Thin electric focuser/helicoid?

[dickb]

The total distance between mft mount and dovetail is only 1 or 2 mm? The mft mount will be thicker than that by itself so that won't work.

[Lou Jost]

No, it could work. The distance I mentioned is the distance from the end of the MFT lens mount (the inner flanges) to the flat camera front, not the distance from the flange.

[dickb]

I am not familiar with the MFT mount in detail, but it still seems like a nigh impossible challenge to get a selfcontained electronic helicoid of under about 5 or 7mm of height. Or perhaps you can use a wide helicoid into which you can recess the entire MFT mount. The camera should be able to take such a helicoid, as it has a flat surface. The inner diameter of the helicoid should be wide enough to accomodate the rear of your MFT lenses, ideally in a way that allows you to reach the lens release button.. Alternatively if the camera is narrow enough you might be able to recess it into large helicoid or some kind of bellows instead.

Or perhaps fix the MFT lens and move the camera on a focus block with a MicroMate type of focusser. You'd need some non-load bearing bellows or shroud between the lens and the camera in that case. This would likely limit its use to indoors only.

[Lou Jost]

Or perhaps you can use a wide helicoid into which you can recess the entire MFT mount.

This is the approach I have been taking so far.

The inner diameter of the helicoid should be wide enough to accomodate the rear of your MFT lenses

I have not found a suitable helicoid yet.

"ideally in a way that allows you to reach the lens release button."

Luckily these astro cameras have no shutter button...

Or perhaps fix the MFT lens and move the camera on a focus block with a MicroMate type of focusser.

I've been working on that approach too, but consistent alignment in the field with micron precision is very difficult.

[dickb]

Or perhaps you can use a wide helicoid into which you can recess the entire MFT mount.

This is the approach I have been taking so far.

The inner diameter of the helicoid should be wide enough to accomodate the rear of your MFT lenses

I have not found a suitable helicoid yet.

How about something like this? 76.3mm free aperture should be wide enough to recess most MFT lenses into I guess.
https://eu.primalucelab.com/esatto-3/es ... cuser.html
This might actually be wide enough to recess the camera into, I read it has a diameter of 76mm..

"ideally in a way that allows you to reach the lens release button."

Luckily these astro cameras have no shutter button...

You misread what I wrote: lens release button, not shutter release.

Or perhaps fix the MFT lens and move the camera on a focus block with a MicroMate type of focusser.

I've been working on that approach too, but consistent alignment in the field with micron precision is very difficult.

That sounds like a serious challenge indeed.

[Lou Jost]

You misread what I wrote: lens release button, not shutter release.

Yup, sorry. I am half blind....I need surgery to get the lens of one of my eyes replaced.

Thanks, that Prima Luce thing might actually work, if my astro camera can fit inside it. It measures approx 75mm in diameter, slightly less than 76.3mm of the focuser. I better check the measurement carefully. Costly though...Adapters will also be tricky...but very interesting solution.

[Chris S.]

Lou,

You've no doubt considered this, but is there any reason that the linear actuator needs to be between camera and lens, rather than, say, under the lens? I'm thinking your could mount the lens on a microscope focus block, mount the camera just behind it, and make a small bag bellows to block light and dust between the two. It would be cumbersome, but easy to make.

--Chris S.

[Lou Jost]

Yes, I have thought of that, and considered a microscope focusing block. But they are heavy and for my astrophotography application I only have a very lightweight star tracker with low load capacity. They would also be very hard to collimate in the field with each change of lens.