To understand remote control astronomy, let's have a story that describes one astronomer's observatory, an evening of operating the observatory and some of the problems that arose during the night of observation.
This story presents a typical remote observing session using a remote dome. The folks who will be doing the observations are in their home some 1000 feet away from the equipment. The father (Dad) and son (Josh) want to try taking a CCD image of the galaxy M51, a spiral galaxy with a magnitude of 8.4.
The family has a control room located in the den of their home where the son's networked computer is located. Some of the software loaded onto the son's computer is The Sky, Digital Dome Works, Codas, Remote Focuser, and a communication program. Inside the observatory is another computer with the same software, along with automation hardware including a control box and various sensors, a telescope and an ST-7 CCD camera by Santa Barbara Instrument Group (SBIG). The computers are running Windows 95. The telescope and dome have been aligned and ready to use.
Dad turns on the control room computer and clicks on the communication software. The program brings up a screen that shows the observatory as the host location. Dad clicks on the Observatory icon. The program starts and communications over the network with the Observatory PC where the same communication program is awaiting for a call.
The Observatory PC responds and the two copies of the communication program talk to each other. Dad can now control the Observatory computer from his den. Using his mouse (which is now controlling the observatory computer's cursor) and clicks on the DDW icon. This starts the DIgital Dome Works Control Program (DDWCP) in the Observatory PC. DDWCP then establishes a connection with the DDW processor in the Observatory. In a few seconds, DDW responds and the Observatory PC has established a connection with the processor in the DDW control box. Josh and Dad now look at the resulting data screen that shows the shutter is closed and the dome is in the HOME position.
Dad and Josh could look outside through the den window to see what the
weather is like, but instead they decide to check the weather system mounted
on the dome. Josh clicks the weather button which brings up a screen
showing that the wind is only 5 mph and the temperature is 50 degrees F.
They also notice that it is apparently raining (the weather sensor shows
activity). Dad knows there has been no rain so he decides that birds
may have "done their thing" on the sensor. The problem is that the
measurement interlock will prevent the dome from opening. Dad is
ready to over-ride the sensor to open the dome, but Josh reminds him that
the wetness may be a result of the water falling on the dome from the lawn
sprinkler. After Josh turns off the water, Dad decides it is safe
to override the still wet sensor and opens the dome.
| Comment:
The lawn sprinkler is a good example of a remote observing problem.
Unexpected events will occur, and you need the ability to detect conditions
that may affect operation. A good system will have protection built
in. The user must be cautious in over riding the protective interlocks.
The wetness sensor was doing the right thing: its job is to protect the contents of the observatory. |
Dad now brings up the surveillance camera located inside the observatory to watch the shutter open. Josh now clicks "OPEN". The screen shows that the dome shutter begins to open and in about 10 seconds the shutter is fully open. You can also watch the shutter open with the surveillance camera. Now Dad turns off the camera.
Dad will be slaving the dome to the telescope, so he clicks on the "slave" button. DDWCP will now obtain telescope direction from The SKY software and change the dome position to match. With the dome slave function turned on, Dad is ready to turn on the telescope. He remembers that the CCD camera is not running, and that it takes a while to cool down to be ready for operation. Dad has installed a remote relay device that allow him to turn items on or off in the dome by remote control. He selects the User I/O button on DDWCP and turns on Channel 1. THis connects to a relay that turns on the 120VAC power supply for the CCD camera.
Next he uses his mouse to click on TheSky icon, thus opening a copy of TheSky in the observatory. After a few moments, TheSky planetarium screen shows on Josh's computer. He uses the menu to find M51 and , selecting it, he centers M51 on his screen in a red circle.
Now to run the telescope! He uses the menu to select Telescope/Connect.
After a few seconds, TheSky screen shifts direction, showing a white circle
on some stars, indicating that the telescope is connected, and is pointed
in their direction. Dad again selects and centers M51 in the red
circle. He clicks on M51, which brings up a small data menu box.
He selects "SlewTo" and the telescope begins moving to point to M51.
A small screen shows that the telescope is slewing, and after a few seconds,
the white circle creeps over M51.
| Comment. Note that Dad did things in the "wrong" order--he should have turned on the telescope and then selected M51. This illustrates the desirability of planning your observation to save time and irritation. |
Meanwhile, as the scope is turning, so is the dome. Dad can see this on the DDWCP screen, which is up-dating the position of the shutter opening as the some turns.
Dad now had the telescope and dome aimed at M51. He is ready to operate the CCD camera. He clicks on CCDOPS (the CCD program that comes with this particular CCD camera) which shows up on his computer. He uses the menu to select StartUp.
Josh immediately blurts out, "You did it again, Dad. When you turned
ON the CCD camera, you should have started CCDOPS and started the camera
cooling. If you had, the camera would be ready now!" Dad acknowledges
that Josh is correct and turns on the camera cooling. It would take
five minutes for the camera to get cold enough to operate, but Dad can
still begin using the camera. Dad selects his exposure setting and
takes an image. In a few seconds, the image appears onto his screen.
M51 is not there! But wait, it looks to be just off the CCd chip,
a little to one side. Dad selects the telescope motion controls in
TheSky to move the scope slightly, and then takes a new image. After
several tries, there is M51 almost in the center of the image.
| Comment. CCD cameras are incredible, but the camera-telescope combination is not a "point and click" operation. The field of view is small and skill and practice are necessary to get good results. The sky will still be there tomorrow and next year: astronomy requires patience. |
With M51 centered, Dad asked Josh why he thought the camera did not show it right away. She suggests that maybe the telescope is not set up right. Dad points out that the telescope pointing accuracy is close, but that its software allows you to constantly refine its pointing. So, using the telescope control on TheSky menu, he "synchronizes" the telescope to M51.
Dad suggests to Josh that now he should try to get a good image of M51.
But when Josh takes the image, he notices that the image is very fuzzy
and out of focus. Since the observatory had a remote focusing mechanism,
Josh slowly (remotely) improves the image. After each focus adjustment,
Josh takes a new image to see the result. After a few minutes Josh
obtains good focus and takes a great image of M51.
| Comment.
Again, remote control is not point and click. Focusing is an area
in which available equipment is relatively limited.
This is an area where a litle forethought can prevent most problems. Usually, focus will stay reasonably accurate from one night to the next unless drastic situations occurred. |
Dad now decides that it is time to close the dome. Again Josh uses
the DDW I/O control to activate a remote TV monitoring camera and light
inside the dome so they can see what is happening. Dad show Josh
how to start the video capture in the Observatory PC and they now view
images of the dome's interior. Josh goes back to the main screen
and closes TheSky, thus terminating the connection to the telescope.
Likewise, he turns off the camera cooling and closes CCDOPS. He goes
to the DDW screen and selects CLOSE. DDW directs the dome to turn
to the HOME position, then closes the shutter which both Dad and Josh watch
on the video monitor.
| Comment.
When he closed TheSky, Josh did not first terminate the connection to the
telescope. Although in this case it caused no problem, it is far
safer to turn off programs in the reverse order than they were opened.
Dad and Josh used the video monitor to observe the closing of the dome. This is good practice: you should use all the information available to understand what is going on in a remotely operated facility. But the worst mistake was that Josh neglected to turn off the drive (or the power) to the telescope. As a result, the telescope would continue to track M51 until the wires are wrapped tightly around the telescope, and something BREAKS! In this case, DDW saved them! WHenever the doem closes, if DDW is connected to the telescope it will send a series of commands to the telescope that will stop the drive. |