Apache Point Observatory

FILTERS

• neutral density filters
• broad band filters (bandpass > 30nm)
• intermediate band filters (10nm < bandpass < 30nm)
• narrow band filters (bandpass < 10nm)
• blocking filters
• specialized filters
• filter sets

Filter Size for Each Instrument

Double Imaging Spectrograph:

Takes 50-mm square filters, up to 8-mm in thickness. Note: These filters are mounted in the slit mask wheel. There are 4 interchangeable slit mask wheels. Wheels C and D each have five apertures for slit masks or filters. Wheels A and B each have four apertures for slit masks or filters and one aperture of a special size and shape for mirrored long slits. The slit mask wheel pull down menu in the Remark DIS interface lists the filters and slits currently mounted in the wheel in the spectrograph. The Gunn-Thuan filters (g and r) are permanently mounted in a wheel that is not accessible. The Gunn-Thuan filters can be rotated out of the beam if the observer does not want to use them. The field of view with 50-mm filters inserted is 4.7x4.2 arcmin.

Drift Scan Camera:

Approx. 80-mm square, up to 5-mm in thickness. Smaller filters can be used with inserts, but cause vignetting.

Echelle:

Will probably be able to accommodate 50-mm square filters, up to 20-mm in thickness (?)

Guide Camera:

Takes 1.40-inch square filters, up to 0.315-inch in thickness.
Note: The guide camera is not designed for frequent filter changes.

Thanks to Karen Strom of the UMass Astronomy Dept. for the use of her greek letter gifs.