How to put a star in the Lucifer Long Slits

Here's the idea:

  • Your script takes two direct images offset from each other and you difference them, to either (1) see the object you want to observe, or (2) see the star you will offset from if you are doing a blind offset. If you are doing a bright telluric standard you can probably see it in one image and don't need to difference.

  • Your script pauses.

  • You put one of the direct images into the bias buffer in Skycat

  • You stick in the Mask to FPU with your long slit and manually take another image. Stick this image into another bias buffer.

  • Difference the direct images and find your star in the Skycat display

  • Start SHIFT IMAGE sequence.

  • Identify the star

  • Subtract the slit image

  • Identify the center of the slit at y=1024 pixels. The x,y offsets will be computed, in the lower left corner of the Telescope Control gui.

  • "Commit" the x,y offsets if you are happy. This puts the star you identified in the slit.

  • You can take another image manually if you want to see if the star is really in the slit. You can skootch the star in the slit one way or the other with the "Offset in arcsec RELATIVE" box. Positive x moves the star to the right in the Skycat display.

  • Now continue your script, which may do the blind offsets if you want a blind offset.

  • Now take spectra

The rest of this page needs editing

Mask to Position Mask in FPU and Start READ

Turn on Flex compensation

In Telescope Control:



Go back to SKYCAT, click on the star in the direct difference image (which is image 2 - image 1)

In SkyCAT, pull down GO to the slit image

Zoom in by clicking on zig-zag buttons

Click on a position in the slit you want the object to be at. Remember that you want the star offset from the center row of the detector, which is funky.

4. Go back to the Telescope Control Gui and See what offset will be done

At the lower left, there is a box which should show a number, next to


This is the offset.

Place cursor in x,y offset box. Then click COMMIT

5. Start your long slit observations.

find your script, say myscript.txt

luci myscript.txt

J. Bechtold, F. Bian, E. McLinden Jan 2010. Revised Jill B March 14, 2011
Topic revision: r3 - 14 Mar 2011, XiaohuiFan
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