page_title: Apache Point Observatory
section_title: ARC 3.5 m
hierarchical_section_title: Apache Point Observatory / Telescopes / ARC 3.5 m
caption_attribution_description: Apache Point Observatory 3.5m telescope running APOLLO lunar laser ranging experiment taken by Dan Long
context_page_description: The Apache Point Observatory is an astronomical observatory located in the Sacramento Mountains in Sunspot, New Mexico, United States, approximately 18 miles south of Cloudcroft. The observatory is operated by New Mexico State University and owned by the Astrophysical Research Consortium. Access to the telescopes and buildings is private and restricted.
context_section_description: The ARC 3.5 m (140 in) telescope is a Ritchey-Chretien reflector on an alt-azimuth mount with instruments attached at several focal points.  Construction of the building began in 1985, but full operations of the telescope were delayed until November 1994 due to problems with fabricating the primary mirror.  From 1991 until early 1993 the telescope was fitted with a 1.8 m mirror now located at Rothney Astrophysical Observatory under a cost-sharing agreement.
  There are a variety of optical and near-infrared instruments available for the 3.5 m telescope, including:
  The ARC echelle spectrometer (ARCES) uses a 2048 × 2048 pixel CCD and has a resolution of .
  The Double Imaging Spectrometer (DIS) is a low-resolution optical spectrometer.
  The Near Infrared Camera/Fabry–Pérot Spectrometer (NICFPS) was developed at the University of Colorado. It uses a 1024 × 1024 H1RG HgCdTe infrared detector and a near-infrared Fabry–Pérot interferometer. It has many narrow band filters, including H2, [Fe II], and [SiVI]. It is unique among astronomical Fabry-Pérot devices in that it is cooled with liquid nitrogen.
  The Seaver Prototype Imaging camera (SPIcam) is an optical imaging instrument with a 2048 × 2048 pixel CCD.
  TripleSpec (Tspec) is a near infrared spectrograph which provides continuous wavelength coverage over the range 0.94–2.46 µm at moderate resolution (, depending on the choice of slit).
  The 3.5 m telescope is also used by the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) lunar-ranging project.  The APOLLO laser has been operational since October 2005, and routinely accomplishes millimeter-level range accuracy between the Earth and the Moon.
  Observations using the 3.5 m telescope can be carried out remotely by observers using TUI, the Telescope User Interface, via the internet.
caption: The ARC 3.5-meter telescope
exif: {"Image Make": "NIKON CORPORATION", "Image Model": "NIKON D70", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS2 Macintosh", "Image DateTime": "2008:02:06 13:05:34", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "228", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "946", "Thumbnail JPEGInterchangeFormatLength": "0", "EXIF ExposureTime": "30", "EXIF FNumber": "4", "EXIF ExposureProgram": "Manual", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2005:09:14 23:31:30", "EXIF DateTimeDigitized": "2005:09:14 23:31:30", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "4", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire", "EXIF FocalLength": "12", "EXIF SubSecTime": "10", "EXIF SubSecTimeOriginal": "10", "EXIF SubSecTimeDigitized": "10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "480", "EXIF ExifImageLength": "640", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "820", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CVAPattern": "[0, 2, 0, 2, 2, 1, 1, 0]", "EXIF CustomRendered": "Custom", "EXIF ExposureMode": "Manual Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF FocalLengthIn35mmFilm": "18", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "None", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}