The Slit Camera Viewer (SCV) GUI

Allows users to alter the visual scale used for the current slit camera image that will appear in boxes 2, 3, 5, and 6. “Zscale” is automatically adjusted by the GUI for each slit camera image, but users can select “Manual” if they are checking for faint sources or the autoscale is undesirable.

A close up image of the slit in 5. The red and blue boxes represent the A- and B-nod positions on the slit respectively (i.e. the target will shift to the crosshairs in these boxes on the slit during A/B observing--assuming the nod executed correctly!). The green circle off of to the side of the slit represents the coordinate reference pixel (the green cross in 5) for the spectra. The coordinates recorded in the IGRINS header correspond to the coordinates at this reference pixel.

This box will fill with a zoomed in image of the slit (similarly to box 2) when the Guide button in box 14 is clicked. Box 3 is the box users should click in when setting up guiding on slit. For off-slit guiding, additional colored boxes will appear (to be discussed on the Autoguiding page).

Allows users to make adjustments to the slit camera image in box 5.

1. Raw image shows the image as taken from the slit viewing camera, scaled using the settings in box.

2. Sub (Prev) shows the difference between the previous slit camera image and the slit camera image most recently acquired. This setting is useful when panning around using the paddle in box 11 throughout pointing.

3. Sub (Sky) subtracts a sky reference slit camera image from the most recently acquired slit camera image. A sky reference slit camera image must be marked using the “Mark Sky” button for this to work properly. This feature is not often used.

Shows the entire slit viewing camera image with relevant orientations marked in cyan (North-East in top left corner, Slit-Width (SW) and Slit-Length (SL) marked in the center-ish left, and X- and Y-pixel direction for the image in the bottom left corner). The green cross represents the location of the reference pixel, while the red and blue boxes are the A- and B-nod positions, as outlined for box 2. This box is primarily used during pointing and target acquisition. The slit camera FOV dimensions on sky can be found here and the slit dimensions and slit camera image plate scale can be found here.

A zoom in on where the curser is clicked (if clicked) in box 5. This box is often used while focusing the telescope to view the shape of the PSF clearer.

Will show the same image as box 6 in different scaling (matplotlib color map jet) which can make abnormalities in the PSF easier to see. When this box is clicked the GUI will attempt to fit a Gaussian to the area surrounding the cursor (so be sure to center the cross hairs on the reference star! You can do this by clicking the center of the star in box 6). The FWHM of the Gaussian can be used as a proxy for the seeing, used to assist with focusing the telescope. Users can toggle between the views by clicking on this box.

When correctly configured, this box will show coordinates from TCS (the telescope control system) and user input information from the DTP.

This box indicates if the SCV is correctly communicating with the TCS. It is important that this shows a green box highlighting “connected” otherwise IGRINS and the TCS are not communicating properly!

Where the user can manually change the position angle after rotating IGRINS on the telescope. It is important that the PA is updated properly here after rotating IGRINS before taking observations! 90 deg is the standard stow PA for IGRINS.

The hand paddle that will slew the telescope on sky in small increments. The center value sets how far the telescope will move in the selected direction in arcseconds. This paddle is used during pointing in the beginning of the night and target acquisition/verification throughout the night.

For standard IGRINS observing the A-B selection in the Nodding box should always be selected. Other advanced guiding modes are discussed in detail in Autoguiding.

Allows the user to acquire a single slit camera image by clicking the single button (exposure time for the image is set in box 17) or to stop the acquisition of the slit camera image (often only used if the exposure time for the slit camera image is incorrect).

After setting up guiding using box 3 and the buttons in box 16, users can start guiding on sky by clicking the “Guide” button. When observations for the target are finished, users should click the “Stop Guide” button.

Determines how frequently guiding adjustment coordinates are sent from the slit camera images to the TCS in order to keep your target on slit. For example, in the case shown here 1 in every 5 slit camera images taken will be used to adjust the TCS coordinates slightly to keep the target on slit during the spectra acquisition. This also means that only 1 in every 5 slit camera images are saved to the IGRINS hard-drives.

1. We recommend keeping this number low (below 3-5) otherwise the target is likely to drift off of the slit often during the spectra acquisition.

2. If your exposure time is longer than 1.63 seconds (i.e., you are in a field of fainter stars and a longer exposure is required to see the target) it is best to change this value to 1.

These buttons are used to set up the guiding and nods.

1. “go R”: will set the center of the reference pixel (see box 2) to where you have clicked on the slit camera image in either boxes 2, 3, 5, or 6. When you find the target in the slit camera image you should click the center of the object in any of the fore mentioned boxes and click “go R”->”Single” (box 13). If the target is not centered on the reference pixel in box 2 and 3 after doing this, try clicking the center of the object in boxes 2 or 3 and “go R”->”Single” again. The center pixel of the object from the “go R” image is used to centroid the object on the A- or B-nod, so centering in this step is imporant.

2. “go A”: will put the centroid of the object in the “go R” position (or wherever the curser was last clicked on the slit viewing camera image in boxes 2, 3, 5, or 6) in the centroid of the A position on the slit. This is the position the target should be put in before a user clicks the “Guide” button on box 14. Once guiding has begun, the user can begin acquiring spectra using the DTP.

3. “go B”: same as outlined for “go A” but for the B-nod position. In typical observing with no errors, the IGRINS software will move between nods (as outlined in the DTP) without human intervention.

4. Note: Occasionally there are issues with the target slewing correction to the nod positions (particularly the last A frame in an ABBA nod) so users should verify the correct target position on slit at the beginning of every spectral frame taken. If a user notices an issue with the position of the target on the slit the spectra acquisition should be aborted using the DTP, stop guiding, reset the guiding (see Autoguiding; be sure to put the target at the desired nod position using “go A” or “go B”), and begin re-acquisition of the spectral frame using the DTP.

The exposure time for the slit camera image. 1.63 seconds corresponds to 1 fowler sample (the detector’s fastest possible readout time). Exposure times over 20 seconds will trigger an audio warning in the observing room, and a pop up box, but sometimes high exposure times are required to see faint objects with the slit viewing camera. The user should not be using high exposure times above 20 seconds when the target is bright (K Mag < 7-8) or there are bright objects in the frame of the slit viewing camera.

!! Important for Guiding !! This “send AG offsets to TCS” box must be checked when guiding is active! Otherwise the coordinate offsets calculated from the guiding software used to keep the target on slit will not be sent to the TCS to reposition the telescope meaning there will be no guiding.

Indicates the status of the read out for the slit camera image that was just acquired. If the status is not green the SCV or errors show up during a read out its possible TCS communication has been severed or there is an error with the SCV GUI. Usually closing the SCV and relaunching the SCV GUI will resolve the issue, but occasionally more detailed troubleshooting is required.

This will show a PSF histogram of the target on the slit for each slit camera image acquired. The offsets sent to the TCS are shown as little dots on the top of the histogram plot. Users can manually send TCS offsets if guiding needs a manual correction by clicking on the area of the histogram (if the target is falling off the slit slightly we recommend clicking inside the wings of the Gaussian for a reasonable correction). This needs to be closely monitored by users at all times to ensure the target is not off to the side of the slit consistently during observations (can cause issues with optimally extracted spectra), but especially in the case that there is a nearby companion to the target close to the slit that appears in this PSF box (sometimes off-slit guiding is preferable in this case).

Shows the manual correction fed into the guiding offset sent to the TCS. Users should only send a manual offset, by clicking the histogram in box 20 and clicking “SEND”, every 5 frames at most (!!) as too many manual corrections can aggressively skew the guiding in a negative way. If you find that the object keeps moving off of the slit without manual corrections, verify that the box in box 18 is checked and try resetting the guiding using the directions in Autoguiding (abort any currently acquiring frames before doing this!).