User Manual - UWMRO/TCS GitHub Wiki
Contents
Introduction
Welcome to the User Manual for Bifrost, the TCS user interface at Manastash Ridge Observatory. The contents of this manual is ordered as a guide, allowing a new user to walk through correct operation procedures for a typical observing night. Before we layout proper use of the software for the observer, it is necessary to communicate the hardware and software needed for correct operation.
Heimdall
Bifrost is run on Heimdall, the right-hand computer in the control room. It will only work as intended on Heimdall, as it utilizes the mcapi telescope drivers located on the machine. In general, Heimdall should be kept on at all times, but in the event of a necessary reboot a click can be heard from the computer rack when the mcapi drivers successfully initialize.
Bifrost
The Graphical User Interface for the TCS has been given the name Bifrost. Bifrost will be the primary piece of software discussed in this user manual. It can be booted from Heimdall's Desktop. When booted, Bifrost will attempt to launch the rest of the TCS. This means the user will not usually have to interact with any of the other TCS components during observing, but in the event of complications or crashes Bifrost will usually need to be restarted. A desired feature in the future is to save the observing session so that Bifrost can pick up where it left off prior to a reboot, but for now Bifrost will need to be reinitialized on launch.
The Bifrost UI has been built with some basic color organization to group buttons by function. All blue buttons will move one or more of the telescope axes (RA, DEC, Focus). All green buttons will bring up a plot. When learning the Bifrost software, mind these colors as they indicate what the button is intended to do. For example, when "focusing" the color scheme helps explain that Increment Positive and Increment Negative do not actually move the telescope focus axis. Only Move Relative, which is colored blue, moves the focus axis.
Evora
For strict telescope control, Evora has no influence. But for the observer, Evora is a worthwhile mention in this manual. Evora is the Image Acquisition Graphical User Interface (GUI) run on Loki, the left-hand computer in the control room. An observing team will need to use both Bifrost and Evora to collect astronomical data. The Evora GUI controls an Andor CCD Imager (1024 x 1024) and a filter wheel for proper filter selection. The link to the documentation and user manual can be found in the sidebar.
Initialization
Launching the Bifrost Software
The TCS environment is booted by clicking the Bifrost icon on the desktop. The software will take a few moments to load, as it starts the TCS server, gives it some grace period to initialize and then connects the Bifrost client to it. If Bifrost does not load when clicking on the icon, chances are another instance of it is running in the background. If the problem persists after confirming no other Bifrost client is active, consider restarting Heimdall.
On boot, you will be greeted with this screen, the Telescope Control tab. The Telescope Control screen keeps track of relevant position and time quantities for observing and allows users to perform important actions such as Slewing, Jogging, Tracking, Pointing and Focusing. An important mention is the red Emergency Stop button. If the telescope is ever moving in a way that is dangerous to the user or the telescope, the Emergency Stop will cut any motor movement and force a stop of the telescope. If you ever press this, a full restart of Heimdall will be required. Notice that most of the buttons are faded out, they will become functional once the telescope has been properly initialized.
Initializing the Telescope
The first thing that should be done when using the Bifrost software is to initialize the telescope. Click the Initialization tab at the top of the screen to load the Initialization screen, which contains functions necessary for initializing the telescope and it's coordinate systems.
Shown above is the Initialization screen. To initialize the telescope, click the Initialize Telescope Systems button in the Telescope Slewing block. This begins crucial processes, allowing Bifrost to send and receive information from the telescope as well as allowing the hand paddles to control telescope movement (if the telescope key has been turned). Notice that on the Telescope Control screen, Bifrost is now tracking multiple quantities in the Telescope Status block. Additionally, many of the buttons throughout Bifrost have now be enabled. Before moving forward, check the log in the bottom half of the screen to confirm the success of the initialization. Below, the initialization was unsuccessful, as noted in both the log and and the status bar at the bottom of the screen. If this is the case, restart the Bifrost software. Restart Heimdall if the issue persists.
Synchronizing Telescope Coordinates
When the telescope is turned on, it reports by default that it is at Zenith (Pointing straight up, where Right Ascension is the Local Sidereal Time and Declination is the Latitude of Manastash Ridge Observatory). If the telescope is not actually at Zenith, any telescope slew is dangerous as the telescope will incorrectly compute the RA and DEC it needs to move to. Thus, before using the telescope, it is important to synchronize the telescopes reported position with its physical position. This is in the Telescope Coordinates block in the top right of the Initialization screen. Update Telescope Coordinates will set the telescopes measure of its RA and DEC to the values entered in the RA and DEC fields above. If the telescope was off-zenith when Bifrost was launched, the user could enter in the actual RA and DEC of the telescope and click Update Telescope Coordinates to synchronize the telescope coordinates with the physical position of the telescope. However, it is strongly recommended to always synchronize the telescope coordinates when the telescope is pointed at Zenith. There are multiple reasons for this, but in general this is a safer and more reliable way to assure that the telescope is correctly reporting its current physical position.
To do this, move the telescope up to Zenith visually, using the bubble level, the hand paddle and/or the software jog buttons on the Telescope Control screen. When the bubble level is roughly centered, the telescope is ready to be told it's at Zenith. Press the Load Zenith Coordinates button to populate the coordinate fields with the current coordinates of Zenith. Note that LST is the current Local Sidereal Time. Press Update Telescope Coordinates to assert that the current position of the telescope is Zenith.
NOTE: A quirk of this particular function is that "Zenith" in the NAME field will use a different driver command, so if one were to put "Zenith" and a random RA and DEC, the telescope would be synchronized with Zenith. As another caution for synchronizing off-axis, be sure to change the name from Zenith if you plan to do so.
Cover Position & Parking
At MRO, there is a specially defined Altitude-Azimuth position called "Cover Position". It is the position with which an observer can remove and reapply the physical cover on the telescope and the finder scope. In order to slew to Cover Position, make sure that you have first synchronized telescope coordinates. Then press Slew to Cover Position in the Initialization tab. The telescope will move towards the location of the stairs in the dome and stop near the horizon limit.
The other specially defined position is "Parked", or at Zenith. When the user has synchronized telescope coordinates, they may press Park Telescope to return the telescope to the "Parked" position. The observer should always do at the end of the observing night.
Target Selection
Bifrost features a full observing suite, allowing the user to store and generate plots of potential observing targets. This observing suite is contained in the Target List screen, shown below. While containing many optional support features such as finder charts and airmass curves, the Target List also contains functions necessary for slewing and pointing.
Reading and Writing Target Lists
One of the most useful features of Bifrost is the ability to store and load "Target Lists". Target lists are collections of objects with their relevant observing information. These target lists are held in the targetlists folder on the Desktop. A target list is a semi-colon separated file in order Object Name;RA;DEC;Coordinate Epoch;V-mag. For example, look at pointing_stars.txt,a list containing popular stars to point on from MRO shown below.
Vega;18h36m56.33635s;+38d47m01.2802s;J2000;0.03
Arcturus;14h15m39.67207s;+19d10m56.6730s;J2000;-0.05
To read in pointing_stars.txt to the Bifrost Target List. Type in "pointing_stars.txt" in the Object List File Name field and press Retrieve List. Alternatively, in v1.1 of Bifrost the observer may select a target list from the drop down button. When clicked, a list of all files currently in the targetlists folder on the desktop will be displayed. Press Retrieve List load the selected file. If the targetlists folder has been modified since during software operation, click Refresh Choices to update the available lists in the drop down menu.
The information for Vega and Arcturus listed above is now displayed in Bifrost. Objects can also be added manually to the target list through the Name, RA, DEC, EPOCH, and V Mag fields to the right of the screen. RA and DEC can be entered as hh:mm:ss dd:mm:ss, xxhxxmxxs +xxdxxmxxs, or even galactic coordinates where "l=[Value for Galactic Longitude]" is added in the RA field and "b=[Value for Galactic Latitude]" is entered in the DEC field. Be sure when entering information into the EPOCH field that you enter the correct epoch identifier ('J'2000 vs 'J'1975 vs 'B'1950). To add a target manually, press Add to List once all fields have been filled out. Additionally, objects can be removed from the list by clicking on an object (highlighting it) and pressing Remove Selected from List.
Target lists can also be written by the observer. The first method is to manually write a text file in the format shown above and drop it into the "targetlists" folder on the desktop. Then, the target list can be retrieved in the same manner as pointing_stars.txt. The second method is to "Export" the current target list. This allows the user to store the current list of objects in a text file that can be retrieved through Retrieve List. When the user presses the Export List button, Bifrost opens a second window that prompts the user for a file name and directory. After these fields have been specified, the user can then enter the specified file name to retrieve the list of targets written into the file at the time of export.
Observation Planning
Bifrost is fully integrated with the Astropy-affiliated package Astroplan. The user has a selection of useful plots available for any given target on the target list. For any of these plots, the user must first select the target they wish to plot (highlighting it), and then click one of the three green plot buttons.
The first of these buttons is the Plot Target button. As it is up right now, we'll take a look at the Crab Nebula (NGC 1952) with each of these plots. Shown below, the Altitude-Azimuth position of the target is plotted. The red dot is the current position of NGC 1952, and the black dots represent the trajectory of NGC 1952 over the next 8 hours in hour increments.
The next plot is the Airmass Curve button. While each target has a real-time value associated with its airmass in the target list, it is useful to be able to see how a targets airmass will change over the rest of the observing night. The "Airmass Curve", shown below, plots the selected targets airmass over the next 8 hours. There are horizontal lines detailing relevant airmass quality thresholds, however, it is useful to keep in mind that the physical horizon limit of the telescope itself (at 20 degrees above the horizon) limits the observable airmass to anything under ~1.6.
The final plot is contained in the Load Finder Chart button. This button loads a 18' by 18' finder chart (note that this is twice the radius of the Evora science camera field at 9' by 9') of the target, shown below for NGC 1952. An important note for this function is that it is semi-unstable as of v1.0. It is possible that on clicking Load Finder Chart that the Astroplan function will fail to initialize a download. There is a 20 second timeout associated with downloads that should allow a second attempt, but if you have issues with getting this to work, either restart Bifrost or seek finder charts online.
Selecting a Target
When a target on the target list is ready to be observed by the user, the user may select the target from the list and click Select Target to notify Bifrost that this is the intended observing target. This pushes the target information to the Telescope Status screen in the Current Target block. Additionally, it stores the target coordinates for pointing. It is possible to select an observing target manually by entering its information into the Current Target block, however, this is discouraged as it locks out the ability to point and removes the feedback metrics that storing the target in the target list provides. When a target has been selected, the status log will mention that the selected target is now the "Current Target".
Observing a Target
Calibration Images
As a quick aside, much of taking calibration images is discussed in the Evora documentation. However, there is some involvement with the telescope for certain calibration images like dome flats and sky flats. When needing to move the telescope for flats, use either the dome paddle in "Slew" mode or the software Jog buttons on the Telescope Control screen. Follow the MRO checklist for procedural discussion of how this fits into a typical observing night.
Tracking
When preparing to slew to a target, the first thing the user should do is enable "Tracking". Tracking allows the telescope to slowly move with the sky, keeping a desired target in the field of view. Tracking by default is set to the standard sidereal rate of 15.04108 deg/hr. This value may be changed by the user on the Initialization screen. The Tracking block contains the default tracking rate written in the "RA Tracking Rate" field. The user may change this number to whatever they wish and press Set RA Tracking Rate to update the stored value. Note that if the telescope is currently tracking, tracking will need to be turned off and on to properly update the value. The Reset Right Ascension Tracking Rate button will re-enter the 15.04108 deg/hr into the field so that a press of Set RA Tracking Rate will restore the default recommended value. For the average user, this will never be needed. Outside of irregular objects like comets, the standard sidereal rate will always be the best choice.
To enable "Tracking", press the Start Tracking button on the Telescope Control screen. When pressed, the button will change color and its label will change to "Stop Tracking". When tracking, the Tracking field on the status bar at the bottom of the screen will read "True" and the RA field of the TCC Status block should stabilize, meaning that as it updates every second it should read a consistent RA (with some minor fluctuations). Pressing Stop Tracking will disable tracking and restore the button to its original state.
Many functions that request the telescope to move, such as slewing, jogging and hand paddle input, will disable tracking for the duration of the move and re-enable it when available. While unlikely, there is a possibility that Bifrost will fail to properly re-enable tracking, even if the interface shows that it is. The way to diagnose this is to monitor the RA field of the TCC Status block for a few seconds after telescope movement has concluded to see if the RA stays consistent or if it is drifting. If it is drifting (ticking up every second), disable and re-enable tracking. This should be resolved in v1.0, but it is good practice to visually confirm that tracking is on after each slew to ensure the least issues.
Slewing
Once a target has been selected from the target list, its information is added to the Current Target block on the Telescope Control screen. Before slewing, make sure that tracking has been enabled and make sure that you have properly synchronized telescope coordinates.
To slew the telescope to the target, press Start Slew. When slewing, the Start Slew button changes to "Stop Slew". If you need to stop the slew for any reason, pressing Stop Slew will halt the telescope and maintain coordinate synchronization. This allows the user to slew to another desired target without any preparation. Note that the tracking and jogging buttons become unavailable during the slew.
As mentioned in the tracking section, tracking is disabled during a slew. In order to correct for the distance moved by the target during the slewing period, Bifrost utilizes a "Secondary Slew" technique. This means that, once the slew has completed, Bifrost will auto-request a second slew to the target. To the user, this will appear as a flicker of the Stop Slew Button as it flips from finishing the slew to starting a new slew. When the full slew routine is complete, the Stop Slew button will change to "Start Slew" and the user will have control over tracking and jogging.
Pointing
Pointing is the fine-tuning of target coordinates to reflect the physical position of the telescope on the sky. It is necessary as synchronizing the telescope with zenith using a bubble level is an approximation of the correct position. To point, the observer slews to a target object and attempts to center the target in the Evora science camera screen. When the target object is centered, the observer can then tell the telescope it is directly on the coordinates of the target object.
To accomplish this in Bifrost, load in pointing_stars.txt on the Target List screen to get the coordinates for Vega and Arcturus, two bright stars that are often used for pointing at MRO. Determine which object is better at the given time of observing and slew to the target. After the slew has completed, rotate the dome to allow the telescope an unimpeded line of sight to the target and take a brief exposure with Evora. Attempt to find the pointing star in the field, with Vega or Arcturus even if the star is out of the field you will see it's brightness profile on one edge of the screen. Use the paddle in "Set" mode or the software jog buttons in "arcmin" increments to move the object to the center of the field. When the field has been centered, press the Update Pointing to Target button in the Current Target block. This informs the telescope that is is directly pointing at the coordinate position of the pointing star. Once pointing has been updated, future slews should be accurate and bring the target close to the center of the frame.
If you are having trouble finding your pointing star, ensure you have the correct coordinates. If you do, consider re-zenithing the telescope. This can be done quickly using the Park Telescope button on the Initialization screen provided you initially synchronized telescope coordinates.
Focusing
Currently, Bifrost supports "Relative" Focusing. When the user initializes telescope systems, the Focus field in the TCC Status block is set to 0.0. Relative focusing means that this value of 0.0 is not the physical position of the telescope focus axis. Rather, it is just the offset of the focus axis from the focus position when the user initialized the telescope system. Focusing is handled through the Focus block on the Telescope Control tab. The Increment Positive and Increment Negative buttons add or subtract 1500 from the user-editable focus field. When the desired focus increment is in the focus field, press Move Relative to move the focus axis of the telescope in the desired direction.
As a general note about focusing, at MRO focusing is handled manually with IRAF. Assess the moffat PSF of a star in the field of an Evora exposure and try to minimize it through successive relative movements of the focus axis. When a local minimum of moffat PSF is reached (a positive or negative increment from this focus point worsens the moffat PSF), the telescope has been properly focused.