Not so long time ago I made an entry about measuring double stars with AstroImageJ software. Then I found out about dedicated software for this purpose – REDUC. This smart and simple to use program was written by Florent Losse, and you can ask for your copy at http://www.astrosurf.com/hfosaf/uk/tdownload.htm page. I got my copy pretty quick, and then needed to wait some time for clear nights to collect data. Meantime I learned how to use Reduc. It contains both simple methods just to measure separation and position angle basing on single or series of frames, but also some sophisticated algorithms to resolve very close doubles for example. You can also filter and sort frames, reject outlying measurements, stack, align and do many other things. Reduc itself does not contain any plate solving functionality, so frame orientation and scale needs to be determined other way. But I found PlateSolve2 extremely useful for this purpose – after solving any frame you just need to copy calculated Pixel Size and Angle values to proper fields in Reduction window of Reduc.
Help page of Reduc is very useful, and most probably after one evening with it you will be able to measure double and multiple systems in no time. I really liked this small but powerful software. It does not matter if you have small or large instrument, guided or not guided, if you use cooled CCD camera, DSLR or webcam – you can start collecting data for double star measurements.
Here are few of my first measurements using Reduc. For the first system I have choosen bright and well separated 11 and 12 Cam stars.
This system contains four components, and they are easy to observe visually with nice color difference. I use all 100 RGB frames (3 seconds each) to measure separation and position angle and here are the results:
|Components||Position angle [deg]||Sigma||Separation [arc sec]||Sigma|
This system was pretty wide, but then I tested more and more tight double stars as you can see in the table below. For these bright stars I used between 30 and 300 frames with subsexposure times about 0.05 seconds each.
|Image||Star||Position angle [deg]||Sigma||Separation [arc sec]||Sigma|
|Castor (alpha Gem)||52.25||1.32||5.242||0.15|
|Algieba (gamma Leo)||126.12||0.96||4.749||0.119|
For the 57 Cnc with separation 1.5″ I tested surface modeling for separation measurement, and it worked very well. I am quite happy about the results from Reduc software. There are still some workflows that I need to get familiar with, but measuring doubles with Reduc is really fun.
All images was taken with Meade ACF 10″ telescope and QHY163M camera on EQ6 mount.