Senior Thesis Automation of the Student Astronomy Laboratory Telescope In Partial Fulfillment of the Requirements for The University of Denver Bachelor of Science Degree in Physics Jason Matthew Dahl, Jr.
Table of Contents Introduction Page 3 Chapter 1: The Concept Page 4 Chapter 2: Construction Page 7 Chapter 3: Automation Page 9 Chapter 4: User s Manual Page 17 Chapter 5: Operational Checklist Page 33 Chapter 6: Conclusion and Acknowledgements Page 37 2
Introduction The Student Astronomy Laboratory (SAL) is a combination telescope-periscope that, upon automation, will allow for access to a large telescope without having to leave the comfort of the warm building. It is the main intent of this scope to be used as a teaching and research tool for the students and faculty of the University of Denver. The addition of the necessary parts and creation of the automation program spanned a period of nearly two years. The completion of this automation project will allow for the students and faculty of DU to have a flexible researchgrade telescope system that is outfitted for the 21 st century. Figure 1: SAL opened and pointed at the North Celestial Pole with Assistant to the Chairman Barbara Stephen standing in the foreground. 3
Chapter 1: The Concept SAL was designed primarily for teaching astronomical methods to undergraduate and graduate students at the University of Denver. Large optics combined with cutting-edge computer control allow for quality research to be done while among the city lights in Denver. Furthermore, allowing the light gathered by the rooftop scope to be reflected down to another focusing telescope in the room below has a two-fold purpose. First and foremost, it will keep observers warm on cold nights, exposing only the telescope to the elements. Second, it has the capability of becoming a handicap-accessible telescope. By having the focusing scope in the same position all the time and allowing the scope on the roof to do the navigation, handicapped individuals will now be able to experience the joy of astronomy as seen through a large telescope. The most important use for SAL, however, is its use by the DU students. SAL will allow for hands-on instruction in astronomical observational technique and data collection without requiring students to make the arduous trek up to the Mt. Evans Meyer-Womble observatory site during the school year. Also, because the telescope is located in a milder environment than the Meyer-Womble scope, it can be used all year round. Because of the nature of both the program and the telescope itself, students will be required to think diligently about the objects they wish to observe. Certain objects are unreachable at certain times of the year due to physical constraints. Also, because the telescope is mounted on a German-Equatorial mount, the order in which objects are observed is also important. A mount of this style has one axis always pointed at the North Celestial Pole and, thus to move from the Eastern side of the mount to the Western 4
side, or vice-versa, the telescope must travel through the pole. This can be a time consuming move and it is therefore important for the user to plan his or her observing night carefully so as to not waste time moving back and forth through the pole to each object, but rather start in the West and work their way East. SAL, therefore, will not only give students a chance to observe with a research grade telescope, but also will allow them the opportunity to experience the planning that goes into an observational session, and will help teach them about important observational basics such as coordinate systems and mechanical mount constraints. Of course, another use of SAL will be for advanced University research. Though built as a teaching instrument, SAL has the capability of becoming an invaluable research tool as well. The Right Ascension and Declination encoders on the telescope have resolutions of approximately 35,000 encoder counts per degree and 19,000 encoder counts per degree, respectively. These high-precision encoders allow for mechanical precision that is approximately within 0.2 arcseconds. This kind of precision has been realized in the Right Ascension axis of the telescope, however the Declination axis has only had a repeatable celestial accuracy in the range of approximately 30 arcminutes at the time of this writing. It is estimated that the issue with the Declination axis accuracy is due to an imbalance of the telescope on that axis. This hypothesis is going to be tested shortly to see if both the mechanical precision and the celestial accuracy on that axis can be improved. These high-precision encoders allow for the scope to be pointed accurately at faint objects, which can then be documented with a digital detector. The optical configuration of SAL is not one found in a common, everyday telescope store. SAL has an afocal Mersenne optical configuration, meaning that the light enters the 5
telescope, is collected into a collimated beam and is then sent down through the axes of the telescope 1. Several mirrors (known as figure-four mirrors) inside the axes of the scope bounce the light down to a second, beam-narrowing telescope in room 422 below which reduces the beam s size from 6 to 1 so that attached instruments can make use of the light coming in (see figure 2). Figure 2: Two different pictures of the optical layout for SAL. Both indicate how a collimated beam of light created by the primary and secondary mirrors is bounced to the figure-four mirrors, which are located in the axes of the telescope. The light travels to the condenser telescope (seen in the right image) where it can be sent off to an instrument (in this case, the FTS). The image just to the left with the words chop flat at the top is simply an enlargement of the condenser telescope ray trace. 1 see Jurgenson, Colby A. Doctoral Thesis 2005. University of Denver. 2005. p. 50-51. 6
Chapter 2: The Construction D.U. was contracted with Equinox Interscience in the year 2000 and the telescope and enclosure were delivered to the rooftop in 2003. First light was obtained with the telescope in the spring of 2004 and the decision to upgrade to an automated system to be run from the floor below with the aid of LabVIEW was made in 2006. I began my work on the automation portion of this project in June 2007. Before any computer automation could begin on SAL, it was required that the telescope be outfitted with the appropriate stepper motors and encoders that would communicate with the computer. This was done in two steps. First, the encoders were attached to the telescope, followed by the stepper motors. To attach the encoders required the additional outfitting of two metal plates to the telescope base, one for the Right Ascension axis and a second for the Declination axis. On these plates were attached both the absolute and relative encoders, which were then connected to several gears and then connected to the gearing on the telescope. Thus, as the telescope axes turn, the encoders turn with them, relaying those rotations as information the computer downstairs can decode into a position. To attach the motors, the motor drivers were affixed to the end of the worm shaft that is connected to the worm gear. The motor drivers were then covered with empty plastic bottles that would create a weatherproof environment for the motors. The most difficult part of the outfitting came when the cables were attached to the motors and encoders. Because the telescope rotates about its two axes, there was concern about cable- 7
wrap a condition that occurs when the electronic cables running from the computer to the telescope get wrapped around the telescope, creating tension in the cable. Thus, several extra feet of cable needed to be left at the level of the telescope so that as the telescope moved, the cables would not bind the scope or, worse yet, break altogether. Once the cable-wrap situation was resolved, the cables were fed downstairs during the Spring of 2007 to the computer room where automation of the telescope control could begin. 8
Chapter 3: The Automation The encoders are integrated into the telescope computer system through the use of LabVIEW. This program has the ability to read the attached encoders, decode their values, and turn them into numbers corresponding to the celestial coordinate system. This gives the user an understanding of where the telescope is situated in the sky. The user can then interpret that data, input the coordinates for the object he or she wishes to observe and let LabVIEW communicate with the motors to move the telescope to that desired location. The user also has the ability to command the motors to track an object in the sky, sync with an object in the sky, and drive the telescope under manual control. All of this can be done from the main control panel for SAL. This control panel, however, does not do this all under one routine. Many subroutines are constantly running to make the program run smoothly. It was the compilation of these subroutines that made the main program possible, and that compilation had to be done in a certain order. After outfitting the telescope with the necessary hardware to become a remotely controlled telescope, it was time to create the program that would control it. It was decided that LabVIEW would be the controlling software. LabVIEW was chosen for three main reasons. First, it was already implemented on another telescope built by Equinox Interscience and that was a good jumping off point for me to see where to begin. Second, the motor control cards we used are designed by National Instruments (as is LabVIEW) and, thus, it seemed to be the most logical choice for compatibility. Third, LabVIEW is used in D.U. s intermediate laboratory classes, so students are becoming familiar with it through their course work. It was now my task 9
to create a LabVIEW program (known as a VI, or Virtual Instrument) that would control the telescope from the room below. The first step that was necessary was to have control of the telescope in the form of a hand-paddle and then other subroutines could be written from there. Fortunately, creating the hand-paddle control was easy. National Instruments (NI) has written in to the example codes (under the help menu of LabVIEW) a program written for just exactly what I needed. I simply copied the wiring diagram as shown in the help menu and applied it to the telescope control panel VI (see figure 3). After confirming that I had full control over the telescope, it became very apparent that I needed indicators on the screen depicting the position of the telescope (see figure 4). Again, this code had already been written, this time not by NI, but by Equinox Interscience s programmer Buddy Hahn (there are several subroutines in my program for which I owe gratitude to Mr. Hahn for getting them started). After implementing these indicators, the next most-obvious necessity was a subroutine that determined the local sidereal time. While this is a simple calculation, the subroutine had also already been written, and was thus added to the program (see figure 5). 10
Figure 3: The block diagram (coding) of the hand-paddle control. Here, the x-axis controls east-west movement and the y-axis controls north-south movement of the telescope. Figure 4: The indicators on the main panel of the VI. This give dials of degrees of HA and DEC, running from -180 to 180 and -90 to 90 degrees, respectively. The left indicator can be switched to indicate either Hour Angle or Right Ascension. Figure 5: The program written by Buddy Hahn that calculates, most importantly, the LST or Local Sidereal Time. The most important part of this program was the automatic control of the telescope. It was desired to be able to have the coordinates of an object, plug them into the program, have the program check to make sure the telescope would not hit anything, and then move the telescope to that object. This was the first full subroutine I needed to write. Using the aid of NI Motion (which is another program provided by National Instruments, used to write generic subvis for the NI motion cards), I created the simple code for providing the motion card with a given 11
encoder count and velocity and having the motor move the telescope to that specific location at that specific velocity (see figure 6). I then added that subroutine to the main program, making it work with the push of a switch. It was now possible to move the scope both manually and automatically by encoder count. The next crucial step was to convert those encoder counts into Hour Angle and Declination coordinates. Every star in the sky has been given a set of coordinates, known as Right Ascension and Declination, to distinguish them from other stars. Right Ascension increases to the East and is denoted in terms of hours, minutes, and seconds. Declination, however, has its zero mark at the celestial equator and increases to the North of that point and decreases to the South. Declination is denoted in terms of degrees, minutes, and seconds of arc. Right Ascension and Declination can be thought of as the longitude and latitude of the sky, respectively. Hour Angle and Right Ascension are related to the LST: HA = LST - RA. It was necessary for me to determine how many encoder counts fitted into one hour of Right Ascension and one degree of Figure 6: Two case structures (LabVIEW s version of if, then statements) allow for the separate automatic control of the HA and DEC axes. The squares containing the LabVIEW symbol in each case structure are the subroutines I created in NI Motion for the control of each axis. 12
Declination. In other words, I needed to determine the resolution of the encoders. This was done by, first, choosing a few bright stars, and then calculating the number of encoder counts it took to move in each axis between the two stars. Then, using predetermined Right Ascension and Declination values for those stars, we determined how many degrees we moved the telescope, how many counts we moved the telescope, divided the latter from the former, and obtained the resolution of the encoders (which, as stated above, was 35,213 counts/degree for Hour Angle and 19,196 counts/degree for Declination). The next necessary subroutine was one that would take an input of desired Right Ascension and Declination, turn them into decimal degree versions of that value, then pump it through and multiply by the computed resolution of the encoder to obtain a value (in counts) of where the telescope needed to move to view that object (see figure 7). With this addition, the telescope now was able to move to a desired location on the sky with the click of a button. One of the next important steps that was completed was the implementation of a position zero feature. Fortunately, again, Mr. Hahn had already written a routine for this feature. I only had to implement it into my overall program (see figure 8). It simply allows the user to move the scope to a desired zero point and set that zero point on the front panel of the LabVIEW VI. For example, with the use of the telescope, we wanted the Declination value to read 0 degrees, 0 minutes, 0 seconds when at the celestial equator. To do this, we pointed the telescope at the zenith and, using a bubble level, used the zero feature 13
Figure 7: One particular case for the calculation of the appropriate encoder counts to move the telescope. You will notice the two values noted above (35,213 for HA and 19,196 for DEC) as multiplication factors of the inputed decimal value for the desired coordinates of the move. Figure 8: The case structure that activates the zeroing subvi written by Buddy Hahn. on the VI to zero the readout, then brought the telescope back to the angle that equates to our latitude (at DU, this latitude is 39 degrees, 40 minutes, and 22 seconds) and then zeroed the Declination side again. This gave us zero at the celestial equator. For the zero mark at the meridian, we simply leveled the telescope with a bubble level on the Hour Angle axis and then zeroed the value. 14
As with any research-grade telescope, one must have a way to compensate for the earth s rotation. To do this, a simple tracking program was added to the main VI. This was a simple matter of adding a boolean on/off switch marked tracking and then, in the case the switch was on, having the scope move to the west at a given rate (see figure 9). The track rate (201 counts/ sec) was determined by watching a star in the field of view to make sure it did not move after several minutes. Figure 9: The case structure that, when true drives the Hour Angle motor in a west direct to track the object at which the telescope is pointed. Perhaps the most crucial step in creating the main VI was inputing the scope movement limitations. These were imperative to make sure that the user does not unintentionally command the telescope into the ground or into the north wall. The most difficult part of this entire task was creating a program that would check for clearances in all cases. The essence of how the telescope can move is based on a discontinuous function. Thus, we must use a device in LabVIEW that will check multiple ranges of values (see figure 10). It has clearance from the unstow position all the way around the western side of the meridian, up to the north celestial pole and clearance up to zenith if the Hour Angle axis is in the park position. We also have clearance past the north celestial pole along the east side of the meridian to the southeastern part of the sky. We cannot, however, view any part of the east side of the meridian without going through the pole first due to the placement of the scope on a German-Equatorial mount, as discussed earlier. Therefore, the program checks to see if where you are going is in an allowable 15
zone, then computes whether or not a trip through the pole first is necessary (see figure 11). After those computations are done, if the move is allowed, the telescope is ready to be moved to that position. Figure 10: This is an enlargement of the subvi that calculates the encoder count values necessary to make a move to a desired coordinate. The two symbols in the middle of the case structure with the values coming out the left side are range checkers. With this, LabVIEW checks to see if the incoming HA degree value is between 0-90 and then 270-360 degrees. If it is in one of those ranges, the telescope is allowed to move. If not, the exceeds scope limitations light illuminates and the user should not move the telescope as it will crash. Figure 11: Here, the subvi is checking the relation of the desired Right Ascension versus the current LST, thus computing an HA (HA = LST - RA). From that calculation, it determines if the user is trying to go to the East or West side of the Mount and chooses the appropriate case. 16
Completion of the rough program occurred approximately around February 2008. However, it would be another month and a half of debugging and troubleshooting to make sure that all the components of the VI worked harmoniously with each other. This debugging consisted of redoing the limitation values until it worked in all cases, making sure the HA/DEC to encoder count calculation was correct for the east side of the mount, and the readout for Right Ascension was correct for the east side of the mount at all LST values, to name a few. On Saturday, March 15, 2008, the Student Astronomy Lab became a fully automated telescope. 17
Chapter 4: User s Manual The following several pages will outline, in detail, the necessary steps needed to run SAL from the computer in room 422 of the Physics Building at the University of Denver. These pages should cover everything necessary to make successful use of the telescope. This chapter will be broken up into different sections to make it easier for the user to find necessary information. These sections are as follows: Start Up and Initialization, Unstowing the Telescope, Moving to the Pole, Moving to a Desired Location (Automatically and Manually), Tracking and Syncing on an Object, Stowing the Telescope, and Appendix and Emergency Procedures. Start Up and Initialization: After opening the rooftop and removing the front covers of the main telescope and finder telescopes, the first step is to turn on the computer if it is not already powered on. Log in to the SAL username with the password SAL123. After the system has booted up, three programs need to be launched by the user in the following order: SKY6, Measurement and Automation Explorer (MAX), and LabVIEW 8.0. When SKY6 launches, minimize it and ignore it for now. It will be used later for determining coordinates. Also, minimize MAX for the time being. When LabVIEW opens, on the left hand side under recently opened, launch SAL Main Control. The user will be presented with the Main Control Panel (figure 12). Turn on the power strip that provides power to the motors. Now, maximize MAX and click on the plus sign next to devices and interfaces, then click on the plus sign next to NI motion devices. Finally, click on PCI-7340 and in the pane to the right at the top, click on the button that says initialize (see figure 13). Finally, bring up the main panel and in the upper-left hand corner there is an arrow pointing to the right. Click that button to run the program. The user should see needles indicate 18
the position of the telescope and the LST clock begin to count. The user should then enter the daytime air temperature into the appropriate box (below the DEC indicator) so the computer can calculate the fastest rate allowed for movement (below 60 degrees F, the rate should be less than 10000 counts per second to avoid binding of the gears). Figure 12: Main Control Panel for SAL. Figure 13: Top left corner of MAX. Notice the button that says initialize toward the middle of the screenshot. Push this to initialize the program. 19
Unstowing the Telescope: The first procedural move that the user will make is to take the telescope out of park position. This needs to be done before any other move is made. To unstow the telescope, go to the desired celestial coordinates tab and under desired RA HMS, enter a value close to the current LST, YET STILL LESS THAN THE CURRENT LST as this will prevent any confusion on the part of the program thinking you are trying to go to the East side of the sky (accuracy down to the second is not crucial). For example, if the LST is 1 hour, 30 minutes, enter 1 hour 29 minutes into the desired RA HMS box. Leave the desired DEC DMS box at 0h 0m 0s (see figure 14). This will bring the scope to the celestial equator along the meridian. Now click on the tab labeled AUTO GOTO control. In here, confirm that the desired dec counts reads somewhere in the vicinity of 950,000 (see figure 14a). DO NOT MOVE THE TELESCOPE IN HA AT THIS POINT! The telescope must be unstowed on the declination axis first. To do this, switch the GOTO switch to the on position and enter the desired velocity of the move (in cts/ sec; this velocity should not exceed 20,000) into the appropriate box. Click the goto dec button and the telescope should begin to rise out of the park position toward the celestial equator. When the move is complete, be sure to switch the GOTO switch to off. See figures 15 and 15a for what the telescope and program should look like at this point. 20
Figure 14: Screenshot of the inputed values for desired celestial coordinates to unstow the telescope. Notice the value of the desired RA. It is close to the current LST, but still less than the current LST. Figure 15: SAL in its unstow position at the celestial equator. 21
Figure 15a: Screenshot of the main control program when the telescope is unstowed. 22
Moving to the Pole: The next appropriate move is to take the telescope to the pole (unless all your observing is to be done on the western side of the sky, in which case, proceed directly to the next section of this manual). To move the telescope to the pole will require two moves from the unstow position. The first will require going to the western horizon in Hour Angle and the second to the pole in Declination. From the unstow position (celestial equator at the meridian), click on the desired celestial coordinates tab. From there, do not change the desired declination value, but under the desired RA HMS value, enter a value 5 hours and 30 minutes to the west of LST (that is, 5 hours and 50 minutes less than the current LST...remember, LST increases to the East; see figure 16). Now, click on the AUTO GOTO control tab and switch the GOTO switch to on. Next, enter the desired velocity for the RA axis in the appropriate box (remember, do not exceed 20,000 cts/sec) and click on the goto RA button and confirm the telescope is moving to the West. See figures 17 and 17a for images of what the telescope and program should look like at this stage. Figure 16: LST and the corresponding desired RA HMS entered to go to the west horizon. 23
Figure 17: SAL as it looks when pointed at the western horizon. Figure 17a: Screenshot of the main program when the telescope is at the western horizon. 24
After the telescope reaches the western horizon, the move in Declination to the pole is next. To do this, return to the desired celestial coordinates tab and, without changing the RA value, enter 90d 0m 0s into the desired DEC DMS box (see figure 18). Return to the Auto GOTO control and, if not already on, switch the GOTO switch to the on position and then click the goto dec button. The telescope should begin to move toward the pole. When the move is complete, switch the GOTO switch to the off position. The telescope is now pointed at the North Celestial Pole and the LabVIEW program reflects that case, as in figures 18a and 18b. Figure 18: Inputed desired DEC DMS to go to the pole. Figure 18a: SAL as it looks when it is pointed at the north celestial pole. 25
Figure 18b: Screenshot of the main control program when the telescope is pointed at the pole. Moving to a Desired Location (Automatically and Manually): Moving to a desired location in the sky is much like the three moves that the user has already completed. The first step is to bring up SKY6 from where it was minimized earlier. In SKY6, hit the f-button on the keyboard to bring up the find menu. Under that menu, type in the object that is to be observed. SKY6 will then bring up information on that object, including its published RA/DEC coordinates. Copy those coordinates into the desired RA HMS and desired DEC DMS boxes in the desired celestial coordinates tab in LabVIEW. The computer will then compute if that move is legal. Provided that the user does not get an illumination on the exceeds scope limitations light, the user can move on to the next step. Next, click on the AUTO GOTO control tab. Whenever possible (which, should be about 95% of the time), MOVE THE TELESCOPE IN DECLINATION FIRST! This will avoid many issues with the North wall. The user will have to use some common sense as to how to 26
move the telescope in the most efficient way possible, but that simply requires a little thought before haphazardly pressing the goto buttons. Once the move is double checked by the user to be an okay and legal move, switch the GOTO switch to on and press the goto dec or goto RA button, whichever is being moved first and allow the telescope to finish the move. Upon completion of the first move (which, again, should have been in DEC), press the other goto button to move the telescope on the other axis. Upon completion of that move, the telescope should be pointed at the desired location. Be sure to move the GOTO switch to the off position upon reaching the desired object. If any adjustments need to be made, or to simply move the telescope manually, click on the manual control tab (see figure 19). From this tab, the user can input both a slow and a fast rate of slew for the telescope (and toggle back and forth between them) and freely move the telescope in both axes. Each button is appropriately named for the direction it will move the telescope. Press the corresponding button to the direction you want to move the telescope. It is important to remember that the telescope will only move in manual mode if the GOTO switch in the AUTO GOTO control is in the off position. For small moves, it is recommended that the user move the telescope at a slow speed, roughly 2000-3000 counts per second, whereas, for big moves, the user should move the telescope at a fast speed, roughly 10000-12000 counts per second. 27
Figure 19: Screenshot of the Manual Control tab. Note that the DEC axis needs to remain as axis 2 and the HA axis needs to remain as axis 1. Changing this will cause the button control to switch (North would move the telescope East). Tracking and Syncing on an Object: To track an object, the user simply needs to point the telescope at that object (as described above) and click on the tracking tab. In that tab, the user simply needs to switch the Track switch to the on position (see figure 20). The user can verify the telescope is tracking by confirming the position HA 2 value is increasing. Again, the telescope will not track if the GOTO switch is in the on position, so be sure to switch it off upon reaching the desired destination. Figure 20: Screenshot of the Tracking tab. The track rate is variable by the user, but it should not deviate much from 200-201. The sync function of the program is used to make corrections to the readouts given on the main panel. For example, if SKY6 claims that the object of interest is at 3 hours 32 minutes 12 28
seconds Right Ascension and the control panel, when the telescope is centered on the object, reads out 3 hours 33 minutes 12 seconds Right Ascension, the user can use the sync feature to bring the readout back to the correct value. All the user has to do is input the offset into the corresponding box to change the readout to the correct value (see figure 21). This same value must also be entered into the corresponding box on the desired celestial coordinates tab so that the computer can take the correction into account when moving to the next object (see figure 22). IMPORTANT: ZERO OUT ALL SYNC OFFSETS BEFORE PARKING THE TELESCOPE. IF THIS IS NOT DONE, THE USER RISKS CRASHING THE TELESCOPE! Figure 21: The sync tab of the main control panel. Note that the text indicates which sign (+/- or N/S) to use to move the reading in the correct direction. Figure 22: the desired celestial coordinates tab of the main control panel. Note the sync offset inputs that must be copied from the sync page. 29
Stowing the Telescope: To stow the telescope, the procedure is essentially the reverse of the unstowing procedure. First and foremost, GO TO THE POLE. It is easiest to park the telescope in a three step move from the pole. If the user is already on the western side of the pole, it may be easier to go to the park position without going back to the pole, but that is a decision to be made by the user. For the purposes of this manual, I will simply discuss how to park the telescope from the pole position. From the pole, input into the Declination box under the desired celestial coordinates tab 0 degrees, 0 minutes, 0 seconds. This will return the telescope to the western horizon. Under the AUTO GOTO control tab, switch the GOTO switch to the on position and press the goto DEC button to move the telescope. When the move is complete, the telescope and program should look as they do in figures 17 and 17a. Next, return to the desired celestial coordinates tab and input into the Right Ascension box a value that is very near the LST, YET LESS THAN THE LST. This will keep the telescope from going past the meridian when returning to the park position. Return to the AUTO GOTO control tab and press the goto RA to move the telescope back near the meridian. When the move completes, switch the GOTO switch to the off position and proceed to the manual control tab. Under the slow speed box, enter a speed of 500 and move the toggle switch to slow. Continue to move the telescope East until the position HA value reads less than 100. Then, lower the speed in the slow speed box to 16. This will allow the user to move the telescope in single count increments. Continue to move the telescope East until the Position HA value reads 0. The telescope is now on the meridian. 30
Return to the desired celestial coordinates tab and enter 47 degrees, 0 minutes, 0 seconds South into the Declination box. Return to the AUTO GOTO control tab and switch the GOTO switch to on. Press the goto DEC button to lower the telescope to near park position. When the move completes, return to the manual control tab. In the slow speed box, enter a value of 500 and proceed South until the Position DEC value reads less than 100. Again, change the slow speed value to 16 and continue South with the telescope until the Position DEC value reads 0. The telescope is now in the park position. Press the stop sign two buttons to the right of the run button in LabVIEW to stop the program and turn the power to the motors off by turning off the power strip. Return the front cover on the main telescope and finder telescopes and rack the focusers all the way in. Turn off the telrad, if used, and turn the finder eyepieces inward to face the telescope. Close the rooftop and the telescope is stowed. Appendix and Emergency Procedures: First, the user should be advised that while great care has been taken to keep the telescope from being able to be run into things, not every limitation could possibly be thought of. The artificial horizon drawn in SKY6 is not perfect and the limitations in LabVIEW are very conservative. When in doubt, the user should always make conservative movements and then use the manual control feature to approach a limit. Some thought is required with every move that is made with this telescope. Second, in the event of a telescope runaway, turn off the power to motors on the IMMEDIATELY! After the motion of the telescope stops, stop the program and return to MAX and click on the plus sign next to PCI-7340 and then the plus next to interactive and then click on 1-D interactive. Confirm the encoders have stopped counting on both axes 1 and 2 (if 31
they have not, simply press the kill button at the top of the screen). Reinitialize and restart the LabVIEW program and manually return the telescope to the park position (the park position of the telescope is written in between the two dials). Then, in MAX, click on the 1-D interactive section again and, on both axes 1 and 2, reset the encoder values to 0. The telescope has now been reset and the user can restart his or her observing session. 32
Chapter 5: Checklist Start Up and Initialization: Open the rooftop Remove all necessary covers Log In on the Computer, username = SAL, Password = sal123 Start SKY6 Start Measurement and Automation Explorer Start LabVIEW 8.0 (note: this program takes several minutes to boot) Open SAL Main Control Turn on the monitors with the power strip Turn on the encoders with the power strip Enter daytime air temperature Initialize the encoders in MAX by clicking on the plus sign next to devices and interfaces, then on the plus sign next to NI Motion devices, then on the words that say PCI - 7340. Click the button at the top-middle of the screen that says initialize. Start the control program by clicking the arrow in the upper left-hand corner of the LabVIEW program Check for accurate clock time, then check and cross-reference the given LST in the main control program with SKY and confirm it is correct Unstowing the Telescope Enter a value close to the LST yet less than the LST in the desired RA HMS box Enter N 0d 0m 0s into the desired DEC DMS box 33
Enter the desired rates for the HA and DEC axes on the AUTO GOTO tab (note: do not exceed 20000 cts/sec) Switch the GOTO switch in the AUTO GOTO tab to on and press the goto dec button When the move has finished, switch the GOTO switch to off Slewing to the Pole Return to the desired celestial coordinates tab Enter a value 5 hours and 50 minutes West of the LST (less than LST) into the desired RA HMS box. Switch the GOTO switch in the AUTO GOTO tab to on and press the goto RA button. This will put the telescope at the Western horizon. Enter a value of N 90 degrees, 0 minutes, 0 seconds into the desired DEC DMS box press the goto dec button When the move completes, switch the GOTO switch to off. This will put the telescope at the pole. Moving to a Desired Location (Automatically and Manually) Switch the toggle switch next to the RA readout to Actual RA Determine the coordinates of the object the user wishes to observe in SKY6, and enter those coordinates into the desired RA HMS and desired DEC DMS boxes (note: use the Equatorial coordinates, not the Equatorial 2000 coordinates. Also, note that + = N, - = S.) Switch the GOTO switch in the AUTO GOTO tab to on. Verify the desired HA and DEC count values are less than any of the posted limits. 34
Determine which axes should be moved first to avoid collisions (95% of the time, it should be in DEC). Move in that axis by pressing the corresponding goto button When that move completes, move in the other axis by pressing its corresponding goto button Switch the GOTO switch to off when the telescope completes the move For manual movement or fine adjustments, open the Manual Control tab and use the corresponding buttons to move the telescope in the desired direction, controlling the speed with the two corresponding boxes and its toggle switch Tracking and Syncing on an Object To track an object, make sure the GOTO switch is off. Then, in the Tracking tab, switch the TRACK switch to on. Confirm tracking is on by seeing if the position HA 2 value is increasing. Proper Track Rate is 201. To Sync on an object, center on the object and then insert the offset values into the respective boxes in the SYNC tab as instructed on screen. Copy those offset values into the corresponding boxes in the desired celestial coordinates tab Stowing the Telescope ZERO ALL SYNC VALUES BEFORE PARKING THE TELESCOPE Return to the Pole (5 hours 50 minutes West of the LST on HA, N 90 degrees, 0 minutes on DEC) Return to the Western Horizon (5 hours 50 minutes West of the LST on HA, N 0 degrees 0 minutes on DEC) Return nearly to the Unstow Position (0 hours 10 minutes on HA (that is 10 minutes West of LST), N 0 degrees, 0 minutes on DEC). Switch the GOTO switch to off 35
Finish the move manually to 0 hours 0 minutes HA Move to the stow position (S 45 degrees, 0 minutes in DEC) Finish the move manually to the final park position listed on the program. Stop the LabVIEW program Close all open programs, don t save any changes to LabVIEW or SKY6 Turn off the encoders Turn off the monitors Replace all covers and close the rooftop Log off the computer 36
Chapter 6: Conclusion and Acknowledgements My experience on SAL has greatly improved my knowledge of both observational astrophysics and LabVIEW programming. To be able to write this program, it was necessary for me to have a comprehensive understanding of how a telescope on a German-Equatorial mount moves around the sky and, specifically, how SAL moves around its mount and with respect to its enclosure. The extensive amount of time that I spent writing this program has furthered my understanding of LabVIEW exponentially. I know this is knowledge that will carry me far in my chosen career. I would like to thank, first and foremost, Mr. Buddy Hahn, whose help was necessary to the creation of this program. Without Mr. Hahn, I would not have gained nearly as much knowledge about LabVIEW. Secondly, I would like to thank Russ Mellon and Equinox Interscience for their help in procuring the necessary parts to begin the automation process. Their help in the beginning stages of this project was invaluable. Finally, I would like to thank Dr. Robert Stencel and the University of Denver Physics and Astronomy program for providing me with the opportunity to learn so much and work in a field I find very interesting. SAL will, hopefully, one day be a very valuable tool. There are still many steps to complete before the telescope can be deemed finished. Mine is simply a small part among many. This telescope has the potential, I believe, to do great things and this program will help it get there. I sincerely hope to see SAL fully operational in the very near future. 37