HDTenEightyP/NetNews huggingface dataset:
From: higgins@fnala.fnal.gov (Bill Higgins-- Beam Jockey)
Newsgroups: sci.astro
Subject: Re: A 100 Billion?  (and Nemesis again)
Date: 14 Oct 92 17:34:04 -0600
Organization: Fermi National Accelerator Laboratory
NNTP-Posting-Host: fnala.fnal.gov

In article <1992Oct14.045250.2312@zia.aoc.nrao.edu>, dbriggs@zia.aoc.nrao.edu (Daniel Briggs) writes:
> In article <STEINLY.92Oct13114043@topaz.ucsc.edu>
>   steinly@topaz.ucsc.edu (Steinn Sigurdsson) writes:
>>There is one star in our solar system.
> 
> Well, *probably*.  ;)  
[description of search for hypothetical red dwarf Nemesis]
> The basic search
> strategy is to teach an automated telescope to do the parallax
> measurements, and go through the whole sky down to some reasonable limiting
> magnitude.  

Shouldn't this pop right out of the Hipparcos data?  Hipparcos is an
ESA satellite launched in 1989.  It has a small telescope to do
astrometric measurements, including parallax, on essentially the whole
sky.   The spacecraft ran into some trouble at launch-- it was
intended for geosynchronous orbit but wound up in some nasty ellipse--
but last I heard, it was able to collect most of the data of the
original mission, and is still going.

Naturally a space-based telescope can do better than a ground-based
one of the same size, since the stars appear much less fuzzy.  But
Hipparcos doesn't have a very big telescope (I'm not gonna quote
apertures from memory, not after my solar-sail gaffe yesterday), so
maybe Dan's friends would like to use a bigger scope to go after
dimmer stars.  In any case the Hipparcos folks ought to be able to set
some limit on dim, high-parallax Nemesis candidates.

> You have to admire a scientist who is willing
> to bet a fair chunk of his career on a search that could be fantastically
> important, but in all probability will come up null.

Agreed.

Bill Higgins, Beam Jockey              | "I'm gonna keep on writing
Fermi National Accelerator Laboratory  | songs until I write the song
Bitnet:           HIGGINS@FNAL.BITNET  | that makes the guys in
Internet:       HIGGINS@FNAL.FNAL.GOV  | Detroit who make the cars
SPAN/Hepnet:           43011::HIGGINS  | put tailfins on 'em again."
                                            --John Prine
Newsgroups: sci.astro
From: gawne@stsci.edu
Subject: Re: rumor concerning Saturn's rings
Organization: Space Telescope Science Institute
Distribution: na
Date: Tue, 13 Oct 1992 13:32:18 GMT

In article <1bdc69INNjmk@usenet.INS.CWRU.Edu>, 
mal11@po.CWRU.Edu (Matthew A. Lewis) writes:
> 
> Could someone please tell me when the rings around Saturn were
> discovered????
> 
> I heard an rumor that people in ancient times could see them (and
> a whole lot of other stuff) with the naked eye.....
> 

Galileo reported seeing something extending away from Saturn that he
described as being like ears.  Apparently Huygens was the first person
to make the mental leap required to recognize that he was looking at 
a ring around a planet.

As for naked eye visibility of the rings?  I doubt it.  The human eye
can't resolve Jupiter's moons, and the angular resolution needed for that
task is a factor of three or so less than the angular resolution necessary
to resolve Saturn's rings from the planet.  The fundamental limit is an
aperture (pupil) size of 7mm at the most.  Even Galileo's little telescope
more than doubled the aperture.

-Bill Gawne,  Space Telescope Science Institute
Newsgroups: sci.astro
From: mock@space.mit.edu (Patrick C. Mock)
Subject: Re: Discrete Red Shifts
Originator: mock@benz
Reply-To: mock@space.mit.edu (Patrick C. Mock)
Organization: MIT Center for Space Research
Date: Wed, 14 Oct 1992 21:27:07 GMT


In article <Bw3FKv.CDM@well.sf.ca.us>, metares@well.sf.ca.us (Tom Van Flandern) writes:
> 
> mock@space.mit.edu (Patrick C. Mock) writes:
> 
> > In summary the PSA is notorious for false alarms and it can be fooled by
> > nonperiodic correlations.  ...  I will remain skeptical of these results
> > until Tifft, Guthrie, Napier, etc. use better tools to analyze their data.
> 
>      There is just one thing wrong with your skeptical analysis of the
> redshift periodicity, and speculations about what might have caused a false
> signal: The uncorrected observed redshifts show no significant periodicities
> whatever.  Only after redshifts in all directions are corrected for the
> galactic rotation of the Sun and orbital motion of the Earth does the
> periodicity pop out.  The same periodicity has now appeared in two different
> independent samples of galaxies.  PSA (power spectrum analysis) was the tool
> available to the researchers.  It may not be the best possible tool, but it
> is certainly adequate for this purpose.  The resulting periodicities have
> undeniable statistical significance.
> 
I've done a fair bit of timing analysis in my previous career as an electrical
engineer and I don't trust the PSA method.  I do think Tifft et al. have
some interesting results and I'm sure a few theorists will start
working on the implications.  However, better tools for analyzing the data
do exist and I think it is important that they be used.  Especially since
the results are controversial.

Even the most careful methods can have underlying flaws.  Remember, last
Jan., Dr. Lyne had to retract his discovery of a planet around a pulsar.

Pat
From: ka1gt@cbnewsm.cb.att.com (robert.m.atkins)
Newsgroups: sci.astro
Subject: 2" Barlow wanted (1.25" Televue offered in part exchange): Genesis
Date: 7 Oct 92 16:08:08 GMT
Article-I.D.: cbnewsm.1992Oct7.160808.5969
Distribution: na
Organization: AT&T

I'm looking for a quality 2" barlow for photographic use with a TeleVue
Genesis. The TeleVue 2" would be great (though a bit expensive at $200+
for the amount of use it would get). I'd prefer something of fairly low
(1.5x, 1.8x) power if available. Does anyone have something like this they
would like to sell. I can offer a 1.25" 1.8x or 2.5x TeleVue barlow (both mint
condition) in part exchange. These are great barlows, but result in some
field vigneting (sp?) when used photographically. Visually they have
absolutely no problems. I'd be interested in comments on other 2" barlows
particularly if anyone has used them photographically with the Genesis.


===============================================================
Bob Atkins  AT&T Bell Labs  email (direct)  att!clockwise!rma
===============================================================
From: wats@scicom.AlphaCDC.COM (Bruce Watson)
Newsgroups: sci.astro
Subject: Meteoryite hits car in New York state
Date: 11 Oct 92 21:07:15 GMT
Organization: Alpha Science Computer Network, Denver, Co.

From an AP article in the Sunday Denver Post: Michelle Knapp, 18,
of Peekskill, NY, heard a loud crash, Friday, that shook the windows of her
house. Her 1980 Chevy Malibu had suffered a hole straight through the trunk. 
(Repo Man?) A small crater was seen in the ground underneath. The meteorite 
was still "pretty hot" and was found to weigh 30 lbs and measured about 
1 foot in diameter.

-- 
Bruce Watson (wats@scicom)  Tumbra, Zorkovick; Sparkula zoom krackadomando.  
Newsgroups: sci.astro,sci.physics
From: rwallace@unix1.tcd.ie (russell wallace)
Subject: Visual Effects of Relativistic Speed
Organization: Trinity College, Dublin
Date: Mon, 12 Oct 1992 13:37:10 GMT

What would be the visual effect of travelling very close to the speed of
light? I've seen a few conflicting ideas about what would happen;
currently, the best information I have is that the stars would appear to
move forward, so that at very close to lightspeed the rear hemisphere of
the field of vision would be totally black. Objects that were almost
directly behind will now be almost directly alongside, and massively
redshifted. Objects that were ahead will be massively blueshifted; at
sufficiently high speed, the cosmic background radiation ahead would be
blueshifted to visible light (though by this time, collision with
interstellar hydrogen atoms etc. would probably be lethal). Is this
correct, or am I missing something?

--
"To summarize the summary of the summary: people are a problem"
Russell Wallace, Trinity College, Dublin
rwallace@unix1.tcd.ie
From: greg@korg3.columbiasc.ncr.com (Greg Porr)
Newsgroups: sci.astro
Subject: Re: Meteor Showers ...
Date: 7 Oct 92 19:54:54 GMT
Distribution: world,local
Organization: NCR Corp, MCPD-Columbia, Columbia, SC

In article <6OCT92131247@tiamat.hacks.arizona.edu> omf@tiamat.hacks.arizona.edu writes:
>Hi all, I apologize if this is the wrong place to post this, but
>where can I get information on upcoming meteor showers?

Sky & Telescope magazine lists the showers each month, including such factors
as whether or not the moon might interfere.  The next major shower is the
Orionids, which, I think, start around the 20th of October.

Each year, the January issue includes a chart that lists various astronomical
phenomena for the entire year, including rising, transit and setting times
of the planets, sun, moon, and a few stars, as well as moon phases, meteor
shower peaks, etc.

I would guess that Astronomy magazine would also list major showers, though
I don't read it as much as S&T.  If you're interested in other aspects of
astronomy, I'd suggest trying both of these magazines to see which one
suits you better.

-- Greg Porr
   (Greg.Porr@ColumbiaSC.NCR.COM)
Newsgroups: sci.astro
From: moroney@ramblr.enet.dec.com
Subject: Re: What makes Fireballs green
Organization: Digital Equipment Corporation
Date: Wed, 14 Oct 1992 22:24:45 GMT

Barium, copper, boron and thallium are some elements that will be significantly
green when excited.  Do any of them occur in enough quantity to impart
their color to a meteor?  I don't think so.

-Mike
From: eramos@gmuvax.gmu.edu
Newsgroups: sci.astro
Subject: databases in astrophysics
Date: 10 Oct 92 11:58:10 -0500
Organization: George Mason University, Fairfax, VA.




Hi!

    My name is Elio Ramos and I am a graduate student in CSI/Institute (George Mason University). I am working in a Research paper for my Scientific Databases course. The topic that I'am working is Database requirements for astrophysical research specifically about the HEASARC facilities. I have the basic HEASARC 
documentation (Online user's guide, Available databases,etc). Also I have a 
copy of the "Legacy" Journal. Actually, I need information about the database
structures used by HEASARC. I checked the DOCUMENTS database but I don't know
where I can find this information. Also I want to know about current research 
topics in the development of the HEASARC facilities. Can you help me? I would
appreciate any recommendation. My postal adress is:
            
    Elio Ramos Colon.
    Institute for Computational Sciences and Informatics
    Room 116 Science and Tech.I Building
    George Mason University
    Fairfax,Va 22030
    
or better, REPLY this message.

thanks,
   
Elio Ramos
Organization: Johannes Kepler University Linz - Computing Center
Date: Wednesday, 14 Oct 1992 11:51:21 CET
From: Herbert Raab <K3032E0@ALIJKU11.BITNET>
Newsgroups: sci.astro
Subject: What makes Fireballs green
Distribution: na
 <1992Oct13.161237.10714@kakwa.ucs.ualberta.ca>

The light you see from a meteor is not really the meteoride burning up, it's
the ionized air. The green color comes from ionized oxygene (By the way, it's
the same what makes bright planetary nebulae look green).

Lots of clear nights, with many bright meteors & space-rocks coming down |

  Herbert Raab

>> K3032E0@ALIJKU11.BITNET << >> K3032E0@EDVZ.UNI-Linz.AC.AT <<
From: abian@iastate.edu (Alexander Abian)
Newsgroups: sci.astro
Subject: Re: Response to PUTTING VENUS IN AN ORBIT ... and TIME HAS INERTIA
Date: 11 Oct 92 20:59:11 GMT
Article-I.D.: pv343f.abian.718837151
Organization: Iowa State University, Ames IA

In <1b87ekINNcp7@roche.csl.sri.com> ronnie@cisco.com (Ronnie B. Kon) writes:

>In article <abian.718045416@pv343f.vincent.iastate.edu>, abian@iastate.edu (Alexander Abian) writes:
>|>    
>|>    My statements concerning PUTTING VENUS IN AN ORBIT SIMILAR TO THE ORBIT
>|> OF THE EARTH  and  TIME HAS INERTIA need no further elucidation, justifi-
>|> cation or proof.  They are explicit, self-explanatory and self-evident.
>|> 

>These are brilliant ideas, and you are absolutely right--they are so 
>obvious that your present postings have fully explained them.  Any 
>further postings on them would be entirely wasted: either people are
>open-minded and accept your conclusions, or they are close-minded and
>will just ridicule you (some more subtly than others).  Do not give
>into them.  Your time could be much better spent doing more research.
>Please resist the temptation to post more articles for the "guardians"
>of "truth" and "reality."

>You might wish to correspond with Hannu Kaarlo Juhani Poropudas
>(hporopudas@tnclus.tele.nokia.fi) whose posts strike me as demonstrating
>a kindred soul to yours.

   My comment to your advices  is:

              THE FEELING IS MUTUAL !
                                             Alexander Abian         

--------------------------------------------------------------------------

     THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION,OR THE PRESER-
     VATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE.  
                                                       C.Darwin (1859)    

     THE FUTURE OF SPECIES BY MEANS OF RATIONAL ALTERATION OF COSMOS, OR
     THE PRESERVATION OF INTELLIGENT RACES IN THE STRUGGLE FOR LIFE.
                                                        A. Abian (1992) 
Newsgroups: sci.astro,sci.geo.geology
From: cain@geomag.gly.fsu.edu (Joe Cain)
Subject: cratering
Followup-To: sci.astro
Organization: Florida State University Geology Dept.
Date: Sat, 10 Oct 92 14:27:17 GMT

I posted this to alt.sci.planetary and got zero response, so thought
maybe this group might.
***************

Students were asking me recently some questions about craters for
which I have only fuzzy answers. Could someone help?

1. What are the special type of craters seen on Mars called? Hartmann
refers to them as "rampart" craters, but other references seem to use
words like "petal," "pancake," and "pedestal" according to their
specific shape. I am looking for a generic term that describes all and
"rampart" does not seem to me to convey the nature of the
landform. I like the term "splosh" mentioned by Greeley more than
"fluidized ejecta", but wondered if the former caught on among the craterites.

2. Morrison and Owen indicate that an atmosphere might have played a
role in the form of Martian craters, but I have not seen this
mentioned elsewhere. Would an atmosphere not also imply a small size
cut off? I do not see any references to such a cutoff in the distributions. 

3. Morrison and Owen include the following table (9.2):

Relative cratering rates:

	Mercury	Venus	Earth	Moon	Mars
	2.0	1.0	1.5	1.0	2.0

with the footnote: the higher value for Mars is due primarily to its
proximity to the asteroid belt, while that of Mercury is as result of
the Sun's gravity.

This is the only reference I see to this, and Hartmann does not
mention this and I cannot fathom such from his comparative plots (pp.
327-335)
Is this difference in rates generally agreed upon?

	



Joseph Cain		cain@geomag.gly.fsu.edu
cain@fsu.bitnet		scri::cain
Newsgroups: sci.astro
From: sutherland@nssdca.gsfc.nasa.gov (Gary Sutherland)
Subject: Re: Astrophotography?
News-Software: VAX/VMS VNEWS 1.41    
Organization: NASA - Goddard Space Flight Center
Date: Thu, 8 Oct 1992 13:50:00 GMT

In article <1992Oct8.040749.10515@news.cs.indiana.edu>, vivek gupta <vigupta@tope.cs.indiana.edu> writes...
>Hi,
> 
>I am interested in taking various pictures of the moon, stars, and other planets. I am an amateur photographer and have been fascinated by the nite sky for quite some time. I was wondering what sort of equipment I would need to start.
> 
>I have a cannon T-70 camera, with long exposure (up to almost 24 hrs.) Since I will be doing this for personal pleasure and I don't have an enormous budget, what are some low cost telescopes and camera mounts, etc.
> 
>I am a novice, so please list all items I would need, so when I go calling around I can get total estimates.
> 
>Thanx in advance,
>Vivek GUpta
>vigupta@greatwhite.cs.indiana.edu

This is a very expensive hobby.  Your best bet is to join a local 
Amateur Astronomy club for advice.  When looking for a telescope, try 
to buy a used one first.  Many people buy them for loved ones at 
Christmas then the telescopes end up on the market 9 months later.  
You will need a clock drive on an equatorial mount if you plan on 
photographing anything more than the Moon and bright planets.  A good 
source of information is Astronomy Magazine or Sky & Telescope 
Magazine.  Good Luck, and keep us posted with your success.
From: jordan@warped.pnl.gov (Randy Jordan)
Newsgroups: sci.astro
Subject: Re: Radio Telescopes
Date: 15 Oct 92 18:54:20 GMT
Article-I.D.: oracle.1992Oct15.185420.9734
Reply-To: jordan@warped.pnl.gov (Randy Jordan)
Organization: Battelle, Pacific Northwest Laboratory


In article <1992Oct15.155626.28515@bcars6a8.bnr.ca>, mleech@bnr.ca (Marcus Leech) writes:
|>Path: pnl-oracle!ogicse!usenet.coe.montana.edu!uakari.primate.wisc.edu!sdd.hp.com!cs.utexas.edu!torn!cunews!nrcnet0!bnrgate!bcars6a8!bnr.ca!mleech
|>From: mleech@bnr.ca (Marcus Leech)
|>Newsgroups: sci.astro
|>Subject: Re: Radio Telescopes
|>Message-ID: <1992Oct15.155626.28515@bcars6a8.bnr.ca>
|>Date: Thu, 15 Oct 92 08:56:26 GMT+8:00
|>Article-I.D.: bcars6a8.1992Oct15.155626.28515
|>References: <1992Oct8.105453.10254@bsu-ucs.uucp>
|>Sender: usenet@bcars6a8.bnr.ca (Use Net)
|>Organization: Bell-Northern Research, Information Techology Division
|>Lines: 29
|>Nntp-Posting-Host: bcarh1ea
|>
|>In article <1992Oct8.105453.10254@bsu-ucs.uucp>, 00csriggle@bsu-ucs.uucp writes:
|>|> Hi... Me and some other people are attempting to build a "minor" radio
|>|> telescope. Just wondering if anyone had ideas on whether to get a shortwave
|>|> from someone or to build one ourselves? If it's a good idea to buy one, is
|>|> there a good place to get one?
|>|> 
--
	If it helps the DoE/Battelle Pacific Nortwest Laboratories is going
	to 'Excess' a 30 ft radiotelescope and it's equipment. You might
	inquire of them, what they want for it.
RJ

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	To Thyne Own Self be true...
	                             myne opinions are.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From: steve_olson@npd.novell.com
Newsgroups: sci.astro
Subject: Diesen sphere or Strungen Sphere
Date: 12 Oct 92 16:55:24 GMT
Reply-To: steve_olson@npd.novell.com
Organization: Novell, Inc.

Does anyone know any thing about a Diesen sphere or a Strungen Sphere? 
It is supposed to be a sphere with a star in the middle. 

I first saw it on Star Trek, you should see it in this weeks episode, I saw 
the sattelite feed on Sunday.  Our local university astronomer told me that
the sphere is actually called the strungen sphere, but on ST they refer to
it as a Diesen Sphere.

Steveo
From: oler@rho.uleth.ca (Cary Oler)
Subject: Daily Solar Geophysical Data Broadcast for 14 October
Organization: University of Lethbridge
Date: 15 Oct 92 18:46:20 GMT

!!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 288, 10/14/92
10.7 FLUX=105.5  90-AVG=118        SSN=067      BKI=2333 2235  BAI=016
BGND-XRAY=B2.5     FLU1=4.6E+05  FLU10=9.6E+03  PKI=3333 3235  PAI=016
  BOU-DEV=015,024,029,029,019,015,025,094   DEV-AVG=031 NT     SWF=00:000
 XRAY-MAX= C9.9   @ 1935UT    XRAY-MIN= B1.1   @ 2353UT   XRAY-AVG= B5.6
NEUTN-MAX= +001%  @ 2310UT   NEUTN-MIN= -003%  @ 1105UT  NEUTN-AVG= -0.5%
  PCA-MAX= -2.9DB @ 0535UT     PCA-MIN= -3.6DB @ 1935UT    PCA-AVG= -3.1DB
BOUTF-MAX=55430NT @ 0336UT   BOUTF-MIN=55399NT @ 1702UT  BOUTF-AVG=55419NT
GOES7-MAX=P:+145NT@ 1946UT   GOES7-MIN=N:-014NT@ 2348UT  G7-AVG=+080,+036,+011
GOES6-MAX=P:+146NT@ 1946UT   GOES6-MIN=E:-024NT@ 1716UT  G6-AVG=+088,-014,+029
 FLUXFCST=STD:100,105,107;SESC:105,105,110 BAI/PAI-FCST=020,010,010/025,020,020
    KFCST=3344 4453 3333 3333  27DAY-AP=076,026   27DAY-KP=5677 5455 4545 4333
 WARNINGS=*SWF
   ALERTS=
!!END-DATA!!
From: wats@scicom.AlphaCDC.COM (Bruce Watson)
Newsgroups: sci.astro
Subject: Re: How bright is the Hubble Space Telescope?
Date: 15 Oct 92 18:07:27 GMT
Distribution: na
Organization: Alpha Science Computer Network, Denver, Co.

In article <1992Oct14.154305.1@stsci.edu| hamilton@stsci.edu writes:
|I was wondering how bright HST is when it passes near the zenith. I've seen HST
|numerous times from here in Maryland, but its maximum elevation is only ~20
|degrees.  On one rare occassion, it flared up to ~ -2 while on vacation back in
|Indiana, but it is usually ~ 3rd to 4th magnitude. 

Like you, I've observed HST from about 40N a number of times and while it
is commonly mag +3 (when visible) it has flared to +1 and 0. Seasat's
behavior is similar. The one time I saw it nearly overhead was in Cabo
San Lucas in July of 1991 it was a steady +2. I hope observers participate.
Light variation of the telescope (and other satellites of similar
architecture) is very interesting.

-- 
Bruce Watson (wats@scicom)  Tumbra, Zorkovick; Sparkula zoom krackadomando.
From: j.jahn@abbs.hanse.de (Jost Jahn)
Newsgroups: sci.astro
Subject: Sunspots at 15.10.1992.
Reply-To: j.jahn@abbs.hanse.de
Date: 15 Oct 92 22:39:00 MET
Distribution: sci
Organization: ABBS AstroMail, D-W 2121 Dahlenburg / Germany
X-Version: ZerUU V6.45c

Sunspots at 15.10.1992., 0 h UT.

No.    Pos.  Cl.  Ar.  Mag. SF  F  M  X
---------------------------------------
7306 08S 71W Hsx   30   a
7309 16S 38W Bxo   10   b
7310 07N 38E Cro   40   b    1
7311 17S 45E Cso   40   b
7312 20N 68E Hsx   30   a


No optical or x-ray flares yesterday observed.


 
--
------------------------------------------------------------------------------
ABBS AstroMail, the first and most popular German astronomical bulletin board
------------------------- 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: F1.DAO@isumvs.iastate.edu (David Oesper)
Subject: University Optics Filter Wheel
Organization: Iowa State University, Ames IA
Date: Thu, 15 Oct 1992 04:57:38 GMT

Thanks to Michael Edelman's answer to my question on filter wheels,
I was able to purchase an eight-position filter wheel for 1.25"
filters from University Optics for $129 (too expensive!).  I have
received the filter wheel and had a chance to use it several times.
Overall, I am very pleased with it.  The only drawbacks are (1) the
price, (2) it is made of low-grade plastic, (3) the filter wheel is
open to the elements around the perimeter, and (4) the wheel doesn't
have a good mechanical locking mechanism for each filter position --
you have to do it visually.  These are all rather minor criticisms,
however.  I called Lumicon the other day inquiring about their
nebula filters, and mentioned to them that they ought to offer a
filter wheel for their nebula filters.  They told me they are
working on one that will be made of better materials than the
University Optics filter, but that it is not available yet.

Just for fun, I took a look at Albireo using the filter wheel the
other night and noticed a strange phenomenon which I can't explain.
Using a Schmidt-Cassegrain and a 45-degree prism diagonal, I put the
red filter in and focus the stars as well as seeing will permit.
Then running through the orange, yellow, and green filters I get to
the blue filter and find I have to focus in the NEAR direction to
achieve focus in blue light.  The difference between the red and
blue filter focus points is very small.  The polarizing filter I
have focuses in between the red and blue filter focus points (not
surprising).  The real surprise comes when I rotate the filter wheel
to the open (i.e. no filter) position.  Now the image is grossly out
of focus!  I have to focus in the FAR direction relative to the red
filter in-focus position to achieve focus.  Anybody want to hazard a
guess as to what is going on here???

Thanks,

David Oesper  (S Per)
Ames Area Amateur Astronomers
Ames, Iowa
Newsgroups: sci.astro