APT 2.0

Simon Dawes & Keith RickardUpdate 1

What is the APT?Automatic Photometric Telescope

Built by Jack Ells in 1984 (based on JBAA)

AutomaticOnce set-up it continues to observe the same stars over and over, corrects for tracking problems, recognises cloud.

PhotometricUses a photomultiplier tube and 24 bit counter (256^3 – 3 x 8 bit counters) to measure star brightness

TelescopeDuh…

Why 2.0The APT has been out of commission for about 5 years• The fluid light guide went opaque - a generous gift from the

BAA enabled us to buy a new one.• The BBC Model B used to control the telescope stopped

working - it was a rare 64kB version and the National Museum of Computing generously swapped it for a working model they had.

• The drives failed, the 20 year old soldering failed and was rewired by an ESA engineer

• The BBC Model B software keeps crashing• Moving Data off of the APT (if it was working) requires

manual transcription

2.0 Approach

Concepts• Computing Platform Agnostic• Interface platform well established and

supported• Simple User Interface• Simple to use• Smaller footprint

2.0 Approach

Why keep the PMT and not use a CCD camera?• A more complex solution is required (e.g. laptop

and imaging software)• Additional cost• PMT provides instant results - a CCD requires

post-processing time and effort• PMT can be accruate to a few 1000ths of a

magnitude

Main Components of the APT

• 8 1/2 inch Newtonian reflector• Flip mirror• Light Guide• Photomultiplier Tube (PMT)• Filter wheel• Amplifier/Discriminatior• PMT pulse Counter• Stepper motors and control box• Computer system

Currently...

Flip mirrorFlip mirror

Reticle eyepiece

Light guide socket

A pin hole allows light of the star to pass through to the PMT. The field of view is 1 arc minute.

Mission ControlMonitor

BBC Micro B computer (64K RAM)

Two 5 1/4" floppy disk drives

PMT pulse counters

Stepper motor control box

900v DC power supply

PMT amplifier and discriminator box

Photomultiplier tube (PMT)

Stepper motor box

Inside the control boxResistor heat sink

2 x Stepper motor control boards

Sockets for stepper motor leads

240V AC to 30V DC transformer

BBC Micro B cable connector socket

note: wiring rebuilt by Mark

Photomultiplier tube900V power supply

Photomultiplier tube (PMT) enclosure

Amplifier and discriminator box

Filter wheel

Light guide hole

Amplifier and DiscriminatorConnector for PMT

cable

+12v/-12v power socket

Connector to PMT Pulse Counter box

PMT Pulse CounterAmplifier/Discriminator cable connector

BBC interfacing chip

Counters (count up to 16,777,216 pulses)

Cable to BBC Micro B interface port

5 volt supply from BBC Micro B computer

Introducing the Raspberry Pi and the Arduino Uno

Raspberry Pi• 256MB RAM (BBC has 64K!)• 600 Mhz (BBC runs at 2Mhz!)• Runs under Linux (like Windows but free and open source)• Operating system runs from an SD Card instead of a hard disk• 2 x USB ports (for mouse, keyboard and other devices!)• GPIO port• Runs off 5V at 700ma• Costs around £33

Also has

• Ethernet port for connection to a network

• HDMI & composite video output

• Audio output

Arduino Uno

• 32K Flash memory• 2K RAM• Runs at 16mhz• 20 input and output pins which can be used to directly

control electronic devices• USB port which is presented to connecting device as a serial

port• Runs off 5 - 12V, max 1000ma• Costs around £15

2.0 Architecture

RPi(Master)

RA Drive

DEC Drive

PMT

Controller

counter

Arduino(Slave)

Arduino(Slave)

Keypad

LCD

Buzzer

• The programming language for the Arduinos is C++

• Raspberry Pi will be the "brains" of the operation and will control the two Arduinos by instructing them what to do, operate the user interface, store data from the PMT, etc. The program is being written in Python.

The RPi and Arduinos will be powered by a USB hub

Connecting to the stepper motor control boards

The Arduino will be housed in the stepper boards box and connected to this board

Connecting to the PMT pulse counters

This is the only bit that is required.

These counter chips will be placed on a small circuit board known as a "shield" on the Arduino and housed in the stepper boards box

Hand Box

Will contain a red lit 2x16 character LCD

Will aim to have the keypad backlit in red

Software

~15% complete; 1235 lines of code-No user interface (no keyboard, mouse or monitor!)

- Controlled by pre-built files and user input/output via a hand controller

-Arduino's controlled by bespoke 'language' invented by Keith and Simon, currently 31 commands.

Spiral Search

We are keeping many concepts in the original software such as the spiral search. This will be managed by the Python software

Find Sky* = Done

Find CheckHA 18.8:DEC 73.1

Find ComparisonHA 18.8:DEC 73.1

1. APT 2.0 MenuPress *

Select VariablePress *,2,4 or #

Select ObserverPress *,2,4 or #

CommissionPress *,2,4 or #

AboutPress *,2,4 or #

Z CamPress *,2,4 or #

cycle through objects in objectlist.csv

Find VariableHA 18.8:DEC 73.1

# #

6 6 6

4 4 4

#*

*

#*

During this sequence:1)The arrow keys are available to slew the scope. 2)The A,B,C keys change the slew speed3)* moves on in the sequence4) # exits the sequence back to 'Select Variable'

Current Menu Structure

End