MIKE Fibers Overview
OVERVIEW OF THE MICHIGAN MIKE FIBER SYSTEM (MMFS) Mario Mateo (mmateo @ umich . edu) November 2006
- The Michigan/MIKE Fiber System (MMFS) is available for general use by
the Magellan community with support provided by UM. The system has the
following basic features:
- 128 "Red" Fibers that
feed the red camera of the MIKE spectrograph.
"Blue" Fibers that feed the blue camera.
for interference filters to isolate specific orders on both the red and
blue sides. Available filters include Mg (around 5180 Å, one tuned for
the red side and one tuned for the blue side), H-alpha, red order 56
(about 6140 Å), and the Ca IR triplet. The current filters isolate
single orders, but multi-order operation is possible. Interested users
should contact M. Mateo (mmateo @ umich . edu) to inquire about
these keeping in mind that new filters require money (a kilo-$ or a
few), and a lead time of about 8 weeks. Single order coverage is about
delta-lambda/lambda ~ 0.01. Multi-order observations -- at the cost of
total number of targets per field -- can cover a range of up to
- 1.4 arcsec diameter circular
apertures for each fiber.
- Minimum separation
between fibers of 14.5 arcsec.
- Fiber access
via plugplates to a 20-23 arcmin diameter corrected on the Nasmyth-East
focus of the Clay telescope. Since Clay lacks a wide-field corrector,
the full 27-arcmin field is likely only available for relatively bright
- System throughput is strongly
filter/order dependent, but observations so far indicate that the system
delivers 1 photon/sec/Angstrom at V=17.2 in the Red fibers, abd 1
photon/sec/Angstrom at V=17.7 with the Blue fibers at about 5180 Å.
Throughput is highly seeing-dependent; the values above refer to about
0.8 arcsec seeing. Considerably better seeing gains about a factor of
1.5-2.0 over the realistic range of good seeing at Clay.
- All 256 fibers can be used for observations between
approximately 4800 and 5250 Angstroms since there is no dichroic in use
with the fibers. Only blue fibers can be used below 4800 Å, and only
red longward of 5250 Å.
- The user is the fiber
robot; new users will be thoroughly trained in this process. Experience
shows that competent observers can plug 128 fibers in approximately 20
min. Plugging time for all 256 fibers is approximately double or a bit
longer. Two people can plug fibers simultaneously, shortening the time
- Repeatable exposure
times are limited to longer than about 2-3 second, with a shutter
latency of about 0.2 seconds.
- Th-Ar and Th-He
comparison lamps are available for calibration. This combination should
ensure that every order is devoid of excessively bright comparison
lines. Arc exposure times of 60 sec are likely required for most
- The effective resolution with the
fibers is approximately 70% that of MIKE direct with a 1 arcsec slit, or
about 15,000 in the Red and 19,000 in the Blue. The 175 micron
diameter fibers project to about 6-8 pixels on the Red and Blue CCDs.
We recommend binning the CCDs 2x2 or even 3x3 in normal use. A slit
assembly to be located at the fiber ends to increase resolution, but
this is not yet available and would only be built if demand warrants.
- MMFS has an integral Shack-Hartmann mask that
allows normal Shack-Hartmann updates to the primary mirror IF a bright
star is positioned at the field center. If no such star is available or
desired, the SH system can be used to focus the telescope during fiber
observations by offsetting to a bright star periodically. This has been
shown to work for 30-60 minutes depending on location of the field
relative to the zenith (worse near the zenith).
is carried out with two coherent fiber bundles that are positioned at
the locations of two suitable guide stars. Auto guiding is available,
though manual updates are required to tweak rotator errors (if any)
during fiber observations. Such guider errors have so far been
negligible in observations carried out to date.
to 8 stars can be used in each field as "acquisition targets", allowing
one to quickly set up on target fields (typical time is ‹ 5 minutes).
- Any potential users should ensure that they
have relative astrometry good to ± 0.1-0.2 arcsec and that they are
certain a suitable order isolation filter is available for their
program. Plug plates cost approximately $100 each, plus about $200-300
for machining. Up to three and possibly four fields, each consisting of
256 fiber positions, can be drilled per plate, particularly if the
entire FOV is populated more-or-less uniformly with targets. Users must
plan to cover the cost of the plates and for machinging the fiber holes
(the $200-300 per plate cost). Astrometry should be available at least
TWO MONTHS prior to the start of any MMFS observing run.
- Software for designing plug plates is available. Please
contact MM for details.
If you are interested in using MMFS, please contact Mario Mateo (mmateo @ umich . edu) for further details.