1.5-m Telescope

1.5-m service observing schedule and information website 

About the 1.5-m Telescope

The 1.5-m telescope is one of the small telescopes operated by the SMARTS II Consortium.

The 1.5-meter telescope is mounted on an asymmetrical, off-axis mounting and is used on the east side of the pier. It is not possible to reverse the telescope over the pier.

All Cassegrain instruments are mounted on an instrument rotator, and thus they may be placed at any position angle on the sky. However, rotation is performed manually and can only be done near zenith, so changing the PA usually requires at least 10 min. The angle can be read to ± 0.1 degree. Variable speed, D.C. motors have been incorporated into both the right ascension and declination drives in order to improve the efficiency of the telescope for infrared work.

The view of the 1.5-meter telescope is restricted when looking towards the SE by the dome of the 4.0-meter telescope. At the following declinations, exceeding the indicated hour angle will cause the view to be obstructed:

Graph of theoretical image quality over the FOV and sensitivity of focus with temperature change

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Observing mode

Entirely service observing. See Operating Plan for up-to-date information and any current restrictions that may apply.

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Instruments 

RCSpec and CHIRON are the current instruments in use at the SMARTS 1.5-m telescope.  In the past, the 1.5-m has also hosted the following (now retired) instruments: Bench Mounted Echelle (BME) Spectrograph, the Automated Single Channel Photometer (ASCAP), OSIRIS and CIRIM IR imagers, a Cass focus CCD (CFCCD) Imager and the CPAPIR wide-field IR Imager.

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Time Synchronization

For projects that require accurate timing information, here is a quick overview on how the time ends up in the image headers:

When using the optical imager, there are two different header entries relating to time, UT and UTSHUT. UT is read from the TCS. While there is a GPS receiver that displays accurate Universal Time in the telescope's console room, this information is currently not communicated to the TCS automatically, but instead has to be manually entered at the beginning of each night. The absolute accuracy is therefore at best ~1 sec. In addition, the TCS clock often drifts by a considerable amount during the night and is therefore not reliable for both absolute and relative timing.

UTSHUT is taken from the ARCON controller's clock, which is synchronized against the SUN data acquisition computer's clock every time ARCON is started up. After that it runs on the controller's internal clock. The UTSHUT timestamp is the time when the shutter opens and should provide the most accurate timing information currently available. The SUN computer's clock is synchronized with the time reported by the US Naval Observatory and other internet sites (the details of this process are given here). Occasionally, e.g. after a power outage or network problems, this synchronization process fails and it is important to check the accuracy of the SUN clock at various times during a run by visually comparing it to the GPS time display.

To check for the correct UT time on the web, try this link to the USNO Master Clock.

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Proposal and Observing Preparation

See the Applying and Observing pages for more information and forms.

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