Eta Carina HOO

[pkinchington]

Eta Carina HOO 79x60s Ha + 128x60s Oiii. What is causing the aberration in the large bright star in the lower LHS?

[JA]

That is caused by aberrations in the lens / optics most likely a mixture of some coma and astigmatism / sagittal coma flare.

You don't say what optics you are using, but stopping down the lens or optics can help reduce it or you can reduce its appearance in image processing.

Best
JA

[pkinchington]

Hi JA using sharpstar edphii 61mm refractor with matched 0.82x reducer/flattener giving 275mm f4.5 telescope with qhy filterwheel and Ha and Oiii filters.
Cheers Kanga

[Nikolas]

The reducer would be the culprit

[pkinchington]

Hi Nik,
In what way - faulty or spacing iissue etc?
Cheers Kanga

[Nikolas]

From what I have read about these and seen on youtube they can be prone to a little CA in the blue channel as there was a batch that did this, there was also talk of very minor aberrations.
I'm after one of these scopes as they are brilliant and the newer reducers seem to have been sorted.

[pkinchington]

Thanks Nik - I will have to get back to Jamie at Testar to see what is going on and get a replacement.
Cheers Kanga

[Nikolas]

Look at these videos
https://www.youtube.com/watch?v=6a6S6lMwooQ
https://www.youtube.com/watch?v=RhaGObIsR9Y
https://www.youtube.com/watch?v=pZ7N_-0AqGA

[Spaceman_Brown]

Cooooool!

[pkinchington]

Thankyou Matt,
cheers Kanga