Depends on how long is, well, long. There are a couple of fairly common and rather lovely Pentax zooms (SMC Pentax-A 70-210mm f4 and SMC Pentax-M 80-200mm f4.5) to keep an eye out for, the latter was also sold in the K series (marked SMC Pentax without the -M). Both will give a prime serious competition.

Any of the original K series Pentax lenses are worth having in good condition - they're marked "SMC Pentax" without any suffixes like "-M". These are seriously well-made, sharp lenses which can embarrass brand new glass in the right hands.

Don't just chase something like a generic 500mm prime or mirror lens, generally they're not up to much and you'll get more use from something around the 200mm mark.

Take an LED torch to check inside lenses, it should show up any dust or fungus. Check the focus is smooth and the aperture ring works properly - if you set it to the smallest aperture and move the lever with a finger the aperture should open and close snappily.

Good luck - I wish we had photo fairs near here!

I would think that the images would survive the trip, otherwise there wouldn't be a lot of point!

On the other hand it could be interesting working out what gear to take. I think for pre-SLR era I would want an MX, 40mm f2.8 and a pocket full of film as it'd be easy to tuck away and avoid drawing attention. Plus you'd probably get away with it even if spotted - the 35mm rangefinders were not that much bigger and of similar shades.

I should perhaps have specified that as you have a controllable time machine you can come back to 2010 when you run out of batteries/memory cards/film...

It definitely should work - anything from the F series onwards will work on a Pentax DSLR just as a new DA series lens does.

It does sound as though the lens isn't going into "A" mode properly as that's exactly what happens if you put a lens on with the aperture set to something other than A. Have you tried wiggling the aperture ring or repeatedly moving it to and from the A position?

Already have done - there's a Metz 45 CL-1 in the post. The first one I spotted had sold but I noticed an identical one for £36, which isn't bad even if I need to replace the nicads. They appear to be standard AAs so I just need to match the amp/hour rating.

A thought I had recently and felt might provoke an interesting thread:

You bang your head and invent the flux capacitor. After building a time machine you realise that you'll need photos to prove it worked, so grabbing your camera you climb aboard and push the button...

When do you go and what do you shoot?

I think I'd probably want to go back to the 1920s and get involved with the Bentley Boys Le Mans entries. By most accounts it would seem that it was more of a party than a motor race!

I'm now in a bit of a quandary:

I could buy a used Metz 45 CL-1 hammerhead flashgun, the trigger voltage is safe according to various sources and it comes with all the bits for £40

Alternatively I can get a bracket to mount my AF240Z in a similar position for £10

I don't use flash a huge amount, I already have the AF240Z and the cable to trigger it off-camera is in the post. However, I'm thinking that the bracket is £10 I could be putting towards the Metz unit. Thoughts?

Just wondering whether anyone has one of these and can comment on how it works with a Pentax DSLR? Would there be any automation beyond the old "set aperture and shutter speed, then let the flash vary its output"?

I found some stuff about the later CL-3 and CL-4 which suggested that they will track your shutter speed, ISO and aperture settings but I don't know whether the CL-1 can do this?

What about the Metz 45 CL-1? I see those going for £50 or less fairly often and I suspect there may be a module to support program flash, like my AF240Z does. I've just seen one for about £40 with flash, bracket, mains adapter, battery pack and sync cord which looked in good condition.

I just don't see much point in buying something like an AF400T when I can't use anything other than the manual mode. The Metz unit presumably has a similar power output, is a hammerhead gun, and would only need a simple module to connect to the K-m. The sync cord I've already ordered will still come in handy as it provides a PC socket.

That may well be due to the old thing of people not wanting to leave negative feedback because they'll get tit-for-tat responses. I know there are still a few sellers around who won't leave feedback until the buyer does.

Goats cheese and caravan fridges do not mix (from the list of things I learned from family holidays to France). It has a habit of attacking anything within a half mile radius unless sealed in a container. The ones used for transporting used nuclear fuel rods are just about effective for this.