Dave Trott
Dave Trott
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Confusing Catadioptric Cassegrain Telescopes
There are many possible varieties of Catadioptric Cassegrain telescopes. Most of them attempt to save on the manufacturing cost by using spherical optics. Spherical mirrors rather than parabolic or elliptical or hyperbolic ones are much easier to make and less expensive. The same applies to lenses.
Here are several possible versions. I compare them with one another. However, my conclusion as to their performance is only valid for these particular examples and should not be generalized to all such scopes. For example, the Maksutov is a well-understood and quite effective design that nearly always produces a superb image despite the rare poor example shown in this video.
Here are my videos about these scopes individually:
Kenko 100mm Maksutov: ua-cam.com/video/9_mFbd0vQzU/v-deo.html
Spacia 100C: ua-cam.com/video/qQGLUt6Ry5w/v-deo.html
Meade 2040: ua-cam.com/video/GvLapqJwkRo/v-deo.html
Vixen VMC95L: ua-cam.com/video/HnzW7DHyiIk/v-deo.html
My video about the C5: ua-cam.com/video/yyQfl06Cdk8/v-deo.html
There are also several versions of Catadioptric Newtonians including Jones-Bird telescopes like the Comet Chaser. Most of them are a horrible mutilation of the original design where they move the corrector from the secondary to the inside of the focuser. This saves the manufacturer a lot of money. One common example is the Jason Comet Chasers and similar scopes. The resulting toy is usually impossible to adjust and is a typical cheap piece of junk. But the CX150 and a maybe a few others implemented the original brilliant design properly. This is a very fine telescope! Manufacturers can take a nice optical design and make it into a very poor telescope.
Here's my video about the all spherical Jones-Bird Comet Chaser scopes. They are highly dysfunctional but still have a lot of charm in some iterations:
ua-cam.com/video/ZlUDJdM7WYY/v-deo.html
Here’s my video about the CX150: ua-cam.com/video/UfuRwm-sE5s/v-deo.html
Another review of the Vixen VMC95L: www.scopeviews.co.uk/VixenVMC95.htm
Rod Mollise has a superb guide to classic SCT telescopes: uncle-rods.blogspot.com/2009/05/how-much-is-that-kitty-in-window.html
Переглядів: 3 030

Відео

Kenko 100mm Maksutov
Переглядів 4426 місяців тому
This 100mm Maksutov seems to be pretty rare in the US. The scope is not very high quality but the mount is remarkable. It seems to be identical to the mount for the highly regarded Pentax J60 except that this one is for a tabletop. Pentax J60 Video: ua-cam.com/video/qb7S5YsHFsk/v-deo.html My video comparing this to other Classic Catadioptric Cassegrain scopes: ua-cam.com/video/-1lg8y1oBTs/v-deo...
Kenko Spacia 100C Telescope
Переглядів 8486 місяців тому
The Kenko Spacia 100C is one among many possible varieties of Catadioptric Cassegrain telescopes. This particular design involves an assembly of lenses buried in the baffle tube. It is an unusually fast telescope for a Cassegrain at f/8 and has a very large central obstruction. Despite all the compromises this particular example functions well. I don’t think I will recommend this type of scope ...
Meade 2045 Classic Telescope
Переглядів 1,2 тис.6 місяців тому
The Meade 2045 is a 4 inch Schmidt Cassegrain telescope which was available new in the late 1980’s. It was comparable to the Celestron C5 though a little smaller and less expensive. Like the C5 it was almost a clone of a larger 8 inch version. The big brother to the Meade 2045 is the Meade 2080. It is a simple and effective scope in a relatively compact package. It’s really not much bigger than...
Vixen VMC95L Telescope
Переглядів 1,1 тис.6 місяців тому
This is a 95mm telescope. It is called a Maksutov but is not the usual Maksutov design with a deeply curved meniscus in the front, so the name may be technically correct but causes a lot of confusion. Performance of the scope is good but not spectacular. It’s as cute as can be with all the doodads and creamy white pain job. My video on the C5: ua-cam.com/video/yyQfl06Cdk8/v-deo.html My video on...
C5 Classic Telescope
Переглядів 9717 місяців тому
The C5 is a smaller version of the C8 classic telescope. Like the C8 it is a Schmidt Cassegrain telescope which is a nice design for putting a large aperture into a small package. The C5 is a highly regarded telescope among amateur astronomers and they usually have very good optics. The C5 is a nifty balance of portability and reasonably large aperture. C8 Classic Telescope: ua-cam.com/video/1A...
C8 Classic Telescope
Переглядів 3,7 тис.7 місяців тому
The Celestron C8 telescope is one of the most popular scopes in the world because of its many attributes. It offers fairly large aperture in a small package at a reasonable price. This video shows an early classic orange version of the scope with minimal bells and whistles. I also compare it with a modern version of the same scope and show some much more recent applications! The C5, close relat...
Deep Sky Astronomy from my Light Polluted Backyard
Переглядів 2,6 тис.7 місяців тому
This video show how to observe faint deep sky objects when you are in a light polluted location. It’s easy to observe the Moon, planets and double stars from an urban location. Not so easy to see faint galaxies and nebulae. The equipment and techniques I use in this video are fairly straightforward but a bit expensive. And the results are not as good as using a large aperture telescope at a pri...
Alternate Mounts for a Questar
Переглядів 6779 місяців тому
This is a look at the Meade 883 and the Meade 884 mounts and their application in holding a Questar 3 ½ inch scope. Recently I acquired a Quantum 4, a close cousin to the Questar 3 ½ inch telescope. I tried several alternative mounting systems before I ultimately designed and made an entirely new mount. Some of my experiments involved the Meade 883 and Meade 884 mounts. These mounts were design...
Questar TriStand
Переглядів 9949 місяців тому
The Questar TriStand is a mount for the Questar 3 ½ inch telescope. It is meant for seated observing. There is a taller version of the mount intended for standing viewing called the AstroPier. These have the same mechanics and legs. The only difference between them is an additional foot or so of height off the ground. I start the video with a demonstration of the functionality of the TriStand m...
Making a Miniature Questar
Переглядів 8529 місяців тому
This video shows some details on the construction of my half-scale Questar 3 ½ inch Classic Telescope. The model is a fully functional semi-replica, though it does not have all the features of the original and does not meet the impeccable quality standards of the original. It is meant for display and not for daily use. If you have not watched the general overview of the model you will want to v...
Questar Half Scale Model
Переглядів 7809 місяців тому
This is a model of a Questar 3 ½ inch Classic Telescope. It is done at approximately half the size of the original (60%). The model is a fully functional semi-replica, though it does not have all the features of the original and does not meet the impeccable quality standards of the Questar 3 ½ inch scope. Long considered to be the Rolls Royce of small telescopes, the Questar is renowned among a...
Portable Classic Telescopes for Astrophotography
Переглядів 63210 місяців тому
This is a comparison of three classic telescopes that were marketed for portable “Hoshino” (star) astrophotography. These three scopes were remarkable innovations when they were new in the 1970’s and 80’s. The Takahashi TS-65P had the first integrated polar alignment scope. That was a significant development as demonstrated by the fact that nearly all modern scopes have that setup. It made astr...
Vixen SA70S Classic Telescope
Переглядів 83810 місяців тому
The Vixen SA70S was marketed in the late 1970’s as a competitor to the Takahashi TS-65P. It has an additional 5mm aperture and many of the same characteristics. It was designed to be portable and small for expeditions away from city light pollution. Obviously, Vixen wanted to capitalize on the popularity of the renowned Takahashi scope. They may have been late to the party, though, as these sco...
Goto Kogaku Single Axis 78 Telescope
Переглядів 94010 місяців тому
This is the Goto Kogaku “Single-Axis” 78mm telescope from about 1952. The optics are superb and it is quite rare as are all the early Goto Kogaku scopes. This one features a unique mount with a singularly beautiful casting. It is completely breathtaking but how well does it work? The elegant off-center structure causes some interesting issues when it comes to using the mount! This scope stands ...
Goto Kogaku Mark X 125mm
Переглядів 84711 місяців тому
Goto Kogaku Mark X 125mm
Goto Mark X 65mm Classic Telescope
Переглядів 61611 місяців тому
Goto Mark X 65mm Classic Telescope
Goto Mark X Portable Photographic Mount
Переглядів 18711 місяців тому
Goto Mark X Portable Photographic Mount
Goto Mark X Modifications
Переглядів 24911 місяців тому
Goto Mark X Modifications
Modular Telescope Mounts
Переглядів 49011 місяців тому
Modular Telescope Mounts
Goto Mark X 80mm Classic Telescope
Переглядів 55211 місяців тому
Goto Mark X 80mm Classic Telescope
Pentax 75 EDHF Classic Telescope
Переглядів 1 тис.Рік тому
Pentax 75 EDHF Classic Telescope
Goto Kogaku Telepac Classic Telescope
Переглядів 462Рік тому
Goto Kogaku Telepac Classic Telescope
Porter Garden Telescope Replica
Переглядів 1 тис.Рік тому
Porter Garden Telescope Replica
Classic Borg Telescope in a Tube
Переглядів 747Рік тому
Classic Borg Telescope in a Tube
Vintage Star Pointers
Переглядів 358Рік тому
Vintage Star Pointers
Satellite Scopes Part 5
Переглядів 416Рік тому
Satellite Scopes Part 5
Newton's Telescope Replicas
Переглядів 1,3 тис.Рік тому
Newton's Telescope Replicas
Making a Replica of Newtons Mirror
Переглядів 937Рік тому
Making a Replica of Newtons Mirror
Model of Newtons Telescope
Переглядів 451Рік тому
Model of Newtons Telescope

КОМЕНТАРІ

  • @ronaldrubin4778
    @ronaldrubin4778 5 років тому

    Just finished watching the video and found it very informative. I was interested in the segment where you added an adapter to the photo port on the ETX 90. I have been looking for one just like the one in the video and cannot find one. I have a 45 degree prism and I do not need to but the Meade 932 prism, I just need an adapter as shown in your video. If anyone knows the adapter he used and where to find one I would appreciate a reply on this site. Thanks!

  • @stephen6whitehead398
    @stephen6whitehead398 5 років тому

    I remember my two tal reflectors with fondness.I owned both the 110mm and the 150mm.The optics aren't just adequate they are superb,pinpoint star images,very nice clear views on planets.I wouldn't mind getting either ones of these back.I'm not fond of reflectors but these were superb.The mounts and pillars were unmovable,no shakes at all.I never managed to get hold of the 100mm refractor but i bet that was a stunner.

  • @michaelschnittker7388
    @michaelschnittker7388 5 років тому

    Would love to know the gears used in the drive. Would Boston Gear have equivalents? Would love to try to build something similar for my scopes, can't think of anything more elegant! Thank you!

    • @davetrott6046
      @davetrott6046 5 років тому

      These are standard Boston Gears right from the catalog. They tell you which gears work with each other in the catalog.

  • @michaelschnittker7388
    @michaelschnittker7388 5 років тому

    Great video! I am working on a tripod for my 6" f/10 and it gave me a lot of good ideas! Thank you!

  • @michaelschnittker7388
    @michaelschnittker7388 5 років тому

    Excellent. I have an 8mm and 1.5" focal length eyepieces marked "J.W. Becker Inc.". They work well for what they are on my longer f ration scopes. Love the old scopes!

  • @GoldSrc_
    @GoldSrc_ 5 років тому

    Wow, that C90 is so cute. Thanks for sharing.

  • @danielnicholson6174
    @danielnicholson6174 5 років тому

    hi Dave I was wondering what you favourite scope has been to look at Jupiter and mars in your opinion, and have any of your refractors shown you the shadings within the great red spot which I has experienced with a tak mt160 kind regards.

    • @davetrott6046
      @davetrott6046 5 років тому

      I have no one favorite. Each scope has it's good and bad points. And the image quality is only one attribute. If I had to pick just one it would be my Alvan Clark 3 inch. What a scope!

    • @danielnicholson6174
      @danielnicholson6174 5 років тому

      @@davetrott6046 thanks for your reply Dave sounds like a great scope, i have tried a fs78 briefly on Saturn and had a nice view but haven't had a great view of Jupiter yet as the seeing has been poor and it's been too low on the horizon at the moment down here in Australia. Great channel keep up the good work.

  • @conquerthemoon4
    @conquerthemoon4 5 років тому

    Very Nice scopes...I have a unitron 40mm Model 127 and its missing the focuser.....do you have one you can sell ?

  • @nicholasdisabatino1697
    @nicholasdisabatino1697 5 років тому

    these should be quite nice for planetary viewing.

  • @40belowful
    @40belowful 5 років тому

    Hey so Dave how many finger prints did you get on the optical glass sticking your hand in there to swivel it :) ha

  • @иванепифан-к8ж
    @иванепифан-к8ж 5 років тому

    Oh, thank you ! Interesting to See the telescopes that disappeared firm "Merz and Mаller" !

  • @иванепифан-к8ж
    @иванепифан-к8ж 5 років тому

    Hello, Mr. Dave Trott . From your diversity run eyes.))))) I'm shocked. Everything is fine but in the line of telescopes Maksutov no telescope TMSH (1946 release) it was one of the first telescopes of this system , produced for students. (of course in scanty quantities that the about 15 thousands of) www.astronomer.ru/publications.php?act=view&id=204

    • @davetrott6046
      @davetrott6046 5 років тому

      This is a fascinating read about small Russian School Maksutov Telescopes and I highly recommend it to my viewers. Google Chrome translates it pretty clearly. These scopes are the earliest Maks. Wonderful!

  • @Pete391
    @Pete391 5 років тому

    Its strange since I have had many of the coulter odyssey telescopes since 1985.....I never saw these advertised anywhere myself and only now hearing about them..

  • @Thomas_Deering_King
    @Thomas_Deering_King 5 років тому

    Thanks for making this video, Dave. I like the way your mind works.

  • @guepit
    @guepit 5 років тому

    yo tengo uno igual con la misma caja al final con 6 lentes....

  • @chrisshelton3504
    @chrisshelton3504 5 років тому

    I belong to a 60mm telescope group that I’m sharing this with! Thank you so much for your knowledge, time, and enthusiastic presentations!

  • @wetcanoedogs
    @wetcanoedogs 5 років тому

    best youtube unboxing I have see in awhile!

  • @cosmolocus6545
    @cosmolocus6545 5 років тому

    Amazing!

  • @claudiostar71
    @claudiostar71 5 років тому

    A little jewel. Very nice. Hugs to Dave

  • @rlewis1946
    @rlewis1946 5 років тому

    Hello Dave, Thank you for your videos! I very much enjoy these informative episodes; seeing instruments rarely seen these days. Please continue posting these fascinating stories. Roy Lewis Buffalo, NY

  • @paulsunday6720
    @paulsunday6720 5 років тому

    Russia is also looking!

  • @sonfire1
    @sonfire1 5 років тому

    I have same kind of small spotting scope made in Russia, you can see below video of mine ua-cam.com/video/ZA7BP6U492k/v-deo.html

  • @moschetto58
    @moschetto58 5 років тому

    Thanks Dave, great job!

  • @MrOtterdude
    @MrOtterdude 5 років тому

    As usual, you did a great job on the replicas! Thanks for the video!

  • @cosmolocus6545
    @cosmolocus6545 5 років тому

    Curious and rare telescopes these Unitron RFT. Good question: roles have been exchanged short tube-long tube. At present, there is a great demand for short telescopes, especially for digital astrophotography. Among modern visual observers are also more fashionable. The massive introduction of ED glass and its massive publicity have favored this issue. Good work with the replicas!

  • @40belowful
    @40belowful 5 років тому

    cool stuff Dave:)

  • @szaki
    @szaki 5 років тому

    New Mead ETX is made so, the OTA can be removed very easy! Even other OTA can be mounted between the fork!

  • @ferretface8782
    @ferretface8782 5 років тому

    I just picked up a vintage one from Goodwill for $40. It says made in Barrington, N,J. I'll keep the bar code placard on it that says 'U.S. GOVERNMENT PROPERTY'... kinda cool xtra. Mint condition w/ strap and base. Only has the 28mm lens. I'm going to 3d print an adapter for my dslr camera(16MP/36x optical zoom). Might need to fashion up a hose to go in through lens opening to suck up some dust that has settled on the bottom mirror. ANY SUGGESTIONS are welcomed... thanks for the video. This thing is beautifully unique.

  • @40belowful
    @40belowful 5 років тому

    Wow!! nice find Dave and very rare:) I had a brand new 132-c with green lens from 1981. sorry I sold it. Bought it from untron direct:) My lens cell had a c-### on it. serial number? and unitron on it. It yielded razor sharp image's. I was told when I bought mine in 1981 from peter at unitron that 25 4" models made and 100 3" models made. Also I remember my trypod legs were heavier and had a wood tray spreader

  • @soarbooks
    @soarbooks 5 років тому

    Thanks! I have never had a chance to handle the early ETX non-ElectronicControl fork mount, and your explanation of the knobs and their function is very helpful.

  • @Muesli711
    @Muesli711 5 років тому

    Nice review and scopes! I have the original version: the Vixen made Tasco 9vr. Slightly shorter than the 999vr and with no tripod.

  • @RaysAstrophotography
    @RaysAstrophotography 5 років тому

    Nice stuff Dave!

  • @fnersch3367
    @fnersch3367 5 років тому

    Those old Edmunds had 0.917" eyepiece barrels. The Japanese used 0.965" barrels.

  • @fnersch3367
    @fnersch3367 5 років тому

    I had the Edmund 3" f/10 scope with a white cardboard tube. 3X paper finder. That was a good scope. Bought it in 1963 for $29.95. Had to save my money for a long time (sacrificed many candy bars!). Still have the tripod and mount after all these 55 years.

  • @fnersch3367
    @fnersch3367 5 років тому

    I read Paul's books when I was a kid. Very influential. His stuff was so readable.

  • @victoralexander848
    @victoralexander848 5 років тому

    my3tp-57 was supplied in a wooden case and a leather carry case they were made by several ussr co.base on zeiss jena design the company they took over after the war in east germany before zeiss fled from jena to oberkochen that is why you had such great binoculars from the ussr and east germany they were basically zeiss jena hence that why there was zeiss west and zeiss east gemany be fore the fall of the berlin wall and the fall of the ussr

  • @fnersch3367
    @fnersch3367 5 років тому

    They still use solar filters in Russia as they expect people to be reasonable intelligent about personal safety. I used them for decades with no harm (now, I use an Ha scope). They are not a litigious society like the US.

  • @fnersch3367
    @fnersch3367 5 років тому

    While watching this I bought a Lomo 30mm from a Lomo factory worker in Russia (Ebay). Lomo liquidated in 2000. I wonder if Intez is still around?

  • @fnersch3367
    @fnersch3367 5 років тому

    The Russians & Japanese got their inspirations from Zeiss and the German school of engineering.

  • @fnersch3367
    @fnersch3367 5 років тому

    The Unitron mount uses a synchronous motor like the Questar. Your pedestal mounted equatorial uses a driven system invented after the Civil War (1870s). Standard AC & synchronous motors were another generation away at this time. Another interesting fact is that the basic gearing system in that box was invented 2200 years ago by the Greeks in the Antikythera Mechanism. That's a fine piece of mechanics you have there. Thanks for sharing this.

  • @fnersch3367
    @fnersch3367 5 років тому

    Wow!! What a masterpiece! I saw a 4" Unitron full dresser with Garrish drive recently that went for 30K. Such instruments deserve a nice 6-8 foot dome in the classic style.

  • @fnersch3367
    @fnersch3367 5 років тому

    Your mount is fantastic. I so wish I had one like this for my 67mm, F/16.5 mahogany tubed Dollond refractor made in 1795. I want to use it at public outreach events.

  • @fnersch3367
    @fnersch3367 5 років тому

    The two scopes have focusers like my 225 year old Dollond. From 1650 to about 1825 this was a common way of doing it. The modern focusers are more stable and can handle heavier loads.

  • @fnersch3367
    @fnersch3367 5 років тому

    I have two of those scopes: The Questar and the Celestron C-90 Astro. Both are very high quality scopes and would recommend either for a small planetary instrument. They are not suitable for deep sky objects however.

  • @fnersch3367
    @fnersch3367 5 років тому

    The 100 in. F/5 Hooker telescope was built from 1915-1917. My grandfather witnessed the opening of this observatory in Nov. 1917. George Ritchey built the mirror & Edwin P. Hubble used it in the 1920s to make several discoveries leading to modern cosmology. The 60 in. F/5 Ritchey telescope was inaugurated in 1908 and was the largest fully functioning telescope in the world until 1917. Ritchey was the greatest American optician living at the time. The LAAS still uses this instrument about 6 times a year. Alvin Clark was Americas greatest optician and manufacturer in the 19th. C. He made brass tubed telescopes like this one up until 1929. Many of his instrument survive to this day and can fetch large sums.

  • @livepolarexnr.1-telescope124
    @livepolarexnr.1-telescope124 5 років тому

    old Telescopes are Quality ....

  • @fnersch3367
    @fnersch3367 5 років тому

    That is cool. About 37 years ago at RTMC someone brought up a 6 in. Goto full dresser refractor on a weight driven pier. This thing weighed a ton. And cost a ton: $65,000. What magnificent views we had with it that weekend (5-1981).

  • @fnersch3367
    @fnersch3367 5 років тому

    Wow !!! I need you to make me a period brass eq. mount for my 220 year old Dollond. I want to take it to our public star parties at Griffith Observatory. We garner 2 million visitors a year. Many look thru our scopes.

  • @fnersch3367
    @fnersch3367 5 років тому

    I have one of those Newton replicas as well. A fun scope to bring to star parties. It helps people to appreciate modern instruments. I use this as well with my 220 year old Dollond refractor. The sphere mount of the Astroscan was invented by one of our club members several decades ago (Norm James). His is driven and can track the stars. The largest I have seen was a 32 in. f/4 at a Mt. Pinos star party in 1978.

  • @fnersch3367
    @fnersch3367 5 років тому

    Interestingly the very early Tascos & Swifts had optics made by Takahashi. Later Takahashi branded scopes became famous for high quality. I had a 1960s Mayflower that possessed these superb optics. I regret I sold it.