Discussion in 'Vintage Telescopes & Equipment' started by Bomber Bob, Nov 11, 2016.
Started by Bomber Bob on Nov 11, 2016 at 8:35 AM
Here's a rare Corrected Dall-Kirkham Cassegrain, the Kenko 125C:
It's a 125mm F8 system with an optical design very similar to the equally rare Mizar Altair 15 where a correcting lens assembly is placed in the primary mirror baffle.
I had my first good viewing session with it last night, which I reported on CN --> http://www.cloudynights.com/topic/555959-kenko-in-a-cracker-jack-box/page-4#entry7529898
An Italian site has a comparison between the 125C and a Takahashi TS65-P --> http://www.dark-star.it/astronomia-articoli-e-test/test-strumentali/kenko-125-c/
In my tests, I compared the 125C with a vintage white tube C5, a 1950s Edmund 4" F15 refractor, and a China-made Celestron PowerSeeker 114 reflector. This is a good compound telescope, and if you find one with the KES mount, $300 or less is a fair price.
Hi Bob -
You might be interested to know that the Carton Optical Industries, in Japan, made the optics for a great many brands sold all over the world. Among these were old Edmund Scientific refractors and the Unitron refractors. Also both Kenko and Mizar. Here's a short Pdf. on this:
_Carton Optical Company.pdf
I almost fell out of my shoes to find that my old 3" F/15 Edmund refractor had the same lenses that Unitron used. I always wished I had a Unitron instead of my Edscorp 3." Little did I know...
Thank you for the info on this Kenko 125C. I find these rare optical telescopes especially fascinating! A very nice find!
So, I have a Kenko 125C, but it is missing the eyepiece. Can someone tell me what size/kind I need to get? I have no idea. Thanks.
It appears to be missing more than an eyepiece. Is this telescope something you're trying to get in good working order for you to use? Where did you come by this interesting looking Cassegrain?The more we know, the better we can assist you.
Oh yes - welcome to A-C, nice of you to join us!
A beautiful looking telescope Bob, thank you for showing it and the links
Do check the dates on the posts, Gabby. All but this last one are from Nov. 2016.
I like when old treads are resurrected like that.
Well, it mostly has all the pieces, but it is not yet put together (obviously). The mount has some missing nuts & bolts, but I just picked some up at the hardware store so that I can put it together. It does have the finder, though it is not pictured. So the only thing missing that is really missing is the eyepiece. I talked to a local astronomy club, and he pointed me to a .965 to 1.25 adapter. But for the actual eyepiece, do you recommend a 13mm? or something different? I don't actually know much about telescopes in general, but thought it would be something fun.
I got it on a free ad listing, so I don't know its history or anything else.
I see on the side of the scope there's gold & blue tag. That likely has the specificatioons of the telescope. Such as the aperture, the focal-length, and focal-ratio. Could you please tell us what it says on it.
Without knowing these details, there's no way to tell things like what magnifications a given eyepiece will have in the telescope. Once we have these specs, then I'll show you the simple mathematical formula used to determing the magnifying-power of the many different eyepieces that you can use in this telescope. There are literally 100's of different eyepieces available a telescope can use - including that Kenko.
D: 125mm / f: 1,000mm
P.S. Sorry, I probably should have created a new thread instead of adding onto this one.
Okay! Now we have the parameters for you to get eyepiece(s)!
The aperture of your Kenko is 125mm. Which is to say a rat's hair under 5-inches at 25.4mm = 1-Inch.
The F.L. is the Focal Length of your telescope. This makes the Focal-Ratio to be F/8, or just F8. We accomplish this by: 1,000mm / 125mm = 8.
Now to find the magnification any eyepiece will result in giving you in the telescope, we do this:
Take an eyepiece that says 25mm - which is it's F.L. (focal-length). Now use this equation: 1,000mm (focal-length of telescope) / 25mm (focal-length of eyepiece) - 1,000mm / 25mm = 40X
So a 25mm EP (Eyepiece) will give you 40X power. That's a good all-round lower-power EP.
How high a 'power' can your telescope be hoped to achieve (before the view goes to blurry-yuck)? The usual wisdom is 50X to 60X per inch of aperture. So 125mm = 4.9-Inch = 245x - 294X. So on nights (very rare) of perfect 'seeing' the Kenko could be pushed up to a rats' hair under 300X.
So a 25mm EP is a good low-power EP. An EP that will give you around 125X would be a good middle-powered EP. And an EP of 8mm would fit this earmark. And an EP of 4mm will soar up the 250X.
Now these are generalizations. There are a great many different types of eyepieces available: wide-field, planetary, super wide-field, etc. And it's up to you to do some reading-up on these and looking at the ads for prices, reviews, pro v. cons - and so forth. And then we can go into the Barlow-Lens, a simple optical-component that effectively doubles the number of eyepieces you have!
I'm hoping Mak will lend an ear to this thread - he's our resident Eyepiece-Nut here, and should be able to assist you better than I in this task. But you now should have the basics for starters!
Welcome to Astronomy!
Thank you so much! That's very helpful.
Hello Kattoone I have a complementary question, do you have a primary interest, specific things you want to look at? It could be something from the list bellow.
- High power planetary observation
- High power moon observation
- Low power deep sky object observation, you have large DSO that will benefit from low a power eyepiece and larger exit pupil like the Veil nebula or the north America nebula.
- Low power wide fields observation, looking at the star fields in the MilkyWay constellations like Cygnus, Lacerta, Cassiopeia, etc they are all very rich in stars.
- Medium high power smaller DSOs like planetary nebulae or some globular cluster that can take medium to high power.
- Low Medium High double star splitting
- Carbon Star observation.
- Sun observation perhaps.
- Comets / asteroid observation.
Kat (if I may call you such?) - All this may seem a pretty steep learning-curve. But I assure you it gets easier in short order! We all go through it - IF we wish to put our telescopes to provide the most amazing things they are capable of providing.
This beginning phase just opens one's eyes to a Universe that goes on forever. Once one catches their breath with some simple math-equations and word-associations under the belt - then the REAL fun begins! Some people, for fun, drive their shiny cars on the highways looking for hamburgers & beer. We cruise the dust-lanes of galaxies looking for oddities in deep outer-space.
I don't know if I can add anything. The OTA seems to be a Cassegrain design.
Although f/8 seems fast for any Maksutov type design. I really don't know anything about modified Dall-Kirkham scopes. What I'm pretty sure of is that when you place any eyepiece directly into the focuser the image will be inverted and mirror reversed. To get an upright image you will need a diagonal of some sort, and to get an upright, non-mirror reversed image, you will need an Amici prism diagonal. Unless the Dall-Kirkham design compensates for this, of course.
Bomber bob has come back.. but I believe the second OP is gone.
Thank you all. As for what specifically I'm interested in looking at, I'm not necessarily sure. My immediate thought was planets, moon, maybe star clusters? Simply because that's all I'm really familiar with at this point. I wasn't really sure what type of capability this telescope has. Thank you for laying out the possibilities. I have some research to do.
Regarding reversed image, I guess I'll have to try it out first to see whether the telescope compensates for it or not. it might. Someone that looked at it seemed surprised that there was another lens in it without the eyepiece...or something like that.
You're welcome. As far as I know the only real way to get an upright and non-reversed image on a refractor or cassegrain is to use an Amici prism diagonal. Not all are ninety degree, but this configuration is the most practical for astronomy as it makes it easier to look vertically up at the zenith and any altitude inbetween. You can get these for smaller barrel sizes than 1.25".
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