Strange Light Rays

[Geoff Barnes]

Bit of an odd one this. I've recently noticed during my last few sessions that I'm getting these strange light rays emanating from Jupiter and Saturn in a broad cross shape. I know about diffraction spikes from bright stars from the secondary support arms, but this is different. The light rays extend from the body of the planet at the same width and gradually fade as they extend out into space. 

It is happening with all my EP's which I keep spotlessly clean so I know it is nothing to do with them. I've also cleaned the secondary mirror which was a bit dirty but this has had no effect. The only thing left to clean is the primary, but that was cleaned a few months ago and is still pretty well spotless. 

I'm at a loss as to what is causing it, I certainly never used to see this cross of light from planets, so any ideas from you folks as to what it is?

I've done a quick sketch of Jupiter to give an idea of what it looks like....

Edited September 27, 2019 by Geoff Barnes

[vlaiv]

Same thing - diffraction spikes.

We see them readily on bright stars and there they look, well, like spikes. Now imagine that planet consists out of bunch of stars (it is not solid but rather has "points" that make it). Imagine diffraction spikes from each of those stars overlapping. They will form exact pattern that you are seeing.

Here is a little diagram to explain it a bit better:

(sorry for poor star shapes, my drawing skills are in need of collimation )

 

[Geoff Barnes]

Yes that's what I thought Vlaiv, it's just that in the past Jupiter and Saturn were seen without the spikes, just clear blackness all around their discs. Very odd.

[Kn4fty]

I've had that happen before. In my case Jupiter was starting to move behind a pine tree. I was getting views between the needles.

 

Rob