SCT Image Shift Solution

Hi All,

I just thought I would share my simple solution for SCT image shift. Since I refuse to pay the high price for some aftermarket focusers I made my own. It's a simple helical focuser. It drops into my existing 2" diagonal. It was made for 1 1/4" eyepieces. The threads were precision machined for a nice smooth fit. There is no play even when extended to 1 1/2". I use the main focus knob on the OTA for rough focus and the helical for fine focus (high power planetary observing). For visual use it works quite well. I tried to find something like this in the aftermarket arena but found nothing.

I didn't spend the time to knurl the focuser since the eyepiece thumbscrew acts as a fine focus knob.

I also use the helical focuser when I want to mimic the waves of defocus in Aberrator. I can do it easily now since I know the thread pitch (12). One turn is .083" of defocus and if my calculations are right this comes out to 4.79 waves.

Keith

Attached Image:

Minimum focus.

Attached Image:

Maximum focus.

Attached Image:

Keith,

Nice idea. Hopefully I can do the same. Thanks for the tip.

Regards,
-JW:

Nice job of machining. Orion sells something that works similarly but it does not look nearly as nice as the one you made.

"...I also use the helical focuser when I want to mimic the waves of defocus in Aberrator. I can do it easily now since I know the thread pitch (12). One turn is .083" of defocus and if my calculations are right this comes out to 4.79 waves..."

The approximate wavelength of green light (550 nanometers) is 0.00002165 inches so one turn of your focuser would be 3,849 waves.