Seasonal ideas for the SA100

[SteveBz]

Hi Guys,

Although I never got a fully corrected spectrum for Uranus,  I was still mighty chuffed to have got as far as I did.

Can I ask what ideas people have for the SA100 that I can look for during March and April? In fact is there a spectroscopy calendar that someone has put together somewhere?

Kind regards,

Steve.

[robin_astro]

You could perhaps take look in the BAA database to see what others have been looking at for a particular time of year. (Most observers there are northern hemisphere, though accessibility will still be latitude dependent of course ).  They are generally at higher resolution than the typical Star Analyser spectra (you can limit the resolution in the search if you like) but you should be able to see the main features shown there provided they are bright enough for your setup

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

(enter the date range of interest) 

Cheers

Robin

[SteveBz]

7 hours ago, robin_astro said:

You could perhaps take look in the BAA database to see what others have been looking at for a particular time of year. (Most observers there are northern hemisphere, though accessibility will still be latitude dependent of course ).  They are generally at higher resolution than the typical Star Analyser spectra (you can limit the resolution in the search if you like) but you should be able to see the main features shown there provided they are bright enough for your setup

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

(enter the date range of interest) 

Cheers

Robin

Hi Robin,

That's very cool - and easy to access.  I can see people have been busy! Can I ask:

1) How do you calculate the resolution of those spectra?

2) What is a 'Star - Be' or 'Star - Be Candidate'?

Kind regards

Steve.

 

 

[robin_astro]

16 hours ago, SteveBz said:

1) How do you calculate the resolution of those spectra?

2) What is a 'Star - Be' or 'Star - Be Candidate'?

1) To measure the resolution you need a spectrum line which is narrow compared with the resolution of the spectrograph.  With slit spectrographs this is usually measured from the width of one of the calibration lamp lines. with a slitless spectrograph you can measure it from a line in the star spectrum you know to be narrow. You can see an example here where I used the lines in P Cygni. 

http://www.threehillsobservatory.co.uk/astro/spectroscopy_16.htm#SA200_filter_wheel

You will often see the resolution quoted as resolving power R = wavelength/resolution so for example an R of say 120 typical of a simple Star Analyser setup equates to a resolution of 50A at 6000A while my LHIRES at maximum resolution has a resolving power of ~15000 or 0.4A

2) Be stars are main sequence B stars which intermittently show H alpha in emission, from a circumstellar disc.  They are a popular amateur target as they are part of a big pro am project to track them and better understand how the disc forms and disappears. There is a database dedicated to them

http://basebe.obspm.fr/basebe/

and a website which shows which stars need spectra currently

http://arasbeam.free.fr/?lang=en

Be Candidates are stars which have been found with Be like emission but are not currently catalogued as such. (Because discs form and disappear a normal B star can turn into a Be star) There was an amateur  systematic survey to discover some of these a few years back

http://www.astrosurf.com/aras/be_candidate/auto-be-candidate.html

and candidates pop up from time to time for example in the  Gaia transient survey where they can be followed up by amateurs eg

https://www.spectro-aras.com/forum/viewtopic.php?f=40&t=2940

Another popular area of pro-am work is Cataclysmic variables.  (novae, dwarf novae, symbiotic stars etc) There are more examples in the ARAS database

https://aras-database.github.io/database/index.html

 

Cheers

Robin

 

Edited March 21, 2022 by robin_astro

[SteveBz]

7 hours ago, robin_astro said:

1) To measure the resolution you need a spectrum line which is narrow compared with the resolution of the spectrograph.  With slit spectrographs this is usually measured from the width of one of the calibration lamp lines. with a slitless spectrograph you can measure it from a line in the star spectrum you know to be narrow. You can see an example here where I used the lines in P Cygni. 

http://www.threehillsobservatory.co.uk/astro/spectroscopy_16.htm#SA200_filter_wheel

You will often see the resolution quoted as resolving power R = wavelength/resolution so for example an R of say 120 typical of a simple Star Analyser setup equates to a resolution of 50A at 6000A while my LHIRES at maximum resolution has a resolving power of ~15000 or 0.4A

So with this one that I took last year of P Cygni and processed with BASS:

The width at half intensity (6.0E5 on this plot) goes from 655.0 nm to 657.7 nm giving a width of 3.7 nm.  I should probably call that 4 nm.  656/4=164 or 656/3.7 = 177, so it's a bit over 160, say in the range of 160-170.  Is that right?

Kind regards

Steve.

[robin_astro]

5 hours ago, SteveBz said:

The width at half intensity (6.0E5 on this plot) goes from 655.0 nm to 657.7 nm giving a width of 3.7 nm.  I should probably call that 4 nm.  656/4=164 or 656/3.7 = 177, so it's a bit over 160, say in the range of 160-170.  Is that right?

Yes.  With slit based systems the resolution is fixed by the slit width but with slitless systems it will depend on the star image size (seeing etc) 

Cheers

Robin