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--- kosmos [2023/07/04 16:41]
jnb [KOSMOS multi-object slit masks]
+++ kosmos [2023/07/04 16:58] (current)
jnb
@@ Line 44: / Line 44: @@
 ===== Aligning the mask and observing =====
+The following is a mask alignment and observing procedure kindly provided by Amanda Townsend.  Holtzman and Burchett are currently developing software to help automate several steps of the mask alignment process, but we advise that observers fully understand the steps involved!
+  - Observer should take slit mask alignment map images (initial can be done at start of night with cals) = dim truss qtz OR internal qtz (or arc) with ND5 filter. Match up alignment map to finder chart with slits, figure out which are which ahead of time to save time later!
+  - Obs spec should set instrument to kimage to keep focal plane same as image. Corollary: do NOT invert images in ds9! This will make offsets very confusing. Rather, invert your finder chart.
+  - Slew to field with rot +90 object.
+  - Take image exposure with disperser = EMPTY and slit = EMPTY to see field.
+  - Match up image to finder chart. Invert finder chart to match if necessary, but again, do NOT invert kosmos images.
+  - For each of the (probably 4-5) alignment/register stars, which are the square slits on the mask, determine the (x,y) coords in the alignment map exposure as well as the (x,y) coords of the star in the image you just took.
+  - Measure x and y offsets for each alignment star: (star-slit)*(plate scale=.258) = offset in arc seconds, find average x and average y offsets for all alignment stars.
+  - Make offsets in TUI Offset window. Select "object arc xy" from the dropdown, and enter x and y offsets. To move star to left = move telescope right = +x offset; to move star down = move telescope up = +y offset. You can also use the nudger (nudger pushes star/pulls telescope).
+  - Start NA2 guider!
+  - Take another field exposure, blink between this image and your alignment map in ds9 to check alignment (and/or check pixel positions or copy regions from one frame to the other).
+  - If they are still far enough off, iterate; otherwise put in your slit mask but NOT the disperser and take another exposure. Look to see where the stars and targets fall in their slits.
+  - Center up the register stars in the squares. Science targets will be off-center in slits for sky measurements.
+  - Put in disperser now. Optional: short exposure to check?
+  - Science exposures!
 ===== Reducing the data =====

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