MOSFIRE Observers Guide


Is there an exposure time calculator?

Yes, a preliminary one can be found here:

This is a *beta* calculator, please report mistakes to npk@astro.caltech.edu.

Uncategorized Questions
1. How long does an observation take?
Configure CSU in alignment mode while slewing telescope and w/ dark filter in
300 s
Select filter for alignment60 s
Use the Slit Alignment Tool (SAT), acquire guider image, select alignment star, perform telescope offset30 s
Use SAT to take a sky image, nod telescope and take alignment image through mask60 s 
 SAT will predict & calculate rotation60 s
 Verify alignment60 s
 Configure CSU to science version45 s 
 Configure turret from imaging mirror to spectroscopy grating45 s
 Expose, up to user20 min 

 Swap filter and move grating     45-60 s

     The above table was adapted from the MOSFIRE Pre Ship Review Report Page 175 and was written by Chuck Steidel.


2. What is the spectroscopic field of view of MOSFIRE?

MOSFIRE's spectroscopic field is 6.1' by 3' and indicated by the green rectangle in the image below:

MOSFIRE's imaging field is the area that is covered by the blue circle and red square. In imaging mode the corners of the chip (red square) will not be illuminated. 
    -- Image is from page 32 of the pre ship report.

3. Where is MOSFIRE's Guider Relative to the Imaging Field?
The left hand side of the image above shows the optical relationship between the on-axis science and off-axis guider fields. The image on the right shows the front window (bottom; gold) and guider front lens (labeled as GUIDER). The guider is a frame-transfer CCD with RG780 filter. -- From PSR pg 33

4. What is the filter complement?
For spectroscopy, MOSFIRE has Y, J, H, and K filters, with the filter curves shown below:

In addition to the spectroscopy filters, MOSFIRE has several imaging filters: a Ks filter (curve shown above); and a J2, J3, H1, and H2 filter curves shown below. In addition, the J2 filter covers a region of wavelength space between Y and J that might be useful for some observers.

5. How many new masks can I observe in a night?
This is somewhat uncertain, but may be limited by the duty cycle of the mask-creation mechanism (CSU) during afternoon wavelength and flat calibrations. You are safe with under 10 new masks per night, and less than 15 is probably OK. We will learn more during commissioning.

Please let me know if this poses problems and we can discuss your particular application.

6. What does the grating mechanism look like? Why does it take so long?
The mechanism rotates a large and heavy device to micron-level precisions. The operation of the mechanism can be seen by clicking on the picture below:


The grating is the octagonal object.

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