Lens suggestions (for astro use).

[iancandler]

I have been looking at getting some more lenses for my DSLR mainly for widefield astro use.

Currently I have:

Samsung/pentax 18-55mm AF

sigma 70-300mm AF

sigma 400mm f5.6 MF

I had been thinking of a 28mm f1.8 or 2.8 and a small f2.8 zoom (24-135mm) as it would double for macro, portrait and other uses.

*update* I finally decided to go for a sigma F2.8 28mm lens for wide shots as it was around £100 cheaper than a secondhand F1.8

The bonus is that apparently you can pick up a fish eye attachment on ebay that works really well with it.

For the rest I think I've settled on either a 24-135 or 28-105 sigma F2.8 lens and a cosina 100mm macro .

The 100mm though not that fast at F3.5 can be put to good use for astro work as well as wildlife macro shots.

Now all I need to do is get an idea about what sort of exposures to do.. so its websearch time.

[cygnusx1]

Ian hi

I am assuming your Sigma lenses are the newer ones, i have read that the old ones won't fit dslr's.

Is this correct, I am looking on Ebay for a 70-300mm but most seem to be old version?

Also, i've heard a prime fixed focal lens is a better option, any ones you can recommend?

[Naz]

The fixed focus lens is a good choice at any focal length, usually about five or six elements, remember that zooms contain a lot of extra glass, up to about thirteen, or more, and each element introduces light loss and the risk of reflections. Also check that the older lenses will fit your camera and allow it to function.

naz

[Stardust]

Fixed focal length lenses are better, faster and usually sharper than zooms. I don't know the mounting of your camera but I've bought a few of the old manual M42 fitting lenses. Adaptors are available for different camers but they work very well with Canon camers. Just need some clear skies to try them out.

DAve

[themos]

Surfing the net I found out that the prime, manual, Zeiss Jena Multi-Coated 135mm@f3.5 was a classic. It has the M42 thread mount. I got one on ebay for thirty-odd pounds. I will mate it to the ToUcam for M45-like fovs (around 2° ).

[themos]

Manual focus lenses: http://www.mflenses.com/best-manual-focus-lenses-4.html

M42 mount lenses: http://m42.artlimited.net/site_lenses.php

[barkis]

I bought a Olympus DSLR to M42 Adaptor on Ebay, It allows me to use all my old M42 lenses on the DSLR, but only in MF mode.

Ron.

[cygnusx1]

Manual focus lenses: http://www.mflenses.com/best-manual-focus-lenses-4.html

M42 mount lenses: http://m42.artlimited.net/site_lenses.php

Thanks themos, bookmarked for reference!

[cygnusx1]

I bought a Olympus DSLR to M42 Adaptor on Ebay, It allows me to use all my old M42 lenses on the DSLR, but only in MF mode.

Ron.

Are all m42 adapters MF restricted? Do any allow AF?

Also i read one must check if M42 adapter one purchases will allow focus to infinity of a particular lens.

A bit confusing if ya tell me

[Stardust]

you can get an adaptor that bleeps when focus is achieved, don't know how well they work and if they'd work for astro use.

You're right about infinity focus being a problem with some cameras, Pentax wont work but check yours.

I too went for some Carl Zeiess lenses the 135mm is very nice another very well regarded one is a 35mm Flektogon, very sharp and will focus as close as 4cm giving 1:2 macro.

If you're on a budget the Pentagons ain't bad for the money but Carl Ziess and Pentax will be better.

ALL M42 lenses will be manual focus and you'll be using the camera in manual anyway.

Just need some decent weather to get the kit out there.

DAve

[barkis]

Only lenses designed for the DSLR will respond to AF. It's not possible to achieve Auto Focus with a non digital lens. This is a personal view, and there may well be someone with a different one.

Ron.