Apo-tmosphere: Gutekunst ADC Review
Sep 23 2015 11:18 AM by pbsastro
Optolong LRGB Filter Testing and Comparison wit...
Sep 22 2015 01:41 PM by turbo399
First Light Review: Teeter Custom TT Planet Kil...
Sep 04 2015 12:57 PM by Zellmer
The Baader Planetarium Morpheus
Aug 20 2015 10:45 AM by wapaolini
Categories See All →
- CN Reports
- User Reviews
- How to . . .
- Observing Skills
- Astronomical History
- Optical Theory
- Vision and Related Experiments
- How to Gain the Support of your Family for your Astronomical Pursuits
- Evaluation Tips
- Special Events
- The Elements
- New Articles in [!monthname!]
- Telescope Articles
- Submit a Review / Article
- Monthly Guides
- Behind the Scenes
- About Us
- Copyright ©
- Terms & Conditions
- Tiny Eyes on the Skies
- From the Editor's Desk
- What's Up . . .
- The Light Cup Journals
- Who is this Super Light Cup?
- Cloudy Nights T-Shirts
- Imaging Contest
- Small Wonders
- Previous Imaging Contest Winners
- This Month's Skies
- Mike's Corner
- The Cloudy Nights Friends and Family Discount
- Uncle Rod's Astro Blog
- Fishing for Photons
- Binocular Universe
- Article Submissions
The Novosibirsk TAL 200K Klevtsov Cassegrain
At last I have a telescope that sees better than I do. This instrument is a carefully designed and built Cassegrain with a big difference, its tube is open at the top like a Newtonian. The Klevtsov optical train uses a meniscus like a Maksutov but there the familiar ends. This design offers a few disadvantages and many advantages over all other scope designs.
The Klevtsov is no featherweight. The tube is 18.5" long with focuser and has a diameter of 9 3/16". The ID is slightly over 8". The OTA weighs 22.5 lbs., about the same or a little heavier then the Celestron C-9.25 which is a bit of a surprise. When "mount ready" with stock finder scope, diagonal and eyepiece it weighs 27lbs. The OTA is twice as long as it’s diameter, giving it a longish appearance. It wants for a handle. A front and rear cover is provided. As with a Newtonian no dewcap is needed.
The OTA is finished with the gem-like Novosibirsk white. The front and rear collars are painted black and very substantial, far more so than the Intes Micro Scopes. The rear assembly is dished out and appears to be much more rigid than the straight back of the M603 or C-9.25. The optical components of this scope are going exactly nowhere.
The obstruction is 71mm, about 12% by area. There is no secondary; in its place is a 2-element corrector. The scope looks like a robust Newt from the front. The spider vanes are very robust; they are cast steel rather than strap metal and are gracefully curved, giving a "turbo" look. There are no "spikes" in the image. There are no adjusting screws visible. Note: later editions of the scope have straight vanes.
The corrector assembly has a negative meniscus and what seems to be a second surface curved mirror (this I determined by looking at the optical diagram, but it might just be the way it’s drawn). Light appears in the drawing to pass through both elements twice. All elements are spherical.
The manual says that all aspherical aberrations and coma are fully corrected as is "a little" longitudinal chromatic aberration. It goes on to say "correction of residual aberration is perfect", and seems to say that the scope has less error than other reflector telescopes. I saw no optical distortion whatsoever.
The Klevtsov secondary needs no collimation. The primary is adjustable, however, the manual does not instruct on collimation. It is clearly the intent that post-production collimation be unnecessary. If this proves true, that is a very nice feature of the design/construction.
The manual says that the primary can be removed for cleaning, and a cleaning procedure is provided, but no specific instructions for removal/replacement of the primary mirror is given. I believe that all maintenance is intended by the manufacturer to be done from the focuser end, the secondary should not be disturbed.
I checked collimation with the Helix laser grid. The primary mechanical is a tad off (expected). The diagonal mirror is also off a tiny amount (unexpected). The screws to disassemble the diagonal are covered by a thin metal decal containing all of the lettering found on the scope, giving model, s/n (mine is #17) and date. I carefully pried this decal off without damage and found 8 screws underneath, 4 for securing the mirror assembly to the diagonal body and 4 for collimating the mirror. Again using the Helix, I jockeyed the mirror until the grid pattern centered.
A star test verified that the optical collimation is perfect.
The Cassegrain baffling is "imperfect", more stray light gets past the secondary than the C-9.25 or the Intes Alter M603. This is the classic Cassegrain trade-off, perfect baffling costs you effective aperture as there is no way to achieve it without blocking part of the light traveling from the primary to the secondary. The result is a very bright image but a scope less suitable for terrestrial viewing, and some tendency to flare or ghost. The inside of the OTA is blackened and has a flocked surface that could be better. The scope has a rather distant close focus point. It’s far too heavy to take birding in any case.
The diagonal inserts into the all-metal focuser as any does many other diagonals, via a slip fit tube. But the diagonal has an extra tapered collar on the scope end, flaring outward (similar to the 1.25 to 2" adapters on the Synta refractors). This allows you to loosen the setscrews so that the diagonal can be rotated without any possibility of the diagonal sliding out and falling to the ground. The setscrews capture the flare of the flange before actual clamping. A nice feature. A standard 1.25" diagonal can be used.
Using a simple screw, this is the first Russian product that I have seen w/o a split ring for eyepiece capture. The focuser is a rack and pinion and uses the standard Novosibirsk tensioning system. (Hold one knob while turning the other.) Some "s****ing" was felt while racking the focuser inward which went away in time. This scope does not have a standard SCT tailpiece. A standard focuser can be adapted and is available from ITE (Internet Telescope Exchange).
A Pentax Universal Screw Mount adapter replaces the diagonal for photography. A Pentax screw mount body screws right on at prime focus. A T-Mount adapter is provided so you can use other bodies with the T mount accessory as appropriate for the camera attached. So you can have it either way. The 35mm photographic FOV is 40 arcminutes.
The finder is the same as the TAL2, 8x50 and first rate. It is really a small telescope by its own right, having a nice helical focuser and (very fine) open center cross hair. It came with a dewcap but no covers. There is a dovetail base and a clamping screw has been added to the assembly, the finder bracket has a clamping screw with no front to back play as does the TAL2, an improvement. The Orion SCT dovetail ring assembly clamped into the dovetail base with a little application of a flat **** to it edges. This gave me a way to easily attach my GRO RA super finder.
The scope comes with its own dovetail mounting/clamping system. The bar does not extend from front to back like others, but is very heavy, sturdy and positive. By drilling two holes (drill press required), it can easily attach to a "Polaris" type mount. (GP, SVD, G11, CG5 ). You balance the scope by sliding it back and forth in the dovetail.
A "super" 25mm Novosibirsk Plössls is provided, along with a 10mm and a Barlow. The 25mm comes with a screw in crosshair, a nifty accessory. Both eyepieces are identified in the manual as symmetricals. The Barlow is strange looking even for a Russian and very "short". I was able to check out the Barlow and was pleasantly surprised to find that it provides excellent images. In fact, it seems to actually improve some eyepieces! Screw in moon and solar filters are provided along with a prohibition against using the solar. In fact, pointing the scope at the sun is a no-no at any time, as it will damage the corrector assembly (secondary). I would rather the scope be provided with the clip on filters of the TAL2 and TAL-M.
Here is a summary of the advantages of the TAL200K:
1. No chromatic aberrations
2. Quick cool down
3. No dewing or delayed dewing - no dewcap required
4. Very high quality, low cost (all spherical)
5. Integrated system, mount, eyepieces, all supplied
6. Sit-down observation
7. High image quality
8. Flat photographic field
9. Bright images
10. Compact size.
The German Equatorial mount is specifically designed for this telescope. The Pedestal is reinforced with heavy gauge collars at both ends, is 32" high and the head adds another 10". It weighs in at 44lbs. I have not actually done it but I believe the JMI DSC encoder kit will install on it with no problems. It is not as well built as the massive TAL2 mount, not having tapered shafts.
The Russian clock drive runs on 12VAC, a transformer is provided. An on-off switch is on the motor housing and another on the transformer. A small LED indicates when power is applied to the motor. I like the Russian motor, in fact, I have asked Sovietski to send me the Russian parts they removed when installing the Hurst US motor and I plan to "unmodify" my TAL 2 mount. The mechanical setting circles are useable but slightly smaller than the ones on the TAL2. Like the TAL2, the RA circle is labeled backwards (sun time) and I simply made some replacement labels and applied them.
The head has the dual clutch system of the TAL2 mount with a 180-tooth worm (ring) gear. This means that you can use the slow motion RA knobs or simply push the OTA where you want it, no unlocking required. The Declination axis has a tangent arm with 360-degree rotation and a +-4 degree vernier knob. All controls are easily reached while the user is seated in the viewing position.
Observations(conditions never better than visual Mag 4.)
On the first night a quick peek between the clouds allowed me to set up on the moon and align the Rigel Quickfinder and finder scope. I spent only a few seconds there and jumped to Saturn because it is out from behind the trees. (I have to wait for the moon and Jupiter).
Without a doubt, in spite of the close presence of the moon, this is the best view of Saturn yet. I can see 4 moons and the rings are stunning! I don’t know how to explain this visual presentation except to say it’s bigger and brighter than any scope I have owned. Lots of surface detail, cookie cutter rings and beautiful orange creamsickle color shading.
I continue to be amazed at the brightness of this scope. Every scene I tracked was filled with specks of light, stars and moons. There seem to be twice as many objects visible in all my familiar scenes. This is making it difficult to describe the view as I am seeing unfamiliar patterns. Saturn was floating in a cloud of moons and stars, much more so than I have seen before. Initially I thought I saw 7 moons, with 4 or 5 just outside the rings, wrong of course, but that was the raw count. In addition to that 7 there were about 6 or 8 other specks in the 39’ field. There was too much turbulence to judge the rings or planets disk.
Saturn and Jupiter are so bright that I feel I need to try a neutral density filter on them, especially Jupiter.
There is a tendency for ghosts to show up. This seems to be aggravated by individual eyepieces. It is worse in wide-angle eyepieces than Plössls. These ghosts are not objectionable because they only show when the eye is off center. Once I am in position, they go away.
M42 was spectacular despite the haze that had moved in by the time is high enough to observe. For the first time I saw 5 stars in the trapezium. I saw much more nebulosity than ever before. It was everywhere I looked in Orion. I also saw many unfamiliar stars in the area of M42.
The 200mm f/10 Klevtsov is definitely sharper than the 235mm f/10 C-9.25 SCT.
At no time, with any eyepiece, have I seen any coma or edge distortion at all. There is no focus shift; the focuser is external, and no mirror flop. I traded my 2" 32mm UO König II for the same EP in 1.25". That eyepiece would not come to focus until I pulled it out of the focuser a smidgen. I was unable to get my GRO/LOMO straight through binoviewer to come to focus.
I cannot describe the stars as pinpoint. They are not the blobs of the big SCT, about the same as the M603. I am pleased with this fact. The colors of all objects are very good, as good as the M603 and the TAL2 but much brighter.
But the image is so BIG! And bright! I am at a loss to explain!
There is some field curvature when wide-angle eyepieces are used. I can focus a star at the edge of the field and need to refocus when I move it to the center. This is a characteristic of the eyepiece, not the scope. No coma was observed.
M42 - Trapezium - lots of nebula visible, very bright greenish gray, more striations or streaking then I remember from previous observations. Saw E star and detected a hint of F. All stars very white in color.
44-i Orionis - triple star, 2.8,7.3 11.4" (NSOG) - saw AB&C stars. A star white and B & C stars had more color. B was yellowish and C bluish. This was an accidental observation, I didn’t realize it was a triple until later when I looked it up in NSOG.
M44 - Beehive Cluster - Surprised as the whole cluster seemed to fit into my FOV with the 1.25" UO König II. Also surprised at how good it looked in my finder scope. All stars white or close to it, I did not spend time here as I was headed for M67.
M67 - Brightest star supposed to be 9.69v. Saw about 50 stars all pinpoints of white light. This is the very first time I have observed M67 in a telescope, previously in 20x60 binoculars only, so I have little to compare it with. Last season I spent weeks looking for M67 star hopping, this time I found it right away with DSCs. M67 brightest in 15mm Kellner and 26mm Russian Plössl.
41- gamma Leonis - Algebia - a favorite. - Good split, lots of black showing between the pair, both stars straw yellow. 2.2,3.5 4.4" 127° (NSOG). Best at 124x, 14mm LOMO/GRO SWA. Very pretty despite air movement.
M66 - Galaxy - This was my first telescopic galaxy back in March with the C-9.25. It is easy to identify due to two "pointer" stars. I was a bit surprised that I could see it at all with the only fair condition of the sky.
Ursa Major - Mizar & Alcor. took a spin around the Big Bear. Sketched in 5 very white stars, the Mizar double and Alcor and two field stars forming the third leg of a triangle. The faintest star is m11v according to the NSOG. Very pretty, like a dazzle of cubic zirconias sprinkled on a black rug.
Like my other scopes, the Klevtsov comes in a cabinet grade Baltic Birch plywood case with black hardware. The entire scope goes fits inside, making this a big case. An engraved military looking plaque on the outside identifies the contents and a "roadmap" is pasted on the inside of the lid. This case arrived slightly dinged as it was not packed in a shipping crate on some leg of the trip and a shipping label was plastered directly on the wood. It is still quite good looking and will clean up nicely.
As compared to other scopes I’ve owned and used in the past year:
C-9.25 — Klevtsov is heavier and has sharper images with more detail, especially on planets. The C-9.25 uses standard accessories but the finder and mount are dismal compared to the Russian. C-9.25 requires collimation, has focus shift and mirror flop, the TAL200K none. The C-9.25 mounting arrangement (dovetail bar) is a bit flimsy in my opinion and only half of the connection comes with the OTA.
M603 — TAL200k is much, much brighter, as sharp, not nearly as portable, a better buy unless you want a birding scope, better finder, no dew cap required ($100 more for M603 and is required.) Collimation of M603 primary and secondary required. M603 OTA comes with complete dovetail system and superb baffling, even the finders dew cap is baffled!
The TAL200k is restricted to 1.25" eyepieces.
TAL2 — The Klevtsov lets you sit down and see more. The TAL2 comes with more accessories. If you can live with 150mm the TAL2 is still the best buy in a telescope that I know of. The TAL2 has wider FOV, solar projection screen and does prime focus astrophotography without any modification (unlike other Newtonians).
Both Russian scopes come with excellent eyepieces, filters, Barlows and cabinet grade storage cases. Both have motor drive in RA dual RA clutches and pedestal mounts. The TAL2 mount can carry much larger scopes than the TAL2. Both Russians have very smooth (1/10 wave) mirrors.
Orion Skywatchers (100 and 120mm) the Klevtsov offers clean color and no distortion. The 100mm f/5 in particular has a lot of false color. The refractors have wider and much wider FOV, but I find it easy to settle for binoculars in this regard.