Submitted: Wednesday, 28th March 2007 by Mike Salway
2007 has already been a big year for comets, with Comet McNaught (C/2006 P1) putting on a spectacular display in January. Well it’s not over yet! Long-time IceInSpace member Terry Lovejoy (CometGuy) has just discovered a new comet, C/2007 E2 (Lovejoy), his first such discovery - and the first ever comet discovery using an off-the-shelf digital camera!
Mike talks to Terry about his discovery, his methods and how it feels to finally find what he’s been searching for.
IIS: Let’s start with a bit about yourself. How old are you, where are you from and when did your interest in Astronomy begin?
TL: I live in Thornlands, a bay side suburb of Brisbane. I am 40 years old and have been interested since a young age. I remember being shown Mars and Jupiter through a Unitron refractor in the mid-70’s by my father and have been hooked ever since. I actively started identifying constellations in the later part of 1977 and remember eagerly awaiting Orion to rise. By early 1978 I had sold a trail bike to fund an 8” Newtonian and never really lost interest since! Another event that is etched in my memory is being taken to a public field night held by the Sutherland Astronomical Society in the Suburbs of Sydney where I grew up.
IIS: Have you always been interested in Comets? What is it about them that fascinates you?
TL: My grandmother remember seeing a spectacular Halley’s Comet in 1910 from near Mossvale, NSW, when a local astronomer got her family up in the morning to view the comet (I’ve always wondered whether that astronomer was John Tebbutt). Her accounts were very inspiring! Dad also clearly remembers the Spectacular Comet Ikeya-Seki in 1965. I think the final catalyst was hearing about a recent comet discovery of magnitude 5 with a clear tail in 1978 by David Seargent. I really wanted to see one and that finally came at the end of 1980 with the observation of Comet Stephen-Oterma and Tuttle which were around mag 8 or so at the time.
I guess the attraction is that comets show a great variety of detail and phenomena. There is also a thrill of seeing a bright comet develop from a faint diffuse blur into a intensely brilliant object with a searchlight beam tail.
IIS: How long have you been searching for Comets? Can you describe the methods you use, for capture, processing and analysis?
TL: I really didn’t start seriously until mid-2004 (actually my first search sequence was on May 16, 2004) as I was really waiting for technology to catch up and provide a large format imager at an affordable price. That time came with the introduction of the Canon 300D.
In the 1980’s I created a set of search charts for Kreutz Sungrazing comets and made a couple of attempts to search visually with binoculars and a telescope but not with anywhere near the commitment needed to be serious. I don’t really count those times!
Around 1999 SOHO started to publish images from their LASCO C3 camera. In August, 1999, I discovered a couple of faint Kreutz sungrazing comets in the LASCO C3 real time images. But these were not credited with my name as they were discovered via a professional instrument. In the following 2 years I discover 10 comets this way. None of them were seen from the ground.
The serious search began mid-2004 as mentioned. I basically take 10-16 images of a single field and stack them to make 2 images that can blinked to show moving objects (as well is exclude cosmic ray strikes and the like). My telescope drive is programmed to advance along Right Accession and take images of around 8-10 fields per session (with both cameras operating). Image processing is done using IRIS, which has been fully automated using Autoit as well as its own scripting facility. IRIS also does astrometry so that I can easily calculate RA and DEC of a suspect and I now generate star charts automatically centred on the suspects. The process has evolved to the point it is quite efficient and I would spend about 5 minutes searching a field. There is probably about an hour involved in setting up, retrieving cameras copying/sorting images to the computer hard drive. The processing (which is automated) takes at least an hour for 5 fields and the searching around 30 minutes.
IIS: That must be painstakingly slow and labour intensive work. How many hours have you spent in the last few years searching for Comets?
TL: I have not taken accurate notes, but probably 1000 hours.
IIS: Did you ever feel like giving up? With the proliferation of automated, robotic sky surveys such as the Siding Springs Survey, the LINEAR, NEAT and SWAN programmes all looking for NEO’s, it must be almost impossible to find a new object using your methods?
TL: Yes! But when I found prediscovery images of 2 comets, including a quite clear image of C/2006M4 before it was announced I knew I was on the right track and that it would be only a matter of time. Most of the big surveys don’t search too close to the sun where most comets are brightest. Furthermore, coverage is not always complete by the big surveys; they can’t look everywhere at once (at least not yet). The other competition is SWAN and soon STEREO. SWAN can often easily detect comets down to mag 10, but they don’t always make data available in a timely fashion as was the case with 2007 E2. My current camera lens configuration can also see fainter objects than SWAN (I have detected comets of mag 14 in my images).
IIS: Comet Lovejoy (C/2007 E2) was discovered on the morning of March 15th, 2007. Tell us about that morning. Was it different to any other search you’d done?
TL: Not really. I was feeling pretty fatigued recently and had not done many searches in the morning as a result. However, my job often requires oncall and this morning I got a few calls so my sleep was already interrupted so I decided to setup and try my luck.
IIS: What’s the process for lodging a potential discovery? What did you do the moment you discovered something on your images?
TL: Generally it’s preferred to get a backup observation by another observer before lodging a claim with the CBAT (Central Bureau of Astronomical Telegrams). In this case I jumped the gun a little, and in the late afternoon lodged a precautionary note to Dan Green at the Bureau to say I might have something and plan to get further confirmation. Further confirmation came only a few hours later from John Drummond who called me later that evening. Once I got a followup position the following morning CBAT issued circular IAUC 8819 announcing the discovery.
IIS: It must have been an agonising wait to get confirmation that it wasn’t an already discovered and named object. Was it hard not to get your hopes up?
TL: It certainly was! But by Sunday I had obtained 3 nights of observations myself and this was indicating a high inclination orbit with no matches to previous comets so I felt certain I was going to be credited.
IIS: Paint us a picture of Comet Lovejoy (C/2007 E2). What is its orbit? Has it gone around the Sun yet, and how bright is it expected to get? Is it a periodic comet or will this be the first and last time we see it?
TL: C/2007 E2 is closest to the sun late in March, although it always strays further from the sun that earth. It does however approach to earth in April and may brighten to mag 7 and be well located in the morning sky under the milky way. Because it is intrinsically rather faint tail development is expected to be minimal. Regarding the periodicity of the comet, we will have to wait for more astrometric observations so that an accurate orbit can be determined. This might take a month or so.
IIS: With Comet McNaught (C/2006 P1) putting on such a spectacular show in January, there seems to be renewed interest in Astronomy from the media and general public. What has the reaction been to your discovery? I imagine you’ve been inundated with requests for information, interviews etc.?
TL: The attention is actually slightly more than I am comfortable with and more than I thought would occur for a 9th magnitude comet! Some people have locked onto the fact that it was the first discovery by a consumer digital camera.
IIS: Is it hard to be the one to follow after Comet McNaught? A lot of people might be hoping or expecting Comet Lovejoy to become just as bright as C/2006 P1.
TL: No not really, I am content with a comet visible in binoculars! The reality is a great comet like P1 is intrinsically bright and will almost certainly be found by the professional surveys when in it is far from the sun.
IIS: This discovery must have been a lifelong goal for you, now achieved! What’s next? Has it invigorated you to keep searching, or with that goal now out of the way, will you relax and let the robots do the searching from now on?
TL: A tremendous amount of work went into the search, I don’t plan to rest on my laurels just yet!
IIS: Is light pollution killing the ability for you to do this type of comet searching? Do you ever get the chance to go out to dark sites?
TL: Yes light pollution has a serious impact. My evening sky suffers greatly and I have been forced to go to the 200mm lens, although in the morning sky it is still often dark enough to see the zodiacal light and my limiting magnitude is better as a result.
IIS: Which other comet hunters do you admire? What has been your favourite comet to-date?
TL: Don Machholz and Vello Tabur have given me tremendous encouragement. Of course how could you not admire Bill Bradfield!
As for comets I have trouble picking favourites between Comet Hyakutake and Comet McNaught as they were very different but spectacular comets (the later for me might get a small edge). Comet Hale-Bopp was amazing in binoculars and I saw it at its best from some of the most scenic locations in the USA.
IIS: What do you enjoy doing when you’re not standing in the dark behind a camera?
TL: Spending time with my family.
IIS: Thankyou very much for taking the time to talk to IceInSpace.
TL: Thanks Mike.
References and Further Reading