Frustration at 50mm...

[Knight of Clear Skies]

...which is preferable to terror at 30,000 feet, but still...

Haven't got the tracking mount going yet, so I had a quick play with the 1100D and 50mm f1.8 lens from a fixed tripod on Friday. My target was comet C/2012 K1 - more as a test of how the camera/lens combo can cope with local light pollution than in expectation of producing much of an image. I'd have been happy with the merest smudge.

Unfortunately I hit problems, the big one being the focus ring doesn't stay put. I've had trouble with this before, but it seems the closer I point it to the zenith the more quickly it slips. It's not stiff enough and the action of the shutters rocks it out of position. Out of 50 5-second subs I only got about 8 usable ones. Frustrating, but all part of the learning process so a useful exercise.

Looks like I'm going to have to either tape up the focus ring each time I use it for widefields, unless anyone has a better suggestion? Olly did post an image of a lens clamp in a previous thread about this, but I haven't been able to find one for sale anywhere. Is there anything else I could adapt maybe? Another option I have is to borrow an old M42 50mm lens, which has a much stiffer focus ring. Does anyone know if this would be worth trying please?

The other problem I'm having is aiming. The 50mm produces a busy starfield so I'm having trouble matching up my asterisms. Thinking about it perhaps I can try shooting at a lower ISO when taking framing shots, so that only the brightest stars stand out. Does anyone else have any other tips please?

As for C/2012 K1, I do have a smudge in the about the right place at edge of frame, but I'm sure if it's the comet or a couple of faint stars close together.

[JamesF]

Astro Tortilla may a the solution as far as aiming goes?

As regards the focus ring, if the camera is in full manual mode and you put the lens in autofocus mode, will the motors just act as a lock?

James

[Knight of Clear Skies]

Astro Tortilla may a the solution as far as aiming goes?

As regards the focus ring, if the camera is in full manual mode and you put the lens in autofocus mode, will the motors just act as a lock?

James

Astro Tortilla could be handy thanks. Trouble is, as a flat dweller it's often impractical to take my laptop and chair out to dark site as I have to walk some distance, so I'm hoping to get up and running with just the camera and mount. (This is also the biggest reason why I haven't yet bought my own telescope.)

Autofocus on the lens is independent of the camera mode, so unfortunately can't be used to stop it from slipping. Searching around a bit, I see that APT supports auto focussing, so I guess it must drive the focus motor in autofocus mode, which would also prevent slippage. That would be great if it works with my camera, but again I'd need the laptop. Has anyone tried this please?

[DaveS]

Get yourself a cheapo manual focus lens from almost anywhere and an adapter.

One of the joys of Canon EF is that most other lenses can be adapted to fit, the main exception being Canon's older FD and FL  lenses.

[Leveye]

DaveS is right on the money. Look a a Nikkor 50mm or any nikkor lens from the 70's really. That and an adaptor. I prefer Fotodiox myself. Oh and the great thing about an old Nikkor lenses is the Infinity setting is right on. Just set it and forget it.

[Photosbykev]

a wide rubber band that will cover some of the focussing ring and the adjacent static metalwork so it acts like a clutch

[Adamar98]

I'm the same as photosbykev. I use a rubber band. It works a treat!

[Beulah]

a wide rubber band that will cover some of the focussing ring and the adjacent static metalwork so it acts like a clutch

Was going to say this myself. Works really well and no pennies spent.

[Knight of Clear Skies]

a wide rubber band that will cover some of the focussing ring and the adjacent static metalwork so it acts like a clutch

Thanks, will give this a go. I was looking at hose clamps online earlier, but a rubber band didn't occur to me!

Less keen on the idea of buying another lens when I already have one of that focal length.  Good to hear there are no issues with the old M42 lenses though. I have an adaptor and a 35mm f2.4 lens I haven't tried for widefields yet.