HDTenEightyP/NetNews huggingface dataset:
From: ethanb@ptolemy.astro.washington.edu (Ethan Bradford)
Newsgroups: sci.astro
Subject: Re: Gravitational lenses
Date: 20 Nov 92 06:17:29 GMT
Organization: U. of Washington
To: millnerrl@vtcc1.cc.vt.edu (CALLABLE_TPU)

I am not an expert in lensing (I was waiting for one to chime in), but
these few things I know:

With a gravitational lense there are always an odd number of images,
but, since some are magnified and some are demagnified, some images
may not show up.  The number of images depends on the mass
distribution of the lensing system (this is the most important unknown
in the lensing studies), on the geometry of the lensing setup, and on
the strength of the potential.  In the limit of a source exactly
behind a spherical lense you get an Einstein ring (I think this counts
as one image, very smeared out).  I think the distortion of the lensed
image always leads (for a spherical lensing mass) to extension into
arcs centered on the lensing mass, so I don't think a cross is
possible.

If you know the lensing mass distribution, you will be able to figure
out the angle that the light is bent through, so you will know the
exact geometry of the observer, the lense, and the source to an
overall factor.  That is, you will know the family of similar
triangles that the lines can be on, but you don't know the length of
any side.

This in itself is usefull; you will know, for instance, the exact
ratio of the distances of the lensing system and the quasar, and thus
you can check that the Hubble relation holds and confirm that quasars
are in fact at cosmological distances.  If you can in addition measure
the difference in length of two sides (by measuring the difference in
travel time of a speed-of-light signal), you can assign absolute
lengths to all the sides, which is a very important accomplishment.

Though a time difference has been measured for at least one lensed
system, uncertainties in the lensing mass distribution cause the
resulting answer for the Hubble constant to be no more accurate than
the value derived from other methods (according to the cosmologists I
know; the astronomers doing this work think their answer is very
precise), but this area shows great promise.

-- Ethan
From: newberry@kepler.as.arizona.edu (Mike Newberry)
Newsgroups: sci.astro
Subject: Re: st6 images wanted
Date: 19 Nov 92 21:45:24 GMT
Organization: University of Arizona, Tucson, AZ

In article <1992Nov19.193343.22313@novell.com> jscherer@db (John Scherer) writes:
>
> recently downloaded st6 images from sunlight.physics.uiowa.edu, but found that
> the images are 8-bit.  From what I know about the st-6, it is capable of 16-bit images.  I would like to see some 16-bit images if there available..
>
> John Scherer
> jscherer@sjf.novell.com

You should fetch the *.fts.Z files instead of the *.gif files.  You'll have
to use the unix uncompress to turn the .Z file into a binary uncompressed
data file. This file will be in "FITS" format, a standard used throughout the
astronomical world. If you do not have software which will read FITS format,
you can use the following recipe:

Skip the first 2880 bytes of the file, as this contains the file information
"header" in FITS format. Starting at byte offset 2880 will be found binary,
uncompressed, unpadded pixel data. The pixels are unsigned 16-bit integers,
so watch out if unsigned integers might choke your software--these images do
have values above 32767. To turn this binary raster file into a 2-dimensional
image, note that there are 375 2-byte pixels in each row. There are 242 rows.

Mike Newberry
Organization: Georgia Tech Research Institute
Date: Sunday, 22 Nov 1992 15:27:41 EST
From: <LABBEY@GTRI01.GATECH.EDU>
Newsgroups: sci.astro
Subject: Re: Prism Diagonals vs. Mirror Diagonals
 <2800016@hpgrla.gr.hp.com>

Prisms are not really ideal for this purpose.  They are FAR more expensive.
A 1" prism of the same quality as a $25 first surface mirror would cost over
$200.  Remember, there are three surfaces to be figured, and about an inch
of glass which must be perfect. The cost of the glass alone would exceed the
cost of the first surface mirror.

To the best of my knowledge, there is no source of high quality prisms for
this purpose.
a

Leonard Abbey, F.R.A.S.
Georgia Tech Research Institute
Atlanta, Georgia, USA
labbey@gtri01.gatech.edu
Newsgroups: sci.astro
Subject: Re: Distance of horizon
From: harper@kauri.vuw.ac.nz (John Harper)
Date: Sun, 22 Nov 1992 23:21:30 GMT
Organization: Victoria University of Wellington

In article <csLkuB9w165w@west.darkside.com> max@west.darkside.com (Erik Max Francis) writes:
>fiddler@concertina.Eng.Sun.COM (steve hix) writes:
>
>> Anyone have handy a function for figuring the distance of the
>> horizon from a viewer based on the viewer's height from the
>> surface?
>
>I calculated it a while ago to be 
>
>    s = r arctan [(h^2 + 2 h r)/r^2]^(1/2).
Refraction makes a significant difference. Mount Ruapehu is 2797m = 9175ft
high and about 150 miles or 230 km away. It can occasionally be seen from 
various local hills. It makes a difference of around 300m or 1000ft (from 
memory not recent calculation) to calculate how much of the mountain can 
be seen with and without allowing for refraction.

John Harper Mathematics Dept. Victoria University Wellington New Zealand
From: meier@Software.Mitel.COM (Rolf Meier)
Newsgroups: sci.astro
Subject: Re: Lunar astronaut covers earth with thum
Date: 18 Nov 92 13:52:45 GMT
Organization: Mitel. Kanata (Ontario). Canada.

In article <1992Nov17.122236.26582@hemlock.cray.com> dadams@cray.com writes:

>a magnifying lense when the moon (or sun) is in this position.  (Did
>I get it right?)

No.
Newsgroups: sci.astro
From: ins894r@aurora.cc.monash.edu.au (Aaron Wigley [Wigs])
Subject: Re: Supernova (Was Re: P/Swift-Tuttle at last!)
Reply-To: wigs@yoyo.cc.monash.edy.au
Organization: Monash University
X-Newsreader: TIN [version 1.1 PL6]
Date: Thu, 19 Nov 1992 23:36:34 GMT

Tarl Neustaedter (tarl@sw.stratus.com) wrote:
: In article <1992Nov14.043817.3016@monu6.cc.monash.edu.au>, ins894r@aurora.cc.monash.edu.au (Aaron Wigley [Wigs]) writes:
: > Then, all of a sudden I saw a very brief flash off centre from 
: > one of the Clouds. 
: >[,,,]
: > Until the next day, when I read about it in the newspaper. I happened to
: > have witnessed Supernova 1987A :-) 
: 
: From the smiley, I assumed you were making a joke, but someone else seems
: to have taken it seriously. 

No, no Joke intended.

: So I'll comment:
: If you saw a brief flash, it wasn't SN1987A. The neutrino flash was several
: seconds long, and the visual portion would have taken hours for the
: shockwave to arrive at the surface of the star. (Stellar atmospheres are
: not transparent). Once the shockwave did arrive, the brightness increase
: would be gradual, as larger and larger portions of the surface visible to
: you showed the effects (it's a sphere, and the closest portion is light-
: hours closer to you than the edge). After the effects hit the surface, the
: brightness would not fall back - the gas is still hot and size is still
: increasing due to the explosion.

Okay. People have sent Email to me regarding this observation. This is
what I can remeber. I can dig out other information at home, and post later.

 o What I saw could be more accurately described as a prolonged flare
   (not a fraction of a second flash). The flare was brief, I did not 
   have time to get my friends to look at it, but it was not over
   instantly. I would say duration was two, two and a half seconds. 
 o At the time I would not consider my eyes to be fully adapted to the 
   dark, as I had previously been inside a lighted room about 10 
   minutes before. The observation was performed
   outside the Warrnambool Royal Life Saving Society clubhouse, in Victoria,
   Australia (I can get Latitude and longitude if it is needed).
 o The sky was clear, with only some twinkling in the stars. Considering this
   observation was in a small city (on the outskirts), light pollution
   may have dampened the flare.
 o The event happened in the region off-centre of the (from Memory, I may
   be wrong) Large Magellenic Cloud. The Time was about 2115 local time,
   (I cannot remember if Daylight saving time was in effect then - it would
   depend on the date I will look up), on a Thursday night. Local time
   is 10 hours ahead of UMT. 

If someone needs any further information, please don't hesitate to ask/etc.

:          Tarl Neustaedter	tarl@sw.stratus.com
:          Marlboro, Mass.	Stratus Computer
: Disclaimer: My employer is not responsible for my opinions.

The Wigs of Oz,
Aaron Wigley
From: palmer@cco.caltech.edu (David M. Palmer)
Newsgroups: sci.astro
Subject: Re: Kepler's Mom Not Burned...
Date: 17 Nov 1992 22:55:16 GMT
Organization: California Institute of Technology, Pasadena
NNTP-Posting-Host: alumni.caltech.edu

sichase@csa3.lbl.gov (SCOTT I CHASE) writes:
>There is always Keplers "Fourth Law," the one we don't talk about much
>today.  If I remember correctly, he claimed that the semimajor axes of the
>planetary orbits were in the ratios of the radii of all the inscribed regular 
>polyhedra.  This is not exactly numerology, but it's close enough to
>be considered pretty silly by modern standards.

Instead we use Titus-Bode's law which states that the semi-major axis
of planet n is 0.4+ 0.3 * 2^n Astronomical units, with small exceptions:
    Mercury is planet n=-infinity and Venus is planet n=0
    The asteroid belt is planet n=3
    Ignore Neptune.  Pluto is planet n=7  (which is evidence that
	Neptune is an escaped moon of Pluto :-))

If Kepler's fourth law were correct, then we would talk about it.  Titus-Bode's
law is just as close to numerology, and people talk about it.  
(I use it as a mnemonic.)

-- 
		David Palmer		 palmer@alumni.caltech.edu
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: P/Swift Tuttle Observation 11/20-21/92
Organization: Simon Fraser University
Date: Mon, 23 Nov 1992 18:36:09 GMT

In article <1992Nov23.162924.12039@linus.mitre.org> chaloux@mandolin.mitre.org
(Dave Chaloux) writes about his telescopic observation of P/Swift-Tuttle:
>Two faint stars were noticed directly in line and under the
>tail at 7:10 p.m. The coma itself was a noticebly blue color which has been
>mentioned by others. A stellar nucleas is obvious and was roughly centered in
>the coma.
>
>At this point, the clouds rolled back in. This comet is beginning to look like
>a real beauty. One question that came to mind as I looked at it could not be
>answered due to the short amount of time I could watch (5 min). The two stars
>that were directly in line with the tail may in fact have been stars or they
may
>have been larger hunks of material that blew off the comet. I guess now I'll
>never know. 

The tail is blown by the extremely small pressure of the solar wind. It can't
influence macroscopic objects, certainly not ones sufficiently large to be
visible as points from here. I agree with you; the comet is getting to be very
nice. I'll get out my own 8" SCT tonight.

Leigh
Newsgroups: sci.astro
From: batchelor@nssdca.gsfc.nasa.gov (Dave Batchelor, Space Phys. Data Facil. 301/286-2988)
Subject: Re: supernova
News-Software: VAX/VMS VNEWS 1.41    
Organization: NASA - Goddard Space Flight Center
Date: Fri, 20 Nov 1992 18:27:00 GMT

In article <1992Nov20.164104.19401@sfu.ca>, palmer@sfu.ca (Leigh Palmer) writes...
>In article <1eie5uINN87n@darkstar.UCSC.EDU> fxt@helios.ucsc.edu (oxide owner)
>writes:
>>
>>> From: palmer@cco.caltech.edu (David M. Palmer)
>>> The supernova went off Feb 23 1987, (by the time of the neutrino burst),
>>
>>lovely hubris. 1987a exploded some 170,000 years ago.
> 
>It appears that we have a believer in absolute space with us. :-)
> 
>Leigh

Or perhaps you are a believer that c = infinity? ;-)  The relativity of
simultaneity doesn't really mean that we should think of events on our light
cone as "happening now."  It is reasonable to adopt the frame of reference of
the earth, the galactic center, or even the rest frame such that the 2.7 deg K
black body radiation is isotropic, and to think of time differences between
events within that reference frame.

Lightly,
])ave
------------------------------------------------------------------------------
Dr. Dave Batchelor   Space Science Data Operations Office   Mail Code 632
NASA Goddard Space Flight Center  Greenbelt  MD  20771  USA
batchelor@nssdca.gsfc.nasa.gov
From: schlegel@cwis.unomaha.edu (Mark Schlegel)
Subject: Re: supernova in M31
Organization: University of Nebraska at Omaha
Date: Mon, 23 Nov 1992 23:45:41 GMT


That's NOVA, not SUPERNOVA!!,

Geez, you got me all excited when I read that subject line.
From: 1k1mgm@kuhub.cc.ukans.edu (Christopher Gunn)
Newsgroups: sci.astro
Subject: Re: Fujinon FMT-SX 7X50
Date: 21 Nov 92 10:54:55 CST
Organization: University of Kansas Academic Computing Services

In article <1992Nov21.054854.20423@mnemosyne.cs.du.edu>, smustopo@nyx.cs.du.edu (sofjan mustopoh) writes:
>    Now for all netter please voice your pro and con about 
>  Fujinon FMT-SX 7X50 and what is FMTR-SX and FMTRC-SX

'R' is rubber-armored, about a $50 (at discount) option. I note in
the Orion catalog that the plain FMT comes *with* a case and the
'R' comes *without*, so it's possible the 'RC' is an 'R' with a case.
Just a guess.  If the 'RC' is about $30 more than the 'R,' maybe
that's it.

>  And last one. How much better is Fujinon compare to 
>  Celestron Ultima.

I got Fujinon's 10x70 a couple years ago in the wake of a small
but unexpected financial windfall, and have nothing but praise
for the optics and construction, although I find that they're
heavy and awkward enough (with tripod) that I don't use them
as much as I thought I would.  I've obviously wondered whether
a 7x50 or 8x56 would have been a better choice.  Which leads me to
note the following:

Fujinon 10x70          76 oz.
Fujinon 7x50           50 oz. (53 oz. 'R')
Celest. Ultima 8x56    30 oz.
Celest. Ultima 7x50    27 oz.

You can read the extra 1.5 lbs. of the Fujis as 'quality' or as
'tired,' depending on perspective, I guess.  Also, the Fujis have
*only* individual eyepiece focus, also generally regarded as a
'quality' point, but one that would make them somewhat less suited
than the Celestrons for, say, birdwatching *or* if you're passing
them around in a group.

I wouldn't hesitate to recommend the Fuji 10x70 over other giants
if price were no object, but think there are some other considerations
in the hand-held sizes.  Dickinson & Dyer, in _The Backyard Astronomer's
Guide_ (Camden, 1991) recommend the 7x50 or 10x50 Adlerblick from
Carton Optics of Japan and note that 'Celestron Ultima binoculars
are similar in design and also provide very good performance,'
among binoculars in the $200-400 price class.
They say the 'Nikon 7x50 SP-HP Prostar (about $600) has the best
optics we have seen in any binocular at any price by any
manufacturer. [....]  In the same price range but a bit lighter
and optically a very close contender is the Fujinon FMT-SX 7x50....'

Good luck.

Christopher Gunn	Molecular Graphics and Modeling Lab
SPAN--KUPHSX::GUNN	Department of Medicinal Chemistry, Malott Hall
913-864-4428 or -4495	University of Kansas, Lawrence, KS  66045
From: ja@gnv.ifas.ufl.edu
Newsgroups: sci.astro
Subject: Tallahassee Clubs ???
Date: 23 Nov 92 13:07:09 -0500


Does anyone know of Astro clubs in the Tallahassee, FL area.  I'm moving there
soon and really enjoy observing in groups. I learn the sky faster this way.

Please send email since I can't read News often during the move and not at all
after.  

Thanks ............ John

ja@ifasgnv          Bitnet
ja@gnv.ifas.ufl.edu Internet

Xref: sparky sci.astro:12210 sci.space:16119
From: bill@bessel.as.utexas.edu (William H. Jefferys)
Newsgroups: sci.astro,sci.space
Subject: Re: Hubble's mirror
Date: 19 Nov 92 20:40:53 GMT
Followup-To: sci.astro
Organization: McDonald Observatory, University of Texas @ Austin

In article <BxqDzI.B1q@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:
#In article <83625@ut-emx.uucp> bill@bessel.as.utexas.edu (William H. Jefferys) writes:
#>I'll agree, the error would have been caught if the primary
#>and secondary mirrors had been tested together. There are
#>lots of simple tests that would have caught the error.
#>None were used.
#
#This is rapidly becoming a contender for Technological Myth Of The Decade.
#
#If you look at what actually happened, rather than the popular mythology,
#the fact is that three independent tests were run, and TWO OF THEM DETECTED
#THE ERROR.  At which point, Perkin-Elmer management decided that the third
#was more trustworthy than the other two, and ignored the two failed tests.

The tests to which you refer are the refractive null and
the inverse null, in addition to the faulty reflective null.
All three of them are based on the same basic interferometric
technology, and are not independent in the sense that I 
meant. You are correct, had P-E decided to investigate the 
discrepancies between the reflective null and the other two 
devices (which agreed with each other) the problem would have
been discovered. Had the optics people who built the reflective
null realized that there was a problem when they found themselves
shimming out the lens cell for the field lens with washers, the
problem would have been found. Had they measured the position of
the field lens with a PLASTIC RULER, it would have been found.
There were lots of red flags flying, and they were all ignored.

By an independent test, I meant a geometric-optics test such as a
Hartmann test that could have, fairly cheaply, detected the problem. 
I certainly don't want to be accused of promoting a Technological 
Myth; I am personally quite cognizant of the technical issues involved,
owing to my long association with the HST project. But I am using
'independent' in a different sense than you. 

Bill
Newsgroups: sci.astro
Subject: Re: Deflecting P/S-T
From: warhil@post.ntu.edu.au (Warren Hill)
Date: 17 Nov 92 09:54:16 +0900
Followup-To: sci.astro
Distribution: world
Organization: Northern Territory University

In article <10NOV92.17034867@wl.aecl.ca>, dyckg@wl.aecl.ca wrote:
> 
> dg@cam-orl.co.uk (Dave Garnett) writes:
> >If you applied a constant thrust perpendicular to the
> >track for 1 year (31e6 seconds), then the acceleration
> >required from Newton is:-
> > 
> >  a = 2 . 8000 . 1000 / (31e6)^2
> >    = 16e-9 m/s^2
> > 
> >Hence the force required is = mass . accel
> > 
> >    = 26e6 kgf
> >    = 2600 tonnes !
> 

{SOME STUFF FROM GARY DELETED HERE}

> Gary
> 

I missed the original posting, but would like to offer the following.
If mass = kg, and acceleration = m/s^2, then from the SI units we
derive F = m.a as newtons (N), not kgf !

Then, if this is what was intended, the answer should read 26e6 newtons,
or, 26 meganewtons (MN) of thrust.  As a comparison, I think that one 727
engine can deliver about 400 kN of thrust ( leading to the somewhat silly
conclusion that the earth could be "saved" by 22 Boeing 727s ).  Maybe
someone could give us a comparison with the thrust generated by the shuttle
(I don't have these figures at my finger tips).

Regards

Warren Hill
Northern Territory University
Newsgroups: sci.astro
From: fischer@physun.physics.mcmaster.ca (Phil Fischer)
Subject: Re: FITS format
Keywords: FITS, images, format
Organization: Dept. of Physics & Astronomy, McMaster University
Distribution: sci.astro
Date: Thu, 19 Nov 1992 02:18:09 GMT

In article <1992Nov16.161843.6016@cerberus.ulaval.ca> beaucham@astro.phy.ulaval.ca (Dominique Beauchamp) writes:
>Hi everybody,
>
>I'm writing a program to display FITS images.  I have some info
>about FITS format but I think I missed something.
>
>What is the length of the header?
>
>Is this length flexible?
>
>Please answer via e-mail
>to:
>
>beaucham@phy.ulaval.ca
>
>Thank you
>
>Dominique Beauchamp
>
>
>


Incidentally, there already exists a program to display fits files. It is 
called saoimage. If you would like further info let me know.

-- 
Phil Fischer                         | Hamilton, Ont.
fischer@crocus.physics.mcmaster.ca   | Canada
Dept. of Physics and Astronomy       | L8S 4M1
McMaster University                  | 416-525-9140 X 4574
Newsgroups: sci.astro
From: skjohn01@nx26.mik.uky.edu (stephen k johnson)
Subject: Good Schools?
Organization: University Of Kentucky, Dept. of Math Sciences
Date: Wed, 18 Nov 1992 23:52:52 GMT

I am looking for schools that have a good astronomy program since my  
school does not have one thank you.


					Kelly

---------------------
Stephen Kelly Johnson
SKJOHN01@MIK.UKY.EDU
---------------------
Newsgroups: sci.astro
From: phfrom@nyx.uni-konstanz.de (Hartmut Frommert)
Subject: Re: Know an adjective for black holes?
Organization: Dept. of Physics, University of Constance
Date: Mon, 16 Nov 1992 15:03:01 GMT

"Black Holean" :-))
-
 Hartmut Frommert                 <phfrom@nyx.uni-konstanz.de>
 Dept of Physics, Univ of Constance, P.O.Box 55 60, D-W-7750 Konstanz, Germany
                                           -- Eat whale killers, not whales --
From: davep@paladin.corp.sgi.com (David Packer)
Newsgroups: sci.astro
Subject: Re: Gravitational lenses
Date: 17 Nov 1992 22:39:01 GMT
Organization: Silicon Graphics, Inc.  Mountain View, CA
NNTP-Posting-Host: paladin.corp.sgi.com


I thought I saw an article on this recently in Discover magazine, I
think....


Dave

Xref: sparky sci.astro:12102 sci.space:16005
From: jfw@ksr.com (John F. Woods)
Newsgroups: sci.astro,sci.space
Subject: Re: Hubble's mirror
Date: 17 Nov 92 17:00:40 GMT
Article-I.D.: ksr.18865

gsh7w@fermi.clas.Virginia.EDU (Greg Hennessy) writes:
>PE developed a system of testing that they
>THOUGHT would be good enough. Unfortunately it was not.

According to the report, the system of testing *was* good enough.  Two of the
three tests indicated the mirror was mis-figured.  Perkin-Elmer gave exactly
the attention to those tests that a CERTAIN OTHER manufacturer of space
hardware gave to the tests indicating routine damage to a CERTAIN O-ring in
the Shuttle...

All the managers who approved ignoring those tests (who were probably rewarded
with bonuses for bringing the mirror in on-time) ought to be billed the repair
costs.  (and whoever thought to add random spacing washers to a piece of
*precision* equipment, instead of asking why it didn't fit like it was supposed
to, ought to have boxing gloves surgically attached to his hands so he won't
be tempted to screw up any *other* pieces of equipment...)
Newsgroups: sci.astro
From: anderson@stsci.edu
Subject: Request for source of lunar topo data
Organization: Space Telescope Science Institute
Distribution: na
Date: Thu, 19 Nov 1992 06:00:43 GMT

After much digging in the data sources listed in the FAQ, I have been unable to
locate:

  A set of lunar surface topographic data.  Selenocentric X, Y, Z or 
longitude, latitude, altitude would be fine.  A fairly coarse grid (~10^4 
points) would do nicely.

Anyone know of where I can obtain said data?

Chris Anderson				Science Operations Specialist
ANDERSON@STSCI.EDU			Science Planning & Scheduling
					Computer Sciences Corporation
					Space Telescope Science Institute
From: rjb12@unix.brighton.ac.uk (Titch)
Newsgroups: sci.astro
Subject: Re: Light pollution
Date: 17 Nov 92 17:41:19 GMT
Organization: University of Brighton, UK

acb20@cus.cam.ac.uk (A.C. Baker) writes:
> Astronomy is, along with the space programme, *the* biggest thing that gets 
> people interested in science. Yet more and more westerners, and others, now 
> live with light pollution that makes stars next to invisible ... possible
> links to the decline of industry and eductation etc in the UK, the US etc 
> immediately come to mind ...

Have you seen last month's Astronomy Now? Quite a large feature on light
pollution and the efforts being done to curb it.

Cheers,

Rich
-- 
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Rich Browning (rjb12@bton.unix)   * The Intel Plentium: Ethernet controller  
Department of Computer Science    * or fiendish knitting pattern?          
University of Brighton            * What!? It's a PROCESSOR???            
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Newsgroups: sci.astro