Why couldn't a catadioptric or newtonian optical system be used in binoculars? (1 Viewer)

So want a newtonian? Here ya go

http://www.brucesayre.net/#Overview

A Bird Watcher from OT sent me this, and I thought I'd pass it along.

Steve C said:

So want a newtonian? Here ya go

http://www.brucesayre.net/#Overview

A Bird Watcher from OT sent me this, and I thought I'd pass it along.

Click to expand...

Wow! That's an impressive binocular telescope! :t:

Steve C said:

So want a newtonian? Here ya go

http://www.brucesayre.net/#Overview

A Bird Watcher from OT sent me this, and I thought I'd pass it along.

Click to expand...

Wow. Equal to a 40% larger single mirror Newtonian. That is a 30 incher! Egads! Imagine what the Southern Magellanic Clouds would look like through that at a really dark site like Milford Sound on the south island of New Zealand. Even binoculars are awesome at Milford.

etudiant said:

The mirror surface(s) are continually adjusted, primarily to offset atmospheric distortion but also to optimize the figure. A reference star is created with a laser that creates a fluorescing point about 50 miles up, which allows the distortions to be measured and corrected for. The Japanese Subaru telescope in Hawaii has an active secondary which is said to give especially good results. The active optics concept is the key to making larger telescopes, because the distortions brought about by the mirror's own weight limit single mirror sizes.
The James Webb telescope that is expected to succeed the Hubble uses active optics, partially also because the mirror is folded into a small package to launch, so when it unfolds it needs to unfold exactly so much, no more.

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Are you an amateur astronomer or professional?

[email protected] said:

Are you an amateur astronomer or professional?

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Strictly amateur, but have had the good fortune to visit the observatory complexes in Chile and Hawaii in the company of professionals.
Professionally, the interest arises from the aerospace/electronics side, where active and very high resolution optics as well as compatible pointing/tracking solutions are of great interest.

. I said that there is nothing very difficult about making F/2 mirrors if the design requires it.

I have been trying to find out the full specification of the large Maksutov binocular. I remember being told by the maker that the primaries were 12 inch, but I see reference to the binocular being 11 inch aperture. I think both of these can be true as Maksutovs may have oversize primaries. I have not yet established whether the primaries were F/1 or possibly a bit slower. The final F ratio may have been about F/4 or F/5 although I'm not sure of this. His telescopes usually had beautifully made secondaries and relay lenses.

As to the comment about my having read about optics and not having made telescopes.
I am not a telescope maker, I am a telescope user.
I have used over 30 compound mirror telescopes and mirror lenses that have primaries of F/2 to F/2.5.
In addition, my main telescope had the relatively slow F/3.5 12.5 inch thin edge main mirror, with a final ratio of f/14.7. Its larger brother, which is still being used has I think an F/3 primary. It is 16.3 inches aperture.

Unfortunately, the gentleman making the the large Maksutov binocular was in his 80s and was unable to complete the instrument.

. When I say that there's nothing very difficult about making F/2 mirrors, I mean that it is not difficult to somebody or to an organisation that makes these things.
The gentleman making the large binocular made dozens of beautiful compound mirror scopes with primaries of F/2 to F/2.5. I have used some of these.

I would estimate that there are more than 100,000 compound mirror telescopes and mirror lenses that have primaries of f/2 to F/2.5. For the people who make these mirror telescopes and mirror lenses it is not that difficult as they would not be making them and selling them for relatively low prices
Nowadays, you can buy a good quality mirror telescope for about £100 or £200 and mirror lens for £100 or less.

The Japanese mirror lenses in particular are very good.
I have an Optomax 500 mm F/8 mirror lenses that splits both components of Epsilon Lyra using a three times teleconverter and a 10 mm monocular converter. That is, it is cleanly splits real stars of about 2.3 arc seconds separation, and on a normal photographic tripod.
The Nikon, Minolta and Canon 500 mm F/8 mirror lenses are of similar quality.
Similar mirror telescopes are of even better quality.

I also find out now that a British worker was regularly making small optical units with top quality F/1 mirrors for industrial use.

I am not recommending that Maksutov binoculars are a good idea. I was only replying to the question whether such binoculars have been made. The only one that I have seen is the large one mentioned, which was not completed because of old age.
They are not a good idea for normal binoculars because of the complication and the fact that they have narrow fields. They might be interesting as a high-powered binocular, but even then they have to be made to extremely fine tolerances and they are critical as to alignment individually and as a pair.

Neither am I advocating off axis designs.

But discussion of different designs should in my opinion be allowed without personal attacks.

As it happens, I think that the Yukon 30×50 is a magnificent effort. It is a pity that it doesn't have full multi coating and enhanced mirror coatings. It is the most usable 30 times binocular that I have seen.

etudiant said:

Strictly amateur, but have had the good fortune to visit the observatory complexes in Chile and Hawaii in the company of professionals.
Professionally, the interest arises from the aerospace/electronics side, where active and very high resolution optics as well as compatible pointing/tracking solutions are of great interest.

Click to expand...

That would be extremely interesting.

Binastro said:

. I said that there is nothing very difficult about making F/2 mirrors if the design requires it.

I have been trying to find out the full specification of the large Maksutov binocular. I remember being told by the maker that the primaries were 12 inch, but I see reference to the binocular being 11 inch aperture. I think both of these can be true as Maksutovs may have oversize primaries. I have not yet established whether the primaries were F/1 or possibly a bit slower. The final F ratio may have been about F/4 or F/5 although I'm not sure of this. His telescopes usually had beautifully made secondaries and relay lenses.

As to the comment about my having read about optics and not having made telescopes.
I am not a telescope maker, I am a telescope user.
I have used over 30 compound mirror telescopes and mirror lenses that have primaries of F/2 to F/2.5.
In addition, my main telescope had the relatively slow F/3.5 12.5 inch thin edge main mirror, with a final ratio of f/14.7. Its larger brother, which is still being used has I think an F/3 primary. It is 16.3 inches aperture.

Unfortunately, the gentleman making the the large Maksutov binocular was in his 80s and was unable to complete the instrument.

. When I say that there's nothing very difficult about making F/2 mirrors, I mean that it is not difficult to somebody or to an organisation that makes these things.
The gentleman making the large binocular made dozens of beautiful compound mirror scopes with primaries of F/2 to F/2.5. I have used some of these.

I would estimate that there are more than 100,000 compound mirror telescopes and mirror lenses that have primaries of f/2 to F/2.5. For the people who make these mirror telescopes and mirror lenses it is not that difficult as they would not be making them and selling them for relatively low prices
Nowadays, you can buy a good quality mirror telescope for about £100 or £200 and mirror lens for £100 or less.

The Japanese mirror lenses in particular are very good.
I have an Optomax 500 mm F/8 mirror lenses that splits both components of Epsilon Lyra using a three times teleconverter and a 10 mm monocular converter. That is, it is cleanly splits real stars of about 2.3 arc seconds separation, and on a normal photographic tripod.
The Nikon, Minolta and Canon 500 mm F/8 mirror lenses are of similar quality.
Similar mirror telescopes are of even better quality.

I also find out now that a British worker was regularly making small optical units with top quality F/1 mirrors for industrial use.

I am not recommending that Maksutov binoculars are a good idea. I was only replying to the question whether such binoculars have been made. The only one that I have seen is the large one mentioned, which was not completed because of old age.
They are not a good idea for normal binoculars because of the complication and the fact that they have narrow fields. They might be interesting as a high-powered binocular, but even then they have to be made to extremely fine tolerances and they are critical as to alignment individually and as a pair.

Neither am I advocating off axis designs.

But discussion of different designs should in my opinion be allowed without personal attacks.

As it happens, I think that the Yukon 30×50 is a magnificent effort. It is a pity that it doesn't have full multi coating and enhanced mirror coatings. It is the most usable 30 times binocular that I have seen.

Click to expand...

The alignment is what I would worry about. A binocular telescope doubles the complexities. Is this the Yukon you are referring to?

http://www.amazon.com/Yukon-Advanced-Optics-Spotting-Tripod/dp/B0002HBOR4

How to create a new thread

Can someone tell me in simple terms how to post on a new subject. I find the help page impenetrable. I am new to the forum and wish to tell a story about opticron. This should be easy but I saw something about big red buttons in a forum so I went tone at random and could see no buttons.

iancfitzg said:

Can someone tell me in simple terms how to post on a new subject. I find the help page impenetrable. I am new to the forum and wish to tell a story about opticron. This should be easy but I saw something about big red buttons in a forum so I went tone at random and could see no buttons.

Click to expand...

Your best bet would be to go to here http://www.birdforum.net/forumdisplay.php?f=299 if it about Opticron telescopes

or here
http://www.birdforum.net/forumdisplay.php?f=445 if it is about binoculars

and then click on the Big Red Button at the top left of the list of threads that says , New Thread

. No,
. The Yukon 30×50 that I have is essentially perfectly collimated and gives very nice star images. So it is apparently fairly easy for the maker to achieve collimation that is fixed. I suppose there may be collimation screws but I haven't seen them.
Additionally, the Yukon 6x to 100×100 mm spotting scope that I have also gives very nice star images. I definitely would not want to drop this lightweight spotting scope. Also I don't think that I would like to drop the 30×50 binocular, although this seems to be more sturdy than the spotting scope.

The alignment problems, relate to Maksutov telescopes. The classic design has the secondary mirror as part of the correcter shell. So there is no adjustment needed for this, although the positioning is critical in these designs.
These are usually F/12.5 or slower.
I do have a 150 mm F/10 Maksutov, but this needs a separate secondary which has collimation screws. I used this for years without problems, without having to adjust it, but the initial alignment has to be very good.

Also Schmidt Cassegrains needs very careful alignment.

So having two of these instruments mounted as a high magnification binocular, using relay lenses would be extremely tricky, may be outside the capabilities of ordinary folk to align.

I have a 5.3 inch approximately, Maksutov that had a triplet relay lens made by the person who made all the fast compound instruments mentioned earlier. He was able to figure lenses to give good results. This triplet was broken and replaced by a doublet, and lesser folks simply have been unable to make this instrument work. So basically, for some of these instruments you do need a master optician.

Having said that, it is quite clear that large numbers of compound instruments with fast primaries, both telescopes, and mirror lenses for cameras, are being successfully made.

I would mention that I have a Samyang 800 mm mirror lenses and the one I have is awful. It is very soft, the contrast is low and the resolution is not very good and the image is mushy.
I've also had some of the older mirror lenses, which display bad astigmatism and generally poor images. So it is quite possible to make bad mirror lenses, both custom-made and factory made.

I'm not disputing that most people would have trouble making these fast systems. However, there are people who can make them repeatedly to high standards, both custom-made and factory made.

I have a 1000 mm F/10 very early Soviet MTO that is unbelievably good. The serial number is in low single digits.
Also I've seen and tested another unbelievably good Dutch military mirror lens about 5 1/2 inches aperture.
The Mirador 70 mm Maksutov spotting scope that I have has a standard zoom lens of 30 times to 120 times, plus an additional, I think 25 times eyepiece, and will take any Astro eyepiece. I think that this mirror spotting scope probably resolves as well or better at 120x than any 65 mm refractor spotting scope including fluorite models.
It is thought that a 70 mm mirror scope like this resolves as well as the best 53 mm refractor. This is because normally the resolution is thought to be equivalent to the full aperture minus the diameter of the obstructing secondary mirror. But spotting scopes use fast objectives and have prisms though, and even exotic ones are not as good as the best long focus refractors

Some people don't like mirror scopes, but others do. The fantastic planetary images taken by Astro imagers are often taken with Schmidt Cassegrains, which have very large secondary mirrors.

. The 30×50 Yukon spotting scope as detailed on the Amazon site is generally pretty poor quality, although they vary quite a bit. The price quoted is ridiculous, it should be about 1/10 of this.
The 30x50 Yukon binocular is not two of these side-by-side but a purpose made folded refractor design.
The 30x50 spotting scope is just a fairly cheaply made draw tube telescope.


The 6x to 100×100 mm spotting scope is quite different and is a folded refractor, however, originally with a 45° inclined eyepiece but I think later also available in a straight through design. It is quite novel and extremely lightweight. But the housing is some kind of plastic.

Binastro said:

. No,
. The Yukon 30×50 that I have is essentially perfectly collimated and gives very nice star images. So it is apparently fairly easy for the maker to achieve collimation that is fixed. I suppose there may be collimation screws but I haven't seen them.
Additionally, the Yukon 6x to 100×100 mm spotting scope that I have also gives very nice star images. I definitely would not want to drop this lightweight spotting scope. Also I don't think that I would like to drop the 30×50 binocular, although this seems to be more sturdy than the spotting scope.

The alignment problems, relate to Maksutov telescopes. The classic design has the secondary mirror as part of the correcter shell. So there is no adjustment needed for this, although the positioning is critical in these designs.
These are usually F/12.5 or slower.
I do have a 150 mm F/10 Maksutov, but this needs a separate secondary which has collimation screws. I used this for years without problems, without having to adjust it, but the initial alignment has to be very good.

Also Schmidt Cassegrains needs very careful alignment.

So having two of these instruments mounted as a high magnification binocular, using relay lenses would be extremely tricky, may be outside the capabilities of ordinary folk to align.

I have a 5.3 inch approximately, Maksutov that had a triplet relay lens made by the person who made all the fast compound instruments mentioned earlier. He was able to figure lenses to give good results. This triplet was broken and replaced by a doublet, and lesser folks simply have been unable to make this instrument work. So basically, for some of these instruments you do need a master optician.

Having said that, it is quite clear that large numbers of compound instruments with fast primaries, both telescopes, and mirror lenses for cameras, are being successfully made.

I would mention that I have a Samyang 800 mm mirror lenses and the one I have is awful. It is very soft, the contrast is low and the resolution is not very good and the image is mushy.
I've also had some of the older mirror lenses, which display bad astigmatism and generally poor images. So it is quite possible to make bad mirror lenses, both custom-made and factory made.

I'm not disputing that most people would have trouble making these fast systems. However, there are people who can make them repeatedly to high standards, both custom-made and factory made.

I have a 1000 mm F/10 very early Soviet MTO that is unbelievably good. The serial number is in low single digits.
Also I've seen and tested another unbelievably good Dutch military mirror lens about 5 1/2 inches aperture.
The Mirador 70 mm Maksutov spotting scope that I have has a standard zoom lens of 30 times to 120 times, plus an additional, I think 25 times eyepiece, and will take any Astro eyepiece. I think that this mirror spotting scope probably resolves as well or better at 120x than any 65 mm refractor spotting scope including fluorite models.
It is thought that a 70 mm mirror scope like this resolves as well as the best 53 mm refractor. This is because normally the resolution is thought to be equivalent to the full aperture minus the diameter of the obstructing secondary mirror. But spotting scopes use fast objectives and have prisms though, and even exotic ones are not as good as the best long focus refractors

Some people don't like mirror scopes, but others do. The fantastic planetary images taken by Astro imagers are often taken with Schmidt Cassegrains, which have very large secondary mirrors.

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A good quality apochromatic refractor can take good astro photo's to can't it?

. Yes.

[email protected] said:

A good quality apochromatic refractor can take good astro photo's to can't it?

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For me, that would be the primary use of an apochromatic refractor, especially one with a fast focal ratio.

HighNorth said:

For me, that would be the primary use of an apochromatic refractor, especially one with a fast focal ratio.

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Outside of just planetary observation. When I was into Astronomy I really preferred a nice refractor over a reflector for planets.

Binastro said:

. There are very large telescopes with very fast primary mirrors. Such as 8 m or 300 inch F/1. Others of F/1.25.
And designs for a 30 m telescope with an F/0.5 primary. Correctors are used.
The primaries are usually spherical.
The common low-priced Schmidt Cassegrains use F/2 mirrors.
there is nothing very difficult about making fast mirrors if the design requires it.

I also had a very strange Philips mirror system which seems to have perhaps an F/1 primary and you looked at it from the side. I never did find out what it was.

I have a Sigma 500 mm F/4 mirror lens, which is complex. It only works at one focusing distance. If you focus away from this point the image becomes progressively worse. I do not know how fast the primary mirror is on this.
There is also the Nikon 500 mm F/5 and I think the Zeiss 500 mm F/4.5. Again I don't know how fast the primaries are.
As has been said above the secondary obstructions are large and the contrast low.
The Minolta 250 mm F/5 .6 lens is very small and quite useful, but again the contrast is not very good.

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The Phillips mirror system is interesting. I have never heard of that.

Binastro said:

I have a 1000 mm F/10 very early Soviet MTO that is unbelievably good. The serial number is in low single digits.

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Is that the MTO 10/1000 telephoto lens? I've got one of those as well, with a later serial number (922xxx). I use it with an Intes prism diagonal and Zeiss Jena orthoscopics (26mm, 16mm and 10mm). At 100x the image is very good indeed. Used with a Leica zoom eyepiece (plus adapter) I get up to 140x, still at a very decent optical quality.

The MTOs are really nice and built to last. There were quite a lot on the market some 20 years or so ago, and many astronomers over here got them for use as a travel scope. They were lovingly called "Russentonne".

Hermann

Hermann, the one you have seems to be a late one made in 1992, may be post-Soviet, but it still may be good.
I've had about four of these over the years with varying manufacturing dates. They generally do perform well up to 100 times, although I found that they have temperature stabilisation problems if used in cold weather or through an open window. Part of this is atmospheric disturbance, but also due to the instrument itself.

The eyepieces that you have are probably very high quality.

There was I think a variation, possibly called a Russar, which had a doublet corrector in the front, rather than the normal single corrector. Whether this was better or not I don't know, it may be better corrected off axis.

Many mirror lenses have been made with doublet correctors and also complex relay lenses, and some use Mangin mirrors, where the mirror itself is used as a refractive element with the coating on the back rather than on the front.
The 1000/F10 MTO is a fairly simple version, but of high quality.
The filters supplied with it are usually of high quality and is the cheapest way of getting good quality filters 100 mm diameter.
Both the Russian and Soviet 500 mm F/8 and 1000 mm F/10 are geometrically correct F numbers.
However, the Japanese good quality mirror lenses such as Nikon, Minolta, Canon and the Optomax are 77 mm aperture instead of 62 mm or 63 mm for the Russian 500 mm F/8. The Japanese ones compensate for the central obstruction. However you cannot call them 500 mm T/8 as they are not further corrected for transmission losses. So there may be 500 mm T/9.5 unless they have enhanced coatings.
The Tamron I think uses enhanced coatings, possibly a doublet corrector and maybe a back silvered mirror?
This is usually very good and a bit better than the Sigma or Tokina versions.
One really needs to try these lenses at high magnification on stars to see how good they are.

The one that I have, mentioned above, is quite outstanding and was made about 1950, and has a special wooden box. It is about the best optical quality that can be made. It is made by a master craftsman and I've often wondered whether it was made by Maksutov himself, although I don't know offhand the year he was born. It is definitely better than two Questar telescopes that I have used. Bouwers in Holland independently invented the same thing, but during the war years they did not know about each other's work. But Den Oude Delft made fantastic quality optics, at least the ones I've seen.

The Mirador 70 mm spotting scope is also essentially perfect and can be used up to 200 times magnification.
I think it was a special manufacturers sample, as I have not seen another one.

Similarly, the Pentax 100 mm F/12 top quality refractor that I had also seems to have been a special manufacturers sample.
These are the optics to get, if you can get hold of them.

The Russian small spotting scope that I have is maybe 65 mm or 70 mm aperture, I think called Astele? It is also very good and can be used at high power.

Generally, Soviet and Russian mirror lenses and mirrors scopes are of high quality, although quite heavy.

These types of telescopes are optically good at high magnification, although because of their long focal length they are not suited to low magnification and they don't have wide fields. If buying a goto telescope I would definitely not advise going for one of these long focal length instruments, but rather go for a short focal ratio, because the goto is often not accurate enough to find anything. Beginners buy these telescopes, get completely frustrated. The telescopes end up in the attic and the owners lose interest.
Similarly, I would advise against any beginner buying a telescope with a flimsy Equatorial mounting and tripod. They are pretty useless. A simple sturdy altazimuth mount works and is a much better idea.
Unfortunately, people nowadays think that electronics and digital is a way is the way to go. It isn't.

. Regarding the last post, 59.

The 1000 mm F/10 Soviet mirror lens from about 1950 is of a different design than the later common MTO lens.
This earlier design had an integral lens hood with an internal lip, which is part of the optical construction. This lip was an aperture stop in front of the corrector. I suppose it would work without the special hood, but I've used it complete as it is meant to be. I don't think many of these were ever made.