Aperture Wheel
The aperture wheel has seven slots for slits, pinholes, and occulting
disks, and a clear position. Any position of the wheel may be
remotely selected from the
Motor Control
GUI.
For slit spectroscopy, an assortment of precisely machined, slit-shaped
apertures is provided. The observer may chose from among eleven apertures
of various fixed widths (most are 3.6 arcminutes in height), but the
four mounted by default in the aperture wheel (see below), along with a
pinhole and two occulting disks, have proven satisfactory nearly everyone's
needs.
The apertures are positioned at a slight angle to the focal plane so
that a periscope assembly can be used to view the slit with the guide
camera, for both field acquisition and autoguiding.
If yopu need to use an aperture that is not one of the standard apertures,
contact a support astronomers in advance of your run so that they can
install the aperture for you. The standard installed apertures and others
listed listed below.
| Standard Contents of Aperture Wheel |
|---|
Wheel
Pos. | Pixel Width1 |
Arcsec Width | Return
Code |
|---|
| 0 | Empty | Empty | 1250 |
| 1 | 1.4 (0.7) | 2.9 | 1550 |
| 2 | 2.2 (1.2) | 4.6 | 1850 |
| 3 | 3.2 (1.7) | 6.6 | 2150 |
| 4 | 4.2 (2.2) | 8.8 | 2450 |
| 5 | Pinhole | 1.5 | 2750 |
| 6 | Occulting Disk | 5.0 | 3050 |
| 7 | Occulting Disk | 10.0 | 3350 |
| 1 Values in parentheses are for the 58mm Nikkor lens. |
|
| Other Available Apertures |
|---|
| Millimeter Width | Pixel Width1 |
Arcsec Width |
|---|
| 0.097 | 0.29 (0.15) | 1.2 |
| 0.146 | 0.44 (0.23) | 1.7 |
| 0.194 | 0.61 (0.32) | 2.3 |
| 0.340 | 1.0 (0.53) | 4.1 |
| 0.3882 | 1.2 (0.61) | 4.6 |
| 0.646 | 1.9 (1.0) | 7.7 |
| 0.923 | 2.8 (1.5) | 11.0 |
1 Values in parentheses are for the 58mm Nikkor lens.
2 All slits are 18mm (3.6 arcmin) long with the exception of the
0.388mm aperture which is 10mm (2.0 arcmin) long. |
|
| Aperture IDs |
|---|
| ID Number | Aperture |
|---|
| 1 | 2.9 arcsec slit |
| 2 | 1.2 arcsec slit |
| 3 | 1.7 arcsec slit |
| 4 | 2.3 arcsec slit |
| 5 | 4.1 arcsec slit |
| 6 | ?? arcsec slit |
| 7 | 4.6 arcsec slit |
| 8 | ?? arcsec slit |
| 9 | 6.6 arcsec slit |
| 10 | 7.7 arcsec slit |
| 11 | 8.8 arcsec slit |
| 12 | 11.0 arcsec slit |
| 13 | 4.6 arcsec slit, 2.0 arcmin long |
| 14 | 1.5 arcsec pinhole |
| 5" | 5 arcsec occulting spot |
| 10" | 10 arcsec occulting spot |
| 15" | 15 arcsec occulting spot |
| N/A | large (maybe 20 arcsec) occulting spot |
| N/A | Wire |
Support Astronomers (sa@ucolick.org)
Last modified: Tue Jul 17 18:34:48 PDT 2012
