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Spectroscopy equipment

  • John D
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1 year 9 months ago #104173 by John D
Hi Guys,

Quick question to the pros here: Have you ever done spectroscopy? If so what equipment did you use?

I ask because I am looking at this Rspec Star analyser:

www.rspec-astro.com/sample-projects/

Take a look, some really interesting projects! :D

Clear skies,
John

John

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1 year 9 months ago - 1 year 9 months ago #104176 by mjc
For diffraction grating consider

www.patonhawksley.co.uk/staranalyser200.html

I only played around with mine - never did calibration.
A diffraction grating is enough to get started.

Mark C
Last Edit: 1 year 9 months ago by mjc. Reason: Missing url

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1 year 9 months ago #104179 by michaeloconnell
I've dabbled a little in it.
RSpec is good software. Worth buying.
See my homepage www.astroshot.com for an example on a supernova.
The Star Analyser 100 is plenty to get started.
www.patonhawksley.co.uk/staranalyser100.html
Loads of projects you can do with that.
Also, take a look at this thread:
www.irishastronomy.org/index.php?option=...&id=99755&Itemid=211

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1 year 9 months ago #104188 by John D
Michael,

I am really impressed with your work! This is something I've been wanting to try for a while. Did you purchase your grating from Paton Hawksley website, if so did you need to buy a spacer too?

Thanks again,

John

John

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1 year 9 months ago #104189 by michaeloconnell
John,
I bought mine from Shelyak Instrruments in Ferance.
www.shelyak.com/rubrique.php?id_rubrique=4
I didn't get buy spacers. However, I did buy the prism.
This helps to keep the spectrum on the chip at the same time as the star.
Makes calibration a fraction more difficult, but makes imaging much easier.
If you decide to order it and give it a shot, I'm happy to do a Google Hangout and help you with calibration in RSpec.
Michael.

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1 year 9 months ago #104190 by eansbro
I've used RSpec to be good for processing and analyzing star spectra. It really depends how far you want to go in spectroscopy. Their are other spectroscopy software that can extract more detail than RSpec.

It depends how far you want to go and what applications you are interested in. I have been interested in wide fields of view of star clusters, comets, Veil nebula. Michael's approach is a good starter using a transmission grating in the optical train of your telescope.

I have built 4 spectrographs over the years. From simple systems using 200 l/mm transmission gratings to 1200 l/mm reflective gratings. I've taken images of dense star fields and wide fields of comets with there nucleus and coma. Typically fields of view of from 3 to 30 degrees. The limiting factor of transmission gratings is low resolution. I've used reflective gratings with off the shelf optics.

One of the designs involves the bilateral movement of the slit assembly is synchronized with the rotary movement of the diffraction grating. The camera records in a scan mode to achieve a wide field of view. see references below if your interested in building this one.

Another design version called a Slit-Free Multiplexing Spectrograph Design provides a FOV of 30 degrees. This has similar resolution to the best spectrographs. The other advantage is that you have simultaneous side by side images of both the target stars and spectra.

Eamonn


Ref: Ansbro E. "Wide-field fast scanning spectrograph", Proc. SPIE 4876, Opto-Ireland 2002: Optics and Photonics Technologies and Applications, 1265 (March 17, 2003); doi:10.1117/12.464052

Ref: Ansbro E. "A new wide-field spectrograph", Proc. SPIE 5492, Ground-based Instrumentation for Astronomy, 1290 (September 30, 2004); doi:10.1117/12.550887

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1 year 9 months ago #104196 by John D
Michael, Thanks for your info, I may take you up on that offer when I get my rspec ;)

Eamonn, I am truely amazed by all the different techniques and methods you have done. When you say "similar resolution to the best spectrographs", what kind of prices are we talking about with this technique?

Also, have you done Exoplanet doppler shifts with this technique, I am hoping to study Exoplanets in my Masters so it is a bit of an obsession of mine!

Also, what other software could you recommend to extract more detail than the Rspec software.

I am quite excited about the prospect of spectroscopy now! Thanks guys! :D

John

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1 year 9 months ago #104201 by eansbro
John,

I haven’t done Doppler shift measurements of exo planets, except exo planet transits.
You could look at the spectrographs I’ve built that may be applicable for exo planet observations. You’ll realise that all the systems I have designed and built are for wide field of views taking in multiple objects, except No.4. In your case you may only need a one star through the slit type. No. 4 may be suitable as it uses a grating 1200 l/mm (high res). This is fibre fed to a 0.4m telescope.
I’m not sure if No.1 is suitable as it uses a large grating size (5” x 4”).(medium res)
Its all down to the aperture size of the telescope/ spectrograph to collect light and to provide ever increasing resolution.

Software:

User friendly versions are BASS (Basic Astronomical Spectroscopy Software), ISIS (Integrated Spectrographic Innovative Software), More complex for extraction is SPECTOOL from IFAF is a GUI Spectrum Display and Analysis Tool, other user friendly ones are VisualSpec, SpIRIS, SpcAudace, PRiSM, Astro-Linux.

In order to give you more choice and costs I have built 4 types of wide field spectrographs.

1. Own design as mentioned references. Reflective grating at 400 l/mm ($1.2K)
2. Own design Slit-Free Multiplexing Spectrograph reflecting grating 300 l/mm and high speed optics. ($500)
3. Conventional using a ROS 200 l/mm transmission grating within an f/5.6 telescope ($200)
4. Czerny Turner design. ($1K)

If you need more technical details I can send on to you.

Optical Spectroscopy Considerations really depends on your application. I’ll give you some idea and resolution:

Trade-Offs Encountered With Traditional Spectrographs
Field of view
Whatever the field lens “sees” is focused onto the
entrance slit, creating a summed spectrum of all
objects, or selected object if field lens is a telescope, and
unable to distinguish multiple objects from each other

Big advance in 1980s: Replacement of exit slit with CID/CCD Array detectors –
Creates simultaneous multiple wavelength ability

Spatial resolution: If the spectrograph is an imaging spectrograph, with no
entrance slit, e.g. camera with ROS or Star Analyser type transmission grating,
then the spectrograph sees the whole field of view as set by
the field lens and its focal length.

The State Of The Art Multiplexing Spectrographs are Multi-slit WFCCD spectrograph at Las Campanas.
Fiber-fed multi-object spectrograph: Sloan Digital Sky Survey
Spectrographs at Apache Point Observatory

Each are complex, and capture generally less than 1-degree of sky

Slit-Free Multiplexing Spectrograph Design is an
Off-Littrow Reflection Grating Design for
both Echelle and Non-Echelle, inducing
astigmatism to form slit-like images of
point sources at the tangential focus
No Slits – provides wide field
Field of View set by Entrance Lens, which
is very low f/# to form highly reduced
image of wide field.

Off-Littrow Mount provides high spectral resolution, wide bandpass, and increased
line intensities.

Eamonn

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1 year 9 months ago #104209 by John D
Wow, that is truly a treasure trove of information Eamonn. Thanks so much.

I will look up those software you mentioned and compare them to the Rspec software

Thanks again,

clear skies,

John

John

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