Diffraction spikes with Skywatcher 80ED

[tarkanyigabor]

Dear Everybody,

I have just started astrophotography and I have noticed some diffraction spikes in my images despite I use a Skywatcher 80ED. This is primarily present in corners, especially the upper right corner of the image (picture enclosed).  Their placement was similar during two different occasions with different camera angles. I have nice round stars without spikes in the middle. My imaging train is the following: SW 80ED, Altair Lightwave 0.8x flattener, T2/Canon ring, Canos Eos 450D.

Could you please help me with what the problem might be. I have read that it can be pinched optics, but I am not really sure.

 

Thank you,

Gabor

 

diffraction.tif

[ollypenrice]

10 hours ago, tarkanyigabor said:

Dear Everybody,

I have just started astrophotography and I have noticed some diffraction spikes in my images despite I use a Skywatcher 80ED. This is primarily present in corners, especially the upper right corner of the image (picture enclosed).  Their placement was similar during two different occasions with different camera angles. I have nice round stars without spikes in the middle. My imaging train is the following: SW 80ED, Altair Lightwave 0.8x flattener, T2/Canon ring, Canos Eos 450D.

Could you please help me with what the problem might be. I have read that it can be pinched optics, but I am not really sure.

 

Thank you,

Gabor

 

diffraction.tif 229.53 kB · 10 downloads

Rather than posting a link to a TIFF, just post a stretched JPEG. Many members are reluctant to open unknown files and some, like me, have slow internet connections. You'll get a much better response that way.

Olly

[Skipper Billy]

jpeg

[vlaiv]

Looks like astigmatism to me rather than diffraction spikes.

Pinched optics would produce this over whole field - if it's just corners, it probably has to do with field flattener / reducer. Maybe spacing, or tilt or similar.

[Martthebass]

Not easy to tell from the image but looks like a slight pinching caused by over tight collimating screws.  Usually more apparent when it's cold.  If it concerns you then return it or get it adjusted under warranty.  Not uncommon on fast doublets/triplets, my WO GT71 has it slightly when its very cold. 

[tarkanyigabor]

Thank you for all of you for the usefull answers and help. I think I will try imaging without the flattener and see what happens to figure out what part has the problem.

[MattJenko]

bit late to the party, but I always got some spikes from my ED80 on brighter stars which I attributed to the how the lens cell was held in place as there are very slight intrusions into the light cone. I never minded them.