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Helen

New to spectroscopy - some newbie questions please

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I've got the staranalyser 100 on a zwo1600 mono camera in a Wlliam Optics 98FLT scope.

I'm struggling a bit to be sure about focus!  I'm trying Christian Buil's technique of turning off the drive.  Am I looking to get the lines in the sprectrum as narrow as possible?  How far out will I be if I focus on the star?  as some nearby stars look quite out of focus.

I'm working with relatively short focus as I'mm looking at the brightest stars eg Gamma Cass, Vega.  Will I get enough data with 2s exposures, or should I go longer? and/or should I bin?

And finally, what's the best software to use for the analysis?

Thanks

Helen

PS If I upload a couple of my files could someone check they look reasonable/do a quick analysis for me?

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This is a JPEG of vega 10s - verdict?

Thanks 🙂 

Helen

vega10s.thumb.jpg.d61e34aa1f96ad38c8d2ef59576e9c46.jpg

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Helen,

2sec would have been a better starting point...

The Vega spectrum although well positioned, is blown out and over exposed.

Looking in the background you can see some fainter spectra which show some detail...

The attached (colour) example shows what you should be looking for.

I use John's BASS Project for all my spectral processing.

https://uk.groups.yahoo.com/neo/groups/astrobodger/info

Onwards and Upwards.

 

 

Vega_overexp.JPG

background spectra.JPG

vega_focused_AA7_profile.JPG

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Thanks Ken :icon_salut:

I've got some shorter ones too, so will start with those 🙂 

I'll report back!

Helen

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15 hours ago, Helen said:

This is a JPEG of vega 10s - verdict?

Thanks 🙂 

Helen

 

Hi Helen,

Good to see you here too !   

Yep way over exposed. Aim for an exposure more like the star highlighted here (a cool star showing nice molecular bands) As I mentioned on the Staranalyser forum, aim for under exposure rather than over initially as it is easier to see the features (Note how the well exposed unblazed spectrum on the left more clearly shows the features.)  Even here the correct, blazed spectrum is over exposed as Ken's spectrum profile shows, though this might be due stretching the image to produce the jpeg?)

Cheers

Robin

vega10s.jpg.99461ddee398d87d91f0ee7b88e8f772.jpg

Edited by robin_astro

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54 minutes ago, robin_astro said:

Aim for an exposure more like the star highlighted here (a cool star showing nice molecular bands)

 

The highlighted star is HD172380 at Mag 7.3 so 800x fainter than Vega (The Star Analyser is very sensitive !)  it is catalogued as spectral class M4iii.  With this information we can make a quick rough and ready calibration of the spectrum image (Here using Visual Spec, other software is available 😉 ) The dispersion is~7.8A/pixel

The blue spectrum is from the image and the red spectrum is a standard M4iii spectrum from the Pickles library of spectra.  Note the broad molecular bands mainly from TiO which can form in this star's cool atmosphere 

helen_star_calib.png

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