Amateur astronomy equipment, techniques, info, etc

Archive for February, 2010

AstroNet: attention recent subscribers.

We unfortunately must report that we had a disk crash and have lost the
e-mail addresses of those subscribers who signed-up between October 9 and
approximately the 26th.

If you have recently subscribed to AstroNet’s Astronomy Digest and do not
receive delivery of the publication (or notification of a new issue) next
Wednesday (November 1), please e-mail us and ask for the ASTRONET.TXT file
again, so you may re-subscribe.

Sorry for any inconvenience.  All subscribers prior to October 9 can
disregard this information.

Clear skies!

Mark Wagner


  |   A s t r o N e t    O n – L i n e   A s t r o n o m y   D i g e s t   |

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Re: Telrad problems

stri…@salzo.Cary.NC.US (B.J. Holt) wrote:
>I have recently purchased as my first "real" telescope an 8" Orion Dob
>with a Telrad. The Telrad however had no instructions on how to attach it
>to the scope. It seems no matter where I place the Telrad on the scope
>the centered object is always on the lower edge of the outside ring. How
>do I get the Telrad properly alligned? Also when the finder is on the
>scope the scope becomes very top heavy. How can I correct this. Any help
>would be much appreiciated from a struggling beginner. Thanks.

   Did your Tel Rad not come with sticky foam along the base?  Older
versions came with gray twine.
   Select a spot on your scope that you can get at from every postion
that you will point your scope and that affords the most comfortable
view with the least amount of motion away from the eyepiece.  Peel of
the sticky tape and apply the base.  If you have the older version,
firmly tie down the base with the provided twine.  (In fact, I would
recommend doing this anyway so that you can decide whether you like
the position that you have picked.)  The easiest star to centre your
Tel Rad on is Polaris as it will stay put while you twiddle knobs,
however, any star will do.  Centre your scope on the star.  Look
through the Tel Rad and adjust the three small nuts on the back of the
Tel Rad, directly beneath the spot you look into.  These nuts are
attached to a mirror inside the body of the Tel Rad and this is how
you centre a star.  Once the star is in the exact centre of the
smallest ring, check to see if the star is still centred in your
scope.  Repeat if necessary.  Unless you permanently affix your Tel
Rad base, you will have to check this each time you set up your scope.
I highly recommend buying nuts and bolts of the correct size and
length to bolt the base to your tube once you have found the position
that you like.
   Since once you get used to your Tel Rad, you will likely not need
your finder scope, you can remove it and that should restore the
   If you still cannot balance your scope, what I have done in the
past with Dobsonians is attach a piece of sticky backed velcro to the
mirror end of the scope.  Then I sew small bags with the other side of
the velcro on them that can be filled with lead shot.  Stick the bag
on to balance.  Since a very heavy ocular can also overbalance your
scope, you may need a few different bags for different balance
   Clear skies!

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Re: Black night sky

Mike Maier <…> wrote:
> I read the info on blue skies, which I already know.
> My problem is the following: Why is the night sky black?
> I’ve heard of a paradoxon that says that each point of the night sky
> should be as brilliant as our own sun (of course the day sky would
> appear the same). The reason for this – if I remember correctly – is
> that every point of our sky would recieve exactly on ray of a sun at
> some enormous distance…

> So, who knows, why its not so?

This is called Olbers’ paradox. The current theory has two explanations:

1) The universe is expanding, so stars (galaxies) far away move away
   from us. This means that the photons we receive from these distant
   stars have longer wavelengths (“Doppler effect”), thus less energy.
   Another effect of the expanding universe is the following: we don’t
   receive energy from distant stars at the same rate as they send it
   out, since energy is piling up in photons in the space between us and
   the star: this space increases, thus more and more energy is piling
   up there.

2) Universe has existed only for a finite time. Photons from very
   very far away have not reached us yet.

If you want a more detailed explanation, please ask in sci.astro, this
newsgroup is avoiding topics of “cosmological” nature.

Cheers — Harald

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Re: Why didn't I see de

Jim.Van.Nul… (Jim Van Nuland) wrote

>   There is a mnemonic that can help:  find the arc of the handle
>   of the Big Dipper, and ARC to Arcturus.

>   Then if it’s not to low in the sky, you can (continue) speed on
>   to Spica.

>   My thanks to Jay Freeman for this useful device.

My thanks to both of you; I don’t think I’ll ever call Arcturus
‘Antares’ again. BTW, Paul Schlyter directed me to a reasonably dark
site in Stockholm, and I finally saw deVico tonight, but it was tougher
than I had anticipated (10×42 binoc’s). But M3 was lost in the haze, so
the conditions weren’t great. To my amazement, M81/82 were easier to
see than deVico, but better located of course. Still, I didn’t think it
was possible to see M81/82 from *within Stockholm* in small binoc’s.

Cheers — Harald

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Any Refractor review FAQ's??

 Are there any good reviews that compare the various refractors made
by the different companies?  I’d like to see what people think of
different models of 4 and 5" refractors and how they might compare.

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FS: 18" Sky Designs Dob – Galaxy Optics

I have a Sky Designs 18" VPT Dobsonian for sale.  ALL optics are by
Galaxy Optics and are simply superb.  Many extras as well.  Will sell
for $2300 plus shipping.  I am selling it to get something smaller and
more portable.
  E-mail if interested.

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Re: ATMing and old cars

> Any thoughts on what kinds of ATM-parts can be salvaged from an old car?

    o Hood ornaments:  Just the thing for telescopes which have nothing else
      to recommend them, thus in wide demand.  Also handy as peep sights.
    o Glove compartments:  Useful place to store star charts, eyepieces
      and Oreos.  Caution:  Only glove compartments from armored vehicles
      are raccoon-proof for more than 0.3 second.
    o Tachometers:  Every telescope should have a tachometer for each of
      its axes of rotation.  Automobile tachometers will give a highly
      accurate reading most of the time, even when not hooked up.
    o Fuel gages:  Ditto.
    o Windshield wipers:  For observing in heavy dew or rain.
    o Headlights, high beam:  Save for retaliation against non-recycled
      automobiles driving through your observing site with lights at
      bolometric luminosity approximating the sun.  The naive and the
      gentle may wish to save low beams as well, on the possibility that
      flicking your telescope’s lights back and forth from high to low
      will induce automobilists to reduce unwanted illumination.
    o Backup lights:  Required by law in most localities when tracking
      solar system bodies in retrograde motion.
    o Rear-view mirrors:  Permit looking for objects below the horizon
      without turning your telescope upside-down.
    o Bumpers and fenders:  Useful in territorial disputes with other
      amateur astronomers over prime observing sites.
    o Gear-shift knobs and levers:  A nice shifter sticking out of the
      mechanism of your sidereal drive will impress all your friends at
      the next star party, particularly if you affix near its attach
      point a small placard bearing the text "hyperdrive", and modify
      your tachometer (see above) to read out in warp factor.

   Jay Reynolds Freeman — free… — I speak only for myself.

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Off axis guider/reticle eyepiece for 8" SCT

Hi there,

I have an 8" SCT and am planning to try some prime focus photography
in the near future.  I’m seeking advice from those who’s had
experience with offaxis guiders and guiding eyepieces.  What guider
and eyepiece do you recommend?  I’m currently leaning towards the
Celestron radial guider and possibly a 9mm eyepiece.  Do you think
the 9mm is powerful enough?



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Truckload of Planets!


This is probably obvious to most readers of this group, but
just in case you haven’t been paying attention…

Lined up from west to east tonight just after sunset were
Venus, Mars, Jupiter, the Moon, and Saturn, big and bright
as life!  Uranus and Neptune were lurking somewhere between
the Moon and Jupiter, too, if you knew where to look…

This parade will continue for the next month or so, so keep
looking up!  (To coin a phrase.)

e ho’ole’ale’a

Richard Stueven    g…

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Deep Observing M31

Its prime season for observing M31, and instead of just the 5 minute
"look" , try some of these projects:

1) Observing the angular extent of this galaxy. Scopes best suited for
this are rich-field, though binoculars and even your eyes are suitable.
Under reasonably dark Georgian skies, I’ve seen M31 extend almost  3.5
degrees in my 6" f/5.

2) Trace out the extent of the dust lanes. This goes beyond just observing
them, instead see how far around can you seen the 2 main dust lanes. This
is something I’m going to try with the 6 and 20" scopes.

3) Observe the numerous globular clusters. Sky and Telescope (Nov, 1995)
gives directions to finding G1 (brightest globular), while Luginbuhl and
Skiff’s Observing Handbook of Deep Sky objects and articles in Deep Sky
also give instructions/maps to finding these objects.

4) Here’s an "unusual" challenge: try to resolve the brightest stars
in NGC 206 (star cloud in M31). This is no joke, you can resolve the
brightest members (>= 15th mag). I have done this with our club’s 20",
and so has Roger Venerable of Augusta, Ga (independent of my observations)
You will need a large scope, excellent conditions (seeing AND transparency)
plus > 20x per inch for maximum contrast and sky darkness.

..if you know of other interesting projects like this, or would like to
share them with others – please do!

- Rich Jakiel

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