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Collimation gone wrong

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To make long story short i will get straight to the point.This summer after traveling a long diastance aprox ~600km my optics were out of collimation.Specifically the secondary had lost its tilt.I had never touched the secondary since i didn't use to travel that much.Anyway i started "playing" with it, i was in the mood for " what will happen if a unscrew this screw " and so i began to play with the tilt.I also "touched" the center screw of the secondary mirror looking for the best possible possition (reflection should be a perfect circle).I think i am now in a good state of collimation but i would appreciate if you could find any problems beside the one i will state.

This is a recently picture of my collimation through my collimation cap.


The collimation seen in the picture hasn't changed that much since i took the picture.I know it is not the best picture but i hope you can make sense from it.

How am i gonna make the center black ellipse turn into a circle with equal black shadows surrounding the very center reflection of the cap?

PS i do not own any other collimation tools and i currently do not have the scope with me so i cannot take other pictures and/or make any adjustments.Was hoping to gather as much information as i could before i touch it again.

Thank you and clear skies to all of you.

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The centre black ellipse as you describe it would be normal for faster newts, say f5 or faster. Take a look at the following links, they may help:



For the second link, you may need an account on Cloudy Nights to automatically see the attached diagrams. You probably don't need to read the entire thread (it seems to descend into a bit of bickering), but the first few pages are certainly useful.

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Hello Andy.

I have made the same topic in CN too. One suggested action was to "square the focuser".But i will not touch the focuser.I know i will make things only worse.

So is it normal that it is an ellipse?Or does it need adjustment? In Astro baby's guide it does say something about the offset but in f/5. Mine is f/6 and is a big offset i suppose.

Thank you and clear skies.

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To the OP, your secondary mirror positioning looks OK. Leave it as is.

Ideally, the secondary mirror silhouette is circular but shifted which gives the illusion it is elliptical.

You can't have all reflections concentric. If you center the secondary mirror silhouette then your secondary mirror will look off-center.




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