The information on this page is for quick reference. Please consult the LMI Users Manual for more detailed information, including filter transmission curves and data.
LMI Filters:
Currently available filters for LMI are given in the table below.
- The value shown under FITS Header will appear in the
FILTERSkeyword of your image headers. - The Pattern String is the LOUI display string you need to use if creating a Telescope Motion Pattern File.
- Focus Offset indicates how much additional focus offset is applied to the Active Optics System to account for filter refraction – it is most helpful for determining which filters are parfocal.
- For taking dome flats (using the CLSD lamps at 12V), an approximate Exptime for 20k counts is provided. For the bluest filters (both broad- and narrow-band), the usual "LMI Lamps" do not provide sufficient flux in the bandpass to easily collect dome flats. For these, a second exposure time is listed using the Photo Floods (a.k.a. IGRINS lamps) on the lamp boom. These are 600-W photographic flood lamps with very short lifetimes – please use sparingly.
- For selected filters, the Central Wavelength and Filter Width (both in Å) are listed.
Sample dome flats for the various filters taken over time can be found on the LMI Filter Characterization page.
| Filter | FITS Header Value | Pattern String | Focus Offset (µm) | Exptime for 20k counts (seconds) | Filter Central Wavelength (Å) | Filter Width (Å) |
|---|---|---|---|---|---|---|
| Non-Filter Positions | ||||||
| OPEN | OPEN | OPEN | 0 | |||
| DARK | DARK | DARK | N/A | |||
| 4 Hole Mask | 4HOLEMASK | 4Hole | ||||
| Johnson-Cousins Filters | ||||||
| U | U | U | +140 | 178 / 4* | ||
| B | B | B | +105 | 9 | ||
| V | V | V | +105 | 5 | ||
| R | R | R | +140 | 3.5 | ||
| I | I | I | +140 | 3.3 | ||
| Sloan (SDSS) Filters | ||||||
| SDSS u' | SDSS-U | SL-u | +180 | 313 / 4.5* | ||
| SDSS g' | SDSS-G | SL-g | +180 | 4.5 | ||
| SDSS r' | SDSS-R | SL-r | +180 | 3.5 | ||
| SDSS i' | SDSS-I | SL-i | +180 | 4.25 | ||
| SDSS z' | SDSS-Z | SL-z | +180 | 3.25 | ||
| Other Broad Band Filters | ||||||
| V+R | VR | VR | +185 | 6091.7 | 1763.9 | |
| Yish | YISH | YISH | +105 | 26 | ||
| General Narrow Band Filters | ||||||
[OIII] | OIII | OIII | +205 | 180 | 5001.7 | 25.5 |
| Hα-On | HALPHAON | Ha-on | +155 | 115 | 6564.9 | 30.1 |
| Hα-Off | HALPHAOFF | Ha-off | +155 | 37 | 6459.1 | 114.6 |
| Wolf-Rayet Filters | ||||||
| WC | WR-WC | WC | +165 | 115 | 4660.4 | 49.5 |
| WN | WR-WN | WN | +160 | 4690.9 | 49.6 | |
| CT | WR-CT | CT | +170 | 4756.1 | 54.6 | |
| Comet Filters (Note: These filters are 4 inches round and suffer some vignetting on LMI) | ||||||
| Ultraviolet Continuum | UC | UC | +175 | 500** / 80* | 3449 | 79 |
| Blue Continuum | BC | BC | +175 | 130 / 3.5* | 4453 | 61 |
| Green Continuum | GC | GC | +175 | 119 | 5259 | 56 |
| Red Continuum | RC | RC | +175 | 70 | 7133 | 58 |
| C2 | C2 | C2 | +175 | 46 | 5135 | 119 |
| C3 | C3 | C3 | +175 | 4063 | 58 | |
| CN | CN | CN | +175 | 480 / 14* | 3869 | 56 |
| CO+ | CO+ | CO+ | +175 | 160 | 4266 | 64 |
| H2O+ | H2O+ | H2O+ | +175 | 7028 | 164 | |
| OH | OH | OH | +175 | 480** / 400* | 3097 | 58 |
| NH | NH | NH | +175 | 3361 | 54 | |
| Assorted Other Filters (inquire if you want to use, as they may not be readily available) | ||||||
| W032 | W032 | W032 | +176 | 5300 | ||
| 5027 | 5027 | 5027 | +130 | 5027 | ||
| K1593 | K1593 | K1593 | +194 | 5010 | ||
** OH & UC counts were at about the bias level for this exposure time using the CLSD lamps at 12V.
* Using the photo floods (a.k.a. IGRINS lamps) on the LMI lamp boom