Comet C/2014 Q2 Lovejoy is still visible in the sky in the constellation Cassiopeia. It is not as bright as it was a few months ago but can still be seen with a pair of binoculars. It is probably best viewed in the evening as Cassiopeia moves lower in the sky overnight and in the early morning hours. This makes it more difficult to see as there is more atmospheric attenuation at these lower elevation angles.
Sky map for locating Comet Lovejoy (03/22/2015) using the free and open source Stellarium planetarium software.
Using my recently acquired iOptron Skytracker for tracking night sky objects I took numerous exposures totaling 14 minutes (9x60s@iso1600; 10x30s@iso3200). These were then stacked in Deep Sky Stacker (DSS), a very good and free program designed for astrophotography.
Comet C/2014 Q2 Lovejoy on 03/16/2015. A faint tail can be seen extending to the upper right.
The resulting image was then post-processed using the Astronomy Tools v1.6 actions in Photoshop.
Comet C/2014 Q2 Lovejoy continues to be a fascinating object to photograph in the evening sky. It is now located high in the sky at sunset and sets in the northwest overnight. It is, however, growing fainter and this requires longer exposure times to bring out the details. As noted in a previous post, I have been photographing the comet without an equatorial mount and this has limited my exposures to a few seconds. That has changed as I now have a tracker mounted on my tripod (iOptron SkyTracker) and this allows much longer exposures. It takes a bit of practice to properly align the device but I’ve gotten pretty good with a few sessions. With good alignment, it is possible to take exposures of 5–10 minutes without getting star trails.
Comet Lovejoy: 17 February 2015
On another night, I was again taking a sequence of images when some high, thin clouds moved in. Rather than shutting down, I continued to capture images. The result of the high clouds was to create a colored area around the brighter stars.
Comet Lovejoy: 18 February 2015.
Cloudy skies have returned to northern Arizona and that will be the end of comet photography for at least a few days.
Comet Lovejoy (known formally as C/2014 Q2) continues to put on an impressive show for sky watchers. In December it began to climb upwards from the southern horizon towards Orion, then passing to its west and climbing higher. In mid-January it was nearly overhead in the evening sky as it passed near Taurus and Pleiades. Many astrophotographers have taken advantage of this setting and there have been some beautiful photographs posted at various web sites.
To best capture the delicate details of the comet—and especially its tail—a tracking device is needed to guide your camera or telescope so that it matches the motion of the stars across the sky. This allows longer exposures without the stars streaking or creating star trails. Without a tracking device, exposure time is limited. This limitation can be partially overcome by taking numerous short exposure images and stacking them using any of the many applications available. Still, the laws of physics and the engineering of camera sensors will result in better images if you have, say, five 30-second exposures than thirty 5-second exposures—even though both are 150 seconds total exposure.
From the DeepSkyStacker pages on the theory of stacking:
Are 100 x 1 minute and 10×10 minutes giving the same result? Yes when considering the SNR but definitely No when considering the final result. The difference between a 10-minutes exposure and a 1-minute exposure is that the SNR in the 10-minutes exposure is 3.16 higher than in 1-minute exposure.
Thus you will get the same SNR if you combine 10 light frames of 10 minutes or 100 light frames of 1 minute. However you will probably not have the same signal (the interesting part). Simply put you will only get a signal if your exposure is long enough to catch some photons on most of the light frames so that the signal is not considered as noise.
For example for a very faint nebula you might get a few photons every 10 minutes. If you are using 10 minutes exposures, you will have captured photons on each of your light frames and when combined the signal will be strong. If you are using 1 minute exposures you will capture photons only for some of your light frames and when combined the photons will be considered as noise since they are not in most of the light frames.
Since I don’t have a tracker (at least, not yet), I have no choice but to stack short-exposure images of the comet. Here are a few images of Comet C/2014 Q2 Lovejoy taken on several different nights. The quality of the images varies depending on how much light pollution was captured in the image, whether there was moonlight, and how clear the sky was.
Comet C/2014 Q2 Lovejoy and Pleiades: 19 January 2015.Comet C/2014 Q2 Lovejoy: 08 January 2015Comet C/2014 Q2 Lovejoy: 27 December 2014
Comet C/2014 Q2 Lovejoy and Orion above Cathedral Rock, Sedona, Arizona: 28 December 2014
There’s still plenty of time this winter to venture outside with a pair of binoculars and gaze at the comet. Here is a link to a sky chart provided by Sky and Telescope for the month of January. For February and beyond, try this chart hosted by UniverseToday.
Comet C/2014 Q2 Lovejoy has been climbing northward and is now well above the horizon for easy viewing in the northern Hemisphere. Sky and Telescope magazine has a good article showing where the comet is located each night in the sky through January.
With inclement weather approaching and threatening to eliminate any chances of photographing comet C/2014 Q2 Lovejoy for the next week (or more), I took advantage of one last clear, chilly night. The comet was easily visible in 7×50 binoculars and faintly visible as a naked-eye object.
The first image shows the well-known Cathedral Rock in Sedona, Arizona, with the comet visible in the lower left. Shot with a wide-angle lens, the tail is barely distinguishable in this image. In the upper center of the image stands Orion. (ISO 1600, 28mm, f/2.8, 15 seconds.)
The second image clearly shows the tail extending up and to the left. (ISO 1600, 85mm, f/1.8, 8 seconds.)
The third image is a composite of 100 images each of 8 seconds duration and stacked with Deep Sky Stacker and shows a much longer and more detailed tail. (ISO 1600, 85mm, f/1.8 100×8 seconds.)
All images were taken using a fixed tripod with no tracking. I would like to try a equatorial tracking device so that I might be able to take longer exposures without the stars developing trails. Perhaps that will be my next photo equipment purchase.
