Finder Documentation

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Reference Manual

Installing a Previously Configured Finder

Finding Finder
Installing Finder
Telling Ssh on the Bunker Computers About the New Finder
Alignment

Configuring a Finder Computer from Scratch

Before You Begin
Setting Up
Initial Configuration
Installing Linux
Change Default Passwords!
SSH Sshenanigans
Set the Coast User ID
More SSH Sshenanigans
Mounting Oberon as an NFS (Network File System) Drive
The CCD Drivers
The Finder Application
Check it All Works!
Time Synchronisation (optional)

Building Finder

The Application
The Drivers

Running Finder as a Transportable DIMM

Introduction
Setting up your host PC
Connections
Running finder
Shutting down
Actions which have been found to crash finder or the controller (don't do them!)
Actions which will reduce the scientific value of the data

Converting a HX516 to run in DIMM mode [deprecated]
Appendices

The Finder Configuration File
Enumeration Reference

Installing a Previously Configured Finder

A finder computer at COAST has failed for some reason, but being the forward thinking (and modest) individual I am, I have programmed and tested a spare board for you. This section describes what you need to get this board running. The procedure is not quite plug-and-play but you should be back on the air in a matter of minutes, fast enough to recover during an observing run.

Finding Finder

The spare board is in a blue plastic carry-case that looks something like an oversized lunchbox. At the time of writing it was stored at the south end of the COAST bunker on a table along with other finder spare parts. The finder that has failed will be in the telescope electronics enclosure, horizontal, in the top of the rack.

The case containing the spare Arcom board and accessories.

Image of SBC in telescope housing

The location of an installed board in a telescope electronics housing.

Installing Finder

Take the usual anti-static precautions when handling a disconnected board.
The spare finder is called "cstfinderx". The COAST network knows about this hostname and the corresponding IP address, so the board will work immediately on connection.
Go out to the failed telescope with the spare board and a phillips head screwdriver.

There are three board connectors: power, USB and ethernet.
The USB connector can be plugged in the wrong way around so note the position.
Remove the power connector first, then the USB and ethernet.
Swap the boards.
Plug in the USB and ethernet, then the power connector.

Go back into the bunker.

Note the details of the failed computer in this table.
Delete the entries for the failed computer in ~coast/.ssh/known_hosts on every bunker PC (there is an explanation about this here).
Now log in from the bunker and change the finder settings:

ssh coast@cstfinderx (you might get a warning about authenticity, ignore it).
Become root with su.
Type rw to make the root partition writeable.
Edit /etc/config/network/hostname to be the name of the computer you are replacing.
Edit /etc/config/network/interfaces/eth0 so that IPADDR is the IP address of the computer you are replacing.
Edit /etc/hosts to change the cstfinderx hostname and address to those of the computer you are replacing.
exit to become coast.
Edit ~coast/finder.conf so that the name and port are those of the computer you are replacing.
Become root and reboot to get the new settings to take effect.

Tell SSH on the bunker computers about the new finder:

ssh from an xterm to the new computer. You will get a warning about authenticity, ignore.
Login as coast.
Logout.
The ssh tables on your console machine are now updated.

You should now be able to run finder as usual, even with the pulldown menus.

Alignment

The crosshair position for the new computer will most likely need to be changed. Ideally you would set it in the same way as you would at the start of the night, but at this point you're probably in a hurry and not too happy about how your observations are going. Hence:

Start finder on the telescope you've just replaced the computer on.
Switch on the artificial star and see where it falls in the finder field. This is the corner cube return beam.
Move the crosshair to that spot (you can find out how to do this in the quickstart guide). No need to send the telescope to position 0, 0.
Switch off the artificial star.
Start observing!
The next observer will refine the crosshair position if necessary as part of the normal alignment procedure.

Configuring a Finder Computer from Scratch

As a result of some cataclysmic event at COAST, you find yourself with a blank Arcom single board computer and an urgent need to reprogram it as a finder. Possibly a board has failed and you have a replacement, or a board has had its drive wiped as a result of an accident or malicious hacking. The configuration of a replacement board is non-trivial and this documentation, the distillation of many weeks of learning on my part, should help a lot. Even if you want to use a different single board computer or just want to know how finder is set up it will help to read this.

The general strategy is to do only the basic configuration as a stand-alone system, install the board on the COAST network and complete the installation (more conveniently) over the network.

Before You Begin

You will need the following:

An Arcom SBC-GX1 single board computer
A CD-ROM drive and IDE cable
The Arcom development disc (in the Arcom development kit). Note: the disc is labelled "Development Kit CD" and "VERSION 2 Issue 2". We also have "Issue 1", which is deprecated, and various RedHat installation discs which you should not need.

The CD in its case.

A spare monitor, keyboard and mouse
An Arcom power supply for the computer (in the Arcom development kit)
A VGA adaptor for the computer (in the Arcom development kit)
A power supply for the CD-ROM, as found in most desktop computers.

The SBC-GX1 and the VGA adapter cable required to connect it to a monitor.

Note: The "Arcom Development Kit" is a carry-case that looks like a big blue lunchbox containing all sorts of useful Arcom accessories and hopefully a spare board. It should eventually be found at COAST along with the spare finder parts.

You will also need the following information:

A basic knowledge of linux, including the ssh secure shell, the vi editor and networking.
Hostname and IP for the computer (at the time of writing these were as listed here).
IP numbers for the COAST gateway and name server (131.111.50.62 and 131.111.48.8 respectively at the time of writing).

Setting Up

Before applying power to the single board computer:

Take the usual anti-static precautions for handling static sensitive devices.
Move the link "LK7" to connect the leads closest to the battery. This connects the battery to the CMOS RAM, otherwise the computer will forget CMOS settings when it is powered down.

Move this link towards the backup battery.

Connect the mouse, keyboard and monitor. The monitor requires a special adaptor cable, see the above illustration.
Connect the CD-ROM drive and CD-ROM power.
Place the Arcom development disc in the CD-ROM drive.
Finally, connect the Arcom power supply to the computer.

Initial Configuration

While the computer is booting, hit the <DEL> key to edit the computer BIOS:

In "Standard CMOS Setup", set the date and time to the current UT.
In "BIOS Features Setup", set the boot sequence to "C, CDROM, A"
In "Chipset Features Setup", enable the USB controller but then leave USB legacy support disabled.

All other values can be left at their defaults.
Save and exit the BIOS setup.

Installing Linux

As the computer reboots, hold the <ALT> key down to make it boot from the CD.
When the install program asks about the boot source, type "master".
A Debian-style configuration utility will start. You can tab between options and select or deselect items with the space bar. <ENTER> will activate buttons.
Select custom install.
Of the optional packages, only install FTP, telnet, ssh and sshd.

Enter the network configuration parameters as requested. A list of IP addresses for the existing finders is here. DHCP should be turned off!

All other configuration options can be left at their defaults.
Wait while installation is carried out (a few minutes).
The computer will reboot automatically.

Change Default Passwords!

Two users are installed by default, these are "arcom" and "root". Both have the password "arcom". For security, you should change these to the COAST standard passwords and users before connecting to the network! So:

Login as root
Type rw, this makes the root partition writeable.
Change the root password with passwd.
type adduser coast and give the COAST user password.
cd /home/arcom
cp .bashrc /home/coast
cp .inputrc /home/coast
cp .inputrc /home/coast
cp .profile /home/coast
cd
deluser arcom
rm -rf /home/arcom
type poweroff to power down gracefully.

You can now install the computer in a COAST telescope and continue the installation from your office. There are three connectors: USB, ethernet, and power. All the telescopes are wired up the same way so you can use another one as an example.

SSH Sshenanigans

You have put a new computer on the network with the same name and IP as an old one. But ssh knows the difference, because they will have different cipher keys. If your host has accessed the finder before and you try to connect to it with ssh you will get a complaint about a possible "man in the middle attack" and a refusal to connect. So on your host and on every host likely to have ever accessed that finder:

Login as coast.
cd .ssh
vi known_hosts

Look for a line starting with the hostname of your new finder computer.
Delete that line.
Save the file and quit vi.

ssh coast@apfinderwhatever
After a warning about authenticity you will be able to log in.
Note: You cannot telnet in remotely as root. This is for security. To get root access with telnet, you must log in as coast and then use su. However, you can ssh in as root. There is no good reason to use telnet with the finders, it is only there as a backup if ssh fails.

Set the Coast User ID

The coast user should have the same ID as they do on the other computers in the network, mainly to avoid confusion during NFS file sharing:

Log in as coast and become root.
Type rw to make the root partition writeable.
vi /etc/passwd
Edit the coast line to become "coast:x:103:103:COAST Admin Account,,,:/home/coast:/bin/sh".
cd /home/coast
chown coast .*
chown root ..
Logout and check that you can still login as coast.

More SSH Sshenanigans

The coast user needs to be able to run the finder executable from selected computers without a password (otherwise launching finder with pulldown menus on a remote host won't work). This requires a program called xauth to be present, not part of the Arcom distribution. Also, X11 forwarding needs to be turned on in ssh so that finder can be displayed remotely. This is done by sshd, but the version supplied by Arcom is crippled in this respect. The easiest way to fix this is to copy these programs from a finder with versions that work (I have compiled replacements):

Log in as coast, become root and make the root partition writeable.
Edit /etc/hosts . The finder hostname and IP will already be there, just add similar content as for other finders.
Edit /etc/ssh/shosts.equiv to have the same contents as for the other finders.
Edit sshd_config:

Set HostbasedAuthentication to yes
Set IgnoreUserKnownHosts to yes
Set X11Forwarding to yes

Look up the IP of a working finder here, for example 172.24.225.211 (the finders don't have hostname lookup even though a DNS IP address is requested during installation).
Carry out the modifications to ssh:

scp 172.24.225.211:/etc/ssh/ssh_known_hosts .
cd /usr/X11R6-e/bin
scp 172.24.225.211:/usr/X11R6-e/bin/xauth .
cd /usr/sbin
scp 172.24.225.211:/usr/sbin/sshd sshd.new
mv sshd.new sshd
reboot

Wait about half a minute and then see if you can login as coast without a password from one of the COAST machines. Then test X11 forwarding: type xterm and see if an xterm appears. If you get an X11 error it might be that you needed the "-X" option to ssh when logging in (shouldn't be necessary on any of the bunker machines).

Mounting Oberon as an NFS (Network File System) Drive

The finder program and CCD drivers are stored in directories on oberon which are NFS mounted by the finders. Hence when the program or drivers get updated it is only necessary to update one set of files on oberon rather than one set on each of the finders. Hence all the finders are guaranteed to be running the same version of the program! When finder produces data (when saving images or movies), the data is also stored on oberon as the local storage capacity is limited.

So set up NFS directories:

Log in as coast, become root and make the root partition writeable.
Make two directories:

/net/oberon/soft where the software is kept
/net/oberon/data where finder data is stored.

Add the following two lines to /etc/fstab :

oberon.ra.phy.cam.ac.uk:/soft /net/oberon/soft nfs ro,hard,intr,nolock 0 0
oberon.ra.phy.cam.ac.uk:/data2 /net/oberon/data nfs rw,hard,intr,nolock 0 0

Check it works:

/etc/init.d/mountnfs.sh
ls -l /net/oberon/soft/finder (you should see finder, ccd.o and sx_usb.o).

Add NFS mounting to the normal boot scripts (rc3):

cd /etc/rc3.d
ln -s ../init.d/mountnfs.sh S98mountnfs

Check that worked:

reboot

This works pretty well, except we had to use the "nolock" option in /etc/fstab. This means that more than one program can write to a file at a time (definitely not a good idea) because the finder has no idea whether another program is trying to access the file or not. This can be fixed if we also install a daemon called portmap. This is not part of the standard arcom distribution so copy the files from another finder (apfinder1, 172.24.225.211, for example):

Log in as coast, become root and make the root partition writeable.
Copy over the portmap daemon:

scp 172.24.225.211:/sbin/portmap /sbin

Create a new group and user called "rpc" for the daemon:

adduser -g "Portmapper RPC user" -s /bin/false rpc
You will be prompted for a password. Choose anything you like, I used the coast password. Adduser does have a "no password" option but it doesn't work for me.

Clean up after adduser, it isn't very bright and doesn't do quite what we want:

In /etc/passwd, edit the rpc line to read rpc:x:32:32:Portmapper RPC user:/:/bin/false
In /etc/group, edit the rpc line to read rpc:x:32:
Delete the /home/rpc directory that was created as a side effect.

Delete the "nolock" options in /etc/fstab so that the nfs lines read

oberon.ra.phy.cam.ac.uk:/soft /net/oberon/soft nfs ro,hard,intr 0 0
oberon.ra.phy.cam.ac.uk:/data2 /net/oberon/data nfs rw,hard,intr 0 0

Check it worked:

reboot
login and type ps
You should see that portmap and lockd are running.
You should be able to see directories on oberon if you look in /net/oberon/soft or /net/oberon/data.

The CCD Drivers

It is now necessary to install USB drivers (Arcom neglected to provide them but I have compiled some) and CCD drivers. The CCD drivers don't really get installed, we just put in a symbolic link to the drivers on oberon. The USB drivers can most easily be copied from another finder.

Log in as coast, become root and make the root partition writeable.
Lookup the IP of a working finder here, for example 172.24.225.211 (the finders don't have hostname lookup).
cd /lib/modules/2.4.18/kernel/drivers/
mkdir usb
mkdir ccd
Copy the USB drivers over:

cd usb
scp 172.24.225.211:/lib/modules/2.4.18/kernel/drivers/usb/hub.o .
scp 172.24.225.211:/lib/modules/2.4.18/kernel/drivers/usb/usb-debug.o .
scp 172.24.225.211:/lib/modules/2.4.18/kernel/drivers/usb/usb-ohci.o .
scp 172.24.225.211:/lib/modules/2.4.18/kernel/drivers/usb/usb.o .
scp 172.24.225.211:/lib/modules/2.4.18/kernel/drivers/usb/usbcore.o .
chmod g+w *.o

Now for the CCD drivers:

cd ../ccd
ln -s /net/oberon/soft/finder/ccd.o ccd.o
ln -s /net/oberon/soft/finder/sx_usb.o sx_usb.o

Now make the modules load at boot time:

cd /etc/init.d
Create a file called initccd.sh containing the following:

#! /bin/sh insmod usbcore insmod usb-ohci insmod /net/oberon/soft/finder/ccd.o # Use "model=5" for the Starlight Xpress MX516 # Use "model=-5" for the HX516. insmod /net/oberon/soft/finder/sx_usb.o model=-5

chmod ugo+x initccd.sh
cd /etc/rc3.d
ln -s ../init.d/initccd.sh S99initccd

...so the CCD modules won't load until after NFS mounting is complete and the modules can be seen from the finder.
Finally, we have to make some devices for the CCD drivers to work with:

Type (by cutting and pasting) the following:

mknod /dev/ccda c 127 0 mknod /dev/ccda1 c 127 16 mknod /dev/ccda2 c 127 32 mknod /dev/ccdA c 127 128 mknod /dev/ccdA1 c 127 144 mknod /dev/ccdA2 c 127 160 mknod /dev/ccdb c 127 1 mknod /dev/ccdb1 c 127 17 mknod /dev/ccdb2 c 127 33 mknod /dev/ccdB c 127 129 mknod /dev/ccdB1 c 127 145 mknod /dev/ccdB2 c 127 161 chmod 0666 /dev/ccda chmod 0666 /dev/ccda1 chmod 0666 /dev/ccda2 chmod 0666 /dev/ccdA chmod 0666 /dev/ccdA1 chmod 0666 /dev/ccdA2 chmod 0666 /dev/ccdb chmod 0666 /dev/ccdb1 chmod 0666 /dev/ccdb2 chmod 0666 /dev/ccdB chmod 0666 /dev/ccdB1 chmod 0666 /dev/ccdB2

The Finder Application

Finally, we need to install finder itself, or rather, a symbolic link to finder on oberon:

cd /bin
ln -s /net/oberon/soft/finder/finder finder

We also need to install a configuration file so that the local incarnation of finder gets telescope-specific information:

Stop being root by typing exit. You should now be coast.
cd
create a file called finder.conf that looks like this:

# Finder configuration file # # NOTE: This file is automatically generated! Changes # made to parameters will be remembered, but comments # will be overwritten! # Name East_Telescope TelescopeIP apcsttel.phy.private.cam.ac.uk Port 2703 Crosshair 345 197

Change the name and port to the values for your telescope as described here. More information on the file format can be found here.

Check it All Works!

Reboot the finder and log in as coast. Use the "-C" option for ssh if you are working from the Cavendish Labs, this speeds up the link by compressing the X11 traffic.
type dmesg . If all is well, at the end of the listing you should see something like this:

Registered ccd @ major #127
usb.c: registered new driver starlight-xpress
hub.c: USB new device connect on bus1/2, assigned device number 2
starlight-xpress: probing usb_device 0x0547:0x2131
starlight-xpress: found EZUSB device
starlight-xpress: RESET 8051
starlight-xpress: Download 341 code records
starlight-xpress: un-RESET 8051
usb.c: USB disconnect on device 2
starlight-xpress: disconnect
hub.c: USB new device connect on bus1/2, assigned device number 3
starlight-xpress: probing usb_device 0x4444:0x4220
starlight-xpress: found ECHO2 device
starlight-xpress: read 0xFF model from camera
starlight-xpress: writing 0x05 model to camera
starlight-xpress: camera model is Starlight Xpress HX5/16
Registered CCD mini-driver: Starlight Xpress HX5/16 @ minor #0 and #128
starlight-xpress: camera has 1 serial ports

Type finder and watch the user interface appear. Hit the "connect to CCD" button. If you see a crosshair appear, you're in business!

Time Synchronisation (optional)

The clocks on the finder computers can be synchronised using the Network Time Protocol (NTP). For the finders installed in the COAST telescopes this is desirable so that results can be compared with fringe data and autoguider data taken simultaneously. A network connection is required so it is not possible to use NTP on a stand-alone DIMMWIT box in a remote location.

As with much of the previous installation, it is easiest to copy the required files from an existing finder. Suppose we want to install onto apfinder1 (172.24.225.211) using apfinder5:

cd /usr/sbin/ scp ntp* 172.24.225.211:/usr/sbin scp tickadj 172.24.225.211:/usr/sbin cd /etc scp -r ntp 172.24.225.211:/etc scp ntp.conf 172.24.225.211:/etccd /etc/init.d scp ntpd 172.24.225.211:/etc/init.d cd /lib scp libcap.so.1.10 172.24.225.211:/lib

On apfinder1:

cd /lib ln -s libcap.so.1.10 libcap.so ln -s libcap.so.1.10 libcap.so.1

Add the following lines to /etc/hosts on apfinder1:

# Time servers... 131.111.8.74 aquila ntp0.cam.ac.uk 131.111.12.21 janus ntp1.cam.ac.uk 131.111.8.42 chimaera ntp3.cam.ac.uk 131.111.48.8 mraos mraos.ra.phy.cam.ac.uk

Check it works on apfinder1:

/etc/init.d/ntpd start /usr/sbin/ntpq -p

...should return something like...

remote refid st t when poll reach delay offset jitter ============================================================================== +aquila ntp2.ja.net 2 u 5 256 377 1.177 1.020 0.295 -janus spanner.eng.cam 3 u - 256 377 1.897 -0.166 0.057 *chimaera ntp2.ja.net 2 u 251 256 377 1.136 1.007 0.086 -aptitania spanner.eng.cam 3 u 252 256 377 0.431 -0.090 0.161 +apcstapd spanner.eng.cam 3 u 45 256 377 0.390 0.672 0.048

Ideally we would just leave NTP running all the time, but it periodically interacts with its servers over the network. If this happens while a DIMM file is being recorded, dropouts in the acquisition can occur. We could use the cron program to switch on NTP only during daylight hours, but cron itself wakes up once a minute to see if there are any tasks that need doing. Again, there is a risk of dropouts. So instead we tell oberon to start and stop NTP on the finders during the day and let the finder clock run by itself during the night. This way, there are no unnecessary processes running during observing hours.

To do this, we need to give coast on oberon the power to run the /etc/init.d/ntpd script on the finder, which normally requires root privileges. To do this without compromising security too much we install the super program on the finder.

On apfinder5:

cd /bin scp super 172.24.225.211:/bin cd /etc scp super.tab 172.24.225.211:/etc

On apfinder1, check it works by logging in as coast and typing:

super ntpd stop super ntpd start

...you should see the ntpd daemon either appear or not when you type ps.

Finally, oberon needs to know when to start and stop ntpd on the finder. If you are replacing a finder it probably already knows but it doesn't hurt to check.

crontab -e

Add lines to the file something like:

01 9 * * * ssh apfinder1 super ntpd start > /dev/null 51 14 * * * ssh apfinder1 super ntpd stop > /dev/null

The first and second columns are the minute and hour of the day respectively that you want NTP to start and stop. I prefer to start or stop NTP on each finder a minute apart so that the load is spread out.

Building Finder

There are two parts to finder, the main application that the user sees and the driver modules for the CCD.

The Application

Compilation should be straightforward on a linux system provided you plan to dynamically link the application to run-time libraries. Compilation has been tested under RedHat 7.2 and 8.0, and Debian Testing (Sarge). The libraries required are:

Xfree86
Qt 2.0 or higher

However, the single board computers only have a minimal Redhat installation. In particular, Qt is not present. Hence it is necessary to link static libraries at compile time to produce an executable. The libraries required are:

libXft.a
libqt.a
libmng.a

Up to RedHat 7.3, RPMs of these libraries were available. From 8.0, however, RedHat no longer made them (except for libmng), nor did Debian. It has hence become necessary to download and install the static libraries manually. Most troublesome is libqt, you might have to download the right distribution and compile it just to get the libqt.a file.

The Drivers

The drivers are a set of two modules, ccd.o and sx_usb.o that need to be dynamically loaded by the kernel before the Starlight Xpress CCD camera can be accessed via the USB cable. In order to compile them you will need a source tree for the target kernel. For the single board computers the source tree is on our copy of the Arcom development kit CD ROM.

Running Finder as a Transportable DIMM

Introduction

As part of its legacy finder includes code that allows it to be used as a fast readout "Differential Image Motion Monitor Which Is Transportable" (DIMMWIT).
In this mode, a single board computer running finder is directly connected to a host PC via ethernet.
There is no network. Hence this configuration is useful in remote locations.
COAST has two finder computers configured for use in this way, each in a blue box.
The finder program is stored internally but an updated version on the host PC can also be used.

Setting up your host PC

The stand alone finder is called "dimmwit" and has an IP address of 192.168.20.1 .
It expects your host computer to be called "dimmwithost" with an IP address of 192.168.20.2 .
These are IP addresses allocated to private networks.

You can change your computer's settings accordingly, or you can instead create a virtual ethernet device which will not affect your usual network connectivity:

A useful guide is at http://handsonhowto.com/virt.html .
If you have a recent redhat installation, create a file called /etc/sysconfig/network-scripts/ifcfg-eth0:1 containing the following:

Password:
DEVICE=eth0:1
BOOTPROTO=static
BROADCAST=192.168.20.255
IPADDR=192.168.20.2
NETMASK=255.255.255.0
NETWORK=192.168.20.0
ONBOOT=yes

Put the following in /etc/hosts :

# DIMMWIT single board computer192.168.20.1 dimmwit# This machine when talking to DIMMWIT192.168.20.2 dimmwithost

When connected to dimmwit your computer will now use the 192.168.20. subnet and be called "dimmwithost" but when connected to your usual network it will have its usual name and IP.

It is also a good idea to set up NFS on your PC so that dimmwit can save files direct to your hard disc (the onboard space is limited):

Put the following in /etc/exports :

# Starlight Xpress single board computer
/directory/that/contains/program 192.168.20.1(ro)
/directory/that/contains/data 192.168.20.1(rw)

The directories are of your choosing and are the places you want to keep any updated finder executables and generated data. So make sure they exist and that the data directory is writeable by anyone.
Also make sure that 192.168.20.1 is allowed to do NFS in /etc/hosts.allow .
Make sure an NFS server is running on your PC! On a redhat system you can run serviceconf to start it.
You will need to edit /etc/fstab on dimmwit to reflect the directories you have chosen. This can be done from your PC host once you have connected, or you can connect a keyboard and monitor to dimmwit and do it directly.

Connections:

Connect the 30m ethernet cable between dimmwit and your PC.
Boot your PC.
Turn on dimmwit and wait half a minute or so for it to boot.
Connect the USB camera controller to dimmwit with the USB cable.
Connect the camera head and power supply and turn them on.

Running finder:

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

ssh coast@dimmwit finder

Enter the password when requested (NOTE: 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.
For information on using finder, refer to the user guide and in particular the section on DIMM mode .
To use the version on your host PC instead, type

ssh coast@dimmwit remotefinder

Shutting down:

Do "disconnect CCD" from within finder.
Exit finder.
(optional but preferred) From your xterm, type "ssh root@dimmwit poweroff" and enter the root password when requested.
The order in which things are then turned off or disconnected is not important.

Actions which have been found to crash finder or the controller (don't do them!):

Quit finder while in fast or slow readout mode.
Choose the region selection tool (the green rectangle) and then double click on the image area.

Actions which will reduce the scientific value of the data:

Long acquisitions in fast readout mode will experience dropouts if the mouse is moved or windows/menus are selected.

Converting a HX516 to run in 1D DIMM mode [deprecated]

NOTE: This section is retained for archival purposes. The cause of the problem has finally been discovered: the horizontal clocking for the HX516 is the inverse of that for the MX516. The drivers have been modified to support the HX516 clocking and the artefacts have gone away.

- Bodie Seneta 19 October 2004

We have two kinds of Starlight Xpress camera head in the COAST group, the MX516 and the HX516. The MX516 works in 1D DIMM mode without modification, but the HX516 is much more problematic. Often the result of a HX516 1D DIMM measurement is a series of vertical lines within which the original data is lost.

DIMM artefacts.

Unfortunately for DIMM purposes, the HX516 is the camera installed in the COAST telescopes. However, we have a single HX516 which functions correctly in 1D DIMM mode as is, currently installed in the east telescope. Furthermore, Terry Platt at Starlight Xpress has suggested a hardware modification for the HX516 that sometimes mitigates the problem. The solution is to reduce the value of the black level clamping capacitor in the camera head from 10nf to 1nf. We are in the process of converting other COAST cameras over. There is a supply of surface mount 1nf capacitors in the kit of spares at COAST. The modification is described below by Terry:

Another workaround is to use 2D DIMM mode instead, which always works.

Appendices

The Finder Configuration File

Each Finder computer runs an identical copy of the Finder program (the original is currently stored on Oberon). However, there are things each Finder needs to know which are unique to the telescope it is in, which may need to be changed without recompiling the source code or which must be remembered even during power cycling. These are stored in a local file (the default name is finder.conf but others can be loaded or saved via the File menu). The file is loaded at runtime and saved upon quitting or user request. It is also text-editable, although no comments or formatting will be preserved the next time Finder writes it.

Example of finder.conf (it may change):

# Finder configuration file## NOTE: This file is automatically generated! Changes# made to parameters will be remembered, but comments# will be overwritten!#Name East_TelescopeTelescopeIP apcsttel.phy.private.cam.ac.ukPort 2700Crosshair 160 89
# as the first character in a line denotes a comment. The rest of the line is ignored.

Name is the name to appear on the particular Finder window title bar and all ancilliary dialog boxes, to avoid confusion when several Finders are displayed on the same monitor.

TelescopeIP is the name or IP address of the telescope controller computer.

Port is the ethernet port number used to communicate with the telescope controller.

Crosshair is the X and Y coordinates of the current crosshair position (the target point which finder and the telescope will try to move the star image towards such that it also lands on the autoguider).

Enumeration Reference

For "historical reasons", the telescope nomenclature associated with Finder can be confusing. However, the following table, correct at the time of writing, might assist in resolving ambiguities:

Telescope number	Finder computer name	IP address	Foundation	Beam	Finder-telescope ethernet port
1	apfinder1	172.24.225.211	N4	4	2704
2	apfinder2	172.24.225.212	C	1	2700
3	apfinder3	172.24.225.213	E1	3	2703
4	apfinder4	172.24.225.214	W7	2(W)	2702
5	apfinder5	172.24.225.215	W2	2(E)	2701
(spare)	apfinderx	172.24.225.216	(spare)	(spare)	(spare)
reserved IP	apdimm	172.24.225.217	none	none	not connected

apfinderx is a spare single board computer configured as a replacement for failed boards in telescopes. apdimm is an IP address allocated in case we should wish to connect a DIMMWIT to the COAST network.

This page last updated 20th October 2004 by bodie@mrao.cam.ac.uk