This page describes how I operate the observatory for a typical observing session. I have included brief discussions of options available and some of the reasons for my own choices.
Shutdown Condition
When not in use,
- The observatory dome is in the home position (aligned with the door) and the shutter is fully closed.
The shutter is only operable with the dome in the home position. When the shutter is fully closed, the observatory, including the dome and shutter, is rated to withstand winds of at least 100 mph.
- The Digital Dome Works (DDW) power supply is turned off.
Shutting off the DDW power supply is a matter of personal preference. I am cautious about leaving things turned on that might cause unplanned motion in my absence.
- The telescope is parked and turned off, with the power cord and all data cords disconnected for improved protection against power surges.
Parking the telescope ensures that it will maintain its alignment information when powered down. I disconnect all external wiring from the telescope as a measure of protection against power surges.
- The telescope is covered with an aluminized fabric shroud that extends to floor level for protection from environment, dust, and insects.
- The observatory computer is operating.
This allows the computer to maintain the current weather information on this website, and allows image processing and other operations to be carried out remotely.
- The air conditioner is left operating during the summer months.
- The observatory security system is enabled.
Although I also do astrophotography, this page only discusses the setup for visual observing. My astrophotography setup and routine are still evolving, and any description of that setup would soon be obsolete.
Startup for Visual Observing
- Disarm the observatory security system.
- Enter the observatory by turning on the DDW power supply using the keyswitch on the outside of the observatory. Use the external operation switch to open the shutter, to allow opening the door and entry.
It is important to resecure the door after entry, since the dome is not designed to be rotated with the Dome Support Ring (DSR) swingout at the door opening unsecured.
There are two external keyswitches. One is used as a power switch for DDW. The other, called the entry switch, controls dome and shutter operation. After DDW is turned on, operation of the second switch automatically rotates the dome to the home position if needed, and then opens the shutter fully. If entering the dome for maintenance, shutter operation can be interrupted at any time by momentary operation of the entry switch.
- Turn on and adjust the red rope lights, and turn off the air conditioner if operating.
Once the initial setup is complete, the power-on indicators for the various equipment items provide plenty of light for dark-adapted vision, and I turn off the red rope lights unless they are needed as a safety consideration for guests.
- Uncover the telescope and stow the shroud. Connect the power and data lines to the telescope control panel, and turn on the telescope. The telescope begins its initialization.
- At the computer, start TheSkyX Professional and the DDW Control Program (DDWCP).
- Verify DDWCP connection to DDW, and use DDWCP to open the shutter fully if not already fully open.
The DDWCP communicates with the DDW controller over a dedicated serial link. The DDW must be in the REMOTE mode in order to respond to the control program.
- When telescope initialization is complete, turn on the optical tube assembly (OTA) fan, if needed.
The fan will almost always be needed, especially in the early evening, since the interior of the OTA will be warmer than the surrounding air. Continue running the fan until thermal effects are not noticable in the eyepiece view. The Meade operating instructions suggest a run time of 5 to 25 minutes.
- Manually slew the OTA to the horizontal position. Remove the objective, eyepiece, and finder covers.
It is much easier to remove and reinstall the optics covers -- especially the large objective cover -- with the OTA horizontal.
- From TheSkyX, establish the link with the telescope.
My first attempts to use the TheSkyX (actually, its predecessor, TheSky6) driver for the RCX400 gave unreliable operation. I use the LX200 GPS driver, which has all the functionality I'm looking for; i.e., to slew the telescope and periodically update the position. TheSkyX also adds the ability to nudge the telescope, which is very handy for centering images on a CCD imager.
- From DDWCP, slave the dome to the telescope.
The DDWCP provides several means to report the telescope position to the DDW controller, including:
- An ASCOM driver
I have been unable to install the DDW ASCOM driver on the Windows 7 (later Windows 10) computer.
- A serial adapter that splits the serial connection from the telescope, sharing ports on the computer and the DDW controller.
This method has the advantage of being independent of how the telescope is controlled, whether manually or from any of several planetarium programs. However, it seems to confuse the telescope. Occasionally the hand controller on the telescope would report "downloading - do not turn off" and become unresponsive. Since no downloading of new firmware was in progress, the only remedy was to power down the telescope and realign it from scratch. I soon abandoned this approach. My guess is that the command packets from the computer and the DDW controller get scrambled together once in a while, causing the scope to see an unintended character sequence. Another artifact was that the DDW would sense a spurious telescope position and rotate the shutter opening to a new position away from the scope. It would return to the correct position on the next query.
- File communication
The best method of synchronization for me is to use the option in the TheSkyX telescope connection that writes the current telescope position to a designated text file. The DDW controller can be configured to query that file and move the dome to the appropriate azimuth. This has worked reliably for years, but requires that the telescope be controlled from TheSkyX. In practice, this is not an inconvenience. A curious observation is that the telescope position is reported in celestial coordinates. TheSkyX and DDW calculate slightly different azimuths for the same telescope position, differing by up to 3 degrees. Both programs are configured with the same latitude, longitude, and time zone, so their conversions between celestial and altazimuth coordinates should agree closely. The error is well within the acceptable band for dome position, so I have not pursued the matter with much vigor.
- An ASCOM driver
Use of the entry switch requires that the DDW controller remain selected to the REMOTE mode and that the ALL STOP panel switch not be closed.
An external paddle switch can allow manual operation of the shutter. The DDW instructions discourage use of this switch for my type of installation (door entry with DDW installed) since it can lead to a short circuit of the DDW controller if the controller is attempting to operate the shutter at the same time. The paddle switch has been disconnected to protect against such a problem.
The observatory is now ready for operation. The startup procedure takes less than 5 minutes.
Observing
- Use TheSkyX to select an object to observe.
- From the Object Information Dialog, command the telescope to slew to the object.
- When the telescope completes the slew, the dome will rotate to the same azimuth as the telescope.
The DDW Controller seems to nearly always do a single dome rotation movement after the telescope has completed its slew. Occasionaly it will do one intermediate movement during a long slew. Presently the DDW controller can't do an anticipatory movement of the dome, since it has no way of knowing the destination of a telescope slew. With the present setup, I would have to write some custom software to support an anticipatory slew. Maybe I'll do that.
- The Object Information Dialog in TheSkyX Professional provides a convenient logging function that can provide almost any desired amount of detail.
Shutdown
- From TheSkyX, terminate the link with the telescope.
This is just good practice. I am about to take manual control of the telescope and dome, and terminating the connection prevents TheSkyX and the DDWCP from trying to continue synchronization.
- From DDWCP, close the shutter. When the shutter is nearly closed, interrupt the closing using the cancel (B5) button on the DDW hand controller.
The shutter close command will also automatically rotate the dome to the home position, and disengage the synchronization with the telescope. The B5 button seems wiser than simply moving the remote operation switch to ALL STOP, since the controller can ramp down the shutter drive current if appropriate.
An alternative is to simply use the external entry switch to close the shutter after exiting the observatory. Using the DDWCP has the advantage of allowing other operatons such as securing the telescope while the shutter is closing.
- Close the DDWCP.
- Manually slew the OTA to the horizontal position. Replace the objective, eyepiece, and finder covers.
- Park the telescope.
- When the telescope is parked, turn it off and disconnect the power and data cables.
- Close TheSkyX if no longer needed.
If I plan to do image processing or review observing logs remotely, then I will leave TheSkyX running.
- Cover the telescope with the shroud.
- Turn on the air conditioner, if needed.
- Turn off the lights, exit the observatory, secure the observatory door and use the entry switch to fully close the shutter.
When the shutter is fully closed, the observatory door can't be opened due to the shutter overlapping the DSR swingout.
- Turn off and lock the DDW power supply.
- Arm the security system.
The observatory is now secured.