Observation by David Swan: Gamma Cassiopeiae: spectrum

Uploaded by

David Swan

Observer

David Swan

Observed

2018 Jan 18 - 20:28

Uploaded

2018 Jan 18 - 21:10

Objects

Spectrum
γ-Cas

Equipment

200mm SCT @ f/6.3
ASI178MM
Star Analyser
FireCapture and RSpec

Exposure

Stack of 100 x 100ms frames

Location

Tynemouth, UK

Target name

Gamma Cassiopeiae

Title

Gamma Cassiopeiae: spectrum

About this image

A very clear hydrogen alpha emission line from this well-known Be star.

Files associated with this observation

gammacass.png (6.9 kB)

Like this image

Graham Winstanley, Hugh Allen, David Hancox, Peter Carson, Jeremy Shears, Ray Emery, Dr Andrew Smith, Andy Wilson, Robin Leadbeater, Nick James

Comments

Hugh Allen, 2018 Jan 18 - 21:28 UTC

That's very nice David!

David Swan, 2018 Jan 18 - 21:45 UTC

Thanks very much Hugh. Focusing is quite a challenge isn’t it? For example, I found that when I achieved a sharp tapering where the first order spec starts (in visible light of course!), the Halpha line for gamma cass wasn’t as clear as it was at a slightly different focus. What do you recommend? David

Andy Wilson, 2018 Jan 20 - 11:18 UTC

Great spectrum David! As well as the hydrogen emission you can also see absorption by the Earth's atmosphere, telluric lines, a good example between H-alpha and 7000 Angstroms.

Hugh Allen, 2018 Jan 21 - 21:29 UTC

Hi David,

As I showed in the forum conversation I adjust the focus based on the Bahtinov mask pattern formed by the zero order star image. I experimented with adjusting the focus until I got the sharpest A-type star spectrum and then used the appearance of the Bahtinov mask image to act as a reference for future focus setting. I always set the focus to give the same Bahtinov pattern. Does that make sense?

Cheers

Hugh

David Swan, 2018 Jan 23 - 22:22 UTC

Thanks Hugh - I was a bit slow on the uptake, but get the idea now. A clever system. I might buy one of these masks soon.

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