Affiliation
American Association of Variable Star Observers (AAVSO)
Sat, 01/10/2015 - 02:01

I had a good discussion with Tom Field, the developer of RSpec, at the AAS meeting.  Tom is highly interested in supporting the AAVSO diffraction grating project and working with us to enhance his product to include new features (such as 1D FITS output images).  I have used RSpec a bit, and like both the user interface as well as the many video tutorials that Tom provides.  For the diffraction gratings, I think RSpec is a good match, and with the additional tuning, has the potential to produce scientific-quality spectra.

Towards this end, Tom is willing to give our group a special discount on RSpec.  For the next two weeks, those who ordered gratings through the AAVSO group purchase, as well as those who have ordered gratings in other ways in the past, but who are part of the AAVSO community, are eligible to purchase RSpec for $59.  I will post the link on the AAVSO governance forum (since it is a members-only forum), and will send the link to those who are not AAVSO members but who purchased gratings through our group purchase.

Enjoy!

Arne

Affiliation
None
RSpec

 

Hi Arne,

That is certainly good news. I am please to see Tom offering RSpec at a discount to the AAVSO. I know some people will still wonder why they should pay for a spectrum processing software program when several freeway programs are available. I have used most if not all the freeway programs and while they certain work, for the beginner they can be a big hurtle. As such RSpec is by far more friendly and can help a newcomer understand what they can do with spectroscopy and how they can do it. This is all in a very friendly and easy to use environment.  If you go astray and mess up, redoing things is very easy and this encourages the user to experiment, something that is usually dangerous with the freeway (crashing the program or getting hopelessly lost).

I look forward to seeing data produced with RSpec on this forum.

Jeff Hopkins (187283)
Hopkins Phoenix Observatory

Affiliation
American Association of Variable Star Observers (AAVSO)
Hi Arne,
Have you consulted

Hi Arne,

Have you consulted any of the prominent figures in amateur spectro circles for advice on software?  (Christian Buil, Robin Leadbetter, Ken Harrison, ...)

I only ask as I doubt anyone who I have been involved with in spectro would recommend RSpec.  I can't comment on it with any authority as I am not a Windows user so have used neither RSpec or any of the common alternatives (VSpec, ISIS & BASS) but I have not seen anyone using RSpec for scientific work.

Obviously you want to make your own decision on your recommendations but I would definitely consult some of the folks above, there is a considerable wealth of experience on tap there.

Malc, CAS, Christchurch, NZ

Affiliation
American Association of Variable Star Observers (AAVSO)
RSpec

Hi Malc,

Most of my professional spectroscopy work has been with slit spectrographs, either long slit or echelle.  What I was looking for when forming the grating purchase was the entire process, from the equipment through the software, archiving and analysis phases.

I've used IRAF a lot, and prefer it for any serious spectroscopic work because it has been vetted by hundreds of professionals, the algorithems are clearly explained, and the software source code is available.  However, for the gratings, my primary factors for choosing RSpec were its ease of use, documentation, and support.  There are several changes to make the results more scientifically useful, but Tom is willing to put effort into the process.  The other choices you mention all have good features, but do not support the diffraction gratings as cleanly as RSpec does.

Frankly, when it comes to any software, there are supporters for every package, and for usually good reasons.  In photometry, I don't care which package someone chooses as long as the results are useful for the AAVSO.  The same goes for spectroscopy, and when we start supporting the more complex slit spectrographs, my guess is that we won't recommend any specific software system, but instead work with the vendors/developers to ensure that the results are good and standardized to the extent necessary for archiving and community use.  We're not there yet, so I'm starting "small" and making sure that the diffraction gratings are done right.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
Yes, Tim, RSpec is download

Yes, Tim, RSpec is download only.  

However, if for some reason you need a DVD, we can burn one and mail it to you at no charge. (It won't have  a label with pretty graphics, though!)  :-) 

 

Tom

Affiliation
American Association of Variable Star Observers (AAVSO)
Rspec

I had the priviledge of being a beta tester for RSpec. It is great software, easy to use and intuitive. Tom has done an outstanding job of making videos for training. A few years ago I attempted to port and use IRAF. Let's just say that with a busy work schedule I just couldn't dedicate enough time to learn it's use! I have also used several of the European spectra programs. RSpec is much easier for the casual researcher to use. Tom Field is also an incredibly helpful and enthusiastic developer. He has answered every question and even presented, via internet a talk to my college astronomy class!  I will look forward to the changes that Arne would like to see!

Paul Temple

 

Affiliation
British Astronomical Association, Variable Star Section (BAA-VSS)
Software choice

Yes Arne and I have discussed software before :-)

Note this is my personal take on the choice of software and the reasons I use the software I do.

I personally use Visual Spec mainly for the Star Analyser and ISIS to reduce spectra from my other instruments. This is partly historic but also I personally like the security of knowing the software has been developed by experts in the field who know more about the subject than I do which means do not have to interrogate the author to closely or delve too deeply into the program to find out if it is working the way it should. (But I admit I am OCD about this sort of thing, as I was in my professional career.) Tom freely admits he is relatively inexperienced in this field.  I worked closely with Tom in the early days of RSpec and thoroughly tested and improved its basic functions but it has grown in complexity significantly since then and would need to reassure myself that those new functions are ok before using Rspec for serious work.

From my perspective, for beginners RSpec is probably the easiest to use with the Star Analyser and is an excellent choice for beginners, with Visual Spec (on which RSpec is quite closely modelled) a close second. I can recommend either of these to beginners (I do not know enough about BASS to comment) The main advantages of RSpec over VSpec are the real time display, 32 bit image handling and  reliability (Vspec is indeed still prone to crash occasionally at the worst possible moment- you learn to save your intermediate results! ) Two current weakness of RSpec for Star Analyser users I know of are the rudimentary background removal handling (unless this has been improved recently) which is important for fainter stars and for accurate instrument response correction (the latest versions of Vspec has a flexible background subtraction capability (similar to ISIS) which it would be nice to see RSpec adopt) and lack of support for Fits file output which I consider a show stopper for Pro-Am work.

For Pro-Am spectroscopy, ISIS has become the de facto standard apart from a few amateurs using IRAF or ESO MIDAS and I recommend ISIS to anyone doing spectroscopy other than with the Star Analyser etc (ISIS can be used with the Star Analyser but it is not so straightforward)  The big advantages of ISIS are its provenance (written by the worlds leading amateur spectroscopist with over 20 years experience in the field) and that it follows professional best practise data reduction procedures with a high degree of automation, using standard pipelines for most common spectrograph configurations, producing  fits files with well documented headers. The degree to which this improves consistency between observing sessions and between observers is impressive.  I would personally be surprised if RSpec could match this level of capability and quality in the forseeable future without a high degree of input from experts in this field

Robin

 

I'll say honestly that if you

I'll say honestly that if you pro-am collaborate with me, I'll want the dark subrtracted flatfielded images and I'll do the rest.  I bet most pros feel the same way.  So what you are using to do the spectral extraction for yourself should be largely based on what you are comfortable with and what you like.

 

Affiliation
American Association of Variable Star Observers (AAVSO)
BASS grating software

Guys,

Don't shoot the messenger!

I like Robin worked closely with Tom in the initial phases of the development of his commercial software. He has done a great job and made initial use of the grating an easier task.

Considering "moving up the food chain" to find a suitable software package that can grow with your capablities, I would honestly recommend you at least look at John's BASS project. Over the last few years this processing package has grown and developed to meet the needs of the amateur spectroscopist.

The documentation and available tutorials are first class. It can handle very well the grating zero order spectral image and with the minimum of  hassle can handle tilt and slant corrections as well as background removal, calibration and can display 1D fits (with header data compliant to the BeSS standard) which the professionals are looking for.

To me it's a "one stop shop". John is VERY responsive at any amateur request and has incorporated many new features to meet our needs.

Please check it out....

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

 

 

 

 

Affiliation
British Astronomical Association, Variable Star Section (BAA-VSS)
Pro-Am data reduction

Perhaps it is the added complexity and effort needed per result but I like to own my data and keep closer to the action than perhaps the average photometrist does. I take pride in being able to reduce my data to a professional standard. 

For me probably about half the data which ends up getting published has been reduced by me. In either case I always reduce my own data as well though, comparing my result with that of the pros. (On  more than one occasion I have found issues with the professional reduction)  I keep all the raw images of course in case of queries and put my reduced data into the various databases (BeSS, ARAS etc) so it is easy to see at a glance what the spectrum looks like reduced.  

Doing this also allows me to compare my data with other observers and identify any potential issues early. (The BeSS database submission system with its mentoring element has proved an excellent way of improving the quality of amateur spectroscopic data) 

Having all the data from various observers reduced by one person using the same software can certainly help consistency though if there is available resource. This is never done routinely for AAVSO photometry data though as far as I am aware so I am not sure it should be strictly necessary for spectroscopy either provided robust data reduction procedures are used.

Robin

Affiliation
American Association of Variable Star Observers (AAVSO)
Very generous!!!

 

I just want to thank Tom Field and his co-wrokers for this incredibly generous offer!

Cheers,

Doug

Affiliation
American Association of Variable Star Observers (AAVSO)
Software Choice

I am very new to spectroscopy and only have processed a few spectra. I found Buil's ISIS to be the best choice for me as he provided screen-by-screen tutorials with example files that guided me through the process.  This is a program I feel I can grow with as I progress. Is it the best "beginner's software?" I cannot comment, not having investigated all the alternatives.

Ed

 

 

Affiliation
American Association of Variable Star Observers (AAVSO)
Magnitudes from Spectroscopy

Hi Arne, Tom and others,

I have software for deriving Sloan and Johnson-Cousins magnitudes from radiometrically calibrated spectroscopic data. If there is enough interest, I could make this into a stand-alone application or perhaps help to incorporate it into RSpec.

Best regards,

Tony Mallama

 

Affiliation
British Astronomical Association, Variable Star Section (BAA-VSS)
Photometry and Spectroscopy

Hi Tony,

I am not sure that RSpec would be capable of producing  spectra calibrated in absolute flux currently.

Radiometric calibration of spectra is pretty tough from the typical amateur observatory and as far as I am aware, is currently rarely done, except by a few  advanced amateurs and even then not routinely. Shelyak did recently introduce stepped slits for spectrophotometry as options to their spectrographs to aid radiometric calibration however and ISIS does have this capablity and can also produce photometric data from radiometrically calibrated  spectra based on standard filter passbands. It might be interesting to compare the results it produces with that from your software.

A potentially interesting alternative technique, particularly for AAVO observers can be to use photometric data to radiometrically calibrate  spectra which are only calibrated in relative flux (which is how the majority of amateur spectra are calibrated today) ISIS also has this capability built in. 

This article by Christian Buil on various radiometric calibration techinques for the amateur may be of interest

http://www.astrosurf.com/buil/calibration2/absolute_calibration_en.htm

and I can dig out some of the detailed discussions on the subject on the ARAS forum if people are interested

Robin 

Affiliation
American Association of Variable Star Observers (AAVSO)
Photometry and Spectroscopy

Hi Robin,

Christian Buil’s article does indicate that ISIS can produce magnitudes from radiometrically calibrated spectra. Yes, I would be interested in comparing my results with those from ISIS.

There are a few other approaches that might be worth exploring too. I don’t want to give up too easily because of the tremendous amount of photometric information available in spectrally resolved images. In principle, one could derive a complete set of 5 Sloan magnitudes and 7 Johnson-Cousins magnitudes from a single image.

One approach would be to generate raw magnitudes from uncalibrated spectra of a variable and a comparison star. These raw values could then be processed with a conventional photometry reduction program that applies extinction and transformation corrections. This is essentially multi-band differential photometry but the advantages are that all bands are recorded simultaneously, photons are used efficiently and no time is lost changing filters.

In another approach an observer should be able to derive a filter-by-filter relationship between their extinction-corrected spectroscopic magnitudes and standard star magnitudes. This would be almost equivalent to achieving radiometric calibration in SI units and should allow for transformation between their spectral system and standard magnitude systems.

Related to the idea above, suppose that only one magnitude, say Sloan r’ is available for a star. That value could set the scale for radiometric calibration and then the other magnitudes could be derived. In this way absolute photometry would be feasible even if only relative radiometric calibration is available.

Finally, color indices are obtainable even when absolute photometry is not. For example, one could follow color changes during a binary star eclipse in order to assess the temperatures of the component stars.

I may have oversimplified these processes and I don’t mean to indicate that they would be trivial. Several may also overlap current capabilities in ISIS and other programs. However, I think that they are worth exploring a bit further. If they prove to be workable, then any spectroscopy application program could be enhanced. I’d be interested in feedback (from anyone) on this forum or off-line. My email address is anthony.mallama@gmail.com.

Best regards,
Tony Mallama

P.S. I am learning more about the currently available pro-am software each day. The last stellar spectrum that I recorded was on a Kodak 103a-E glass plate around 1974, so I need to get up-to-date.   :-)