Use of Registax and LiMovie for the Reduction of Marginal

Occultations

Tony George

Umatilla, Oregon

Low light video cameras such as the Supercircuits PC164C

and Watec WAT 902H series cameras

allow observers to recordoccultations at the very limit of detectability

The problem comes when we try to reduce the data from these very low brightness events, sometimes the

target star is not visible on the video monitor and sometimes in LiMovie we cannot see the target star to affix an aperture to measure the brightness

To avoid this problem, some observers use integrating cameras such as:

• WAT 120N and Astrovid Stellacam

• Lumenera SKYnyx2-0

• SBIG STV

These are great cameras but there are a couple of problems

• At the maximum frame rate, they may not be as sensitive as the non-integrating cameras

• If you select an integration rate that is too long, you lose time resolution in your data

One solution to this problem is to use the non-integrating CCD video

camera and then integrate the video after recording. This allows you to extract just enough of the

signal to detect the event (or confirm a negative event), but no more than is necessary to avoid

unnecessary loss of time resolution

So how do you do this?

Registax to the rescue…

Videos can be easily and quickly integrated with Registax without any loss of video integrity and only the minimum required for time resolution

Integration can be done in four simple steps

We can take LiMovie data that looks like this….

Is there an occultation in this raw data?

And turn it into data that looks like this

This was done with an 11-frame integration from raw data

This was done with a 5-frame integration from raw data

We can extract data from videos where wind vibration is excessive…

If there is a bright star in the field, a pre-registration can be done in six simple steps

Do not ‘Optimize’

Press Save to create a ‘Registered’ file

Here is a raw shaky image…

LiMovie cannot reliably track the faint star in the raw data…it is hard to tell what is happening to

the faint star

Pre-registering so the target star is steady and can be analyzed with LiMovie…

In the ‘registered’ file, LiMovie tracks the faint star, even right next to the bright star – and we have data on both stars. If the faint

star was the one occulted, we would now have good data.

Detailed procedures for using Registax for preprocessing videos for

subsequent analysis by LiMovie are contained here:

http://www.asteroidoccultation.com/observations/Forms/RegistaxAlignment.htm

LiMovie, coupled with Registax can prove to be a very powerful

combination – one that can greatly extend the events we can detect

and report