M42 lenses + ASI2600MC Pro - Forums

Topic starter

Jun 13, 2024

Dear AstroBinners,

I have a question regarding the compatibility of vintage M42 camera lenses with the ZWO ASI2600MC Pro camera.

According to sources, the so-called "flange distance" of M42 lenses is 45.46mm

The 2600 camera has 17.5mm between its sensor and the M42 thread

My question is simple - will the M42 lens work with it?

Would I simply attach the lens to the camera directly? Would I need to use spacers? Would the distance between the lens and camera have to be exactly 55mm?

Here is the image of the M42 lens;

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Christian Großmann

Jun 13, 2024

Hi,

the answer is, that the distance from the sensor to the back of the lens (not to the thread) must be 45.56mm. So you need an adapter to get this value. I never saw such an adapter, but they might be available somewhere.

In my experience, M42 lenses may not be the best option for your camera. I tried them with my DSLRs several times and they are usually quite soft and have other issues that even cheaper modern lenses do not have. I don't know which lens you plan to use, but they might be at least three decades old. I assume, they are even older. During this period of time, photography changed significantly and digital sensors need other optical designs. So unless you are doing it just for fun, it may be worth thinking about another way of getting the images you want. But I totally understand if you will give it a try

CS
Christian

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Jan Erik Vallestad

Jun 13, 2024

Christian already gave the only right answer here, the flange focal distance on the different lenses are absolute. The idea of 55mm doesn't apply to lenses in general. Wikipedia has a good general description as well as a list of all common mounts: https://en.wikipedia.org/wiki/Flange_focal_distance

As long as the flange focal distance of the lens is more than the 17,5mm on your camera you can adapt it. Just subtract the 17,5mm and then you have the right amount of space you need to fill in, remember to factor in 1/3 of the filter thickness as well if you use any.

There are several good vintage lenses out there. Some of the small Takumar tele-lenses have been known to be quite good. I used an 80s Nikkor 135mm lens that also weren't bad. I know I had some other suggestions here on Astrobin a while back as well, but sadly I couldn't find it atm.

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Christian Andres

Jun 13, 2024

There is also the issue with different thread pitch between the two standards. The vintage M42-mount comes with M42x1 whereas the "T-mount" (T2) is M42x0.75. Keep that in mind while looking for an adapter.

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