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Author Topic: Maksutov Cassegrain 1000mm  (Read 2936 times)
whiteheat
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« on: November 15, 2012, 05:04:32 AM »
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Hi All

Some advice needed.  Does anyone know what filter size this lens uses? (Maksutov Cassegrain 1000mm)

Many thanks.
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ErikKaffehr
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« Reply #1 on: November 15, 2012, 05:34:52 AM »
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Hi,

That is a catadioptric lens. There are many makes. You need to be more specific.

Best regards
Erik

Hi All

Some advice needed.  Does anyone know what filter size this lens uses? (Maksutov Cassegrain 1000mm)

Many thanks.
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snoleoprd
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« Reply #2 on: November 15, 2012, 11:31:06 AM »
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Most telescopes and similar Maksutov type lenses are not threaded for filters generally. I have yet to see one threaded does not mean they do not exist. The front element is generally not flat as the secondary mirror is plated on to the concave glass that is on the front element. The are also fixed aperture as you probably already know. Focusing is quite slow generally. It will depend on the actual lens/scope.

Alan
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Alan Smallbone
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whiteheat
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« Reply #3 on: November 15, 2012, 11:02:57 PM »
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OK, I'd better get a more exact model info.  It is an MTO 11CA 100/1000mm Maksutov Cassegrain and looks like this........

http://www.telescope-service.com/maksutovs/MTO/MTO.html
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FranciscoDisilvestro
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« Reply #4 on: November 15, 2012, 11:47:28 PM »
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I belive it is M116x1
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whiteheat
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« Reply #5 on: November 16, 2012, 03:23:48 AM »
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I belive it is M116x1
OK great.  So it would now seem, although the information format of "M116x1" doesn't intuitively connote that the filter size is 116mm!

Well, thanks to all who have replied.
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snoleoprd
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« Reply #6 on: November 16, 2012, 09:14:06 AM »
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They don't seem to say anywhere on the web site, I would email and ask them, it may be that the sliding lens shade may interfere, it says it screws on.
http://www.teleskop-express.de/shop/product_info.php/info/p2411_Maksutov-Tele-Objective---1000mm-focal-length---f-10-Flat-Field.html

sounds like an interesting lens but the bokeh will be typical of catadioptics. I would be interested in seeing some images from it if you get it. The 500mm they sell uses 72mm filters but you cannot really extrapolate.

Alan
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Alan Smallbone
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nemophoto
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« Reply #7 on: November 16, 2012, 12:23:31 PM »
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Most cat lenses rely upon a drop-in or rear filter, rather than a front filter.
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snoleoprd
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« Reply #8 on: November 16, 2012, 02:48:20 PM »
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The one he is looking at has front filters, it is not your usual cat type lens. Even the focuser is different than a normal one.

Alan
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Alan Smallbone
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FranciscoDisilvestro
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« Reply #9 on: November 16, 2012, 04:35:56 PM »
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Quote
it may be that the sliding lens shade may interfere, it says it screws on.

I had one of those lenses a few years ago (MTO-1000). The filters screw in, the lens shade does not interfere, the filters have the same outer diameter as the lens.

Here a couple of pictures with that lens on film

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whiteheat
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« Reply #10 on: November 17, 2012, 03:29:00 AM »
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Hi All

I emailed the seller and he replied saying that the manufacturer originally produced front mounted filters for this lens, however, due to lack of demand, they stopped manufacturing them!  Anyway, there is also another solution.  He said that he supplies an adapter that can be screwed in to back of the lens and then a 2" filter, which he also supplies, can be fitted (note the imperial measurement - not metric).  Well, so far so good.  However, this little solution is going to cost over 100 euros and it will only partially meet my requirement, which as well as filtering light, the filter was to act as front element protection.  Obviously, if rear mounted this won't do.  I have searched for 116mm filters but with no luck so far.

Many thanks to every one all the same.
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stevesanacore
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« Reply #11 on: November 18, 2012, 07:22:05 AM »
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2" filters that screw on behind the lens on the focus tube are standard issue for astronomical telescopes. The only issue I see here is that the focuser is built into the lens body which means if you screw a filter on behind the lens it will change the distance of the lens to the film plane.
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whiteheat
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« Reply #12 on: November 25, 2012, 04:05:09 PM »
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Disappointed with this lens.

The problem though is not an optical one as the lens produces fine images for a reflex lens.  The problem is with the design and build.  Actually, there are 2 problems.

The first is that the rear mount is of the free rotating kind.  To explain.  The rear mount requires a T-mount adapter, which allows connection to whatever camera you have (you just specify your required T-mount type at time of purchase).  The rear mount rotates so that when the lens is fixed on a tripod, it is easy to align the camera to the vertical or horizontal positions as required, which is very useful.  However, what is missing is a locking mechanism to prevent further rotation when the camera is attached and aligned as required.  The result is that the camera then immediately slews to one side or other because the rear mount continues to rotate as there is nothing to prevent it from doing so.  The only improvisation at the time was to hold the camera to stop it rotating!!!  On reflection, I think a long slider plate and some wedging material would do the job.

The second problem and much greater problem, was the focusing ring.  This being a manual lens, focusing is quite a critical aspect.  The focusing ring on this lens is so stiff and heavy that it required 2 hands to move it with any degree of accuracy.  The problem with that is that the lens then moves around like crazy and makes focusing on a specific target extremely difficult even with focus peaking, which doesn't work that well because of potential lack of light and that the target subject is difficult to maintain within the frame whilst trying to focus on it because of the amount of force being exerted on the lens just to move the focus ring.

The result is that from a useability perspective, I much prefer the lighter and cheaper Vivitar 800mm Series 1, which is much easier to work with even though it has 200mm less reach than the Maksutov.  Unless there is a way to greatly loosen the focusing ring, this lens will probably never see the light of day again.
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BrianVS
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« Reply #13 on: November 26, 2012, 04:11:02 PM »
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Can you use a different T-Mount adapter, one with set screws to lock into position?

I've not taken a large Russian lens apart- but the Jupiter lenses use a grease that is almost like candle wax. Cleaning the old grease out and replacing with one not as heavy makes those lenses much easier to turn. Is it worth dropping the lens off to a reapir shop for a relube?

I have used a Meade 1000/10 and 1000/11 before- did not have these problems, but not the sharpest optics on a camera. I still have the 1000/11.
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whiteheat
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« Reply #14 on: November 26, 2012, 07:26:42 PM »
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Hi Brian

Thanks for that.  Unfortunately, there is nothing at the back of the lens behind the mounting ring that any locking mechanism could lock in to!  Never mind, I can get around that problem without to much hassle.  As for your other suggestion, it's worth a try but I wonder about the cost of doing so as it is likely to be at least $100 and then if it fails to produce any significant difference, it would have been a complete waste of money.
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Kevin B
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« Reply #15 on: November 29, 2012, 08:42:20 AM »
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Check out the True-2 prime focus adapter and the Baader Clicklock.  The adapter mounts on the camera just like any lens, and any filter you want threads onto the end of it.  I have a polarizer on mine.  A short twist of the Baader Clicklock and it clamps down on the barrel of the adapter and the camera is locked in place.  I don't know enough about your lens to know if this will work, but if you can mount the Clicklock on the back of the lens you are good to go.   This combination is way better than any T-mount adapter that I have seen.     
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