Welcome to the first instalment of my new project, Seeing Double. My aim here is to show people who are new to astronomy some of the great double/multiple stars we have in the sky and to give people something to look at while the moon is out drowning all the DSOs in its glorious (debatable) light.
We'll be looking at visual doubles, multiples and binaries of course so no special equipment (which is probably beyond us all anyhow) has to be used, just your telescope. I am hoping to do this on a monthly or bi-monthly basis depending on when I can get out doing constellation each month including 5-10 doubles drawing information from my own knowledge, various websites and a program called cartes du ciel.
Definition: I could have put this in my own words, but alas I am to lazy... so here is an excerpt from the Eagle Creek Observatory site in their doubles section...
Quote:
A "double star", or multiple star, is exactly that. It's a set of two or more stars that appear next to each other. There are two types of double or multiple stars. There are "true" binaries or multiples and "optical" binaries or multiples. True binaries or multiples are stars that are actually physically close and are bound together by gravity. Optical binaries or multiples are stars that are lined up just right so that the appear to be physically close.
Anyhow, enough dribble lets do some observing!
This months constellation is our very own Southern Cross (aka crux). Nestled between Centaurus and Musca (the fly) it is our great southern lands best known constellation and it holds a number of really nice double stars.
**note, colours mentioned are how they appeared to me and not necessarily their true colour**
1-Alpha Crux: well... if the cross was up the right way it would be the bottom star. This star is actually a multiple consisting of 3 parts, 2 bright stars close together and one dimmer star out from the rest. All 3 stars show as blue in my 8" newt. Stars A and B are mag1.25 and 1.55 and are 3.9” apart star C is mag 4.8
2-HJ 4524: a great little double near the edge of NGC 4439 (open cluster) consisting of a white star (A) and a yellow star (B). Star A is mag 8.05 and star B is 9.93 and separation is 30.3”. quite pretty next the the cluster really…
3-HJ 4547: marked on the map for your convenience a double of white and what looked like blue in my 8” scope. The 2 near stars could be mistaken for part of the double and look nice next to it. A is mag 4.72 and B is considerable dimmer at 10.24 but the split is easy due to the 28.1” separation.
4-Dun 117: It’s a triplet! Yup 3 stars in one. This group contains t whites and one dimmer blue. A and B are 7.40 and 7.83 respectively, C is 10.24 mag. Seperation of A and B is 27.7” its another easy split… I didn’t do any hard ones
5-BSO 8: put your hand up if you love yellow stars! We have to lovely yellow stars of similar magnitude here right next to NGC 4337. Their magnitudes are 7.84 and 7.98 with a separation of 5.2”… A lovely sight by any standards.
6-Gama Crux: did you know that 3 of the 4 points are doubles/multiples? Well Gama Crux is one of them. Three stars in this one and they are very purdy. A is white and 1.8 mag, B is blue and 6.45 mag, the bonus star C is 9.25 mag. This is practically for binos (except C is bit dim).
7- Beta Crux: another triple system and one I did not conquer, so I thought I’d put this in as an added bonus because of the blood red carbon star near by. A is 1.25 mag and B is 11.4 mag. Although the aren’t close (42.3”) the dimness of B makes it very hard to see… but hey, check out the carbon star anyway
Now get out there and search for them
Please feel free to reply here with any feedback, pics or reports of these objects… I want to know how you go
also tell if you want more of these and any changes to the format you could suggest.
This is fantastic! I'm looking forward to the next clear night to check them all out, thank you so much. Guides like this is really great for beginners like me! With all the thousands of objects out there I still get so caught up trying to figure out what to do with myself!
Here are 4 multiple stars I captured with my Vixen ED102mm f9 refractor, TeleVue x5 PowerMate, Vixen x2 Barlow using the Meade LPI CMOS digital camera.
Images were taken back in 2004.
Rigil Kentaurus and Acrux were captured using Vixen x2 Barlow.
Theta 1 Ori was captured using Televue x5 PowerMate.
Antares was captured using Televue x5 PowerMate and Vixen x2 Barlow stacked. The bright orange ring around Antares is the first diffraction ring resulting from the extremely high magnification used to capture the image.
Nice one Ving. Some great targets fairly close together. Makes life more easy not having to slew too far.
Nice work too Dennis. Is that nebulosity in Theti 1 Ori??
Hi Matt
Nebulosity - I wish! The Meade LPI max exposure is 16 secs, so what you are seeing there is.....poor seeing blobs, due to the relatively high magnification and longish (multi-second) exposures to help record the stars.
That's still good work Dennis. Especially with the LPI. It's not really intended for that purpose, is it?
Hi Matt
Yes, you're right there, it's more for the Moon, Planets and Sunspots (with the necessary solar filters) although I have seen some fairly decent DSO's (Deep Sky Objects) posted by users with large aperture, fast dob's before Meade introduced the DSI for DSO's.
I posted this reply to a thread on eyepieces but it really is a lot more appropriate here so I have duplicated it.
Quote:
Originally Posted by davidpretorius
there is another one i am chasing and i noticed it is now in the morning sky
gamma 2 delphini
orange / blue.
I really want to image this couple
David/Matt
Not sure if you guys were here when we had the "Monthly Observing Challenge". The files are still available and I have posted a link to them. I selected the double stars and did the write ups for them. If you haven't observed these doubles before they are all really nice. Several have a lovely colour contrast. If you're interested in Double/Multiple stars, these are worth observing now and in the coming months and suited to smaller/medium apertures. Here they all are with a link to the page contining the write ups:-
Another very nice double worth taking a look at which is currently nicely placed early evening is h3945 in Canis Major. This is a really nice bright yellow/blue double and not too dissimilar visually to X Velorum only it's not quite as bright being about Mag 4.5. It is about 2 degrees south of a nice open cluster in NGC 2362.
There are also 4 or 5 nice orange/blue doubles within about 3 degrees of X Velorum. Not as bright but still nice and easily separated at about 60X to 80 X with medium aperture. Not sure of their names (I think 1 is Dunlop 89) but they are easy to find by just panning in a line between Eta Carina and the Gem Cluster
CS-John B
Last edited by ausastronomer; 07-05-2006 at 09:55 AM.
I spent some time last night checking out doubles in Crux. I didn't have your list handy; I was working from the list produced by Eagle Creek Observatory (ECO), but there were some overlaps.
In relation to your list and commments:
Beta Crux: ECO just note there to be a double, but my notes read: "two candidates for secondary, 1 orange and 1 grey". I think I saw the triplet you refer to.
Gacrux: I saw the primary as yellow-white, and the secondary as blue-white. According to ECO, separation is 111", they are certainly a long way apart!
Dun117: I only saw primary and secondary, both a dull grey, not worth revisiting IMHO.
HJ4524: I agree it is in a lovely location near the OC. I saw the primary as white and the secondary as grey.
There are some other nice doubles in Crux also worth checking out that did not make it to your list:
Mu Crux: is a beautiful bright double, sep 34"
HIP 60557: located near OC NGC4337, this close double (sep 5.3") looks rather like two eye protruding from the OC, like eyes of an alligator, the OC being the body of said 'gator!
CP 12 (SAO 251919): A great test for seeing, your sight, and your scope, this is a faint double, with 1.9" separation. I managed a clean split with magnification at 450x, elongated at half that magnification.
COO 140: a close pair (4.9" separation), pale yellowish primary. Split easily at 135x.
BTW, I recommend any doubles fans to also check out delta Bootes. I would interested in what colours you see. It is a bit low on the northern horizon for me to be really confident on its constituent colours, but I see a yellow primary and a bluish secondary.
hi Rod, HIP 60557 is a different name for bso-8 in my list, I liked this one too
I wonder which contellation i should do next...
dun-117. I probably had less moon that you, so maybe thats why i saw the third star? It helped that I knew where it was in relation to A and B too (via cartes).
i used cartes du ceil mainly. it has a huge doubles database. this is also where i got the star names from. i also used WCO and s33, but that was after i had finished, it was meare coincidence that i picked doubles that were on thier lists. I used them just to see if there were any major doubles that i could have put in. I was pretty happy with what i found
Good reports guys, I do doubles sometime when thje sky is getting a bit brighter towards moonrise, and a bit bright for DSO's, it is quite an enjoyable interlude. By the way Rod and others did you join the Webb Society?
