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Science for advanced amateurs

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#1 Lucullus

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Posted 19 January 2020 - 02:07 PM

Has any amateur ever done spectro-photometry or spectro-polarimetry? Are there such instruments for amateurs?

 



#2 lee14

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Posted 19 January 2020 - 02:20 PM

Check into the AAVSO website. All kinds of info there. The AAVSO has a long history of professional level work, and extensive amateur-professional collaboration.

 

https://www.aavso.or...cember 2019.pdf

 

Lee


Edited by lee14, 19 January 2020 - 02:22 PM.


#3 RobboK

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Posted 20 January 2020 - 02:29 AM

Hi Lucullus!  Polarimetry is something that has interested me for a while.  For amateurs, probably the way to go is using polished optical calcite ("Iceland Spar") in a Savart configuration (back-to-back slabs) - these are commercially available from optics firms such as Edmund Optics, Thorlabs etc and are called Mounted Calcite Beam Displacers.  You also need something to provide rotation - eg a “halfwave” plate or “retarder”. But the price is pretty prohibitive for an experimental foray into polarimetry, at least for me.  If you want to go into spectro-polarimetry, this just involves adding a filter wheel with UBVRI filters to get the polarisation at different wavelengths.  Again, unless you already have them, this is a pretty big outlay.  Small slabs of polished optical Iceland Spar are available pretty cheaply and I'm wondering if it would be possible to bodgey something up on a shoestring!

 

Anyway, here's a link to an amateur set-up, hope it answers some questions:

http://articles.adsa...000037.000.html

 

Good luck with anything you might try!

 

Cheers -

 

Rob


Edited by RobboK, 20 January 2020 - 02:34 AM.


#4 robin_astro

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Posted 21 January 2020 - 11:53 AM

Check into the AAVSO website. All kinds of info there. The AAVSO has a long history of professional level work, and extensive amateur-professional collaboration.

 

https://www.aavso.or...cember 2019.pdf

 

Lee

 

This is pretty basic stuff though and does not cover what the OP asked.  AAVSO are behind the curve in spectroscopy and trying to catch up on 10-15 years of development.  Cutting edge expertise in amateur spectroscopy lies elsewhere eg in the ARAS forum

http://www.spectro-aras.com/forum/

 

To specifically answer the questions on spectrophotometry (using either simultaneous V band photometry or absolute flux calibration) and spectropolarimetry here are some example  links

 

spectropolarimetry

http://www.astrosurf...polar2/tuto.htm

http://www.astrosurf.com/buil/polar4/

 

spectrophotometry using V mag

https://britastro.org/node/19379

If you are interested in producing research quality spectra then this tutorial is a good one (far more useful than the aavso manual)

 

absolute flux calibration

http://www.astrosurf...ibration_en.htm

 

spectrophotometry using a Star Analyser

http://www.threehill.../spectra_42.htm

https://www.cloudyni...n-with-neptune/

 

Cheers

 

 

Robin


Edited by robin_astro, 21 January 2020 - 11:59 AM.

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#5 Enkidu

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Posted 22 January 2020 - 03:50 AM

You're looking at a very small (hopefully growing) group of amateurs in any case.

 

Here's an elegantly simple overview of flux-calibrated spectra by Christian Buil: https://www.aavso.or...5#comment-33355

 

I think BeSS does not recommend this process, and these type of spectra are relatively rare in their database.

 

Given time, I'm sure AAVSO's fledgling spectroscopy program will get up to speed technically, and they have other expertise everyone can benefit from.

 

Polarimetry is fascinating!


Edited by Enkidu, 22 January 2020 - 03:54 AM.


#6 happylimpet

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Posted 22 January 2020 - 03:55 AM

On some of the facebook pro-am planetary groups, Padma Yanamandra-Fisher has been pushing for people to get into polarimetry in particular of Jupiter, and as I recall there have been some people trying, though this was a year or so ago and I'm struggling to recall.


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#7 robin_astro

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Posted 22 January 2020 - 05:28 AM

I think polarimetry (as opposed to spectropolarimetry which is a very fringe activity currently) is more common among amateurs. Here you can see  examples of both polarimetry and some experiments in spectropolarimetry using a Star Analyser

https://britastro.org/user/404

 

Cheers

Robin



#8 robin_astro

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Posted 22 January 2020 - 05:49 AM

 

I think BeSS does not recommend this process, and these type of spectra are relatively rare in their database.

 

 

The BeSS standard is actually agnostic on absolute flux calibration and is a minimum standard designed for a specific application. It just states that the spectrum should preferably  not be normalised (rectified) to remove the continuum shape.

 

Historically amateur spectra were mainly just calibrated in relative flux (ie corrected for instrument response and atmospheric extinction) and this is still true but some amateurs are now routinely calibrating in absolute flux, either by taking simultaneous photometry measurements. See David Boyd's spectra in the BAA database for example 

https://britastro.org/specdb/data.php

or (tougher as it requires photometric sky conditions and a combination of wide and narrow slit spectra for good accuracy), directly from the spectrograph flux eg as described by Christian Buil 

 

Cheers

Robin


Edited by robin_astro, 22 January 2020 - 05:52 AM.

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#9 robin_astro

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Posted 22 January 2020 - 06:11 AM

 

 

Here's an elegantly simple overview of flux-calibrated spectra by Christian Buil: https://www.aavso.or...5#comment-33355

 

 

Yes that (and the subsequent) posts  from 2013 describe the development of techniques for absolute flux calibration of spectra by amateurs within the ARAS group (both direct from spectra and from V mag values). Note Arne Henden's comments on the issues encountered doing absolute flux calibration by the direct method, the spectroscopic equivalent of doing absolute rather than differential photometry.

 

Cheers

Robin



#10 Lucullus

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Posted 04 February 2020 - 07:23 AM

This is pretty basic stuff though and does not cover what the OP asked.  AAVSO are behind the curve in spectroscopy and trying to catch up on 10-15 years of development.  Cutting edge expertise in amateur spectroscopy lies elsewhere eg in the ARAS forum

http://www.spectro-aras.com/forum/

 

[...]

 

Cheers

 

 

Robin

A point that makes me wonder since your post: Why is the AAVSO behind in development? How can one be "behind"?

Sure technology advances, but I am convinced developments in spectroscopy and related areas are not something that amateurs can really benefit because those developments take place at the forefront of research. Or am I wrong? I mean the most advanced amateurs in spectroscopy I know of have done radial velocity measurements http://astronomyonli...ts&SubCate=EP03 http://www.spectrashift.com/index.php of a single star. But I have not read about any progress and an Email remains unanswered for years now. And this is only one amateur or semi-professional group trying this in the world. The rest of amateurs uses Rainbow Optics Star Spectroscope, RSpec-astro, Shelyak, and Baader products and do "simple" stellar absorption line or doppler measurements on planets, don't they?

Bottom line, what is there in ARAS what isn't in AAVSO?

 

 

Btw, is Rainbow Optics out of business??


Edited by Lucullus, 04 February 2020 - 07:23 AM.

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#11 robin_astro

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Posted 04 February 2020 - 07:02 PM

It is difficult to know where to start to be honest. For an overview I recommend investigating the ARAS forum and website for an idea of the depth and breadth of amateur involvement in spectroscopy at research level.

http://www.spectro-aras.com/forum/

http://www.astrosurf.com/aras/

 

If you then look up in the literature via ADS some of the names of  the posters there you will find hundreds of references to amateur spectra used in research going back 15-20 years. Typing

 

author:"R Leadbeater" or  abs:"R Leadbeater"

 

into

https://ui.adsabs.harvard.edu/

for example will bring up my 62 references,  most of which relate to my spectra being used in research in some way

 

The Pro-Am database BeSS  contains many tens of thousands of spectra of Be stars produced by amateur and used in research

http://basebe.obspm.fr/basebe/ 

click on "statistics"

 

Francois Teyssier edits a monthly newsletter on amateur contributions to research into cataclysmic variables, in particular symbiotic stars which is recognised by professionals in the field and is indexed in ADS eg

https://ui.adsabs.ha...L...4T/abstract

they are also available on the ARAS website

 

Concerning detection of planets by doppler measurements, discovery of new ones  is probably out of the reach of amateurs currently but Christian Buil demonstrated the measurement of 4 known exoplanets using commerically available equipment

http://www.astrosurf...rasolar/obs.htm

and more recently has matched the precision of his measurement on 51 Peg b to that of the professionals who first discovered this exoplanet  

http://www.astrosurf...anet2/51peg.htm

 

This is just a flavour of what is going on in the mature field of pro-am research using spectroscopy, none of which has had AAVSO involvement

 

Cheers

Robin



#12 robin_astro

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Posted 04 February 2020 - 07:18 PM

As an example of where AAVSO has some catching up to do, compare the AAVSO manual produced for amateurs interested in getting into spectroscopy

https://www.aavso.or...cember 2019.pdf

 

To the content of the workshop aimed at the same audience by an ARAS and BAA member for the SAS conference last year (The top one in this list of resources on the BAA website)

https://britastro.org/node/19378

https://britastro.or...eur Spectra.pdf

(a direct link to the slides)

 

I am not criticising the AAVSO, it is just that in the field of spectroscopy, amateurs and professionals have been working together for many years now and it is understandable that is taking a while for AAVSO as an organisation to come up to speed with what is for them a new venture 

 

Cheers

Robin


Edited by robin_astro, 04 February 2020 - 07:25 PM.


#13 gregj888

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Posted 04 February 2020 - 11:40 PM

SAS might be of interest to some.  Their goal seems to be Pro-Am collaboration.

 

Call for papers, meeting in June.

http://www.socastros...er_Jan_2020.pdf




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