[Jason D (Jason)]

Originally Posted by MrB

Hi Ghassan, many thanks for posting, your contributions to newtonian collimation are much appreciated! I have read your threads on CN and posts here and on Stargazerslounge. I have to admit I am still digesting your postings on CN!

Wow… Thanks…

…and I measured the spot as being out ~0.5mm, I then rotated the cell(incl. mirror) 90 degrees and measured again, this time it was 1.5mm out. I could've continued around the mirror to find the maximum but that would've been pointless.

On a 154mm mirror, this (and the wonky triangle) was enough for me to remove the old spot and place a new 'hotspot'.

Glad that you fixed that issue. I would not have felt comfortable with that much error in the original placement.

Yes there was vignetting by the tube when the offset was toward the focuser.

The tube is 190mm inside diameter with a 154mm mirror, the focuser centre is 180mm from the front of the tube.

Vegetating does not seem to be a possible issue.

If I remove the autocollimator from the focuser and hold it by hand above the focuser drawtube and carefully moving the autocollimator around, I can get all reflections to line up perfectly thru the on and off-axis pupil holes.

I think some of my issues are due to the autocollimator being about 85mm inside the focal plane(reflection '2' is grossly enlarged), I am machining a spacer today to move the autocollimator out to the focal plane.

Sounds you have a good understanding of the dual-pupil autocollimator functionality. Yep, when you are below the focal plane by that much then reflection 2 will become much larger and aligning reflection will be more challenging. Adding an extension tube as you are in the processing of doing will ease aligning reflections and add accuracy.

My tools are home-made on my lathe, they are equivalent to a Blackcat XL and an Infinity XLK with your offset viewing pupil.

Their accuracy is fine, I have tested the autocollimator as you described in a post on Stargazers Lounge(Here). There is zero image shift of the hotspot reflections when I rotate the autocollimator in the focuser.

If your home-made autocollimator passes that stringent criteria then you have build a quality autocollimator.

Jason