Iota Cassiopeiae No Colour

[Coco]

Last night I got the big Bresser 127L ( with Hyperion 10 & 8mm) out on the skytee/Eq legs extended and pillar, brought a bar stool out made a very comfortable observation.

My question is while the stars were pinpoint sharp they were only white, I was hoping ι Cassiopeiae B would show yellow but sadly not, anyone has seen yellow, my 12-inch dob in the past hasn’t provided any colour either.

Before I blow 900 quid on a Starfield 🙄

[Pixies]

Hi,

yes - I can see colour quite easily in an 8" dob. Both blue and yellow companions. My refractors are both achros - I  can't recall the colour view with them.

Cassiopeia is pretty low just now, plus you would have had the moon spoiling the party.  Perhaps you just need clearer darker skies?

[mikeDnight]

It may help if you defocus slightly. It sounds silly but sometimes it can aid in detecting the colour of stars. 

Edited April 14, 2023 by mikeDnight

[mikeDnight]

On 04/04/2023 at 15:35, Coco said:

Last night I got the big Bresser 127L ( with Hyperion 10 & 8mm) out on the skytee/Eq legs extended and pillar, brought a bar stool out made a very comfortable observation.

My question is while the stars were pinpoint sharp they were only white, I was hoping ι Cassiopeiae B would show yellow but sadly not, anyone has seen yellow, my 12-inch dob in the past hasn’t provided any colour either.

Before I blow 900 quid on a Starfield 🙄

I've had a look through some past sketchbooks but it appears I've never drawn Iota Cass. I have come across some other sketches of colourd doubles though, which might hint at what could be the issue.  In the sketches below you'll notice that the core of the Airy disc is almost white despite the star being strongly coloured. Only around the periphery of the disc was the colour more noticeable.  With Iota Cass being yellow, its entirely possible that its brilliance overpowers its colour. By slightly defocusing the image, the colour hew blends across the image and may become more obvious. Hope this makes sense!

[Coco]

That's fantastic advice and thank you very much, I just ordered a laser cut aperture mask to reduce the optic from 127 to 100mm, and it was only 9 quid delivered, I thought it might help but this information is extremely helpful.

 

[Ratlet]

I've found with some doubles the longer I observe them the less colour I can see.  Try moving off from them and back on. 

@mikeDnight I'm going to shamelessly steal your doubles sketching technique.  Seems most threads you comment on turn me into one of the seagulls from finding Nemo.

[mikeDnight]

3 hours ago, Ratlet said:

I've found with some doubles the longer I observe them the less colour I can see.  Try moving off from them and back on. 

@mikeDnight I'm going to shamelessly steal your doubles sketching technique.  Seems most threads you comment on turn me into one of the seagulls from finding Nemo.

Thanks for the compliment. Feel free to steal away. It's a privilege to be theived from in this way!  

 

[Zermelo]

I've observed iota Cas a few times in Bortle 4, and I've seen the yellow and blue coloration only once, faintly, with a 150mm Newt and an OVL Hyperflex zoom. On the other occasions, all three looked white.

[Mr Spock]

I sometimes find the colour in F type stars difficult to see without a dark background. Perhaps try a different magnification?

[Coco]

18 hours ago, mikeDnight said:

I've had a look through some past sketchbooks but it appears I've never drawn Iota Cass. I have come across some other sketches of colourd doubles though, which might hint at what could be the issue.  In the sketches below you'll notice that the core of the Airy disc is almost white despite the star being strongly coloured. Only around the periphery of the disc was the colour more noticeable.  With Iota Cass being yellow, it's entirely possible that its brilliance overpowers its colour. By slightly defocusing the image, the colour hew blends across the image and may become more obvious. Hope this makes sense!

Thank you Mike , I've added these drawings to my phone for so I don't need to find the OP during obs  👍  

[chiltonstar]

I'd agree with more mag. I can see the colours far more readily at high mag (180 Mak) than with a low mag, wider field view, when the individual stars appear as white pinpoints.

Chis

[John]

I've found the tints in Iota Cass are very subtle. My 130mm refractor at high magnification seems to do the best job on this one (see impression below).

The defocus tip is good and really does make the colours of binaries stand out.

Edited April 14, 2023 by John

[The60mmKid]

If you own another scope or have access to one, I'd be curious to know if you perceive the colors differently with the different instruments. I find that my perception of double star colors varies significantly depending on which scope I'm using. One of the reasons I love observing doubles with my binocular telescope is that I'm struck by how colors seem to pop. 

I'm not a big fan of the Sissy Haas double star book, but one point that it clearly demonstrates throughout is how different observers (using different instruments and under different conditions, of course) report such different colors.

[The60mmKid]

On 08/04/2023 at 07:08, mikeDnight said:

I've had a look through some past sketchbooks but it appears I've never drawn Iota Cass. I have come across some other sketches of colourd doubles though, which might hint at what could be the issue.  In the sketches below you'll notice that the core of the Airy disc is almost white despite the star being strongly coloured. Only around the periphery of the disc was the colour more noticeable.  With Iota Cass being yellow, its entirely possible that its brilliance overpowers its colour. By slightly defocusing the image, the colour hew blends across the image and may become more obvious. Hope this makes sense!

(Case in point: I've been observing Izar and Algieba often lately with my 60mm refractor and perceive the colors so differently than those in these lovely sketches.)

[wookie1965]

I have seen subtle colours in what was my Meade 127 and especially in my Tal 100rs  cracking multiple.