BGSU 0.5-m Telescope + CCD Camera for ASTR 3090

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Basic Observing Procedure Outline

Starting Up:

1) The CCD PC in the control room should be shut down when you arrive (power light dark, no effect from typing on keyboard). If the PC is on, shut it down and wait till the light goes dark.

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

Go to the dome and plug the CCD cable into the CCD -- be gentle, hand-tighten the screws on the connector.

2) Boot up the PC by pushing the power button on the front of the PC tower. Do Control-Alt-Delete and log in using the ASTR 3090 account and password, making sure to select "A061933 (this computer)" rather than "BGSU".

3) Start the CCD program by double-clicking on the "Shortcut to MaxIm_DL 5" icon on the desktop.

4) Initialize the CCD camera (Setup: Camera 1: Apogee PCI/ISA; No Filters; then click Connect).

5) Open the telescope as usual following the procedure sheet handed out in class, and zeropoint (initialize) the telescope coordinates on a bright star as usual using the visual eyepiece (so future targets land near the center of the CCD).

6) In the dome, slide the visual eyepiece all the way to the right and tighten the thumbscrew gently (if you forget this step, the eyepiece pick-off mirror will partially block the CCD!). Set the telescope focus to the default CCD value (in 2015 it was 2433 units). Turn off all lights in the dome, including the reticle lights.

Observing:

7) 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.

8) In the "Camera Control" window, select the Expose tab. In the "Options" menu , select No Calibration (I'll explain what this means in class).

9) Point the telescope to your target object and observe the object. Note the observation (especially the file name of the image!) in your paper log. If you get a blast of stray light, you probably left lights on in the dome; the reticle lights should be off too.

10) Repeat Step 9 until you are done, it is dawn, or it clouds over.

Shutting Down:

11) Select the Setup tab in the "Camera Control" window, and click the Disconnect button.

12) Use the File menu to Exit the MaxIM_DL program

13) Shut down the CCD PC computer, and wait till it is completely shut down. You can finish up your paper log and do steps 14-15while you wait. Unplugging CCD cable when PC is on will damage CCD, listen for fan sounds while in the dome!

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

15) Slide the visual eyepiece back to the center position (7.5 on the scale) and set the focus to the default visual focus value (in 2012, it was 2487). This is a courtesy to the stargaze staff and all eyepiece observers!

16) Double check the CCD PC to ensure it has fully shut down (light off, keyboard unresponsive). In the dome, listen for fan sounds. If they are quiet, unscrew the CCD cable connector screws and gently remove the connector. The CCD cable should hang from the "dog leash" and not drag on the floor.

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

18) 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 (laydena (at) bgsu (dot) edu) if you have any trouble or questions.
• Phone me at home (#s by light switch in control room) if it is before 11pm, 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, now out of stock).
• Online manual for MaxIM_DL including useful tutorials.

Updated 2016 Nov 16 -- 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 "Camera Control" window by clicking on the button icon on the toolbar (7th from the left).

• Select the Setup tab.

2) The box along the left of the window should read:

• Camera 1
• Apogee PCI/ISA
• No filters

If these do not appear, let Andy know ASAP (by phone if before 11 pm, see #s above light switch); DO NOT PROCEED if these are set wrong!

3) The center box should read:

• Camera 2
• No camera
• No filters

4) When all is correct, click Connect to initialize the camera and filter wheel.

Updated 2016 Nov 16 -- 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.

In practice, exposure times longer than about 300 sec (5 min) are not advisable. The telescope tracking is not perfect, and the sky will slowly "drift" across several CCD pixels, leaving "trails" on the image. Also, the background skylight (artificial lighting, moonlight, etc) will raise the background counts too. If it is more than about 1000 counts, lengthening the exposure time will do you little good.

One trick for getting clearer images is to take several (3-9 or more!) images with shorter exposure times, then "stack" them (essentially add them together while detecting and removing bad pixels and cosmic rays): see the tutorial on p.23 of the MaxIm manual.

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

1) In the "Camera Control" window, select the Expose tab. The ensure the following parameters are set:

• Exposure Preset = Find Star
• Readout Mode = Normal
• Subframe On box should not be checked
• X Binning = 1
• Y Binning = Same
• Single image radio button should be selected.

2) 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 Start button to take the image.  You will see a timer bar appear while the shutter is open and the CCD chip is being exposed to light, then "Downloading" as the digital image is transferred from the camera to the computer.

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; guestimate proportional shifts N/S and E/W).
• 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 withT_exp = 10 sec (or 100 sec if this is your second test).
  • If there are more than 12,000 counts, the object is too bright 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 may need exposure times longer than 100 sec. You can experiment to find what the longest practical exposure time is: probably 300 sec, but it will vary with sky brightness and airmass (the telescope tracks more accurately when it is near the meridian)... play around and do the best you can!

5) Save all the images you want to keep by clicking the diskette icon (2nd button from the left on tool bar):

• Navigate to your directory (MyDocuments\Astr3090\Yourname) using "Up One Level" button,
• Choose Save as type = "FITS Image" from the menu,
• Type in a File name (for example, M31_100s might work for a 100 sec image of M31),
• Click the Save button (the file gets a .fit extension name to remind you it is in FITS format).

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 2016 Nov 16 -- ACL