[ggb]

I am interested in Astrophotography.

I know the 67 lenses are well regarded for that as they are sharp and also have a lot of backfocus making it easier to set them up with a separate
digital focuser unit.

What other lenses are good for this use?

Greg.

[wildman]

Maybe I misunderstand but shouldn't you be thinking in terms of a scope rather than conventional short FL photography lens'?

[rhodopsin]

If your information about 67 lenses is correct, I think the same could be said of the longer 645 lenses.

In either case, I agree with wildman, for the cost of the 400mm - 1000mm lenses you could buy a REALLY nice telescope with a faster longer lens, complete with tracking mount. Take a look at opticsplanet.com (I have no affiliation, I'm only a satisfied customer).

[ggb]

Thanks for the replies.

I already have several nice telescopes. Lens astrophotography is more about imaging widefield Milky Way or other larger objects.

Thanks for the info about the 645 lens.

Do you know how much backfocus they have?

Greg.

[rhodopsin]

"back focus" or camera register for 645 is 70.87mm, 6x7/67 is 84.95, reference mounts.htm

On that document you'll find there are lenses from other camera systems with "back focus" that meet your requirements.

[smigol]

I assume that you're not using a camera body for the imaging setup but are mating the lens to a CCD/CMOS camera. Richard Crisp (at narrowbandimaging.com) has been using some old Pentax 6x7 lenses for this purpose and goes into detail about the mounting and techniques he's used.

[ggb]

Thanks for that. Yes I know Richard and the lenses are intended to be mounted to my FLI Proline 16803 CCD camera with a special adapter which I have had made.

I have used other lenses in the past with other cameras but the 16803 chip is 44mm square so it requires a large corrected circle and also for ease of focusing it needs a longish backfocus of 84mm.

Greg.