1.2m (48") Telescope

Care and Feeding of the 1.2m (48") Telescope

Created: 03/23/94 by NC
Updated: 10/12/19 by EF

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The 1.2m (48") telescope is an f/8 Ritchey-Chretien reflector, with a honeycomb borosilicate (Ohara E6) f/1.9 primary mirror. In 2013, we replaced the old primary, see this link for a description of the quality of the new mirror. It has a coma-free field of 30 arcmin. The primary is supported in its cell by a system of axial and radial actuators, whose forces on the mirror are determined by counterweights. The axial and radial definitions are each made by three hard points, each of which has a load cell whose force readings are displayed above the electronics rack in the control room (either radial or axial can be displayed, but not both; the normal display is axial).

There are two secondary mirrors, each giving the same Cassegrain focal ratio, but one being undersized for IR observations (in recent years, we have not used the IR secondary). The secondaries are centrally supported and defined. The secondary mechanism (HEXAPOD) allows full remote control of the position of the mirror for collimation; however, observers can only use the focus movement.

The fork mount uses direct-friction drives, allowing very fast slewing (about 2 deg/sec) but with the potentially dangerous feature that the telescope can be moved manually when the motors are not engaged. The drive motors are controlled with a PC (the "mount PC") running software supplied by Comsoft. The dome position is encoded, and when properly set will follow the motion of the telescope accurately.

A guide system running on a Linux PC allows movement of the guide pickoff mirror, in the "topbox", focus of the guide camera, as well as autoguiding. The guide field is about 2x1.5 arcmin. The power for the guide camera should be left on. You will find the electronics box and its switch mounted on the mirror cell. Make sure the guider system is working first. See directions and operating instructions here: guide system . Instructions to operate the guider via the TCS program are available here.

The topbox also has an 8-position filter wheel, controlled by the guide computer, with an interface showing in the TCS program. Moving by 1 filter takes about 5 seconds, by 2 (3), 10 (15) seconds. TCS optimizes the filter wheel rotation, so no filter move takes more than 15 seconds. The maximum filter size is 4" ; inserts allow 2" square and round filters to be used (vignetting may compromise your observations with 2" filters). Observers are not allowed to change filters; please ask the staff during daytime if you need to change filters.

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Cold Start

Warm Start

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The Track Rate and Guide Rates are automatically reset to good values when the Tcs program starts.

There is a large two-speed fan that can be turned on after the dome is opened at night (to the South of the telescope).

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To take dome flats:

To take sky flats:

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 Remote Observing

A: General Info

  1.  Remote observing is intended for observers at CfA in Cambridge. It may be feasible from other institutions or from your home with a high-speed internet connection through your account at CfA. However, the additional network layers and possible barriers may slow you down and preclude observations. You should use the VNC viewer system for observations (also available for windows or Mac OS, see the instructions here). VNC is required, because a loss of connectivity at your location will not bring down the telescope control system. If the outage is temporary, you should be able to recover, or you may need to request a telescope shutdown from the 1.5m observer. It is still possible to observe by logging in with ssh (see below), but we strongly discourage it.
  2. Note: if you require filters that will not be mounted for the run immediately preceding yours, you should provide a list of your filters via email to the staff (WP or TG) a few days before your run.
  3.  If you need dome flats, see the description above.
  4. Please coordinate with your remote helper.  He or she should have your  phone number, email address, remote host name, and any special instructions. It's a good idea to check by phone before starting up, to ensure that no one else is using the system. Make sure that you arrange for both opening up the dome and shutting it down. Take special care when neither Perry Berlind nor Mike Calkins is observing at the 1.5m to plan your night with the observer.
  5. Don't always expect your 1.5m remote helpers to drop everything and help you immediately.  They are working as well, and will help you as soon as feasible.
  6. Note that if your remote helper decides that weather conditions necessitate closing the domes, he or she may need to make the decision for the 1.2m without previous warning to you.
  7. Please realize remote observing can be negatively affected by problems with the internet between Mt. Hopkins and your location that are beyond our control.
  8. If there is a miscommunication and your remote helper is not at the 1.5m when you shut down at the end of the night, point the 1.2m West, away from the sun, at about 45 deg elevation. Weekdays, the day crew will arrive at about 9am MST. Notify them by email that the 1.2m remained open. On weekends, call the dorm room or the gamma-ray building in case someone is there that could assist. If that fails, call WP or EF.

  • Phone number for 1.2m --> (520) 879-4517
  • Phone number for 1.5m --> (520) 879-4519
  • Phone number for Ridge Dorm --> (520) 879-4520
  •  B: Starting Up

    1. It is critical to have a dry run of remote observing procedures at the machine that you plan to use. We recommend trying it out during daytime (after calling in), so you'll be able to ask the staff questions if necessary.
    2. Log into your computer in Cambridge.    You will be using vncviewer to access the system from flwo48, and perhaps also to access the guide camera. Make sure you are using TightVNC. If it is not available on your machine, you can find an executable at ~ted/bin/vncviewer. TightVNC is strongly preferred over the default RealVNC system at the CF. See the instructions for remote VNC use.
    3. If the vncserver is not running, ssh into flwo48 using the observer account. (only observer can be used to observe with Keplercam).  Issue the command govnc to start the vncserver. Once you have connected to the server issue the command gokep to start the system inside the vncserver
    4. Turn on tracking and dome tracking (under Tele Tasks Menu).
    5. If your exposures are longer than 5 minutes, you will need to guide. To view your guide stars in the guider window, start the guider programs in another VNC window.
    6. The pinkish guider Rgain button (below the slider) on the yellow ntcs GUI controls the camera gain. You must click this button to turn remote gain control ON (OFF when done). It is less immediately responsive than the local knob control. If the gain is too high you saturate the guide camera, so move it up slowly. Note: the local knob control should be turned to its minimum (CCW) to use the remote controls. Although it has an automatic gain control (AGC) that is supposed to prevent damage, be careful not to expose the guide camera to bright lights as much as possible. It is a very sensitive intensified camera, also very expensive.
    7. If the gain does not seem to have an effect, ask the 1.5m remote observer to verify that the 1.2m guide camera is on (it should remain on at all times) or turn it on for you. Also, have her check the mirror covers!

     C: Acquiring Data

    1. Please check the online documentation.
    2. Use of catalogs is strongly encouraged.
    3. The remote helper should check pointing off-line before turning over the system to you (at which point he should log out of the Realtime system).  Make sure to tell him/her whether you want the telescope centered at the center of Keplercam, or rather one of the individual amplifiers. Please refer to the manuals for instructions on centering on an amplifier. After that, first you open the Misc Menu on tcs, turn on dome track and tele track.  The catalog brightGaia.mct is an update of the older brightstars.mct with more recent star positions down to g=6mag.  Verify the pointing by moving to a bright star.  Adjust the guide camera focus.
    4. Try using the new command kfindfwhm
      If you are set in the old ways, go to a fairly dense stellar field, and focus the telescope with nfoc or testfoc. See, e.g., the Keplercam primer.
    5. Go to your first object, take an exposure, ftp it back to you machine, and use iraf and/or saoimage to view the data.  You can also do these remotely,  but the impact of the link may be painful.
    6. The dome may close automatically if rain/high humidity occur.

     D: Shutting down

    1. When you are done, stow the telescope, and call your helper to close as soon as she is able. If you were using remote gain please lower the gain to about 40, but leave it on.
    2. Type "bye" in the telshell window to exit the telescope control system.


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