- Rebuilding my CGE Pro
- COUNTING SUNSPOTS WITH A $10 OPTICAL TUBE ASSEMBLY
- Hubble Optics 14 inch Dobsonian - Part 2: The SiTech GoTo system
- iStar Optical’s Phantom FCL 140-6.5 review
- Who’s Afraid of a Phantom: Istar Phantom 140mm F/6.5, that is?
- SHARPSTAR 94EDPH APOCHROMATIC REFRACTOR
- My Losmandy G11T review
- FIELD TEST: THE NOH CT-20 ALT-AZ MOUNT
- SkyTee-2 Alt/Az Mount Review
- SharpStar Askar ACL200 200-mm f/4 astrographic telephoto lens
- A review of the Unistellar EVscope
- Astrotrac 360 tracking platform – first impression
- FIELD TEST: CARL ZEISS APOCHROMATIC & SHARPEST (CZAS) BINOVIEWER
- Omegon 32mm 70º SWA eyepiece review
- Review of iPolar hardware and software for polar alignment
CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.
Small Scope Alt-Az Comparison: Wimberley vs. the GR-2 Deluxe
I have for quite some time looked for the ideal highly portable scope package. My viewing time is often quite
limited, and my principle viewing site (my yard) has a number of large trees; in order to see much, I need to keep
moving about the yard. In addition, my best viewing tends to be on vacations when we're in locations with really
dark skies, and I wanted something that was easy to carry (along with all the paraphernalia that goes with having
a one-year-old daughter).
As part of this hunt I have had a bias towards alt-az mounts. I have used three different alt-az mount heads fairly extensively, none of which have any kind of manual slow-motion controls: the Tele Vue Telepod head, the GR-2 Deluxe (also reviewed elsewhere on this site), and most recently a Wimberley. Below I will share my thoughts on the relative merits of these, most specifically comparing the GR-2 to the Wimberley.
The Wimberley tripod head is not cheap -- it costs $465. By comparison, a Telepod head is $230, and the GR-2 Deluxe head as pictured in this review is about $385 from APM in Germany (including the dovetail plate adapter and counterweight shaft).
Background of the Wimberley
The Wimberley was designed to be used with very large telephoto lenses, as illustrated in the picture below.
To quote from their website (www.tripodhead.com):
"The Wimberley Head incorporates an elevated tilt mechanism and an adjustable platform to perfectly
align the center of gravity of a big lens with the tilt axis of the head. This allows the lens to be perfectly
Perfect balance means that a 15 pound 600mm F4 behaves as if it were weightless. Point the lens, let go, and it stays pointed at the target. Dynamic shots nearly impossible with a ball head are routine with a Wimberley."
When I ordered the Wimberley under their demo program (more about that later), they indicated that a few of their customers used the mount with telescopes or spotting scopes, but the vast majority of customers were photographers.
As you can see below, the design is very simple. Scopes are attached to cork-covered mounting platform with a 1/4"- 20 threaded rod and knob supplied by Wimberley. The slot in the mounting platform is used to move the scope forward and backward to achieve the necessary balance. The two knobs (on the top of the base just below the mounting platform, and on the left side of the arm) are used to adjust tension on each axis.
Balance is the Issue
The more I use these alt-az mounts, the more I come to appreciate how important the approach used for achieving balance is to the success of the design. The illustration below from the Wimberley website (used with permission) illustrates how a telephoto (or telescope) needs to be balanced in order to remain stable throughout the entire range of motion.
By comparison, the shortcoming of the Telepod head is that there is no adjustment provision for the "height"
at which the scope is mounted (similar to what can be done with the vertically adjustable platform in the above
drawing). Due to this, the center of gravity of the telescope is not always aligned with the tilt (or altitude)
axis, particularly when using different diameter instruments, or different weight eyepieces. As a result, the scope
tends to "creep" at varying angles of elevation.
When I used the Telepod head with an Astro-Physics Traveler, it would not stay balanced; if the scope were perfectly balanced at 45 degrees, it would not stay put at 75 degrees. This imbalance contributed to the issue many have noted - namely, how a Telepod (or Gibraltar) at times is not very smooth in movements at higher magnifications. Since the balance point is not constant at different angles of inclination, users tend to clamp down a bit on the altitude tightening screws to keep the scope from moving when it's supposed to stay still. This, unfortunately, makes small intentional motions more difficult and jerky.
The GR-2 and Wimberley each offer better solutions to this problem, but use different approaches. The GR-2 attaches to a scope's mounting rings or other mounting point, thereby ensuring closer alignment with the telescope's center of gravity; the Wimberley has an adjustable platform that (as will be described below) makes perfect balance simple to attain.
A second difference between the Wimberley and the GR-2 is how they balance a scope on the azimuth axis (the pan axis in the above drawing). With a GR-2, this is accomplished with a counterweight, while with the Wimberley the basic design ensures that the combined mass of the scope plus the mount is balanced over the center of the tripod.
I compared the GR-2 and Wimberley using two fairly representative small travel scopes: a Celestron 5 and a Tele Vue 85. In order to understand the impact of tripod mass on performance, I used three fairly different tripods - a very compact Bogen 3221S, a slightly larger Bogen 3021, and a bigger, older Davis & Sanford (quite similar to ones sold by Questar). Without any kind of head, the 3221S tripod weighs about 4 pounds; the 3021 about 5 pounds, and the Davis & Sanford about 10 pounds. Below are pictures of the three tripods used.
3221S + GR-2 + C-5 (left) 3021 + Wimberley + TV-85 (center) D&S + GR-2 + C-5 (right)
The GR-2 is designed to accommodate very substantial scopes, but is also quite workable with smaller instruments. The Wimberley can handle big telephoto lenses, but this translates into the capacity to handle only fairly small scopes. Neither is an exact fit for use with small scopes, but I was curious to see how they would do.
Weight and Build Quality
The Wimberley weighs about 3 1/2 pounds, while the GR-2 (with the optional dovetail plate shown in the photos) is around 5 pounds. Not a big difference, but could be noticeable if you're going on a long hike. Both mounts are quite compact and easy to pack. In terms of build quality, both are very well made.
For those of you familiar with GR-2s, the non-standard aluminum plate on the bottom of mine is an adapter Ken Dauzat made for me to convert this from a 10mm attachment thread to a standard 3/8" 16 thread, making it easy to attach to photo tripods.
Balance - Altitude
This is where the Wimberley shines. It is a fairly simple matter to achieve absolutely perfect balance, through the entire vertical range the mount can point, without any tension on the altitude lock. Every scope - eyepiece combination I tried worked fine. I should note that in order to keep balance, the height of the vertically adjustable mounting platform would change with different scopes, and with significant changes in eyepiece weight on the same scope. For example, when I went from a 32mm Plossl to a 35mm Panoptic, I needed to lower the mounting platform with both scopes. This was a fairly simple thing to do, and once done the balance again was perfect. I found that after a little practice I could get to a perfect balance in about 30 seconds, and the subsequent movements were effortless. The scope stayed perfectly balanced (without any adjustments) in the positions illustrated below, and everywhere in between.
The GR-2 is pretty good, but definitely a step behind. With lighter weight eyepieces (say a 32mm Plossl) the
mount stayed pretty well balanced at all angles. However, with heavier eyepieces there were problems. For example,
when using a 35mm Panoptic, I couldn't get either the TV-85 or the C-5 to balance freely through all angles. The
problem is that the weight of the eyepiece changes the center of mass, and there's no good way on the GR-2 to adjust
and re-center the telescope's mass on the altitude axis. If I did not keep fairly strong tension on the altitude
lock, the eyepiece end would quickly dive down and the scope would point straight up (particularly as I pointed
closer to the zenith). The only solution was to balance the scope at about 60 degrees elevation. From there, it
stayed balanced up to the zenith, but would tip forward once lowered to about 45 degrees. For many scope and eyepiece
combinations it was fine, but there were limitations with heavier accessories.
With larger telescopes the GR-2 is much less sensitive to changes in eyepiece weight impacting balance. I used to use an Astro-Physics 130 EDT on mine, and this balance problem with eyepiece changes wasn't an issue. It makes sense; the weight difference associated with a change in eyepieces was a pretty small percentage of the total weight of the mounted AP 130, and the center of mass wasn't significantly impacted. However, with small travel scopes the impact is quite noticeable.
Balance - Azimuth
The mounts use two different approaches that work very well, but there's a tradeoff. The GR-2 has provisions for a counterweight shaft and counterweights. Using these, it was easy to achieve perfect balance and a very high level of stability. The downside, however, is the added weight of the counterweight, which detracts from portability.
The Wimberley (as noted in the illustration above) is designed to keep the weight of the telescope plus mount centered over the tripod at all times. The design works well and the scope stays completed balanced. The only requirement for bulk in the tripod is that it be sturdy enough to carry the mount and the scope.
I should note that the GR-2 head itself is extremely rigid and can easily hold any of these small scopes without a counterweight on the shaft. The tradeoff, however, is that the mounted scope is somewhat unstable depending on the tripod used, with the center of mass of the scope extending about 8 inches from the center point of the tripod (as in above pictures).
I tried the various scopes on the GR-2 -- without a counterweight - with both of the Bogens and the Davis &
Sanford tripod. Basically, the mass of the tripod performs some of the function of the counterweight. With the
Bogens, since there isn't much mass, there wasn't much counterweight, and the mounted scopes were way too unstable
for my liking. The C-5 with the 35mm Panoptic on the 3221S felt like it was pretty close to tipping over all by
itself. The Davis & Sanford tripod worked better (being more than twice as heavy as the 3221S), and a quick
try on my Astro-Physics hardwood tripod worked better still. Of course, both of these tripods are bulkier, significantly
detracting from portability.
Viewing stability and ease of motion
As might be expected, the stability of the view through the eyepiece varies quite significantly based on the tripod used. As a general statement the GR-2 and Wimberley are fairly equal -- given a sufficiently large tripod. However, on smaller tripods the Wimberley worked better. To test stability I tried both mount heads on all three tripods, using the TV-85 with a 6mm Radian, and the C-5 with a 32mm Plossl (see sample pictures above of tripod + mount + scope combinations).
On the 3221S with the Wimberley and the TV-85, the view of the moon at 100x would move quite a bit when focusing
or when the scope was moved. While it was very easy to move the scope small distances with good precision (I found
I could control movements of less than 1/10 the moon's diameter), the image would shake for about 3 to 4 seconds.
After that, it settled down nicely. I would characterize this combination (or the same with the C-5) as usable,
but just barely.
With the TV-85 and the GR-2 on the 3221S (with no counterweight) stability was even more of a problem. Owing to the heavier weight of the GR-2 itself and the off-axis mounting position, it took 5 seconds or more for things to settle, and the image moved significantly more than the Wimberley + 3221S combination. It was also fairly easy to move the GR-2 precisely, but not quite as easy as the Wimberley. To me, this was not stable enough to be usable; I was constantly nervous that it would tip over!
The 3021 faired better with both tripod heads, but was still fairly bouncy. And, while adding the counterweight to the GR-2 would have improved balance, it also would have pushed the overall weight capacity of these fairly small tripods. With the Wimberley this tripod was OK, particularly with the C-5, but the GR-2 was marginal.
On the Davis & Sanford things were much better; the impact of the sturdier tripod and larger tripod mass on overall stability was very, very apparent. The GR-2 and Wimberley performed nearly identically; focusing or moving the scope caused the image to move just a bit, and the image would settle down in about two seconds with the TV-85, a bit more than one second with the C-5. I couldn't really see much difference between the two mount heads on this tripod, they both worked very well. Taking the magnification up to 200x didn't seriously degrade performance. I concluded that higher magnifications were definitely workable with either, and superior to at least my recollection of using the Telepod head. At 200x, it can be a bit challenging to keep an object centered; I found initially that I tended to swing back and forth past the object, but with practice it worked reasonably well.
The table below roughly summarizes the comparisons on stability, measured in how long it took the combination of scope + mount head + tripod to settle down after movement or otherwise rapping the mount:
|Bogan 3221S||Bogan 3021||Davis & Sanford|
|TV-85 Wimberley||3-4 seconds||3 seconds||2 seconds|
|TV-85 GR-2||5+ seconds||4-5 seconds||2 seconds|
|C-5 Wimberley||3 seconds||2-3 seconds||1-2 seconds|
|C-5 GR-2||4 seconds||3-4 seconds||1-2 seconds|
This is the Wimberley's biggest weakness for astronomical use. Depending on the scope used, pointing straight up might not work. The pictures below illustrate what is possible; I measured the TV-85 at about 80 degrees, while with the C-5 it can easily reach vertical. Depending on the weight of the eyepiece (which shifts the balance point) the TV-85 needs up to about 5 more inches of clearance to point straight up. For the GR-2, this is absolutely no problem - the tested scopes, and much larger scopes, can easily reach the zenith, and there's no problem clearing the tripod legs.
TV-85 + Wimberley (left) C-5 + Wimberley (center) C-5 + GR-2 (right)
Big advantage for the GR-2. As illustrated elsewhere on Cloudy Nights, with a sturdy tripod and the right counterweights it can easily hold 30+ pounds. The Wimberley worked fine on the two scopes I tested, but I don't think it would be a good idea to go much above 15 pounds or so. Longer, heavier scopes will run afoul of the zenith test, and anything much bigger in diameter than a C-5 just wouldn't fit on the mount (see below).
Eyepiece change test
With significant changes in eyepiece weight, the scope needs to be re-balanced (moved forward or backwards,
either on the mounting platform or in the GR-2 dovetail). Also, when an eyepiece is removed (even if it is to be
replaced by one of similar weight, say of different magnification), the scope with the eyepiece out will be unbalanced
and unstable. As a test, I wanted to see if the altitude locks were sufficiently strong to hold the scope in place
even while I removed and changed eyepieces. I was concerned that if it did not hold, I would (sooner or later)
tighten the lock expecting that it would hold, remove an eyepiece, and find my scope rotating out of control.
The Wimberley again worked superbly. I did a test to maximize the change in balance point, and to emphasize a potential out-of-balance condition. In the C-5, I had the scope balanced with a 35mm Panoptic. I then fully tightened the altitude lock and removed the eyepiece. The scope did not budge, making it easy to swap in a 32mm Plossl and then re-balance. The pictures below illustrate how very different mounting points can be held firmly in place by the altitude locks (note where the C-5 is positioned on the mounting platform; the picture on the right is with the scope balanced).
The GR-2 did not do very well here. On my particular unit, both axes can be moved with moderate force even when tightened fully. I would be quite nervous leaving any scope in an unbalanced position on the GR-2. I think this reflects an explicit decision on the part of the GR-2's designers. While I agree it's best to have a mount that doesn't lock up too easily (as happened with my Telepod head), to me it's better still to have one that has a wide range of adjustments, including the ability to lock up when desired.
Neither mount has slow motion controls. In practice, due to the smoothness of the mount movements, I found this
not to be much of an issue on either mount. Also, the Wimberley has no provision for attaching DSCs or any kind
of tracking motors. For the GR-2, both of these are said to be close to consumer release.
Wimberley is a father and son business - David and Clay Wimberley. I have spoken with Clay several times and he has been extremely helpful. Further, Wimberley offers an extremely flexible "try and buy" program. They will ship you a tripod head (usually a new one) for a two-month trial period! You need to provide them with a credit card number to secure the tripod head; if you return it within two months, all you're out are the shipping costs.
The Wimberley is a wonderfully engineered tripod head, no doubt fabulous for its stated purpose of supporting large telephotos, and pretty darn serviceable with small telescopes as well. It is hard to describe how effortless it is to move a scope once it has been balanced; it truly is as if the scope had no weight. When used on a tripod like the Bogen 3021, it's a terrific, highly portable mount.
That being said, the GR-2 is more versatile and a little less expensive. It isn't as portable (particularly if you use a counterweight) and needs a bigger tripod to work well. It doesn't handle small scopes quite as well as the Wimberley, but it does OK with them and can reach the zenith with no problem. In addition, it has a huge advantage when it comes to handling larger instruments. I use it with my 6" Mak, and it is terrific. In addition, I find both of these mounts far preferable to the Telepod head.
If I could only keep one, it would be the GR-2. However, in my search for the best highly portable alt-az mount (regardless of cost), the Wimberley is the clear winner. I would say that it is a perfect alt-az mount for the C-5, and pretty good for the TV-85.
Now, all we need is an astro version! If the side mount arm were made about 5 inches taller, the TV-85 would reach the zenith and the one major shortcoming would be eliminated.
Will I keep the Wimberley? Probably; my only hesitation is if somehow we could convince David and Clay to give an astro-specific version a try . . . .
- Pine Colorado likes this