Double stars

[the rev]

Hello,

I would like to try and work on some double stars with my star analyser. I have tried, but seem to have a problem collecting data for the dimmer star. When I collect the spectra the brighter star seems to blot out the second star and I get very limited data. Is this because I am using a 5 inch scope which obviously shows widefield and therefore not enough distance between the stars, or is there something else I can do to improve the dimmer star.

I am also wondering if I took a series of images of a star which has is a spectroscopic binary would I actually be able to discern any difference as one star passes in front of the other with my set up?

Kate

[jnp]

Hi Kate,

This is a very noble quest!

How wide apart are we talking? Mizar and Alcor have a relatively wide separation and can be easily captured together with an SA100. First rotate the camera such that one star sits exactly above the other and you get two separate spectra. Then rotate it by 90 degrees to get overlapping spectra and see if you can make any sense of the result.

If one star is much brighter, it will, as you have found, blot out the other. A slit or obstruction may help isolate the light from the weaker star.

A 5in Mak should already have quite a long focal length. No harm experimenting with a barlow lens to see if that can help split optical doubles.

I have provided a link to my Gamma Andromedae SA100 spectra as an example.

http://dl.dropbox.com/u/87095951/Spectro/BASS%20Project/stuff/almack_00000.fit

This is an orange K class with a dim blue companion (which is 3 stars, so 4 in total!). I am unable to prove the companion star is contributing to the spectra (anyone is welcome to try). Perhaps worth a go with a slit and higher resolution?

Regarding spectroscopic binaries, I doubt a slitless setup wound have sufficient sensitivity or resolution to detect this unless you had say a blue star with a red companion, but I don't know any?

regards

John

[the rev]

Thanks John I will have a try and see what I can see