Saturday, February 14, 2015

planetary nebula IC 418: a blue gem in a red cocoon

here's my first light with a new ccd camera: starlight xpress trius 694
believe it or not i've never used a filter wheel before
just manually screwed one filter on, imaged for a few nights, then went on to the next
not a big deal for super long narrow band imaging, but inconvenient for quick bright planetaries
so the filter wheel that came with the camera is more of a novelty to me
than the larger, more sensitive chip
thus a quick shot of a bright planetary as first light.

after seeing IC 418 listed as one of winter's best planataries in feb S&T
i decided to revisit the red planetary with narrow band filters
as my prior rgb effort yielded nothing but a red disk with a brighter spot in the center

so here it is in NII/OIII/OIII:

it's difficult to make out the central structure at native image scale
so i upsampled x2
for a final resolution of (EDIT: 0.2"/px)  (makes a difference to my eye)
straight linear stretch with a bit of RL deconvolution

in OIII there is a disk with a subtle central brightening:

here's the NII which shows a central star with an outer shell:


difficult to say whether the mottling is noise or a hint of the spirograph pattern detected in the hubble image

interestingly combining the NII and OIII in a color image
seems to create an unsharp mask like effect
making the central OIII brightening (gem) more evident

prior effort (RGB 2007):

i also shot HeII subs but found only a very faint ring around the central star
seemed matched continuum filter images with equivalent exposure (accounting for bandwidth)
meaning it's either broadband glow or artifact such as reflections, corrector plate dust etc.

of course after imaging it i came across this on Jim Kaler's web site
indicating there are no HeII emissions:
"The low excitation nebula, with its relatively cool central star, does not exhibit He II emission lines (those of ionized helium), just those of He I (neutral helium)"
i believe this is taken from a 50 year old reference:
From L.H. Aller and J.B. Kaler, Astrophysical Journal vol. 140, p. 936, 1964.
so i'm a bit behind the times...

i also shot a 20 minute sub binned x2 in NII and OIII
and found no evidence of any other outer shell (didn't check Ha)

8" LX200R, SX Trius 694  0.4"/px
astrodon 3nm NII, 3nm OIII filters
NII 22x30s, OIII 20x30s
no AO no guiding

Thursday, February 12, 2015

Comet Lovejoy C/2014 Q2

caught a bright comet with an impressive tail in January:

The image frame is approximately 2 degrees wide, making this the longest comet tail I've captured as it clearly departs the frame.  Some images from dark skies show a tail spanning 19 degrees.  
This was shot through heavy light pollution and passing clouds (explaining the gaps in the star trails).  Nevertheless, the bright, twin tail structure is still visible.  
The comet was easily visible in binoculars, brighter than the andromeda galaxy, though i could not detect the tail.  
Here's a video of the individual frames complete with clouds and airplanes:
Note the comet tail follows the direction of the solar wind rather than the comet motion in this instance.   
Though fading a bit from peak brightness
It should still be visible early evening  in Andromeda this weekend with the new moon approaching

FS60C@ f/42. with SX H9C color camera and chroma light pollution filter.  60x2 minute exposures with mount tracking on comet (ASA DDM 60).