6  The Multiple Instrument System (MIS)

6.1) Introduction

6.2) The MIS Camera

6.3) The Multiple Instrument System Control Software, xmis2

6.4) Finder & Spectroscopic Calibration

6.5) Guider

6.5.1) xmis2 guider parameters; preset pop-up menu

6.5.2) Off-axis guiding for direct imaging

6.6) How to Focus the Guider and Instrument

6.6.1) Focus procedure: direct imaging

6.6.2) Focus procedure: spectroscopy

6.7) MIS Filter Wheels and Filters

6.7.1) 4" filter wheel

6.7.2) MDM filter sets

6.8) Technical Reference Section

6.8.1) Guest instrumentation and the MIS mounting plate

6.8.2) xmis2 software configuration (for staff use only)

6.1  Introduction

The Multiple Instrument System (MIS) is comprised of three discrete and independent modules that can be used with a suite of analytical instruments: finder, guider and filterwheel (Figure 6-1).

The Finder module contains spectral calibration (Ne, Ar, Hg-Ne & Xe) and flat field lamps.  It is of note that the Finder module is no longer equipped with a video camera as shown in Fig. 6-1.  

The OSU Buckeye filter wheel module, which also contains a shutter, is used with imaging detectors and some spectrographs when employed as image reduction systems.

The MIS modules are attached to the instrument rotator (Chapter 8) and thus, changing the rotator angle will alter the orientation of the finder and guider fields.  At the time of this update (2014Jan), the image rotator is not usable without some modifications to cable routing. 

The operation of the MIS is linked with several other units that must be turned on for acquisition and guiding (Figure 6-2). Please be aware that Figure 6-2 is out-of-date, although it still is a good primer for the MIS system.  Many components, including the Find camera, FIND/GUIDE Camera Selector, Digital Television Integrator, FIND/GUIDE TV Monitor, and SPARC2 computer have all been removed.  A simple system replacement contains an FLI CCD used for auto-guiding, connected via USB to a Windows-based PC in the control room (we hope to update the drawing as time permits).  

The MIS modules communicate through the MIS control crate, which is located in the right center instrument rack of the computer room. The front panel contains simply a power switch while a bank of fuses are located on the back panel.

Figure 6-1: Finder-Guider-Filter Wheel Optics

Figure 6-2: MIS Control Schematic

Figure 6-3: Finder/Guider System Checkout

6.2  The MIS Camera

The guider is equipped with a low-light-level Finger Lakes Instrumentaion (FLI) CCD that gives a real time display on the Guider PC.  Numerous user-settings, such as CCD temperature, binning, exposure rate, etc. can be modified as the observer sees appropriate.

The guide camera has a "wall-wart" power supply, mounted on the instrument rotator flange. These units are normally left ON; they must be powered down when the camera cables are disconnected to avoid damage to the CCD.

Note that the display orientation changes with position angle of the instrument rotator (Chapter 8), although currently you should assume that the rotator is not in use.

If you experience difficulty in acquiring objects in the guider, consult Figure 6-3 for a system checkout.

Figure 6-4: xmis2 GUI

6.3  The Multiple Instrument System Control Software, xmis2

The MIS control crate is operated from the observer's console (mdm13ws1), where commands to operate the various slides, lamps and filter wheels are entered through the xmis2 GUI (Figure 6-4). When the filter wheel is not used, the information on the filters is not displayed in the window.  (The astute reader will notice that the image above is of xmis2 at the 2.4m.  Rest assured, they are equivalent between the two telescopes.)

This chapter assumes you are familiar with all of Chapter 4. Start-up procedures for the software are described in Section 4.3.4.

When the software is loaded, a large red box with the word INITIALIZE appears. Click on this to initialize communications with the MIS control crate. Use the xmis2 SETUP menu to Initialize or Quit the software at any time. If one or more of the modules fails to initialize using xmis2, but continues after pressing the reset button on the control crate, check the fuses at the back of the control crate.

6.4  Finder

The Finder is used for spectroscopic calibrations or for lamp-based flat fielding.  If the Finder is set to the "IN" position, then it is in the optical path and ready for calibration use.  For on-sky observing, the Finder is set to the "OUT" position.

For spectroscopic calibration, move the Finder "IN" and choose the appropriate lamp(s).  If the lamp button is highlighted in green, it is on.  Make sure that the Guide Probe is not blocking the slit [Guider: S (14700,0)].  For best results, darken the environment to prevent "light leaks"--close the doors, turn off the lights and close the dark hatch.  Remember to turn off the lamp(s) when done.  This can be done by either clicking the appropriate lamp button a second time, or by simply clicking the All Off button.

6.5  Guider

The FINDER mirror must be OUT to allow starlight to reach the guider and your instrument.

An autoguider is available and is described in Chapter 7, which assumes that you are familiar with the contents of this section.

The guider has a diagonal probe whose minor axis is 25.4 mm. The probe can move in x and y directions as specified in Figure 6.5.

The probe has three basic positions accessible through the Preset pop-up menu:

• Origin: probe completely out of beam
• Center: probe looking up on the main optical axis
• Slit: probe looking down at light reflected off the slit plate

6.5.1   xmis2 guider parameters; preset pop-up menu

The probe can be moved to the first three positions by selecting the destination in the xmis2 Preset pop-up window. The coordinates of the guider probe, together with the message [O], [C] or [S] are displayed in the xmis window:

Origin:	Guider: O	(0,	0)
Center:	Guider: C	(14700,	17000)
Slit:	Guider: S	(14700,	0)

Units: probe

The default coordinates, given in motor steps where 1 step moves the probe 0.084 arcseconds at f/7.5 and 0.048 arcseconds at f/13.5

Units: arcsec

The scale is set to 0.0840 to display the probe coordinates in arcseconds at f/7.5.

6.5.2  Off-axis guiding for direct imaging

The probe can move off-axis in x and y directions as specified in Figure 6-5.

Figure 6-5: GUIDER PROBE X-Y COORDINATE MAP

There are two ways to move to an off-axis position, using either absolute or incremental instructions.

X pos: Y pos:

To move the probe in absolute coordinates, place the mouse in the X pos box, type in the desired value and press enter. You will see the message "probe moving" and then the new position will be displayed. Repeat the procedure for the desired Y pos.

dX: dY:

To move the probe by an incremental amount place the mouse in the dX: box and enter the desired amount of movement. Repeat for dY:. 1000 counts will move a star about halfway across the field. Positive numbers move the star right (dX:) and up (dY:) (assuming rotator angle of zero) and negative numbers go the opposite way.

Stop

If you are scanning for a guide star and you see a suitable object moving across the field click on the Stop box to arrest the motion.

6.6  How to Focus the Guider and Instrument

This section assumes you are familiar with the preceding sections. The procedure is different for direct imaging and spectroscopy. Once everything is aligned and focused you can note the field centers.

6.6.1  Focus procedure: direct imaging

1. Bring your instrument (telescope) to focus:
   • Move the guide probe to Origin through the Preset pop-up menu.
   • Center the star on the detector by taking short exposures.
   • Focus the telescope by moving the secondary mirror:
     • Focus is adjusted through the NewFocus entry on the MDM 1.3m TCS GUI.  Focus value can be found above that.  Higher values move the focal plane up.
     • IN drives the focal plane UP
     • 1 focus unit = 0.07 mm at f/7.5 or 0.2 mm at f/13.5 (?)

2. Bring the guider into focus:
   • Move the guide probe to Center through the Preset pop-up menu.
   • Focus using focus.exe, found on the guider computer desktop.  Click STOP when focusing is completed.  Click the white arrow, as seen in the images below, to restart the program.
     
     
                                       
   • If you cannot achieve desired focus, let the MDM staff know.  Even if your focus produces donut-shaped stars, the guide system should still work effectively enough (mmm... guide donuts) for science.

6.6.2  Focus procedure: spectroscopy

1. Align and focus the spectrograph:
   • If time permits, the staff will focus the instrument for you.  However, in the event of telescope problems, or even double-instrument changes, there may not be adequate time to run through the focus routine prior to your arrival.  It's good to read through the manual(s) specific to your instrument and have a working knowledge of what is required to focus the instrument in advance.

2. Focus slit-viewing optics
   • In the case of CCDS, a devoted SBIG CCD is in use for slit-viewing.  This camera has already been focused and will not need adjustment.
   • For ModSpec or the MkIII, an Andor CCD is used for slit-viewing.  MDM staff will have set the Andor focus accordingly before you go on-sky.  For more information about the Andor system, refer here.

3. Turn off the Flat lamp and put the FINDER to Out.

4. Acquire a bright (about m_V = 8) star in the guider (Section 6.5)
5. Focus the telescope on the slit plate by moving the secondary mirror:
   • Use the telescope hand paddle.
   • IN drives the focal plane UP.
   • OUT drives the focal plane DOWN.
   • SET+IN or SET+OUT gives a rapid focus change.
   • 1 focus unit = 0.07 mm at f/7.5 or 0.2 mm at f/13.5.

6. Bring the guider into focus (see above)
7. Mark the field centers (Section 7.3).

6.7  Filter Wheels and Filters

6.7.1  Four-inch filter wheel

The OSU "Buckeye" filter wheel can be used for any direct-imaging setup (MDM or 4k CCDs).  It is controlled via the xmis2 GUI interface.  It is a 12-position filter wheel, holding up to 11 4"-square filters at a time (slot 12 is usually reserved as an open pass-through).  Typically, 2"-square filters can also be mounted in modified filter holders as well.  

6.7.2  MDM filter sets

4" UBVRI filter set:  In 2004 MDM received a set of four-inch square filters for use in the new filter wheel. They were supplied by Custom Scientific, Inc. to the same specifications as the 1999 2" UBVRI filters. 

4" DES-i, z, Y

4" SDSS-g, r, i

2" h-alpha

2" 893/13.6

2" Gunn-u, g, v, r, i

2" Kitt Peak-R, I

6.8  Technical Reference Section

6.8.1  Guest Instrumentation and the MIS mounting plate

The finder, guider and filterbox modules of the MIS all have the same basic 12 mounting holes (Figure 6-6). These holes, 0.625 DIA, take reducing bushings and nuts. These are available in stainless steel and nylon. An electrical isolating spacer, made of G10, is also available.

The vertical height of each box is shown in Figure 6-1; a variety of back focal distances can be accommodated by using a combination of the modules:

Modules used	remaining back focal distance (inches)
none	15.72
Finder	7.25
Finder + Guider	3.00
Finder + Guider + Filter wheel	0.50

If the MIS is not used at all, instrumentation can be mounted directly on the instrument rotator (Chapter 8). The MDM 8K Camera does not use the MIS.

The diameter of the central hole in the FINDER and GUIDER boxes is 177.8 mm (7.0 inches), and the unvignetted field diameter of the telescope at f/7.5 is 125 mm (5 inches). The guid probe and the slit-viewing optics both vignette this field (Figure 6-5).

The slit viewing optics were designed for use with a focal plane 63.5 mm (2.50 inches) below the guider box. The optimal focal plane of the telescope, however, lies 76.2 mm (3.00 inches) below the guider. The slit viewing optics can be adjusted to accommodate slit planes from approximately 50 to 81 mm (2.0 to 3.2 inches) below the guider box. The FILTER WHEEL has, in addition to the 12 mounting holes around the perimeter which take the reducing bushings, 8 holes tapped 1/4- 20 as shown. The central hole is 2.25 inches in diameter.

The maximum total weight of the instrument depends upon its distance and distribution from the instrument rotator, and is approximately 500 pounds (225 kg). A moving platform allows heavy instruments to be raised for attachment to the telescope. Please consult the staff at an early stage if you plan on bringing out your own instrumentation.

Figure 6-6: MIS Mounting Plate Dimensions

6.8.2  xmis2 software configuration (for staff use only)

Staff notice for instrument changes: The xmis2 software needs to know which of the three MIS modules are installed. The telconfig script is used to setup both the TCS and MIS configuration for a given telescope and instrument combination. See the Startup Guide for details.