Online Observing via twitter
All PULSE@Parkes observing sessions may be followed live via twitter. You need to follow @PULSEatParkes to receive the messages. If you wish to make a comment, ask a question or request and observations please ensure that you reply to this account.
The data from the Parkes radio telescope may be accessed via a few means:
- Visual display through the Parkes Online Monitor. This display includes some key information about the telescope pointing, multiple data plots that update every few seconds and an exterior webcam view of the telescope. The individual components of this display are explained below.
- The Student Data Archive lists all of the observation sessions to date.
- The Student Observation Window provides an image of the folded pulse profile that updates every 30 seconds or so. It also contains a chat window that students can use to log comments in a text file.
The PULSE@Parkes program currently focuses on a catalog of 42 pulsars. These have been selected to show a range of pulsar properties and ensure that there will always be a range of pulsars observable regardless of time of day or date. The list shows the names, positions and basic characteristics of the pulsars.
Once a pulsar has been observed and the data gathered you can then analyse it using out online modules to determine certain pulsar properties. At present one module is fully released with a second currently available for testing:
- Distance Calculator Module allows you to determine the dispersion measure of a pulsar which can then be used to calculate a distance to the pulsar and display it on a plan project on the Milky Way.
- Single Pulse Module is currently being tested so is subject to change. Using it you can determine the period of a pulsar.
Other modules are planned and under development.
Please note that if you are following an observing session online you cannot actually control the telescope. For most observing sessions, school students will be controlling the telescope from our observing site. In most cases this is from CASS Headquarters in Marsfield, Sydney though sessions have been held elsewhere.
For the session on 19 July 2011 we are trialling an interactive twitter observing session. During this session there will be no students controlling the telescope. We invite you, our twitter followers, to suggest pulsars to observe. We will be controlling the telescope form our headquarters but you will be the ones telling us where to point it. We will keep up a conversation via twitter where we will discuss the data and you can ask questions.
The online web monitor is a useful means of monitoring the quality of data coming from the telescope receiver. It provides key information such as times and where the telescope is pointing plus a webcam view of the telescope. It also has a number of plots showing different data from the telescope back ends, computer systems that process the data.
Image 1, above, shows a typical screen view of the Parkes Online Monitor.
The Telescope Status: line at the top of the monitor describes what the telescope is currently doing.
An example may be:
In this case the telescope is tracking, that is following a source across the sky as is the case when actually observing pulsars.
In image 3 the status bar shows that the telescope is slewing to a new coordinate. This occurs when we move the telescope from one source to another, eg a new pulsar. Once you select a new pulsar and start to move to it the status window also displays the slew time which then counts down to 0.0(m) or (s). If a long slew time, say 10 - 15 minutes is displayed you may wish to select another target pulsar that is closer to the first one. Where possible we aim to minimise slew times so that we spend more actual time on sources, observing and gathering data.
The next section of the online monitor contains a bar that looks like this:
This section shows some key information including time, how long before the source sets, wind, receiver and where the telescope is pointing:
- AEST stands for Australian Eastern Standard Time and is displayed in hours, minutes and seconds to the nearest tenth of a second. AEST is UTC + 10.
- LMST stands for Local Mean Sidereal Time, again displayed in hours, minutes, and seconds. This is a vital display that you will need to refer to in order to find out the local sidereal or solar time as this is used to determine which sources are actual visible in the sky above the telescope at any instant. For a detailed description of LMST please visit here (external site).
- Time to set tells you how long before the current source being observed sets below the field of view of the telescope.
- Wind in km/h tells you the average current wind speed. Wind is the major impediment to an observing session. If the wind speed is too strong the telescope systems automatically override the observer. To protect the telescope from being blown off its mount the telescope will slew to the stow position, where the dish is pointing straight up to the zenith. This provides the least wind resistance. You cannot recommence observing till the wind has dropped. The safe wind limit actually depends on a number of factors including average speed, gust strength and the wind direction and where the telescope is pointing. In general once the wind speed approaches 35 km/h you can start worrying about a wind stow.
- Receiver identifies which receiver is being used to gather the data. For most PULSE@Parkes sessions we use the Multibeam Receiver at a frequency of about 1420 MHz.
- RA stands for Right Ascension, displayed in hours, minutes and seconds of arc. RA is one part of the celestial coordinate system and in this instance shows where the telescope is pointing. For details about Right Ascension please view this external site.
- Dec stands for Declination and is measured in degrees north or south of the Celestial Equator. A '-' sign indicates a position south of the Celestial Equator. As the Parkes radio telescope is located in the Southern Hemisphere it cannot observe objects high in the Northern Hemisphere of the celestial sphere.
If you wish to recommend a pulsar for observations during a session you must first check that it is visible in the sky above the Parkes radio telescope during that session. Refer to the list of project pulsars and identify the rise and set columns. These give the times in LMST that the pulsar is visible from Parkes. Check the status bar near the top of the Parkes Online Monitor to find the current LMST at the telescope then work out which pulsars are visible.
As you can see from Image 1 above, the Parkes Online Monitor displays several windows with data plots. Typically these are:
- Flux Density vs Phase
- Time vs Phase
- Frequency vs Phase
A section discussing what each of these shows is being developed. In th meantime we willl disuccss what they show during the observing session
When you open the Parkes Online Monitor if you scroll down the page you will see an image of the Parkes radio telescope. This is a live webcam view. You can adjust the slider to alter the refresh rate for this window.
Image 5: Parkes External Webcam
If your screen is wide enough, click and drag on the webcam image to move it up to the top of the monitor adjacent to the top plots, as shown below:
Image 6: Parkes Online Monitor wih the webcam image moved to top right.
Student Data Archive
The Student Data Archive is a table showing all of the PULSE@Parkes observing sessions to date, listed by date. For each session you can see which pulsars were observed. If you click on one of the ticks for a session it will take you to a page showing the pulse profile from that observation. In some cases you will see multiple pulse profiles on the page. This means that that pulsar was observed more than once during that session.
Image 6: Student Data Archive
Once a pulsar has been observed during a session a tick will appear on the table. You may need to hit the reload or refresh button on your brwoser to update the page though. It ususally takes a few minutes after the observation for the tick to appear.
PULSE@Parkes Pulsar List
This contains the catalog of the 42 project pulsars. Details are provided on the catalog page.
Student Observation Window
This page includes a display of the folded pulse profile that gets updated every 30 seconds or so. It also includes a chat window that students use to log their observations. For external observers we suggest that you follow the twitter stream (@PULSEatParkes) and use the Parkes Online Monitor instead to view the data.
Image 7: Student Observation Window