Astro-Physics GTO 1200

Hi there,

For a Major Project for the course "Master: Control System
Engineering" at the High school "Hogeschool van Arnhem en
Nijmegen" (www.han.nl) I need to create a control program to control
the GTO 1200 (and the attached telescope).

This program will be used as a demo for new Minor Projects in the
future, starting next year, where students need to create parts of the
control program themselves.

With this program I also need to create a safety feature for the
movements of the mount + telescope. For some angles of the R.A. and
Dec. axis it is possible that the telescope will hit something inside
the dome and will get damaged.

To create the safety feature (safety zone) I created a subprogram which
calculates the coordinates of the telescope parts inside the dome real
time by using a Homogeneous Transformation Matrix (HTM).

The difficult part of this: this subprogram needs the axis angles of
the Right Ascension and Declination axis from 0° till 360° instead of
the axis information which can be received from the mount with the
commands ":GR#" and ":GD#".


My questions:

- Is there a way to define the axis angle (0-360°) out of the mount
response (HH:MM:SS.S / sDD*MM:SS)?
- If not, can I get this needed information by ordering the encoders
and encoder housings (ENC 1200)?


Please contact me as soon as possible so I can go on with my High
school project.



Kind Regards,



Maurice Ebben

Hi there,

For a Major Project for the course "Master: Control System
Engineering" at the High school "Hogeschool van Arnhem en
Nijmegen" (www.han.nl) I need to create a control program to control
the GTO 1200 (and the attached telescope).

This program will be used as a demo for new Minor Projects in the
future, starting next year, where students need to create parts of the
control program themselves.

With this program I also need to create a safety feature for the
movements of the mount + telescope. For some angles of the R.A. and
Dec. axis it is possible that the telescope will hit something inside
the dome and will get damaged.

To create the safety feature (safety zone) I created a subprogram which
calculates the coordinates of the telescope parts inside the dome real
time by using a Homogeneous Transformation Matrix (HTM).

The difficult part of this: this subprogram needs the axis angles of
the Right Ascension and Declination axis from 0° till 360° instead of
the axis information which can be received from the mount with the
commands ":GR#" and ":GD#".

My questions:

- Is there a way to define the axis angle (0-360°) out of the mount
response (HH:MM:SS.S / sDD*MM:SS)?
Yes.
You need to keep it's time synchronised to that on the computer. Then you
can read the sidereal time from the mount (:GS#). This defines where in
the sky the sidereal origin is (saves you having to convert UT to sidereal
in your program). Given the longitude, and this figure, you can then
calculate what angle relative to the scope, this origin is at. Add the Ra
to this, and you have the required mount angle.
Converting HH:MM:SS,or DD:MM:SS, to degrees, is simple. For the DD one,
DD, is degrees, MM, is in 1/60th degrees, and SS, are 1/3600th degrees.
Add them together. For the HH one, do exactly the same conversion for the
minutes, and seconds, and then multiply the result by 15.

- If not, can I get this needed information by ordering the encoders
and encoder housings (ENC 1200)?

Best Wishes

Roger Hamlett wrote:

Yes.
You need to keep it's time synchronised to that on the computer. Then you
can read the sidereal time from the mount (:GS#). This defines where in
the sky the sidereal origin is (saves you having to convert UT to sidereal
in your program). Given the longitude, and this figure, you can then
calculate what angle relative to the scope, this origin is at. Add the Ra
to this, and you have the required mount angle.
Converting HH:MM:SS,or DD:MM:SS, to degrees, is simple. For the DD one,
DD, is degrees, MM, is in 1/60th degrees, and SS, are 1/3600th degrees.
Add them together. For the HH one, do exactly the same conversion for the
minutes, and seconds, and then multiply the result by 15.

Best Wishes

Dear Roger,

First of all thanks for the fast response on my question.

Maybe I was not clearly enough when I asked my question.

Correct me if I'm wrong but when I look at you solution I think it
calculates some sort of azimuth of the mount.
I just need the shaft angle of the RA and DEC axis on the mount. So how
much did the axis of the RA or DEC rotate.

Hope to hear from you soon.

Kind regards,

Maurice

wrote in message
ups.com...

Roger Hamlett wrote:

Yes.
You need to keep it's time synchronised to that on the computer. Then
you
can read the sidereal time from the mount (:GS#). This defines where in
the sky the sidereal origin is (saves you having to convert UT to
sidereal
in your program). Given the longitude, and this figure, you can then
calculate what angle relative to the scope, this origin is at. Add the
Ra
to this, and you have the required mount angle.
Converting HH:MM:SS,or DD:MM:SS, to degrees, is simple. For the DD one,
DD, is degrees, MM, is in 1/60th degrees, and SS, are 1/3600th degrees.
Add them together. For the HH one, do exactly the same conversion for
the
minutes, and seconds, and then multiply the result by 15.

Best Wishes

Dear Roger,

First of all thanks for the fast response on my question.

Maybe I was not clearly enough when I asked my question.

Correct me if I'm wrong but when I look at you solution I think it
calculates some sort of azimuth of the mount.
No. The Dec, _is already_ the angle of the Dec motor shaft (unless the
scope is flipped). In RA, the scope is pointing at an angle defined by the
RA it is pointing at, the longitude of the scope, and the sidereal time.
This is what I describe.

I just need the shaft angle of the RA and DEC axis on the mount. So how
much did the axis of the RA or DEC rotate.

Hope to hear from you soon.
Imagine this. A scope is at a point/time where it's Meridian, aligns with
0RA. At this moment, the RA, defines the angle the mount is at (with the
caveat of the 180 degree flip at the meridian itself, on both axes). So if
the scope is pointing at 0RA, then the mount is either horizontal to the
east, or to the west. If instead the mount is looking at 23hours RA, then
axis will now be 15 degrees above the horizontal with the tube to the
west. If instead it looks at 22 hours RA, now the tube is 30 degrees above
the horizontal on the same side (assuming a flip at the meridian). However
an hour latter, the 0RA point, has moved one hour to the west. So now
looking at 22 hours RA, the tube is only 15 degrees above the horizontal.
So, you need to calculate the relationship between the 0RA point, and your
meridian. Your meridian is defined by the longtitude. Then the position of
the 0RA point is defined by the sidereal time. With those two figures, and
the point where the scope is pointed (with a 180 degree 'tweak' for the
flip), you have the angle of the RA shaft. The controller will return
which side of the mount it is on (S# returns this). So, once you have
the angle, you can just flip the results 180, if the scope is on the other
side of the mount, and have the actual angles for both axes.

Best Wishes

Roger Hamlett wrote:
wrote in message
ups.com...

Roger Hamlett wrote:

Yes.
You need to keep it's time synchronised to that on the computer. Then
you
can read the sidereal time from the mount (:GS#). This defines where in
the sky the sidereal origin is (saves you having to convert UT to
sidereal
in your program). Given the longitude, and this figure, you can then
calculate what angle relative to the scope, this origin is at. Add the
Ra
to this, and you have the required mount angle.
Converting HH:MM:SS,or DD:MM:SS, to degrees, is simple. For the DD one,
DD, is degrees, MM, is in 1/60th degrees, and SS, are 1/3600th degrees.
Add them together. For the HH one, do exactly the same conversion for
the
minutes, and seconds, and then multiply the result by 15.

Best Wishes

Dear Roger,

First of all thanks for the fast response on my question.

Maybe I was not clearly enough when I asked my question.

Correct me if I'm wrong but when I look at you solution I think it
calculates some sort of azimuth of the mount.
No. The Dec, _is already_ the angle of the Dec motor shaft (unless the
scope is flipped). In RA, the scope is pointing at an angle defined by the
RA it is pointing at, the longitude of the scope, and the sidereal time.
This is what I describe.

I just need the shaft angle of the RA and DEC axis on the mount. So how
much did the axis of the RA or DEC rotate.

Hope to hear from you soon.
Imagine this. A scope is at a point/time where it's Meridian, aligns with
0RA. At this moment, the RA, defines the angle the mount is at (with the
caveat of the 180 degree flip at the meridian itself, on both axes). So if
the scope is pointing at 0RA, then the mount is either horizontal to the
east, or to the west. If instead the mount is looking at 23hours RA, then
axis will now be 15 degrees above the horizontal with the tube to the
west. If instead it looks at 22 hours RA, now the tube is 30 degrees above
the horizontal on the same side (assuming a flip at the meridian). However
an hour latter, the 0RA point, has moved one hour to the west. So now
looking at 22 hours RA, the tube is only 15 degrees above the horizontal.
So, you need to calculate the relationship between the 0RA point, and your
meridian. Your meridian is defined by the longtitude. Then the position of
the 0RA point is defined by the sidereal time. With those two figures, and
the point where the scope is pointed (with a 180 degree 'tweak' for the
flip), you have the angle of the RA shaft. The controller will return
which side of the mount it is on (S# returns this). So, once you have
the angle, you can just flip the results 180, if the scope is on the other
side of the mount, and have the actual angles for both axes.

Best Wishes

Oke, now I get your point.
Many thanks for your help