NGC 6888, the Crescent Nebula (July 2022)

 

This is not my first Crescent, but I wanted to see what I could get with an OSC and light pollution filter.  This is 15x1200" with the Atik 460EXC, Synta ONTC 203mm Newtonian at f/4.9, and the Astronomik CLS filter.

Crescent Close-Up (NGC 6888) (August 2021)

 

I love using my CFF 290 Classical Cassegrain.  Here is an image taken (at f/8.1, 2350mm) of the brighter half of the Crescent Nebula in Cygnus.  This is a full narrowband image.  I took three hours of H-alpha then spent a night on what I thought was O3 but which turned out to be S2---ouch (slip of the brain when controlling the filter wheel)!  The S2 is blended in here.  I finally caught another 3 hours of O3.  Total time: 8 hours 50 minutes.  The H-a and S2 subs were 20 minutes long; the O3's were 30 minutes each.

After I finished the O3 subs and the Crescent slipped behind the trees, I put a diagonal and eyepiece in the big scope and enjoyed a tour of Cygnus.  Highlights included the Owl Nebula and Phi And (0.5" clean split; truly awesome to see those little diffraction patterns so close together).  As always, the scope performed like a champ.  I started observing at 3:30 a.m. and made myself put it away at 5.  I had to sleep sometime.

Crescent Nebula, NGC 6888, in Ha (June 1, 2012)

Full-resolution image here.

The moon was 90% full, but one can shoot H-alpha under the moon.  This is the Crescent Nebula, or at least the part made up of excited hydrogen (and perhaps nitrogen).  What you see here is essentially a large front of excited gas created by the movement of a bright, active star (the one at the center of the nebula) through a cloud of hydrogen.  The brighter part looks more like a crescent; the name matches visual observations.

Flats were taken with an Alnitak Flat-Man, which just arrived.  I used one of these two years ago and always thought it the perfect solution.  Last night's use persuades me I was right. This is also the first image I've taken with an H-alpha filter through the Orion 6IN.  And it's the first time I've stretched subs to 20 minutes.  I should have done 30 minutes, I think, and will try to with the OIII, or with more H-alpha, if I try to gather more data on this object.

Telescope: Orion 6" f/5 Imaging Newtonian and Astro-Tech Coma Corrector (eff. at f/5.5)
Camera and Exposure: 13x20' thru the SXVF-H9, Alnitak Flat-man flats
Filter: Astronomik 12nm Ha [+NII]
Guiding: SX Lodestar and SX OAG
Mount: Takahashi NJP
Software: Nebulosity, Maxim DL, Photoshop CS3
Location: The Woodlands, TX