Starship Asterisk*

http://www.ll.mit.edu/mission/space/linear/ wrote:
<<LIncoln Near-Earth Asteroid Research (LINEAR) is an MIT Lincoln Laboratory program funded by the United States Air Force and NASA. The goal of LINEAR is to demonstrate the application of technology originally developed for the surveillance of Earth orbiting satellites, to the problem of detecting and cataloging near-Earth asteroids—also referred to as near-Earth objects (NEOs)—that threaten the Earth.

The project uses a pair of Ground-based Electro-Optical Deep Space Surveillance (GEODSS) telescopes at Lincoln Laboratory's Experimental Test Site (ETS) at the White Sands Missile Range in Socorro, New Mexico. The telescopes are equipped with Laboratory-developed charge-coupled device (CCD) electro-optical detectors and collected data is processed onsite to generate observations. Observations are then sent to the main Lincoln Laboratory facility at Hanscom AFB in Lexington, Massachusetts, where they are linked from night to night, checked, and sent to the Minor Planet Center (MPC). The MPC assigns designations to LINEAR's new discoveries of NEOs, comets, unusual objects, and main belt asteroids.>>

LINEAR Observations, Detections, and New Discoveries
Totals as of December 31, 2007

Observations to MPC 	22,349,515
Asteroid Detections 	5,370,805
Asteroid Discoveries 	225,957
NEO Discoveries 	2019
Comet Discoveries 	236

http://www.nightskyhunter.com/Comet%20Hunting%20-%20A%20Closer%20Look%20-%20Avoiding%20The%20Surveys.html wrote:
<<In the early days of comet hunting amateurs were free to search as much of the sky they wanted with no clear competition from the professionals, they were visual searchers who were limited only by their determination and the field was wide open to them. Times have changed since those days and now amateurs face a real threat from a host of prolific professional search systems that have emerged onto the scene since the late 1990’s…and for good reason! These surveys have been employed to scan the skies for earth threatening asteroids and comets that could some day pose a serious threat to civilization. Their goal is to find 90% of the potentially hazardous objects out there with a diameter of over 1km. As a consequence the number of amateur comet discoveries has declined since that time. A large number of these robotic patrollers of the sky are now in operation with names like LINEAR (Lincolin Institute Of Near Earth Asteroid Research), NEAT (Near Earth Asteroid Tracking), LONEOS (Lowell Observatory Near Earth Object Search), SPACEWATCH, CSS (Catalina Sky Survey), SWAN (Solar Wind Anisotropies) and SOHO (Solar And Heliospheric Observatory). Using examples of the research completed by Shigeki Murakami I hope to show that amateurs can still compete and continue making discoveries despite the threat from these automated surveys.
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The Threat From LINEAR

The sky visible from the northern hemisphere has been exhaustively searched by LINEAR. Australia may be the last sanctuary left for visual comet searchers….is this correct?

Mr Shigki considers the problem….The area of sky outside LINEAR’s coverage is fairly large. In spite of this, there have been hardly any visual discoveries from the northern hemisphere. This may be because comets usually enter LINEAR’s search area at least once before they attain a brightness possible for visual discovery. This will enable LINEAR to find comets. Although it is not impossible to discover comets visually from the northern hemisphere, the probability of visual discoveries must be now diminished to a fraction of what it used to be.

Comet Discoveries By LINEAR And Amateurs


Consider the relation between the number of discoveries by LINEAR and solar elongations over a period between the beginning of the search by LINEAR and the end of 2002. The total number of discoveries is 99. Most comets were discovered at a solar elongation of more than 80 degrees. Those discovered at a solar elongation of less than 80 degrees count two in the morning and one in the evening. Among those were two discovered at a solar elongation of 75 degrees and 70 degrees. It indicates that the areas of sky within a solar elongation of 80 degrees are most likely outside LINEAR’s search coverage.

After LINEAR started to operate at full capacity, four comets were visually discovered at solar elongations of more than 80 degrees; three in the morning and one in the evening. Of those four, three were discovered in the southern sky; C/1998 P1 Williams (Australian), C/1999 H1 Lee (Australian), and C/2000 W1 Utsunomyia – Jones (Japanese and New Zealander). We tend to think the southern sky is beyond the reach of the Japanese observers, but, as explained later, south of - 30 degrees in declination are outside LINEAR’s coverage.

Note that most of the discoveries by amateurs were made at solar elongations of less than 80 degrees, outside the coverage by LINEAR. This has been even before LINEAR commenced its operation. As regards the search areas, visual search by amateurs and LINEAR’s coverage do not overlap and there is not much competition between them.

Incidentally, both discoveries by LINEAR and by amateurs show that there were twice more discoveries in the morning than in the evening. I have read such claims in a book that there are more transparent, less light polluted, and observers have better physical conditions after a night long sleep. However, this argument is conventional and unconvincing. LINEAR’s telescopes are installed at locations where meteorological conditions are excellent and very little light pollution exists. And, as they are telescopes, it is irrelevant if the observer has had a good sleep or not. It will be more logical to argue that more new comets appear in the pre dawn skies than in the evening. This author has no knowledge of convincing theories presented to explain this fact. A conventional thinking goes as follows: An observable part of the evening sky (or constellations) in the west at any particular time is continuously observable for several months prior to that time without any interference from the glow of the sun. On the other hand, an observable part of the predawn eastern sky at any particular time of year is not observable for about two months prior to that time hidden in the glow of the sun. Therefore, at pre dawn the part of the sky hitherto hidden continuously emerges out of the glow of the sun resulting in more discoveries. However, there is no way to know if this theory is correct.

I have once heard that LINEAR has difficulty in detecting diffuse objects and that diffuse comets not detected by LINEAR had been discovered by amateur observers. When a stellar object and a comet of the same magnitude are compared, the stellar object with its light concentrated at a point is easier to detect than a comet with extended, diffuse light. This is the same photographically and visually. But the seemingly convincing argument that LINEAR cannot detect comets with extended light is simply nonsense.

About the issue of whether visual discoveries are possible under the gaze of LINEAR Mr. Tsutomu Seki, the head of OAA Comet section, has attempted an analysis based on the presumption that, of the six comets Mr. Seki has discovered, those at solar elongations of more than 90 degrees with magnitude 18 or brighter would be detectable by LINEAR. He concluded that LINEAR could have detected one comet without any doubt, one without certainty, and could not have discovered the other four. He has also analyzed C/1999 A1 Tilbrook (discovered on January 12 1999 UT) and C/1999 N2 Lynn (discovered on July 13 1999 UT).

He points out that LINEAR was not able to discover C/1999 A1, in spite of the fact that on December 5, 1998 it was located at +78 degrees in declination with the magnitude being 12 and a solar elongation of 101 degrees. This implies that northern hemisphere comet hunters had a good chance of discovering this comet. He continues that LINEAR could not find C/1999 N2, which was located at - 36 degrees in declination in October 1998 at a solar elongation of 120 degrees with magnitude 16, though the solar elongation diminished after that. As I referred to earlier, LINEAR was probably unable to discover it because it could not cover the area south of - 30 degrees in declination.

Mr. Seki has also analyzed C/2000 W1 Utsunomiya - Jones (discovered on November 19 UT) and P/2001 Q2 Petriew (discovered on August 18 UT). He states that LINEAR could not discover C/2000 W1, although the comet was located at - 9 degrees in declination with a solar elongation of 89 degrees at magnitude 11. P/2001 Q2 had maintained small solar elongations up to the discovery and been outside LINEAR's search area.

Mr. Seki's analysis show that including the comets prior to the start of search by LINEAR there were many comets which were not discoverable by LINEAR and those which were discoverable but not discovered.

I also heard that finding comets would be difficult in the Milky Way. Some people asked me if I had deliberately searched the Milky Way to find C/2002 E2 Snyder-Murakami thinking that LINEAR could not perform well in the Milky Way. It was not in my mind at all at the time of the discovery. However, I have a tendency to search the Milky Way, if I have a choice, because I can enjoy that part of the sky strewn with so many stars.

Regarding the remark that comet discoveries are difficult in the Milky Way, I asked Mr. Akimasa Nakamura, as I did not have much information on it. Mr. Nakamura replied:

"LINEAR's algorithim for detecting objects in motion is different from that of other surveys. Normally, detection of objects in motion is made from a number of frames. In the case of LINEAR five frames of the same field are stacked up and 'five stars in a straight line' are picked up as an object in motion. Because of this, new objects are not often missed, even if they overlap with stars. It can also search the summer Milky Way without any problem, while other surveys tend to avoid this part of the sky."
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Comet hunters can survive for the time being, though the discovery rate reduced to one third in the northern hemisphere after NEO sky survey. In the southern hemisphere if the search becomes active higher discovery rate is expected than the statistics to date. When Kaoru Ikeya discovered his 6th comet 153P Ikeya-Zhang, 35 years had past since his last discovery (Sky & Telescope, July 2002, p.70-73). Shigehisa Fujikawa has spent 24 years to find his 5th comet that named him, C/2002 X5 Kudo-Fujikawa. Both of them continued comet hunting for decades of years without hesitation. Tsutomu Seki emphasizes importance of self confidence and dedication; "Strong rivals exist in any area and only comet hunters who fight bravely and attack openly are crowned with victory".

Unless complete sky coverage of the NEO sky surveys is realized, amateur comet hunters can survive but they have to swim with the sharks. Comet hunting goes on.

In his latest book David Levy (discoverer of 21 comets) summaries...

'Comet hunting has utterly changed in the 37 years since I started comet hunting in 1965. Back then, the threat to visual searches was from photographic surveys, which were succeeding in finding most of the comets. However, these efforts were concentrating on the sky at opposition to the Sun, and not terribly thoroughly at that, leaving many comets available for visual observers. Even after the enormous productivity of the great Palomar photographic surveys of the 1980s and 1990s - surveys specifically designed to discover comets and asteroids - until a few years ago it still seemed possible for comets to be found visually'.

'Although it is certainly still possible to discover a comet visually, it is far more difficult to do so than it was even a few years ago. Some comets happen to come in at a shallow angle to the Sun that hides them from the big surveys. But the date and time of the last visual comet discovery is approaching. I still believe that there will always be comets for the amateur to seek and find through his or her visual telescope. It's harder than it used to be, and many searchers will give up. In 1967, Robert Burnham Jr. who discovered comets both visually and photographically, advised me that "If you hunt long enough, stay away from the galaxies in Virgo, and never give up, some day you will find a comet." I think this advice still holds, although that "some day" could be decades into the future for most searchers'.

'As you hunt for comets, remember that it isn't a good idea to have the discovery of a new comet your only goal. In 1997, Leif Robinson, then-editor of Sky and Telescope, came down pretty hard on single-minded searchers. "I've never had any great admiration for comet hunters," he editorialized. "To spend hundreds of hours in failure for each minute of success never seemed like a good deal to me. ... For amateurs there's the allure of getting your name hitched to a star, albeit a hairy one. If you're very lucky, like Thomas Bopp, your name might appear in text books for years." If the only reason you spend all this time comet hunting is to find a comet, then Robinson has a point. So did the great Japanese comet hunter Minoru Honda, who discovered 12 comets and 11 novae during his lifetime, in the advice he gave Kaoru Ikeya before the young comet hunter made his first discovery. "If you desperately want to find a new comet, please stop your search because you may never be able to find a new comet. However, if you are content to search the sky without ever experiencing a new comet discovery, please keep searching because someday, you may be able to find a new one." Leslie Peltier, in Starlight Nights, perhaps said it best: “In spite of this increasing competition there always will be comets for the amateur to seek and, in some facets of this work, he still has an advantage. In a given time he can cover far more sky than can the camera, he can know within half an hour the true nature of a suspected object and he can search much closer to the sun in regions which would fog a photographic plate.”>>

Ian Cooper wrote:In the APOD for October 2nd 2009 there is a statement in the first line that says, "The Orion Nebula is a familiar northern hemisphere astronomical sight." The last time that I looked M 42 was at declination 5 degrees 23 minutes south. Also by being at Right Ascension 5 hours 35 minutes M 42 will hardly move much closer to the celestial equator over the coming centuries, and therefore will always remain a southern hemisphere object. To be considered a northern object it would need to be visible from the north pole. Unless the inclination of the poles changes dramatically then the latter event will never happen.

It is great that you northern folk can see some of our southern treasures, but don't try taking ownership of them, we guard them jealously. I can see the Andromeda Galaxy culminating at 9 degrees from here in New Zealand but we would never lay claim to it being a familiar southern hemisphere sight even though we look forward to seeing each spring.

orin stepanek wrote:I never paid any attention as to whether the Orion Nebula was South or North hemisphere. For me the Orion Constellation is one of the most Identifiable objects in Nebraska skies. 8)

bystander wrote: Last time I checked, New Mexico was still in the Northern Hemisphere.

orin stepanek wrote: I didn't say it wasn't. So is all of old Mexico!

bystander wrote:

orin stepanek wrote: I didn't say it wasn't. So is all of old Mexico!

I agree with you. I was supporting your statement, not detracting from it.