Article: 110 Southern Sky Doubles

[iceman (Mike)]

Stephen Saber (saberscorpx) has written an article listing 110 Southern Sky Doubles.

You can read the article on the IceInSpace Projects & Articles page, or directly by clicking on the link below:

110 Southern Sky Doubles

Thanks to Stephen for writing the article. If you'd like to contribute a review, article or other content to IceInSpace, please contact me.

This is quite a disappointing list of double stars which has far too many errors, and much of the information that is very out-of-date.

I don't know where you got your information from, but I do suggest you toss it out for something better and more modern!

There are far too many example of corections here, but the important ones are;

- p Eridani / p Eri : The prefix for this star is a lower case "p", and is catalogued as DUN 5. Separation is 10.5 arcsec along PA (Position angle) 190 deg (2002) The 9.6 arcsec is ancient, being made by Worley in 1948 (nearly 60 years ago!!). Magnitudes are the brighter 5.8 and 5.9.

- Gamma Crucis (DUN 124) is listed as having a separation of 10.6 arcsec, when in fact the separation is more like 125.2 arcsec along PA 27 deg (2002). The error is likely in the decimal place, making 106 arcsec, and this derives from Innes in the 100 years ago! The magnitudes here are closer 1.8 and 6.5 - the 1.6 given seemingly the combined visual magnitude and NOT individual ones.

- Mu Crucis (DUN 126) current separation is 34.8 arcsec PA 18 deg (2002)

- Epsilion Cha (HJ 4486), is given as 0.9 arsec. In fact, this star has closed down to 0.4 arcsec (1997), and is currently impossible through most amateur telescopes. The PA is 211 deg . Hartung claims this is visible in 15cm in Astronomical Objects for Southern Telescopes, when the separations were close to 0.9 arcsec. (Positions are 11h 59.6m -78 deg 13')

- Mu Velorum / R 155 is a known binary whose current separation is 2.6 arcsec along PA 55 deg.

- 4 Centauri is H N 51 Separation is 14.8 arcsec along PA 185 deg (1998)

- Alpha Centauri is RHD 1 (Richard 1). The 2006 and 2007 separations are 9.1 and 8.3 arcsec, respectively, with PA's of 237 and 241 deg.

- Gamma Centauri is HJ 4539 is a binary star. This is at the moment near impossible to see, whose separation is 0.59 arcsec along PA 337 deg as of January 2007. It was 1.0 arcsec in 2000, and will not be again 1.0 arcsec until at least 2030 AD. Currently impossible to see in most amateur till at least 2020!

- pi Lup is HJ 4728 Separation is 1.7 arcsec along PA 66 deg (2002)

- kappa lup is DUN 177 Separation is 26.1 along PA 143 deg (2002)

- mu lup is HJ 4753 Separation is 1.0 arcsec along PA 323 deg (1999)
The companion is DUN 180 AC 22.7 arcsec PA 127 (2002)

- xi Lup is PZ 4 ; Seperation is 10.4 arcsec along 49 deg (2002)

- eta Lup is RMK 21 ; Separation is 15.5 arcsec along PA 19 deg (2002)

- delta Aps is BSO 22 Separation is 103.3 arcsec along PA 10 deg (2000)

- HR 3260 is a star catalogue number. This is in fact RMK 8, whose magnitudes are actually 5.3 and 7.6, with the current separation of 3.6 arcsec along PA 67 degrees (2000) [NB : The actual position is 08h 15.3 -62 deg 55' ]

- HR 4179 is a star catalogue number. This is in fact GLI 152, being 6.2 and 8.0 magnitude being separated by 26.3 arcsec along PA 67 deg. Although the primary is a orangry-red M1III star, this is one is among many other candidates one could have selected.

- HR 4423 is a star catalogue number. This is in fact BSO 6, discovered by Dunlop but taken from the Paramatta Star Catalogue. These are 13.1 arcsec apart 168 deg , and whose magnitudes are 5.1 and 7.4. [Positions are; 11h 28.6m -42 deg 40']

- HR 4628 is a star catalogue number. This is in fact JC 17. These are separated by 3.2 arcsec along PA 17 deg (Last measure 2000) (The position for this is 12h 10.0m and -32 deg 42')

- HR 5520 is a star catalogue number. This is in fact I 236, whose latest measure is 2.2 arcsec along PA 90 deg. This is a notoriously difficult star to resolve, and although bright, the difference in magnitude requires at least 20cm to 25cm to split. The magnitudes are closer to 5.9 and 7.6, than the 5.5 and 8.5 in the table. (The more precise position is 14h 53.2m -73 deg 11')

- HR 6416 is a star catalogue number. This is in fact BSO 13 AB or 44 Ara, whose separation is currently 9.2 arcsec along PA 256 deg (2002). (Not anywhere near 4.3 arsec in the list - which is Innes position 100 years ago!). It is also a known high proper motion star. (The position is 17h 19.1m -46 deg 39')

- HR 8202 is a star catalogue number. This is in fact MLO 6 AB, whose latest position is 2.9 arcsec along PA 150 deg. This is a very difficult pair, because of the magnitude difference. Magnitudes are actually closer to 5.6 and 8.2 - differing slightly from these tabled results. (Positions are 21h 27.0 -42 deg 33')

Many other do need additional modifications.

***************************

I strongly suggest, you should go to the Washington Double Star Catalogue Site and download the latest whole catalogue, which is continuouly updated. This is 13.2 Mb in size) This is downloadable from the US Naval Observatory Site at;
http://ad.usno.navy.mil/wds/wdstext.html

The recent "standard" version has just been released (WDS2006.5), and should really be used when quoting information. (This is 13.2 Mb in size and contains c.102 000 of pairs.) This can be obtained at;
http://ad.usno.navy.mil/wds/wds2006.5.htm

You should also download the 1.3Mb Notes file, which has additional information;
http://ad.usno.navy.mil/wds/wdsnewnotes_main.txt

and the Format file ;
http://ad.usno.navy.mil/wds/wdsweb_format.txt

Those with known orbits Ie. p Eridani, Mu Velorum, Alpha Centauri and Gamma Centauri, etc., the ephemeris for this is at;
http://ad.usno.navy.mil/wds/orb6/orb6ephem.html

UNSUITABLE PAIRS

The selection includes a five very difficult pairs, including;
Epsilon Chameleon, B Vel, Gamma Centauri, Upsilon Grucis, Theta Grucis.

None of these are readily visible except in 30cm or greater.

SOME MISSING PAIRS

Also missing from this list are real great pairs like;

Beta Crucis / DUN 125, which is a wide double with the crimson variable star EsB 365. Separation is 373 arcsec (along PA 23 deg, whose magnitudes are 1.3 and 7.2, respectively. This is one of the better pairs for southern amateurs, especially due to the colour contrast.

DUN 74 / b[SUB]2[/SUB] Carina (4.9, 6.6 ; 40 arcsec PA 74 deg )

DUN 81 in Carina (5.8, 7.9 ; 5.4 arcsec PA 240 deg )

J Cen / DUN 133 in Centaurus (4.5, 6.2; 61.7 arcsec PA 343 deg )

x Velorum / DUN 95 AB - HJ 4341 BC 51.8 arcsec PA 106 deg, which is also a multiple. This missing pair is one of the Top 10 pairs in the sky, and one of the most colourful, being orange-yellow and pale blue.

J Vel / RMK 13 is a triple star; (4.5, 8.2, 9.8; 7.2, 37 arcsec; PA 102,102 deg

SUGGESTED UPDATES

What also should be added to the whole list is the;

- the position angles
- A catalogue number for all systems
- more precise positions (ie hh mm.m and dd mm), matching the 2000 Washington
Double Star Catalogue (WDS) designations.

In the meantime, those who must use this list should do so with MUCH CAUTION!

[iceman (Mike)]

Thanks for the post ariane - I'm sure the OP will read the information and hopefully update the list.

In the meantime, it sounds like a great article could be written with your knowledge? (hint hint )

[GeoffW1 (Geoff)]

Gee Ariane,

I think Mike is being very tolerant here. As for myself, as a timid newbie embarrassed at my all-round lack of knowledge, I'll be making sure I get nowhere near you at any IIS Astrocamp.

I thought your response was a nasty self-indulgent putdown, and a shock after reading all the friendly supportive posts in this community.

Couldn't you have put it more diplomatically?

Cheers

Geoff

Geoff

Sorry that you feel this way. I also was once a "newbie", so I probably can understand you view point here, but the expression I have given was I think without malice or putdown - as you say.

I really do think Stephen Saber has produced a very good list of pairs, with about 80% being ones I would consider suitable candidates. However, it is imperative that if information is going to be presented as a astronomical guide, it must be correct as possible. If one was to begin to observe southern double stars it is important that those with smallish telescopes are not infrequently disappointed - else they will not explore the many wonders of their own hobby. There are a number of pairs in this list which I have attempted - even with a very sizeable aperture - to observe over the years but have never quite resolved them adequately.

All quoted double star values and tables are notoriously problematic, because they are often well out-of-date before they are published. Deep-sky objects never really change over ones lifetime. The true beauty of doubles is that they do change - and sometimes quite significantly. One has only to look at Alpha Centauri, which in the 1980's was visible even in small telescopes. Today it is rapidly closing, where small telescopes will have difficulties splitting the famous duo.

Shouldn't people that might become interested in observing doubles have information that will help them learn about their hobby?

As you say, perhaps my diplomacy could have been better placed, and if I have offended you, then I wholeheartedly give my apology.

All

I am prepared to submit the corrected information for Steven Saber's list selected pairs, which I will directly submit to the moderator off-line.

Ie. This will be as;

*********************************** ****************************
Pair WDS RA Dec. Mags Sep PA
Name Cat.No. Sys. Con mm ss.s o ' A B " o Year Map No.
*********************************** ****************************
beta Tuc LCL 119 AC Tuc 00 31.5 -62 57 4.3 4.5 26.6 168 2002 SA 24
*********************************** ****************************

Steven and Mike can use it as they wish!

[iceman (Mike)]

Ariane thanks for your updated list. I agree that astronomical lists need to be correct and accurate for them to be any use to observers.

I'll update the site after the new year.

[saberscorpx]

All suggestions, revisions, and additions are always welcome.
Sources and IDs vary. Preferences vary.

Just wanted to get the DS ball rolling.

Thanks for the input,
Stephen

Steven,

Your statement here concerns me very much.

"Sources and IDs vary. Preferences vary."

Firstly, "Sources and ID's vary".

In this case, No they don't.

The fundamental standardised source is collated within the WDS (Washington Double Star) Catalogue. There is no other data available that is not either second-hand, third-hand or later. All positional values and ID's are simply standardised - being already fixed in rigid terms of name, position and terminology. These have been determined by the IAU Commission 26 for Double Stars - by international decree - and are made to avail us of the problem of misunderstandings or wrong identification.

If you want to be pedantic, all astronomical works that are either as written or as observed and recorded, MUST always be properly re-sourced and acknowledged.

Whilst you are correct stating that "Preferences vary" - based on some criteria the observers believe may or may not benefit other observers, there is no getting away with sticking to standard sources. If you have differences, you must say why.

Again though I may seem very harsh in my opinions here, there is good reason for it. Unless amateur astronomers are willing to comply to reasonable standards concerning visual observations and suitable observing lists based on the best current data - the practice of observational astronomy will be no better than common here-say. Frankly, there is already too many distortions and errors in many of the commonly used references - where the observer has to sift through the chaff to find the truth.

Sorry. For double stars the current standard is based on the Washington Double Star Catalogue. There just are no other "standards".

Note: I would be very interested about your original source data.

[saberscorpx]

ariane-

ECO was the primary data source for the list:
http://astronomy.eaglecreekobservatory.org/doubles/

I have no problem with your tweaking the list to
WDS standards.

I also respect the conviction to accuracy (despite your inability
to correctly spell my name).

The SSD list was presented to be critiqued and hopefully
expanded on.


Thanks for the input,
Stephen

Saber Does The Stars At
http://www.astronomyblogs.com/member/saberscorpx/

[Dennis]

Hello, Stephen

Welcome to the forum and thanks for writing the article on double stars. I’ve not traditionally spent much time looking at these, but your article has now sparked my interest.

I suspect you invested a lot of time and energy in putting the list together – thanks for that. I note that you are from the USA – what inspired you to write about Southern Doubles?

I'll be sure to print the list and make my way through them - using GoTo of course!

Seasons greetings to you.

Dennis

[saberscorpx]

re: ...what inspired you to write about Southern Doubles?

Hi Dennis-

Several years ago I spent two weeks falling in love with the southern skies.
I'm still hooked.
Next visit I plan on tackling the best doubles as well.

We (up north) hear alot about the beautiful DSOs those down under enjoy, but not so much about the interesting splittable stellar light shows.
Creating a large 'starter' list for both residents and northern visitors benefits us all.

What better place to start one than IceInSpace?


Happy holidays,
Stephen

Saber Does The Stars at:
http://www.astronomyblogs.com/member/saberscorpx/

[ausastronomer (John Bambury)]

Originally Posted by ariane

SOME MISSING PAIRS

Also missing from this list are real great pairs like;

x Velorum / DUN 95 AB - HJ 4341 BC 51.8 arcsec PA 106 deg, which is also a multiple. This missing pair is one of the Top 10 pairs in the sky, and one of the most colourful, being orange-yellow and pale blue.

Yep, you're right, this is easily in the top 10 pairs in the sky. One of my favourites. Let's not forget that Hartung also left it out, so it's tough being critical of someone from Illinois USA for leaving it out.

CS-John B

[saberscorpx]

My apologies to xVel.
It is quite beautiful.
I passed right over it.
Anyone have a color shot handy?

I've updated the SSD list at my site, as well.

Personally, I'm not a fan of knowing the PA ahead of time.
Kind of a 'plot spoiler'.

As always, YMMV.


Saber Does The Stars at:
http://www.astronomyblogs.com/member/saberscorpx/

[ausastronomer (John Bambury)]

Originally Posted by saberscorpx

My apologies to xVel.
It is quite beautiful.
I passed right over it.
Anyone have a color shot handy?
Saber Does The Stars at:
http://www.astronomyblogs.com/member/saberscorpx/

I actually selected and wrote this target up in May last year as part of our monthly observing challenge. Here is a reference to my commentary on it.

http://www.iceinspace.com.au/index.p...69,198,0,0,1,0

Here is an image of it taken by one of our forum members, Narayan (Seeker)

CS-John B

[glenc (Glen)]

Thanks for the list Stephen.
Another source is:
Hipparcos Input Catalogue, Version 2 (Turon+ 1993)
Double and Multiple System Components (32290 rows)
http://cdsweb.u-strasbg.fr/viz-bin/VizieR?-source=I/196

[saberscorpx]

Albireo Australis suits it (them) well.

Thanks, guys.


Saber Does The Stars at:
http://www.astronomyblogs.com/member/saberscorpx/

Glen

A comment. The "Hipparcos Input Catalogue" as a source of double stars as referenced is also incorporated into the WDS Catalogue.

Unlike all other sources, the data in the WDS and the 6th Orbit catalogue is continuously updated - everyday in fact.

The Hipparcos satellite data is also flawed, mainly because those between about 2 arcsec and 0.8 arcsec are missing from the list. This was because of the design of the satellite itself, simply caused by the interferometric techniques employed.

"Another source is:
Hipparcos Input Catalogue, Version 2 (Turon+ 1993)
Double and Multiple System Components (32290 rows)
http://cdsweb.u-strasbg.fr/viz-bin/VizieR?-source=I/196

Furthermore, much of the data is actually centred around 1991 - now more than 15 years ago!

Stephen

Sorry. I did spell your name wrong. I have two Steven's in my extended family, so it was just a little slip-up in the differing versions of the name.

I was interested that you commented;

"Personally, I'm not a fan of knowing the PA ahead of time. Kind of a 'plot spoiler'."

In my own experience, the loss of this position angle data would not make a very useful list, as it removes the much needed data regarding real identification. Although the use of computer-aided positioning of telescopes is a huge advantage - the observer still need to make a positive identification of what he or she is observing. Whilst it might be not really be needed for visual observations, this remains important because it;

- Assists in not confusing the double stars from one another. Furthermore, it assists observers who don't know the orientation of the field. Those using Dobs or star diagonals - unless they are aligned to the local meridian, will find that the orientation will be jumbled anyway!

- With the borderline pairs, the resolution of the telescope will be either elongated in a particular direction or just appear single. If you don't know the direction of orientation, it assists identifying the correct pair - otherwise you may have a field of mostly single stars.

- It gives clues to the veracity of any the given PA and Separation at a particular date. Some systems can change very rapidly over a short period. This can be due to such things as a highly eccentric orbit, where apastron will seemingly be fixed for significant time followed by rapid change and reducing separations.

- Without the date of the last measure of the pair, the position angle (and separation) would be only an estimation anyway.

- Completely discards the historical adoption of "standard" observation methods used for the last 180 years. Ie. The observations position angle and separation through the decades or centuries are used to determine the attachment of stars as binaries or optical pairs.

(COMMENT : This sounds more like the adopted Americanised philosophy of the "Astronomy League" - AL. Although AL has admirable goals by presenting most the best objects for observers on a golden platter. In my opinion, it fails quite dismally in setting any astronomical understanding of the history or nature of many different objects.
Furthermore, the addition concern with all the Astronomy League lists - especially the double star ones - is that some of the data has been deliberately made incorrect - mainly to catch out those doing their observing lists. An extensive discussion of this appears within the S33 Double Star Yahoo! Group, where numbers of AL observers were questioning some of the tabulated observing lists for their own "projects".

For me, this approach paints a very biased and rose-coloured glasses picture of various observing methods and very much fails to generate the necessary critical thinking or understanding.)

[glenc (Glen)]

Thanks for the info on Hipparcos.

I like to look at difficult doubles first and then check the pa later to see if I did really see the faint secondary.

There is a list of Brisbane Observatory, Dunlop and Rumker doubles at:
http://www.iceinspace.com.au/forum/s...ad.php?t=15660