The Finding Chart and Acquisition tool is designed so that ULTRASPEC observers can plan their observations, pick comparison stars and choose suitable window sizes, whilst checking that the ULTRASPEC frame rate and signal-to-noise ratio in common filters satisfies their requirements.

The tool is written in Java, and you will need Java installed. Download the jar file usfinder.jar and start the tool by typing 'java -jar usfinder.jar'.


TNO Settings

The Telescope menu allows you to set the telescope parameters; plate scale, rotator offsets, field flips etc. For ULTRASPEC on the TNO, the settings should be the same as those shown here. If you edit these settings, usfinder will remember your changes, so edit with care!


usfinder main window

On loading the tool you are presented with the main window. This window allows you to specify your object either by co-ordinate or name. The name resolver is very fussy. See the Simbad Dictionary for instructions on forming correct names..

If the tool cannot resolve your objects name, enter the coordinates by hand. If both an object name and coordinates are entered, the tool will fetch an image centred on the given co-ordinates. It is worth including your object name even if Simbad cannot resolve it, as the object name is included on the finding chart.

This panel allows you to launch Aladin to display your object and the ULTRASPEC field of view. Simply enter your object name or coordinates and press enter. You can then launch Aladin which will display your object, the current ULTRASPEC field of view.

Ra, Dec and Rot. Posn.

The centre of the field of view, and it's rotation angle can be set either by entering values directly in these fields, or by dragging the field of view around in Aladin. Like all numberical entry fields in the tool, these values can be set by using the up and down arrows. Holding down SHIFT or SHIFT+CTRL whilst pressing the arrow keys will increment the values by larger amounts. Dragging the field of view in Aladin will update these values, and vice versa.

Whilst changing the window parameters and fields of view, the timing and signal-to-noise info will update. Make sure your setup gives suitable frame rates and signal-to-noise ratios

When you are finished and happy with your setup, make a note of these values, as well as the window parameters you chose. You will be able to save setups in the afternoon at the telescope, allowing very efficient observing!

Marking Target and Comparison stars

Once you have loaded an image, you need to indicate your target and comparison stars. This is done by first selecting the object in Aladin (either click on the object or draw a rectangle around the objects you wish to select by holding down the mouse button and dragging the mouse over the stars), and then clicking on the "Sel Targ" or "Add Comp" buttons. Your target will be identified by a red circle, your comparisons by blue circles. You can add as many comparison stars as you like, but if you add more than one, please indicate your first choice by annotating the view - see Aladin Extras below

Saving your finding chart

Once you are happy with your setup use the "File -> Publish..." option in the main window. This will produce a bitmap finding chart, complete with all setup information which can be attached to your phase I information page.....

Aladin Extras

Implementing the Finding Chart tool in Aladin allows you to use all the power of the Aladin application when planning your applications. The Aladin programme is complex and I highly recommend a leaf through the Aladin manual. A few individual features are worth pointing out:

  • You can annotate the view using the "Text" tool on the right hand panel. This is useful for indicating favoured comparison stars, noting blended objects or bright stars to avoid etc.
  • A useful tool is the SIMBAD pointer: enable it by using the top panels "Tools..." menu. Once enabled if you hover the cursor over that object, Aladin will query Simbad for objects near the cursor position.

Entering numerical values

The parameter values defining the windows are entered on the right-hand part of the GUI. You do NOT have to hit 'enter' to register values. Instead the values shown in the GUI are always the values that will be used if you save or post an application. A process runs which checks the current window parameters every second or so and estimates timing parameters from them which are displayed in the lower left panel. This process will also flag any problem values that lead to invalid window settings.

The numerical parameters support the following features:

  • Minimum and maximum values. You will not be allowed to set a value outside this range. Hit the page up or page down buttons to go set the parameter to it's maximum and minimum values, respectively.
  • Increment and decrement using the up & down arrow keys and the left and right mouse buttons.
  • 'Focus-follows-mouse' behaviour, i.e. as soon as you move the mouse onto a field, you can start to edit it. This means that you do not have to click the mouse on a field, so that clicking always implies an increment/decrement operation.
  • Automatic continuous increment / decrement by holding down the respective arrow keys or mouse buttons.
  • Acceleration of the automatic changes by a factor of 10 by holding down the SHIFT key at the same time, and by a factor of 50 by holding down both the SHIFT and CTRL keys.
  • Jumping through pre-defined values by holding down the CTRL key. This is only implemented for the NY parameter of the first window pair where it allows you to jump between the 'magic values' which give minimal pipe shifts in drift mode (see the ULTRACAM paper for full details of this). Note that the NX and NY fields are affected by the binning factors and will be restricted to multiples of the current binning factors. This also applies to the 'magic values', which will be skipped if they are not commensurate with the NY binning factor.

Sync Windows

When you bin the CCD, then it is possible to have identically binned windows which are nevertheless out of step with each other. For instance one window may have xbin=2, with unbinned pixels 4-5, 6-7, 8-9 etc ending up added together, while another may have 3-4, 5-6, 7-8 etc. These two windows are incompatible. To help make sure that you DO use compatible windows, the 'sync windows' button will be highlighted in orange whenever you choose incompatible settings with a standard setting for your chosen binning factors. Pressing it will immediately adjust the windows so that this is the case, or you can just adjust the windows until the button is no longer highlighted. The standard setting is defined to have pixel boundaries between the unbinned values of 512 and 513 in both X and Y. There may be a border of unused pixels depending upon the binning factors.