comet – Page 5 – A Darker View

Postcard from the Universe – C/2013 R1 Lovejoy

I had set the alarm clock for 0230 to get up with plenty of time to setup and take comet photos. What greeted me was a sheet of cloud, an all to familiar sight lately. I did not reset the alarm and went back to sleep. A couple hours later I found myself lying awake again, realizing I would probably not fall back to sleep I got up to look outside. To my surprise Orion shown brightly over the street.

Is there enough time to setup and shoot before dawn?

I rushed the alignment, hoping to setup in less than half an hour. Things did not go smoothly… The EOS utility in the computer did not recognize the 6D, I need to update the drivers. A thin cloud stubbornly sat in front of Polaris, I think I got the polar alignment, the star was very dim on the polar ‘scope. Even when exposures seemed to be going smoothly I they were not. I find out later the auto-guider had moved itself to a hot pixel, probably when a bit of cloud passed through. In the rush I did not get a dark frame for the guider, most of the frames show small guide errors.

One not so bad bit of serendipity… The Hubble Space Telescope went right through one of the frames.

Despite all I did get an image of the comet. It should have been better, rushing astrophotography is not a good plan…

Comet C/2013 R1 Lovejoy on Nov 15, 2013. Canon 6D with the AT6RC and a 0.8x focal reducer. 12 x 60s at ISO 6400.

Dispatch from the Summit – A Cloudy Mountian

Comet ISON is sinking rapidly into the dawn. I have been waiting for a chance to photograph it for a couple weeks now. The gear is ready to go. Any morning that I have had available has been awash with clouds. Not strictly my problem, Keck has lost quite a few nights to weather over the same time period.

Tonight looks to be no exception. We have a number of engineering tests planned for Keck 1, including the first night on sky for a system many of us have put a lot of work into, the TRICK infrared tip-tilt detector for Keck 1 AO. It does not look good.

Update: The night was a complete loss, the telescope never opened.

A Cloudy Mountain — Clouds obscure Mauna Kea on a late fall morning

Comet? Where?

There is one question we all have to ask when a beautiful comet graces the skies…

Comet C/2007 N3 Lulin on the evening of 26 Feb 2009

Where to look?

Like any other solar system object, comets move against the sky. Even worse, when close to the Earth or Sun they can be moving so quickly against the stars that coordinates quickly become out of date. Aiming a telescope using coordinates a day old, or sometimes even only an hour old will result in a view of empty sky. A few stars perhaps, but no comet.

You need a table of coordinated calculated for regular time intervals, an ephemeris. Alternately you need a set of coordinates calculated for the exact time you will be looking.

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Preparing for Comet C/2012 S1 ISON

Astronomers, professional and amateur alike, are getting ready for comet C/2012 S1 ISON, possibly the highlight of a year that has already seen several good comets.

Discovered in September 2012 by Vitali Nevski and Artyom Novichonok, of the ISON project, a group of telescopes dedicated to discovering and tracking solar system objects. The comet was then an 18th magnitude object in the outer solar system, an impressive find for a small telescope.

When astronomers first calculated the comet’s orbit they found a surprise. The comet will pass close to the Sun. Not just close, but extremely close! On November 28th the comet will pass perihelion, its closest approach to the Sun. At a mere 1,860,000km (1,150,000miles) this will be a close pass indeed. As perihelion is measured from center to center, the distance is even closer if you consider the 695,500km (432,200mile) radius of the Sun. Subtracting the solar radius you realize the comet will pass a mere 1,165,000km (724,000miles) above the surface of the Sun. At this distance the intensity of the solar radiation will be nineteen thousand times more intense than a sunny day on Earth.

The next surprise was hinted at by the orbital calculations. The orbital solution indicated a nearly hyperbolic path, suggesting that this was a new comet, one that had not visited the inner solar system before. This possibility was strengthened by later observations of the comet.

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Taking Comet Photos with Keck

After our comet ISON observing session I have been asked what it is like to take a comet photograph with Keck. An apt question as all of the recent observers were taking spectra, not photos.

The answer? Not very pretty.

A few years back Greg Wirth and I took some frames of comet Hartley 2 with Keck 2. When I processed the frames into a color photo the results were less than impressive.

Comets are big. While the nucleus is quite small, we do not see the nucleus even with the enormous power of a 10 meter telescope. It is hidden in the coma and quite dark, the average nucleus is a shade of dark gray equivalent to charcoal.

The coma and tail are very extended, much larger than the field of view of the telescope, thus the entire frame is inside the coma. The photo of Hartley 2 Greg and I took was no exception.. The image is notable for its complete lack of any interesting structure. There are no jets, shells or other inner coma detail visible. The tail is simply a general brightening to the southwest (lower right in this image).

Small telescopes, in the hands of amateurs, are going to produce the prettiest images of comets. With fields of view measured in degrees, not arcminutes, the comet is going to be seen in all its glory.

103P/Hartley 2 — Comet 103P Hartley 2 with Keck2 and DEIMOS 6Oct2010 @ 7:27UT, 3x60s, 3x60s and 3x120s with standard BVR astrometric filters, credit: Cooper/Wirth/W.M. Keck Observatory

Postcard from the Universe – 144P Kushida

Continuing with the cometary theme, another favorite comet photograph from the past…

ISON Webcast

We put it together in very short notice. Fortunately a webcast is pretty easy to put together.

Keck is hosting a sizable team of folks who are here to observe comet ISON. Astronomers from several institutions are participating in the NASA Comet ISON Observing Campaign. They have a total of 6½ nights, but only the last few hours of each night as the comet rises in the dawn. Comet C/2012 S1 ISON is starting to encounter significant publicity, we may as well take advantage of this.

It was a lot of fun. I particularly like the spot (41:00) where I made the mistake of saying spectra were not very pretty to look at in a room full of spectroscopists. These folks love spectra and quickly corrected me, leading to a nice discussion on why spectra are so valuable to astronomy, often more valuable than photos.

The video is embedded below. A lot of good information about comet ISON, indeed about comets in general. Nothing like having a room full of comet experts…

Waiting for ISON

I will probably make my first attempt to photograph C/2012 S1 ISON this coming weekend. A couple reasons for waiting… The bright Moon will have moved out of the morning sky by then. The comet, currently around magnitude ten, is brightening rapidly.

On the other hand the comet is plunging towards the Sun, rising later each day. Wait much longer and the photographic opportunity will slip away, at least until after Thanksgiving, when the comet will again appear after perihelion.

In the meantime, one of my favorite comet photos from years past…

Keck Lecture – Comet ISON

Astronomy Talk: The Wonder of Comet ISON, A Relic From the Beginning of the Solar System

Thursday October 24, 2013
07:00 pm – 08:00 pm

Kahilu Theatre

Dr. Carey Lisse, head of NASA’s Comet ISON Observation Campaign, will present a timely talk on how and when comets were formed, and where they come from. Also a Senior Research Scientist with Johns Hopkins University Applied Physics Laboratory, Lisse will relate how comets may have helped start life on the Earth, and also how they may have ended it for millions of creatures at least 4 times in the past. He’ll also give a bit of the history of comet observing by mankind, and explain how Comet 2012 S1 (ISON) fits into this picture of comets as relics from the beginning of our solar system.

The Portents of ISON

Comets have long been regarded as omens of extraordinary portent. Novae, eclipses, conjunctions, anything seen in the sky can serve in this role, but bright comets have always held a special awe.

Even today those who seek signs are quick to seize upon any unusual astronomical event. A few months ago it was meteors, events over Chelyabinsk grabbing the attention. With ISON entering the inner solar system the attention shifts.

Bright comets are invariably seen as omens by some. History is littered with stories of comets and prophesies. This has not changed, there are many recent examples… Hale-Bopp, Hyakutake, Elenin, each has been used to make all manner of wild predictions. Comet C/2012 S1 ISON certainly fits the role. It will most likely be quite bright, easily visible without optical aid. It may even be visible in the daytime.

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