A lovely triple for the late Summer........

[chiltonstar]

With near perfect seeing here last night (Oxford area), I had another look at some tough doubles and triples to see if I could resolve them better.

One that was absolutely stunning was iota Cas, which has a close double (mags 4.6, 6.9 ca. 2.5 arc secs apart - Cambridge DSA) and a more distant fainter star (mag 8.4, 7 arc secs from the primary). All three were well resolved last night as perfect airy disks, with the faintest star an intense blue colour. On previous occasions, I've only half-resolved the mag 6.9 star as a shimmering blob, but last night it was worth braving the mosquitos!

Scope: 5" Mak, mag x250.

Chris

[Moonshane]

I totally agree that this is a stunning double, one of my favourite systems. I use it as a guide to seeing and ca often split the three components readily with my 6" f11. I tend to disgree slightly on the colours of the secondary / tertiary stars I see the primary as a yellowish colour and the other two brick red. That said, looking here http://www.jouscout.com/astro/belmont/belmontd.htm it suggests white and red for the sec/tertiary stars so my eyes must be going!

[chiltonstar]

I totally agree that this is a stunning double, one of my favourite systems. I use it as a guide to seeing and ca often split the three components readily with my 6" f11. I tend to disgree slightly on the colours of the secondary / tertiary stars I see the primary as a yellowish colour and the other two brick red. That said, looking here http://www.jouscout....nt/belmontd.htm it suggests white and red for the sec/tertiary stars so my eyes must be going!

And yet Cambridge quotes "yellow, lilac and blue"; I had another good look last night and made sure that my eyes were white-adjusted by looking at Vega for a few minutes beforehand. I would have said white (hint of blueish) for the primary, definitely yellowish for the secondary, and a blue tertiary star - mainly blue but perhaps a hint of purple.

There has been an online debate of this question of perceived colours on "the other astronomy forum" with some very informed contributions. My feeling is that imaging the system is more likely to be definitive, even though there are still issues eg on processing. My pic of Beta Cyg a few nights ago is quite close to my perception of the visual colours of this double...... but is it how others see it (my eyes are rather ancient)?

Chris

[carlc]

It may be my monitor calibration (or my eyes) but I see the A component as more yellow through my Tal - however according to my wife (an artist) I'm not colour blind just colour stupid. In your picture the B component looks blue edging towards violet to me.

[Moonshane]

I suppose it is down to colour perception often seen when describing various things. I agree that imaging would give better diagnosis of colour assuming the processing was colour neutral (whatever that means!)

[John]

It's a lovely triple star regardless of it's tints

With my 4" refractor the mag 6.9 component is right on the diffraction ring of the brighter one. It looks a bit like a diamond ring

A useful test of seeing conditions as Shane says.

FWIW, with my ED120 refractor this evening, the primary looks pale lemon, the close companion blue / grey-ish and the fainter one orange-ish. Maybe my eyes are going too !

[chiltonstar]

With reasonable seeing last night, I had another look at Iota Cas, this time with my ED80. Nicely resolved and interestingly enough, with the smaller scope, the colours were very different - principle star white, secondary yellow, and the tertiary star a kind of deep cocoa red. Must all be down to number of photons hitting the eyeball and the colour response of the scope, I suppose...?

Chris

[Moonshane]

I agree chris, I thin the atmosphere, optics, state of mind (tiredness etc) all play a part in what we see. whatever the colours, it's a cracking system, cannot wait for another fave, Sigma Orionis to come around again.

[chiltonstar]

I agree chris, I thin the atmosphere, optics, state of mind (tiredness etc) all play a part in what we see. whatever the colours, it's a cracking system, cannot wait for another fave, Sigma Orionis to come around again.

I've had a few looks at Sigma Ori over the years with my 4" long focus achro refractor, but the false colour always gave some problems; I'll have a look with my 5" Mak soonish and see what I think!

Chris

[cotterless45]

Lovely triple, had a look in a 200 Dob. Thanks for posting, nice,

Nick.

[alan potts]

I will give iota Cas a go it sounds a nice system.

Alan.