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250th anniversary of Halley recovery
Paolo
post Nov 2 2008, 12:47 PM
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No one seems to have noticed, but next December 25 marks the 250th anniversary of Palizsch's recovery of comet Halley, the first time a comet was predicted to return
http://cometography.com/pcomets/001p.html
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ElkGroveDan
post Nov 2 2008, 03:20 PM
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I'll feel really old when they recover it again...anyone know when that is likely to occur?


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dvandorn
post Nov 2 2008, 05:52 PM
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Isn't Halley supposed to return in 2061? It's period is some fraction greater than 75 years, right? And it last appeared in 1986, the time before that it was here in 1910, and the time before that in 1835. It's either slated for late '61 or early '62, from that reckoning. At which time I would be somewhere around 106 years old. YMMV.

Fairly easy to predict in rough terms, though, eh? wink.gif

-the other Doug


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ElkGroveDan
post Nov 2 2008, 06:02 PM
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True, but visual recovery of it will occur some time before that.


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dvandorn
post Nov 2 2008, 06:57 PM
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Yeah, very true. Well, last time Halley was spotted telescopically just more than a year before its perihelion. It had a rather poor geometry for Earth-based observation last time, but that was during perihelion. I really don't know how the far-approach geometry compares in 2061 to what it was in 1986.

BTW, as per wiki, next perihelion is July 28, 2061. No info readily available on the approach or viewing geometry, though.

-the other Doug


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Paolo
post Nov 2 2008, 07:03 PM
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By the way, Halley is still being tracked telescopically, last in 2003. According to Olivier Hainaut, who used the VLT to spot its nucleus, it probably won't be observed again until around aphelion in 2023
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siravan
post Nov 2 2008, 07:11 PM
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QUOTE (dvandorn @ Nov 2 2008, 01:57 PM) *
BTW, as per wiki, next perihelion is July 28, 2061. No info readily available on the approach or viewing geometry, though.


IIRC, 2061 return won't have a favorable geometry either. I have a vague recollection that 1986 and 2061 have the two worst viewing geometry (from Earth that is!) in the last 2000 years.
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mcaplinger
post Nov 2 2008, 08:59 PM
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QUOTE (dvandorn @ Nov 2 2008, 10:57 AM) *
Well, last time Halley was spotted telescopically just more than a year before its perihelion.

Huh? It was recovered on 16 Oct 1982 by Ed Danielson and Dave Jewitt using the Hale telescope at Palomar. Perihelion was 9 Feb 1986.


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dvandorn
post Nov 2 2008, 09:50 PM
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QUOTE (mcaplinger @ Nov 2 2008, 03:59 PM) *
Huh? It was recovered on 16 Oct 1982 by Ed Danielson and Dave Jewitt using the Hale telescope at Palomar. Perihelion was 9 Feb 1986.

Really? We need to go fix Wikipedia, then...

QUOTE
The first person to visually observe comet Halley on its 1986 return was amateur astronomer Stephen James O'Meara on January 24, 1985. O'Meara used a home-built 24" telescope on top of Mauna Kea to detect the magnitude 19.6 comet.


This was footnoted:

QUOTE
Malcolm W. Browne (August 20, 1985). "Telescope Builders See Halley's Comet From Vermont Hilltop". The New York Times. Retrieved on 2008-01-10. (Horizons shows the nucleus @ APmag +20.5; the coma up to APmag +14.3)


-the other Doug


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ugordan
post Nov 2 2008, 09:51 PM
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QUOTE (dvandorn @ Nov 2 2008, 10:50 PM) *
We need to go fix Wikipedia, then...

I'm not saying either one of you is wrong, but Wikipedia shouldn't be taken for gospel...


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dvandorn
post Nov 2 2008, 09:55 PM
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I have a feeling that the Wikipedia reference is for the first eyeball-to-eyepiece *visual* (not photographic) recovery of Halley prior to its 1986 perihelion, and that Mike is referring to the first *photographic* recovery of the comet.

-the other Doug


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ugordan
post Nov 2 2008, 10:32 PM
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Hmm, you might have a point there. Either way, photographic evidence is photographic evidence wink.gif


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mcaplinger
post Nov 2 2008, 11:10 PM
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QUOTE (dvandorn @ Nov 2 2008, 01:55 PM) *
Mike is referring to the first *photographic* recovery of the comet.

Technically, Ed Danielson was using the PFUEI (Prime Focus Universal Extragalactic Instrument), which was a cooled CCD camera based on the TI 800x800 sensor used in the first WF/PC on HST.

Ed went on to be the instrument manager on the Mars Observer Camera.


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dvandorn
post Nov 2 2008, 11:17 PM
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You know, that bring up a good semantic nit -- is it only "photographic" if it involves film? Is there another term if the light is recorded via CCDs and not film? Electronic light capture vs. photographic light capture vs. biologic (i.e., eyeball) light capture? I guess in that case, "visual" contact would only apply to the third of those options.

I find it interesting that by 2061 it's possible that Halley might not again be lost -- that we may have instruments sensitive enough to maintain electronic (if not "visual") contact all the way out to its next aphelion and back.

-the other Doug


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