The many shapes of Alnitak

[John_Gill]

Hi,

Attached is my first venture into NB photography.  The image has only had a Histogram stretch.
Captured with APM apo 107/700 scope and ZWO 1600MM (mono) camera with a Ha filter.
The exposure was for 300 seconds and a gain of 75.

Can someone explain the multiple shapes of Alnitak and how to avoid this in the future and
perhaps how to fix this now ....

space is not black
John

[pfile]

there is a good thread on cloudynights about this:

https://www.cloudynights.com/topic/635937-microlens-diffraction-effect-explained/

rob

[John_Gill]

Thanks Rob.  Any ideas how to avoid this in future - beside not imaging near big bright stars .....

[Andres.Pozo]

Thanks Rob.  Any ideas how to avoid this in future - beside not imaging near big bright stars .....

The image has a very bad focus. The stars are like donuts. I would repeat the image, perhaps the diffraction patterns are less visible when the image is well focused.

[John_Gill]

Hi Andres,

I think you are right but it might also be a back-focus issue. I was processing the image and noticed that the stars are a bit long but guiding seemed to be fine. My previous imaging with a DSLR has produced nice round star to the edge of the images. So I will give it another try, as soon as the clouds go away.

Thanks for your help.
John