star tracking...
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Hi all,
I'm looking at a telescope and some way to follow a star.
I know there are ways to calculate where the stars should be, but
that does not allow for Earths rotation. A second point that is
roughly 90 degrees from the object is preferred to 'derotate' the
telescope so the photos are no those swirl of stars one often sees.
So... anybody know a way to 'see' a star and then follow it ? I'm
thinking a small telescope with a CCED camera and then someway to
keep that point of reference in the center.
Dave
I'm looking at a telescope and some way to follow a star.
I know there are ways to calculate where the stars should be, but
that does not allow for Earths rotation. A second point that is
roughly 90 degrees from the object is preferred to 'derotate' the
telescope so the photos are no those swirl of stars one often sees.
So... anybody know a way to 'see' a star and then follow it ? I'm
thinking a small telescope with a CCED camera and then someway to
keep that point of reference in the center.
Dave
Comments
a database of about 5,000 objects and have the 'scope lock on it forever.
With a GPS receiver, built in, you do not even have to align your 'scope
with Polaris.
I am sure this device would cost far less than the time and expense of
trying to the same thing with a stamp, stepper motors, etc.
Rick
Original Message
From: "Dave Mucha" <davemucha@j...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, January 24, 2004 12:21 PM
Subject: [noparse][[/noparse]basicstamps] star tracking...
> Hi all,
>
> I'm looking at a telescope and some way to follow a star.
>
> I know there are ways to calculate where the stars should be, but
> that does not allow for Earths rotation. A second point that is
> roughly 90 degrees from the object is preferred to 'derotate' the
> telescope so the photos are no those swirl of stars one often sees.
>
> So... anybody know a way to 'see' a star and then follow it ? I'm
> thinking a small telescope with a CCED camera and then someway to
> keep that point of reference in the center.
>
> Dave
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
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>
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>
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>
>
All you need is two motors, preferably stepper motors,
one for right ascension (left to right, or East to
West horizon) and declination (above and below the
horizon, North to South horizon) and your telesope
mounted to those motors on a good, solid, sturdy
telesope tripod. of course, these can be bought in
many stores ot mail ordered from the various astronomy
magazines. Mead and Celestron are the two best that
come to mind. There are others, too, but be careful
of the scopes sold in the department stores as they
are cheap.
As the commercial telescope drive systems do, you
align the whole system with the North star. Once that
is done, since the Earth rotates at a fixed rate, or
in other words, the stars move from East to West and
appear to rise above and fall below the Southern
horizon in the field of view.
Also, the more sophisticated drives even have the
ability to store star coordinates (R.A. and Decl -
Right ascension and declination) in the computer or
controller and then you can punch in the star and
voila...the desired star appears in the field of view.
The key to the whole system to maintain the accuracy
is to have the drives and scope aligned with the north
star, which is at the center of the field of rotation
(or above the North pole.)
Might want to to a google search for telescope drives,
even check out the various Astronomy magazines for
information.
Hope this helps or at least gives you some ideas of
where to look for this information.
Thanks and have a great day!
James E. Merritt
--- Dave Mucha <davemucha@j...> wrote:
> Hi all,
>
> I'm looking at a telescope and some way to follow a
> star.
>
> I know there are ways to calculate where the stars
> should be, but
> that does not allow for Earths rotation. A second
> point that is
> roughly 90 degrees from the object is preferred to
> 'derotate' the
> telescope so the photos are no those swirl of stars
> one often sees.
>
> So... anybody know a way to 'see' a star and then
> follow it ? I'm
> thinking a small telescope with a CCED camera and
> then someway to
> keep that point of reference in the center.
>
> Dave
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed.
> Text in the Subject and Body of the message will be
> ignored.
>
>
> Yahoo! Groups Links
>
> To visit your group on the web, go to:
> http://groups.yahoo.com/group/basicstamps/
>
> To unsubscribe from this group, send an email to:
> basicstamps-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject to:
> http://docs.yahoo.com/info/terms/
>
>
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<wb3csy@e...> wrote:
> It's called a clock drive. They are so good, you can call up an
object from
> a database of about 5,000 objects and have the 'scope lock on it
forever.
> With a GPS receiver, built in, you do not even have to align
your 'scope
> with Polaris.
>
> I am sure this device would cost far less than the time and expense
of
> trying to the same thing with a stamp, stepper motors, etc.
>
> Rick
Actually it's called a de-rotator. The clock drive will keep the
star in the scope as the panet moves and the star appears to be
moving.
The problem is that the Earth rotates and the telescope also rotates
360 degrees. Imagine sitting on a Merry-go-round. If you were to
put an object about it, say a tree branch, you will see that in
relation to your point of view so that as you spin, the branch
appears to spin. If you were to take a time lapse photo, you would
get on point on the branch that was an axis, and everything else
would be a large blurring swirl.
IF, however, you were to pick a point, say the trunk of a tree and
made sure your 90deg was rotated opposite to your rotation, so that
trunk was always on the relationship to your camera, then and only
then would the branch appear not to move in the time lapse photo.
What I need to do to get this is to lock on to that 'tree trunk' that
is 90 degrees off my star.
I need to be able to see a star as reference and then figure a way to
use that as the means of generating control signals to de-rotate the
tube of the telescope.
The star drives will correct for elevation and azimuth, but the 3rd
thing is missing.
Dave
>
Original Message
> From: "Dave Mucha" <davemucha@j...>
> To: <basicstamps@yahoogroups.com>
> Sent: Saturday, January 24, 2004 12:21 PM
> Subject: [noparse][[/noparse]basicstamps] star tracking...
>
>
> > Hi all,
> >
> > I'm looking at a telescope and some way to follow a star.
> >
> > I know there are ways to calculate where the stars should be, but
> > that does not allow for Earths rotation. A second point that is
> > roughly 90 degrees from the object is preferred to 'derotate' the
> > telescope so the photos are no those swirl of stars one often
sees.
> >
> > So... anybody know a way to 'see' a star and then follow it ? I'm
> > thinking a small telescope with a CCED camera and then someway to
> > keep that point of reference in the center.
> >
> > Dave
> >
> >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
> >
> >
> > Yahoo! Groups Links
> >
> > To visit your group on the web, go to:
> > http://groups.yahoo.com/group/basicstamps/
> >
> > To unsubscribe from this group, send an email to:
> > basicstamps-unsubscribe@yahoogroups.com
> >
> > Your use of Yahoo! Groups is subject to:
> > http://docs.yahoo.com/info/terms/
> >
> >
There are two common astronomical telescope mounting systems. El over
Az and Polar.
In an El/Az mount the lower motion points the scope in azimuth (0 to 360
degrees) and the upper motion sets the elevation (-90 to +90 degrees).
This type of mount costs less to build than a Polar mount and is used
with very large telescopes. The image rotates as the mount tracks a
star and a de rotator is needed if taking time exposure images. Because
of the finite time it takes to rotate 180 degrees the scope can not
point to within some number of degrees of straight up.
In a Polar mount there is an axle pointing at the North celestial pole
(very near the North star). Movement around this axle is called Right
Ascension and is in terms of sidereal time (00:00 to 24:00). The other
axle is at right angles to the R.A. axle and is called the declination
axis (-90 ti +90 degrees). Once the declination axis is set to point to
a star then a simple clock drive rotating the scope about the polar
(R.A.) axis will de spin the Earth's rotation and allow time exposures.
There is no field rotation. The common types of Polar mounts are the
Schmidt Cassegrain Telescope (SCT) fork mount and the German Equatorial
mount.
The key is the filed of view of the camera and how long you want to
expose. A normal camera mounted to a Polar mount, typically piggybacked
on the main telescope, can have an exposure time of say an hour. If you
are photographing trough the telescope at high power maybe only a minute
or two is all that can be done before errors in the mount cause
streaking or blurring of the image. For high power exposures over long
times you need mounts that are very good (read $ 10,000 and way more)
and/or active guiding, either manually using a guide scope or
automatically using a TV camera or specialized camera that has tracking
correction capability.
Without more details from you I can't go deeper.
Have Fun,
Brooke Clarke, N6GCE
http://www.PRC68.com
>Date: Sat, 24 Jan 2004 17:21:29 -0000
> From: "Dave Mucha" <davemucha@j...>
>Subject: star tracking...
>
>Hi all,
>
>I'm looking at a telescope and some way to follow a star.
>
>I know there are ways to calculate where the stars should be, but
>that does not allow for Earths rotation. A second point that is
>roughly 90 degrees from the object is preferred to 'derotate' the
>telescope so the photos are no those swirl of stars one often sees.
>
>So... anybody know a way to 'see' a star and then follow it ? I'm
>thinking a small telescope with a CCED camera and then someway to
>keep that point of reference in the center.
>
>Dave
>
>
>
>
> So... anybody know a way to 'see' a star and then follow it ? I'm
> thinking a small telescope with a CCED camera and then someway to
> keep that point of reference in the center.
Dave, google for "barn door tracker". You should get a lot of
hits on various homebrew trackers that are simple and very easy
to build using a simple stepper motor from old floppies, etc.
And they're incredibly accurate for the simple technology
involved. You could build one for about $10.
Michael