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IMACS Multi-Object Echelle

B. Sutin, T. Hare & A. McWilliam & many others. IMACS Multi-Object Echelle. *. N. *Not yet released. IMACS Multi-Object Echelle (MOE). F/4 focus. Grating + Prism cross-disperser in grating module

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IMACS Multi-Object Echelle

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  1. B. Sutin, T. Hare & A. McWilliam & many others IMACS Multi-Object Echelle * N *Not yet released

  2. IMACS Multi-Object Echelle (MOE) F/4 focus

  3. 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

  4. MOE Characteristics • Wavelength range: 0.34-1.0m (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 Ha for V~17.0 (~1400 counts/pix/hr at 7600A) • Cost: Parts~$35K, Labor~$20K

  5. 13 10 4

  6. MOE Engineering • October/November 2004 • Th-Ar lamp system installed & calibrated • Problem #1: mechanical clash! (-3mm) IMACS model off by 9mm Solution: move prism

  7. Slide the prism down. Minimum distance now 1-2 mm.

  8. 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

  9. MOE Engineering • Problem #5: blaze not centered on CCD Design flaw or grating blaze 3 degrees off Solution: in progress

  10. Off-center Blaze for central object O2 B-band Ha Carina star #1386 V=17.88 (1 hour exposure)

  11. Object at edge of field O2 B-band Ha Carina Star # 1107 V=17.79

  12. 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

  13. CoI EuII VI FeI NiI FeI FeI Ha Chip #2

  14. 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

  15. 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.

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