The Moon.

I couldn't sleep last night and saw the moon out of my window. Figured it'd be nice to try and take a picture of it. I have a 400mm Optomax lens which I received as a hand-me-down from my mum, however it's an M42 mount and my only digital at the moment is my K7. I decided that if I put the lens on my tripod and rested the camera gently behind the mount I could perhaps get a shot. So I took about 25 high speed shots in the hope at least some may come out fairly sharp and to my surprise it worked rather well.

I'll put it on here if that's ok I've made sure it's not full size. Out of interest, I was considering getting a Pentax adapter for the lens because it's really rather nice, I saw a genuine Pentax model on the SRC Microsystems website. Good spend?

I know it's a bit corny but here it is: [cropped obviously]

[IMG]http://img195.imageshack.us/img195/8796/lunaup3.jpg[/IMG]

Alex; I have to say I love the way this is composed (or should I say how you've cropped it). It's that letter box aspect ratio combined with the colour of the moon itself reminds me of Tatooine from Starwars.

Very cinematic. I like it.

Thanks Bob, I find it more interesting to crop isolated objects that way.

You can pick up an adaptor on eBay for £3-4 so it's certainly worth doing that.

I heard that people are inclined to stay away from the cheap ones on eBay?

I've never been bitten by one. Try and find a low profile one (~£5+) to ensure infinity focus.

Have a look at the mount on your lens before you buy anything else

Many 3rd party older lenses use a T2 mount which can be swapped, so you can replace the M42 with a K mount rather than adding an adapter. A new T2 mount isn't expensive and it'll be much easier to use. Judging by photos I've found of the Optomax 400mm f6.3 I suspect that it is a T2 mount. Just loosen the three screws in the knurled bit next to the mounting thread and unscrew the mount from the lens, the K mount fits on in the same way (but can be rotated to put infinity focus on top).

@Steep could you possibly link me to one?

@Dangermouse I'm not sure I follow, although I do have a spare K mount on a broken lens?

This is the mounting on the Optomax I have:

[IMG]http://img849.imageshack.us/img849/9562/imgp8846.jpg[/IMG]

Cheapest I've seen so far...

http://www.ebay.co.uk/itm/Macro-M42-Lens-Pentax-PK-camera-adapter-K-7-K-M-KX-/29...

Thanks Steep, although it says at the bottom that it isn't capable of infinity focus. I will definitely shop around.

Just buy a SH Pentax original for under £30. You will always
sell it again for more than it cost.

Is this a preset lens or does it have an auto/manual switch (with the little silver pin visible on the bottom rim of the lens mount closing the aperture down when pressed)?

T2 mounts are an interchangeable lens mount. The lens is standard but the shop will bundle a different mount according to what camera you buy it for, said mount simply screws onto the back of the lens. I have a 500mm mirror lens with this fitting which came with a K mount, but I could easily swap that to an M42 mount or another brand entirely.

The presence of the silver pin suggests to me that this is a fixed M42 mount, as in my limited experience T2 mounts are only found on mirror lenses (with a fixed aperture) or preset lenses (where you close the aperture manually with a second control ring after preselecting an aperture with the normal click-stop ring).

If you can't swap the mount then you need an adapter like this one:

http://www.ebay.co.uk/itm/Pentax-M42-42mm-PK-K-Mount-K-Bayonet-Adapter-Ring-/110...

Note that it doesn't have the flange present in the other link, and will therefore allow infinity focus. I would still advise hunting for a genuine Pentax one though as they are far better made than the copies.

It does indeed have the auto/manual switch. I think you're on the money completely.

SRC have a genuine Pentax adapter. The lens is pretty sharp and on my oldest film camera it's taken some fairly nice pictures so I think getting the adapter is worthwhile.

Thanks for your help Matt and everybody else.