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SV 50 Finderscope meets WO 50mm Bracket

Posted by Timm Bottoni   08/24/2007 12:00AM

SV 50 Finderscope meets WO 50mm Bracket
An unlikely combination turned out to be a perfect match for my finder scope and bracket needs, when I paired the new style, quick release WO (William Optics) 50mm finder bracket, with the new style SV (Stellarvue) 50mm RACI (Right Angle Correct Image) finder. Yes, you read that correctly, and much to my pleasure, these two products from competitive companies didn’t burst into flames upon contact.

The search for a new finder scope and bracket

My WO Megrez 80SD refractor package originally included a WO 6x30 finder scope and bracket as a part of the package price. I liked it and used it a lot, but as always, needs seem to change over time. Originally, I was using the WO Megrez 80FD on a modified Nexstar GoTo mount, so the mount did most of the real finding for me. After getting the WO EZTouch mount, I found I was using the finder scope and bracket a lot more, trying to find objects without GoTo help. I realized that I might be able to benefit by upgrading so I started thinking about what I might like.

I always removed the original bracket after each observing session to return everything to its backpack case, and when I would put it back on the next time; the combination of the single attachment thumbscrew, along with the smooth felt face of the bracket required me to spend extra time each session getting it lined back up. It never seemed to be angled exactly the same each time, and tightening the bracket seemed to result in it swiveling slightly, and a little more loosening and tightening to get it aligned. The WO 6x30 finder scope was also very nice, with sharp, clear views that included a lighted cross hair, which used a set of two small batteries to power a red LED attached to the finder near the eyepiece end. This was a nice feature, but in all honestly with my light polluted skies, I didn’t use it all that often (and I often forgot to turn it off, resulting in dead batteries). The 6x30 was a straight through view, that was corrected both top to bottom, and left to right. This made using the finder quite easy, since the image was neither inverted nor flipped in direction. The problem with a straight through finder however, is that it becomes awkward to use when trying to locate object near Zenith, and requires you to get underneath it, twisting your neck to use that straight through view.

First: The WO 50mm new style quick release bracket

I was looking for an improvement in alignment time and repeatability, so I got a new style WO 50mm bracket. I found it to be a very simple installation since it was a complete replacement for the original bracket. The bracket mounts to the scope using the same threaded hole in the focuser, but rather than the entire bracket being held in place by a single thumbscrew, a separate base piece is secured in place with a single tightened hex screw. The result is a very secure fit of the base to the scope, that once tightened does not twist easily. The entire bracket, both the small attached base piece, and the stalk and ring assembly is made of precision machined aluminum alloy, finished in a flat black anodized coating. The stalk fits smoothly, yet securely in the base, and is held in place by a thumb screw that mates to the stalk in a cut out groove. There is a small amount of wiggle room, but the tolerances are very close.

The WO 6x30 finder scope was easily removed from the original bracket, and inserted into the ring assembly. Once in place the finder scope was easy to align using the Teflon tipped tri-screw alignment configuration in both the front and back rings. All in all, this is a very simple and intuitive setup. The bracket is designed to handle a variety of sizes of finder scopes, including both of the William Optics models, e.g. the 6x30mm model I owned, and the 7x50mm model. The dual sets of three screws provide enough adjustment to allow for nearly anything from 20mm to 55mm in diameter, which covers the range of most finder scopes, and perhaps even a handheld laser (which I don’t have, but thought hard about getting before making my final decision on a finder scope).

Since the base remains on the scope at all times, each night when I am finished observing it’s a simple matter to remove the finder bracket and scope with the single thumbscrew, and put it away. The next observing session requires only that I insert the stalk, tighten the thumbscrew and observe. Well, almost, since in spite of very closely machined parts, the possibility for human alignment error exists. While the side to side movement is nearly completely eliminated, the front to back placement can result in a slight amount of shift. I found it was best to get it in place, carefully lining up the front and back, and then tighten it and spend 30 seconds on Polaris, just to get it as close to perfect as I had the patience for. The end result is a product that looks great, and allows for quicker and more consistent alignment from night to night, and stays securely in place once tightened.

Are there any issues with the new WO Bracket?

There aren’t any problems with the bracket, but it is designed only for WO scopes, so if you are interested in this bracket you will want to make sure it will fit your scope before spending $99. It handles a wide range of finder scopes, but be careful to check the dimensions just to make sure. The inside dimensions are 55mm, exactly as stated on the WO website, which I confirmed by measuring it with a digital caliper.

The bracket base that is left on the scope also has another slight issue with the WO rotating focuser on my model. While this many not be much of an issue, it is worth mentioning, since there are a lot of Megrez 80 scopes out there. The focuser normally rotates freely, 360 degrees, after loosening the silver thumbscrew that secures it from rotating. The thumbscrew spins with the focuser, and now comes in contact with the base of the bracket. This means that there is one small spot on the rotation circle that the focuser can no longer be placed in. It also means that if you are rotating the focuser one way, and are stopped because of the base, you may have to reverse directions and spin the focuser the other way to get to the spot you were trying to reach. Again, I don’t see this as a very big issue. There are certainly less expensive finder scope bracket options for those who are less interested in something this versatile, so it’s $99 cost may classify it as a somewhat expensive option for some people.

Next: The Stellarvue 50mm Finder Scope

After using the combination of the new bracket and original WO 6x30 finder scope a number of times, I got to thinking, this finder bracket has lots of room for a bigger finder, and wouldn’t it be an advantage in my light polluted skies to have a 50mm finder scope? So I started to look at the options, reading reviews, forum posts, and asking people I knew who had used various options, what they preferred. I liked the correct image view of the WO model I had, but I found that a large part of my time was spent looking up towards Zenith, which is the area of the sky least likely to be plagued by light pollution. This can be awkward at times, with a straight through finder scope, so I inquired about RACI (Right Angle Correct Image) finder scopes from a number of sources.

I number of weeks went buy, and a variety of opinions and reviews were analyzed and I finally decided on the new style Stellarvue 50mm model, which now includes a rotating back. This new model sports several nice features that simply make this finder scope a joy to use, and an excellent value. I had gotten the specs from Jennifer at Stellarvue by email, and had someone I knew who had one measure the diameter, and it seemed like it would just barely fit, which had me worried about being able to adjust it enough to allow for proper alignment, but I went ahead and ordered one anyway. The new model is available in white, shiny black, and new flat black which came out just after I bought mine. Everything I had read about this finder scope was very positive, and the reviews raved about SV customer support, the quality of the product, and the fact that it would also support most standard 1.25 inch eyepieces. It was affectionately known as the “Sparrow Hawk” by SV fans, and it sure looked good in the pictures I saw.

A closer look at the Stellarvue 50 aka “Sparrow Hawk”

First, the objective of the scope is a 50mm cemented doublet held in place by a substantial dew shield, which extends approximately 2 inches from the front element. Yes, I took it all apart, I tend to do that with things, but I had to figure out how to get it into the bracket anyway, as it wouldn’t fit fully assembled. The optical doublet seems well made for a 50mm F/4 (focal length about 200mm) finder scope. The dew shield is fixed at its extended position which helps to keep dew and stray light from entering, and also holds the doublet aligned in place when firmly screwed in place on the tube. The inside of the dew shield is flat black and threaded to help keep out unwanted reflections, and serves it’s purpose well. Note: Be careful if you unscrew the dew shield, it is all that holds the glass doublet in place.

The finder includes a nice set of well fitting dust caps for both the front and back. The quality of the 50mm objective lens is the first real treat, which is described further in the optical testing section. The box, foam, packaging and manual were all top quality, but pretty much ignored initially due to the excitement of opening it up to get to the scope itself.

The entire finder scope is finished in a shiny black coating that looks nice, and not cheap like some of the finishes I have seen on several of the less expensive finders out there. Moving further back, the tube is exactly 54.4mm in diameter by my digital caliper, and ends in a nicely threaded union to the RACI prism that is held securely inside of an assembly that appears to be custom made by SV with their logo on it. The prism diagonal assembly can be unscrewed, and can also be rotated while the finder is secured in place, by loosening the thumb set screw on top. This is a very nice feature, and is new to the 50mm finder scope line by SV, replacing the original design that was fixed in place. This rotating back feature added a slight additional cost to the product, over the old model. Being able to rotate the eye position is probably worth its weight in gold, if the configuration is mounted on a GEM setup, as it would facilitate much easier eye placement no matter where the scope is pointed.

But wait, don’t order yet, there’s more!

There are two helical focusers that provide precise focusing ability. Why two? Well, the first is to adjust the focus point for the image viewed through the eyepiece, and the second is to adjust the focus point of the crosshairs. The eyepiece is a 23mm eyepiece with a standard width field of view, and built in cross hairs, which allows for the precise focus of both the image and the crosshairs at the same time. While it may sound confusing, the included instructions are pretty clear if you choose to read them, which I did after figuring it out just by trying it. It’s pretty simple, and a bit of trial and error should have most people with focused views of the sky and focused crosshairs pretty quickly. Just remember that both helical focusers affect each other, so you may need to get the hang of turning both at the same time if you are particular about having the image and the crosshairs in perfect focus.

There are some extra things on the end that needed further exploration, and explanation. The first is a round rubber plug of some sort that is stuck in the side of a hole in the eyepiece. Hmm, this is strange; it looks straight into… a hole that goes no where. It’s actually the hole to light the crosshair. The crosshair is not a wire, but a keenly engraved image on a disk set at the focal point, which makes sense when you realize that SV sells an optional Rigel Pulse Guide light to light up the cross hairs. Very clever indeed! I didn’t purchase this option, but removing the rubber plug, and shining a light into the hole lets you see exactly how the illumination process would work, if this option were purchased and threaded in place. This means I could always add it on later for $39 if I wanted to.

Is it a “finder” scope or a “tele” scope?

There is also a thumbscrew that can be loosened, and poof, the eyepiece is loose and can be removed completely, revealing a standard 1.25” eyepiece opening. OK, sure, but will a standard eyepiece actually work, and why would you bother since there are no crosshairs in standard eyepieces? Hmm, well, of course, I had to try it. I tried all three of my 1.25” WO UWAN 82 deg FOV eyepieces, and had no trouble getting any to reach focus. I also tried all three of my WO SPL eyepieces, and they worked well too. In fact, there is a growing list of supported eyepieces available on the SV Yahoo group, and it looks like most standard eyepieces will work. Well, I had read about people using it as a small 50mm F/4 telescope, with a 200mm focal length and a variety of eyepieces for star gazing, and thought I would give mine a try. The conclusion? It’s not bad for night time use, and really darn nice for average daytime spotting scope use. Sure, I know there is false color, it is after all, a fast Achromatic doublet, and at F/4 doesn’t do all that well in the outer third of my 82 degree field of view WO UWANs, but anytime I can get double use out of something for little or no cost, I consider that to be a good thing.

The 200mm focal length results in a magnification of about 9X with the supplied 23mm crosshair eyepiece, which I believe to be simple design with about a 50 deg FOV. The resulting field of view is about 7 degrees of sky, which is a nice setup for my finder scope needs. The UWANs yield magnifications of about 12X for the 16mm, about 28X for the 7mm, and about 50X for the 4mm UWAN. Even at 50X, where the false color becomes noticeable on bright night time objects, the overall image quality is still good. During daylight, a 50X magnification is quite acceptable considering the price of this product, but does show purple fringing, and edge softening and distortions mostly due to field curvature and some astigmatism but remember – this is designed to be a finder scope, not a spotting scope or telescope. I tested it in my basement using my charts, including a grid and a detail chart, and both charts help up well even at 50X, again with the obvious field curvature and astigmatism out past the halfway point with my UWAN eyepieces. Using all of my WO SPL eyepieces, in sizes 12.5mm, 6mm, and 3mm, I found the image to be sharp to nearly the edge.. It doesn’t appear that barlows will work, and I didn’t have one to test anyway, but then, seriously, I can’t figure out why someone would want to use a Barlow with this product, so it really doesn’t matter.

I think if used with decent plossls, or even a 8-24 zoom eyepiece it would be good enough for a super small and portable telescope or spotting scope.

Are there any issues with the SV 50W finder scope?

The shiny black finish is quite smooth and slippery. It looks great, but this smooth finish makes it harder to tighten it down to prevent it from accidentally spinning in the WO finder bracket due to the non-marring nylon or Teflon coated adjustment screws. I am afraid to tighten it too much, for fear of damaging something, so I have to be careful not to twist it when handling it. I would probably have chosen the white or the flat black model if I had realized that.

The helical focusers turn so smoothly that it’s easy to move them accidentally and have to refocus. This is a minor issue of course, but it would be nice if it actually wasn’t such a smooth focuser.

As stated in the optical testing section above, this is not going to make you happy if you trying to buy a 50mm telescope because it’s simply not designed as that. It has clear optical limits as a telescope and spotting scope, so even though it serves double duty for me, and many others, it is what it is – and excellent 50mm finder scope first. If you are looking for something super small and portable, take a look at the variety of offerings in the 66mm small APO refractor choices out there. They are designed as telescopes first, and truly will be able to handle higher magnifications much better than the SV 50mm finder scope, but at a much higher cost of course.

There is one additional unavoidable issue with a larger finder scope, which is not really a function of this particular product that I want to point out. Using it on my current EZTouch mount setup can sometimes cause balance issues, since it adds a lot more weight in a location that is hard to balance out at time when switching eyepieces. The EZTouch mount is so smooth, that if you don’t have the balance perfect, and forget to tighten it down between switching eyepieces, it is likely to start moving on you. When you are pointed near Zenith, the finder scope and bracket also have a tendency to cause the scope to want to start to tip over the top. This is an issue that can only be resolved with some sort of counter weight, and for now it’s something that I have just learned to live with, and is a worthwhile trade-off for me.

Again, this is not also product for the ultra thrifty purchasers either. At $119 without a bracket, there are certainly less expensive, and very good finder scopes available from a variety of sources. But if quality is what you are looking for, and the combined price of $218 doesn’t make you flinch, I can’t imagine there is any other setup that could work better for me.

Final Conclusions

This unlikely pair of accessories from WO and SV have turned into a real beauty of a combination for just what I needed to solve my needs for a quick install and release, RACI 50mm high quality finder scope. I would highly recommend both products to anyone who is looking to meet needs similar to the ones I have.

Click here for more about the SV finder. -Ed.

Click here for more about the WO bracket. -Ed.