I Bought a 2-meter Observa-Dome

It's at http://www.davidillig.com/ast-thedome.shtml.

It is 28 years old, but it appears to be in nice condition -- rotation
and shutter operation are smooth and easy. It is made of welded
aluminum. It was not in my mind to buy a dome, but one does not see
used ones very often, so this was a target of opportunity.

I had planned to build a small observatory this spring with a pier and
the Milburn Wedge that I have ordered for my 8" LX200
http://www.davidillig.com/ast-m45.shtml. This changes the equation,
considerably, and I will have to scrap the plans that I have been
drawing. I'm thinking of a 12-sided, 4-ft high base with a stoop-down
entry door, mounted on a concrete pad with the pier also mounted in
concrete, but isolated from the base.

I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?
I figure that when I want to move the telescope to a new target I could
disengage the rotator and manually rotate the dome to a new starting
position, the re-engage. So, will that work?

Thanks,

Davoud

--
usenet *at* davidillig dawt com

"Davoud" wrote in message
...

I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?

Only if you are at the North or South Pole

At temperate latitudes, consider what's going on.

If you're aimed at Polaris, you don't want the dome to rotate at all.
Polaris stays put.

There will be an area of sky, high in the south, where rotating 15 degrees
per hour would be almost correct, but it's not all that much of the sky.

In the east and west, objects are moving mostly up or down, not sideways.

"Davoud" wrote in message
...

I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?

Only if you are at the North or South Pole

At temperate latitudes, consider what's going on.

If you're aimed at Polaris, you don't want the dome to rotate at all.
Polaris stays put.

There will be an area of sky, high in the south, where rotating 15 degrees
per hour would be almost correct, but it's not all that much of the sky.

In the east and west, objects are moving mostly up or down, not sideways.

"Davoud" wrote in message
...

I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?

Only if you are at the North or South Pole

At temperate latitudes, consider what's going on.

If you're aimed at Polaris, you don't want the dome to rotate at all.
Polaris stays put.

There will be an area of sky, high in the south, where rotating 15 degrees
per hour would be almost correct, but it's not all that much of the sky.

In the east and west, objects are moving mostly up or down, not sideways.

In article , Davoud
wrote:

I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?

No it wouldn't. Consider the case where you are looking at Polaris for
the simplest counterexample.

Computer control would require that the computer know what RA and Dec
you are tracking. It is probably a lot easier than controlling a
telescope because you can be a lot sloppier. Look into various Dob
drivers such as Mel Bartels', remembering that you only need azimuth.

If you are not taking long astrophotos, you could probably get away
with a variable speed control set by a dial. Check every 5 minutes or
so whether you are going too fast or too slow, and after a while you
will probably get a good feel for what speed you should set it at for a
given point in the sky. For long astrophotos you would likely waste a
few pictures by getting the dome in the FOV before you train yourself.

I don't know what people usually do with domes. I know Palomar had a
mechancial analogue computer for the dome control.

--
David M. Palmer (formerly @clark.net, @ematic.com)

In article , Davoud
wrote:

I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?

No it wouldn't. Consider the case where you are looking at Polaris for
the simplest counterexample.

Computer control would require that the computer know what RA and Dec
you are tracking. It is probably a lot easier than controlling a
telescope because you can be a lot sloppier. Look into various Dob
drivers such as Mel Bartels', remembering that you only need azimuth.

If you are not taking long astrophotos, you could probably get away
with a variable speed control set by a dial. Check every 5 minutes or
so whether you are going too fast or too slow, and after a while you
will probably get a good feel for what speed you should set it at for a
given point in the sky. For long astrophotos you would likely waste a
few pictures by getting the dome in the FOV before you train yourself.

I don't know what people usually do with domes. I know Palomar had a
mechancial analogue computer for the dome control.

--
David M. Palmer (formerly @clark.net, @ematic.com)

In article , Davoud
wrote:

I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?

No it wouldn't. Consider the case where you are looking at Polaris for
the simplest counterexample.

Computer control would require that the computer know what RA and Dec
you are tracking. It is probably a lot easier than controlling a
telescope because you can be a lot sloppier. Look into various Dob
drivers such as Mel Bartels', remembering that you only need azimuth.

If you are not taking long astrophotos, you could probably get away
with a variable speed control set by a dial. Check every 5 minutes or
so whether you are going too fast or too slow, and after a while you
will probably get a good feel for what speed you should set it at for a
given point in the sky. For long astrophotos you would likely waste a
few pictures by getting the dome in the FOV before you train yourself.

I don't know what people usually do with domes. I know Palomar had a
mechancial analogue computer for the dome control.

--
David M. Palmer (formerly @clark.net, @ematic.com)

Davoud wrote in message ...
[...]
I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?
I figure that when I want to move the telescope to a new target I could
disengage the rotator and manually rotate the dome to a new starting
position, the re-engage. So, will that work?

Nope. (Not unless you tilt the dome and polar-align it :-)

Seriously, a quick way to check this for yourself is to use any sky chart
or planetarium program, pick an object (such as a star), step the time hour
by hour and note the azimuth reported by the program for that object.

Think about it for moment. Suppose you wanted to view/image Polaris for,
say, 5 hours. Chances are you wouldn't need to rotate the dome at all.
Unless you want to rotate the dome manually, you'll need a "smart" interface.

One possibility to do it on a budget would be the "Talon" program featured in
the January 2004 issue of LINUX JOURNAL. The article can also be found online
at URL:

http://www.linuxjournal.com/article.php?sid=6673

FWIW, Talon incorporates XEphem as one of its components. Contrary to the
article, the source code is found in the CVS section at:

http://sourceforge.net/projects/observatory/

Davoud wrote in message ...
[...]
I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?
I figure that when I want to move the telescope to a new target I could
disengage the rotator and manually rotate the dome to a new starting
position, the re-engage. So, will that work?

Nope. (Not unless you tilt the dome and polar-align it :-)

Seriously, a quick way to check this for yourself is to use any sky chart
or planetarium program, pick an object (such as a star), step the time hour
by hour and note the azimuth reported by the program for that object.

Think about it for moment. Suppose you wanted to view/image Polaris for,
say, 5 hours. Chances are you wouldn't need to rotate the dome at all.
Unless you want to rotate the dome manually, you'll need a "smart" interface.

One possibility to do it on a budget would be the "Talon" program featured in
the January 2004 issue of LINUX JOURNAL. The article can also be found online
at URL:

http://www.linuxjournal.com/article.php?sid=6673

FWIW, Talon incorporates XEphem as one of its components. Contrary to the
article, the source code is found in the CVS section at:

http://sourceforge.net/projects/observatory/

Davoud wrote in message ...
[...]
I'm not very good at spherical geometry, so please bear with me here. I
don't want to go to the expense of controlling the dome's rotation by
computer, but I would like to auto-rotate it. Would it work to simply
install a motorized rotator that would rotate the dome at 15° per hour?
I figure that when I want to move the telescope to a new target I could
disengage the rotator and manually rotate the dome to a new starting
position, the re-engage. So, will that work?

Nope. (Not unless you tilt the dome and polar-align it :-)

Seriously, a quick way to check this for yourself is to use any sky chart
or planetarium program, pick an object (such as a star), step the time hour
by hour and note the azimuth reported by the program for that object.

Think about it for moment. Suppose you wanted to view/image Polaris for,
say, 5 hours. Chances are you wouldn't need to rotate the dome at all.
Unless you want to rotate the dome manually, you'll need a "smart" interface.

One possibility to do it on a budget would be the "Talon" program featured in
the January 2004 issue of LINUX JOURNAL. The article can also be found online
at URL:

http://www.linuxjournal.com/article.php?sid=6673

FWIW, Talon incorporates XEphem as one of its components. Contrary to the
article, the source code is found in the CVS section at:

http://sourceforge.net/projects/observatory/