UGA OBSERVING GUIDE

The Short Version

J. Scott Shaw Jan 2005

I. Preparing for an Observing Run

1) Preliminary Work

Before arriving at the observatory it is wise to construct a timeline for each night, denoting the UT and local time AND the corresponding sidereal time.  A convenient way to do this is to go to the UGA observatory homepage (www.physast.uga.edu/~star/) and link to the daily phenomena.  Locate the appropriate dates that you have scheduled telescope time and read off the important information.  Mark on your timeline the time sunset occurs, the end of astronomical twilight, Moonset or Moonrise, morning twilight and sunrise times in both local and Universal times.

Next schedule your targets so that you observe the sources that are in the west first since they are going toward larger hour angles (HA).  It is best to schedule sources as high in the sky as possible (minimize HA), and this can be determined by the relationship HA = ST - RA.  It is imperative that low declination sources be observed at small HAs!

2) At UGA Dome

Be sure to arrive at the Observatory early enough to check out observatory functions before your run.  It takes about 30 minutes to open up, so if you want to start as soon as the twilight allows, arrive about 45 minutes after local sunset.  Make sure all computers are up and operating properly and the status of the telescope is correctly reflected in the ACE window.  (For instance, if the telescope is pointed toward mirror cover park, but the ACE software thinks it is at Zenith park.)  See OPEN -UP procedures to start observing.

II. Operation of the Camera

1) Start -up NOTE that MaximDL has a full set of tutorials available with the ? button

1.     Log in as scope with the appropriate password.

2.     If MaximDL is not loaded double click it icon, then the CCD icon 7th from left). and choose the Setup tab

3.     If the Main CCD window has just the camera name in it, click the Connect button

4.     If the cooler is not on click it on.  Check the CCD temperature.  If it is not -10 or so check the cooler on box and put -10 to -15 in the 'New(C)' window.  The camera will do a lot better when it gets to -10 or so.  It takes about 15 minutes to do this so you might make sure the camera is cool before opening the telescope.

5.     There are many options on how to use Maxim DL. For example, look under the Settings tab in the CCD control window.  You may use only part of the 1024x1024 CCD by changing the offsets and width and height, or you can bin the pixels (sum adjacent pixels).  However, we usually just take the whole image so the only option of interest here is the calibrations choices.  Do not choose full calibration.  If you are willing to have the camera take a dark frame and subtract it from your picture [this takes twice the exposure time] then your resulting image will have a lower background.  For most purposes None will do fine.

6.     Now go to the Sequence tab.  First choose where you will store your images by opening Options>  then ‘Set Destination Path’.  If you don’t have a folder make one. Choose your folder then say OK.  If you ever get a chance to pick Overwrite DO NOT choose it. You could wipe out data.  If you are doing a sequence of observations stay in this window and enter a name in the Filename window. For example the name of the object with maybe some date information.  You then have to go through Options> again  and Setup sequence to choose the type of image, filter, and number of repeats. "Start at' indicate the sequence number that will be added to what you put in the Filename window.  So if you put Jupiter in the Field name window and 5 in the Start at window then you exposure will be named Jupiter005.  The next exposure will be Jupiter006, etc.  To start the sequence click the Start button.   Anytime you wish to stop the sequence click stop,  If you are taking one exposure at a time then click the Expose tab.

7.     To expose go to the Expose tab, set the time of exposure, choose light, dark, bias or flat click expose.  If you get an exposure you like you can name it and save it.  You can tell if the exposure is saved by looking at the top of the image window for the name you put in.

8.     The final set-up that is needed is to select the proper image display size.  To do this: click on View and zoom in or out as you need.

III. Observing

1) Calibration Images

If you are taking research quality data refer to 'How to take calibration images'.

2) Verifying Pointing integrity.

Pick out a bright star (mag. ~ 3.5-4.0) relatively close to your intended target.  Enter its coordinates and epoch and initiate a move to this target by clicking on the green GOTO button.  A dialog box appears in the center of the screen that reports the intended move location.  If everything is correct and acceptable, click on move telescope in that box.  As the telescope moves, the green GOTO button will be replaced by progress bars.  The top one is for RA and the bottom one is for DEC.  When the move is completed, the progress bars disappear and the GOTO button returns.  Use the Paddle to center the star on the crosshairs of the eyepiece. 

If the star is not a fairly condensed point of light you may need to focus the telescope (See below)

Now flip the mirror out of the way and take a CCD image.  You probably do not want to save these images, and the exposure time will likely be around 0.1 or 0.5 seconds, depending on the brightness of the star.  If the bright star is not in the field, check to make sure you 1) have the flip mirror out of the way and 2) have the CCD shutter open.

NOTE: The normal camera display has North to the top of the image and East to the left of the image.)  You can center the star either using the soft hand-paddle or by using the offset mode in the ACE screen.  If you use the soft hand-paddle, be sure the "set" is selected instead of "guide" and the set speed is "60".  For every arc minute, depress the appropriate directional button for 1 second.  Take further images and make further corrections until the star is centered, then under the telescope menu, choose reset encoders.  You will be prompted as to whether you really want to reset encoders and choose appropriately.

If you have trouble finding your bright star use the setting circles.  The declination wheel reads 0.3° too high.  The Hour Angle = Local Sidereal Time = Right Ascension.  Local Sidereal Time is displayed on the ACE screen

3) Focusing the Telescope

The simplest way to do this is to put a bright star in the wide field eyepiece and use the two focus buttons (mounted on the telescope on a small aluminum box).  The focusing is done by a small motor moving the secondary mirror very slowly so you have to hold the button down quite a while to see any effect.

For a better focus you may use the CCD and a bright star; however, you need to make sure you are not overexposing it.  If the start is 4th magnitude or fainter, then an exposure time of .5 or longer with most filters is acceptable.  Once you have moved to the focus star, you may focus in any filter. Choose an exposure time and take an image.  If this overexposes the star, decrease the exposure time until it is not over exposed.

Then proceed by holding down one focus button for about 5 seconds.  If the image improves keep using that button in 5 second intervals until it gets worse.  Then switch to the other button for 5 seconds.  You will reach a place that neither button seems to make much difference.  This is as good as the focus gets.  If the images are 4-6 pixels wide at FWHM you are doing well for our site. While you can focus the visual eyepiece to see the star better this will NOT focus the telescope on the CCD.  Once you have a focus on the CCD you can focus the eyepiece.  Later if the telescope gets out of focus you can use the eyepiece and the focus button to focus the telescope.

You can also use the focus in Maxim.  This will continuously expose the camera as you use the focus buttons.

4) Moving To a Target

Enter coordinates of your object in the ACE coordinate box.  If ACE is in offset mode or H.A. mode, then click the RA tab so that the RA-DEC windows appear again.  Remember to use 2000 for your epoch

The Object selection feature allows you to have a TOF file in which the name, coordinates, and epoch of your objects are stored.  To create this file, one needs to place the cursor in the object selection window and depress the right mouse button.  A small window with options to open a database or save a database appears.  Select Open Database and a window comes forward which lists the .tof files that are already stored in the ACE directory.  Click on the appropriate database if it exists and click on open.  This will open the database in the ACE window.  If you have yet to create a TOF file for your project, you can do that by typing in the name, coordinates and clicking the Add button.  Once you have entered the Name, RA, DEC and epoch, click "add" and it will be placed in your file for future use.  Now click on the green "GO" button.  You can save the database by again depressing the right mouse button in the object selection field and choosing Save Database As.

Once the proper coordinates are inserted in the RA box, click on GOTO and the move window pops up with the coordinates to which the telescope will slew and the air mass.  Always check the airmass to see if it is reasonable.  Although the ACE code prevents you from making certain moves to very high air masses, it is always better to check.  ALSO, DO NOT MOVE TO DECLINATIONS GREATER THAN +65 OR LESS THAN -30!!! Take a quick CCD image to make sure you are properly centered in the desired field.  If not properly centered, center it using either the soft hand paddle, or "offset"

5) Changing Filters

If you want to take images in different colors, click on the Instruments option at the top of the ACE screen and a menu will appear.  Select the filter wheel tab and there will be a list of UBVRI filters along with an empty space.  Click on the small circle to the left of the desired filter and it will rotate into the optical path.  The status box in the left hand side of the ACE display tells you the filter wheel is moving and which filter it stops at.

IMPORTANT: The filter wheel may not remember where the filters are.  You can test this by moving to empty and taking an image.  The star image should be noticeably out of focus.  If the filter selected is empty, and you have focused images there may be a problem with filter wheel initialization.  If you do a filter initialization the power panel on the telescope next to the focus buttons must be on.  Go through the entire filter wheel until you find the out-of-focus position and that is the empty slot.

6) Ending the observing session

To end the observing session, move the telescope to the zenith with drive off.  Verify in the ACE window that the RA drive is off and that the telescope is in the zenith.  Important!  If there is no one scheduled for the next night warm the CCD by turning the CCD cooler off. Leave all computers up and running.

Cover the mirror and the finder.  Close the dome.  Turn out all lights.

IV. IMPORTANT PHONE NUMBERS

Emergency Numbers  9-911

UGA police 542-2200

JSS Home 353-2614      Office 542-2870