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Weird star shape. Help requested pls

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Posted (edited)


The APM UK retailer has been great and very much onside with trying to fix my teardrop star shape issue. The first high mag image was taken by APM having recollimated the cell after finding the lenses to be stuck together when the front retaining ring was slackened and noted the following:

“The attached image is a 10µm star at 78x magnification. It is a 5000 frame stack taken with a colour camera. If there was any trace of misalignment or pinching it should be visible as this is a high contrast, high resolution image.”

Does anyone have thoughts on the flat edge, top right hand quadrant of the first image, and if this is related to the pointed extension on the top of the central star image? 

This was in fact the subject of my original star shape enquiry (see the remaining images attached). These where my own more crude star tests to show a flattened edge. The UK APM Retailer who has the scope for correction say of their high mag image (first image below):

 “In any case this image suggests a very well aligned optic with no issues. For imaging you will be at 1x or less so you will never see a star in this detail”

That may be the case for the diffraction rings but star shape is my bigger concern and it seems odd for a round object viewed through a round optic.

By way of comparison my reflector shows a similarly scaled flattened edge effect when the focus tube impinges on the FOV but that’s a big piece of kit getting in the way and refractors are not configured that way. But I have visually checked the tube and I could not see any thing that would clip the star image.

So what’s going on here?

Is this what is reasonable distortion for optics of this class?







Edited by PadrePeace

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