it. It gives a large field of view
and tolerably little chromatic abberation. I would certainly recommend it
to a friend. I would however be interested to see how it compares to the
Vixen's new 114mm ED.
--
Bill
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Gary Harwell
the construction of the VX-120. I'm looking for someone who has one and can
give me an actual evaluation based upon use. Thanks, and clear skies.
Dustin Smith wrote:
> I don't have much knowledge of this scope, but is it a Flourite or ED
> model, or just a simple achromat? If it's an achromat, I would opt for
> the Vixen 102 line of scopes, preferrably the flourite model. They also
> carry an ED model of the same scope for a few hundred bucks less.
>
> -Dustin
Gary Harwell
Bill McHale wrote:
> Dustin Smith (dus...@airnet.net) wrote:
> :I own one and I am very pleased with it. It gives a large field of view
Gary Harwell
talked to them about ordering directly. I'm looking for someone who has a
VX-120 and can tell me how good it really is in the field. Thanks, and clear
skies. Gary
William Rison wrote:
RAnder3127
>Well the VX120 is an achromat, but not a simple one. Instead of the normal
>two element, 1 group objective in a normal achromat it has a 4 element, 2
>group objective. The first group acts like a long focus refractor and the
>second element serves to shrink the Focal Length and to flatten the field
>of view. As a result the VX120 gives far better performance than an
>traditional achromat its size and focal length could ever hope to give.
How is the diffraction image and detail shown on planets?
Is the colour apparent on the Moon?
-Rich
Death to Divx; Long Live DVD!
"If Tandy (Radio Shack) or Blockbuster
(who censor videos) adopt Divx, please
boycott them. Divx is Evil incarnate."
Bill McHale
this scope and I seem to be the only one posting on this thread who
actually owns one (If I am wrong, I would love to compare notes) I guess I
will write a little review for the scope.
Overview of the system:
The VX120 is what what Vixen has dubbed a Neo Achromat. Essentially this
means that instead of containing two lenses the scope contains 4 lenses
with two lenses at the front of the scope and an additional 2 approximatly
2/3-3/4 of the way back to the eyepiece. The design appears similar to if
not identical to a Petzval with the second lens grouping serving to shorten
the focal length of the system and to flatten the field, in addition the
scope has much less chromatic aberation than a 2 lens achromat of the same
focal length. The final focal length is 800mm or f/6.7 and the scope is
approx. 1 meter long.
Just a thought, but I think this scope is similar to design and execution
to the original Tele Vue Renissance but with a slightly larger F/ratio.
Star Test:
Viewing bright stars at relatively high power (213x) revealed near text
book images in focus with just a hint of under correction revealed in the
out focus images.
Chromatic Aberation:
It must be remembered that this scope is an Achromat and does not garuntee
APO like performance. On 1st magnitude or brighter stars and on Mars and
Venus (the only planets I have had a chance to really look at with the
scope so far) there is noticable Chromatic abberation, but it is not so bad
as to make the image displeasing. I have compared this scope to a 4", F/10
Jager Achromat and a Meade 90mm and I believe the chromatic correction to
be slightly better than either of those scopes despite having a shorter
focal length. Color Filters allow the most to be milked out of this scope,
and with them I was able to see as much on Mars as I was through a Friend's
AP Traveler.
Just a note but on dimmer stars and nebulas no chromatic abberation can be
seen. Alberio appears a text book blue and gold in this scope with no
fringe color at all.
Other performance:
The system has a wonderfully wide field of view. With a 1.25" 40mm Plossl
more than 2 degrees of sky are visible and the stars remain pin-points
until very near the edge of the field (And I suspect that is an EP
limitation not a problem with the scope). I am currently trying to work a
2" visual back, diagonal and 35mm Panoptic into my budget, I expect the
scope will not disappoint.
The scope also cools relatively quickly; usually being ready to view within
15min of being set up.
Now for a few nitpicks.
1. Orion should not be selling this scope with a GP mount. I ordered mine
with a GP-DX and am very glad I did. I have heard one person with the GP
say that the scope was near the limits of usability on the lighter mount.
2. The focuser is a little stiff. At low magnifications this is not a
problem but at greater than about 150X it induces enough vibration into the
system to make it difficult to obtain a precise focus. I am going to try
plaing around with the focuser plate, the tripod and the counterweights to
see if I can get it to be a bit more stable.
3. The scope should come with a 2" visual back and not a 1.25". I can't
even imagine it saves Orion or Vixen any money though perhaps it results in
sales of the 2" back.
Overall assesment:
This scope, as many of Vixen's scopes represents a very good comprimise of
value and quality. Priced considerably less than a scope like the Traveler
or the FS-102, it matches those APOs in most performance areas for anywhere
from $600-$1200 less. This scope does lag slightly behind those scopes
because of chromatic abberation particularly on planetary work, and also
slightly on mechanical quality (see the nitpick about the focuser above).
The main difficulty this scope will have is finding a proper market for it.
If bought seperately (to get the GP-DX) the scope, mount and dual-axis
drive cost approx. $2800. If you need to get a Diagonal and ep's the cost
can climb over $3000 without much effort. That will buy you a big
reflector and is close to the cost of the Premium 4" APOs with mounts and
is in the same range as the VX102GP-Flourite with drives and eye pieces.
The market seems to be people like myself who want a very good and portable
refractor but can't quite currently make the investment that the APOs
require. I like this scope very much, and if your situation is similar to
mine I would recommend the scope without reservation. If however you can
stretch just a bit farther I would recommend stepping up to the Traveler or
the TV-101. I would only recommend the Takahashi or the Vixen scopes if
you were not as interested in wide fields of view, though for planetary
work either would be an excellent choice.
Another alternative that also intrigues me is Vixen's new 114mm ED scope.
I would be interested to see how a semi-apo like that can compare to an
Achromat that is just slightly larger.
Let me see if I can put this in perspective by numerical comparison with
the Traveler and Takahashi FS-102. Note all the numbers assume a Refractor
of between 4" and 5".
Scope: VX120 Traveler FS-102
Chromatic abberation: 7 10 9.75
Spherical abberation: 9 10 10
Field of View: 8 9 7.75
Construction Quality: 8 9.5 10
Size: 7 10 7.5
Focuser: 6 9 10
Planetary Performance: 7.5 8.5 9
Deep Sky: 8.5 8.5 8
Price (OTA only): $1300 $2400 $2000
Mind you everything but price is based off of my subjective experience, and
I have had more experience with the Traveler than with the FS-102 so some
of my assesment there could be due to familarity with the Traveler.
Hope this is helpful for people.
Reid Williams
Bill McHale wrote in message <7n2ddt$etv$1...@news.umbc.edu>...
>
>2. The focuser is a little stiff. At low magnifications this is not a
>problem but at greater than about 150X it induces enough vibration into the
>system to make it difficult to obtain a precise focus. I am going to try
>plaing around with the focuser plate, the tripod and the counterweights to
>see if I can get it to be a bit more stable.
>
Bill,
My Vixen 90 has allen screws on top of the focuser that can adjust the
tension and "slop". Two are located forward of the focus lock, and one is
located aft. I don't think the focuser plate will help much....if you do
remove the focuser plate, watch for small washers that may fall in the tube
and put the rear elements in danger of debris.
Reid
Gary Harwell
RAnder3127
> The design appears similar to if
>not identical to a Petzval with the second lens grouping serving to shorten
>the focal length of the system and to flatten the field, in addition the
>scope has much less chromatic aberation than a 2 lens achromat of the same
>focal length.
I keep hearing this but what does it mean in percentages?
Are there any other aberrations present that would make
someone go to a fluorite instead?
-Rich
"The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all progress
depends on the unreasonable man.
-George Bernard Shaw
Bill McHale
: In article <7n2ddt$etv$1...@news.umbc.edu>, wmc...@umbc.edu (Bill McHale) writes:
: > The design appears similar to if
: >not identical to a Petzval with the second lens grouping serving to shorten
: >the focal length of the system and to flatten the field, in addition the
: >scope has much less chromatic aberation than a 2 lens achromat of the same
: >focal length.
: I keep hearing this but what does it mean in percentages?
: Are there any other aberrations present that would make
: someone go to a fluorite instead?
The only real thing is Chromatic abberation and how much you are willing to
tolerate. That and the fact that the tube is a fair bit longer than the
focal length suggests.
Personally I think that visually it matches a Flourite scope of between
84-87% of its size (i.e. the TV-101, Tak FS-102, AP-Traveler, and VX102
Flourite) except for the chromatic abberation. If I were to buy a flourite
in that size range it would be for other reasons such as superior
mechanical quality, or wider fields of view (i.e. the TV-101 or the
Traveler).
As for percentages.. well I am really not sure I am qualified to put a hard
number on the Chromatic Abberation compared to other scopes. Like I said
it appeared as good or better than 90 and 102mm achromats of a longer focal
length but it was definitely noticable. To get any more precise than that
will require a much more skilled observer than I.
As for other aberations. I did not notice any at the eye piece and
considering the scope is designed as much for photography as visual use I
suspect that it will be true across at least a 35mm field at prime focus.
If you lived in or near Maryland I would be more than glad to let you have
a look through the scope and judge these things for yourself.
lin...@vega.rice.edu
wrote:
>Thanks for your reply. I've had a chance to look at Vixen's web site and I have
>talked to them about ordering directly. I'm looking for someone who has a
>VX-120 and can tell me how good it really is in the field. Thanks, and clear
>skies. Gary
>
Gary - I received my VX120 a week ago, but have had clouds (of
course!). Monday night cleared for an hour or so, and I got to look
at stars and the moon. As Bill reports, the star test was quite good.
I use the scope on a Meade LXD-650, mounted with a Losmandy dovetail
system. All my scopes have dovetail blocks so they easily slide onto
the mount. This makes it easier to do comparisons.
I have a Tak FCT-76 and a TV-101. The VX120 shows color on the moon,
but it's not bad, and the sharpness is excellent. It easily
outperforms the Tak fluorite triplet because of the aperture
difference, but the Tele Vue holds its own pretty well, with no color
visible.
I used a 5mm Tak LE, 4 Radian, 3 Radian, and 2.5 LV. The Lanthanum
shows a little color on the APOs, and adds a little more color to the
VX120. The Radians and Taks are outstanding lunar/planetary EPs.
If we ever get a stretch of clear weather, I'll try to report more
details. In the meantime I believe the VX120 is a real bargain at its
present sale price, and do not regret the purchase at all.
Clear Skies to All!
- Steve -
(remove "vega" for email)