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What is this 'flare' around Vega?


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I've recently gotten a new Skywatcher 200pds and whilst testing it out i noticed this weird 'flare' around the star. My best guess is that it is something to do with collumation and because this is my first newtonian im new to this process. I don't know how to get rid of it.

 

Anyone know and can help?

Thanks 

 

Vega (2).jpg

Edited by _steffastrostuff_
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My take is that it looks to me as though the secondary is a fair distance away from where it should be. One edge is deep in the light cone, and its rough-ish edge is causing all that extra diffraction. And the other side of it is way outside the light-cone,  therefore causing no diffraction at the other side. Those two extra gaps are 120 degrees apart, which suggests that 2 of the 3 mirror clips are causing them.

M

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On 26/10/2020 at 11:05, _steffastrostuff_ said:

I've recently gotten a new Skywatcher 200pds and whilst testing it out i noticed this weird 'flare' around the star. My best guess is that it is something to do with collumation and because this is my first newtonian im new to this process. I don't know how to get rid of it.

 

Anyone know and can help?

Thanks 

 

Vega (2).jpg

It's the focus tube pushing back into the light path a common issue when imaging with the PDS range. 

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10 minutes ago, _steffastrostuff_ said:

Is there a way to correct this without cutting up my scope?

Sorry, No! :crybaby2:

But, seriously, it's most likely a straight forward collimation issue - the alignment of the mirrors.

Collimation is a skill that Newtonian owners eventually learn or they sell their scope! I think a fair few have taken option 2 over the years.

Depending how you assimilate knowledge best you could Google for either pictoral or video tutorials. Once you "get" it you'll wonder what the fuss was about. No doubt there are plenty of excellent books on the subject also and there must be hundreds of thread here on SGL to whet your appetite.

I taught myself on my old Fullersope, I just worked out what the concentric reflections should look like through the focuser draw tube and twiddled till I got there. My newer 250PDS is more challenging. I tried a laser collimater but never got on with it. A Cheshire eyepiece suits me better but I'm still happiest with a simple collimating cap. These are terms that will become "earworms" in you scope owning life! 

 

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Just a quick note , if the focus tube is too far in have you taken out the extension section of the focus tube.

When using a DSLR on my Newt I had to unscrew and remove the lens holder , unscrew the extension section (was about 50mm as I recall) then screw the lens holder back on to take my DSLR nosepiece.

This way with enough infocus for the DSLR the tube base did not intrude into the light path.

 

The thin join between the extension piece and the main tube can be almost invisible so you dont see it is there sometimes.

 

Having said that I suspect collimation is the thing to check first.

 

(and perhaps your tube does not have an extension piece anyway

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