Posts Tagged ‘comet’

Comet Catalina (C/2013 US10)

January 3, 2016 Leave a comment

Comets are difficult objects to capture and process, but the good ones are worth the effort. Catalina sits in the pre-dawn skies right now.  I’ve gotten up at 4am two mornings in a row to get this shot.  Yesterday, I captured it with Arcturus in the same frame, but I underestimated the comet’s dimness, so the final image was fairly dim and noisy. This morning, I doubled the exposure time with better results.

Catalina LRBG 3

LRGB imaging is not ideal for comets: even with 2-minute exposures, there is shift between them.  DeepSkyStacker comet alignment mode is great, but the color channels don’t quite line up perfectly. Next time, I’ll use a DSLR.

Image data:

  • Exposures: 52×2 min L, 18×2 R, 16×2 G, 17×2 B
  • Telescopes: Two William Optics Star 71s (360mm f/5)
  • Cameras: SBIG ST-8300M and QSI 583wsg, 2×2 binned
  • Mount: Takahashi EM200
  • Guiding: QHY 5L-II mono, guided using PHD2
  • Conditions:  light wind, nearby moonlight
  • Processing: DeepSkyStacker -> PixInsight -> Photoshop
  • Date: Jan 3, 2016

A Quick Look at Comet Lovejoy C/2014 Q2

January 23, 2015 Leave a comment

It’s not often that we get a bright comet so high in the sky.  Luckily, I was able to seize a couple of hours of clear skies to image Comet Lovejoy while it was in Aries.  I took separate L, R, G, and B exposures across a 1×4 mosaic, since I knew the tail could be really long.  This extended tail was also very dim, barely showing with 3-minute exposures.  Because comets are moving targets, I only took a single 3-minute exposure for each channel, then moved the field of view.  You can actually see the effect of this movement a little in the head of the comet, where the L exposure came about 20 minutes after the R.

Comet Lovejoy, Jan 20, 2015

Comet Lovejoy, Jan 20, 2015

It’s easy to lose your sense of scale here.  This is a tremendous field of view.  Below is one of the uncropped mosaic images used to generate the above. Each of the four overlapping frames you see is 2.9 x 2.2 degrees, so the total field of view is around 7 x 3 degrees!

Uncropped mosaic view

Uncropped mosaic view

Image data:

  • Exposures: 1 x 3 min L, R, G, and B exposures in a four-part mosaic
  • Telescopes: William Optics Star 71 (360mm f/5)
  • Cameras: SBIG ST-8300M, 2×2 binned
  • Mount: CGEM
  • Guiding: QHY 5L-II mono, guided using PHD2
  • Conditions:  calm
  • Processing: DeepSkyStacker -> PixInsight -> Photoshop
  • Date: Jan 20, 2015

Comet Garrad (C/2009 P1) Animation Video

September 2, 2011 Leave a comment

Comets move across the sky too slowly to notice while watching, but enough that the motion over a night is clearly apparent.  What better way to see this than with a time-lapse video?

Comet Garradd was discovered in 2009, and it has gradually brightened since then to the point where it is now visible in binoculars in the constellation Sagitta.  It’s still a small and dim comet, but it should brighten through next spring.  The video here shows the view through an 80mm f/6.3 telescope over the night of August 30th from my light polluted skies in central NJ. The field of view is about 2 degrees wide, about the width of four full moons.   The video starts at 9:55pm, when the comet is close to the zenith (straight above), and by 4am, it is lost in the trees across the street from me. Every three seconds in the video corresponds to an hour of time.

The equipment used:

TMB 80 SS triplet refractor, f=503mm on a CGEM mount.  Canon 450D XSi modded camera.  Autoguided with Meade DSI through a 50mm finder with PHD software.

4 minute exposures at ISO1600, calibrated in DeepSkyStacker, batch processed in Photoshop CS3, compiled into video with Windows Movie Maker.

The nice blue-green color of the comet doesn’t show well in the video, but a stacked image aligned on the comet shows the colors nicely:

Comet Garradd, 86x4min, aligned on comet

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