Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

New Carbon Double Star in Andromeda

  • Please log in to reply
30 replies to this topic

#26 ssmith

ssmith

    Messenger

  • *****
  • Posts: 486
  • Joined: 28 Jun 2012
  • Loc: Colorado

Posted 11 November 2018 - 04:09 PM

Hi Aubrey -

 

Here is the SIMBAD data for NC 4 showing its other identifiers:

 

NC4 Simbad data.jpg

 

The 10.2 magnitude value is from SIMBAD and the 11.4 value is from Stephenson’s original paper.  I have no idea if this magnitude spread represents an actual variability of the Star or if it is just some measurement discrepancy between the two sources.

 

 

 

 


Edited by ssmith, 11 November 2018 - 04:50 PM.

  • flt158 likes this

#27 fred1871

fred1871

    Apollo

  • -----
  • Posts: 1293
  • Joined: 22 Mar 2009
  • Loc: Australia

Posted 11 November 2018 - 08:26 PM

Magnitudes depend on the waveband in which they're measured. The list of magnitudes (by waveband) in the Simbad page Steve Smith shows in #26 gives such a list: V magnitude 10.2, and much brighter in the various IR bands, J, H, K.

A magnitude of 11.4 could be a blue magnitude, a different V-band result, or an indication of variability. More data needed.

 

You'll notice that there's no Tycho designation listed by Simbad for this one. And it's not in the WDS, not too surprising given the faintish magnitudes and fairly wide separation, even before Proper Motion numbers show it as optical.

 

The best way to identify an object like this one is to give RA and DEC numbers, and indicate if they're J2000 or precessed to 2018. That way we can all readily locate the object being referred to.

 

Thanks, by the way, to James (jkwhinfrey) in #12 above for providing the Simbad link some time ago. After he provided that, there really wasn't any need for folk to be wandering around in hope of somehow finding/guessing the correct red/carbon star.


Edited by fred1871, 11 November 2018 - 08:27 PM.

  • flt158 likes this

#28 flt158

flt158

    Viking 1

  • -----
  • topic starter
  • Posts: 769
  • Joined: 11 Aug 2014
  • Loc: Dublin, Republic of Ireland

Posted 12 November 2018 - 02:03 PM

Whilst I agree with you, Fred, I get the feeling that there are many of us basic amateurs find both the Simbad and the Gaia pages greatly complex in their interpretation.

There is too much information in them for me to figure out. 

Of course that should not be the case for anyone. 

It would be very nice if someone could explain the basics for Simbad for a start. 

For instance -what do the abbreviations ICRS and FK4 coordinates stand for?   

Even though I do not doubt they are both 100% correct. 

 

However, having said all that,  I do also trust Steve's excellent image (#24) as absolute truth, and very helpful indeed. 

 

And I do thank you, Fred, for your contributions on this optical double.

 

Kindest regards from Aubrey. 



#29 fred1871

fred1871

    Apollo

  • -----
  • Posts: 1293
  • Joined: 22 Mar 2009
  • Loc: Australia

Posted 14 November 2018 - 07:23 PM

Aubrey, the Simbad page - as offered by Steve Smith - is not complex. If you look at the ICRS coord you'll see it's followed by (ep=J2000) - which tells you that the position listed is for epoch (year) 2000. Likewise, the FK4 co-ordinates are for epoch (year) 1950. Comparing the two also gives you the change due to precession in a 50 year period, ignoring very small differences in accuracy of the positions as measured. The long numbers listed shows these are high precision positions, beyond what any backyard observer needs for normal purposes.

 

Obviously as precession does not stop, the position for 2018 will be a bit different again : near-enough 18/50 of the 2000/1950 difference in the same direction. But if you're using common software for amateur observers, it usually defaults to the current date position, so you're not looking where the object was 18 years ago (J2000).

 

If you've found an object by star-hopping, or by chance, you can try using star maps for getting an approximate position; or if your mount is go-to or push-to or some version with digital setting circles, you can get a reading of the position, which will be roughly correct. Common mountings allow that; accuracy isn't pin-point, but a useful starting point. The mount I mostly use (from SkyWatcher) does move off precise accuracy, but using it puts known-position objects into a low-power field; if I want better accuracy I can compare the current RA and DEC numbers from a catalogue or list with the reading the software is giving, the object being centred (assuming a known object); that allows correction for a more accurate position reading in that part of the sky for objects I'm trying to identify.

 

It might sound complicated, but isn't: it's very easy and straightforward. And giving the position of an object, along with an idea of degree of accuracy, and adding other pointers you might have, allows quicker identification for you and others.


  • flt158 likes this

#30 ssmith

ssmith

    Messenger

  • *****
  • Posts: 486
  • Joined: 28 Jun 2012
  • Loc: Colorado

Posted Yesterday, 09:52 AM

Fred is right - SIMBAD and the ALADIN interface is a wonderful tool and one that every amateur should have at least a passing familiarity with.  It is what the Pros use and the ultimate tool for the armchair astronomer.

 

I have been using it for years and I have still have not plumbed the depth of its capabilities.

 

At its most basic it will give magnitudes and position of every star - far more than any planetarium app.

 

Magnitudes in almost every band imaginable not to mention spectral classes, proper motion etc.

 

It has every star catalog ever produced (And there are hundreds of them).

 

Click on a star and it will give you a bibliography and a link to every scholarly journal that has referenced that star.

 

You can do astrometric and photometric measures.

 

Huge catalog of photos in every spectral band.

 

Its capabilities go on and on ...

 

Best of all  ...  it’s on-line and free to use!


Edited by ssmith, Yesterday, 10:08 AM.

  • flt158 likes this

#31 flt158

flt158

    Viking 1

  • -----
  • topic starter
  • Posts: 769
  • Joined: 11 Aug 2014
  • Loc: Dublin, Republic of Ireland

Posted Yesterday, 01:10 PM

Thank you, Steve and Fred, for helping me and the rest of us out with Simbad. 

I reckon we can take it that the term Fluxes refers to the magnitudes through various bands. 

For example V means visual.

And that's why we know that C* 3223 has a magnitude of 10.2. 

It probably doesn't matter that I don't know what G, H, J and K mean. 

But to others it might. 

 

Kindest regards to both of you, from Aubrey. 




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics