The Information and Commands a Telescope Needs
In this 1:12 video, Chris explains the journey of the code from the moment you hit submit through the movement of the telescope:
The Quorum you have learned will help in your understanding of how code can help automate the running of a telescope. It will also be essential in your understanding of how Afterglow Access, the image processing software, works behind the scenes.
A PDF of a textfile of the commands of this Part are available at this link:
Open a new Quorum Box for the telescope instructions.
This first command informs Skynet (hence, the word ‘skynet’ is first in the command line), through Quorum commands, which telescope you want to use. Make sure you type the telescope name exactly as it appears, and use the parentheses (this tells Quorum which variable to use for the AddTelescope function), and quotes (simply means that the AddTelescope input is a text variable).
For now, we will use Prompt6 in Chile as our telescope. Look up the telescope if you want to see a picture of it.
The next two lines of code tell the telescope where to look in the sky. The third line sets the name you choose to call the object. In this example, the Messier object, M104, was choosen. The RA and Dec were looked up (Wikipedia works just fine for these well known objects), and then the name was set – in this case ‘M104’. Again, notice the word skynet was used as the first entry into each command line. This sends the Quorum commands to the Skynet server, which will then process the request. Look for an image online if you are interested in what M104 looks like.
Notice the format of the RA and Dec. The units in RA and Dec must be changed to semi-colons. Also, all the information after the commands are in parentheses and quotes.
Use your journal to answer the following questions:
a) What type of object is M104?
b) Briefly define this type of object.
c) Find an image of your target online. Will your telescope image appear like the one you found online? Why or Why not?
d) How will the telescope know where this object is located?
The next commands concern the Sun’s maximum and minium elevation. Chris explains in this 1:27 video:
The numbers seen in these two command are the defaults, but sometimes astronomers want a little bit more control. Therefore the commands can be changed.
Chris talks about filters and the AddFilter command in this 0:49 video:
Recall from the CCD camera activity how filters allow only the desired “color” (which is really wavelength) of photons to interact with each pixel. We will use a “Clear” filter. A clear filter means NONE of the light is blocked except for a small number of wavelengths near ultraviolet. Therefore, most photons in the visible spectrum are collected by the CCD camera. This range of collected photons is affected by the efficiency of the camera. This efficiency is actually called the “quantum” efficiency of the camera, and is determined when it is manufactured.
In this next, 1;21 video, Chris explains exposure length:
A few more notes about the length of the exposure:
Length of Exposures
a.) Overexposure means that some of the pixels have the maximum number of counts in them: they are saturated. The details of the image disappear. Some overexposed images have spikes on some of the stars, but other times it is hard to tell. The image software program, Afterglow Access, has tools to help.
b.) Any underexposed image is a little easier to recognize. The pixels which hold the background light are dominated by “noise” from the camera electronics, so the image looks grainy or speckled. It is hard to remove it with image processing programs. Setting the exposure length takes practice and attention to details.
c.) For the telescope we are using, Prompt6, the exposure length for the Messier objects chosen should be about 30 seconds.
Remember the parentheses tell Quorum to execute the command called “SetExposureLength” . And notice there are no quotes around the number. That is because Quorum reads it as an actual number, not text.
Number of Exposures
We can also request more than one exposure at a time. Why would you need to do that? Come up with at least two reasons. Record these ideas in your journal.
These last commands just close the request. A command for a response is also requested.
action ResponseReceived(text response)
You should now have 15 lines in your Quorum Box. There would be a few more in the beginning to identify your account to use the telescope, and to let the Skynet server now an image request is coming.
Since we do not have permission to use Skynet in this manner at this time, we will move to using Afterglow Access (AgA) with sample images or your own images.
Opening an Image in Afterglow Access
You now know the basic items required for a telescope to collect data. Let’s move on to what can be done with that data.
The link below to Afterglow Access will open in a new window.
Once the link is open, login via Google – this is found to the right of the center of the screen.
**Note: Once you are logged in, if you would like to change the appearance of the program to suit you vision, go to the far right on the blue banner across the top of Afterglow Access and find your initials. If you click on this, a menu drops down with “Theme Editor” at the top. Here you may choose a color scheme, a font weight, and a font size for whatever suits your vision best.
Move to the left of the screen directly under the words “Afterglow Access”.
There are several icons which are named as you move across them.
Find the one that that is titled “Open files”.
Click on that. A popup screen will appear.
There are two file folders here. Choose the one titled Sample. This will open to more file folders.
Choose the Messier folder.
You may open any images you would like. It will open in the viewer window of Afterglow Access. You may open more than one image, since some will be examples of “bad” images.
We will be exploring Afterglow Access and all of its tools in Section 2.
Let’s wrap up this first section on the next page: