HDTenEightyP/NetNews huggingface dataset:
From: billn@hpcvaac.cv.hp.com (bill nelson)
Subject: Re: Mirror Testing
Organization: Hewlett-Packard Company, Corvallis, Oregon USA
Date: Sat, 12 Dec 1992 10:43:37 GMT

drummond@taligent.com (Brian Drummond) writes:
: 
: Questions: 
: 
: * What are the advantages/disadvantages of using the Ronchi test over
: the Foucault test?

The Foucault test does not work well for fast mirrors - the shadows are
too dim.

: By the way, 15 years ago I made a 6" mirror using Sam Brown's book
: "All
: About Telescopes" from Edmund Scientific and made a Foucault tester
: that
: was described in that book.  I finally had someone else test the
: mirror
: (with the Ronchi test) and the person that made the test stated that
: the
: figure was between 1/4 and 1/8 wave across the figure.

I love the book. It is probably the best all around easy to understand
book on telescopes in existance.

Bill
From: tordm@vana (Tord G.M. Malmgren)
Newsgroups: sci.astro
Subject: Thanks! (was: SETI)
Date: 14 Dec 92 13:32:11 GMT
Reply-To: TordM@VanA.PhySto.SE
Organization: Department of Physics, University of Stockholm -- Sweden


 better late than never; many thanks to the people who responded to
my query about S.E.T.I.! In order of appearance:

 Simon Peter Ellingsen
 Larry Klaes
 Dr. Edward T. Olsen
 Mark Schlegel
 Bob Arnold

and

 Jon

the material sent to me was extensive and interesting. Thanks again!




---------------+--------------------------------+----------------------------
 Tord Malmgren | InterNet: TordM@VanA.PhySto.SE | These opinions are my OWN,
               | BITNet  : TordM@SESUF51        | and NOT of this department!
---------------+--------------------------------+----------------------------
 Department of Physics, University of Stockholm -- Sweden (Northern Europe)
Newsgroups: sci.astro
From: neely@iowasp.physics.uiowa.edu
Subject: Re: Planet viewing
Organization: Department of Physics and Astronomy, University of Iowa
Date: Mon, 14 Dec 1992 19:20:15 GMT

In article <1992Dec10.153922.29564@siemens.co.at>, howdii@patty.gud.siemens.co.at () writes:
> I can not easily believe, that JUPITER can also be seen during bright daylight
> like VENUS, because Venus can get much more brighter then Jupiter. 


I went to the 1991 Texas Star Party and at 2:00 in the afternoon I could
see right in a line: the Sun, Venus, Jupiter, and then the moon.

Of course, observing at around 6,000 feet in VERY arid conditions helped
a lot.

Here in Iowa, I have seen Venus in the daytime if the weather conditions
permit.

Clear Skies

			-Matt Neely

Newsgroups: sci.astro
From: eng20204@nusunix1.nus.sg (LEE MUH HWA)
Subject: Star Mar Gifs
Organization: National University of Singapore
X-Newsreader: TIN [version 1.1 PL6]
Date: Tue, 15 Dec 1992 02:36:14 GMT

Can anyone tell me whether that is an anonymous ftp site for star maps
gifs, photographs of planets and the Moon?

Thanks.

Newsgroups: sci.astro
From: billn@hpcvaac.cv.hp.com (bill nelson)
Subject: Re: What would happen if
Organization: Hewlett-Packard Company, Corvallis, Oregon USA
Date: Sat, 12 Dec 1992 10:05:58 GMT

jcarl@jabba.ess.harris.com (Joe Carl Jr.) writes:
: 
: The moons orbit around the earth is approximately 27 days,  the earths
: orbit around the sun is 365 days, a factor of about 13.
: For the moon to have a period of 365 days we need to increase its 
: orbital radius according to Keplers laws by a factor of the
: third root of 13 squared or about 5.6
: So the moon needs to be 5.6 times further from the earth than it currently
: is.  The question is, does this represent a stable orbit
: Not in a Lagrangian sense but in the sense that the Earth-Moon orientaion
: now is stable?

I assume that you are looking for a 365 day orbit around the Earth.

: So If I start out with a full moon, would it always be a full moon?
: What would this new orbit look like to Earthings?

Well, It would always be full. It would also be at its highest in the
sky at local solar midnight.

Bill
Newsgroups: sci.astro
From: chris@chrism.demon.co.uk (Chris Marriott)
Subject: Re: Earth's Orbit if no other planets 
Distribution: world
Organization: None
Reply-To: chris@chrism.demon.co.uk
X-Mailer: Simple NEWS 1.90 (ka9q DIS 1.19)
Date: Tue, 15 Dec 1992 15:12:45 +0000

In article <9212150607.AA09164@cpsnet2.cps.edu> DAVID_JOHNSON@cpsnet2.cps.edu writes:

>One of the people at work and I were having a discussion of astronomy
>vs.  astrology, and the subject of the Earth's orbit came up. 
>Specifically, this person believed that if there were no other planets
>in the solar system, then the Earth would have a different orbit than it
>does now.  We were discussing various scenarios, and considered both all
>other planets being removed from the existing configuration, and the
>formation of Earth by itself.  I disagreed that the orbit would be any
>different, giving the same mass of the Earth and Sun, and all other
>factors other that the existence of the other planets would remain the
>same.
>
>Comments?
>

If all the other planets were to suddenly disappear, the Earth's orbit
WOULD be very slightly different in the future.  The gravitational
attraction of the planets "perturbs" the orbit of the centre of mass
of the Earth/Moon system from the keplerian ellipse it would otherwise
follow around the sun.  Unless you're interested in predicting precise
positions of bodies in the future and/or past, though, the perturbations
are quite negligible compared to the gravitational attraction of the
Sun (and, of course, the Moon!).
-- 
--------------------------------------------------------------------------
| Chris Marriott                           | chris@chrism.demon.co.uk    |
| Warrington, UK                           | BIX: cmarriott              |
| (Still awaiting inspiration              | CIX: cmarriott              |
|  for a witty .sig .... )                 | CompuServe: 100113,1140     |
--------------------------------------------------------------------------
 
Xref: sparky sci.astro:13163 sci.physics:21216
From: steinly@topaz.ucsc.edu (Steinn Sigurdsson)
Newsgroups: sci.astro,sci.physics
Subject: Re: Detecting Second-Order GR Effects in Binary Pulsars
Date: 15 Dec 92 10:49:37
Organization: Lick Observatory/UCO
	<1992Dec14.205537.12618@s1.gov>
NNTP-Posting-Host: topaz.ucsc.edu
In-reply-to: lip@s1.gov's message of 14 Dec 92 20:55:37 GMT

In article <1992Dec14.205537.12618@s1.gov> lip@s1.gov (Loren I. Petrich) writes:


	   About the precession rate, is there an alternate theory of
   gravity that predicts (1) a significant departure from the GR value
   for the HT pulsar and (2) nearly perfect agreement for the Solar
   System?

Come now Loren, you should know that one. There are several sets
of theories that predict agreement with the solar system and
significant departure from one of the GR predictions for the HT
pulsar - which is compensated for by a shift in some other parameter
to get a match with the result. I further claim that a sufficiently
free theory can always be constructed to match all the observed
constraints, both strong field, weak field and radiative - the
problem is most sets of such theories require an arbitary number
of free paramters and become increasingly ad hoc as more observations
become available. Certainly GR is by far the most elegant and simple
of the published theories still consistent with observation.

As I understand it, the fuss over the Taylor & Damour paper
is because Damour noted that there are unconstrained theories
away from the conventional PPN theories that are ruled out
by observations - essentially Damour et al constructed a new
(infinite) family of theories of gravity...


*  Steinn Sigurdsson   			Lick Observatory      	*
*  steinly@lick.ucsc.edu		"standard disclaimer"  	*
*  The laws of gravity are very,very strict			*
*  And you're just bending them for your own benefit - B.B. 1988*
Newsgroups: sci.astro
From: gak@wrs.com (Richard Stueven)
Subject: Re: Hi Observer
Reply-To: gak@wrs.com
Organization: Wind River Systems, Inc.
Date: Mon, 14 Dec 1992 18:50:38 GMT

In article 71521@cup.portal.com, FuzzyM@cup.portal.com (Paul J Mortfield) writes:
>Sympathy, YOU want sympathy..
>
>Yes I've seen the comet. Atleast a dozen times. HOWEVER only have been able
>to take photos with the schmidt ONCE!!!!! 

Photos?!?  At least you have a _camera_!

# define YORKSHIRE_MODE on

Luxury.  We 'ad to live ('undred and seventy of us) in t'bottom of t'septic tank!*

# define YORKSHIRE_MODE off

have fun
gak

---
Richard Stueven       AHA# 22584 |----------| Monday is a work day
Internet:            gak@wrs.com |----GO----| Tuesday's much the same
ATTMAIL: ...!attmail!gakhaus!gak |---SHARX--| Wednesday comes and goes away
Cow Palace:            107/H/3-4 |----------| Thursday's back again

* :-) for the Monty-Python-impaired!
Xref: sparky sci.astro:13121 sci.physics:21147
From: lip@s1.gov (Loren I. Petrich)
Newsgroups: sci.astro,sci.physics
Subject: Re: Detecting Second-Order GR Effects in Binary Pulsars
Date: 14 Dec 92 20:55:37 GMT
Organization: LLNL

In article <Bz8pq3.CKs@well.sf.ca.us> metares@well.sf.ca.us (Tom Van Flandern) writes:

	[A supposed extra GR parameter...]

>     I'm happy to.  Quoting from the cited Ehlers et al. reference:

>     "... leads to an expression for the average rate of energy loss due to
>gravitational radiation of the form
>     - dE/dt = A (G / c^5)  (d^3 Q-sub-alpha-beta / dt^3)  (d^3 Q-super-
>alpha-beta / dt^3),
>where Q-sub-alpha-beta is the quadrupole moment of the system, and A is a
>numerical constant.

>     "...  The most commonly quoted value (Einstein 1918) is A = 1/45; as far
>as we know, no value greater than this has been claimed.  However, all
>derivations are subject to one or more of the objections discussed earlier,
>which may invalidate the derivations altogether, or lead to changes of A of
>the same order of magnitude as the results claimed.  Therefore, at present
>nothing can be said about the value of A (except that it is nonnegative,
>...).

	Unfortunately, that does not tell us too much.

	I've yet to see any "permeability" parameter in any statement
of Einstein's equations, for instance.

	Checking GR work more recently than Einstein's, such as
Misner, Thorne, and Wheeler's big book, reveals a flux exactly the
same as Einstein's value, to lowest order.

	The only thing that might be somewhat questionable, as far as
I can see, is the use of all-retarded potentials. However, the
assumption of all-retarded (and no-advanced) potentials does give the
right result for macroscopic electromagnetism and elementary-particle
interactions, however.

	For those not quite familiar with this question, a retarded
potential is one that corresponds to an outgoing wave, while an
advanced potnetial corresponds to an incoming wave. If one assumes
that there are no waves coming in, one works with all-retarded
potentials.
	
	The HT pulsar's orbit decay is consistent with the G-wave flux
calculated with all-retarded potentials, which is consistent with all
other field-theory results to date.

>     I hope this helps.  BTW, your posting contained an excellent description
>of the data anaylsis.  One can see clearly why any theoretical uncertainty in
>how much gravitational radiation is predicted by GR would not change the
>formal errors of the solutions from observations.

	Thanx for your flattering comments about my exposition of the
question. BUT, for the amount of G-wave flux to be theoretically
uncertain, it is also required that the precession rate be
theoretically uncertain, or else that both quantities be controllable
with fudge factors that can be adjusted to give a line of agreement.
However, GR predicts an unambiguous value for _both_ the precession
rate _and_ the G-wave decay rate.

	About the precession rate, is there an alternate theory of
gravity that predicts (1) a significant departure from the GR value
for the HT pulsar and (2) nearly perfect agreement for the Solar
System?
-- 
/Loren Petrich, the Master Blaster
/lip@s1.gov
Newsgroups: sci.astro
From: dsc@gemini.tmc.edu (Doug S. Caprette Bldg. 28 W191 x3892)
Subject: Re: Telescope question from rank novice
Organization: NASA GSFC CDP VLBI
Distribution: na
Date: Thu, 17 Dec 1992 21:11:14 GMT

In article <BzEvCL.HH1@unx.sas.com> saseph@hal.unx.sas.com (Ed Hughes) writes:
>
>Does anyone out there know who manufactures the
>6" or so reflector telescope that Brookstone
>(the gadget store) sells?  Is it one of the 
>manufacturers-to-avoid?  This thing regularly
>sells for around $450 (but that's Brookstone
>dollars) and is on sale now for $299.  A tripod
>and some selection of lenses is included.  I'm
                       ^^^^^^
		       Probably you mean eyepieces.

>not sure of the type of mount, since I just read
>the FAQ today and learned about equatorial and
>altazimuth.
>

I don't know the specifics of this scope, but a
6" scope for $299 is almost certainly a Newtonian.
(Actually, it is likely to be smaller than 6")

I would be very suspicious of any tripod mounted Newtonian.
Tripods and Newtonians simply don't go well together--they
tend to interfere near the zenith.

A portable Newtonian made by a manufacturer with telescope
experience will normally be pedestal mounted.  Then, there
should be no interference between the tube and the legs.

In a tripod the legs form a sort of A-frame.  In a pedestal,
the legs are attached more or less at a right angle, near
the bottom of the verticle pipe which supports the mount.

in ASCII:



   mount                        mount
    /\                           ||
   /  \                          ||
  /____\                         ||
 /      \                        ||
/        \                  =====||=====
^        ^                  ^          ^
 Tripod                        Pedestal

Hope this helps.

--
dsc@gemini.gsfc.nasa.gov  
 |  Regards,         |   Hughes STX                |    Code 926.9 GSFC        |
 |  Doug Caprette    |   Lanham, Maryland          |    Greenbelt, MD  20771   |
 -------------------------------------------------------------------------------
"There is no way to peace; peace is the way." -- Gandhi

Newsgroups: sci.astro
From: hathaway@stsci.edu
Subject: Re: Which Lunar Eclipse Was Darker?  Dec 82 or 92?
Organization: Space Telescope Science Institute
Distribution: na
Date: Fri, 11 Dec 1992 22:59:49 GMT

In article <roelle.724112089@uars_mag>, roelle@uars_mag.jhuapl.edu (Curtis Roelle) writes:
> 
> So sci.astro readers, which was darker?  The December 1982 or the
> December 1992 eclipse?
> 
> Curt

I saw the '82 eclipse from Illinois where the moon was well up in a dark 
sky during totality.  Just on my recollection, I think the '82 one was 
slightly darker than the '92 one.  I only lost naked-eye sight of the 
'92 one for a few minutes, while the '82 one was virtually gone for 
many minutes.  

Wm. Hathaway
From: sla@umbra.UCSC.EDU (Steve Allen)
Newsgroups: sci.astro
Subject: Re: info sought on Lick observatory "amateur" night
Date: 20 Dec 1992 05:09:06 GMT
Organization: UCO/Lick Observatory
NNTP-Posting-Host: umbra.ucsc.edu
Summary: only in summers when there is no budget crisis

In article <1992Dec19.162706@cs.man.ac.uk> mario@cs.man.ac.uk
(Mario Wolczko) asks about visiting Lick Observatory.

Lick Observatory is usually open to visitors every day except Christmas.
This means that the gift shop is available in the afternoon, and every
half-hour the guide will escort a tour of the 36-inch refractor.  The
visitors gallery at the Shane 3-m reflector is also open.

On summers when California is not having a budget crisis, 10 Fridays nights
are visitors nights.  Tickets can be obtained for free by writing to the
observatory.  On such nights visitors are allowed to look through both
the 36-inch refractor and the 40-inch reflector.  Objects are chosen by
the staff, and they are usually the "easy" ones which will appeal to
the general public.  For the past several summers, visitors nights
have not been held because of the poor state budget.

Some private tours can be arranged (usually for educational purposes).
These must be arranged in advance, and I believe they may now require
the touring group to offset some of the cost.  For exact details,
contact the observatory directly.

The road to Mt. Hamilton is a state highway.  It is only closed if
there is snow or imminent expectation of snow.  This is usually rare,
but it did happen two days ago.
_______________________________________________________________________________
Steve Allen          | That was the equation!         |   sla@lick.ucsc.edu
UCO/Lick Observatory | Existence!...Survival must     | If the UC were opining,
Santa Cruz, CA 95064 | cancel out programming! -- Ruk | it wouldn't use me.
From: job@head-cfa.harvard.edu (Jeffrey Oliver Breen)
Newsgroups: sci.astro
Subject: Re: Nemesis References Wanted
Date: 12 Dec 92 21:45:13 GMT
Organization: Smithsonian Astrophysical Observatory, Cambridge, MA,  USA

In article <1g5o5oINNh16@iskut.ucs.ubc.ca> gibson@crisium.geop.ubc.ca (Brad Gibson) writes:
>------------------------------------------------------------------------------
>
>Can someone fill me in on some recent (last few years) references (refereed
>preferred, but others are welcome) on the so-called "Nemesis" star/hypothesis?
>Basic info like ... orbital period about Sun, ellipticity,
>proposed mass (brown dwarf?), etc. would be appreciated as well.
>

I did a paper on this theory a couple of years ago for an undergrad
general science course.  To summarize:  I don't buy it.  As the
orbital period must match the period of mass extinctions, cratering,
etc., (26 Myr), you wind up with a semi-major axis of about 9 x 10^4
A.U.  If we assume it passes through a dense region of the Oort cloud
once per orbit, you require a perihelion distance of 2 x 10^4 A.U. and we
find an aphelion distance of 1.6 x 10^5 A.U. - that's 0.78 pc!!  And that's
more than half the way to Proxima or alpha Centauri.  Barnard's star
is something like 1.8 pc distant, and Wolf 359 is almost 2.4 pc.

So at aphelion, Nemesis would be getting pretty close to other star 
systems, and susceptible to severe gravitational pertubations.  One 
should not expect its orbit to be stable enough to come by and clobber
us every 26 Myr like clockwork.  I haven't followed the debate since I
wrote the paper a couple of years ago, so I don't have any recent
references to share, but here are the most relevant:

Fernandez, J.A. and Ip, W.-H.  1987, "Time-Dependent Injection of Oort
Cloud Comets into Earth-Crossing Orbits"  Icarus, 71:46

Hills, J.G. 1984, "Dynamical constraints on the mass and perihelion
distance of Nemesis and the stability of its orbit"  Nature, 311:636

Hut, P.  1984, "How stable is an astronomical clock that can trigger
mass extinctions on Earth?"  Nature, 311:638

Matese, J.J. and Whitmire, D.P.  1986, "Planet X and the Origins of
the Shower and Steady State Flux of Short-Period Comets"  Icarus, 65:37

Torbett, M. and Smoluchowski, R.  1984, "Orbital stability of the
unseen solar companion linked to periodic extinction events"  Nature, 311:641

Weinberg, M.D., Shaprio, S.L., and Wasserman, I.  1986, "The Fate of
Wide Binaries in the SOlar Neighborhood: Encounters with Stars and
Molecular Clouds"  Icarus 65:27

-- 
+-----------
| Jeffrey Oliver Breen   Harvard-Smithsonian Center for Astrophysics,
| (617) 495-7252         60 Garden St., Room B-340, MS 70, Cambridge, MA  02138
|
From: lucas@watson.ibm.com (Bruce Lucas)
Newsgroups: sci.astro
Subject: lunar eclipse from an airplane
Date: 11 Dec 92 18:37:23 GMT
Distribution: sci
Organization: IBM T.J Watson Research Center
Disclaimer: This posting represents the poster's views, not necessarily those of IBM


By pure coincidence, I happened to be flying (as a passenger) in a
single-engine airplane from Maine to New York during the eclipse.
We were on the ground in Bedford Mass. to drop off a colleague along
the way just in time to see the Earth's shadow completely engulf
the moon.  Fortunately I had the foresight to bring my binoculars
with me, for some very nice views.
 
On our way from Bedford to White Plains the moon was mostly behind us,
but at one point I looked back to note the reappearing crescent of the
moon, and pointed it out to the pilot.  He treated us all to a better
view by flying a little circle (unfortunately, only once around).
The banked attitude of the plane gave us a fantastic view of the
reappearing moon, Orion reclining on the horizon, and the Pleiades
as a fuzzy patch visible by averted vision while looking at the moon.
We happened to be between air traffic controllers at the point so we
didn't have to explain anything, but a conversation overheard between
a controller and another airplane made it clear they were doing something
similar.  I suppose planes all over the country were making little circles
in the sky last night.
 
Bruce
Xref: sparky sci.astro:13253 sci.physics:21399
From: pp@cbnewsl.cb.att.com (peter.peng)
Subject:  buying a new telescope
Organization: AT&T Bell Laboratories
Distribution: na
Date: Mon, 14 Dec 1992 18:45:56 GMT
Keywords: telescope, buying

I'm currently shopping around for my first telescope.
Would any of you please give me some advice.......

Some question which I can think of:

1) what are the advantages and disadvantages of refraction telescopes
   vs. reflection?
2) what to look out in mounting methods? Wood vs. Al?
3) I'm a beginner in this field, so I'm starting out looking at the moon
   some near by planets. But I would like get a telescope for more distant
   viewing for the future.
4) Is motor mounting really necessary for my situation?
5) where to find better prices? I live in NJ.
6) what size (power) of telescope is necessary and flexible enough for amateur v
7) what are the brands to consider? to avoid?
8) any specific recommendation for under $500?
9) I would also like to attach my Canon A1 camera to take some shots, Are there
   any things to watch out for?

please email me directly.
Thanks in advance......

Peter Peng
attbl!hotoup!peng
From: miker@yuma.ACNS.ColoState.EDU (Mike Riley)
Newsgroups: sci.astro
Subject: My SC corrector plate is dirty. Help!
Date: 20 Dec 92 18:56:57 GMT
Distribution: na
Organization: Colorado State University, Fort Collins, CO  80523

In looking at Mars last night through my 10" Meade SC, I noticed ghost 
images of the disk, which led to inspecting the optics.  There appears 
to be a misty coating on both the inside and outside of the corrector plate.  

I'm tempted to remove the corrector plate to carefully clean it (I've cleaned
enough Nikon lenses to know I can ruin the coating!), but I'm put off by
the manual's warning of alignment problems.  Has anybody else experienced
this problem, and have you cleaned/would you recommend cleaning the
corrector plate?  (I would also gently dust of the primary if I were to do
this.)

Any replies would be appreciated.


    
 _________________________________________________________    
|Mike Riley    Internet: miker@yuma.acns.colostate.edu    |
|              Phone: (H)(303) 482-8967                   |
|_________________________________________________________|