Sh2-155 (Cave Nebula)

Data gathered between 17th June & 4th July






www.kinchastro.com/sh2-155-cave-nebula.html

It truly looks like a cave alright.

What constellation is that in? New nebula to me.

Beautiful image. Thanks for posting.

Clear skies,

Aubrey.

Thanks Aubrey.
It is in Cepheus. If you can - follow the link under the image. On that page I have some info (as usual making use of Wikipedia) but also put 'sky plot' diagrams - showing the exact position.

Beautiful image. It's a nebula that I had not heard of before.
Even more challenging with the long Summer nights.

I wonder what the Garnet Star (Mu Cephei) would look like in one of your images, Kinch?

In the past, I have tried to give an estimate of its varying magnitude.

Aubrey.

No idea what it would look like Aubrey but I do know that it would give me no end of trouble

Generally in the Nebulae shots I try to reduce the stars so that the nebulosity stands out - rather than the stars. Big bright stars give me 'trouble' because in the different narrowband filters they turn out different sizes - and when combining the three (Ha, OIII & SII) I get artifacts on the edge of the larger stars. In this image (Cave Nebula) you can see star HD 216945 (just above right of center) has a red hue to the edge. This is because the Red channel star (Mostly SII) is bigger than the star as it comes out in the HA or OIII subs.
So, regardless of other considerations - I think I would make a right mess of the Garnet Star in a narrow band image. RGB would not be such trouble - if I ever get it in any of the shots I do, I'll be sure to draw your attention to it.

Brendan.