The Double Double

[avtaram]

Last night I was having look at the double double and noticed the one companion of each of the doubles is blue white and the other yellow.

I've observed these many times before but always semed as if all four were yellow if my memory serves me right. I had not made any notes before.

Has anyone else noticed this.

Avtar

[Qualia]

It's been a while since I've returned to these with the 4" but I did find significant colour in the 'Other Double Double' but not so much from Epsilon Lyrae. Here are a couple of sketches to indicate what was seen with a small frac from inner city last year:

Epsilon Lyrae

Struve 2470 & 2474

[lunator]

I have never seen a strong colour in the double double. Always been white to my eyes.

It could be the combination of the conditions and scope.

I will have a look with my ST120 and see if that gives a colour.

Cheers

Ian

[acey]

Always looked white to me too, which may be down to my eyes and scope, but seems to tally with most descriptions.

[avtaram]

Last night I was having look at the double double and noticed the one companion of each of the doubles is blue white and the other yellow.

I've observed these many times before but always semed as if all four were yellow if my memory serves me right. I had not made any notes before.

Has anyone else noticed this.

Avtar

Just looked up the double double in Burnham's Celestial Handbook.

In the book it states that modern obervers generally find all four stars to be simply "white". Struve, however, found the components of Epsilon 1 to be "greenish-white and bluish-white" while Herschel thought the fainter star inclined toward a "red tint" ; this was also the impression of Admiral Smyth who reported them as "yellow and ruddy".

So different opinions.

Avtar

[acey]

I was just looking up Smyth's description to see what he says: A yellow, B ruddy, C and D both white. Between the pair, he says, are "three small stars forming a curve to the south, the two smallest being Herschel's 'debilissima' couple, of the 13th magnitude, having an angle 220 degrees, and about 45 arcseconds apart". Given that the double-double is such an easy test for small scopes, maybe the "debilissima" pair (whatever that means) would be a worthier challenge - Smyth saw them with his 6-inch refractor.

See page 540:

http://archive.org/stream/cycleofcelestial031506mbp#page/n5/mode/2up

Edit:

I've also just had a look at Webb's Celestial Objects For Common Telescopes, which is very interesting on the Double-Double. Webb says epsilon Lyrae can be seen as double with the naked eye, and gives colours "greenish white; bluish white; yellow; tawny or rose coloured". More interesting, though, is that Webb says he has seen the "debilissima" pair with a refractor of aperture 3.7 inches, "an aperture for which they are excellent tests". I suspect this has subsequently been misquoted as saying that the double-double is the excellent test. Webb gives a diagram of the double-double including these intervening stars (marked 125, 120, i.e. they are of magnitude 12.5 and 12.0). He says that one observer (Ward) saw them with a 2.125-inch refractor "in very fine air".

See pp. 167-168:

http://archive.org/stream/celestialobjects02webbrich#page/166/mode/2up

My suspicion is that everyone has been concentrating on the wrong test - the thing to look for is those faint stars between the double-double, which John Herschel called "debilissima".

Edit:

This 1880 article summarizes the history of the epsilon Lyrae group:

http://articles.adsabs.harvard.edu/full/1880Obs.....3..637P

It seems to have had a similar fascination for 19th century observers as the Trapezium in Orion, so could be equally appealing as a modern observing challenge. The article has a detailed chart (p639) where the "debilissima" pair are labelled F and G.

[chiltonstar]

They look white at low mag to me: at higher mag, they do appear to be slightly different colours, but I took that to be just a low-light effect (ie the eye has a different spectral response at low flux levels).

When I've imaged them, they all appear fairly white I would say, eg:-

Chris

[Stu]

Yep, always looked pretty much white to my eyes at whichever magnification I'm using

Stu

[acey]

Can no longer edit above so am adding this:

John Herschel wrote in the observing notes "Debilissima inter 4 (epsilon) and 5 Lyrae" which I think is Latin for "Extremely faint - between 4 and 5 Lyrae", hence the subsequent nickname.

[Rockrae78]

I haven't ever been able to resolve the double double... do you have any tips?

[avtaram]

I was just looking up Smyth's description to see what he says: A yellow, B ruddy, C and D both white. Between the pair, he says, are "three small stars forming a curve to the south, the two smallest being Herschel's 'debilissima' couple, of the 13th magnitude, having an angle 220 degrees, and about 45 arcseconds apart". Given that the double-double is such an easy test for small scopes, maybe the "debilissima" pair (whatever that means) would be a worthier challenge - Smyth saw them with his 6-inch refractor.

See page 540:

http://archive.org/stream/cycleofcelestial031506mbp#page/n5/mode/2up

Edit:

I've also just had a look at Webb's Celestial Objects For Common Telescopes, which is very interesting on the Double-Double. Webb says epsilon Lyrae can be seen as double with the naked eye, and gives colours "greenish white; bluish white; yellow; tawny or rose coloured". More interesting, though, is that Webb says he has seen the "debilissima" pair with a refractor of aperture 3.7 inches, "an aperture for which they are excellent tests". I suspect this has subsequently been misquoted as saying that the double-double is the excellent test. Webb gives a diagram of the double-double including these intervening stars (marked 125, 120, i.e. they are of magnitude 12.5 and 12.0). He says that one observer (Ward) saw them with a 2.125-inch refractor "in very fine air".

See pp. 167-168:

http://archive.org/stream/celestialobjects02webbrich#page/166/mode/2up

My suspicion is that everyone has been concentrating on the wrong test - the thing to look for is those faint stars between the double-double, which John Herschel called "debilissima".

Edit:

This 1880 article summarizes the history of the epsilon Lyrae group:

http://articles.adsabs.harvard.edu/full/1880Obs.....3..637P

It seems to have had a similar fascination for 19th century observers as the Trapezium in Orion, so could be equally appealing as a modern observing challenge. The article has a detailed chart (p639) where the "debilissima" pair are labelled F and G.

I saw one very faint star almost half way between and slightly to the north of ε1 and ε2. This was at a magnification of 253 using the Baader zoom at 8mm with the Baader 2.25 Barlow.

I couldn't make out any other stars nearby.

Avtar

[coulthamst]

I haven't ever been able to resolve the double double... do you have any tips?

Looking at the equipment you have, you may need a little more magniffication. I observe from inner city Leeds, and find that around 200 times is required. I managed it with a SW 80 f5 refractor from this light polluted site. A decent 6mm eyepiece and your Barlow should suffice.

[alan potts]

I wa looking at this last night in excellent conditions and I have to say I only see them as white, I was using my M/N 190 mm and a magnification of x125 with the 8mm E.

Alan

[avtaram]

Heres a sketch I did last night.

[Rockrae78]

Looking at the equipment you have, you may need a little more magniffication. I observe from inner city Leeds, and find that around 200 times is required. I managed it with a SW 80 f5 refractor from this light polluted site. A decent 6mm eyepiece and your Barlow should suffice.

Cheers for this... OH is not going to be happy if I buy another EP! Oh well.... I wont tell him if you don't! 

[Stu]

Looking at the equipment you have, you may need a little more magniffication. I observe from inner city Leeds, and find that around 200 times is required. I managed it with a SW 80 f5 refractor from this light polluted site. A decent 6mm eyepiece and your Barlow should suffice.

Are you talking about the CPC800 or am I reading this wrong? 3mm will give huge magnification in that...?

It's as much about cooling, collimation and seeing conditions as anything else.

I've seen it quite easily in a 66mm refractor at under x100, and around x80 ish in a 106mm.

Stu

[Moonshane]

I see three of them as whitish and one of them as less whitish. to my eyes there's definitely one star that looks less 'clean' than the others.

[coulthamst]

Are you talking about the CPC800 or am I reading this wrong? 3mm will give huge magnification in that...?

It's as much about cooling, collimation and seeing conditions as anything else.

I've seen it quite easily in a 66mm refractor at under x100, and around x80 ish in a 106mm.

Stu

Oops! I was commenting on the Nexstar 130, you are quite right BigMakStutov.

[Rockrae78]

I've tried it with both scopes... and to no avail.  Used the highest power EPs with both too.... for the SLT 130 - used 8mm with Barlow and could clearly see 2 stars, but couldn't resolve it into 2 doubles... for the CPC 800 used 6mm Plossl (w/out Barlow), which is pushing the max useful mag., and all I could see was some fuzzy stars.

I have tried from both my fairly light polluted back garden, and more recently from the Brecon Beacons (although I only had the 8mm EP with me there - again w/out Barlow) and still no luck.  

I have tried using a Barlow with the CPC 800, but I just don't feel as though I get as crisp views so generally tend not to bother with a Barlow with this scope. 

Its not just that I can't resolve it clearly either... every time I've tried, I get perfectly round stars - not even funny shaped ones that would suggest a double.  Tried with both 1.25" and 2" inch EPs too.  Makes no difference.  Will keep trying, but I'm finding it very frustrating! 

[Moonshane]

are you sure you are on the right double?

[Rockrae78]

Yep... definitely the right double. 

[Stu]

I've tried it with both scopes... and to no avail. Used the highest power EPs with both too.... for the SLT 130 - used 8mm with Barlow and could clearly see 2 stars, but couldn't resolve it into 2 doubles... for the CPC 800 used 6mm Plossl (w/out Barlow), which is pushing the max useful mag., and all I could see was some fuzzy stars.

I have tried from both my fairly light polluted back garden, and more recently from the Brecon Beacons (although I only had the 8mm EP with me there - again w/out Barlow) and still no luck.

I have tried using a Barlow with the CPC 800, but I just don't feel as though I get as crisp views so generally tend not to bother with a Barlow with this scope.

Its not just that I can't resolve it clearly either... every time I've tried, I get perfectly round stars - not even funny shaped ones that would suggest a double. Tried with both 1.25" and 2" inch EPs too. Makes no difference. Will keep trying, but I'm finding it very frustrating!

That's a bit strange...LP shouldn't really make much difference, if you can see them then you should be able to split them. Even if conditions aren't great, you should see a peanut shape to them. 8mm in the CPC800 is around x250 which is plenty of power, shouldn't need any more.

Not sure what to recommend, although Shane's question popped into my head too!

Stu

[Rockrae78]

Definitely, definitely in the right place... checked, checked, rechecked, then checked again... even had other people looking at star parties to confirm I'm in the right place. Obviously must be doing something wrong, but I don't know what.

[Moonshane]

are you at PSP? you will see it there for sure even if I have to show you it myself  once you see it you'll wonder how you missed it.

[Rockrae78]

Yes, going to PSP... would appreciate the help with this one... So far, its the only thing I've not been able to get, but should be able to get(if that makes sense!).