M13 In big Dob +16in - Colour?

[Pingster]

For those lucky enough to have viewed M13 under dark skies and with a Dob +16in.... have you seen the orange and blue stars distinctively? Visual only. Personally in a 16in ive only ever seen the stars as bright white all the way to the core... coreish..... 

[John]

I viewed M13 with a 20" dob from a dark site a few years back. The view was stupendous but I can't recall seeing coloured stars ?

[Beulah]

No coloured stars in M13, through my 400p.

However, with M42 through a 16" in a dark sky....WOW!

[ollypenrice]

Sadly no, in the 20 inch F4.1. However, the brightness at the size and resolution of the view is devastating. But no star colour for me.

Olly

[estwing]

Can't remember will check next week...I'm off to Elan!!

[Pingster]

Looking at a photo of M13 the orange stars are so distinct i hoped that maybe some viewers have managed to see colours in M13 with their dob.

Has anyone seen the colours (orange and blue stars) with an APO and what size?

Sent from my SM-N910U using Tapatalk

[Stu]

In common with the other comments, I've not seen colour in either a 16" don or 6" ED doublet. Pretty sure these are only visible through imaging, or perhaps once you get up to insane apertures under really cracking skies

[jabeoo1]

Glittery & silver/white to the core.  But thats in a minuscule 10" dob. 

[John]

Glittery & silver/white to the core.  But thats in a minuscule 10" dob. 

Same in my 12" - just a little more glitter

[ollypenrice]

Looking at a photo of M13 the orange stars are so distinct i hoped that maybe some viewers have managed to see colours in M13 with their dob.

Has anyone seen the colours (orange and blue stars) with an APO and what size?

Sent from my SM-N910U using Tapatalk

No colour in our TEC140 and I do prefer the large aperture view in the 20 inch on this one, no question. This is not always the case but on this the big one is a clear winner on all counts.

Olly

[Pingster]

What fantastic experiences. Thanks for your replies.

[astronymonkey]

No colour for me either, although its a wonderful object in larger apertures.

I agree with the comment from beulah about m42 in a big dob ... the detail is freakish under dark skies !

Cheers

[Moonshane]

I once saw M13 in a 22" f5 and 31mm Nagler at about 100x. The stars looked as blue as stars in M45 but no orange stars.

[Peter Drew]

No obvious M13 colour in my 30" but plenty of stars.      

[Pingster]

Hehe i was waiting for the replies from the Dozillas and im not dissapointed!

[Stu]

No obvious M13 colour in my 30" but plenty of stars.

I think that counts as conclusive proof that the colour is not seen visually!!

[mert]

I'll have a look but last time I cant remember seeing anything like that.

[Pingster]

Im not sure we have not heard from any 40in dobfrankenstiens yet?

[swamp thing]

At high power I have observed some of the red giants in the core of M13. They give a subtle yellow tinge to my eyes. ( using 16" and 20" reflectors). it requires very high power to get the separation needed though. 

Searching cloudy nights on this it appears I'm not alone

[acey]

Like everyone else, I've never seen colour in M13, using scopes up to 12 inches. It would be a test of the individual's colour perception as well as a matter of aperture. As an experiment you could try finding the faintest naked-eye star that looks distinctly red to your eye, and use that to estimate the minimum aperture you would need to see red stars in M13.

For example, the "garnet star" mu Cephei is magnitude 4. The brightest stars in M13 are magntude 12. To get a gain of 8 magnitudes over the naked eye requires a telescope with an aperture 40 times larger than the eye pupil (because 8 = 5log40). So if a person with a 7mm pupil could see mu Cephei as clearly red then an aperture of 280mm *might* show redness in the brightest stars of M13. However I do not see mu Cephei as red with the naked eye, the brightest stars in M13 are not as red as mu Cephei, and the calculation assumes a perfect telescope.

I see Betelgeuse as very clearly red. It has magnitude 0.4, suggesting that a gain of 12 magnitudes should show me some clearly red stars in M13. Assuming that my eye pupil is 6mm, I would need a clear aperture of 1500mm (59 inches) to achieve this (because 5log(1500/6) = 12).  So if I were to look through the 60-inch telescope on Mount Wilson then I *might* see some red stars in M13.

It should certainly be possible to see red stars using smaller aperture and sufficiently high power, if the observer is sufficiently colour sensitive.

[Pingster]

Thats interesting swampy, i know from observing from you your eyes do appear to have better low light sensitivity than others.

[Stu]

Thats interesting swampy, i know from observing from you your eyes do appear to have better low light sensitivity than others.

I would tend to agree with that! Steve picked out detail in the Crescent when observing at SGLX that I couldn't see.

[Beulah]

At high power I have observed some of the red giants in the core of M13. They give a subtle yellow tinge to my eyes. ( using 16" and 20" reflectors). it requires very high power to get the separation needed though. 

Searching cloudy nights on this it appears I'm not alone

Must try this next time I am out with the dob. Must admit that I have never actually looked out for orange/blue stars in M13.

[estwing]

regularly give this 314x...its having 510x at the weekend...more if I'd got my zoom....where are you mike?!!!

[John]

Thats interesting swampy, i know from observing from you your eyes do appear to have better low light sensitivity than others.

It also raises a very interesting issue for me. In all our discussions comparing visual astronomy tools, ie: scopes, eyepieces and filters of similar specifications, I wonder how often we are discussing differences in the performance of our eyes as individuals, rather than optical goods being served up by the instruments ?