Quote:
Originally Posted by multiweb
Absolutely superb.  All your hard work and dedicaton paid off and it certainly shows. I'm amazed at the sharpness of the details for such a widefield. How do you focus? |
I use a computer controlled stepper motor to focus the lens. The lens is held at a constant temperature by thermostatically controlled dew heaters. Focus is attained by taking test images 1000 steps apart (1000 steps is 0.15mm of focus ring movement). Once best focus is set not only does it not change for the night it is still at best focus for many nights as long as the lens and camera are equilibrated to their set temperatures. Typically 18C and -10C.
There is a reason for heating the lens body as it stops the filter in the lenses rear filter holder getting condensation due to the camera body being at -10C
Bert