Moon shaped stars

[wuthton]

Could anyone with camera lens knowledge educate me as to what caused the moon shaped stars in the following image? It was a borrowed lens that I've now given back and it was a lot shorter than I wanted but I'm still intrigued. I'm assuming that stopping it down would have helped but I didn't have a Canon body to do the deed.

Canon 24mm/Atik 314L, 55"/pixel

Baader Ha filter, 12 x 10min subs with no calibration frames

[bogdog]

Quote

I'm assuming that stopping it down would have helped

correct

you could cut a peice of card to cover the front of the lens,then cut a smaller diameter hole in centre of the card to allow less light in

or pick up a cheap m42 lens,which you just use the manual stops on 

[wuthton]

4 minutes ago, bogdog said:

correct

you could cut a peice of card to cover the front of the lens,then cut a smaller diameter hole in centre of the card to allow less light in

or pick up a cheap m42 lens,which you just use the manual stops on 

Gah! I should have thought of the card trick last night.

Do you know what causes the flares though?

[bogdog]

no idea,maybe just the brightness of the stars reflecting on the glass elements

but with it stopped down it should reduce them same with halo's