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Note: More information about much of the software listed below is available in our Observing Occultations Using Video: A Beginner's Guide Manual.
Predict & Co-ordinate Observations:
OCCULT is a program which provides occultation observers with a comprehensive package to support their program of observing. Authored by David Herald, it allows you to:
Download OCCULT here.
Authored by Hristo Pavlov, Occult Watcher reads minor planet occultation predictions from Steve Preston's website and selects events for your local area. You can define a range of parameters to control the number of events diplayed. When a local event is found, you can register your own intentions and via the software check whether others plan to observe it, allowing you to co-ordinate with other observers to achieve maximum results. A great piece of software allowing us to co-ordinate team efforts.
Download Occult Watcher here.
Written by Hristo Pavlov, OccuRec is a video recorder for Windows that has been specifically created to provide better options for recording asteroidal occultations, particularly using integrating video cameras.
Download OccuRec here.
Written by Kazuhisa Miashita, Limovie is a video analysis tool specifically for use with occultation lightcurves. It is particularly good for general lunar occultations, and for lunar occultations of double stars.
Download Limovie here.
Download the Limovie Manual written by David Herald here.
Written by Hristo Pavlov, Tangra is a video analysis tool similar to Limovie. It is purpose-written for the analysis of occultation lightcurves.
The program reads AVI files and analyses the brightness of selected stars. It is more simple to use than Limovie for minor planet and Jovian mutual events, and it handles normalisation and binning integration.
Download Tangra here.
Written by John Broughton, ScanTracker allows you to plan your occultation observing using a CCD and the drift-scan method. Once you have obtained your data Scanalyzer helps you reduce it.
Download ScanTracker & Scanalyzer here.
A general purpose video capture & processing utility mainly for use with AVI files. Can be used to break AVI files into manageable chunks before processing with Limovie.
Download VirtualDub here.
General purpose script-based software for editing and processing videos.
Download AVISynth here.
Hristo Pavlov's BeeperSync software can be used to synchronise your occultation beeper box to UTC using only a Windows computer and the internet. The precision of this method is usually much better than 50ms and if you have a good internet connection and use an NTP server that is close to you - most of the time you will get a precision of about 5ms or less.
Download BeeperSync here.
General purpose audio recording and editing software, particularly useful for analysing voice recordings of occultations and extracting event times.
Download Audacity here.
A major problem when visual occultation timings are made is the amount of time it takes for an observer to react to the event. This time is called the observer's Personal Equation. When queried, many observers will estimate their reaction time as only a few tenths of a second, whereas comprehensive studies have shown that actual reaction times are often considerably longer - sometimes by an order of magnitude.
An observer's Personal Equation depends on many factors, some of which are:
as well as a number of other factors.
Human reaction time is the single largest cause of error in visual occultation timings, and its effects can have serious consequences, especially in the case of minor planet occultations where reaction times (differing between Disappearance and Reappearance) can be a substantial fraction of the occultation duration. When minor planet occultations are observed from multiple sites,large differences in the reaction times of the observers lead not only to uncertainty in the actual length of the chords, but also to large offsets between adjacent chords. It is for this reason that we encourage observers to move to non-eyeball forms of observing (e.g. video).
The International Lunar Occultation Centre (ILOC) has determined, thorugh the analysis of many tens of thousands of lunar occultation observations over many years, that the average reaction time for a lunar occultation disappearance timed by an experienced observer is of order 0.4 seconds. Experienced observers timing reappearances have an average reaction time of order 0.6 seconds. For less experienced observers studies have shown that reaction times are frequently many times these values.
Nevertheless, visual occultation timings still have value and will continue to do so. (It was, after all, the analysis of tens of thouands of visual occultation timings that showed that the Moon is slowly spiraling away from the Earth). With practice, human reaction times can be minimised.
Various computer programs have been written to help observers estimate - and with practice, reduce - their reaction times. The program available here - REACT - has been kindly made availale by John Talbot for free download.
REACT takes the form of an MS Excel spreadsheet containing macros written in VBA. (You must have Excel or Open Office installed to be able to run this, and you must allow the REACT macros to be run).
REACT simulates a realistic occultation, by producing a random star field on your screen with a target star whose brightness varies randomly on each run. If your speakers are turned on you will hear one-second pips that simulate the signals from time-signal station WWVH. The star will disappear at some random time and reappear some time later. You can make an "occultation" timing by hitting the ENTER key at each of these events. Your reaction times for both the disappearance and reappearance are measured over several runs, and the average value and standard deviation calculated. Note that while this program does simulate what happens in a real occultation, your reaction time at a true occultation event will also be affected by whether you're standing in the freezing cold, at 3 a.m. with a strong wind blowing....
If you think your reaction time is faster than 0.4 secs then check it out with this tool.
Download REACT.ZIP here