MTO-11CA 1000mm f/10 M42 mount options

**nater** · 08-30-2014, 07:39 PM

So I have a version of this lens with the M42 mount on it's way. My research indicates it might take other mounts. It isn't a T-mount, by any chance, is it? Did MTO or a third party make a K-mount for it? If not, what would be the best way to adapt the M42? I'm aware of the official Pentax M42 adapter, but that's best when you can dedicate a Pentax body to it, and I have no other M42 lenses. Third-party M42 adapters can be more convenient but can mean a lens looses infinity focus because they are typically thicker.

**boriscleto** · 08-30-2014, 08:32 PM

There are 2 types of third-party M42 adapter. One that has a thick flange and one that sits inside the mount like the Pentax adapter. The adapter with a flange is only useful for macro photography as it affects infinity focus.

For a specialized lens like this, which will only be used with a heavy tripod anyways, get the Genuine Pentax Adapter K. It's not like you are going to be swapping lenses when using it, and even if you were it takes like 2 seconds to remove the adapter. Third party adapters are less convenient because they need a special tool to remove, unless you take the spring clip out.

The flanged adapter might even be useful if you want to focus closer than 24 feet...some extension tubes too.

**jatrax** · 08-30-2014, 09:12 PM

Get the genuine Pentax adapter. Don't even think about it. And no you do not need a dedicated camera, it comes off in like 3 seconds. Just press the release tab and turn, nothing to it.

**nater** · 08-30-2014, 10:42 PM

Thanks for the suggestions, if I go the M42 route I'll use the official Pentax adapter.

I had remembered reading about using a T-mount to K mount adapter on this lens a few years back, and some googling turned up the post I remembered from another forum:

Russian 3M/6A 500mm f6.3 mirror

"If you buy an eos t mount you should be able to seperate the outer ring with the 3 little screws and then screw it onto the spigot. It's like a t mount but with one half of the mount always attached to the lens instead of unscrewing, I think the register distance is slightly different but you should still be able to get infinity focus. My mto-11ca had the same thing, it seems any t mount can be disassembled and screwed into the spigot."

I'll try this T-mount method first since if it works will effectively make the lens into a K-mount.

vonBaloney · 08-31-2014, 06:23 AM

Most mirror lenses will focus past infinity quite a bit -- you might get away with a flanged adapter (which will also be most secure) if the flange is very thin (some are). (And infinity is probably REALLY far out on that thing, so even if you lose the moon, you might still be able focus on anything on earth you can actually see.)

If you use a regular m42 adapter, I'd definitely use the genuine one though -- the others you pretty much have to remove to spring to keep from losing your mind, and then you have only a friction fit which would be dangerous with that lens.

**jatrax** · 08-31-2014, 09:38 AM

Originally posted by nater

I'll try this T-mount method first since if it works will effectively make the lens into a K-mount.

Do make sure the lens is t-mount and not m42. From what I read it is an m42 lens not t-mount.

T-mount was designed to be a generic mount with m42 x .75 threads on one side and an adapter on the other side that took a mount for different brands, including Canon, Nikon, Pentax k-mount and Pentax M42. Pentax M42 mount has M42 x 1.0 threads and looks very close to t-mount but if you force one on the other you will ruin the threads.

If the lens is t-mount then unscrewing the whole adapter will leave you with a lens that has m42 x .75 threads that the t-mount->k-mount adapter will thread onto.

If it is M42 all you need is the m42->K-mount adapter.

**nater** · 09-07-2014, 08:37 PM

Originally posted by jatrax

Do make sure the lens is t-mount and not m42. From what I read it is an m42 lens not t-mount.

Now that I have all the bits (lens and T2 adapter) I can speak in more detail.

If you read the post from mflenses.com, this is the most relevant bit: "It's like a t mount but with one half of the mount always attached to the lens".

There are T-mount adapters that go to K-mount and are made up of two parts, an inner part that has the T-mount threads and an outer part that has the K-mount (not unlike C-mount adapters for the Q). There are three little screws that you tighten to lock the two pieces together, and you loosen them in order to align the lens rotation so the focus indicator points up in the normal way. So the neat thing about the MTO-11CA is that it is exactly as they described on the mflenses.com forum - the base of the lens is one half of one of those adapters. To convert it from M42 to K-mount, you loosen three little screws around the M42 part of the lens, and then that comes off, leaving an unthreaded ring. You then take apart a T-mount to K-mount adapter (I used a Qualide brand I bought from ebay for $7) the same way, removing the three little screws and separating the two parts. Then you take the K-mount part and fit it over the unthreaded ring on the MTO-11CA, and tighten the three little screws down with the lens aligned so the focus indicator is at the 12 o'clock position when the lens is mounted to the camera and voila, you now have an MTO-11CA with a native K-mount! No adapter other adapter needed, and very easy to reverse.

I just did some test shots of the full moon, quick and dirty, and I'm very happy with the results. This may be the mirror lens I have been searching for my whole life!

08-30-2014, 07:39 PM	#1
nater Loyal Site Supporter Join Date: Aug 2009 Location: New England Photos: Albums Posts: 706	MTO-11CA 1000mm f/10 M42 mount options So I have a version of this lens with the M42 mount on it's way. My research indicates it might take other mounts. It isn't a T-mount, by any chance, is it? Did MTO or a third party make a K-mount for it? If not, what would be the best way to adapt the M42? I'm aware of the official Pentax M42 adapter, but that's best when you can dedicate a Pentax body to it, and I have no other M42 lenses. Third-party M42 adapters can be more convenient but can mean a lens looses infinity focus because they are typically thicker.

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08-30-2014, 08:32 PM	#2
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	There are 2 types of third-party M42 adapter. One that has a thick flange and one that sits inside the mount like the Pentax adapter. The adapter with a flange is only useful for macro photography as it affects infinity focus. For a specialized lens like this, which will only be used with a heavy tripod anyways, get the Genuine Pentax Adapter K. It's not like you are going to be swapping lenses when using it, and even if you were it takes like 2 seconds to remove the adapter. Third party adapters are less convenient because they need a special tool to remove, unless you take the spring clip out. The flanged adapter might even be useful if you want to focus closer than 24 feet...some extension tubes too.

08-30-2014, 09:12 PM	#3
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Get the genuine Pentax adapter. Don't even think about it. And no you do not need a dedicated camera, it comes off in like 3 seconds. Just press the release tab and turn, nothing to it.

08-30-2014, 10:42 PM	#4
nater Loyal Site Supporter Join Date: Aug 2009 Location: New England Photos: Albums Posts: 706 Original Poster	Thanks for the suggestions, if I go the M42 route I'll use the official Pentax adapter. I had remembered reading about using a T-mount to K mount adapter on this lens a few years back, and some googling turned up the post I remembered from another forum: Russian 3M/6A 500mm f6.3 mirror "If you buy an eos t mount you should be able to seperate the outer ring with the 3 little screws and then screw it onto the spigot. It's like a t mount but with one half of the mount always attached to the lens instead of unscrewing, I think the register distance is slightly different but you should still be able to get infinity focus. My mto-11ca had the same thing, it seems any t mount can be disassembled and screwed into the spigot." I'll try this T-mount method first since if it works will effectively make the lens into a K-mount.

08-31-2014, 06:23 AM	#5
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Most mirror lenses will focus past infinity quite a bit -- you might get away with a flanged adapter (which will also be most secure) if the flange is very thin (some are). (And infinity is probably REALLY far out on that thing, so even if you lose the moon, you might still be able focus on anything on earth you can actually see.) If you use a regular m42 adapter, I'd definitely use the genuine one though -- the others you pretty much have to remove to spring to keep from losing your mind, and then you have only a friction fit which would be dangerous with that lens.

08-31-2014, 09:38 AM	#6
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by nater I'll try this T-mount method first since if it works will effectively make the lens into a K-mount. Do make sure the lens is t-mount and not m42. From what I read it is an m42 lens not t-mount. T-mount was designed to be a generic mount with m42 x .75 threads on one side and an adapter on the other side that took a mount for different brands, including Canon, Nikon, Pentax k-mount and Pentax M42. Pentax M42 mount has M42 x 1.0 threads and looks very close to t-mount but if you force one on the other you will ruin the threads. If the lens is t-mount then unscrewing the whole adapter will leave you with a lens that has m42 x .75 threads that the t-mount->k-mount adapter will thread onto. If it is M42 all you need is the m42->K-mount adapter.

09-07-2014, 08:37 PM	#7
nater Loyal Site Supporter Join Date: Aug 2009 Location: New England Photos: Albums Posts: 706 Original Poster	Originally posted by jatrax Do make sure the lens is t-mount and not m42. From what I read it is an m42 lens not t-mount. Now that I have all the bits (lens and T2 adapter) I can speak in more detail. If you read the post from mflenses.com, this is the most relevant bit: "It's like a t mount but with one half of the mount always attached to the lens". There are T-mount adapters that go to K-mount and are made up of two parts, an inner part that has the T-mount threads and an outer part that has the K-mount (not unlike C-mount adapters for the Q). There are three little screws that you tighten to lock the two pieces together, and you loosen them in order to align the lens rotation so the focus indicator points up in the normal way. So the neat thing about the MTO-11CA is that it is exactly as they described on the mflenses.com forum - the base of the lens is one half of one of those adapters. To convert it from M42 to K-mount, you loosen three little screws around the M42 part of the lens, and then that comes off, leaving an unthreaded ring. You then take apart a T-mount to K-mount adapter (I used a Qualide brand I bought from ebay for $7) the same way, removing the three little screws and separating the two parts. Then you take the K-mount part and fit it over the unthreaded ring on the MTO-11CA, and tighten the three little screws down with the lens aligned so the focus indicator is at the 12 o'clock position when the lens is mounted to the camera and voila, you now have an MTO-11CA with a native K-mount! No adapter other adapter needed, and very easy to reverse. I just did some test shots of the full moon, quick and dirty, and I'm very happy with the results. This may be the mirror lens I have been searching for my whole life!