Annoying refraction spikes.

[JohnH]

Are you an electronics tinkerer?
If so, just run a clear led underpowered until it just glows, should be small enough to get you going as an artificial star.

The other way which i've used is a home made fibre optic made from glass blowing glass, just hang a weight heat it up and let it draw out.

The other one you could do which might be cheaper is to actually get a fibre patch chord.

Mac.

My best bet is optical fibre - I have some 0.25mm that was sold by a model shop.

John

[MarkS]

Take an image of an out-of-focus star - both inward and outward.  The images should look like a bright doughnut with the shadow of spider vanes crossing.  If you see any other "shadowy lumps" (like nuts, bolts or focuser) cutting into the doughnut then the cause of those shadowy lumps is likely the cause of your diffraction spikes.

[Edit: I've just seen your other thread : http://forum.orpington-astronomy.org.uk/index.php?topic=12451.0  Assuming it's the same scope you clearly have additional shadowy artifacts in your out of focus stars.  These could be causing or contributing to the diffraction spikes]