BGSU 0.5-m Telescope + CCD Camera for ASTR 309

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Procedure Outline

Starting Up:

1) The CCD PC in the control room should be shut down when you arrive. Check that it is my typing on the keyboard -- nothing should happen. If it is on, shut it down. If/when it is shut down, you can go to the dome and plug the CCD cable into the CCD (be gentle, hand-tighten the screws on the connector).

WARNING: Never plug in or unplug the cable to the CCD when the PC is powered up -- you will damage or destroy the CCD!

2) Boot up the PC by pushing the power button on the front of the PC tower. Wait for the PC to boot up.

3) Start the MaxIm_DL CCD program by double-clicking on the "Shortcut to MaxIm_DL" icon.

4) Initialize the CCD camera.

5) Open the telescope as usual, following the procedure sheet handed out in class.

6) Zeropoint the telescope coordinates on a bright star as usual using the visual eyepiece.

7) In the dome, slide the visual eyepiece all the way to the right and tighten the thumbscrew (so it doesn't obscure the CCD!). Set the telescope focus to the default CCD value (2382 units).

Observing:

8) Start a paper log of your observing. Pages are available on top of the PC tower. Be sure to document the sky conditions, moon phase, etc when you begin.

9) In the "MaxIm CCD" window, select the Settings tab. In the "Auto Calibration" field, click the Simple Auto-dark radio button. If you are using exposure times longer than 60 sec, you may want to select the None radio button instead. [Why?]

10) Point the telescope to the coordinates of your target object and observe the object. Note the observation (especially the file name of the image!) in your paper log.

11) Repeat Step 10 until you are done, it is dawn, or it clouds up.

Shutting Down:

12) Close up the telescope as usual following the procedure sheet handed out in class.

13) Slide the visual eyepiece back to the center position (7.5 on the scale) and set the focus to the default visual focus value (2420).

14) Deactivate the CCD: Select the Setup tab in the "MaxIm CCD" window, and click the Shutdown button.

15) Quit the MaxIM_DL program

16) Shut down the CCD PC computer, and wait till it is completely shut down.

17) In the dome, unscrew the CCD cable connector screws and gently remove the connector. Clip the string to the "dog leash" so the connector and cable hang safely off the floor.

18) Record your observing session in the telescope log notebook in the dome.

19) Listen for sounds (fans on CCD?) in dome, shut off lights, close/lock dome and control room doors.

Note: if you have trouble:

• Troubleshooting basic CCD problems.
• Troubleshooting problems with the telescope and/or observatory.
• Email Andy Layden if you have any trouble or questions.
• Phone me at home (#s on bulletin board in control room) if it is before midnight, or if there is a dire emergency.

Here are some links that you may find useful:

• CCD University from Apogee Inc -- more information about CCDs in general.
• Details about specific Apogee CCDs (ours is model# AP6E).
• Image anomalies produced by CCDs and ways to correct them.

Updated 2004 Nov 17 -- ACL

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Initialize the CCD Camera

Note: In order to send and receive information from the camera, there must be a link established between the PC and CCD.

1) If it did not appear already, bring up the CCD control window "MaxIm CCD" by clicking on the button icon on the toolbar (8th from the left).

• Select the Setup tab.

2) The three boxes along the left of the window should read:

• Apogee 1 [CCD]
• No Guider [Guider]
• No Filter [Filter]

If these do not appear, choose them correctly from the drag-down menus (see Troubleshooting).

3) When all is correct, click Restart to initialize the camera and filter wheel.

Updated 2004 Nov 17 -- ACL

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Observing A Celestial Object

Note: The CCD is very sensitive to light -- pointing the CCD at the moon or a bright star or planet could result in permanent damage to the CCD. Never intentionally point the telescope at the moon or a bright planet (Venus, Mars, Jupiter, Saturn) while observing with the CCD! The instructions below describe a safe way of incrementally increasing your exposure time from short, safe exposures to the correct exposure time for your object.

In general, the longer the exposure time you can manage, the more detail will be visible in your picture -- up to a point. If the total number of counts in any pixel gets larger than 16,353 the computer can't handle it, and we say the object is "saturated". In many cases, an ideal exposure level is 10,000 counts for the brightest pixels in your object -- you want to adjust the exposure time to reach this level. Very faint objects like galaxies will probably never yield 10,000 counts, because the required exposure times are too long.

1) Begin here once you have chosen an object to observe and pointed the telescope to those coordinates.

2) In the "Maxim CCD" window, select the Expose tab. Do the following to take a test image with an exposure time of T_exp = 1 sec:

• Enter an exposure time of 1 sec -- this will ensure you never overexpose the CCD too badly.
• Hit the Expose button to take the picture.

3) Inspect the test image:

• Can you see anything? If not, 1 sec is too short: repeat to Step 2 with T_exp = 10 sec (or 100 sec if this is your second test).
• Is the object near the center of the chip? If not, you can move it NSEW using the TCS command OFFSET (the CCD has a 1200x1200 arcsec field of view).
• Is this a good exposure length? Run the cursor around the brightest (whitest) parts of your image and find out how many counts are in the brightest pixels of your object.
  • If there are less than 1000 counts, you will want a longer exposure time: redo Step 2 with T_exp = 10 sec (or 100 sec if this is your second test).
  • If there are more than 16,353 counts, the object is saturated and you will need a shorter exposure time.
  • If it is somewhere in between, compute an ideal exposure length as follows:
    • How many counts are in the blank sky (blackest)?
    • Compute the count difference in counts: object_max - blank_sky.
    • Ideal exposure time = (10,000 / difference) * T_exp.
    • Close the test image (X in upper right corner -- no need to save it).
    • Take another exposure using this ideal exposure time.

4) For faint objects, you will probably need exposure times much longer than 100 sec. You will have to experiment to find what the longest practical exposure times are: probably 300 to 500 sec. You can try to go longer, but I suspect (1) imperfect telescope tracking will result in blurred images, and/or (2) the background sky light will be very high (more than about 4,0000 counts). Faint objects like galaxies are fun and challenging ... play around and do the best you can!

5) Save all the images you want to keep by clicking the diskette icon (3rd button from the left on tool bar):

• Navigate to your directory (C:\CCDImages\A309\Yourname) using "Up One Folder" button,
• Choose File Format = FITS from the menu,
• Type in a File name (for example, M31_100s.fit might work for a 100 sec image of M31; .fit reminds you it is in FITS format),
• Click the Save button.

6) Record comments in your paper log such as Starname, UT/Local Time, Sidereal Time, CCD Temperature, Exposure/Filters, and especially Comments (eg, moon & sky conditions, problems, etc).

Updated 2004 Nov 17 -- ACL