DIS Slitviewer - Users Information

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This page last updated: June 28, 2006 - JMD
This page last checked: September 28, 2004 - JMD

Contents

Basic information to know...

Using the DIS Slitviewer

The DIS Slitviewer Quick Start Guide

DIS Slitviewer User's Manual

Slitview docs(copy info off Loki!)

Setting Orientation of and Placing Objects on the DIS Slit

Reference

Basic information to know...

You should retrieve your science images off from APO computers within 7 days after they are taken, otherwise they will be deleted. We DO NOT back up data locally here. Data can be found here.

To place an object in the middle of the DIS CCD's you need to place the object at (228,284) of the slitviewer. (note: this coord needs to be verified)

Using the DIS Slitviewer

• Setting up DIS Slitviewer exposure parameters
• Taking your Calibration lamps
• Taking your Dark Frames
• Focusing DIS Slitviewer
• Centering your star on the slit
• • TUI
• • Remark
• Setting up multiple exposures
• Taking your exposure
• Pausing an exposure
• Stopping an exposure (early Readout)
• Stopping an exposure (discarding data)
• Where does your Data go?
• Always examine your data!

The DIS Slitviewer Quick Start Guide

 DIS Slitviewer User's Manual

last updated 26 June 2003 by JCB

An Important Note About 3.5m Autoguding And The DIS Slitviewer

Although the 3.5m telescope tracks very well unguided over the course of many minutes, and performs even better with the NA2 autoguider, you MUST monitor the DIS slitviewer periodically! This can be done either by issuing the repeat command in the slitviewer software or be taking an exposure with exp commands every few minutes. Instances are known where object drifts very slowly off the slitviewer while the telescope is autoguding in particular parts of the sky where the rotator speed is large; by not monitoring the slitviewer, entire exposures have been lost due to this problem. To assure the quality of your data, remember to check the slitviewer (as well as your raw data!)

Introduction

This manual describes how to operate the Apogee camera which is used as the slit viewing camera in DIS. This camera is operated by a separate program outside the normal Remark interface. For instructions on using DIS itself, see other documentation.

The Apogee slit viewing camera is made by Apogee Instruments and uses an 512x512 thinned, back-side illuminated SITe CCD for imaging the DIS slit. The 24 pixels give an angular pixel size of 0.31 arcsec/pixel, with a total square field of view of 150 arcsec on a side.

The reasons for switching from the old SBIG slit viewer to the new system are:

1.

The new camera has significanly less overhead for readout time and image transfer time

2.

Software for the new system should allow in most cases for remote operation, which will hopefully lead to better efficiency

3.

The new camera should have better sensitivity than the old one

Requirements and capabilities

To run the software and be able to see the images, you must be:

1.

working on a workstation running an X11 window server,

2.

the X11 server must be running in 8-bit PseudoColor mode.

The software will allow you to take images, with optional automatic dark subtraction, and will display these on your screen. You will be able to interact with the images to get pixel coordinates, values, etc., and adjust the color map both by adjusting the color map or by redisplaying with different contrast/brightness. Simple image centroiding is possible which will suggest instrument offsets needed to place the object in the slit. Images will be saved by default in /export/images/dis-slit, although the auto-saving may be turned off. If desired, the images can be automatically copies to your local machine using the secure scp, if you set up an account which allows remote access without a password (instructions later).

Running/restarting the program

To start the program, you must first log onto tycho.apo.nmsu.edu using the visitor1 account (check with APO staff if you don't know the password). Once logged into tycho, execute:

slitview

to start the program. In reality, this will actually be running a program on another computer (offset.apo.nmsu.edu) to which the CCD is physically connected, but this is all transparent to you. A separate xterm window should appear on your screen with a status section in the top half, and a command section in the lower half. At the current time, you should not resize this window. Once you take your first exposure, a display window will appear with the image.

Hopefully this won't ever happen, but if the program appears to be totally hung up, you should be able to kill it using a CTRL- . Then restart it as above.

If you wish to interrupt an exposure (e.g., you entered an exposure time which is much too long), you should be able to do so using CTRL-C. This should stop the current exposure and return you to the command prompt.

Commands

All commands are case insensitive. The following commands are available:

• EXP [time]

• REPEAT

• STOP

• WINDOW [x1 x2 y1 y2]

• FULL

• Offset commands

• NEWCENT xc yc

• FILENAME [name]

• NEWEXT [ext]

• +DARK/-DARK

• FITS

• -DISK

• +DISPLAY/-DISPLAY

• +XFER/-XFER

• SCALE

• NEWSCALE

• SKYSCALE

• FULLSCALE

• SAMESCALE

• SETTEMP temp

• QU

Image display window

The first time an image is taken, the program opens an Image Display window on the console, and loads a color map as well as displaying the image. Once an image has been displayed, the Display window will accept interaction asynchronously of commands in the command window, provided that a wait for input, or any other I/O is not pending. To interact with the image, simply move the mouse onto the display window. The current pixel location of the cursor will be displayed in a frame at the base of the image display along with the pixel intensity. The arrow keys are used for find control (one pixel at a time) of the cursor position.

Important. If the image display window fails to open after the first image, it may be because of a problem with the program interacting with your X11 server. Make sure your X11 server is running in 8-bit PseudoColor mode; this is the mode which is required, e.g., for IRAF/XIMTOOL. If insufficient colors are available in the default colormap, the program will allocate a private colormap to proceed, in which case you may see the colors on your display switch as you move the cursor into and out of the display window. If you are using a private colormap, you will need to move the cursor into the display window to see the images ``normally''.

By default, the image window comes up as a moderately small window which shows a view of the image at 1/2 resolution. With mouse keys (described below) you can zoom into any region at full resolution. Alternatively, you can resize the window to a larger size and the program will automatically display images at full resolution if your resized window is large enough. This can be done at any time and does not require re-starting the program.

The image will come up with (1,1) in the lower left corner. With this convention, the image appears in the same orientation as it does on the sky. If the instrument is at 0 position angle, then N will be up and E to the left; obviously, if the instrument is rotated, this will no longer be true.

The following mouse buttons and keyboard keys are active while the mouse is located on the image display:

If you place the mouse on the color bar, these commands are available to adjust the contrast of the image:

LOW CONTRAST

Hold down the LEFT Mouse button, drag the left end of the color bar.  

HIGH CONTRAST

Hold down the RIGHT Mouse button, drag the right end of the color bar.  

ROLL COLOR MAP

Hold the MIDDLE Mouse button, "roll" the color bar left or right.

The position of the mouse cursor displays the range of intensities represented by that color.

Pressing the R key while the mouse is on the color bar restores the original color map (undoing any change of the contrast or "roll" changes made with the mouse buttons).

Details and what to do in case of problems

When you issue the slitview command from tycho, you are actually just starting a process on the computer to which the slit viewing camera is actually connected; this computer is offset.apo.nmsu.edu. As a result, you cannot kill the program on tycho itself. When slitview is started, it automatically kills any program which is currently talking to the camera before a new control program is started up. Only one user can connect to the camera at a given time. There is a command on tycho called killview which will attempt to kill any existing slitview processes on the remote machine.

If you have problems with the program, it may be a good idea to directly log onto offset.apo.nmsu.edu, user arc (password known by on-site personnel). Check to see if any processes are running the program slitview.linux. If you kill these, any running versions of the program should exit. On offset, there is a script, killview which will automatically do this for you. Then you can try to start the program again using the slitview command.

To Do items

• Implement a Gaussian fit/radial plot routine to allow for focus analysis within slit viewer application. (HIGH priority but unfortunately may require a fair bit of work!)

• put default target nighttime and daytime temperature, as well as default slit center position, in a configuration file which is read on startup.

• Implement a "smoothing function" for temperature readout to avoid the "noise" in temperature readout.

• note cooler load so one could adjust temperature accordingly

• Figure out how to get a blinking cursor in the right place in the command window.

• Figure out how to allow users to resize the command window without screwing things up too badly.

• Figure out how to get image automatically redrawn if display window is resized.

• Implement communication with the telescope to put telescope parameters in image headers.

• Implement communication with the telescope to allow offsets to be directly implemented by the telescope

• If telescope communication is implemented, implement autoguiduing algorithm.

• If telescope communication is implemented, put a compass on the image showing N and E given the current rotation.

Setting Orientation of and Placing Objects on the DIS Slit

1. Slew to field at Object Rotation=0, take a slit image.

2.  

3. If one or both of the objects are obscured by the slit, DO NOT offset at this time. You can adjust the position a little and reslew to get them off the slit. But offsetting before adjusting the rotation can make trouble.

4.  

5. Measure the positions of the two objects: (x1,y1) and (x2,y2)

6.  

7. Rotate to this angle:

8.  

9.                           / (y2 - y1) \
                     arctan ( ----------- )
                             \ (x2 - x1) /
      

10. 
    If I got this right, the sign of the rotation should come out correct. You can also check it visually: A positive rotation moves the field clockwise.

11.  

12. After rotating, take another image to verify that the rotation is correct, and find the offset position to get them on the slit.

13.  

14. Use an instrument offset to move the two objects onto the slit.

15.  

SETTING OBJECT(S) OF A GIVEN POSITION ANGLE ONTO THE SLIT

If you know the P.A. (Position Angle) of your object on the sky, you can place it on the slit by using the following rotation:

Rotation = (P.A. - 90)

Where P.A. is measured North through East on the sky, North= 0 and East=+90. This rotation will align the object(s) parallel to the slit. Use an instrument offset in the Y direction to move the object(s) onto the slit. The scale is 0.31 "/pixel

SETTING SLIT TO BE PERPENDICULAR TO HORIZON:

If your goal is to orient the slit with respect to the horizon, there are two ways to go about it. The simplest is to use a rotation type of horizon. To keep the slit perpendicular to the horizon while you track, set the rotator to 90 degrees, horizon. The drawback to this method is that the field is no longer de-rotated on the sky. Thus only one point in the field will be stationary and all else will rotate about it. This point is called the boresight. To minimize the rotation of your object, you should correct local pointing error (Recalibrate under Telescope -> Special Moves) then use object offsets to put your object at the center of the slit.

A few words on offsets:

The reason you need to use object offsets to place the object at the center of the slit (defined as the boresight in the instrument block)is because object offsets leave the boresight at its default location. Instrument plane offsets move both the object and the boresight. Thus, while you may put your object in the center of the slit using instrument plane offsets, you will have moved the boresight away from the center of the slit at the same time. Again, Object plane offsets only move the object. Instrument plane offsets move both object and boresight. The drawback to Object offsets are 1) When the rotator is not at 0 deg obj, a declination offset is no longer vertical and RA offset no longer horizontal on your image. 2) You must divide by cosine of the declination to get an RA offset in arcseconds on the sky. With instrument plane offsets the amounts are always in arcseconds on the sky and X-offsets are always horizontal and Y-offsets are always vertical regardless of rotator angle.

The second method is a bit more tedious, but you can have the rotator track with the sky, while being approximately perpendicular to the horizon. You need to determine what object rotation angle corresponds to 90 degrees horizon. There are several ways to do this. One way is to issue a TCC AXIS STATUS command using the tester buttons of Remark, while tracking with rotator set to 0 degrees object. The AXISSTAT word for AXIS 3 (which shows up in the debug window), gives the mount position of the rotator in degrees. Next move the rotator to 90 deg horizon, and repeat the TCC AXIS STATUS. The difference between the two is the object rotation angle you will need to put in to orient the slit perpendicular to the horizon, and still track the sky. Check this by issuing another TCC AXIS STATUS, once you have entered the object rotation angle to be sure you have the sign right.

AN EXAMPLE:

After you slewed to your object (rotator at 0 deg object), the rotator was at 122 degrees mount. After rotating to 90 Horizon, the rotator was at 29.5 mount. To orient the slit perpendicular to the horizon and track the sky, set the rotator to 122 - 29.5 = 92.5 degrees object. Now the rotator should read around 29.5 degrees mount. Now that you have the slit aligned roughly perpendicular to the horizon you can use instrument plane offsets to put the object on the slit in the same way described above when rotating with the sky (you can also use object offsets but determining which way is "up" is more tricky). Your object is at 420,442 on the red chip. So your offset will be (434 - 442)*0.610 = -4.9 " in Y in the instrument plane. You now have your object on the slit and the slit is roughly perpendicular to the horizon.