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by Oldfield So 12/31/05 | Email Author

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A Complete Review of the Tele Vue Ranger

A Complete Review of the Tele Vue Ranger


Background information
Tele Vue Ranger has been one of the modern classic for telescopes, but as anything will be, it has been discontinued with the advancement of technology.

So, why am I reviewing a discontinued product? I don't exactly know, but I keep on discovering new aspects of my beloved Ranger, and I believe that the ideas presented here will also apply for any high quality compact portable refractors. Therefore, I don't think it's completely meaningless.
I have owned my Ranger for over 8 years, and it has been in active use from day one of the ownership. I bought it new from Orion Telescope and Binoculars Center.

During all these years, my observation habbit changed quite a lot but the Ranger keeps a very important position in my hobby. When I first acquired it, I usually observe with my friends during camping, and so a really portable wide field scope was what I needed. And then I began to move on with a larger aperture scope, and again the Ranger augment it very well. Then I wanted a guidescope when I do imaging, it also works amazingly. Finally when now I had to stay at home due to my children, it serves as a wonderful solar telescope (with proper solar filter system) extremely work, too. It is really a very very versatile piece of equipment.

Not only for the 8 years of ownership, but also from the experience to use my Ranger in different situations, it's no first night experience, brief impression or unmatured conclusion that I'm going to make, here we go!

Introduction


The Tele Vue Ranger is a 70mm f/6.8 ED achromat, featuring 480mm focal length. It is very short and you can put it fully inside a medium sized backpack, and the mechanical construction is superb so that I never worry to put it inside my backpack together with my tripod, even without any padding. It is 3.5 lb in weight and thus any mount, or even better photo tripods, can hold it without any problem.

Ranger is a downsized version of Pronto, the weight reduction is a result of the 1.25" helical focuser instead of the 2" rack and pinion, the removal of the sliding dew shield, and the replacement of a simple dovetail mounting plate instead of a tube ring. Such an arrangement reduces the weight nearly by half.

The optical quality of the Ranger is considered to be excellent at its own age, it was selected as a scope for birding in "Better View Desired". Of course, it is not a true apochromat and it exhibits quite a lot of chromatic abberation if you are experienced enough to find it out, but it is not exceeding annoying at least, for most targets in the sky.

Semi-technical detail




A close look at the lens of the Ranger

The objective lens: It is an ED doublet, the coating is applied very nicely and it appears as a deep purple color film. If you view directly into the OTA, somehow the lens disappear virtually, so you see how effective is the coating.

The doublet is held in a cell, and it is not user adjustable and it means that you cannot collimate it yourself easily. The lens cell has 77mm thread for the attachment of an optional flexible rubber dew shield, and/or any other aperture filter. I've that rubber dew shield but it is not very effective and I found that a 1.25l soft drink bottle works out surprising good and it fits very securely too.

A metal retaining ring was used to fix the doublet inside the cell, and if you are brave enough, you can remove it to clean the lens and to have any adjustment yourself. However, it's not recommended and it might void your warranty, if you still have.

On removing the retaining ring, you will find another metal ring lies between the retaining ring and the doublet, I guess it is to prevent the retaining ring from scratching the doublet when it's being screwed in/out.

The doublet sit very tightly inside, and I believe it's good for the maintenance of good collimation. But at the same time, it's not too tight to introduce pinched optics.

Local amateur always said if you love your telescope enough, you will disassemble it sometimes to clean it, to re-adjust everything yourself eventually. We have such a culture since we are from Hong Kong, usually far away from the manufacturers of our equipments, and thus it is natural for us to do the maintenance ourselves.

After years of usage, my Ranger has some patches of dew and/or dirt on the inner surface of the lens, and thus I have to clean it myself instead of to ship it across the Pacific Ocean to have it cleaned by the manufacturer. Of course, unless if one day Tele Vue offers a new lens upgrade for my Ranger, or else I won't probably ship it back to US.

The telescope tube: The tube is quite simple but it is extremely robust. The lens cell was fixed to the OTA, and you cannot remove it easily, at least up to this moment, I still cannot remove it.

The evergreen finish is superb, I fail to create any major scratch on the tube surface even I routinely put my Ranger with the tripod inside a backpack for traveling. Inside the OTA, you find no baffle but instead, it has some dull black paper inside, something like sand paper. It effectively enhances the contrast without having to increase the overall weight with conventional baffling system.

Having said that, you would still know the moon is just outside the field of view when you point the OTA near enough but not exactly pointing at the moon, that means there is still room for improvement.



The rear end of the Ranger, the focuser, and the dovetail bar

The focuser: the focuser consists of a sliding draw tube which can be fixed with a set screw. Such a draw tube can effectively extend the focusing range of the instrument. I found it great to use since you can rapidly come to a rough focus, and then fine tune it using the helical focuser.

However, if you use the Ranger with a heavy camera, the sliding draw tube can be quite bad to use since you can hardly adjust it without introducing excessive vibration to the whole system. Having said that, it works quite well even with a binoviewer.

For those who were used to rack and pinion focuser, might find the helical one hard to use, however, I found it not a problem. The feeling can be best described by cutting a piece of butter with a heated sharp knife, extremely smooth and predictable. You can start and stop at any point, with no noticeable backlash.

Over all the years, the helical focuser can become quite sticky. Another local folk who owned a Ranger also said the same. So, I disassembled it for cleaning and re-greasing. To disassemble the helical focuser, you losen the small allen screws on the focuser end which is a retaining ring indeed, afterward, you can turn the retaining ring and it will go off. By then, you can take the whole thing apart and do the cleaning and re-greasing.



The focuser disassembled

At the end of the focuser, we have two set screws to fix anything like a diagonal. These screws are not captive and I have actually lost one before. So, be careful. These screws are nylon and won't leave any mark on a metalic barrel.

One should note that the Ranger will not come to focus without a diagonal or an extension tube.

The sliding dovetail mounting bar: Instead of a tube ring (or clamshell), the Ranger employs a small dovetail plate for mounting. Several 1/4" threaded holes are tapped so that you can mount it on any camera tripod.

That small dovetail can slide forward and backward with a very generous range, so that you can balance the OTA easily. The dovetail is extremely well made so that there's zero room for vibration of any kind. The dovetail is fixed via a set screw and it's very effective to hold it firmly in place.

Use Cases


As a rich field instrument: This is why I bought my Ranger when I was an absolute beginner. I remember at that time, I found it hard even to align the finderscope with my C90. And small aperture scopes are really limited to brighter and larger objects, so I don't mind giving up 20mm worth of aperuture and moved to a Ranger. In my by then beginner eyes, I found the Ranger more contrasty than the C90 and it also delivers brighter views!!! Believe it or not.

With a 32mm Plossl, the Ranger yields 3.3 degree field which is large enough to encapulate the whole belt of the Orion. With a large field of view, you don't really need a finder and you can easily scan around to find the object you wanted. It's so easy. That C90 keeps frustrate me but I ended up observing far more after I acquired my Ranger. This is the scope which helps me to grow up and got fully addicted in astronomy.

3 degree plus field is enough, but adding a zero power finder will speed up your searching and thus I have added a Rigel Quick Finder to my Ranger.

When compare a large aperture instrument to a small one, there's only a few thing which a smaller instrument can win other than weight, portability and maybe also cost. However, none of these are really contributes when you are actually looking into the eyepiece. The only exception is the field size! You cannot use your C14 to scan around the milky way, or to use even a C8 to view the beautiful Pleaides.
With the wide field capability, the Ranger can be used as a great finderscope as well.

Brighter deep sky objects show nice detail, and it's also a good instrument to locate and detect dimmer ones. It tooks me a few years to exhaust all the possibilities even I am observing in highly light polluted Hong Kong sky.

I found a 20mm Widescan Type III a perfect match with it for low powering scanning, since the increase in magnification effectively darken the sky and yet it provides the same true field of view with my 32mm Plossl. It helps to combat light pollution.

Narrow band light pollution filter like the Orion Ultrablock can work with the Ranger as well, for example, on M42, to bring out more nebula structure if you don't mind the color change.



Chromatic abberation on the Ranger - this is already the worst case and it's not that worse in my eye, the webcam definitely magnify the problem!

As a high power instrument: When we concern about rich field, one will say we better use a pair of binoculars, and it's even more compact and portable. While this is true, the Ranger can do more than that, it's to provide high power view.

For deep sky objects, small aperture scope are probably restricted to brighter and bigger targets like what I said before. However, small aperture scope like my Ranger, can really show some nice solar system objects at higher power, quick examples are the planets and the moon.

I can push my Ranger to over 120x with ease, while I have actually tried to push even higher, but it ends up to be empty magnification, yes you get a larger image but you also get a dimmer and less contrasty image. So, I usally use no more than 120x.

I found 120x is about optimal for planet observing with the Ranger. Chromatic abberation is kept very minimal at this image scale, and both the contrast and sharpness are still very high. Features like the Cassini division on the Saturn, the cloud belts of Jupiter plus the Great Red Spot (GRS) can also be seen, phrase of Venus is not a problem and the major feature of Mars during opposition is quite easy as well. I bought my 5x Powermate since I knew my Ranger can be pushed up after trying with some high power Plossls, the Powermate gives more flexibility and more importantly, to deliver high power with lower power eyepiece and to retain eye relief at the same time. For examples, the bundled 20mm Tele Vue Plossl works perfectly on the Ranger with 5x Powermate, it's parfocal and so you instantly boost the power by 5 times!

For the moon, the contrast of refractors are showing its power with the Ranger, it's particularly pleasing to the eye than even slightly larger compound telescope. Since the moon is very bright, I can use my binoviewer as well and the views are simply addicting!

For chromatic abberation, it is not very annoying for most of the objects except those brightest ones. When in good focus, most color error go away with a bit residue at the edge.

As a guide scope: Since I can push the magnification very high with the Ranger, it serves very very well as a guide scope to do guided deep sky imaging.



Ranger serving as a guidescope

For visual guiding purpose, one can really push the power beyond 140x, but it really depends on the seeing and transparency, poor sky condition will lower the limit. The Ranger is light enough, and also short enough not to overwhelm your mount for guiding purpose.



Webcam autoguiding experiment conducted inside my home

I have also tried to do webcam guiding with the Ranger, at f/6.8, I can find guide star quite easily. One will need a notebook, an ASCOM compatible mounting system to do so.

The draw tube and the helical focuser are built to very tight tolerance so that no image shift is detected. This is very important as a good guidescope.



A solar prominence taken with H-alpha solar filter with the Ranger

As a solar scope: when used with white light filter, or narrow band hydrogen alpha filter, the Ranger can be used as a solar scope. A solar telescope does not have to be large, and larger scope is less useful for day time seeing condition, and also the heat built up inside the tube can make larger scope less than perfect when used in hot day light.



White light image taken with the Ranger + 3x barlows

As a white light instrument, the Ranger is a bit on the small side and one would prefer a scope to have at least 3 inch aperture, but I would say, 2.7 inch can still do quite well for sunspot observation, especially when we consider that small sunspots are less interesting and larger sunspots can be observed effectively with a smaller scope.



H-alpha image taken with the Ranger + 2x barlows with Solarmax 40 and BF10

For narrow hygroden alpha observation, if one use a Coronado filter system, with its short focal length, one can use the cheapest blocking filter offering BF5 to see the whole solar disc. The minor chromatic abberation of the Ranger is irrelevant for monochromatic observation like in hydrogen alpha, other abberation of the Ranger is under very well control and I would say it has nothing worse than an apochromat for this application.



Ranger on Orion Min-EQ, taken on Venus transit 2004

As a traveling scope: Ranger is so light and therefore, I can put it in a medium sized backpack for wild camping and hiking. You know, I can run while everything are inside my backpack! Public transportation is also okay, not to mentioned any small car.

For overseas trip, you can also take it with you easily. The strong construction will give you a peace of mind during long travel, and the compact size will make it airline portable.

For solar eclipse chasing, it is even more convenient since you can use the same scope for deep sky scanning, or to do some guiding with a piggyback camera photography. I've yet to find a chance to take my Ranger to go for a solar eclipse, let's see.


M7 taken with the Ranger afocally

As an astrograph: The Ranger is less good as an astrograph, the relatively fast focal ratio makes it looked nice but the small 1.25" focuser will make vignetting worse than the Pronto. The focal reducer/flattener for the Pronto is not useable in the Ranger but we only have a flattener for the Ranger, which has a 1.1x magnification factor, making it a bit slower. However, the 1.25" focuser would not be too bad with APS-C sized DSLR. Finally, I have to say I didn't have much experience to do prime focus deep sky work with my Ranger yet, so take my advice with a grain of salt.


Jupiters taken with the Ranger + 5x Powermate

For planet/moon/solar imaging, the Ranger is not bad at all. For planets, it is more like limited by the aperture. But for lunar and solar imaging, some very pleasing results can be made.

The focuser is strong enough to hold a barlow plus a 1.25" eyepiece and a prosumer digital camera afocally.

As a terrestial scope: As a compact wide field instrument, the Ranger is widely used by the birding community at its age. The high quality optics plus the wide field capability, are making it a very good instrument for terrestial usage. One can buy a erect prism diagonal to provide correct image.

Mounting Options


I used a Manfrotto 410 mini geared head at first and it provides a very stable platform for wide field scanning and also for high power tracking. The Ranger is so light that the 410 handles the imbalance very well. Tracking can be done easily at over 120x.

Then I moved to a Unistar Light since the 410 head is not very good for wide field scanning for one can only unlock a single direction for scanning, the Unistar Light is perfect in that regard. Tracking is quite easy when well balanced, and 120x is not hard as well despite it lacks of a slow motion control.

Later I bought a Takahashi TG-SP II for it, and again, they work extremely good. One can scan around easily with the clutches disengaged, and one can track at high power without any problem.

I have also used my Ranger on my Giro mount, an Orion Min-EQ which was sold, and also a LXD55, all worked perfectly as expected. The Ranger is so easy to mount such that any reasonable mount would suffice.

Customer Services


I didn't use much of the customer services of Tele Vue as I am from Hong Kong. Once I did lost a set screw on the focuser and I wrote a letter to Tele Vue for a replacement, and they sent two to me rather quickly. So, now I still have one more as a backup.

Summary


If you have not yet owned a small refractor, please consider it seriously as they probably provide greatest value for the money due to their extremely versatile nature. As you can see its potential purpose in all the areas that I mentioned above, it's a real bargain since it can do it all.
The Ranger is a good example, it is not very expensive, it is very light weight, compact and portable. It delivers wide field of view which cannot be provided even with your light bucket. It lives with you as your observation habbit changes, it grows with you when you advance from casual visual scanning, to wide field photography, and even to serious deep sky imaging as a guidescope, or it will even work as a finder when you graduate with a giant light bucket.

Small instruments cannot beat the law of physics, and they are limited by the aperture size, but again, they can provide wide field of view, and high quality small refractor delivers every millimeter of quality aperture it provides!

Finally, don't be let down by the discontinued status of the Ranger, and don't hit me for reviewing a discontinued product, if you're going to find someone to hit, find those who write reviews for those small gems from Astrophysics, they should be even harder to get than the Ranger. I should emphasis that it is good to own a small quality refractor, but it does not necessarily to be a Ranger.

Similar offerings


I think I owe you this section if I managed to get you interested in the Ranger, since it's discontinued. So, please allow me to give some recommendation in case you want one:
  1. 2nd hand Ranger: you can see the 2nd hand section of cloudynights, astromart or even ebay, but it is not very much recommended since for such a good scope, no one would willing to part with it unless it got some problem? But you may still be able to get a good one when someone wanted to upgrade or having financial trouble. Depend on your luck.
  2. Takahashi FS60C: I have even compared this one side by side with the Ranger, should it be available at the moment when I bought my Ranger, I would probably go for it rather than the Ranger. It's even lighter and more compact, delivering even slightly better performance than the Ranger, and can be used with a reducer flattener for better photographic performance for deep sky objects.
  3. William Optics 66mm: Either the triplet version or the ED Petzval one should be good alternative to the Ranger. I have no first hand experience however.
  4. Borg small ED: either those ED mini-borg, or the slightly larger 76mm ED should be nice as well. I've conducted some side-by-side comparison of the 76mm ED with the Ranger and the Borg is very much more color free than the Ranger, the weight is very similar but you got more aperture, with a slightly longer OTA.

Frankly, I would say any observer should own a small high quality refractor to serve some or even all of the purpose which I mentioned above, and maybe to invent some more, say to start a BBQ fire with the sun light? One will enjoy it if it is your quick looking scope, or if it is your 2nd, 3rd or nth scope even if you have a 20" light bucket.

It is simply the beauty of small portable high quality refractor, not the Ranger itself! Enjoy!


By Oldfield SO

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