The scope's flaws are as expected. Still, it's a classic, and insanely cool! Looking at the mounts of the day, the increased steadiness must have somewhat offset the degraded image, but not much. Optically, sounds as though it's like having a good, but not great, 60mm that nevertheless has the resolution of a 3-inch. Still, it's a quirky favorite of mine.
Unitron 131-C
Started by
Dave M
, Mar 02 2013 11:12 AM
279 replies to this topic
#27
Dave M
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Posted 03 March 2013 - 10:09 AM
One could "assume" that might be the case.
The mirrors look in excellent condition given their age.
Since they are in such excellent condition i have no plans to have modern coatings applied.
The mirrors look in excellent condition given their age.
Since they are in such excellent condition i have no plans to have modern coatings applied.
#28
Joe Cepleur
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Soyuz
Posted 03 March 2013 - 11:41 AM
A lot goes into choosing a telescope, from the expectation of what one might see, to the ease of carrying it outside, to the ineffable pleasure of using it. All told, the folded Unitron is one of the greats, a good-sized refractor in the ultimate grab-and-go package, surrounded in the glow of history and ingenious design. Congratulations!
#29
Dave M
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Posted 03 March 2013 - 11:55 AM
Thanks! Joe, i couldnt agree more, very well stated. 
#30
starman876
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Nihon Seiko
Posted 03 March 2013 - 12:22 PM
That small box is for the Unitron 80mm spotting scope.
#31
starman876
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Nihon Seiko
Posted 03 March 2013 - 12:24 PM
And if you are interested you can, out of two of those spotting scope boxes, make a box that will hold the 131C. If you would like pictures of how I did it just ask. 
#32
starman876
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Posted 03 March 2013 - 12:26 PM
Exactly why I am planning to replace the mirrors in one of mine to see if I can improve the performance of the 131C.
#33
Terra Nova
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Posted 03 March 2013 - 12:29 PM
Precisely why I like the thru-put of a straight thru design coupled with a quality prism. No mirrors (I don't smoke) 
Terra
Terra
#34
starman876
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Posted 03 March 2013 - 12:36 PM
This was Unitron attempt to counter the high end shorter focal legth APO's. I always wonder what would have happened if they would have started making APO telescopes. I do know they attempted to start selling telescopes again, but in order to compete with price market were obtaining products out of China. However, they could not find a source to be able to produce the quality that people were expecting from Unitron so they left the telescope market completely.
#35
Dave M
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Posted 03 March 2013 - 12:37 PM
Thanks! for the ID on the Unitron box Johann.
Yes, please do post some pictures of you box here, ide love to see them.
Yes, please do post some pictures of you box here, ide love to see them.
#36
xavier
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Posted 03 March 2013 - 12:45 PM
Congratulations with your new Unitron. Great find.
Is one of the few missing in my collection.
Is one of the few missing in my collection.
#37
Dave M
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Posted 03 March 2013 - 12:49 PM
If you do replace them ide be interested in your results.
I dont have any imediate plans on replacing mine but who knows, i could be tempted at some point.
I dont have any imediate plans on replacing mine but who knows, i could be tempted at some point.
#38
starman876
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Posted 03 March 2013 - 01:01 PM
I would think they are at least 1/10 flats. I am not sure it I ever saw any specifications on the mirrors. Considering the wavefront on the objective and 1/10 mirrors I would be surprised it it comes close to 1/4 at the eyepiece. Anybody else have any opinions on this?
#39
Dave M
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Posted 03 March 2013 - 03:33 PM
Here`s a shot of the objective, apparently mine is also one of the rare green tinted ones, see the next to last page, and last page in this thread.
http://www.cloudynig...4715419/page...
His is marked with a C531 on the lens cell, mine is marked C540.
Thought that was rather interesting..
http://www.cloudynig...4715419/page...
His is marked with a C531 on the lens cell, mine is marked C540.
Thought that was rather interesting..
Attached Thumbnails
#40
mustgobigger
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Posted 03 March 2013 - 04:37 PM
I am going to do some testing
With mine when the weather gets a little better.
I think mine will blow away any
60mm let alone 55mm as stated
Above.
maybe ill try a photo light meter
At the eyepiece between mine and
A 60mm.
No one will make me believe
It compairs to 55mm.
I am so swamped it might be awhile
Before I get a chance to test but
I will do that.
I get great views with mine and
No way any of 50 or more 60mm
Scopes I have viewed through
Match it.
With mine when the weather gets a little better.
I think mine will blow away any
60mm let alone 55mm as stated
Above.
maybe ill try a photo light meter
At the eyepiece between mine and
A 60mm.
No one will make me believe
It compairs to 55mm.
I am so swamped it might be awhile
Before I get a chance to test but
I will do that.
I get great views with mine and
No way any of 50 or more 60mm
Scopes I have viewed through
Match it.
#41
starman876
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Posted 03 March 2013 - 04:55 PM
It is always fun to read comments from people who have never used the equipment they are commenting on. Wonder if any new scientific discoveries would ever even been thought of if enough people were critical like that. We might still be reading by candle light.
#42
Terra Nova
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ISS
Posted 03 March 2013 - 05:54 PM
Hence the smoke.......... And mirrors comment 
#43
Dave M
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Posted 03 March 2013 - 06:08 PM
Thanks! xavier
#44
DAVIDG
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Posted 03 March 2013 - 06:33 PM
The resolution won't be effected by the mirrors only the brightness of the image. With fresh standard Al coatings, reflectivity is about 88% so with two mirrors your down to 77%. If you use a star diagonal it's thru put is also around 90% so your down to 70%. It is the same when you use a Cassegrain with a star diagonal as well.
The mirrors are small so to have them enhanced coated won't cost that much. What is more critical is the flatness, especially for the mirror directly behind the objective. They both should be good to 1/10 wave for the best performance. I would test them before replacing them and/or recoating them. It's an easy test and you can get a good understanding of the surface flatness by using a small optical flat of known quality. Surplus Shed has small flats that are good 1/20 wave and also a couple at 1/10 wave that under $20.
- Dave
The mirrors are small so to have them enhanced coated won't cost that much. What is more critical is the flatness, especially for the mirror directly behind the objective. They both should be good to 1/10 wave for the best performance. I would test them before replacing them and/or recoating them. It's an easy test and you can get a good understanding of the surface flatness by using a small optical flat of known quality. Surplus Shed has small flats that are good 1/20 wave and also a couple at 1/10 wave that under $20.
- Dave
#45
Joe Cepleur
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Posted 03 March 2013 - 08:13 PM
It is always fun to read comments from people who have never used the equipment they are commenting on. Wonder if any new scientific discoveries would ever even been thought of if enough people were critical like that. We might still be reading by candle light.
Using Classic telescopes is the realm of astronomers who are both dreamers and doers, who often research rare items that they may never see in person, and then buy and use what they can both find and afford. Whether that is true is a fair question, so I've started a thread asking about people's motivations.
In my case, I have never seen a Unitron 131-C, yet according to DavidG's post, my speculations based on the physics were spot-on. I think they were also misunderstood. If the actual brightness MustGoBigger measures shows that he has both the necessary resolution of a 75mm objective and better light throughput than a 60mm or 55mm, that will speak to the excellent quality of his scope's mirrors, not to a flaw in optical theory.
I'm a Nerd. I love physics. I do not feel that others are obliged to share my interest, but can say that what makes a Nerd a Nerd is not an elitism based on understanding calculations, but an aesthetic and egalitarian response to the wonderful truths those calculations reveal. I'll further posit that scientific discoveries are never made by people who restrict their thoughts to realms they know. They are made by those who see what they know appear in something new, and leverage that to discover further qualities in the new. If we'd rather read by candle light, we should invent a world where people restrict themselves to ever manipulating only what they already know, a dull world indeed.
Because most of us will never see most of the wonderful telescopes discussed in this forum, I hope we'll encourage the dreamers to dream, to ask, to speculate wisely, and those who know from experience to confirm the expanding knowledge. If, for fear of being razzed or any other reason, people were afraid to post about equipment they have never seen, Classic Telescopes would become a sparse forum indeed.
I've occasionally seen, but never driven, a Ferrari. May I be forgiven for saying I think it's a wonderful car? The Unitron 131-C fascinates me, despite that I've never seen or used one. If ever I see one for sale at a price I could afford, I'll buy it -- and then I'll post about it for my fellow dreamers, and invite them to my star parties to try it. A welcoming attitude expands everyone's knowledge.
#47
Dave M
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Posted 03 March 2013 - 09:40 PM
Let me guess, plain, buttered, carmel and cheese.. 
#49
starman876
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Nihon Seiko
Posted 03 March 2013 - 09:55 PM
pics of 131C box made from spotting scope boxes
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#50
starman876
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Nihon Seiko
Posted 03 March 2013 - 09:59 PM
pic 2
I did not cut the wood for the cradle to hold the scope in place, but for now it functions and protects the scope. I have the original boxes with the other 131C's I have so I have a good model. Nor sure if I will leave the extra handle on the box.
I did not cut the wood for the cradle to hold the scope in place, but for now it functions and protects the scope. I have the original boxes with the other 131C's I have so I have a good model. Nor sure if I will leave the extra handle on the box.
Attached Thumbnails
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