Is this for fine focus ?

[Mikel56]

Attached is a photograph with an eyepiece to the left and a “unit” to the right.

I have been looking for something to help me with fine focus and avoid a lot of image vibration, particularly on the Celestron 9.25. In a box I found the unit shown on the right of the photograph. It is graduated in mm from 0 to 10. When the knurled section is turned fully from 0 to 10 the unit extends by a measured 1 cm. I added the unit to the Swift 831. I can focus the Swift roughly by using the drawtube and indeed if I get that initial focus more or less correct for my eye I can fine focus with the unit however there’s not a lot of room for error. Is the unit designed for this purpose or something else ? If not would it be better to source a unit specifically to aid focus, particularly for the Celestron ?

Thanks,

M

[StevieDvd]

It's a helical focuser. Usually used when the scope has a rough focuser like a pull/push out and this does the final focus with finer precision. Some finderscopes have them like this one.

 

 

[Mikel56]

Thanks Steve. It’s good to know I’m using something for which it was designed !