Abell 30, the born again nebula

March has been a difficult month for me in recent years, 
a number of events have prevented me from completing this project, but finally,
here is my image of Abell 30, a rare "born again" planetary nebula who's central star re-ignited after turning into a white dwarf,
creating a new system of complex knots of oxygen (blue-green)
inside a mature spherical shell of hydrogen (red) and oxygen:

Abell 30 in Hydrogen (red) and Oxygen (blue-green)

The O III signal was faint, Ha signal extremely faint, and He II almost nonexistent.  

I was baffled by sources stating that the knots have strong He II emissions, e.g., 

Osterbrock's Astrophysics of Gaseous Nebulae and Active Galactic Nuclei p. 264.

My He II filter is spec'd at 468.6 nm with a 4 nm band width detects almost no signal in the outer shell, but did detect signal in the small knots closest to the central star.  My best guess is that "helium rich" refers to the relative ratio of He II to Ha in specific areas of the nebula.  Here's a mosaic of images with the various filters displayed using the linear stretch that best displayed the central knots.  The continuum filter removes the narrowband emissions of the nebula, showing only stars in this case:

Abell 30

Edited the section above (a filter wheel error on my initial attempt substituted a continuum filter for the Helium II filter).

A few findings regarding exposure variation and binning:

for OIII 3 nm 

40 min binned 2x not much deeper than 20 min binned 2x, if at all.

but 

20 min binned 4x (4 subs) much deeper than 40 min binned 2x (2 subs)

though it was difficult to be sure conditions were identical.  

filter band width:

for 40 min binned 2x 3 nm OIII deeper than 5 nm or 8.5 nm; not much difference between latter two

older unbinned subs with my SX H9 (0.6"/px) were far worse than either, threw all subs out

8" LX200R, SX Trius 694 binned x2 to 0.8"/px, binned x4 to 1.6"/px, (final image at .8"/px)

astrodon 5nm Ha, 5nm, 3nm OIII, chroma 4 nm He, 540x50 nm filter (greenish continuum) ; custom scientifics 8.5 nm OIII

ASA DDM60

OIII 10x 20 min bx4, 28x 40 min bx2, 44x 20 min bx2

Ha 2x 20 min bx2, 15x 40 min bx2, 60 x 20 min bx4

HeII 36x 1200s bx4 2x2400s bx2!

continuum filter 13x2400s bx2 (in error, black point 30K ADU!)

2/16/13-3/6/17

eastbluff, CA

crescents and earthshine

what's missing from my previous crescent moon image is this:

no, earthshine is not a drink served at california dispensaries.

Earthshine is a glow which lights up the unlit part of the Moon because the Sun’s light reflects off the Earth's surface and back onto the Moon, best seen during the crescent moon.  It is also sometimes called the old Moon in the new Moon's arms (or vice versa), or the Da Vinci glow, after Leonardo da Vinci, who explained the phenomenon for the first time in recorded history.

yes, i know this lies far in the realm of cub scout merit badges, but i was reminded of it when i tried to cut and paste an image of the first quarter moon for the eclipse test/comparison and could not define the edge of the moon.  i had to eyeball it by empirically fitting a circle to the part that was visible.

when the moon is a thin crescent, it means the moon is almost directly between the earth and the moon, so the part of the moon lit by the sun is mostly facing away from us, while the dark side faces us.  now from the lunar point of view, the earth is almost directly opposite the sun, so all the reflected light of the earth lights up the night sky (a full earth).  this light brightens the surface of the moon just as a full moon lights our nights, the "earthlight" makes the dark surface of the moon easier for us to see.

in an odd twist, astronomers have used earthshine to detect life on earth, testing a technique that could potentially be used to detect life on other planets.

while shooting this image, i turned my low power imaging rig on the "dusk star", the bright star visible at sunset this month:

caught a tiny crescent venus, matching the moon.

Technical notes:
web cam, DMK 51 and the tiny tak, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  The field of view is approximately 96x72 arc minutes.  Each image is a one minute video capture at approximately 12 fps, aligned in autostakkert, wavelets in registax.

crescent moon, hollywood style

What's wrong with this picture (click for full size)?

nothing really, except that the crescent is facing the wrong way. 

though few people can say which way the crescent moon should be facing

they have a visceral feeling that this isn't right.

when the moon is a thin crescent, it means that the sun is illuminating the side which is not facing us, so the moon has to appear very close to the sun in the sky: the crescent moon is seen just after sunset or just before sunrise, with the crescent facing down at the sun below the horizon (tips pointing up).  in the northern hemisphere it points down and to the right at sunset (looking west with sun setting in the southwest).  
you morning people may know that the crescent lies down and to the left in the east.  
it's the opposite in the southern hemisphere.
OK that was really confusing
here's a better description.  

for bad astronomy blogger Phil Plait, this knowledge turned his world upside down

DOH!
he concluded that springfield must actually be in the southern hemisphere based on this scene from the elon musk episode of the simpsons.


the only way the crescent can be on the top of the moon is if you're standing on your head, or in outer space where up and down doesn't matter.  or perhaps some strange partial lunar eclipse.


i chose this orientation as the unnatural rotation gives it a spacey feel
kubrick was well aware of this:

by the way, here's one of the most over-the-top analyses of a movie i've ever seen
tons of fun


but for the clouds you may see the crescent moon in the next few nights
take a look and see what's missing from my image
to be continued...




-bill w

Technical notes:
web cam, DMK 51 and the tiny tak, Takahashi FS-60C, 60 mm aperture at f/4.2 with a reducer.  The field of view is approximately 96x72 arc minutes.  Each image is a one minute video capture at approximately 12 fps, aligned in autostakkert, wavelets in registax.