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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 |
#2
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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)? 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 |
#3
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Astro-Physics GTO 1200
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 |
#4
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Astro-Physics GTO 1200
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 |
#5
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Astro-Physics GTO 1200
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 |
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