The AstroSpotter Device The Easy Way To Find The Stars!
The
AstroSpotter is a
fairly simple device that eliminates the frustration experienced by
people trying to use a small flat star chart to find stars in the very
large spherical night sky. It would serve as an outstanding
astronomy teaching aid and my hope is that people will be able to use
AstroSpotter to make star finding as well as star identification as
easy as possible. These
days with digital phone/devices there are programs to point out parts
of the sky whereas this was invented before those devices existed so it
is 'Old Skewl' approach. If nothing else this device will help
people visualize the way the coordinates of the heavens are laid out
and maybe help to explain the dynamic way the stars move over the night
as well as from season to season. The AstroSpotter makes a great tool for the beginner, the student, as well as advanced binocular watchers of the night sky. The functionality of AstroSpotter can also be had with equatorial telescope mounts but that sort of hardware can easily be far out of the financial reach of the casual star-gazer or student who is just starting out in star gazing.
Picture 1: The AstroSpotter I invented AstroSpotter because all the other devices that try to do this job either cost a bundle or just get beginers frustrated when they finally try to go out at night and try to find stars from documents or devices. Once the AstroSpotter is aligned, stars and constellations are easy to spot given their coordinates taken from any number of references listed in the reference section of this web page. This device is greatly enhanced if you use it with a green laser pointer. Please note that in some places laser pointers are illegal and you must obey applicable laws. Also note that at a serious astronomy star party it is highly discouraged and often not allowed to use a green laser pointer because you may ruin photographs in progress at that time or perhaps just agrivate those around you at the time. The AstroSpotter device is made to attach to a standard camera tripod in order to hold it steady on the north star. Because this tool requires allignment with the north star, the AstroSpotter device is only useful for the northern celestial hemasphere viewable from the United States and most of Europe. The AstroSpotter is not being sold here at this time so you need to be a bit of a do-it-yourselfer in order to get one of these devices at this time. And oh yes ... the legal stuff: All rights to the AstroSpotter belong to the original designer and cannot be used for profit without permission from myself, Mark E. Johnston, in writing.
How
To Align AstroSpotter (Simplified
Method) For star gazers who know where the
north
star is and who know how to figure
out their local sidereal time, the basic idea to align the AstroSpotter
is as
follows. 1) Secure the AstroSpotter to
a camera tripod and point it directly at
the north star by either sighting the north star along the top of the
fin or by
sighting the north star through the middle of the plastic pipe that the
fin is
attached to. 2)
Assure that
the very top of the large dial on the AstroSpotter
always
indicates the correct local sidereal time.
Re-adjustment of the dial
every 5 minutes or so using a little turn of the big dial will do the
trick
nicely. If the sidereal time is 11:00
then adjust the dial so
11:00 is at the top of the dial. You may find it handy to have a
second watch set to sidereal time along when you use the
AstroSpotter. Please see the References section for a
website with sidereal time or your astronomy program usually will tell
you your current sidereal time (Which is the current Right
Ascension directly above your head at any given time. You may
proceed to using
the
AstroSpotter now if you wish. Detailed Description of how to setup
the
AstroSpotter: The baseplate can be attached to a
standard camera tripod using the mounting
hole and a standard 1/4 20 tripod mounting screw. The north star must
be visible
if very precise measurements are to be done and this description will
only
explain how to use the device when the north star is visible. If you
know how to
find the north star skip the next paragraph. Parts Of The AstroSpotter
To align the AstroSpotter,
it is first important to get the north star to be
pointed to through the hole in the middle of the axis
tube. Or sight
the north star along the top of the big fin that holds the two star
pointers. The axis tubes are
aligned to point to the north star by sighting the north star along the
top edge of the sighting fin when the fin is in a vertical position. In
general, this will be good enough to do plenty of good star gazing. If
even better alignment is desired, a little practice will allow the
north star to be centered directly through the axis tubes once the
rough alignment has been done using the sighting fin. Hint: Stay back a
foot or so from AstroSpotter and keep your focus point at infinity as
you sight through the tube. The only error here is you will sight about
4" away from the center of the north star, but that should be fine
( joke ). After sighting the North
star along the top of the fin, The disk with the
scale for right ascension should then be aligned. IF YOU KNOW
YOUR
SIDEREAL TIME ROTATE THE DISK SO CURRENT SIDEREAL TIME
POINTS UP AND MOVE RIGHT AHEAD TO using
AstroSpotter. Move the fin to align with
your correct LOCAL time. Local time varies from the time on your watch
by as much as an hour so see the AstroSpotter
fin or earlier section 'Your Local Time' for an explanation. If it is
not possible to align the fin to local time because the fin does not go
that far, move the fin to align with 12 hours ahead of the correct time
of day and remember this trick for later. A Quick Review of basic setup of the AstroSpotter: 1) Secure the AstroSpotter to a camera tripod and point it directly at the north star by either sighting the north star along the top of the fin or by sighting the north star through the middle of the plastic pipe that the fin is attached to. 2) Assure that the very top of the large dial on the AstroSpotter always indicates the correct local sidereal time. Re-adjustment of the dial every 10 minutes using a little turn of the big dial will do the trick nicely. Locating
A Star With Known Celestial Coordinates
The Figure below shows
the sighting of a typical star of
interest. After
aligning the device as stated above, rotate the sighting fin to align
with the
right ascension of the star as shown on the disk. Then set the pointer
on the
declination scale to align with the correct declination of the star or
constellation. This star is at a right ascension of about 3 hours and
at about
+40 degrees (This is the star Algol which is visible in winter) Typical Sighting Of A Star The scale closest to the clear ascension disk is useful for stars just above the north star that would be difficult to sight using the other scale due to the position of the tripod that the AstroSpotter is mounted upon. For some stars that are within +40 degrees to +90 degrees and are below the north star, the sighting fin will not rotate to the correct right ascension because the mounting plate gets in the way. The figure below shows the way in which the AstroSpotter pointer can be used in reverse to sight such stars. For these stars, the extra scale on the full 180 degree scale can be used to sight the star along the pointer in a reverse manner. Sighting A Star Below The North Star
Using AstroSpotter To Identify A Star The other great use for the star AstroSpotter is to identify interesting stars or constellations that may be noticed while gazing at stars. Here the idea is to twist the sighting fin and turn the pointer on the declination scale so that the pointer is pointing right at the star or Constellation in question. Once this has been done, simply read off the right ascension from the disk and read off the degrees of declination from the scale on the sighting fin. After doing this, consult your planisphere or The Field Guide To The Stars And Planets (See References at the end of this paper) to determine the identity of the star or constellation. Keep in mind that the AstroSpotter must be aligned first and the right ascension disk must be updated if the readings are to give correct ascension. Making Your Own AstroSpotter Device
If
you wish to make an AstroSpotter device and
would like better directions on making
one or some sort of kit of parts to be offered, let me know and perhaps
if it
seems a big enough need, I can figure out some way of getting some sort
of parts
kit together. It is ok for an individual to make his or her
own AstroSpotter
for personal use. I have in my garage a lot of the required
parts that are available on the cheap. Contact me via the email
on the about me page. It would be wrong and unjust to take
this
idea and
profit from it without contacting me and reaching an
agreement. The parts used in an AstroSpotter device are all available in one way or another but it took me personally months to figure out just how and where to get all the parts that both look and fit nicely together. The process went through at least 4 versions of the AstroSpotter and ended up in what is described in these web pages. It is my hope to help folks enjoy an AstroSpotter on their own but for now only the basic idea of my design is shown below. Once again this idea is ok for individuals to use to make their own AstroSpotter to use for themselves or explaining the night skie to others such as school situations.
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