First, read this memo and be sure that you agree with the terms.

If you do, contact the Instrument PI (Matt Bershady, mab@astro.wisc.edu, 608 265 3392) to reach an understanding and agreement on what science program SparsePak will be used.

Finally, email the appropriate letter of request listed below to the WIYN or KPNO Director well before your observations. Email the WIYN Director if you are a WIYN-consortium user. Email the KPNO Director if you are using NOAO time. It is important to cc a copy to the Instrument PI. When he receives this email he will send a similar letter to the appropriate Director, whereupon your SparsePak shared-use will be granted.

Shared-Use Request Letter
WIYN-Institution Time	NOAO Time
Science PI letter - you send this Instrument PI letter - I send this	Science PI letter - you send this Instrument PI letter - I send this
Instructions: fill in blanks and email to jacoby@wiyn.org with cc to mab@astro.wisc.edu	Instructions: fill in blanks and email to rgreen@noao.edu with cc to mab@astro.wisc.edu

• throughput and resolution on half-order points for H-alpha and CaII NIR triplet (6 vs 7 and 8 vs 9).
• relative throughput of Densepak, SparsePak and Red Hydra cables at H-alpha and MgIb (510nm).
• performance in CaII triplet absorption and H-alpha emission on standard stars and nearby, bright galaxies. Samples of CaII triplet data are shown below at a spectral resolution of 21,100 (2.4-3 pixels FWHM)!

  	HD 107328, K0.5 IIIb Fe-0.5, mv=4.96, 10s drift (RV std)		NGC 3982, Sb, B=12,3, 1800s
  	HD 136292, F8 IV-V, mv=5.06, 10s drift (RV std)		NGC 3379, E1, B=10.4, 900s

  
  Here is a properly field-flattened and sky-subtracted comparison of HD 107328, N3982, and the night sky at 860 nm. Note the outrageously good separation of the night sky lines at R = 21,100 (!). The sky spectrum is scaled down by a factor of 10, i.e. the sky continuum at full-moon at 860nm is roughly equal to the source spectrum (I-band surface brightness of roughly 18.5 mag arcsec^-2). Note the solar (rest) CaII absorption lines in the sky spectrum.

  Here is an H-alpha velocity field of NGC 3982 from the second night, courtesy D. Andersen and M. Verheijen.

• On-telescope performance at 515 nm, 660 nm, and 860 nm with the echelle grating: resolution, vignetting, scattered light, sky levels, and comparisons to Densepak and Red Hydra cables. (See this site for on-line information on performance.

• Template library of roughly 30, nearby, bright stars in the 515 nm and 860 nm region with the echelle (orders 11 and 6, respectively). A grid in T and log g was sampled; further observations are required to complete the grid by sampling a wider range of metalicity.

Commissioning run calibration and characterization are in the following two papers:

SparsePak: A Formatted Fiber Field-Unit for The WIYN Telescope Bench Spectrograph. I. Design, Construction, and Calibration , Bershady, M. A., Andersen, Harker, J., Ramsey, L. W., Verheijen, M. A. W. 2004, to appear in PASP (June) (preprint: [local pdf] [astro-ph/0403456])

SparsePak: A Formatted Fiber Field-Unit for The WIYN Telescope Bench Spectrograph. II. On-Sky Performance, Bershady, M. A., Andersen, D. R., Verheijen, M. A. W., Westfall, K. B., Crawford, S. M., Swaters, R. A. 2005, ApJS, 156, 311 (reprint: [local pdf] [ApJS])

• SparsePak tpl
• SparsePak perl script

Source acquisition using the pellicle and pellicle camera:   This hardware is part of WIFOE - the port to which SparsePak and DensePak connect. There are several issues to be aware of when using the pellicle/pellicle camera to place sources onto the SparsePak array. First, the pellicle does not repeat. This means that a fiber position marked with a grease-pencil on the TV is not necessarily valid from one insertion of the pellicle to another. Second, the focus of the back-illuminated SparsePak array image onto the pellicle camera is soft, and variable (probably correlating with IAS rotation, but this has not been quantified). This must mean that when a star is focused in the pellicle camera, it is not in focus on the SparsePak array. The good news is that the fibers are big!

Useful offset patterns:

Array fill -- this 3-point pattern will fill in the aray in the sparses 70x70 arcsec region. Position Relative Offset Absolute Offset 1 0"E 0"N 0"E 0"N 2 0"E 5.6"S 0"E 5.6"S 3 4.9"W 2.8"N 4.9"W 2.8"S	Array sub-sample -- this 3-point pattern will sub-sample the inner region of the array to increase spatial resolution. Position Relative Offset Absolute Offset 1 0"E 0"N 0"E 0"N 2 3.3"W 0"S 3.3"W 0"S 3 1.6"E 2.8"S 1.6"W 2.8"S
Note - these offsets have been updated for the proper plate scale at the WIYN IAS f/6.3 focus of 9.374 arcsec/mm, and rounded off 0.1 arcsec precision. (See WIYN Facts).

How to make offsets:   Between guided exposures, small offsets should be "unguided" for highest precision. This means turning off the guiding, making the small move (or dither), moving the guide box back onto the guide star, and finally "enabling" guiding with a "zero lock." The last step ensures that the guider keeps the star at the location within the guide box where it is placed, i.e. it does not try and drag the star into the center of the box.

Spectrograph Setups & Calibration:   At the present time we have used SparsePak in three wavelength regimes in five orders with the echelle grating (316@63.4), and 2nd-order at H-alpha for the 860 l/mm grating. Thanks are due to Di Harmer and Daryl Wilmarth for carefully establishing the foci and optimum/comprimise camera-grating distances!

The Bench Spectrograph echelle setup parameters, calibration exposure times, and delivered spectral resolution are summarized below. For the echelle, the camera-collimator angle is 11.0 degrees and the fiber focus is -162 (-0.162 inches). For the 860@30.9 setup, the camera-collimator angle is 30.0 degrees and the fiber focus is -212 (-0.212 inches). In all cases: the collimator focal length is 1021mm. Exposure times are for un-binned data although 2x1 is often used for MgI and CaII IRT setups (binning in spatial diretion). For these cases, halve the exposure times. Exposure times for "ThAr" will change until a new, permanent feed is established. As of Jan 2002, the "ThAr: lamp is "CuAr."

Notes - (1) the spectrograph instrument setup parameters apply to any fiber cable, as do the delivered performance in central wavelength and dispersion. (2) Exposure times should scale with the relative fiber area; spectral resolutions should be fairly constant because of the large anamorphic demagnification. (3) The three "low" resolution echelle setups have the same grating-camera distance. This means that rapid switches can be made during the night by only changing filters (alpha and camera focus too -- but from the GUI). (4) Order 7 setups are problematic because of high grating angles. While these yield incredibly high dispersions and large demagnification (hence high resolution), they are difficult to focus over the full range in both spatial and spectral dimensions. There is strong trade between spatial and spectral foci. The high grating angles lead to substantial light loss because these angles are both far off-blaze and so large the grating does not fill the beam. We estimate that order 7 is down by x2 at the 8600 central-wavelength setting and x3 at the 8750 central-wavelength setting compared to setups at the same central wavelengths in order 6. (5) Dewar azimuth angle optimization was tested for Jan 17 2002 run setups for order 6 and 7 centered at 8750. Substantial improvements in uniformity of spatial focus was achieved. Daryl Wilmarth suggests improvements could be made for other echelle setting.

WARNING:   We have found that some fibers (from as many as 1 to 5) appear to "snuff out" during the initial setup of the spectrograph. THESE FIBERS ARE NOT   BROKEN. The cause is the filter blocking some number of edge fibers (at the top or bottom of the SparsePak slit). This arises because the filter has been inserted manually. Another sign that there is a problem is a marked increase in scattered light as seen in a dome flat. A robust solution is to remove and re-insert the filter via the GUI.   Do this as a matter of course, no matter what anyone else tells you. Then check your dome flats. If less than 82 fibers, remove filter and try again.

The easiest way to count the number of fibers is to run noao.twodspec.apextract.apfind on a dome flat, as follows, with these parameters:

Aperture "1" should be on the right side of the spatial profile in the graphics window. It should be obvious from an immediate visual inspection if there are indeed 82 fibers. Note that the vignetting for the edge fibers should put their amplitude no lower than 50-60% of the central, peak fibers.

Otherwise, counting fibers by hand is painful. If you must: Using an "l" (spatial) cut in imexamine fiber 1 is at high pixel x values and fiber 82 is at low pixel x values. Fiber 37 can be identified as the anamalously low fiber found near the middle of the slit. If xstart=450 and xsize=100, cutting near the middle of the dispersion direction of a dome flat (y = 1024) puts fibers 1, 2, and 3 at pixels (x) 159, 169, and 180 respectively.

• the x pixel coordinates of fibers 1 and 82 (use ``j'' in imexamine of a dome flat);
• a ``raw'' dome flat; and
• an estimate of the bias level (imexamine the overscan region of any image).

``Raw'' spectrum showing 82 spectra, left to right. Shorter wavelengths are towards the top. Ha and [NII] emission are evident, as is a weak sky-line blue-wards of [NII]	Radially ``re-Packed'' spectrum over the same wavelength range; the seven sky fibers are at the left edge.	``Re-Packed'' spectrum showing strong sky lines

Repacking .ms files   Because of both the of the complex nature of the mapping of the fibers from the telescope focal plane to the slit, it is difficult to interpret the extracted spectra, as output from, e.g., dohydra. This output is an "ms" file, i.e. an 82x2067 image, where each row is the extracted spectrum corresponding to fibers 1 to 82, respectively numbered according to the fiber position in the slit-block. One solution, suitable for a quick-look at the data, is to re-stack the spectra into meaningful orders. A simple iraf script and support files can be found here as part of an IRAF package named "ifupkg." Down-load this package and install it via an entry in your loginuser.cl. The script "repak.cl" allows you to take the output ms file from dohydra and repak the fibers so that they are ordered either radially (rad) outwards from the central fiber (#52), or stacked by rows oriented at a variety of position angles (pa[x]). The packing symmetry of the fibers allows for PAs of 0, 30, 60, 90, 120, and 150 degrees. The radial repacking is useful for inspection of S/N as a function of radius. The PA packing is useful for making a quick check on, e.g., whether the source has rotation, and a rough estimation of the position angle. Here's an example:

raw ms	rad	pa0	pa30	pa60	pa90	pa120	pa150
								NII Ha NII

For this source you can plainly see there is the least coherent spatial gradient is for PA near 90d (pa90), perhaps slightly offset towards PA of 120d. The kinematic major axis is there 90d offset from this PA, or roughly 10d. This agrees to within 10d of the value determined from a tilted-ring fit to the velocity field.