I began a short observing session last Tuesday morning (12.05.09) by trying to split the well known double star Izar (also known as Epsilon Boötis) in the constellation of Boötes. Despite a hazy mist in the upper atmosphere conditions were fairly decent, but try as I might I just couldn’t separate the orange giant primary, and it’s smaller main sequence companion from each other. I was sure that a power of 166x would be up to the job, but obviously it wasn’t so perhaps someone can offer a little advice on the subject?
After about twenty minutes of fruitless scrutiny I decided to move on from Boötes to bathe in the radiance of my second morning target: Cor Caroli in Canes Venatici. The view through the 6mm plössl was delightful, but unexpectedly, and quite oddly the brighter A class primary shone with a greenish hue rather than the white or pale blue luminosity that I was anticipating. The secondary which is an F class star should have displayed a yellow iridesence, but instead showed no sign of colour.
Regardless of the perculiar spectral colours that I percieved this really was an attractive binary system to study, but I think it will be one that I will return to quite soon for a follow up observation.
Tags: Alpha Canum Venaticorum, Bootes, Canes Venatici, Cor Caroli, Double Star, Epsilon Boötis, Izar
I recently observed several doubles in Bootis as they are on the Astronomical League’s Double Star Club list, so I checked my logbook for you. I observed Epsilon on March 21, 2009, and noted it had a separation of 2.8 arc seconds. “Tight at 350x. A is yellowish, B is considerably fainter and white.” So I guess try more magnification, however it’s not uncommon for me to have try on multiple nights to get those really close doubles. 2.8 arc seconds is a really small separation, it really depends on the atmosphere. Sissy Haas in her Double Stars for Small Telescopes book says she split it at 120x. Hope that helps :) Clear skies!
I should also say my observation was with my 8″ scope and my 7mm Speers-WALER EP with a 2x barlow. About as high a mag as I use with the 8″.
Thanks for sharing that really useful information Aaron. As you pointed out, more magnification is probably my best bet. Conditions can be ‘wobbly’ at the best of times here, but I’ll stick with it. Hopefully you’ll see a sketch of Epsilon Boötis up here quite soon.
Thanks again,
Ewan