Finder and DIMMWIT Quickstart  Guide


This guide applies to:
Finder and DIMMWIT use the same hardware and software, but DIMMWIT is more self-contained.

Starting Finder
Using the window manager menu
From an Xterm
Starting DIMMWIT
Connections and powering up
From an Xterm

Quick Tour
The essential controls
Online help
Telescope status indicators
Acquisition at COAST (Finder)
Initial Tasks
Alignment
Acquiring a Star
Seeing Measurements (Finder and DIMMWIT)
Acquisition
Recording r0 Data
Recording t0 Data
If You Plan to Use 1D DIMM Mode
If You Plan to Use 2D DIMM Mode
If You Plan to Use Transverse DIMM Mode
In Any DIMM mode
Quitting


Starting Finder

Using the window manager menu

Finder can be launched from the popup "Utilities" menu on any of the X consoles in the COAST bunker. Make sure you are logged in as "coast", then move the mouse cursor away from any open applications.
Menu Image

The window placement is the same as for the autoguider display. The finder for beam 1 is at the lower left and for beam 4 is at the upper right.

From an Xterm

Make sure you're logged in as "coast" and then type

ssh cstfindern finder &

where n=1..5 . A table of finder computer names versus telescopes is here .


Caveat: The display will work but won't look very pretty on our older X displays (caliban and the Mullard xterms) due to the low number of colours available.

Starting DIMMWIT

Connections and powering up

To run DIMMWIT you must firstly make sure that your computer has been configured to connect to DIMMWIT and to save DIMMWIT data. See here for how to do this.

DIMM connection overview
In no particular order:
Powering up:

From an Xterm

Assuming your computer has been set up to work with DIMMWIT (see here for how to do this):
ssh coast@dimmwit finder

Quick Tour

The essential controls:

annotated finder screenshot

Online help

Telescope status indicators


Status
Secondary
Beamsplitter
Out
Secondary Out
Splitter Out
Moving
Secondary Moving
Splitter Moving
In
Secondary In
Splitter In

Acquisition at COAST (Finder)

Initial Tasks

On each finder you have started:

Alignment

At the start of the night:
If the crosshair is in the wrong place:

Acquiring a Star

To acquire a star semi-automatically:
 Stretch Contrast Option

...if the display is faint. This linearly maps the dynamic range of the image to the entire display range of the monitor.
Now do it all over again with the secondary in:
Your star is now acquired.

You can acquire on all open finders at once, for example, selecting a star readout region on one finder while others are guiding the star image to the crosshair.

Seeing Measurements (Finder and DIMMWIT)

For seeing measurements:

Acquisition

 Stretch Contrast Option
...if the display is faint. This linearly maps the dynamic range of the image to the entire display range of the monitor. You can also look at the flux bar...
Brightest pixel flux as percentage of maximum
...to determine how appropriate your exposure settings are.

Recording r0 Data

Data recorded in this mode can be used to establish the distance scale of atmospheric seeing, known as r0. The technique is to repeatedly read out a CCD subframe containing the two star images over a long period of time and save the images to disc.
Data Saved progress bar

...will monitor the progress so far.

Recording t0 Data

Data recorded in this mode can be used to establish the time scale of atmospheric seeing, known as t0. The technique is to repeatedly read out a CCD subframe containing the two star images at high speed with precise and accurate timing, and save the images to disc. Three fast readout modes are available:
If You Plan to Use 1D DIMM Mode:
Fast 1D Grid Option
DIMM grid image
If You Plan to Use 2D DIMM Mode:
Fast 1D Grid Option
DIMM grid image

If You Plan to Use Transverse DIMM Mode:
Fast Transverse Grid Option
DIMM grid image
In Any DIMM Mode:


Quitting Finder

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

Last updated  19th October 2004  by bodie@mrao.cam.ac.uk