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Observing >> Variable Star Observing and Radio Astronomy

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Doc Willie
Carpal Tunnel
*****

Reged: 03/31/10

Loc: Mid-Hudson Valley, NY, USA
Carbon Stars
      #6229973 - 12/02/13 07:14 PM

I am just starting the AL Carbon Star list, and would like to open this thread for an ongoing discussion of carbon stars.

I will begin with my first night out on 29 Nov 2013, at our club's monthly dark sky party. I was usng my 8" Celestron SCT on a NexStar mount. I did not have a specific observing plan, so I just picked a few stars that looked well placed by constellation. Not all of them had SAO numbers that were listed in the NexStar's controller.

As it was, I was not able to make any clear observations. I was using a laser pointer, and between the dry air and cold, it was not producing a usable beam. Second, some of the stars were not marked in the Pocket Sky Atlas. I may have been looking right at some of the targets but could not be sure since I did not have a more detailed map or finder chart. I finally gave up and went for R Leporis as my first official AL target since I knew where that was.

I should also mention that it was very cold, and although I managed to keep warm until the last half hour or so, everything was a struggle.

So, my lessons so far are:

1. Plan some targets for the session.

2. Bring a Telrad.

3. Bring a more detailed map and/or finder charts. I have a Great Sky Atlas, so I could probably just copy those pages I need.

4. Carbon star observing offers a different set of challenges than DSOs, especially the Messiers, which are almost always pretty easy to indentify once you find them.


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old_frankland
Carpal Tunnel


Reged: 03/28/05

Loc: San Francisco Bay Area
Re: Carbon Stars new [Re: Doc Willie]
      #6231369 - 12/03/13 12:48 PM

Nice project.

I have an old student version of The Sky planetarium software, very basic, but good for most objects down to 10th magnitude. I locate my targets for the evening then print out charts, usually 2; one widefield with the major constellation stars recognizable, the second narrower field I can use for star hopping and 'ID'ing the object of interest.

I'm also using a entry level CCD camera and a Star Analyser 100 spectroscopy grating to record the spectra. The simple spectrascope arrangement is very helpful for identifying, often locating a given type of star. The carbon stars have a very distinctive spectra with an obvious absorption line for sodium right in the middle of the spectrum.

http://www.lafterhall.com/WZ-Cas_HD224855_20131113-0400ut_001.jpg

http://www.lafterhall.com/RS-Cyg_SAO69636_20131113-0300ut_001.jpg

So many cool things to see!


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Doc Willie
Carpal Tunnel
*****

Reged: 03/31/10

Loc: Mid-Hudson Valley, NY, USA
Re: Carbon Stars new [Re: old_frankland]
      #6232372 - 12/03/13 10:35 PM

Cool spectroscopy stuff. Not what I am planning, but interesting.

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old_frankland
Carpal Tunnel


Reged: 03/28/05

Loc: San Francisco Bay Area
Re: Carbon Stars new [Re: Doc Willie]
      #6233205 - 12/04/13 12:26 PM

Quote:

Cool spectroscopy stuff. Not what I am planning, but interesting.




A few years ago I would have said the very same thing....


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JimK
Skygazer
*****

Reged: 09/18/05

Loc: Albuquerque, NM USA
Re: Carbon Stars new [Re: Doc Willie]
      #6233851 - 12/04/13 05:50 PM

Having recently completed the AL Carbon Star program, I can say that you will probably learn much about the multiple IDs/numbers for stars, locations throughout the heavens, and how to describe colors. I am sure that I learned a lot.

As for printed atlases, I found that not every atlas is suited for the task:

the Sky & Telescope Pocket Sky Atlas contained only 57 of the AL carbon stars (and 3 of those were not labeled)

Taki's 8.5 Magnitude Star Atlas (here) contained only 79 of the AL carbon stars (and 15 of those were not labeled)

J.R Torres' TriAtlas 2nd edition in Z-size (i.e., BC) contained all 100 of them, but 32 were not labeled.
(originally here: http://www.uv.es/jrtorres/triatlas.html,
but recently located here: http://www.volpetta.com/risorse/atlanti.html)

A good star program (such as SkyTools 3) should have all of them, but the identification nomenclature will vary (SAO, HD, NSV, GSC, Vnnnn) in addition to the conventional LETTER and constellation that is used for many. Wading through the various star ID translations can be a good learning experience.

Preparation is an excellent idea -- I used "arrow flags" (as typically used for "Sign Here" thin plastic markers with "Post-It Note"-type adhesive) on my charts to make it easier to find the carbon stars as I star-hopped around the sky (no computer or setting circles for me).

My adventure or quest for 100 carbon stars was completed about a year ago using a 3.5-inch Maksutov telescope. For the most part, only one eyepiece giving about 70x was needed (a couple of faint stars in Aur required a shorter focal length/more magnification to bring them out of the background sky). Overall, I had 24 observing sessions amounting to about 36 hours of observing time for these 100 carbon stars over a five-month period.

I learned how hard it was to describe star colors given the fact that they are generally so lightly saturated (~10%), and for descriptions decided to use the basics of brightness {very bright, bright, somewhat bright, faint, very faint}, hue (primary, prefaced with any secondary, such as orangey-red or yellowish-orange, or even "colorless" for some), and saturation if the color seems "pure" (to better quantify the amount of mixing with white, as in deep red or pale yellow as needed) -- thanks to information posted by Bruce MacEvoy (on the web and as droller on CN).

Good luck on your adventure -- and try to persevere!


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Astrodj
professor emeritus
*****

Reged: 08/24/11

Loc: Missouri
Re: Carbon Stars new [Re: Doc Willie]
      #6234578 - 12/05/13 01:39 AM

Hey Doc Willie,

Try these charts out...

AL Carbon Star List Charts

Enjoy!


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zvaragabor
member


Reged: 01/25/11

Re: Carbon Stars new [Re: Astrodj]
      #6234641 - 12/05/13 03:42 AM

I don't really understand. These Carbon are stars LPV stars. They change their brightness in time. So when they are close to or at their minima, one can barely see its color. And why not estimate brightness? Also, the AL Carbon Star List Charts gives a fix magnitude for each star.

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Rich (RLTYS)Moderator
Postmaster
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Reged: 12/18/04

Loc: New York (Long Island)
Re: Carbon Stars new [Re: zvaragabor]
      #6234695 - 12/05/13 05:51 AM

Not all carbon stars listed are variables. When I did the Carbon Star Program I'd estimate the magnitude of those stars that were considered variable as part of the description. Plot and use AAVSO Charts for these stars and submit your observations to the AAVSO.

Rich (RLTYS)


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NJScope
sage
*****

Reged: 03/08/04

Loc: NJ
Re: Carbon Stars new [Re: Doc Willie]
      #6235151 - 12/05/13 11:07 AM

Doc Willie:

I put together a pre-built list of carbon stars many years ago for use with Nexstar Observer List. Hopefully you will be able to use NSOL with your NexStar8 SE. If not, just PM me and I can provide the seasonal lists in *.csv (Excel) format.


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Astrodj
professor emeritus
*****

Reged: 08/24/11

Loc: Missouri
Re: Carbon Stars new [Re: zvaragabor]
      #6235782 - 12/05/13 04:59 PM

"I don't really understand. These Carbon are stars LPV stars. They change their brightness in time... Also, the AL Carbon Star List Charts gives a fix magnitude for each star."

The finder charts I linked to are just that, finder charts. Like Rich referenced, the AAVSO website is the place to go if you want to see the latest magnitude estimates and or create magnitude comparison charts for estimating the current magnitude yourself. Armed with these data, the finder pdf's I referenced are handy for completing the AL Carbon Star program.

"So when they are close to or at their minima, one can barely see its color."

I often find the opposite to be true, as do others. As an example, earlier this summer a fellow named Preston who posts here commented on the blood red color of S Aurigae which was near minimum at the time, I think magnitude 12 or so. It varies from 8 to 13 (or less maybe, can't remember off the top of my head). I observed it a few nights later and agreed; a startlingly deep red color near minimum.

That said, a host of variables (no pun intended) affect color perception of carbon stars. I don't worry too much about it, I just enjoy observing them.


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The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
Re: Carbon Stars new [Re: Astrodj]
      #6236310 - 12/05/13 09:59 PM

I'm almost done with the AL list. Observed most of them with 82mm mounted binoculars.
Several were too faint for small aperture so I got those with 18" dob.
Most of the stars were obvious carbons, but there are a couple that lack strong color.
One project I did years ago was compile a list of red stars in Skytools, using a B-V of +3 or higher.


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dan777
scholastic sledgehammer
*****

Reged: 11/16/07

Loc: Indiana
Re: Carbon Stars new [Re: The Ardent]
      #6237457 - 12/06/13 01:55 PM

If you want to see a dark red one now, check out S Cep (SAO 10100). It's small but deep red every time I've looked at it over the past three years (B-V 4.1).

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MtnGoat
Carpal Tunnel
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Reged: 02/18/07

Loc: Columbia Gorge, WA
Re: Carbon Stars new [Re: dan777]
      #6237534 - 12/06/13 02:36 PM

That's a good tip, thanks Dan!

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Rachal
super member
*****

Reged: 04/07/09

Loc: Alexandria LA
Re: Carbon Stars new [Re: dan777]
      #6237860 - 12/06/13 06:09 PM

Quote:

If you want to see a dark red one now, check out S Cep (SAO 10100). It's small but deep red every time I've looked at it over the past three years (B-V 4.1).


Dan, Have you ever taken a look at UU Aurigae(SAO 59280)? It's about 5.4 magnitude. I've never seen a redder star.

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dan777
scholastic sledgehammer
*****

Reged: 11/16/07

Loc: Indiana
Re: Carbon Stars new [Re: Rachal]
      #6238122 - 12/06/13 09:08 PM

The last time I looked at UU Aur was last January and my notes say "bright yellow-orange." I'll have to take another look at it.

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Rachal
super member
*****

Reged: 04/07/09

Loc: Alexandria LA
Re: Carbon Stars new [Re: dan777]
      #6238376 - 12/07/13 12:28 AM

It's been much longer than that since I looked at it, so I'll have to take another look myself. I "think" I was using an 8" F7 reflector, but I'm not sure.

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zvaragabor
member


Reged: 01/25/11

Re: Carbon Stars new [Re: Rachal]
      #6238576 - 12/07/13 07:09 AM

Rich, Astrodj, that makes sense, thanks! The AL Carbon Star List Charts confused me, as it gives fix magnitudes, not magnitude ranges.
I have my own list of variables to observe, and some are listed in the AL Carbon Star List as well. I submit my observations to AAVSO. Variable star observing is fun, and I aggree, that deep red stars are the most beautiful.


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sound chaser
member
*****

Reged: 01/13/13

Loc: France
Re: Carbon Stars new [Re: zvaragabor]
      #6239021 - 12/07/13 12:50 PM

VX Andromeda is well placed, it's an semi-regular that varies between around 7.5 - 9.5, visually deep red.

Doug.


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Doc Willie
Carpal Tunnel
*****

Reged: 03/31/10

Loc: Mid-Hudson Valley, NY, USA
Re: Carbon Stars new [Re: sound chaser]
      #6242590 - 12/09/13 12:45 PM

Thanks for all the suggestions. Unfortunately they are useless unless you can tell be how to see them through clouds.

I was wondering about how to handle the brightness of variables. The above discussion is quite helpful.


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Dave Mitsky
Postmaster
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Reged: 04/08/02

Loc: PA, USA, Planet Earth
Re: Carbon Stars new [Re: Rachal]
      #6243153 - 12/09/13 05:13 PM

Quote:

Quote:

If you want to see a dark red one now, check out S Cep (SAO 10100). It's small but deep red every time I've looked at it over the past three years (B-V 4.1).


Dan, Have you ever taken a look at UU Aurigae(SAO 59280)? It's about 5.4 magnitude. I've never seen a redder star.




To the best of my knowledge, the carbon star with the greatest color index (B-V index of +5.8) is EsB 365 or DY Crucis, which I observed during my trips to Bolivia.

http://www.pbase.com/takman2/image/76996595/original%20EsB%20365

Dave Mitsky


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