Collimating the C11 & ASI290MM

It’s been a while that the C11 was put to use, today I could clean the corrector, and also I found the very very small engraved numbers close to the edge, that line up with the line (and the same number next written next to it) found on the back of the primary. With the tri-bahtinov I could focus and collimate the optics. See also the links here and here.

make sure the three area’s of the mask line up with the three collimations screws of the secondary. The procedure is to focus like a normal bahtinov (ate least one set of lines), and then to look for the area (one of three) where the central line is not nicely central between the spikes. That becomes easily visible when covering an area: when that dims or obscures that is the guilty area, and the corresponding collimating screw needs to the turned (very very slightly). You see the effect on the central line. When centralized, repeat for the third area when necessary.

This is really easy, choose a star high in the sky. On the accuracy of this method I have little data or calculations unfortunately. What I do see is that (with a star in-focus) a very slight turn on the collimation screw (Bob Knob’s in my case), like 1/8 of a turn, gives an immediate effect on the Bahtinov image. The lines across the three sections will not be symmetric anymore. The area that corresponds to the collimation screw that was changed, will display a Bahtinov cross that is not centralised. From this observation I do believe that this method is accurate enough for collimating a SCT.

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A nice little galaxy group in Canes Venatici

This picture was taken arbitrarily in Canes, looking for a test object to verify the corrections I did to the optical train. In the previous image (M3) I noticed some tilted focal plane. That was due to an extension ring which was not tightened enough. The main galaxy here is NGC5353

The Leo Triplet

This is a group of galaxies in Leo, the Lion constellation that dominates spring nights. M65, M66 and NGC3628. At distances of 35, 42 and 37 Million light years, they form a fysical group in space  Tidal forces rip apart the extremities of NGC3628. The smallest galaxy identified in this image is PGC1423398 at a distance of 2 Billion light years: so glad those fotons travelled that distance in space & time only to get caught in my camera!! 

Picture with: C11 Starizona LF SCT reducer F 7.2 FL2010mm Nikon D750 FF Optolong L-Pro 2″ 800iso 27x600s

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