HDTenEightyP/NetNews huggingface dataset:
From: tarl@sw.stratus.com (Tarl Neustaedter)
Newsgroups: sci.astro
Subject: Re: Supernova
Date: 19 Nov 92 18:14:15 GMT
Organization: Stratus Computer, Inc.
NNTP-Posting-Host: coyoacan.sw.stratus.com

In article <1992Nov18.172149.27436@Princeton.EDU>, richmond@spiff.Princeton.EDU (Stupendous Man) writes:
>    Actually, while Tarl has explained the slow, gradual brightening of a 
> type II supernova nicely (except for the "light-hours bit" - the envelope
> of even the largest star is only light-minutes in radius),

*Blush*. I was thinking of the time for the shockwave to travel through
the star and brain-faulted on light being a different velocity.

> [flash at time of core collapse - neutrinos interact with stellar envelope]
> If I recall correctly, the "flash" is only a few seconds (minutes?) long

Interesting idea - I hadn't heard of this. But again, this would not be
perceived by the human eye as a flash, since the same spherical delay
would cause it to be minutes long.

However, if we assume that the outer envelope of the star is mostly hydrogen
and helium (a blue giant's chromosphere would not be dominated by metals
even in the late stages of life), the neutrino-provoked reactions would be:

	u + 2D  -> 2He  =>>>  H + H (sproing!)
	u + 3T  -> 3He
	u + 3He -> 3Li ==>>>> H + H + H (SSSPpPpPRoing!)
	u + 4He -> 4Li  =>>>  H + 3He

The cross-sections for some of these have got to be almighty tiny. Would
there be enough energy converted to heat in this flash to approach within 
5 magnitudes of the maximum luminosity? Otherwise, this flash would not
have even brought Sk -69.202 to naked-eye visibility.
 -- 
         Tarl Neustaedter	tarl@sw.stratus.com
         Marlboro, Mass.	Stratus Computer
Disclaimer: My employer is not responsible for my opinions.
Newsgroups: sci.astro
From: ethanb@ptolemy.astro.washington.edu (Ethan Bradford)
Subject: Re: Distance of horizon
To: palmer@sfu.ca, fiddler@concertina.Eng.Sun.COM
Organization: U. of Washington
Date: Thu, 19 Nov 1992 08:40:23 GMT

In article <1992Nov19.021430.13833@sfu.ca> palmer@sfu.ca (Leigh Palmer) writes:

   In article <lglhj3INNb0c@appserv.Eng.Sun.COM> 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?
			       -1
   Try d = R arccos ( 1 + h/R )

       d = horizon distance
       h = height above MSL (assuming horizon is at sea level)
       R = radius of Earth

This is a complicated approximation to a simple function.  The exact
answer is
  d = sqrt(h^2 + 2 R h) \approx sqrt(2 R h)

This can easily be derived by drawing a right triangle with the base
being a line from the observer to the center of the earth and the two
sides being (1) the line from the center of the earth to the horizon
and (2) the line from the observer to the horizon (lines 1 and 2 meet
at a right angle because line 2 is tangent to the surface of the
earth).

Since the cosine of the angle between the base and line 1 is R/(R+h)
and since sin(\theta) \approx \theta for small \theta, the other
formula will not be off by any significant amount.

Leigh Palmer also writes:
   I tried to find a series expansion for arccos ( 1 + z ) in my
   tables, but there ain't one there. I think I see how to figure one
   out, but I've got to go home now.

You won't be able to figure one out; there isn't one.  The derivative
of arccos(1+z) is infinite at z=0.  You will note that the exact form
doesn't have a Taylor expansion either.

-- Ethan
From: cm674@cleveland.Freenet.Edu (Erich Weber)
Newsgroups: sci.astro
Subject: CCD cameras
Date: 18 Nov 1992 13:54:54 GMT
Organization: Case Western Reserve University, Cleveland, Ohio (USA)
NNTP-Posting-Host: hela.ins.cwru.edu


Has anyone informations or practical experience with CCD cameras for
amateur astronomers (especially ST-6)?

Please send me your answers to my following E-mail-addrtess:
   weber@zdfzs.una.ac.at

Thanks in advance!      rgds. Erich Weber, BAA, Austria
From: hrubin@pop.stat.purdue.edu (Herman Rubin)
Subject: Re: Higgs Spotted? (really about Mars)
Organization: Purdue University Statistics Department
Date: Tue, 17 Nov 1992 20:20:51 GMT

In article <1992Nov17.133700.11812@cs.ucf.edu> clarke@acme.ucf.edu (Thomas Clarke) writes:
>In article <1992Nov16.231844.28715@murdoch.acc.Virginia.EDU>  
>crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:


>>       However, there *are* apparently pluvial formations on Mars.
>>       We *do* believe that there is water somewhere (at least some
>>       of us do), and there have been any number of proposals to use
>>       that water for oxygen for humans to breathe while on a Mars
>>       mission.

>Maybe we should be charitable to Mr. Quayle, but when I read his
>Mars (mis?)statement, I immediately thought of books about Mars
>I had read as a child in which scientists believed coniditions on
>Mars were much as Mr. Quayle described. 

>My thought was how sad that the head of our National Space Council
>had not learned any planetary astronomy since elementary school.

>Maybe Quayle really is quite intelligent and educated, but has bad 
>foot in the mouth disease.  Then why is he a politician?

You should be looking more closely at the discussions about our 
miseducational system.  I would not be surprised if at least 70%
of our students never get an astronomy course adequate to read
_Scientific American_.
-- 
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: (317)494-6054
hrubin@snap.stat.purdue.edu (Internet, bitnet)  
{purdue,pur-ee}!snap.stat!hrubin(UUCP)
Newsgroups: sci.astro.hubble
From: kevin@mav.com (Kevin Bagley)
Subject: Re: Lunar astronaut covers earth with thumb
Organization: Maverick International Inc.
Date: Mon, 16 Nov 92 22:05:42 GMT

In article <30473@scicom.AlphaCDC.COM> wats@scicom.AlphaCDC.COM (Bruce Watson) writes:
>On the last installment of "Space Age" Jim Lovell said while he
>was in the vicinity of the moon, he could cover the earth with his
>thumb while his arm was outstretched. (It was also attributed to
>Rusty Schweikart).
>
>A caller, who had a German accent, had trouble with this reasoned:
>

 1 & 2 deleted

>(3) We ordinary mortals here on earth can't cover the moon with 
>    a thumb with arm outstretched.
...
>What is the error the caller made? Give up? It's number (3).
>There's a full moon out tonight. Go out and try it.

The error is assuming that ordinary mortals cannot cover the moon with
a thumb with arm outstretched. Actually, you can do it with a dime. The
moon substends an angle approximately equal to the diameter of a pencil
eraser held at arms length.  It was never stated in the interview that
his arm was outstretched either, but simply that he could put his
thumb to the window and cover the earth with it.

The point being made was not one of angular measurement, but rather a
comment on how insignificant the earth seemed when view from such
a distance.

I'm always impressed with the illusion of the moon appearing larger
near the horizon.  Yes, it's only an illusion.  Anyone want to
explain the illusion?

>-- 
>Bruce Watson (wats@scicom)  Tumbra, Zorkovick; Sparkula zoom krackadomando.  

 _____  Kevin Bagley  kevin@mav.com  206-743-6659   NSS 32881
  )___)  _    _   _   Quote for the day:     "I Hate Computers!"
_/___)  (_(__(_)_/_)_ Disclaimer: Unlike other people, I eat my words
______________/                   just because they taste so good.
From: tarl@sw.stratus.com (Tarl Neustaedter)
Newsgroups: sci.astro
Subject: Re: Supernova (Was Re: P/Swift-Tuttle at last!)
Date: 18 Nov 92 14:30:56 GMT
Organization: Stratus Computer, Inc.
NNTP-Posting-Host: coyoacan.sw.stratus.com

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. 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.
-- 
         Tarl Neustaedter	tarl@sw.stratus.com
         Marlboro, Mass.	Stratus Computer
Disclaimer: My employer is not responsible for my opinions.
Newsgroups: sci.astro
From: rlm@sunlight.Physics.UIowa.Edu (Robert Mutel)
Subject: Re: CCD cameras
Organization: Department of Physics and Astronomy, University of Iowa
Date: Thu, 19 Nov 1992 01:53:00 GMT

	The Univeristy of Iowa is developing a CCD-based laboratory for an introductory course in astronomy. We have several CCD cameras in operation, including an SBIG ST-6, a Spectrasource HPC-1 and 2 PC-Lynxx's. I have placed a few sample images taken with the ST-6 from the roof of the Physics building in downtown Iowa City in a directory accessible by anonymous ftp:

ftp sunlight.physics.uiowa.edu  [128.255.32.102]
cd pub/CCDlab

set file type to binary and mget either the compressed FITS or GIF images. There
is also a text file with a brief description of the images. I plan to update this
directory with more images and a summary of lab projects being done by the undergraduate students this semester in a couple of weeks.

	 In January there will be a full lab manual available for the laboratory, including chapters on operating CCD cameras, planning for observations, image calibration and analysis, a full description of many projects, details description of photometric reduction, and appendices on sky display and image analysis software as well as hardware and software systems for automated telescopes. Anyone interested in obtaining a copy should contact me.
 
-- 
Robert Mutel
Department of Physics and Astronomy
University of Iowa
Iowa City IA 52242

Telephone: 319-335-1950      FAX: 319-335-1753
Email: rlm@sunlight.physics.uiowa.edu  (internet) 
       iowa::rlm (span)
Newsgroups: sci.astro
From: dsc@gemini.tmc.edu (Doug S. Caprette Bldg. 28 W191 x3892)
Subject: Re: Swift-Tuttle observation Sun nite
Organization: NASA GSFC CDP VLBI
Distribution: na
Date: Mon, 16 Nov 1992 22:45:11 GMT

In article <1992Nov16.162011.1@stsci.edu> hathaway@stsci.edu writes:
>
>
>
>(P.S. - a fresh posting quoted a discounting of the collision threat 
>next time around - but how about an older post that said that 
>_eventually_ the comet, or what's left of it _must_ be swept up 
>by the earth?  Until it finally dissipates, there is nothing else 
>to stop it until it happens to find terra.  Maybe not on the next 
>pass, but the 50th?, the 1000th????) 
>

Not only this, but if the comet is delayed to the extent that it 
crosses the orbit of the Earth behind (so to speak) the Earth then 
the Earth will certainly collide with the comet's tail.

Rather like Halley in 1910.

Should make for a nice meteor storm!

Newsgroups: sci.astro
From: dierick@brsux0.bro.dec.com (Dierick Dominique)
Subject: Re: Swift-Tuttle Observation Nov. 19/20, 1992
Reply-To: dierick@ketje.enet.dec.com
Organization: Digital Equipment Corporation, Brussels
Date: Fri, 20 Nov 1992 10:44:01 GMT



On pictures taken this week, a 2 degree, narrow tail was recorded from
my light poluted site. A broad dust tail seemed also on the pictures,
but much shorter.

I used a 160 Takahashi Epsilon with TP2415 Hypered, no filters used.
Printing the negative is another story. The negative is so black, I'll
have to expose about 30 minutes to get a print out of it ...


Dominique
Newsgroups: sci.astro
From: bunner@vms.macc.wisc.edu (Dana A. Bunner)
Subject: Re: I can't see stars anymore at night with naked eye
Organization:  University of Wisconsin Academic Computing Center
Date: 18 NOV 92 19:33:11    

In article <1992Nov14.031207.13073@cbfsb.cb.att.com>, wa2ise@cbnewsb.cb.att.com (robert.f.casey) writes...

>I haven't seen any stars at all for the past several months at night.

That's because there are no more stars.  I haven't seen one since October 26th.
The Supreme Being apparently vaporized all of them and now the sky is 
continually filled with a thick, swirling nebula mist.  Even the Sun and
Moon were taken, although by some miracle it does continue to brighten a bit
each morning and then darken a little in the late afternoon.

My other theory is that Wisconsin was swallowed by "The Nothing" from 
_The Dark Crystal_.

The only thing left to watch in the skies are low flying aircraft ... which
can be quite challenging at 250X on a dobsonian mount.

Dana
Newsgroups: sci.astro
From: mcdonald@aries.scs.uiuc.edu (J. D. McDonald)
Subject: Re: Prism Diagonals vs. Mirror Diagonals
Organization: UIUC SCS
Date: Fri, 20 Nov 1992 18:14:50 GMT

In article <2800016@hpgrla.gr.hp.com> edb@hpgrla.gr.hp.com (Ed Beshore) writes:

>In sci.astro, dave@canopus.as.arizona.edu (David A. Harvey) writes:


>>All you opticians out there -

>>I'm confused.  Reading some of the ads in Orion Mail Order Catalog, I get
>>the impression that Coated prism diagonals for telescopes are "better" than
>>First Surface diagonals.

> I'm going to go out ona limb here, but I'm guessing that with true binoculars
> you must have two diagonals per "telescope" to bring the views together.  Maintaining
> alignment of the diagonals would be tough, especially with the closed optics.
> Prisms, while more expensive, can be solidly mounted and would require less complicated
> adjustment.

> In most cases, you would probably loose less light with first surface diagonals.


Prism versus mirror diagonals ... a tough question.

Pro mirror: 1) only one surface, therefore no secondary reflections. If
               the diagonal is noty antoreflection coated these can be quite 
               bad. Even coated they are noticeable on bright stars.
            2) no aberration introduced ... assuming a flat surface.

Con mirror: 3) Plain aluminized/SiO overcoat mirrors only reflect 85% or so.
               However, enhanced aluminum gets up to 96% at the peak
               of the eye's spectral response curve (but is worse in UV).
               Overcoated silver (MgF2 or better ThF4) reflects 99%
               across the visible but is dead as a doornail in the UV. It
               does not tarnish but is very fragile, and is not available
               any more on the amateur market ... You would have to
               buy an uncoated mirror and have it coated at great expense.

Pro prism:  1) With a three layer antireflection coating on the input
               and output faces, they will transmit >98% average in the
               visible, which is excellent. Uncoated, they transmit 
               about 93 or 94%.

Con prism:  1) They have a limited f/number unless coated with aluminum on
               the hypotenuse, which ruins the transmission. I suspect  this
               to be a problem only at very low f/numbers.

            2) They introduce aberrations; spherical aberration and 
               chromatic aberration everywhere and astigmatism off center. 
               This is zero problem at f/15, negligible at f/10, and
               a bit outside the diffraction limit at f/5. At f/3 it's bad.

Bottom line: for an f/8 or slower scope, a tossup, which wins depends
on the coating and surface quality. At f/4.5, get a diagonal.

Doug McDonald
Xref: sparky sci.astro:12124 sci.space:16021
From: mario@cs.man.ac.uk (Mario Wolczko)
Newsgroups: sci.astro,sci.space
Subject: Interesting Swift-Tuttle Scenario ...
Date: 16 Nov 92 22:19:54 GMT
Followup-To: sci.astro
Organization: Dept Computer Science, University of Manchester, U.K.

Here's something to think about.  Suppose, after S-T has passed out of
the range of our best telescopes, and good orbital elements have been
obtained, all calculations show a direct hit on Earth is very likely.
However, even then there will be no certainty until S-T is reacquired,
inbound, presumably many decades hence. 

What will happen?  

Here's my guess: there'll be a flurry of discussion and ideas on how
to divert the comet, but after that everything will die down and the
whole thing will lie dormant (like the comet ;-) -- apart from the
occasional minor study -- until the early 22nd century.  Then, the
schemes will be dusted off and re-assessed, some new ones invented,
and -- nothing will happen until either the comet is reacquired, or
the last moment to actually start building something arrives.

Of course, by then S-T could be an exhibit in the Natural History
Museum in Lunar Orbit, or a tour stop on the way to Alpha Centauri ...

T-48848 days and counting!
From: rub@aero.org (Jerzy W. Rub)
Newsgroups: sci.astro
Subject: Re: Experiences with telescope mail order
Date: 23 Nov 92 09:34:03
Organization: The Aerospace Corporation, Los Angeles, California
NNTP-Posting-Host: solarium.aero.org
In-reply-to: creps@silver.ucs.indiana.edu's message of Fri, 20 Nov 1992 20:18:53 GMT

I, too, have delt with Orion on several occasions and recently made a large
eyepiece purchase for our club at work.  My experience with Orion has always
been positive.  They know what they are talking about, do let you know if
something is out of stock and how long before they have it again, and they
just deliver.
Newsgroups: sci.astro
From: beaucham@astro.phy.ulaval.ca (Dominique Beauchamp)
Subject: FITS format
Followup-To: beaucham@phy.ulaval.ca
Keywords: FITS, images, format
Organization: Universite Laval, Ste-Foy, Qc, Canada
Distribution: sci.astro
Date: Mon, 16 Nov 1992 16:18:43 GMT

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
From: markv@pixar.com (Mark T. VandeWettering)
Subject: Re: Telescope Making
Organization: Pixar -- Point Richmond, California
Date: Mon, 16 Nov 1992 18:42:40 GMT

adams@engin.umich.edu (Christopher David Adams) writes:

>I would like to build my first telescope and need some advice
>or suggestions.  I'm primarily interested in deep sky astrophotography.
>I'm thinking of building a 12" f4 Newtonian reflector and grinding my
>own mirror.  Any hints, cautionary statements, source info, etc. would be
>greatly appreciated.

I would caution you to probably build a smaller one first.  You will learn
enough to make your eventual 12" a much better scope.  Building a smaller (say
6") scope is much faster than trying to make a 12", and you can decide whether
you really like telescope building.  If you are interested in astrophotography,
you will need to consider a mount for your scope, and the bigger they are, 
the harder they are to mount sufficiently well.  f/4 also seems a bit fast, 
you will get quite a bit of coma around the edge of the field.

Best advice:  Find a club which specializes in this kind of stuff and 
listen to the old hand's advice.  Astronomy magazine publishes a list of 
clubs yearly (I forget which issue).

				Mark T. VandeWettering
From: j.jahn@abbs.hanse.de (Jost Jahn)
Newsgroups: sci.astro
Subject: Sunspots at 16.11.1992.
Reply-To: j.jahn@abbs.hanse.de
Date: 16 Nov 92 19:14:00 MET
Distribution: sci
Organization: ABBS AstroMail, D-W 2121 Dahlenburg / Germany
X-Version: ZerUU V6.45c

Sunspots at 16.11.1992., 0 h UT.

No.    Pos.  Cl.  Ar.  Mag. SF  F  M  X
---------------------------------------
7334 13N 64W Cso   50   b
7335 18S 54W Eho  350   b    2
7337 08N 14E Hax   80   a
7339 18S 29W Axx    0   a
7340 08S 46E Bxo   10   b
7341 16S 11W Bxo   10   b
7342 07S 22E Bxo   10   b
7344 14S 68E Bxo   10   b


No optical or x-ray flares yesterday observed.


 
--
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------------------------- for amateur astronomers ----------------------------
    + 49 5851 7896 / V.21, V.22, V.22bis, V.32, V.42, V.42bis and MNP5
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Newsgroups: sci.astro
From: metares@well.sf.ca.us (Tom Van Flandern)
Subject: Re: Galilean Electrodynamics?
Organization: Whole Earth 'Lectronic Link
Date: Thu, 19 Nov 1992 04:28:52 GMT


schlegel@cwis.unomaha.edu (Mark Schlegel) writes:

> ...  "Galilean Electrodynamics"  ...  The editorial board is made of up of
> ...  Barnes, Hayden, Parshin, Whitney  ...  Editor: Petr Beckmann  ...
> Does anyone know about whether the papers published by this group have any
> validity in the general physics world?  They seem to believe there are
> obvious contradictions between general rel. and observation.

     GE is a fine publication well deserving of the attention of serious
astronomers and physicists.  It is peer-reviewed.  It does contain some flaky
papers which often get cited as evidence of the low overall quality of the
journal.  But in my opinion, the main journals of the field contain their
share of flaky papers too.  But those are accepted as a fact of life.

     However, it would be fair to say that GE tends to err more on the side
of publishing if there is reasonable doubt about a paper, while some well-
known journals tend to reject if there is any doubt.

     In his book, Beckmann advocates the view that gravitational potential
serves as a medium modifying the speed of light.  In particular, he suggests
that the speed of light, c, will be unchanged by the Earth's orbital velocity
around the Sun; but will be c +/- v for the Earth's spin velocity, v, because
spin is a motion with respect to the local gravitational field.  This is a
significant departure from standard SR.  So far, no experiment has ruled out
the possibility that Beckmann may be correct on this point.  To its credit,
the GE journal publishes articles which sometimes criticize the editor
(Beckmann)'s own opinions.  -|Tom|-

-- 
Tom Van Flandern / Washington, DC / metares@well.sf.ca.us
Meta Research was founded to foster research into ideas not otherwise
supported because they conflict with mainstream theories in Astronomy.
Newsgroups: sci.astro
From: hathaway@stsci.edu
Subject: Swift-Tuttle observation Sun nite
Organization: Space Telescope Science Institute
Distribution: na
Date: Mon, 16 Nov 1992 21:20:11 GMT

The skies finally cleared in Maryland Sunday night.  As mentioned, 
I picked up Comet Swift-Tuttle in 7X35 binocs as soon as it got dark 
(~5:44 pm) and soon thereafter star-hopped to it in a 12.5" f/8 
Newtonian.   Used a 55mm, 32mm, and 16mm eyepieces.  I recommend 
that anyone who can get to a 'scope take advantage of this (brief?) 
clear spell to put some aperture and power onto it.  It had a lot 
of coma with many faint variations in the fuzziness.  I thought I 
glimpsed (averted vision and shaking the scope) a big curve like a 
bow-wave curling around and away from it.   It looked like some of 
the drawings I've seen of classic comets.   Confirmation (or NOT) 
would be welcome. 

BTW, I saw Comet Halley in this same scope about fifty times and even 
with the by-now-rather-thinner mirror coating, this comet compared 
favorably with those sights.  

So get out there with some big guns and don't be afraid to crank up 
the magnification.  Photos won't do it justice, as your eyes can 
pick up more range of brightness (and faintness) than paper can hope to do. 

Wm. Hathaway 



(P.S. - a fresh posting quoted a discounting of the collision threat 
next time around - but how about an older post that said that 
_eventually_ the comet, or what's left of it _must_ be swept up 
by the earth?  Until it finally dissipates, there is nothing else 
to stop it until it happens to find terra.  Maybe not on the next 
pass, but the 50th?, the 1000th????) 

Newsgroups: sci.astro