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.
This table also includes the focus offset (wrt OPEN) that is applied when each filter is selected, and the approximate length of a dome flat (Exptime) resulting in counts of ~20,000 (selecting the time will link to an image of a flat of that length).
- 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 Sample flats for the various filters taken over time can be found on the LMI Filter Characterization page.
Filter Names for use in Pattern Files:
When using filters in the automated pattern files, the filter name has to match the LOUI display string for the filter. Since that may not always be what you think it is, the table includes both the string for use in pattern files (Pattern String) and the corresponding string that will be inserted into image FITS headers (FITS Header Value).
| 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 BroadBand 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 & thus not a great candidate for dome flatsusing the CLSD lamps at 12V.
* Using the photo floods (a.k.a. IGRINS lamps) on the LMI lamp boom