NYE Pleiades

[Plossl68 (Paul)]

Too long since I was out trying Astro… same old story: new job, never a good sky when you have any time etc….Anyway, we were away in Daylesford for NYE with nice Bortle 4 skies. It was windy but clear and I managed to catch 20 x 2min subs of this favourite before it dipped behind the trees. Don’t look too closely as I’ve teardropped the stars (wind?).

Redcat 51
Zwo 2600MC (love this camera!)
SkyGuider pro
20 x 2 min light
20 x 2 min dark
No flats or bias
Stacked and processed in Affinity Photo.
Now added a second version, processed a little further to draw out the nebulosity from the same data.

Any and all feedback welcome.
Clear skies,
Paul

[Mickoid (Michael)]

Paul you have definitely brought out more nebulosity with your second process but at the expense of increasing noise and colour balance due to the stretch. This occurs because you have limited data to start with and those areas which received less signal have a higher noise ratio. There are ways to hide this effect but ultimately it is much better to have more data to start with. If this dismal weather clears over the next few days just gather more data on the object and add it to what you already have. You will then have much more to play with and the nebulosity will be revealed without having to stretch the image so much. It looks like you have your equipment working well with nice tight stars, so you're off to a good start!

[Plossl68 (Paul)]

Thanks Michael,

I appreciate the advice and will look for opportunities to gather more data. Do you have any thoughts on the teardropping of the larger stars please? It was windy and the SkyGuider is pretty light so I was thinking that was it, but is there something else that I’m missing?

Originally Posted by Mickoid

Paul you have definitely brought out more nebulosity with your second process but at the expense of increasing noise and colour balance due to the stretch. This occurs because you have limited data to start with and those areas which received less signal have a higher noise ratio. There are ways to hide this effect but ultimately it is much better to have more data to start with. If this dismal weather clears over the next few days just gather more data on the object and add it to what you already have. You will then have much more to play with and the nebulosity will be revealed without having to stretch the image so much. It looks like you have your equipment working well with nice tight stars, so you're off to a good start!

[Mickoid (Michael)]

It looks like you have your equipment working well with nice tight stars

I hadn't looked that close when I posted this. You do have 'Eggy' stars which are most probably caused by mount tracking error. If only a few subs you took has these odd shaped stars, then it could be wind or mount PE. A 2min exposure is a lot to ask from an unguided SkyGuider Pro mount at 250mm focal length. Wind or no wind your Polar alignment would have to be very accurate to achieve round stars over 2 mins. Try cutting the exposure back to 1 min and just do more of them

[Plossl68 (Paul)]

Thanks Michael,

My bad. I should have said I was guiding via an ASIAIR+ which indicated guiding error of about 0.5 RMS. There is a bit of variation between the eggyness of the stars between the subs too. The final thing is that I suspect I might be stretching the weight limits of the SkyGuider Pro. With the RedCat + EAF + camera, I had to add the balance weight extension arm and addition weight to balance in RA. Being at the limit if it’s capability can’t be helping

Originally Posted by Mickoid

I hadn't looked that close when I posted this. You do have 'Eggy' stars which are most probably caused by mount tracking error. If only a few subs you took has these odd shaped stars, then it could be wind or mount PE. A 2min exposure is a lot to ask from an unguided SkyGuider Pro mount at 250mm focal length. Wind or no wind your Polar alignment would have to be very accurate to achieve round stars over 2 mins. Try cutting the exposure back to 1 min and just do more of them