Masks
Facility Masks
Each MODS reserves the first 12 mask slots for the standard facility slit masks which includes imaging stops, segmented long slits, and calibration masks that are always available in each MODS instrument. MODS1 and MODS2 are nearly identical, although MODS1 contains a DarkMask in slot1, while this slot contains the 0.6 arcsec long slit in MODS2 due to slot 5 not being usable. The gerber files (input files for the Mask Manufacturing Unit, see below) are also included for the standard facility masks. To view them you will need an application that can open gerber files, such as Cuprum (free version available).
Position | MODS1 MaskID | MODS1 Description | MODS1 Partner | MODS2 MaskID | MODS2 Description | MODS2 Partner |
---|---|---|---|---|---|---|
1 | DarkMask | Blank mask for a dark block | Facility | LS5x60x0.6 (Gerber) | 0.6-arcsec segmented long-slit | Facility |
2 | SieveMask (Gerber) | Pinhole imaging sieve Nr3 | Facility | SieveMask (Gerber) | Pinhole imaging sieve Nr3 | Facility |
3 | Imaging | Empty frame for imaging stop | Facility | Imaging | Empty frame for imaging stop | Facility |
4 | LS5x60x0.3 (Gerber) | 0.3-arcsec segmented long-slit | Facility | LS5x60x0.3 (Gerber) | 0.3-arcsec segmented long-slit | Facility |
5 | LS5x60x0.6 (Gerber) | 0.6-arcsec segmented long-slit | Facility | NOT USABLE | NOT USABLE | |
6 | LS5x60x0.8 (Gerber) | 0.8-arcsec segmented long-slit | Facility | LS5x60x0.8 (Gerber) | 0.8-arcsec segmented long-slit | Facility |
7 | LS5x60x1.0 (Gerber) | 1.0-arcsec segmented long-slit | Facility | LS5x60x1.0 (Gerber) | 1.0-arcsec segmented long-slit | Facility |
8 | LS5x60x1.2 (Gerber) | 1.2-arcsec segmented long-slit | Facility | LS5x60x1.2 (Gerber) | 1.2-arcsec segmented long-slit | Facility |
9 | LS60x5 (Gerber) | 5.0-arcsec spectrophotometric long-slit | Facility | LS60x5 (Gerber) | 5.0-arcsec spectrophotometric long-slit | Facility |
10 | PinholeSlit | Pinhole Slit | Facility | PinholeSlit | Pinhole Slit | Facility |
11 | Pointing Mask | MODS Pointing Mask (40″) | Facility | Pointing Mask | MODS Pointing Mask (40″) | Facility |
12 | LS5x60x2.4 (Gerber) | 2.4-arcsec segmented long-slit | Facility | LS5x60x2.4 (Gerber) | 2.4-arcsec segmented long-slit | Facility |
Installed Custom Masks
The remaining 12 mask slots are available for custom-designed mask from our users, and are inserted and removed according to demand. Below are the currently installed masks.
Position | MODS1 MaskID | MODS1 Description | MODS1 Partner | MODS2 MaskID | MODS2 Description | MODS2 Partner |
---|---|---|---|---|---|---|
13 | 531956 | mods.3.g20d25ep2.mms | LBTO | 531956 | mods.3.g20d25ep2.mms | LBTO |
14 | Do Not Use | Do Not Use | Empty | Position Empty | ||
15 | 531713 | mods.2.g00d25ep.mms | LBTO | 531713 | mods.2.g00d25ep.mms | LBTO |
16 | Pointing Mask | MODS Pointing Mask (108″) | LBTO | Pointing Mask | MODS Pointing mask (108″) | LBTO |
17 | 532732 | mods.4.g04d25ep.mms | LBTO | 532732 | mods.4.g04d25ep.mms | LBTO |
18 | 515404 | mods.37.r06d80ep.mms | LBTO | 515404 | mods.37.r06d80ep.mms | LBTO |
19 | Do Not Use | Do Not Use | Empty | Position Empty | ||
20 | 585146 | mods.25.kopo2.mms | INAF | 585146 | mods.25.kopo2.mms | INAF |
21 | Empty | Position Empty | Empty | Position Empty | ||
22 | Empty | Position Empty | Empty | Position Empty | ||
23 | Empty | Position Empty | Empty | Position Empty | ||
24 | Empty | Position Empty | Empty | Position Empty |
Mask table updated: Oct 24, 2024
Masks scheduled to be installed in the near future are listed (requires VPN access):
http://wiki.lbto.org/bin/view/Instrumentation/FutureMODSMOSMasks
Mask Properties and Slit Tolerances
Masks are 230 ± 0.1 mm square to cover a 6 arcmin field of view. The mask curvature contains a 1040mm spherical radius which results in a 12.8mm sag from the center of the mask to the corner. This curvature is so they follow the curved telescope focal plane.
The best image quality is in the 4.5 arcmin diameter circle centered on the field. Outside this central region, the resolution and width of the spectrum will be somewhat degraded. The substrates that form the masks are electroformed on a spherical mandrel with NiColoy, which is a proprietary Nickel-Cobalt alloy used by NiCoForm with a nominal thickness of ~150 microns.
The properties and tolerances of the spectroscopic slits or apertures are summarized below:
Width | 0.15-1.2mm |
---|---|
Length | <10mm (typ) |
Orientation | ±30° |
Shape | Arbitrary polygon or circle |
Width Tolerance | ±15um |
Position Tolerance | ±15um |
Edge Roughness | ±1.8um RMS over 180um |
Masks are often designed with slits packed way too close together, either in the vertical direction, or sometimes in both vertical and horizontal directions. As a rule of thumb, please keep any space between slits (and reference stars) to about 1.8 millimeters (about 3”). If slits are too close, there is a risk of losing the bridge between them, which creates a very oddly shaped slits. If a user is unsure, please contact us (or have the PI contact us) prior to the deadline.
Mask Manufacturing and Laser Cutting
LBTO has a dedicated universal laser cutting workstation (Mask Manufacturing Unit aka MMU), which has been since installed at the University Research Instrumentation Center (URIC) located at the University of Arizona.
The GERBER file is converted to machine code (.pgm file) for the Mask Manufacturing Unit where the blank mask substrate is cut.
Mask Installation
Masks are installed in the instruments internal cassette upon request.
Mask exchanges for MODS are part of daily operations and can be performed for masks on hand on short notice, unlike LUCI which are scheduled well in advance.
A database listing all cut previously cut masks kept on site is available here, for users who desire to use previously cut masks and wish to check the availability.