Cygnus in H-Alpha light

sellotaped the lens focusing ring

A good solid engineering solution then

When you get the pier sorter and the mount properly polar aligned, we'll be seeing some pretty stunning images I suspect

Dave

I have now taken an image in daylight at a distant object, sellotaped the lens focusing ring and turned the focusing switch to manual. Hopefully this will help.

The best way is to focus before you start shooting at night. Manual focus is as you are finding very difficult. The best solution is to focus using software just before you start shooting.

Various software based focus applications exist including;

Maxim/DSLR
K3CCD
ImagesPlus

If you rely on the focus on infinity then tape method you are betting that the lens will not loose focus as it cools down. You might be lucky

Later,

Jed.

Jed,

I haven't used these software packages to focus the 300d before. How do they determine the best focus position? Do they take a FWHM measure on a star?

Regards,

I haven't used these software packages to focus the 300d before. How do they determine the best focus position? Do they take a FWHM measure on a star?

Hi Michael,

Yes most provide either FWHM or luminance values (brightest is in focus). Very easy to use after the first couple of goes, and it takes the guess work out of it.

Later,

Jed.

I have Imagesplus so might give it a go with this. Must check the tutorials on it again.
Cheers Jed,