imacs multi-object echelle b. sutin, t. hare & a. mcwilliam & many others n *not yet...
DESCRIPTION
● Grating + Prism cross-disperser in grating module ● Grating: 245 l/mm, 37-degree blaze?,160x214mm ( 20% overfill loss) ● Prism: fused silica, 13-degree apex angle,300x200mm, 63mm baseTRANSCRIPT
IMACS Multi-Object Echelle
B. Sutin, T. Hare & A. McWilliam & many others
N
*Not yet released
*
● IMACS Multi-Object Echelle (MOE)
F/4 focus
● Grating + Prism cross-disperser in grating module
● Grating: 245 l/mm, 37-degree blaze?,160x214mm (20% overfill loss)
● Prism: fused silica, 13-degree apex angle,300x200mm, 63mm base
MOE Characteristics ● Wavelength range: (10 orders)● ~10-100 objects● Resolving power (0.6 arc sec): R=21,000● Slit length: 5 arc seconds● 15x15 arc min. field● ~900 counts/pixel in 1hr at H for V~17.0
(~1400 counts/pix/hr at 7600A)● Cost: Parts~$35K, Labor~$20K
10 13
4
MOE Engineering
● October/November 2004
● Th-Ar lamp system installed & calibrated
● Problem #1: mechanical clash! (-3mm) IMACS model off by 9mm Solution: move prism
Slide the prism down. Minimum distance now 1-2 mm.
MOE Engineering● Problem #2: very tight fit
Solution: move cables & mill the prism mounting
● Problem #3: spectral clash! Design “feature” of grating roll Solution: unique software for mask cutting (empirical vs predicted)
● Problem #4: some spectra fell between CCD gaps Solution: software
MOE Engineering
● Problem #5: blaze not centered on CCD Design flaw or grating blaze 3 degrees off Solution: in progress
Off-center Blaze for central object
H
O2 B-band
Carina star #1386 V=17.88 (1 hour exposure)
Object at edge of field
H
O2 B-band
Carina Star # 1107 V=17.79
MOE Science● 1st Science/Engineering run Dec. 2004● Collaborators: A.Koch (Basel) & V.Smith (Gemini)● Carina dSph mask 20 objects 12 hrs● Fornax dSph mask 20 (10) objects 8 hrs● 4800-7800A blocking filter (4 orders)● 1st night seeing 1.1'' fwhm● Problem?: Nod & Shuffle mode
Solution: software
H
EuII
NiI
FeI
FeIFeI
VI
CoI
Chip #2
Procedural difficulties
● Re-alignment, after each exposure, results in a shift of the spectra on the array; requires quartz spectra to be taken each time MOE is moved.
● Number of spectra: 20 obj x 4 orders x 4 ccd x 12 exp = 3840 spectra => Pipeline reduction required
Summary
● MOE works, but the blaze problem needs to be resolved.
● Pipeline reduction is essential.● MOE complements MIKE and MIKE+fibers.● MOE can compete with VLT/UVES+GIRAFFE
and enhances our ability to study the chemical evolution of nearby systems.