Anti-flare mirror mod

[JD2439975 (Justin)]

This is something I meant to share ages ago but never quite got around to it...I think it was when my THIRD hand control died after two EQ6 mount failures & I lost the will to live.
But I'm over that now...hopefully.

So back on subject, I had some nasty effects from my mirror clips showing in star flaring (probably a more correct term but it escapes me).
I made a plastic ring with a felt inside edge that slips under the mirror clips, stopping them from showing, it also blocks the edge of the mirror which must have some small grinding errors/chips (these aren't real chips just that grinding glass up to a pointy edge must have some errors in it surely).
I do lose a couple of percent in mirror area but that's OK if it looks better.

But I'll let the pictures speak for themselves, the last is a before & after comparison of Antares.
I think you'll agree a much cleaner star image.

I had wondered if using a more precision cut, non felt covered ring would give a circular diffraction "spike" like I've seen in some images. (baffle interaction??)

[RobF (Rob)]

Very very interesting Justin.
Would be interested to hear if anyone else has experienced this too?

[asimov (John)]

It used to be a common problem back in the 'good old days' A lot of mirrors had turned down edges, so there used to be a lot of stopped down scopes around.

[Wavytone]

Actually what you have done is perfect - and turned down edge is not the real issue here.

If the aperture stop is not a smooth circle, you will get a lot of scattering as is evident in the lefthand image; making the aperture stop a smooth perfect circle results in a lot less scattering as shown in the right image - and you have hidden the three mirror clips as well.

The typical Newtonian mirror has a bevelled edge ground with a coarse grit, which means that without anything else, the edge of the mirror acts as the aperture stop - being rough, it scatters a lot of light and degrades the contrast on planets too, BTW.

[JD2439975 (Justin)]

That sounds good, I could do with sharper images on my planets.
EOS Movrec doesn't record the best quality avi's so I need all the help I can get.

[AlexN]

Mate that is a really good improvement... Antares looks beautiful in the second image....

Job well done!! I would say don't bother going any further than that, or changing it in any way... looks like you've achieved what you set out for...

Alex.