Omega Centauri

[avandonk]

Yes Greg. The focal ratio myth is really a myth!

It is all down to lack of understanding or carefully defining what is really being discussed.


If I was to prove it totally, the Airy Disc is immaterial for an infinite evenly emitting object imaged by an optic of a given aperture.

The real world is not like that.

In the real world all point sources look like Bessel Functions in our best optics with a circular entrance aperture.

The Airy Disc is merely the first maximum peak of the Bessel Function.

For an extended object of even emission the resultant image is just all the Bessel Functions of each point overlapping to produce a what looks like an even field of illumination.

Bert

[Eden (Brett)]

Nice work, Bert. The cluster actually looks like a nice spheroid instead of just a flat disk for a change.

What caused the rainbow arc at the bottom of the image?

[avandonk]

Originally Posted by Eden

Nice work, Bert. The cluster actually looks like a nice spheroid instead of just a flat disk for a change.

What caused the rainbow arc at the bottom of the image?

Any bright star outside the recorded field of view can cause internal reflections that are very nicely recorded by this very fast system. It is just photons sneaking past the baffling of the folded optics. If you eliminate this problem by increasing the optic's baffling you end up with a far slower system.

I do have an extended 'dew' shield which limits the amount of sky seen by the optics to just the bit that is being imaged.

I am in the process of designing a far better carbon fibre tube extension with multiple internal baffles and a perhaps a variable entrance aperture.

Bert