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Tele Vue Focusmate
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Focusing on the Focusmate™
I've recently acquired a new 127mm (5-inch) Tele Vue NP127 f/5.2 apochromatic
refractor. It has the
Focusmate™ dual-speed focuser adapter which was announced in April 2005 and is now available through
Tele Vue dealers. For the reader who is unfamiliar, the Focusmate is an add-on accessory exclusively for
Tele Vue refractor.
NP127 with Focusmate
As some of you may know, I've expressed my personal opinion from time-to-time
on the need for a fine-grain
focuser for APO refractor with fast f/ratio. The reason is at f/5, f/5.2, f/5.4 or f/6, the depth of focus is very
shallow and precise focus is more difficult, albeit still accomplishable with a single-speed focuser.
record, I've owned and used a 2"
FeatherTouch focuser with brake (the complete focuser version
adapter) frequently for five months on a triplet APO with and without my BinoVue. So I have a pretty good idea
on what the FeatherTouch can do. Up until then, I've not used any focuser that is better than the FeatherTouch
(with the exception of the MoonLite because I haven't even seen one in person yet). While its coarse focuser was
a little stiff, the FeatherTouch fine focuser worked very smooth, flawlessly and very well and in my opinion, it was
the finest dual-speed focuser on the planet. The FeatherTouch can also be added on Tele Vue refractors. I also
had some experience with using the dual-speed JMI DX-1 focuser which I did not like very much. So now I have
a metric to compare the Focusmate with.
My dealer, Skies Unlimited, offered their service to install
the Focusmate for me because
one of the owner have
known the mechanically inept me to screw up with my screwdriver. But since the fabrication of my NP127
coincided with the time that the production Focusmate became available, my dealer arranged for Tele Vue to
installed it for me. Thus, my new NP127 came with the Focusmate pre-installed at the factory which is not (I
repeat not) a normal service offered by Tele Vue. Just serendipitous timing! Although it was pre-installed, the
instruction for installing the Focusmate was included. I read the instruction at any rate and it appears to be easy to
follow as the instruction sheet also include 8 photos to serve as guide. I actually followed the instructions with my
own "virtual installation" with a "stunning success"!
focuser knob has a rubberized grip just like the
original knob while the fine
focuser knob do not. The
FeatherTouch does not have any rubberized grip at all. As added bonus, the Focusmate can be installed for left-
handed observer as well - a clear benefit for the left-handed person. Use appropriate screwdriver! Beware
that some users have reported stripped screw when removing the original 5-hole knob as the screw is tight; so
please read the instructions which also highlighted this caution.
Clyde (another owner of the
Focusmate on his TV-85) informed me that it was very easy for him to install
Focusmate. In fact, since he uses his TV-85 for birding function, he removes the Focusmate and re-installs it
whenever he switches from astro to bird, seemingly as easily as slipping on and taking off a pair of gloves!
While waiting for the first light of my NP127, I "played with", "rotated" and "spinned"
the Focusmate a lot that
afternoon, turning the coarse focuser back and forth, "working" the finer focuser, repetitively. There was no
binding, no stickiness,. no bumpiness whatsoever in the coarse or fine focusing mechanism. No unevenness
nor rough feel whatsoever in actual use. No backslash that I could tell.
So, how well does the Focusmate work under the stars? Well, I'll be the first
to confess that I had
reservation when I read the details of the Focusmate after Tele Vue's announcement. Being mechanically inept,
I cynically thought, surely it didn't look like it could work as good or better than the FeatherTouch, I speculated.
In fact, I further confess that I had already trumped up a contingency plan to "pawn" the Focusmate if I were to
be ever so slightly displeased with it and would have ordered the FeatherTouch Micro. Starlight Instruments
was very kind in providing answers to my questions. This is because I'll not accept a sub-par, sub-functional
dual-speed focuser for my top-performing NP127 period! As the old saying goes, "looks can be deceiving."
very happy to pronounce that the Focusmate is
an unexpected surprise.
It works as advertised!!!
Very smooth and with a larger, more grippable knob than the FeatherTouch giving a slight edge to handling
comfort! The coarse focuser works less stiffly than the FeatherTouch coarse focuser. The fine focusing
functions as capable as the FeatherTouch fine focusing but with a more comfortable larger knob as noted. The
feel of the movement I get is different of course due to the difference in the design approach. In addition, I had
thought the 6:1 ratio of the Focusmate vs the 10:1 ratio of the FeatherTouch would make a very noticeable
difference. I'm also happy to report that in actual use under the stars, I could not tell the difference in the result!
The Focusmate's ratio changes the focus ever so slightly and visually indistinquishable from the FeatherTouch
ratio. It is perhaps because the Focusmate fine focusing knob is larger than the FeatherTouch fine focuser knob
which conforms to the principle of physics that the larger the radius of the knob the less circumferential distance
it has to turn to achieve equal movement. Later, I learned from talking to Tele Vue that the Focusmate's accuracy
is 0.00005 inch! Good heavens that's much thinner than the thickness of my hair (human hair average thickness
is between 0.02mm - 0.12mm)!!! The actual movement can be seen on the Tele Vue TV-60is digital's readout!
One other fine point. The left-side original focuser knob can still be used in the original R&P mode. Notice also
that Takahashi MicroEdge dual-speed focuser adapter also use a large fine focuser knob.
When performing webcam imaging, precise focus is very
important and in my opinion much more so than visual
observation. If the image is out of focus, no matter how much image processing you do, you'll not be able to
get sharp focus as you would have if the focus was dead-on to begin with! I have been using a focus lever to
assist in getting exact focus for video capture with my TV-102. The Focusmate on my NP127 eliminates the
need for the focus lever and in actual use with webcam video capture software, it was easier to obtain precise
focus than the focus lever. Also, the 6:1 ratio is much more than adequate to achieve precise focus. I believe
again the large knob of the Focusmate fine focuser is responsible for the precise handling.
The Focusmate has no slippage even when pointing straight upward
at the zenith without the need to tighten the
tension screw; this was with my heavy 6mm Radian eyepiece and 2" Everbrite diagonal. Note the new Tele
Vue's refinement (in my NP127) with two tension screw for holding heaving accessories such as binoviewer,
CCD camera, etc..
The Moon through the NP127 and Tele Vue BinoVue binoviewer at RTMC was the fateful
event that led me to
my NP127 and BinoVue today. As such I had high expectation of the Focusmate; it better works flawlessly
with the BinoVue or else! One of the largest magnitude of trepidation I had before acquiring the Focusmate was
how well will it work under the load of BinoVue/2X (1.65 lbs) and a couple of 12mm Radians (2.53 lbs), not to
mention my 2-inch Tele Vue Everbrite diagonal already attached. BTW being obsessively weight conscious, I
chose the BinoVue because it is one of the lightest high-end binoviewer on the market today. The triplet APO
with a unique drawtube design and FeatherTouch I used to own, handled this setup very well. To "stack the
cards" against the Focusmate even more, I intentionally did not balance the OTA. The Moon was riding at 35º
above horizon. Well, what do you know; the Focusmate worked flawlessly! Yes, the coarse focuser motion
was slightly stiffer than the cyclop viewing but so was the FeatherTouch. The fine focuser motion of the
Focusmate was only slightly more stiffish than cyclop mode but so too was the FeatherTouch fine focuser.
Amazingly, the two tension screw on my NP127 did not even have to be tightened . The Focusmate really pays
off big time viewing the Moon especially when the seeing is below average because it forces me to focus often.
NP127 with Focusmate and BinoVue
Moving to near the zenith, this is
a tough test for any focuser. Just to give you an idea, I had to tighten
screw on my Tele Vue TV-102 R&P focuser quite a bit to prevent the focuser from creeping downward with the
BinoVue attached. This made focusing with the binoviewer unpleasant. The Focusmate stayed put without even
tightening the two tension screws! Amazing; whereas I always had to tighten the tension screw (braking screw) on
the FeatherTouch just a wee bit so the focuser won't slip when used near the zenith. How was the motion?
Well, the coarse focuser is a wee more stiff than when it was pointed at the Moon but the FeatherTouch coarse
focuser was stiffer. The fine focuser of the Focusmate is also a wee more stiff than when pointed at the Moon but
the motion has similar smoothness and resistance as the FeatherTouch fine focuser! However, the larger knob of
the Focusmate fine focuser was a welcome design. Amazing from an adapter! Using gravity helps in either case
(i.e. focus upward just beyond focus and focus back down again to attain focus). In my opinion, both Focusmate
and FeatherTouch function equally well and surprisingly similar, with the load of BinoVue and a couple of eye-
pieces near the zenith.
Since my NP127 is being used on a relative light GEM, the Vixen
Super Polaris, I was afraid that touching the
Focusmate would cause excessive vibration. I'm very relieved to find that my fear did not materialize. The image
settled down in about one second, usually less. I attribute this to a combination of excellent handling of the NP127
and well thought out design of the Focusmate. My slightly heavier triplet APO I used to own was also stable but
I recalled it took a tad longer for the vibration to settle down due to its heavier weight. A word or two about
vibration with my Vixen Super Polaris mount with my BinoVue setup. When using the fine focuser, the maximum
amount of vibration lasted only about two sec. (remember I did not balanced the tube), sometimes less which is
remarkable! I think the vibration will be cut back when I balance the OTA.
eeny, meeny, miney, more, which is the NP127 hiding on the floor?
I will also add that I had some anxiety on how the Focusmate on
the NP127 would fit in the already very small
hardcase, which is the same size case as my 4-inch Tele Vue TV-102! Now that I own the NP127, I must
compliment on Tele Vue's ingenuity. Here's how my NP127 with Focusmate slumber in its hardcase and note
how well the Tele Vue Starbeam finder fit in as well. Talking about maximizing the use of available space!
The only one single "flaw" I could find in the
Focusmate was the "look".
Although beauty is in the eye of
beholder, I'll admit the FeatherTouch (and I'm referring to the model with complete focuser housing) look
esthetically "better" and the Focusmate won't win any beauty contest. To me, the Focusmate does have a
"more naked", "wildly feral" "look" if you will and I can't help but slowly succumbed with admiration of its shiny,
exposed "muscular" stainless steel cylinder that seem to go well and match well with the existing focuser knob
and unmistakably convey the Tele Vue "look-and-feel" with the Tele Vue logo. One other knit-picking. The
fine focusing knob can probably use a rubberized grip like the coarse focuser for our observers of the great
cold glacial north, which has already been pointed by several owners of the FeatherTouch as well. The last
macro-knit-pick is that you should be aware how the Focusmate will "sleep" in your case as you will most
likely have to cut some foam yourself. Wrapping up on the "look" issue, after several nights of actual use under
the stars, I realized that the "look" factor dissipated in the dark, cool night (hard to see the focuser anyway)
because I spent 100% of my time scrutinizing on the view and trying to get those teeny Lunar and Mars features
into sharp focus where the Focusmate assisted unintrusively.
Before I close my report, I'd like to confess that I went to
the Astrophysics web site to look at the new triplet
air-spaced AP160 when it was announced, another true jewel of an APO refractor as well (and who doesn't)!
Lo and behold, I noticed that the AP160 comes with the standard R&P AP focuser instead of the FeatherTouch
which caused me great puzzlement. Why would AP do this? After prosing the question on the AP user group, it
was explained that in all likelihood the buyer of the telescope would want to upgrade to some other focuser for
imaging and the popular choice is electric/electronic focuser. Thus, why unnecessarily add more weight and
cost to the product. It sounded logical and being exclusively visual observer at the time I hadn't thought deeply
about it . But now that the new wild imaging B[ee] has emerged, it finally dawned on me that the AP's rationale
made a lot of sense! Now I also see more clearly why Tele Vue continue to equipped their fine APO refractors
with the simple but effective R&P focuser. And perhaps someday, I may get one of the new fangled,
microprocessor controlled electronic focuser for some future SBIG CCD camera. It also occurred to me that
I still have the left-hand knob on the NP127 to possibly installed an electronic focuser on it.
In conclusion, I feel that in my opinion, the Focusmate work
just as well as the FeatherTouch and surprisingly
exceeded my wildest cynical skeptism, although its look won't win the hearts of some people! I can heartily
recommend the Focusmate to the Tele Vue refractor owners wanting functional dual-speed focuser that is
genuine Tele Vue. If you have any problem during installation, Tele Vue's renowned service stands ready to
assist you between 8am- 5pm ET (just don't do weekend installation). Oh, and please don't be shy; be bold
and ask your dealer if they'll install the Focusmate for you when you order your new Tele Vue APO refractor!
Finally please do not get the wrong idea. I'll conclude by clarifying that the Focusmate and the FeatherTouch
are functionally two of the finest dual-speed focusers to be employed in high-end APO refractors today and
I feel fortunate to have the pleasure of using both so satisfyingly.
I went to Tele Vue's booth at a telescope event sponsored by Oceanside Photo and Telescope (OPT) and was
able to "play" with the TV-60is' micrometer (which is made in Switzerland for the renowned precision) and the
Focusmate. Sure enough, I could move the Focusmate at 0.00005 inch increment (note the smaller last numeral
"5" in the digital display!) Very precisely satisfying to see the real-time feedback of the movement of the
Focusmate fine focusing knob.
TV-60is Micrometer and Focusmate (not shown in picture)
In addition, there was a flow of people passing thru all
day. Many people came by to "imbibe" the Tele
refractors; the NP-101 and the NP127 had the Focusmate on them. Most people commented how well the
Focusmate focuses and (note this) many people expressed how good the Focusmate look (especially on the
shiny stainless-steel cylinder) with a few asking whether they can buy it for their non-Tele Vue telescope! Al
Nagler did explain that it was not possible because the Focusmate is designed to precisely fit Tele Vue's focuser
shaft. I was attentively listening and there was not a single negative comment on the Focusmate that I was able
to hear. (Oh and yes, there was another manufacturer with the FeatherTouch focuser - the complete version, at
a nearby booth also. In addition, the Takahashi booth has the dual-speed MicroEdge focusing adapter installed
on the new 6-inch TOA150 APO refractor.)
Please be aware that if you decide to install a third-party focuser on your Tele Vue refractor that is still under
warrantee (Tele Vue refractor comes with a 5-year warrantee), your choice will void the warrantee. If you need
more information regarding warrantee, I suggest calling Tele Vue.