strange diffraction spikes on bright star

[Daniel-K]

last night thought i would have a go at the horsehead before the cloud rolled in only managed 4 subs but look at the star next the flame nebula it looks like diffraction spikes not on any other images with bright stars. any one know what causes this? the image is a single 250 sec sub iso 800

thanks

[Dave S]

Do you use a bahtinov mask for focusing? The diffraction pattern is identical.

Dave...

[Keiran]

Do you use a bahtinov mask for focusing? The diffraction pattern is identical.

Dave...

Thats the first thing that came to mind

[Daniel-K]

no mask just backyard eos

[ollypenrice]

This is not 'a' bright star, it is 'the' bright star, the most consitently pestillential one in the whole sky, one which explodes over everyones' image of the Horsehead! Let's look on the bright side; you have resolved it as a double in exquisite detail, something we rarely see. That is incredibly difficult in refractors, by the way. So well done for that.

Yes, you have some spikes. This would have been the small hours with damp building up in the air and on the glass, perhaps? This can enourage all kinds of artefacts. It might be no more than that if you haven't seen it before.

In the scheme of things that is not a bad Alnitak at all and in thoroughly dry conditions might have turned out fine.

The other cause for such things is something intruding into the light path. Lens clips, drawtubes (in Newts) etc etc. Unlikely in this case.

Olly

[Daniel-K]

i dont think it was dew i had my dew shield on and i was blasting it with the hair dryer every now and again to keep the dew off. very strange indeed will try again later in the year when its up earlier. i didnt even notice it was double looks neat though

[ollypenrice]

Ouch, hairdrirers are a bit hard on optics! Dewstrips do the job gently. That might be your problem.

Olly

[Moonshane]

at least you managed to tease the HHN out of the murk.