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Reporting Lunar Occultations

Reporting Lunar Occultations

The most significant change for 27 years in reporting
lunar occultations is now underway

Dave Herald

Canberra, 29th of August 2008


1 Introduction

Central collection of lunar occultation observations commenced in the 1930's, with it becoming the responsibility of the Royal Greenwich Observatory within about 2 years. That responsibility was transferred to the Japanese Hydrographic Department in 1981. It is now transferring to IOTA. IOTA will commence collecting observations for Africa, Australasia, and North and South America, as from 1 September. Commencement for Japan and Europe will occur in the near future.

There are a number of very important issues associated with this change.

I urge everyone who makes lunar occultation observations to read all these messages in detail. I know this can be tedious, but this is the biggest change in the reporting arrangements for 27 years.

Also, if you know of people that make lunar occultation observations, but are not subscribers of the various email groups, please forward these emails on to them.

If you have queries about the new process, please raise them on the groups. Chances are that someone else will have a similar query.

I am confident that the new arrangements will work very well. But equally I have no doubt that some unexpected issues will arise somewhere - I wish I could predict where! I just ask for everyone's patience and tolerance in those situations.

Finally, at this significant time I think it is appropriate that we thank ILOC for the valuable service they have provided us for the last 27 years.

2 Occult - new version available - version 4.0.5

2.1 A new version of Occult is now available. Version 4.0.5.

For those already using Occult4, the basic upgrade involves a 1.8MB download. The download to update Occult is available at .

When you first run the new version, you will be taken to a download page where you can update a range of files (as described on the above page).

[For those that only read instructions when something doesn't work, the direct download of the update is at]

2.2 Main changes in Occult 4.0.5

The main changes in this version of Occult are associated with supporting the processing and archiving of lunar occultation observations. The Japanese Hydrographic Department (ILOC) has been the agency responsible for collecting lunar occultation observations since 19981. Unfortunately they are unable to continue with that role, and the International Occultation Timing Association (IOTA) has agreed to take on the responsibility.

As part of this responsibility:

Additionally there have been a range of updates and improvements, with the following being the more noteworthy:

This is an important update to Occult. I urge all users of Occult to update to this new version.

3 Lunar Occultations - new report format

As mentioned in other emails, the responsibility for collecting lunar occultation occultations is moving from ILOC to IOTA. When ILOC took over the responsibility for Lunar Occultations in 1981, the report form was extensively revised from that used by Royal Greenwich Observatory - but has not been significantly revised since then. In recent years Video has become a common observing tool, and GPS has become common both for coordinate measurement and time base. Neither of these developments were well supported in the ILOC report format.

Additionally, several years ago ILOC concluded that their system of allocating Station and Observer codes was breaking down. As a result, they completely changed the format of their internal file of reported observations - with the site details being included against every observation in the file.

The transfer of responsibility to IOTA has provided an ideal opportunity to revise the report format. This was approached with the following principles:

3.1 Detailed summary of the changes that have been made

3.1.1 Site coordinates.

3.1.2 Observer details

The email address of each observer may be included (but will not be archived). This will allow a graze coordinator to send preliminary reductions or queries to individual observers, and for a regional coordinator to send the reductions to all observers individually.

3.1.3 Event codes

3.1.4 Method of observing codes

Codes added for:

3.1.5 Time Source (previously called Method of Timing)

Codes added for:

3.1.6 Remarkable circumstances

Code added for event observed during daylight (sun higher than -6 deg).

3.1.7 Double stars

A new field added to allow the WDS component identifier to be specified. [Neither RGO or ILOC ever corrected double star observations to refer to the relevant component. For example, observations of Antares B are returned with residuals of about -2". This new field allows proper reduction of double star components.]

3.1.8 Gradual events

If an event was gradual, the ILOC report had the duration in the comments. In the new format this is a data item in itself. There is also a data item to indicate whether the reported time is at the 50% light level (appropriate for large stars) or at the 25% level (appropriate if Fresnel diffraction was involved.)


Like the ILOC format, the new format allows observers to provide comments against each observations. However those comments will not be archived with the observations. Their only value is in assisting the proper reduction of an observation. [NOTE the ILOC data set does not contain any of the comments that people may have reported in the past. For those who think that comments should be retained - think about the issues associated with unconstrained free text being entered by unrelated people in multiple languages and character sets....]

3.1.10 Header information

The new reporting arrangements will be entirely by email. The days of observers submitting observations on a handwritten form are over. (ILOC advises that they rarely receive hand-written reports.) Consequently the field for the postal address of the representative has been removed. Similarly the field for indicating where the observations have been reported has been removed.

However a new field has been added for free-text comments about the report as a whole. This enables you to provide comments that will assist the coordinator in dealing with your report. By being included as part of the report, the comments will be available when the report is being processed. [In contrast, comments in the email body may get separated from the report when it is being processed.]

3.2 Transitional issues

  1. With the new reporting arrangements, we have maintained the capability to read occultation reports written in the ILOC format. However we urge all observes to move to the new report format in the very near future.
  2. If you have unreported observations, please report them to IOTA under the new arrangements (using either the ILOC format, or the new format - Occult, LunarReport, and LOW can read a report in the ILOC format and write it in the new format). This will help make the transition from ILOC to IOTA occur in the shortest possible time. [Observers in Europe or Japan should hold on to their unreported observations until they are advised of the reporting arrangements for those regions.]

4 Lunar Occultations - the new reporting process

As most will be aware, the Japanese Hydrographic Department (ILOC) announced earlier this year that they would be unable to continue in their role of collecting lunar occultation observations. IOTA has agreed to take on this responsibility.

A number of people have been working hard with developing an updated reporting format, and software solutions to support the reporting of observations, and the analysis of observations. We have now reached the stage where IOTA will be commencing to collect Lunar Occultation Observations for the Americas, Australasia, and Africa as from 1 September 2008. There will be separate announcements for Europe and Japan in the near future.

4.1 Collection strategy.

The Centre de Donnees astronomiques de Strasbourg, which handles the archiving of data in the Astronomical Date Centres of VizieR, has agreed to archive lunar occultation observations. This is significant for several reasons. Firstly, the observations will (for the first time) be archived in 'proper' data archives so that we can be confident that the data is secure in the long-term. Secondly, it is archived with 'main stream' astronomical data. Thirdly, the data will be readily available for anyone to conduct research using it.

The data collection process may simply be described as the process of getting the observations from the observer into the archive. [Of course, we will be making use of the data before it is archived - but that is secondary to the process of archiving.] In setting up the process, there were two key objectives:

  1. The process must not be critically dependant upon a particular piece of software; and
  2. The process must not be critically dependant upon any one individual.
The process that has evolved is based on the model used for collecting asteroid occultation observations. That is, someone in a region has responsibility for collecting observations in that region, with those observations being subsequently collected by a more central person for final processing into the archive. In this model, the regional collectors are in a position to assume the role of the central person relatively easily. Similarly, the regional collectors can provide support for new regional collectors.

On the software side, there are 4 separate applications, from 3 different authors, to support the new report format.

4.2 Detailed arrangements

As of 1 September, regional coordinators (collectors of observations) have been identified for North America, Australasia and Japan. Additionally the North American coordinator has agreed to collect the observations from South America; and the Australian collector has agreed to collect the observations from Africa. [However, if the volumes from those two regions become significant, we would be looking for coordinators in those regions...!]

The regional coordinators will do the initial processing of the observations, including sending a preliminary reduction to the observer. Additionally, they will be converting the observations into the format used to archive the observations. Periodically, they will forward the observations to a global coordinator who will merge all the observations into a single file - with that file being periodically archived. More details about this arrangement may be found at

lunarreport.htm and


4.3 Implementation

  1. In other messages I have referred to the various software packages that support the new reporting process. Relevant email addresses for reporting observations are included in those packages (with facilities to readily get the 'latest' addresses. Observers should obtain their software solution of choice, and start using it.
  2. As from 1 Sept 2008 (0hrs UT for the pedantic!) the coordinators for Nth & Sthn America, Australia, New Zealand and Africa will start collecting observations. Observers in those regions can start sending observations to them from that date. If you have observations ready to be reported, DO NOT SEND THEM TO ILOC. Send them to your regional coordinator. [This will make the transition easier and faster.]
  3. FOR ALL OBSERVERS - WHEREVER YOU ARE LOCATED. Graze observations should now be sent to the graze coordinator - MITSURU SOMA.
  4. Observers in Japan and Europe. Please hold on to any unreported 'ordinary' occultation observations until you are advised that your local coordinator is ready to receive them.

5 Lunar Occultation reporting software

The new arrangements for reporting lunar occultation observations are being supported by 4 software solutions for creating the report. Those solutions are (in alphabetical order):

5.1 Excel-based report form.

Created by John Talbot (New Zealand) and Brad Timerson (USA), this uses an Excel Worksheets for Observer Information, Telescope Information, and Observations. The Form makes extensive use of drop-down lists with common terminology. The resulting Excel file is emailed to the regional coordinator, who uses an Excel macro to convert the spreadsheet data into the final report format for reduction and archiving using Occult or LOW. Download from . The download is about 30K.

5.2 LOW {Lunar Occultation Workbench)

This is a comprehensive lunar occultation prediction and reduction package written by Eric Limburg (of the Dutch Occultation Association). Like Occult, LOW offers a complete reduction of an observation, so that any data entry errors can be immediately identified. Eric has not quite finished updating the program to use the new format - but a beta version should be available in the near future. The LOW download page is at: .The download is about 88MB.

5.3 LunarReport

This program is effectively the Lunar Observations editor from Occult, packaged as a stand-alone application. It contains extensive data entry checks. However it does not include a star catalogue or a lunar ephemeris - so (like the Excel report) it cannot perform a reduction of the observations. It can be downloaded from . The download is only 194K.

5.4 Occult

This is the full-featured Occult program, which deals with Lunar occultation predictions and reductions, Asteroid occultation predictions and reductions, eclipses and transits (plus more....) It can be downloaded from either as an update to an existing version of Occult 4 (1.8MB download) or the complete package (28MB) There are optional downloads of up to another 130MB.....

6 Three items to be added

6.1 Grazing occultations

The members of a graze expedition should continue to report their results to the person who organised the graze (as has been done for the last 40 years). That person will then send the combined observations to Mitsuru Soma. Individual observers should not send their observations direct to Mitsuru.

6.2 Reporting frequency

At this stage we are working on the basis of observers reporting their observations on a monthly basis, and aim to have a monthly update to the publicly available file of current observations. But if you make a lot of observations over a couple of nights, you can send your report at that time. Graze reports should be sent to Mitsuru as soon as all observations have been collected.

6.3 Please do not send your report to more than one person

The process for archiving the observations involves merging the reports gathered by the different coordinators into a single file. If you report your observations to different coordinators, they will create duplicate observations in the merged file - and someone will have to go through and delete the duplicates. [That is a task that no-one wants to do!]

7 For Users of Occult in Europe

On September 4th from the European headquarter of IOTA-ES a new mailing address for reporting lunar occultations is provided, as can be seen in the following email sent by Hans-J. Bode.

Sent: Thursday, September 04, 2008 5:42 AM

Subject: AW: [PLANOCCULT] New Lunar Occultation reporting Process - some extra points

Dear All,

European observers should send their lunar occultation reports to which will distribute the data to those volunteers who will examine and reduce it. The big advantage: You will receive the residuals as soon as possible and the e-mail-address never changes.

Hans-J. Bode


This new reporting address has now been added to the list of reporting addresses that Occult (and the next version of LOW) access to obtain current reporting addresses.

To report observations from within Occult you need to have this new address included in Occult. There are two ways to do this:

1. From the Maintenance tab, select the download page. In the first grouping, select the last item 'Reporting addresses for Lunar occultations'

2. From the Lunar Observations editor, select the menu item 'Submit report... Download current Email reporting addresses'. From the form that appears, select either 'Source IOTA-US' or 'Source RASNZ', and click Download. Upon successful download, the European reporting address will be available in Occult.

When you are ready to report some observations, select 'Europe - IOTA-ES' from the list of reporting addresses (and you will see the actual email address when this is selected). [NOTE: You will not see any reference to Europe in the list of reporting addresses until you do the above download.]

Finally, do not try to send reports to the European address before Sept 8. [If you send a report before the address is active, Occult will 'appear' to validly send the observation report. However you can expect a 'Mail System error' from your ISP, reporting an invalid address.]

8 One month later ...

It has now been over a month since we started collecting lunar occultation observations. The number of reports submitted so far have not been many. However I have now placed all observations I've received from the coordinators onto the IOTA website where they can be downloaded from within Occult and used in current predictions and analysis. The download is under the Maintenance tab, Download button, and is in the top group of downloads ('Latest lunar observations')

In my opinion, this represents a significant advance from the past processes of reporting lunar occultations. Under the new process, observations are made public within a month or two of being reported - compared to the several years or more under all previous reporting arrangements. For the future, my intention is to update the file on the IOTA website whenever I receive new observations from the regional coordinators - so that the file is maintained as current as possible.

Do you want to view the contents of the new files after they have been downloaded? The files are located in the Occult 4\Resources Files directory, and are:

Finally - on the progress towards archiving the backfile of observations:

All this is going to take months to work through, but we should be able to deposit the first archive files in VizieR early next year...