Various Eyepiece and Accessory Reviews

Page 3 -- By Ed Ting Updated 12/30/07

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1) Starbound Observing Chair 2) University Optics Orthoscopic Eyepieces 3) Book: Telescope Optics 4) Book: Star Testing Astronomical Telescopes 5) Pentax SMC-XL 7 mm eyepiece 6) Pro-Optic 11X70 binoculars 7) TeleVue Gibraltar Mount 8) Pentax .965" Orthoscopics 9) Kasai 30 mm 2" eyepiece 10) Orion Accu-Track DC Motor Drive (includes essay on add-on RA drives)

1) Starbound Observing Chair ($159 from various retailers) My crusty physics professor had a rule of thumb about observing. It went something like this: Compared to the average subruban back yard, getting out to a truly dark site is like doubling your aperture. While it may not be mathematically accurate, it is correct in spirit. I'm a little slow to catch on to certain things. For example, I've known about the benefits of using an observing chair for years, but did nothing about it. Anything that increases your comfort while observing will allow you to see more. I once wondered why some observers noticed detail which eluded me, even though they had inferior optics. Now, thinking back on it, many of those observers were seated. I wasn't. Standing up while observing and trying to keep still requires effort. When using a good observing chair, moving on to the next object becomes less appealing. This is especially true of planets -- while my limit was once about 10 minutes, I find it's nice to sit and watch the changing face of Jupiter for a half hour or more at a time. In fact, I'm such a believer in the use of an observing chair that I'm ready state my own maxim: The use of a chair effectively increases your aperture by one inch. With its adjustable height, the Starbound chair is probably the best of those currently offered. Jim Kendrick has just come out with a wooden clone that has a detachable tray for your eyepieces. Even though it's nicely made, I still prefer the Starbound model. You can also use a drummer's stool or one of those plastic luggage dollies that fold up into a seat. Just get yourself a chair. Any chair. Do it now. You can thank me later. 2) University Optics Orthoscopic Eyepieces (4,5,6,7,9,12.5,18,25 mm models, $55.95-$59.95 each) For reasons which are not entirely clear to me, orthoscopics have fallen out of favor lately. Observers and manufacturers have flocked to Plossls; in fact, it's safe to say that the Plossls are now the "standard" eyepiece. University Optics is now almost alone in championing the venerable orthoscopic. Employing a four-element design, orthos are just as sharp, on axis, as any competing design you care to name. The field of view is smaller than on a Plossl, but the eye relief is usually longer.
UO Orthos Champagne sharpness on a beer-budget: The UO Orthos (40 mm 2" Konig MK70 in back row)
I spent some time with several of these, and not once did I wish for my more expensive Plossls or Naglers. In fact, if you are primarily a planetary or double star observer, orthoscopics may be the best choice for you. They don't soak up as much light as the 5-8 element designs, and they're sharp. Drawbacks? The eye lens is small below 7 mm. The mechanical construc- tion isn't as solid as the TeleVue Plossls, or the Meade Series 4000 models -- they're light and small, and minimalist in design. They don't look as cool. The field of view (around 40-45 degrees) is small, compared to Plossls. But for the price (around $55-$60 each) I am not aware of any eyepieces which are sharper or more useful. I've been told by more than one observer who should know that these eyepieces deliver 90%-95% of the performance of the Zeiss Abbe Orthoscopics, at 25% of the price. Highly recommended. I have the distinct im- pression that I am going to wind up with a complete set. Update, 10/2/98: I had the opportunity to run a detailed comparison between the UO orthos and the TeleVue Naglers and TeleVue Plossls. The fact that I am running this test at all tells you how much I think of these eyepieces. I tested the UO 9 mm against the 9 mm Nagler, and the UO 12.5 mm against the 13 mm Nagler. I also had a TeleVue 10 mm Plossl handy, as well as a host of other eyepieces. The telescope was the Takahashi FS102. All of the tested eyepieces are sharp. It surprised me that the Naglers were as sharp as the simpler designs (I expected the orthos to be slightly sharper.) However, this sharpness was not evenly distributed. The 10 mm Plossl and both UO orthos had impressive edge correction -- I could put Jupiter half-in, half-out of the FOV, and there was no distortion. On the Naglers, chromatic aberration crept in, and the planet looked elooongated, if you get my drift. To be fair, though, no one spends a lot of time looking at the edge of the field in a Nagler. I didn't notice any light throughput issues -- the Naglers threw up images of Jupiter and Saturn that were just as bright (and the same shade of color) as the simpler designs. There are two issues, however, that might sway one towards the Plossls or the Naglers. One is an "emotional" issue, the other might potentially be annoying. The emotional issue is simply that the Naglers throw up a huge, picture-window like view, with a giant eye lens, that makes you think you're out in space. You feel as if you're part of the scene. The Plossls have a much smaller 50 degree FOV, but it's still large enough to be involving, even if the eye lenses are small- er. The UO orthos, on the other hand, have a comparatively tiny FOV, and you are always aware that you are looking through a telescope at an object, rather than at the object itself. Now, some people just won't care about this, and will go for the orthos, due to their simplicity, inherent sharpness, and low cost. The bottom line is that the Naglers give you an emotionally-involving view, while the orthos tend to give you an accurate, more "clinical" view. There is a more serious issue with the UO orthos, however. As the night drew on, I began to notice some annoying glare through the UO eyepieces on Jupiter at certain angles. This was also true, looking at the moon. Examining the eyepieces in daylight reveals why. Turn your eyepieces over. On more expensive units, there is a field stop, or a baffle around the lens area. The Panoptics, Naglers, and Plossls (25 mm and under) all have these baffles to shield stray light. The UO orthos, while they do have blackened edges and threads, do not. This allows some stray light to enter the lens, and can cause some glare. Note that this problem only occurred at certain angles and eye positions, and only on Jupiter and the moon (Saturn isn't bright enough) but it happened just enough to be annoying. I think UO should redesign its orthos with some sort of baffle. The eyepieces are so inherently excellent, optically, that I believe it would be worth the effort, even if they had to charge more for them. ...And yes, I am still thinking of acquiring the whole set. 3) Book: Telescope Optics (Harrie Rutten and Martin van Venrooij, $24.95, Willman-Bell) Every telescope-loving astronomer needs this book. The authors meticulously go through just about every telescope and eyepiece design imaginable. The best parts are the spot diagrams showing you exactly what happens to the star image when it reaches the focal point, using various telescope designs. There's enough drawings, diagrams, and formulae to keep you busy for a lifetime. Highly recom- mended. 4) Book: Star Testing Astronomical Telescopes (HR Suiter, $24.95, Willman-Bell) Star testing your telescope is so easy, everyone should learn how to do it. The test is so simple, sensitive, and fast, you should do it every time you take out your telescope. Yet, only a few years ago, no one knew how to properly conduct a star test. Enter Suiter's book, which has taken the hobby by storm. Suiter uses computer- generated images to show you how to recognize various aberrations. Then, he supports these images with exhaustive data and analysis. With some study, this book is going to turn you into an optical expert. A confession: I have, on more than one occassion, fallen asleep dreaming about telescopes with this book in my lap. An essential text. 5) Pentax 7 mm SMC-XL eyepiece ($432 list, about $325 street) The Pentax eyepieces share a similar design philosophy with the Naglers. They're large, premium eyepieces, with a generous (65 degree) field of view. There appears to be a small barlow built in to the bottom of the eyepiece, just like on a Nagler. The SMCs are beautifully-made, huge and heavy, with a screw-up rubber eyecup that looks like an upside-down funnel. I am not sure if they will fit in "tight-space" telescopes like the ETX or the Questar. I finally got a chance to A/B this fine eyepiece with the 7 mm Nagler. The Pentax surprised me. It had less chromatic aberration, and seemed slightly sharper as well. Also, the SMC has twice the eye relief - 20 mm vs 10 mm. You pay for all of this, of course. The Pentax costs a whopping $100 more than the already-expensive 7 mm Nagler. If you're seeking the ultimate performance in a cost-no-object eyepiece, look no further. 6) Pro-Optic 11X70 binoculars ($199.95 list, $159.95 street)
Pro Optic 11X70 Pro-Optic's 11X70 binoculars
"The pain of poor quality lingers on long after the pleasure of low price wears off." These words echoed through my head as I placed my order for these 70 mm binoculars. I had planned to order the Orion Mini Giants ($269), but the low price of this pair caught me in a weak moment. As a result, I experienced "Buyer's Remorse" almost as soon as I hung up the phone. The binoculars arrived a few days later. They are well-constructed and apparently made in Japan. The lenses are multi-coated in a very dark green. There is no light cutoff from the BaK-4 prisms. The binos have a solid, serious feel to them, despite being even lighter (2.8 lbs) than the already lightweight Orion Mini Giants. Hmmm...Looking through the binos reveals a bright, sharp image, with very little softening or mushiness at the edges. The Pro-Optics have a smaller FOV than the Orions (4.0 deg vs. 4.5 deg) but they're sharper across what field is there. After a few tense initial minutes, I relaxed. Hey, these are good binos! They gave very pleasing views of the Pleiades, M42, and the Double Cluster. Sweeping through the Cygnus Milky Way is a lot of fun. These are going to come in handy for sweeping fields as I work my way through the Herschel 400. What's more, they are light enough to hand hold for several minutes at a time. The binos come with the standard battery of accessories I never use - two straps, a cheap hard case, and a piece of cheese cloth. There are two lens caps for the eyepieces and one huge cap for both objectives, which is "back- wards" and the only fault I can find with the binos. These Pro Optic binoculars are cheap, and they're good. Highly recommended! 7) TeleVue Gibraltar Mount (Alt-Az mount, in ash -$475 street- or walnut/brass -$600 street-)
Gibraltar Photo TeleVue's Gibraltar (Ash Version)
Al Nagler is into Alt-Az mounts in a big way. All of his current mounts (the Panoramic, Gibraltar, Up-Swing, etc.) use the same principle. The tube ring of the scope is bolted to a swinging cradle, whose tension is adjustable by two brass thumbscrews. All the mounts work well. The Gibraltar is the "large" size mount, suitable for use on 4" refractors. The mount weighs 17 lbs in ash, or 20 lbs if you opt for the high-zoot brass and walnut version. With the legs retracted, it puts most 4"-class refractors at the right height for a seated observer. For a telescope like the Renaissance, the Gibraltar is an ideal mount. It's about as sturdy as a Super Polaris, but a few pounds lighter. The smooth "Dobsonian-like" motions are easy to master. For high power viewing, how- ever, nudging the mount every few seconds can get a bit annoying. Also, in the wind, I found it a bit unsteady at powers over 80X. The Gibraltar is available with TeleVue's Sky Tour system, which uses encod- ers mounted on each axis. It's a competently executed system, but at close to $700, it's pricey. 8) Pentax .965" Orthoscopic Eyepieces These are superb quality eyepieces that will make you rethink what's possible within the .965" format. They're sharp to the edge, have an acceptable 40-45 degree FOV, and are beautifully-made. I am told you can order them through any authorized Pentax dealer.
Pentax Orthos Good things in tiny packages: the Pentax orthos: (l to r) 5, 6, 7, 9, 12, and 18 mm
I used these in conjunction with the Takahashi FC-76 and FC-50 on Jupiter and Saturn, and never once wished for conventional 1.25" units. The sharp- ness of these eyepieces is really impressive; placing Jupiter half-in, half-out of the FOV at the edge (a demanding test of any eyepiece) revealed no distor- tion at all. These orthos have achieved a kind of cult status among users; indeed, I am hard-pressed to name a sharper line of eyepieces. The only real disadvantage of using these (other than the price, about $200 each if you can find them) is when you're viewing large objects like M31 or the Pleiades. The narrow .965" field stop maxes out your FOV right around the 18 mm unit. Recommended for the .965"-phile. 9) Kasai 30 mm 2" Eyepiece A rare specialty item. Designed in Japan, the Kasai is a clone of the 30 mm, 88 degree FOV Leica eyepiece ($1600.) The Kasai offers even more FOV (90 degrees!) and does so for less than half the cost.
Kasai "Would Sir like a 90 degree FOV eyepiece?"
In actual use, you notice two things right away. First, on popular showpiece objects like the Double Cluster or the Pleiades, there is a "holy cow!" feeling as you pan your eye around inside the eyepiece, trying to catch the whole view. However, there is significant distor- tion near the edges. Aberrations creep in at the outer 20% or so of the FOV. It reminds me of the edges in a pair of cheap binoculars. There is no "magic" to building a super-wide FOV eyepiece. Al Nagler once showed me how to make your own 100 degree FOV unit: unscrew the barlow from the bottom of a Radian. The challenge is making a wide FOV eyepiece that's sharp to the edge. I'm not sure if an eyepiece like this (or the Leica) is a necessity, but everyone should at least get to look through one at some point. 10) Orion Accu-Track RA Drive ($99 add-on RA drive that fits many mounts) I have been looking for an excuse to write an essay about these third- party add on RA drives. The recent purchase of one of these Orion Accu-Tracks allowed me to revisit this topic. Astronomers tired of hand-tracking celestial objects often turn to these generic motor drives. However, it is more than simply a matter of dropping your money (usually around $100) attaching the unit, and sailing off into the sunset.
Orion Accu-Track Orion's Accu-Track, on my mount
Based on my experience and the e-mails I get on this topic, I'd estimate that about half of these units don't appear to function when you first turn them on. There are several reasons for this, and you need to tackle them one by one. 1) FIRST, your scope must be balanced in RA. These little motors generate very little torque, and even slight imbalances will cause the unit not to work. While you're at it, balanace the tube in declination as well. 2) SECOND, you have to make sure that your RA tension is not adjusted too tightly. You may have liked the "tight" tension on your RA cable when you were tracking by hand, but the little motor may not be able to deal with this. There are two solutions to this. First, you can adjust the tension on the worm gear on the outside of the unit, usually using two hex bolts or two allen bolts. If the tension is still too much, you'll need to remove the RA control head, open it up, and manually reset the tension on the gear. There is a possibility that after you reset the tension so that the motor will "kick in," your RA axis may now be too loose. In extreme cases, the scope will drift down due to gravity while you're viewing an object. In most cases, you'll be able to find a happy medium between too-tight and too-loose. Then again, you may not, and you will simply have to live with the fact that your mount cannot accept a motor drive. 3) THIRD, you have to make sure that the set screws on the drive shaft are set correctly. The larger set screw is designed to key into the cut in the RA shaft, while a smaller set screw attaches the shaft coupling to the motor itself. This smaller set screw is designed to give way in case something gets stuck and prevents the motor from burning out. All of this is fine and dandy, but these little screws are forever coming loose, requiring frequent checks and tightening. 4) FOURTH, once you get everything up and running, you need to understand if your RA drive has a clutch or not. On the Orion unit, if you want to use your slo-mo RA cable, you need to disengage the motor from the shaft by unlocking the set screw. You can easily forget to do this, which may result in damage to the motor. On a Super Polaris for example, you CANNOT use the slo-mo cables while the motors are on and the clutches engaged -- attempting to do so will cause damage. So, you need to keep straight in your mind whether the slo-mos are active or not. I've removed the RA cable from my mount temporarily, to avoid unhappy accidents. 5) FIFTH, all motors generate some vibration. At high powers, you may see the image "buzzing" back and forth due to this vibration. Mine isn't bad at all, but I've seen some really lousy ones. 6) SIXTH, if your unit uses a 9V battery and you live in the frozen north (as I do) you will find that these little batteries don't like the cold. They stop putting out the juice just when you need it the most. To add insult to injury, just when you get them inside where it's warm, they sometimes start working again. Also, these 9V batteries do not always output a steady stream of voltage and current. Factor in the rapid temperature and humidity changes we often experience in this hobby, and you'll find yourself making lots of adjustments to the speed control through the course of the night. If you can get all of this straight, the results are worth it. Not everyone will experience all of these issues, but at some point they may creep up. Just beware, and have some patience. This is the price you pay for con- venience. End Various Eyepiece Review, Page 3
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