can someone give me some info about trackers, please?

Hi all,

Honestly, I know very little about this filed of astronomy, and that's
why I need your help. My research involves an new instrument
that is supposed to point the center of the sun disk to measure solar
beam at a certain spectrum. Since our instrument has a 1-degree field
of view only, I need a tracker to accurately track the sun at least
within 0.1 degree. I heard that amateur astronomers use very accurate
trackers to track stars. Could anyone give me some information about
it? Any guidance you can provide would be greatly appreciated.

Christine

An equatorial camera mount might suit your needs
http://www.scsastro.co.uk/cg170001.htm


wrote in message
oups.com...
Hi all,

Honestly, I know very little about this filed of astronomy, and that's
why I need your help. My research involves an new instrument
that is supposed to point the center of the sun disk to measure solar
beam at a certain spectrum. Since our instrument has a 1-degree field
of view only, I need a tracker to accurately track the sun at least
within 0.1 degree. I heard that amateur astronomers use very accurate
trackers to track stars. Could anyone give me some information about
it? Any guidance you can provide would be greatly appreciated.

Christine

"john carruthers" wrote in message
...
An equatorial camera mount might suit your needs
http://www.scsastro.co.uk/cg170001.htm



I can recommend the Paramount ME at the top of the page and when you have
finished with it for your research, I know someone who would take it off
your hands ;-)

Robin

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Robin Leadbeater
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
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"john carruthers" wrote in message
...
An equatorial camera mount might suit your needs
http://www.scsastro.co.uk/cg170001.htm


wrote in message
oups.com...
Hi all,

Honestly, I know very little about this filed of astronomy, and that's
why I need your help. My research involves an new instrument
that is supposed to point the center of the sun disk to measure solar
beam at a certain spectrum. Since our instrument has a 1-degree field
of view only, I need a tracker to accurately track the sun at least
within 0.1 degree. I heard that amateur astronomers use very accurate
trackers to track stars. Could anyone give me some information about
it? Any guidance you can provide would be greatly appreciated.

Christine
There are two different things involved here, and you perhaps need to
think about which part of the approaches available, you need. Any
reasonable polar aligned mount (by this we mean a mount, where one of the
rotational axes, is 'parallel' to the polar axis of the Earth, can be made
to follow the movement of the stars, to an accuracy, limited only really
by the gears involved, and the accuracy of the polar alignment. The rate
has to be modified near the horizon, to allow for the atmospheric
refraction. The Sun is slightly harder, since it moves up and down in the
sky through the year, and moves at a slightly different rate 'across' the
sky. Such 'mounts', have gearboxes, whose accuracy, depends on how much
you are prepared to pay, and the price also varies massively, with the
load that the unit has to carry. Typically,a unit may have a
repeatability, better than an arc minute, a basic 'movement', able to work
to tiny fractions of an arc second, and an overall 'accuracy', to a small
fraction of a degree. If you build a suitable mathematical model of where
the Sun is expected to be, any such mount, with a 'goto' ability, will be
able to meet your criteria easily, being fed the required coordinates from
your model. Many planetarium programs have such models built in, and some
mounts will have quite sophisticated ones in their controllers.
Astronomers though, normally go further, and 'tracking', is augmented by
'guiding'. Here a seperate lens/scope, is used to keep the target
accurately centred. This reduces the demands placed on the actual
'accuracy' of both the mount, and model, since provided the system can
point well enough to actually put the 'target' on the guide chip, the
position can be fine tuned by feedback from this sensor. For astronomy,
guiding to fractions of an arc second, is typical. Now it might well be
worth considering this approach to your problem. If (for instance), a 20mm
camera lens, is mounted rigidly parallel to your instrument, and this is
fitted a solar filter, and feeds to a simple CCD camera, using a basic
sensor, with 7um pixels, and binned 2*2, the 'Sun', will be an easily
resolvable 'dot', only about 4 pixels across. A typical guider, can
maintain pointing to accuracies of a tiny fraction of a pixel (especially
at such a crude scale), and this would then allow a slightly cheaper mount
to be used, and the system to correct for some mechanical irregularities.
You need to think of the weight involved, how the system is to be
protected (rain etc.), how the system will cope with long periods without
re-acquiring the Sun (this increases the basic 'acccuracy' required of the
mount and model). Tracking the Sun to your required accuracy is not hard
(for instance, on the Venus transit, I used a fairly basic 'Gem' mount, (a
Vixen GP-DX), and with a reasonable polar alignment from the night before,
the Sun only moved in the image, by about 24 arc seconds, for the entire
period of the transit. With better alignment, this could easily be beaten.

Best Wishes

Another answer might be a heliostat, where a mirror is driven to keep the
sun's image stationary.
jc

wrote in message
oups.com...
Hi all,

Honestly, I know very little about this filed of astronomy, and that's
why I need your help. My research involves an new instrument
that is supposed to point the center of the sun disk to measure solar
beam at a certain spectrum. Since our instrument has a 1-degree field
of view only, I need a tracker to accurately track the sun at least
within 0.1 degree. I heard that amateur astronomers use very accurate
trackers to track stars. Could anyone give me some information about
it? Any guidance you can provide would be greatly appreciated.

Christine

wrote in message
oups.com...
Hi all,

Honestly, I know very little about this filed of astronomy, and that's
why I need your help. My research involves an new instrument
that is supposed to point the center of the sun disk to measure solar
beam at a certain spectrum. Since our instrument has a 1-degree field
of view only, I need a tracker to accurately track the sun at least
within 0.1 degree. I heard that amateur astronomers use very accurate
trackers to track stars. Could anyone give me some information about
it? Any guidance you can provide would be greatly appreciated.


How long do you need to track for? Dawn to dusk tracking with some designs
of equatorial mount can be a problem depending on the size and weight of the
instrument, due to clashing of the mount with the support. A fork mount
might be a better option eg
http://www.scsastro.co.uk/cg070001.htm
Your best bet may be to find your local astronomy society who will no doubt
be glad to demonstrate what is available

Robin