Collimating the C14 with a tri-Bahtinov.

Finally clear skies with a half Moon yesterday! so perfect for fine-collimating the C14.

Last week, astro-friend Erik (Hemiksem) could lasercut two tri-Bahtinovs, one for F11 native and one for the F7.5 configuration using the Starizona reducer.

This was the intial image before collimation:

Tri-Bahtinov image of the C14 before collimation

As can be seen on the image above, the collimation is pretty good, actually near-perfect. The principle of a Bahtinov is that the middle line is perfect in between the two outer lines. A Bahtinov does that with one axis (on set of lines resembling a star), and a tri-Bahtinov does that on three axis. By aligning the Bob’s knobs with the axis of the mask, you can easily adjust each knob untill the coïnciding middle line is perfectly centered.

Closely looking at the starting image, it’s clear that the 10 o’clock-4 o’clock axis line is a bit off. After some small tweaks with the corresponding knob it looks as follows:

A possible pitfall is that the collimation already needs to be near-perfect for this procedure to work. A SCT can be misaligned but still show an aligned tri-bahtinov. So take care to collimate as perfect as possible visually on a star first.