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Spectroscopes

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Anthony Rodda's picture
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Joined: 01/09/2014 - 14:15
Spectroscopes

Hi guys,

Just to let everyone know I've been keeping busy during these long light summer days & nights.

Photos attached of recently finished spectroscopes and asociated 'stuff'.

The fully clad Tragos in it's finished rigid body; the Paul Gerlach designed Lowspec2, mounted on-scope complete with aluminium tape coat; the new Christian Buil UVEX3, accompanied by a printed guider under testing; and, a 'calibration unit' built with a miniture circuitry that generates 400V from a PP3 9v battery, halogen flat bulb and 'different' "Relco" bulbs that I've found.

Anyway, I now have more spectroscopes than I've had clear, usable, nights in the last two months.  I'm going on my hols soon so they'll all occur then...

Regards

T

The Tragos...

The Lowspec2 on the bench...

Lowspec2 mounted...

Lowspec2 under initial tests...

UVEX3 with guider...

Calibration and 'Flat' unit...

Robin Leadbeater's picture
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TRAGOS limiting magnitude

Looking forward to seeing how faint the TRAGOS might go. It could potentially be a nice alternative to the modded ALPY 200 for supernova work.  (I have had some interest but copying it has been thwarted due the the unavailabity of the 200l/mm grism) What resolving power will your TRAGOS give ?

Robin

Anthony Rodda's picture
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Tragos

Hi Robin,

It sould be around R=400 @550nm for the 23um slit.

Vadim Burwitz got 350 with a much larger pixel camera.

Here's a quick neon test run.

Regards

T

Robin Leadbeater's picture
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SA100 swap ?

Ah OK, a bit high for really faint objects but I guess the SA200 could be swapped for an SA100?  Are you using the PH wedge prism?

Anthony Rodda's picture
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Wedge...

No,  I experimented with Thorlabs 4, 7 and 11 degree prisms and settled on the 6.  (I think the PH is 4 degrees?).

The "11" worked best but deviated the beam too much for my SXVH9 camera chip.  A bigger camera would probably work but I couldn't retask my Atik460.

Anyway, the easiest assembly method is to use standard eyepiece holders/spacers and just screw the four components together!  An optical train of 50mm collimating lens, prism, grating and 80mm camera lens as per Burwitz's design.  A guider at one end (Paul Gerlach's works well) and an camera connector at the other such as a T2/1.25" nosepiece type.  All that's needed is a printed tube/jacket so that the assembly can be rotated/focused at each end (to align the prism/grating with the slit and the camera).

Having built it I now know what needs putting right (!) and I'm redesigning the optics holders and guider.  I'll 'publish' the stl files in a couple of weeks.

Regards

T

Robin Leadbeater's picture
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Junk box

Yes the "junk box" approach is a simple alternative to 3D printing these "linear" transmission spectrograph designs. eg  

http://www.threehillsobservatory.co.uk/astro/spectroscopy_19.htm

http://www.threehillsobservatory.co.uk/astro/spectroscopy_18.htm

though I never got round to coupling them to the ALPY mirror slit guider

Claudio Balcon in Italy has recently classified a couple of faint supernovae using a similar home built collimated Star Analyser 100 setup

Derek Robson's picture
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Supernovae

Supernovae can be seen visually. So what extra does spectroscopy do? Is it that spectra of supernovae can be used to classify them, in a similar way that spectra of stars can classify the stars into certain spectral types?

When a stars goes supernovae, is there a change in spectra (composition wise) before and after?

Robin Leadbeater's picture
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confirming and classifying supernovae

Hi Derek

Not all candidate supernovae turn out to be supernovae, for example they may turn out to be novae, Luminous Blue Variable outbursts or other cataclysmic variables in our own galaxy. A follow up spectrum is needed to establish exactly what type of object it is. (For example the redshift measurement can be used to confirm if it is extra-galactic and the width of the lines can be used to measure the velocity of the material flung out in the explosion which is much higher for supernovae.There are also different types of supernovae produced by different mechanisms, for example core collapse of massive stars or the thermo-nuclear explosion of a white dwarf following accretion of material from a companion. These different types of event have characteristic spectral features and are very different from what the spectrum would have been before the explosion.

An introductory paper on the subject is one by Filippenko here

https://ned.ipac.caltech.edu/level5/March03/Filippenko/frames.html

also brief but more up to date this blog entry

https://astrobites.org/2016/12/02/classifying-supernovae/

I have talked more about this and how I am using spectroscopy to confirm and classify supernovae spectroscopically in more detail in a few BAA meetings a couple of which were videoed

https://britastro.org/video/11250/12234

https://britastro.org/video/13862/14769

Also short more up to date piece on the Sky and Telescope website currently

https://www.skyandtelescope.com/astronomy-news/from-lunar-flashes-to-variable-stars-pro-am-astronomy-projects/

Cheers

Robin