Periodic Error Correction

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Periodic Error Correction

Opening the Dome

1. Turn off PEC in The SKy->Telescope->Options->More Settings by unchecking the "Apply PEC correction" box.


Figure 1: PEC window in The Sky. In More Settings window accesible from the Telescope->Options menu.

2. Open PEMPro. In the Setup tab (one of the lower tabs), connect to the scope and the camera. Switch to the Acquire Data tab, and set the exposure such that the bright star you are pointed at is bright but no saturated. Press Start to begin acquisition. Once Image is exposed. check Maxim DL to make sure it found the star, and not just a hot pixel. Acquire data for a large number of periods.

3. When you have enough periods, click Stop. Save teh data, and you will be prompted to create a PE curve, which you should do (if for some reason you do not, at a later point you can load the data into the Analyze tab and click Create PEC Curve there.) Do not worry about any synching messages. A separate curve creation window will open, and a curve will be fitted automatically. Check to see if any frequencies need to be added; you can reference the Frequency Spectrum from the upper right pull down menu. The RMS error in the upper left window may be on interest. Thsi window, along with the analyze data tab in teh main window displaying the raw data collected with the correction off on 06/01/2010 are shown in figure 2. Save the curve by clicking the 'Create Paramount PEC curve' button. It will ask you if you want to open the curve data in a text file, which is unnecessary at this point. NOTE: if a this or any point it asks you to invert the curve, be careful. We determined that we do in fact need to invert the curve, but this is confusing (it is hard to tell exactly what each of the graphs represents: error, correction, telescope offset, star offset, etc.) and it is important to keep track of any inversions. You do not have to invert when prompted, since as we will see we can do it in the Refine window.


Figure 2: raw data with correction off from 06-01-2010 in teh analyze tab of the main menu, and the PEC curve creation window fitting a curve to the data.

4. Once the Top lip has cleared the Bottom, push the BOTTOM lever to the LEFT. This needs to be manually stopped by pushing the lever back to the center 'off' position. You will hear the motors straining once it is fully opened.

Powering up the Telescope

5. Remove the cover for the large mirror.

6. Turn ON the power on the black uninterruptible power supply (UPS) at the base of the telescope. The green power light will flash for a few seconds; wait until it glows steady green before proceeding.

7. Turn ON the power for the telescope on the black box in the base. Listen for 2 beeps.

Software Setup and Connections

If not already on, start up the PC that operates the telescope.

Log in to the PC as user "telescope".

13. Open TheSky6.

14. Establish link to telescope by clicking green telescope icon in the top shortcuts menu

15. Allow telescope to home if it wasn't done manually with the joystick. Listen for 3 beeps.

16. Open ddwcp.

17. Wait until program connects with the dome then check "Slave to Telescope." (Don't do this if you don't want the dome to move with the telescope, i.e. if you want to take dome flats.)

18. Open MaximDL Pro 5.

19. Click "Toggle Camera Control" (Ctrl + W) in the top shortcuts menu.

20. Camera 1 should read "Apogee U16M".

21. Select Camera 2 from Setup Camera, or "No Camera" if there isn't one connected.

22. Click "Connect."

23. Directly below "Connect", turn on Coolers. Set cooler set point with the Cooler button specific to each camera.

24. Click "Toggle Observatory Control" (Ctrl + T).

25. In the Setup Tab, check that under Telescope it reads "TheSky-controlled telescope" and that Focuser 1 reads "RCOS TCC".

26. Click "Connect All".

27. The telescope can be controlled under Observatory-Telescope (nudging or setting coordinates), set to specific objects through Observatory-Catalog, or moved through TheSky. Manual control of the telescope is possible with the joystick, but will confuse the dome.

Taking Images in MaxIm DL

1. Wait until sensor temperature reaches set point under Camera Control-Expose.

2. Under Camera Control-Expose, set exposure time and frame type for a single frame. Hit start. Single frames must be manually saved and will be deleted once the next image is taken.

3. Use Autosave to take multiple images. Enter an autosave file name. Use different Slots for images with different settings. Click slot number buttons, and select exposure type and a suffix to distinguish between multiple slots. The Repeat box controls the number of frames taken.

4. The image save path can be found under Options, on the right of the box. Images should be saved to the Z:\ drive, and Auto-Subfolder should be checked to save images by date taken.

5. Click Save and make sure to hit Start under the Expose tab.

6. If two cameras are connected, switch between them by selecting camera 1 or 2 next to the binning information.

Disconnecting and Shutting Down the Telescope


1. Under Observatory-Setup, click Disconnect All.

2. Under Camera Control-Setup, turn coolers OFF and Disconnect.

3. Close Maxim DL.

4. In TheSky, home the telescope under Telescope-Options-Find Home (or double click joystick) and then terminate the link with telescope by clicking the red telescope icon.

5. Make sure the dome is Homed, then exit DDW and hit close when the Pin settings window pops up.