Finder Users Manual

...Using the window manager menu (COAST finders) 
...From an xterm (COAST finders)
...From an xterm (DIMMWITs)

File  Menu

Open Config...
Save Config
Save as...
Data Parameters...
Connect Telescope
Disconnect Telescope
Exit

View Menu

Toolbar
Statusbar

CCD Menu

Connect CCD
Disconnect CCD
Fullscreen
1D  DIMM Mode
2D  DIMM Mode
Transverse  DIMM Mode

Tracking  Menu

Select Target
Select Region
Subframe
Start Tracking
Stop Tracking
Manual Control
Save Movie
Stop Recording Movie

Help  Menu

  About...

CCD Readout

Binning
Exposure
Clear Charge

Video Display

Stretch Contrast
Correct Gamma
Fast 1D Grid
Fast 2D Grid
Fast Trans Grid
Show Scale

Status

X and Y Offset Signals
Telescope Secondary and Beam Splitter Status
Progress Bars

Data Saved
Max Flux

Status Bar

Introduction

• Finder is the program and associated hardware used for source acquisition and seeing measurement at COAST.
• Finder allows aquisition of targets to within autoguider range with a minimum of user intervention.
• There are also two portable finders used primarily for seeing measurement. Each is known as a "Differential Image Motion Monitor Which Is Transportable" (DIMMWIT).
  

• Additional features:
• A convenient means of manual telescope pointing adjustment.
• Indicators of current telescope status.
• Fast readout modes for Differential Image Motion Monitor (DIMM) seeing measurements or autoguider performance testing.

Design Overview

• A digital camera and zoom lens located on the optical breadboard.
• At the time of writing the focal length was set to 135mm but can be changed.
• NOTE: The camera is only powered when the telescope beamsplitter is moved to the "in" position.
• A Universal Serial Bus (USB) interface, which:
• interfaces the camera with the computer
  
• clocks the camera CCD
• and reads the digitised CCD output.
• It is powered via the USB cable and hence is independent of the camera supply.
• A single board computer in the electronics housing.
• It is connected to the COAST network via ethernet.
  
• It runs finder under Red Hat Linux and can be logged into like any other linux machine.
• The passwords for root and coast are the same as those for the other computers in the bunker.

• Finder is an X windows application like any other and can be viewed using any X server.
• By making the appropriate network connections all the telescope finders can be viewed on the one screen.
• All the bunker X servers have popup menus that do this for you (see " Launching Finder " below).

• There is no camera lens, telescope optics are used to obtain a focus.
• The camera head has the Pentax M42 camera thread common in Meade and Celestron telescopes.
• There is also an adaptor for attachment to 1" eyepiece mounts.
• The single board computer is in a blue box also containing a power supply and interface sockets.
• The single board computer is connected directly to the user's computer via peer-peer ethernet. 
  

Launching Finder...

• Finder runs on single board computers as a Linux process with an X display.
• Hence its user interface can be displayed on any X terminal.
• For convenience, user "coast" on any COAST bunker machine can log into any finder computer or remotely launch finder without a password using ssh (OpenSSH secure shell).
• The DIMMWITs have different passwords which should be written on each machine.
  

• Display all finders on one X display.
• The finder display should be next to the telescope controller display. Finder and the telescope controller work closely together during the acquisition phase.

• Use a display with many colours. Finder works on our older X displays (caliban and the Mullard xterms) but images are poorly rendered.
  
• Do not use the "xhost +... telnet... setenv DISPLAY..." method to display finder remotely. Ssh is more secure and sets up the X11 display forwarding automatically.
  

...Using the window manager menu (COAST finders only)

• The menu launches an  ssh script that runs the remote application but displays it locally.
• No password is required.

• Hold the left mouse button down while on the display background to invoke the menu.
• Move the mouse to the "Finders" submenu.
• Select the telescope you want to launch a finder for, or "All Finders" if you want to run them all.
• Let go the left mouse button and wait a few moments.

• The finder for beam 1 is at the lower left and for beam 4 is at the upper right.
• Each finder and its ancilliary dialog boxes display the name of the host telescope in the title bar.
• There is not enough room on any of the bunker computer displays to display all the finders at once. As a compromise, the inner and outer west telescope finders overlap because the telescopes share a light path and are unlikely to be used simultaneously.

...From an Xterm (COAST finders)

...From an Xterm (DIMMWITs)

• To use the internally stored finder, from an xterm, type

ssh coast@dimmwit finder

• Enter the password when requested (NOTE: If you are using an older ssh it can take half a minute for the password prompt to appear. I don't know why!)
• Finder will be displayed after a few seconds.
• To use the version on your host PC instead, type ssh coast@dimmwit remotefinder
• Note that you will not be able to connect to COAST telescopes and hence the telescope control interface features (autoguiding, display of telescope status) will not be available. Tracking, manual guiding and target selection are available but of limited use in the DIMMWIT context.

User Interface Layout

• The title bar displays the name of the host telescope of this particular finder.
• The menus and toolbar are used to initiate actions.
• All toolbar items have menu equivalents.
• The display area shows the image seen by the camera CCD. It also displays:
• the target crosshairs
• the subframing selection box
• the fast read region grid.
  
• The CCD readout options give the user control over how the CCD is clocked and hence how the charge is digitised.
• The display options postprocess the CCD images for display in the display area.
• These options do not alter the data itself (for example, when data is saved as FITS files).
• They only change how it is displayed.
• The status message area displays program messages to the user.
• Real showstoppers will not appear here, they will have their own dialog boxes.
• The offset area displays the X and Y difference in CCD pixels between where finder thinks the stellar image is and where it should be (the crosshair position).
• If you are using a COAST finder, this offset is sent to the telescope controller, which in turn tries to minimise it as part of the acquisition process.
• The Data Saved progress bar indicates how much of the current movie has been saved so far.
• The Max Flux progress bar indicates the brightness of the brightest pixel in the current frame, as a fraction of the brightest value possible.
  
• Finally, if you are using a COAST finder, the status of the telescope secondary mirror and beam splitter are displayed on the lower right.

Online  Help

• Tooltips. If the mouse cursor is held steady over a control a tooltip will pop up with a brief description of that control.
• Context sensitive help. Many controls have longer built in descriptions. These are accessed by clicking on the " " icon and then the control of interest.
• Status messages. When a menu item is highlighted, a brief description of its functionality appears in the status bar (unless you have turned off the status bar).

The  Menus and Toolbar

• Accelerators are underlined characters that allow selection of menu items without the mouse.
• Pressing Alt+[character] where [character] is an underlined character selects a main menu from the menu bar.
• Once such a menu is open, pressing an underlined character of a menu item on the keyboard selects that item.
• Some menu items have keyboard shortcuts.
• Pressing the keyboard shortcut combination displayed causes that action to be executed immediately whether the menu item is displayed or not.
• However, if the menu item is disabled the shortcut is ignored.
  

• The toolbar icon if it has one.
• The menu entry as displayed by finder.
• The keyboard shortcut if it has one.
• Accelerators are displayed as underlined characters.
  

File  Menu

Open Config...

The single board computer at each telescope contains a configuration file that lists aspects of finder operation that are unique to that telescope. Finder running on each telescope configures itself according to this file. The contents of the file are described in more detail here .

The default file name is "finder.conf" but with this menu item the user can choose to load a different configuration as long as it has a " .conf" suffix.

Save Config

Saves the current configuration under the filename finder.conf . NOTE: If the crosshair position changes while finder is running, finder will automatically update finder.conf when quitting

Save as...

Saves the current finder configuration under a new name. This might be useful if the user wants to record the current crosshair position before doing experiments where it will be temporarily changed.

Data Parameters... Shift+P

Invokes the data file dialog, which tells finder (or DIMMWIT) how to save files when the " Save Movie " action (in the tracking menu) is chosen. The file format depends on whether finder or DIMMWIT is in 1D DIMM mode or not. Normally, the file is a 3D FITS file with the image stored in the x and y dimensions and successive images in time in the z dimension. In 1D DIMM mode, the file is a 2D FITS file with spatial information in x and successive snapshots in time in the y axis. See " Save Movie " and " 1D DIMM Mode" for more information.

In the file parameters section:

• Under "Base file name" you can enter the path and file name you want to save files to. On COAST finders, the default directory is recommended as it is NFS mounted to oberon and has much higher capacity than the local silicon hard drive. On DIMMWITs you should choose a directory that is NFS mounted on your computer, again because the local silicon hard drive capacity is limited (information on how to NFS mount your computer's hard drive on DIMMWIT can be found here). 
• If you choose "Insert date/time in filename when saving" the base filename you have specified above will have the current date and time (down to the millisecond) inserted. Hence even if you just keep pushing the " " button over and over, each file you make will have a unique file name. Note that this option is forced on if you want to acquire more than one file on a single trigger.
• The "On trigger acquire" allows you to specify how many files to sequentially acquire and how many frames each one should have.
• This allows you to save up to 99 files sequentially without having to manually initialise the acquisition of each one.
• If you want a simple 2D FITS file, specify one file with one frame.
• Be aware that a frame can take several seconds to acquire if you are in full screen mode so a large series will take a while in that case.
• On the other hand, each image in the DIMM modes only takes a few milliseconds to acquire so you can take large numbers of frames.
• NOTE: The maximum number of frames in 1D DIMM mode is 131072 ( 2¹⁷ ). In 2D and transverse mode it is 65536 (2¹⁶). You do not have to remember these numbers, if you type in a larger number than 131072 it will be automatically reduced to this maximum and if you try to acquire a 2D DIMM file with more than 65536 frames you will be warned and the number will again be reduced to the allowed maximum.
• 131072 frames is just over 4 minutes 22 seconds in DIMM 1D mode, 65536 frames is just over 3 minutes 16 seconds in 2D DIMM mode.
• The "Acquire until stopped" item is deprecated and has been disabled.
  

In the FITS parameters section:

• You can record a brief description in each of the fields provided or leave them at their default settings. This information will be written into a standard FITS header when finder saves the file.
  

Connect Telescope Shift+T

(NOTE: This command will not work with DIMMWIT unless it is on the COAST network.)

Connects this finder to the telescope controller via local ethernet. If the connection is successful the " Disconnect Telescope" menu item and button will become available, otherwise there will be an error dialog and you should refer to the   troubleshooting guide for suggestions as to what to do next.

The telescope controller IP address and the port number to use are determined by the configuration file . The port number is important because the telescope controller uses it to distinguish which finder it is talking to. The appropriate port numbers are here . It is important to get the port number right, as it is otherwise possible to have a finder feeding signals back to a different telescope!

NOTE: If finder can't find or does not understand its configuration file, it will default to port 2700 (the centre telescope). So if a finder is unexpectedly communicating with the centre telescope, look for a missing or broken finder.conf.

  Disconnect Telescope Shift+D

Disconnects finder from the telescope controller. If finder is connected to the telescope controller and the latter program forces disconnection (for example, by quitting), finder now also disconnects gracefully .

Exit Ctrl+Q

Quits finder. If the configuration has changed (new crosshair position) finder will inform you before exiting.

NOTE: Finder is reasonably robust when told to quit unexpectedly while connected to everything and tracking. However, it is best not to tempt fate and to shut it down gracefully:

• Click on the " " to disconnect from the telescope.
• Click on the " " to disconnect from the CCD.
• Select "Exit" from the "File" menu.

View Menu

Toolbar

Hides/shows part of the toolbar. Of limited use.

Statusbar

Turns status messages (at the bottom of the display) on/off.

CCD Menu

  Connect CCD Ctrl+C

Connects finder to the CCD controller. If all is well, readout will begin immediately. If not, you will be informed and should refer to the troubleshooting guide for ways to rectify the problem.

NOTE: If the camera head does not have power (for example, a telescope beam splitter is out) the display will remain dark.

  Disconnect CCD Ctrl+D

Disconnects finder from the CCD controller. If you try to quit finder before doing this you will see an error message asking you to disconnect first.

  Fullscreen Ctrl+F

Causes finder to start reading out the entire CCD. The following operations are cancelled if they were running:

• Subframing.
• Tracking.
• Either DIMM mode.

This is a good button to press if something has gone wrong, as all feedback is cancelled and the entire field of the CCD is displayed.

  1D DIMM Mode Alt+1

Initiates high speed CCD readout in a way that is suitable for one-dimensional DIMM measurements.

1D DIMM mode tries to maximise readout rate for seeing measurements:

• Readout is initiated by a periodic USB interrupt to the microcontroller.
• Firstly, 64 lines of CCD charge are clocked into one line, the readout register.
• Secondly, 64 pixels from the readout register are each clocked out and digitised.
• The results from the readout are sent to the single board computer over the USB link.
• The cycle repeats every two milliseconds.
•  The result is spatial information in the horizontal dimension at 500Hz.

Note:

• Because there is no charge clearing, charge produced anywhere on the CCD will eventually be read out. Hence:
• There are many 64x64 regions on the CCD besides the corner that are also useful.
• These regions are marked out when the "Fast 1D Grid " check box is ticked.
  

1D DIMM mode also differs from normal readout in other ways:

• The display changes to display the 64 pixel line of charge.
• Most controls are disabled.
• 1D DIMM mode can be stopped by selecting " Fullscreen".
  
• Selecting " Save Movie" produces a 2D "strip chart" FITS file:
• The horizontal dimension is spatial.
• The vertical is time in 2ms increments.
• Up to four minutes of data can be saved.
  

Dropouts in acquisition files can occur if acquisition is disturbed. Hence:

• Data is saved in finder computer memory and saved to file after the event.
• Don't move the mouse or interact with the display in any way while saving movies.

  2D DIMM Mode Alt+2

Initiates high speed CCD readout in a way that is suitable for two-dimensional DIMM measurements.

NOTE: This mode works with both MX516 and HX516 cameras whether they have had the the hardware modification described above or not.

2D DIMM mode tries to maximise readout rate for seeing measurements:

• Readout is initiated by a periodic USB interrupt to the microcontroller.
• A 64x32 pixel region is read out. It is binned 4x4, so the result is a 16x8 array of data.
• The cycle repeats every three milliseconds.
•  The result is spatial information in the horizontal dimension at 333Hz.

Note:

• Because there is no charge clearing, charge produced anywhere on the CCD will eventually be read out. Hence:
• There are many 64x32 regions on the CCD besides the corner that are also useful.
• These regions are marked out when the "Fast 2D Grid " check box is ticked. 
  

2D DIMM mode also differs from normal readout in other ways:

• The display changes to display the 16x8 rectangle of charge.
• Most controls are disabled.
• 2D DIMM mode can be stopped by selecting " Fullscreen".
  
• Selecting " Save Movie" produces a 3D FITS file just like those produced during ordinary readout, except that:
• The time interval between frames is fixed at 3ms.
• The maximum number of frames is 65536 (about 3 minutes 16 seconds of data).

Dropouts in acquisition files can occur if acquisition is disturbed. Hence:

• Data is saved in finder computer memory and saved to file after the event.
• Don't move the mouse or interact with the display in any way while saving movies.

  Transverse DIMM Mode Alt+T

• Readout is initiated by a periodic USB interrupt to the microcontroller.
• A 64x32 pixel region is read out. It is binned 8x2, so the result is an 8x16 array of data.
• The cycle repeats every four milliseconds.
•  The result is spatial information in the horizontal dimension at 250Hz.

• Because there is no charge clearing, charge produced anywhere on the CCD will eventually be read out. Hence:
• There are many 64x32 regions on the CCD besides the corner that are also useful.
• These regions are marked out when the "Fast Trans Grid " check box is ticked. 
  

Transverse DIMM mode also differs from normal readout in other ways:

• The display changes to display the 8x16 rectangle of charge.
• Most controls are disabled.
• Transverse DIMM mode can be stopped by selecting " Fullscreen".
• NOTE: Sometimes this does not work.
• If this happens:
• Go into 1D DIMM mode by clicking on "".
• Select " Fullscreen" again.
  
• Selecting " Save Movie" produces a 3D FITS file just like those produced during ordinary readout, except that:
• The time interval between frames is fixed at 4ms.
• The maximum number of frames is 65536 (about 4 minutes 22 seconds of data).

Dropouts in acquisition files can occur if acquisition is disturbed. Hence:

• Data is saved in finder computer memory and saved to file after the event.
• Don't move the mouse or interact with the display in any way while saving movies.

Tracking  Menu

  Select Target Alt+A

Changes the cursor into the target selection shape. If it is then clicked in the video display area:

• The target crosshair moves to the clicked position.
• The cursor changes back to its default shape.
• To move the crosshair again, choose " Select Target" again.

If you are using a COAST telescope finder, the crosshair marks the position on the CCD image plane that the telescope controller will guide stars to.

• It is functionally equivalent to the crosshairs on the old finder system.
• When finder is tracking the telescope will try to guide stars to the crosshair position.
• Hence the crosshair position should be set optically congruent to the autoguider.
  
• As with the old system, this is normally done by setting the crosshairs to the image position of the artificial star return beam from the telescope flat/corner cube.

  Select Region Alt+R

Changes the cursor into the region selection shape. To select a region in the CCD image:

• After choosing this option, move the cursor to one corner of the region you want to select.
• Hold the left mouse button down.
• Move the cursor to the opposite diagonal of the region. A green bounding rectangle will change shape as the cursor moves.
• Let the left mouse button go.

In normal use a region is selected around the image of a star that is to be acquired. When that region is later subframed it reads out much more quickly than the full CCD field. The region can also be used to exclude stars that are not of interest.

  Subframe Alt+U

If a region has been selected, this action initiates subframing - that is, only the region of the CCD that has been selected is read out. Tracking is not initiated.

Subframing improves the readout rate, as less time is required to clock the CCD and to transfer the data over the USB cable. This is useful in situations where visual real-time feedback is important,  or as a precursor to tracking or acquisition of 3D DIMM files.

  Start Tracking Ctrl+T

If used on a COAST telescope finder, this is the action used to automatically steer a star image to the crosshairs and hence hopefully within autoguider range.

If a region has been selected, this action initiates subframing (if that is not already occurring) and tracking. Tracking consists of the following actions:

• Subframe readout of the selected region begins.
• The position of the brightest pixel in the region (such as a target star image) is recorded:
• Relative to the region boundary.
• Relative to the target crosshair.
• As the brightest pixel position changes, the subframing region moves to maintain its initial spatial relationship with the pixel.
• The error relative to the crosshairs is displayed.
  
• On COAST telescope finders (with finder connected to the telescope controller):
• Once a second, the position of the brightest pixel relative to the crosshair is sent to the telescope controller.
• The controller tries to steer the star image to the target crosshair (if it has been told to).
  
• If the star is close to the crosshair position, finder tells the telescope controller that the star is acquired.
  

Hence, as the star image moves the subframe region moves with it. The star can be tracked across the entire field without resorting to slow full frame readout. Subframing in this way also allows the user to exclude stars that are not of interest.

  Stop Tracking Ctrl+S

Stops any ongoing tracking. The most recent subframe region is retained and continues to be read out. However, no valid data is sent to the telescope controller. To recommence tracking:

• If the object of interest is still in the field, select " Start Tracking".
• If it is not, select " Fullscreen", select a new region and then start tracking.

  Manual Control Shift+C

If the finder is connected to a COAST telescope, this action allows the user to make manual adjustments to the telescope pointing by clicking and dragging on the star field. To use it:

• Select " Manual Control".
• Move the cursor into the video display area and to some arbitrary position. The cursor changes into a hand.
• Hold the left mouse button down.
• Drag the mouse cursor in the direction you want the star field to go.
• Moving further away from your starting point makes the telescope pointing change faster.
• Let go the left mouse button when the field is where you want it.
• The cursor changes back to its default shape.
  

All this action really does is send a fake error signal to the telescope, which then tries to correct it using pointing changes. As with a real error signal, a conversion is done by the telescope controller into Az and El components. Hence dragging vertically should result in image motion that also appears vertical. 

  Save Movie Shift+M

Initiates the saving of a sequence of one or more consecutive FITS files, each consisting of a set of one or more consecutive images. To change the file saving parameters invoke the data file dialog using " Data Parameters" first.

The files you get after you select this option depend on whether you are in 1D DIMM mode or not.

If you are acquiring normally or are in 2D or transverse DIMM mode:

• The files are 3D FITS files.
• The X and Y dimensions are the binned pixel dimensions of the frame, or the region if subframing was active at the time.
• Each pixel has depth 16 bits.
  
• The Z dimension is time (3ms between frames in 2D DIMM mode, 4ms in transverse DIMM mode) and of depth as specified in the data file dialog.

If you  are in 1D DIMM mode:

• The files are 2D FITS files.
• The X dimension is 64 unbinned pixel intensities.
• Each pixel has depth 16 bits.
  
• The Y dimension is time in 2ms increments.
• Hence the files are strip charts.
  
• Finder should be left undisturbed while acquiring, otherwise there may be dropouts in the data.

In either case:

• When you start saving the movies:
• The " Save Movie" icon is disabled (greyed out).
• The " Stop Movie" icon is enabled.
• You can interrupt movie saving by selecting " Stop Movie".
  
• You can tell when movie saving is completed:
• The " Save Movie" icon becomes re-enabled.
• The " Stop Movie" icon becomes disabled.
• The computer beeps.
  

  Stop Recording Movie Shift+H

Interrupts the recording of a sequence of FITS files.

NOTE: Using this button is not recommended:

• The file that is interrupted will be shorter than its FITS header says.
• Your FITS file viewer will probably complain.
• DIMM mode acquisitions will not be interrupted until the current file has finished acquiring (or sometimes the next one).

You may be able to recover the saved data manually:

• Look at the file length and FITS header to work out how many records were actually saved.
• Manually edit the FITS header to agree with this.

Help  Menu

About...

Displays a brief message about Finder.

The Panel Controls and Indicators

CCD Readout

Binning

Changes the amount of charge binning in the X and Y directions.

Binning is the adding together of charge from neighbouring pixels prior to readout.

• As there is a fixed noise associated with readout, increasing the binning can improve the signal to noise ratio at the cost of resolution.
• Refresh rate is also increased as less data is transferred via the USB cable to the finder computer.
• A full unbinned frame can take several seconds to read out. Recommendation: subframe the region of interest before reducing the binning.

Binning can be changed "on the fly" even while subframing or tracking.

• The change in resolution is accounted for in display and tracking signals.
  
• However, reducing binning can be dangerous while tracking:
• The first new frame has low signal (possibly the previous binning has cleared the charge).
• Mistracking errors may result.
• Recommendation: if tracking, reduce binning one step at a time.

The binning parameter is ignored in either DIMM mode.

Exposure

Sets the exposure time between frames.

• Use long exposures for faint targets.
• Exposure length can be changed "on the fly" even while subframing or tracking.
• The true exposure time depends on whether "Clear Charge" is set, see below.
• Exposure time is ignored in either DIMM mode.
  

Clear Charge

This option clears CCD charge prior to an exposure.

Unchecking it reduces readout time. However, image artefacts are also introduced:

• The CCD charge readout channels are not light sensitive.
• If charge clearing is on, the readout time does not have to be factored in to the exposure time.
• If charge clearing is off, the CCD is exposing and reading out at the same time.
• If the CCD is subframing, the clocking mechanism can move charge from other parts of the chip into the readout region.
• This charge is interpreted as part of the image.
• Hence only uncheck this option if the rest of the field is reasonably dark or you are doing full frame readout or you wish to exploit this charge transfer property in some way.
• "Clear Charge" is ignored in either DIMM mode.
  

Video Display

Stretch Contrast

This option linearly maps the scale of intensities in the image to the full range of the display:

• Images are 16 bits deep but the display is (usually) 8 bits deep.
• High dynamic range images are compressed for display.
• Low dynamic range images (of faint sources) are expanded for display.
• Recommendation: Do not compare source intensities between running finders while contrast stretching is on.

Correct Gamma

Corrects for the nonlinear intensity response of a cathode ray tube display. Hence a linear relationship between photon flux and displayed intensity is produced.

Turn this option off if you have a linear display (such as an LCD monitor) or your display hardware already compensates for monitor gamma (if you are using a Silicon Graphics computer, a Macintosh or some PC display adaptors).

Fast 1D Grid

Displays a red grid in the video display area that marks the fast readout regions useful in 1D DIMM mode . As long as all star images in a DIMM set are in the same valid rectangle of the grid and are separated horizontally, useful data will be obtained.

Fast 2D Grid

Displays a blue grid in the video display area that marks the fast readout regions useful in 2D DIMM mode. As long as the star images in a DIMM image set are in the same rectangle, useful data will be obtained.

Fast Trans Grid

Displays a blue grid in the video display area that marks the fast readout regions useful in Transverse DIMM mode. As long as the star images in a DIMM image set are in the same rectangle, useful data will be obtained.

Show Scale

Displays the angular sky scale on the video display area.

Not yet implemented and disabled.

Status

X and Y Offset Signals

Display of the offset being sent to the telescope controller (if it is connected to finder).

• The offset is the distance in unbinned CCD pixels between the brightest pixel being tracked and the crosshair target position.
• The numbers become more approximate as binning is increased.
• The telescope controller tries to move the bright spot towards the crosshairs by adjusting telescope pointing (if it is connected and has been told to).

Telescope Secondary and Beam Splitter Status

When finder is connected to the telescope controller, the positions of the telescope secondary mirror and beam splitter are displayed:

• These panels are arranged to look like a ray-trace of the light through the telescope.
  
• They cannot be used to move telescope optics.
• Their appearance is as follows:
  

Status	Secondary	Beamsplitter
Out
Moving
In

Progress Bars

Data Saved

• During movie saving, this indicator displays how much of the current movie has been saved so far.
• This indicator is inactive when movies are saved in any of the DIMM modes.
  

Max Flux

• During acquisition, this indicator indicates as a percentage:
• The intensity of the brightest pixel in the most recently acquired frame, divided by...
• The maximum intensity possible. For the HX516 and the MX516, this value is 65535.
• The intention is to provide quantitative feedback for the user regardless of the status of the Stretch Contrast option.
  

Status Bar

At the lower left of the finder user interface, messages to the user are sometimes displayed.