Albireo v Almach

[Ags]

I was comparing Almach (Gamma Andromedae) to Albireo last night whilst waiting for Jupiter to climb a bit higher. I've always found Albireo to be quite subtly colored, so I was surprised when I looked at Almach (for the first time) and saw a really strong blue-yellow color contrast. I did not expect the color difference to be stronger than Albireo but it definitely is.

On that subject, if my notes are correct, the color contrast on 24 Coma Berenices (blue-orange) was also better than Albireo. (EDIT: I was looking at 24 Coma in mid-May, in case there is any confusion! No my telescope can't see round corners, lol.)

I wonder why the blue companion is usually the fainter one. Is it because it has not yet evolved to a giant phase?

http://stars.astro.illinois.edu/sow/almach.html

[albedo0.39]

Hey - that's a good catch - I'll deffo be targeting these objects next time the 'scope goes out..

Cheers

[Breakintheclouds]

Almach is a great double, really pretty.

Albireo's colour always seems to vary a lot and I guess it's affected quite a lot by the specific eyepieces and so on. I viewed it with a Hyperion EP a couple of night ago and like you, just didn't get any real hit from the colours. But when I viewed it at a friend's house recently with a bog-standard Skywatcher EP, there was a real 'wow' from the colour contrast.

[Ags]

Albedo, I was looking at 24 Coma a few months ago btw - don't think you can see it at the moment. Sorry for the confusion. Almach is pretty bright (as you'd expect for a named star) so it's very easy to find. I didn't even need my goto - it was less hassle just pointing the scope at it, rather than searching through a slow-scrolling double star database on the handset.

Breakintheclouds, I have seen more color on Albireo on other nights - only once did it have truly strong color, and that was when observing through thin cloud oddly enough. I thought the Almach - Albireo comparison was fair as it was the same night, same scope and same EPs.

[Breakintheclouds]

Now you mention it, I also used the same scope and EPs on the same night for the two on Friday. So yes, I'd agree with you that Almach is probably more impressive. Perhaps it'll take over as my double star of choice for impressing people!

[Ags]

Great minds - the reason I was thinking about this is because I've been showing casual observers Albireo as the 'best' double, because that's what I've read and heard to be the case. I think I will change to Almach now for these demos.

[Mikea]

What scope were you using Ags?

[lunator]

Hi Ags

I have found that Albireo looks best at lower magnification in a smaller scope, you get a nice colour contrast and a rich background of stars.

Almach looks better in a larger scope as it retains it;s colour contrast.

My opinion on this is that Albireo is a wide pair, and in larger scopes with a longer focal length in general the higher mags you get with any eyepiece makes the pair too wide and you lose the 'impact'

Cheers

Ian

[Ags]

Mikea, I'm using a 102mm Mak (f13) - I was looking at the doubles at 50x and 150x.

[Mikea]

OK - thanks! I'm considering adding a refractor to my current collection (of 1!) to improve doubles viewing. With Christmas looming, I think I deserve a treat...

[Vega]

Would using different magnifications have an effect on the visual contrast?. Almach is a much tighter double and I always use a higher magnification on it. Also... I find the closer the stars look visually in the eyepeice, the more impressive the contrast will look.

Both these doubles are real gems, but for me Alberio is king. I know its a cliche, but cliche's are just that for a reason I guess.

:-)

[moflaher]

For some reason, almach is more pleasing than albireo for my eyes.

[michael.h.f.wilkinson]

I like both doubles. Albireo is brighter, but Almach has the edge colour-wise. Given that the amount of light emitted per unit of surface area rises with the 4 power of the temperature, the orange components must have a much larger surface area to equal the brightness of the blue component. Assuming 3200 K (M-type) for the orange, and 20,000 K (B-type) for the blue, the difference is a factor of 1,500 in surface area (to reach equal magnitude). Even if the orange component is 4,000 K (K-type), the surface area ratio in 625 for equality in brightness. In terms of radius, these values become 39 and 25 times, respectively. So if the blue is fainter, the orange must be a giant or supergiant.

[Adacas]

My two favorite doubles!