Optical defects gallery - an idea.

[Shibby]

Here's some examples of coma, if this is helpful?

[Flying Eye]

Here's some examples of coma, if this is helpful?

Thanks very much for that, I do see it a little, and did wonder what was going on. I'd have to suppose it's going to be pretty common in cheaper optics, as that's what I have?

I'd also suppose if one could change the eyepiece then it might be improved?

I'm probably stuck with whatever causes it, but telling if you can improve it, and if possible, how, would be another helpful thing for the gallery to offer.

[Shibby]

Ian, ok, I'm no expert but here's a suggested explanation for when/if the feature comes about:

Coma is an optical defect inherent in all reflector telescope designs. Any light striking the mirror at an angle cannot be focused to a single point by all parts of the mirror. This often leads to "V" shaped deformations of stars, which gets gradually more exaggerated towards the edges of the image. Stars in the centre of the image remain unaffected, which is why the effect is not very noticeable when using high magnification eyepieces.

Coma correctors are available for both visual and photographic use - the corrector normally attaches to the front of the eyepiece/camera.

Faster optics are more prone to coma than those with a larger focal ratio. Some reflecting telescopes have correctors built-in to their design, such as the Skywatcher 190MN and most Astrographs.

One trick used by some astrophotographers without coma-corrected optics is to use the lens distortion filter in Photoshop to distort the image and improve the star shapes.

[Flying Eye]

Thanks very much for that extra information Shibby.

I was more making the comment that when or if this gallery gets started then that would be a good feature to have if possible, but you have gone that bit extra already and it's really helpful of course.

I'm seeing it in binoculars and a monocular and those are refractor devices, so it seems it can happen there too. Both being fairly cheap I'd imagine it's not going to be very amenable to being fixed (no where to add filters etc).

BTW liking your software.