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Spikes are the least of my worries.

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#1 stargazer193857

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Posted 15 July 2020 - 01:20 AM

I pointed at Deneb and saw spikes in my 6". I wished they were not there, but they were not as bad as the multi-imahe star from my astigmatism. also, there was a glow around the star, probably from thin clouds. And of course coma near the edge of view.

My 80mm f5 refractor has better contrast, but is not as deep as the 6". So, spikes are not terrible. I don't see them on small stars.

As for a curved spider, if the spread light is anything like the glue I saw, then that would not be acceptable.

#2 sg6

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Posted 15 July 2020 - 02:07 AM

As a bit of a generalisation spikes come with bright objects, and reflectors are intended to collect light from dim objects so the actual dim object tends to not show spikes. If there is a star in the field then that might.

 

Would make it not ideal for Jupiter and Saturn and later I expect Mars, but for M1 and I expect M33 they are fine.

 

So it is a case of pick the target, with at least a little thought and understanding. M45 would have spikes everywhere.



#3 mac57

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Posted 15 July 2020 - 05:37 PM

Yeah, you will see spikes in a Newt, and rings in a Mak.  Very bright objects introduce these problems when a mirror is involved.  I got my Mak because my f/5 Newt had the spikes.  The Mak is f/12, so it's better for that sort of stuff.  Some people use curved spider vanes to help eliminate the spike problem, but I suspect that colimation is a bit touchier.  Mark



#4 stargazer193857

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Posted 16 July 2020 - 01:38 AM

I saw beautiful rings in a defocused star in my 5.5mm eyepiece. Looked about the same on either side of focus.

But in focus, I see my vision is not great. I need to fix my glasses. I look forward to viewing through the refractor again. Maybe my eyes focus better through it. They have before.


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