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Trapezium "E" an Orange Star? Visual Obs. needed

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#1 Cotts

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Posted 25 January 2014 - 03:23 PM

Consider my photo from last year: in another thread

It seems to show "E" to be distinctly orange in colour when compared with the other 5 stars...

Any visual confirmation from the CN community?

Dave

#2 Bonco

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Posted 25 January 2014 - 05:31 PM

The biggest scope I've used for E is a 10 inch. Because of its dimness I saw no color other than faint grey or dim bluewhite. More gray I'd say. larger scope might reveal the orange tinge.
Bill

#3 Rich (RLTYS)

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Posted 26 January 2014 - 08:03 AM

The biggest scope I've used for E is a 10 inch. Because of its dimness I saw no color other than faint grey or dim bluewhite. More gray I'd say. larger scope might reveal the orange tinge.
Bill


The same here.

Rich (RLTYS)

#4 azure1961p

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Posted 26 January 2014 - 12:35 PM

Dave,

If you s scroll down to James7c post in the trap-f thread he's got a photo that just begins to reveal the warm hue of E. I really tried to reason this one out as prismatic refraction or the like but it doesn't add up. I think the star is simply yellow-orange. Without checking Id say something like an F spectra?

Lol now I gotta check don't I.

Pete
Edit - all I'm getting is spectra O-B and such for the bright four - cant find spread info on others. I will say between your image, James and still someone else's like 6 months ago Ive seen this star as warm
Hued three seperate times in seperate images by obviously seperate astronomers. It is a persistent thing it would seem.



#5 youngamateur42

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Posted 26 January 2014 - 01:10 PM

I was observing the Trapezium last night and thought maybe I was seeing some color, I'll have to go back and take another look.

#6 The Ardent

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Posted 26 January 2014 - 01:25 PM

When I observe the Trap with my 18", the B star has a slight brown or orange tint. Ive seen this for several years.

#7 Sasa

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Posted 28 January 2014 - 10:19 AM

My telescopes are too small to see color on E-star. But interestingly, I see the brightest star © as of having golden yellow/orange tint. Quite strange, as it should be blue... It is not the only spectral type O star that I see yellowish. Another one is for example the main star of system STF2816 in open cluster Trumpler 37 in Cepheus.

#8 David Knisely

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Posted 29 January 2014 - 05:36 AM

Consider my photo from last year: in another thread

It seems to show "E" to be distinctly orange in colour when compared with the other 5 stars...

Any visual confirmation from the CN community?

Dave


I agree. The E star appears a dim reddish-orange color in my 10 and 14 inch Newtonians. The only data I have been able to find on the E star is that it is magnitude 10.3 and spectral type anywhere from F5 to G2, but this could be in error (no good B-V data appears to be available for it). It is also a spectroscopic binary. Many other observers have also reported E to be slightly reddish in hue, so you are not alone. It could be reddened by dust or made to appear more orangish than it is due to the color contrast with bluish-white Theta Ori C nearby. Clear skies to you.

#9 CelestronDaddy

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Posted 29 January 2014 - 10:35 AM

Dave - I've got this on my list to look at. Don't know that I'll be able to detect any visual color with my scopes but I'll try with my 6"SCT. I checked the Trapezium out a few weeks ago with my 102mm but I was just trying to see if I could detect F. I hope some of the folks here with larger scopes are able to determine some color for E....

#10 azure1961p

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Posted 29 January 2014 - 11:23 PM

Its a testament to the progressive nature of astronomy that this topic - complete with pics - is had on an object observed tirelessly by amateurs for untold decades.

Pete

#11 Cotts

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Posted 30 January 2014 - 09:43 PM

Its a testament to the progressive nature of astronomy that this topic - complete with pics - is had on an object observed tirelessly by amateurs for untold decades.

Pete


True, that. The digital photographs being taken with amateur scopes these days excel anything the Palomar 200" did in its heyday....

I wonder if there are older reports (pre-digital age or so, going back to the 1600's) which mention "F" being orange/yellow. I would not know where to look to find such information.

Dave

#12 azure1961p

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Posted 30 January 2014 - 10:35 PM


Id wonder if Fred might have the information on that. I've always been impressed with his referencing.

Pete

#13 fred1871

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Posted 31 January 2014 - 03:10 AM

If it counts as a reference, I've had a look at what Robert Burnham wrote in his Celestial Handbook. There are quite extensive notes on the Orion Nebula and the Trapezium. It's useful because he mentions various historical observations.

But, first up, the E and F stars are discoveries from the early 1800s. No earlier records. Burnham gives the credit for first recording star E to FGW Struve; for star F, to John Herschel. The WDS lists the first measures as 1832 for AE and 1842 for CF. These dates are slightly later than those Burnham mentions (he gives 1826 for E and 1830 for F).

Among Burnham's notes - TW Webb (mid-1800s) suggested that star E "is believed to have become visible only of late years; perhaps it may be brightening, as it has been seen with a 3.8-inch...". To be remembered is that William Herschel had not seen these stars (E and F)with his large telescopes.

Again from Webb: "E. of Rosse sees it very red". Burnham comments that "any impression of reddish tints in any of these stars must be attributed to the effect of contrast with the greenish background of the nebulosity". (Smyth had also called on of the stars "reddish").

Of course, the visual colour-contrast effect does not apply to photos, but my impression is that getting accurate colour in digital imaging of the sky is tricky - I know a few advanced astro-photographers who comment to that effect.

Looking at Webb directly (the Dover 1962 reprint of the 6th edition from 1917), Webb remarks of E and F that "Both have been thought var." This suggests to me that 19th century observers were puzzled about the varying visibility of the stars - claimed seen by some with small telescopes (SW Burnham, both seen, with a mere 3-inch (76mm) refractor!!!) - yet not easy, especially F, with larger apertures.

Otherwise, I can't offer much information at present. I do notice that the measures recorded in the WDS summary lines suggest that separations of AE and CF have increased over time, which would make both stars somewhat easier to see nowadays with smallish telescopes. However, given the magnitudes - somewhere in the 10-11 range - seeing colour in them visually will require larger apertures. I find I don't see colour in isolated stars of mag 10.5 to 11 or so with my C9.25. But, perhaps when set in a greenish nebula there might be a false-colour effect; I'll try it next clear night.

#14 dave brock

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Posted 15 February 2014 - 05:06 PM

But, perhaps when set in a greenish nebula there might be a false-colour effect; I'll try it next clear night.


I always see E with an orange hue in my 20". I don't see any colour in F so I don't think it's a contrast effect from the nebula.

Dave

#15 GlennLeDrew

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Posted 15 February 2014 - 05:53 PM

If there has been a detectable change in separation, it would strongly suggest a foreground object. At near 1,500 l-y, a visually separated double/multiple should not exhibit a sensible proper motion difference in a couple hundred years... I think.

If a member of the Trapezium, at its brightness it must be intrinsically bluish. Perhaps reddening from foreground dust could be in effect, but it must be pretty well localized to affect one and not others in the immediate field. But it should not be dust in/near the group, for stellar winds will have already cleared out a large bubble.

I think it's a color contrast effect. Perhaps GAIA will pin down the B-V color...

#16 dave brock

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Posted 15 February 2014 - 08:08 PM

I think it's a color contrast effect. Perhaps GAIA will pin down the B-V color...


Any thoughts on why it doesn't happen with F or any other stars of similar brightness in the field? ( In the past I have wondered if it was contrast so have purposely looked for the effect in other fieldstars but E is the only one that shows any colour ). It also still has the effect when enough power is used such that the nebulosity no longer has the greenish hue.

Dave

#17 cpsTN

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Posted 15 February 2014 - 08:32 PM

Several nights ago, I easily saw E in my 12" at 122x. No color though.

#18 GlennLeDrew

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Posted 15 February 2014 - 09:33 PM

Dave,
During visual examination it would be interesting to mask off the other (at least brighter) Trap stars. They might be the more important element in a color contrast scenario.

#19 R Botero

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Posted 23 February 2014 - 02:20 AM

Spotted E (and F) last night from my backyard before imaging Jupiter. No colour perceptible to me in E at either 200x or 315x using a (new-to-me) 10" f/20 MaK. M42 is rather low from my latitude (51N) and I was observing from a spot that placed the Trapezium above the roof of my house, so conditions were not optimal.
Roberto






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