Mapping Extended Targets (ie. Nebulae)

This manual will describe what I consider to be the best way to map an extended target in increments of 1'' above and below the central position.  This process is somewhat more involved than most operations so please read these instructions carefully.

• Pick your Position Angle (PA) and rotate the instrument.  If you intend on creating a data-cube, it is best to position the slit North-South (PA=0 or 180) or East-West (PA=90) since there is no need to rotate your astrometric solution when combining the pointings into a data-cube.
• Set center finding algorithm to 2D Gaussian(M) Fitting, since we are going to be using off slit guiding.
• Center your target directly on the reference position.  Repeatedly click on target and then click "Go R" if necessary.  This may take a few tries since the telescope tracking isn't perfect.
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• Click on guide star
• Choose "Sel G"
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• Click "Set Reference Ready To Guide"
• Center the A position directly in the middle of the slit by setting dA SL=0, SW=0.  This will be the central position for your map and a good way to check that your pointing is good.
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• Set B position to be your initial offset along the slit width.  This will be in the opposite direction that you set B to.  For example dB SL=0, SW=-1 will place your slit 1'' North from the central position. 
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• Click "Move A"
• Click "Start Guide Box".  This starts your first exposure on the central position once the target.
• Start exposure.
• When exposure is done, click "Stop Guiding."
• Move to B position for the first offset from the center.

• Move to A positon, this is important because we are going to change the B position but the A position should always stay in the center of the slit.  Always move to A before changing the B position to avoid any 
• Change B position to second dither SAY EXAMPLE
• Move to B position
• star exposure
• Stop guiding
• Move to off position and take off exposure

• Plan to take your dithers in sets.  Typically to save time you should share OFF positions between sets of dithers.  The patter will be like….
  • TALK THROUGH EXAMPLE
    
    
• Continue taking sets of dithers until your reach your desired +/- X''
• For example here we are targeting 7'' South of our target
  • INSERT IMAGES
• Grab your A0V standard star before, after, or half way through your observations.
• Congratulations you have made a map!