14 replies to this topic

[Astroman007]

Hello all,

 

Over the past year I've developed an interest in hunting down carbon stars. To aid me in my search I've been looking for a print atlas of carbon stars, but so far no luck. Does such a thing exist? If so please share. If not then I'll have to make do with the various incomplete online lists I've turned up and keep cross referencing with my star atlases.

 

Thanks!

[scottinash]

You may have discovered this site by John Barentine? It is done well!

 

https://www.johncbar...-star-list.html

I’m also interested if someone will churn up a printed atlas.  

 

Edited by scottinash, 24 May 2025 - 01:01 PM.

[Cotts]

The S&T Pocket Sky Atlas shows carbon stars on its maps.

 

Dave

[archival]

You have may have discovered this site by John Barentine? It is done well!

 

https://www.johncbar...-star-list.html

I’m also interested if someone will churn up a printed atlas.  

Technically there is such an atlas.  It should be complete for most visual observers in the north but will contain some none carbon stars.

 

It is basically Birmingham's red stars, or more specifically the published and updated version by Espin, which are plotted on the atlas charts of Norton's Star Atlas 16th edition and earlier.  They are denoted by E-B followed by a number.  In the same atlas red stars are marked by an R or Ru for ruddy.  They will not all be carbon stars but you will be able to locate them on the charts using your lists and the charts were made with visual observers with modest telescopes in mind.

 

You'll be able to find the third edition of the catalogue of galactic carbon stars listed here

 

ftp://cdsarc.cds.unistra.fr/cats/III/227/

 

in a flat text format that you may be able to import into your computer star atlas of preference.  The ones that have any sort of magnitude given for them will be observable and the catalog.dat file has the list of othernames for the objects so you can use variable star names to search in your star atlas software even if you can't import this catalogue into it.  The key to the columns is in the readme file.

[Sagitta]

Hello all.

 

There is a beautiful carbon star atlas created by Daniel Herron and it can be found on his webpage thestarhopper.com: 

 

http://www.thestarho...Chartslarge.pdf

 

Happy carbon star hunting!

Edited by Sagitta, 24 May 2025 - 01:10 PM.

[scottinash]

Hello all.

 

There is a beautiful carbon star atlas created by Daniel Herron and it can be found on his webpage thestarhopper.com: 

 

http://www.thestarho...Chartslarge.pdf

 

Happy carbon star hunting!

 

This is worth printing! Thank you.

[ButterFly]

Hello all,

 

Over the past year I've developed an interest in hunting down carbon stars. To aid me in my search I've been looking for a print atlas of carbon stars, but so far no luck. Does such a thing exist? If so please share. If not then I'll have to make do with the various incomplete online lists I've turned up and keep cross referencing with my star atlases.

 

Thanks!

Carbon stars are dynamic.  Their colors change as they expand and contract.  To that end, logging software along with the chart is something I must recommend for such an object.  SkySafari comes to mind.  Not only can it display things solely within a particular list, it (v7+) can also tell you whether such objects were observed in any list you have.  To help out with the variability, duplicating the list for each observing session is one method of attack.  That can get out of hand though, with many, many lists accumulating over time.  A single "observed" list can help get around that, with the caveat below.

 

The color perception of the star depends not only on where it's at in its cycle (the actual color), but also the aperture you are using.  I would suggest you maintain an appropriate list for each aperture you will use.  Not only will that weed out stars that you won't see color in at all, but it can also help you track the changes with respect to the aperture more easily as well.

 

Carbon stars really are fun, but the most fun thing about them is watching them change.

 

Don't worry about tablets being "bright" or whatever.  They can be dimmed down more than adequately for ordinary use, but this isn't ordinary use.  You want to see the color, so dark adaptation is bad!  These are beginning of the session objects, when you're still waiting for dark adaptation to kick in and alter your color perception.  Try that out too!

 

Having a chart of uniform color descriptors is also very handy.  The named color chart in Carbon Stars Will Make You See Red, for example, will help make your notes more uniform, from one night to the next, and one aperture to the other.

[scottinash]

Carbon stars are dynamic......

Thank you for the very informative observing advice, Sevan.  

[AZStarGuy]

That AL list is great! 

 

It doesn't have the finder charts like the AL list, but the Saguaro Astronomy Club here has a downloadable list of "red" stars on their Downloads page found here: https://www.saguaroa.../sac-downloads/

[Cotts]

 Carbon Stars -4.0 C.I. copy.pdf   26.92KB   19 downloads

 

I made this list a while ago - the top 21 Carbon stars by B-V index.  These are the very reddest ones out there!  When you get indices below 4 they really aren't red.  They are orange or yellow orange.

 

You want red, stay above 4.0...

 

Dave

 

 

[Starman1]

Here is a list of 330 carbon stars with variability range and classifications:

https://www.saguaroa.../sac-downloads/

Go down the page to "Saguaro Astronomy Club Red Stars Database version 2.0"

 

BTW, there are other resources there as well.  The DSO database is excellent (8-9k objects).

[Starman1]

Carbon Stars -4.0 C.I. copy.pdf

 

I made this list a while ago - the top 21 Carbon stars by B-V index.  These are the very reddest ones out there!  When you get indices below 4 they really aren't red.  They are orange or yellow orange.

 

You want red, stay above 4.0...

 

Dave

All these stars are variable.  They are the reddest when expanding (going dimmer in magnitude) and reddest when nearing the bottom of the variability range.

They are less red when shrinking (going brighter in magnitude), and the least red and most orange when nearing the top of the variability range.

[archival]

All these stars are variable.  They are the reddest when expanding (going dimmer in magnitude) and reddest when nearing the bottom of the variability range.

They are less red when shrinking (going brighter in magnitude), and the least red and most orange when nearing the top of the variability range.

As you say B-V colours are variable for red LPV variable stars so more importantly it has to be ensured via statement or reference, and not just by hope, that the B-V measure being quoted are at least near contemporaneous measures.

 

The General Catalogue of Variable Stars can be an assistance for red objects as it carries the range of B-V sometimes and the spectral class range often.

 

A simpler clue can be to use the oldstyle R and N spectral classes.  In temperature terms they are parallel to G to K to M spectral types but for carbon rich objects.  Also N stars seem to be the most red.  This was updated to the C spectral class where R kind of goes up to C5 or thereabouts and C5 onwards is kind of equivalent to old N.

 

It is also two dimensional (three if you include the luminosity class) thanks to the second number which is related to the Swan Band strength, or rather the strength of the carbon absorption bands in general.  Although some of these can reach the red end of optical they tend to be strongest in the blue and especially green areas of the spectrum.  An emission line version can be thought of with respect to the images of comets that look green.  So if you have a variable object that is near minimum light which has a spectrum of C7,6 you have cool (the cooler a star usually the redder) with fairly large parts of the blue and especially green continuum supressed (less blue and green = relatively more red).  Possibly there is emission from red Swan bands too, I don't know.

 

The variability doesn't matter that much for some of them as the SR or semiregular variables have a low range of magnitude change and the Lb or red irregular long period variables have very small range in brightness.  Although quite well known Mira variable carbon stars are known there are more SR ones and many more Lb ones.

 

R Leporis, Hinds Crimson Star, often called the reddest, is a Mira of spectrum C7,6e newstyle, N6e oldstyle (e stands for emission lines).  C7 and N6 are temperature of the photosphere related. The 6 in C7,6 shows strong Swan Bands.  Magnitude range is around 6 in the visual so it will have differing shades of red when fainter or brighter.

 

V Aquilae is often described as blood red and ranges from C5,4e to C6,4e, formerly also N6.  Swan Band isn't very strong but not week.  This is a semiregular variable, an SRb class - which means two or more periods (SRa are more Mira like but lower amplitude variation), with a visual magnitude range of barely 2 so does not change in colour all that much.

 

Y CVn, La Superba, also a multiperiodic semiregular variable or type SRb, is C5,4 or N3, and has smaller B-V listed, but is claimed as a quite red star in books.  It is also a J star, which simply means the carbon-13 isotope is relatively more prominent compared to the far more common carbon-12 isotope in the star's atmosphere.  It also has cool circumstellar matter surrounding it which can redden stars.

 

In other words make sure the B-V values are taken on the same night or at least week and use the modern spectral types to give a better idea.  Even more recently the spectral subtypes CR and CN followed by numbers are used with some allusion to the old R and N types, this allows use of things like CJ for the J stars and CH for the hydrogen deficient stars (which can be more carbon star like because of a hydrogen shortage rather than a carbon excess and often aren't very red, just reddish).

 

As with much of astronomy's pigeonholing the rules apply except for when they don't.  It's like learning a foreign language, they teach you the regular verb groups and they sound good with solid rules but it turns out the spoken language uses the more archaic pre-reform verbs known as the irregular verbs with various rules you have to memorise, even if they have small groupings themselves each group's rules differ from any other group.

[Cotts]

I asked this question a while back in another thread. Considering that the Index changes with magnitude what is actually being shown by a single b-v to two decimal places? The mean? Minimum or maximum value? False advertising?
Dave

[Starman1]

Happy birthday, Dave.

 

My recommendation is to look for V Hydrae.

Spectral class N; C6

533 day period +/-

mag.range 6.5-12

B-V 5.5 (!) +/-

It is the reddest star I've ever seen in a telescope: blood red when near minimum.  Obviously most of its light in the IR.