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Pages: 1 azure1961p Postmaster Reged: 01/17/09 Loc: USA Porrimas Albireo effect       #5276368 - 06/17/12 11:46 PM Edit   Reply   Quote Quick Reply   I had a really terrific view of Porrima for the first time. Other times the seeing was 3-4/10 Pickering. Finally I get 7/10 withy my 70mm and I swung it onto this double. I know what the books say - identical F spectrum stars. What seemed persistent - even beautiful however was the fact that one seemed yellow the other a cold white or very light blue. I investigated this online and found it was a case of atmospheric dispersion. Its hard to believe though. The colors seemed to natural. Anyone else see this discrepency ever? Pete PS: Im 51 -I finally get a night thats good and clear for this double. The majority of my doubles observed however are from Vulpecula to Polaris as luck would have it I often always ended up with poor southern exposure no matter where I lived. Its got and upside as there are so many doubles now that Im only starting to see. Edited by azure1961p (06/17/12 11:47 PM) Post Extras:       David Knisely Postmaster Reged: 04/19/04 Loc: southeastern Nebraska Re: Porrimas Albireo effect [Re: azure1961p]       #5276522 - 06/18/12 02:40 AM Edit   Reply   Quote Quick Reply   Quote: I had a really terrific view of Porrima for the first time. Other times the seeing was 3-4/10 Pickering. Finally I get 7/10 withy my 70mm and I swung it onto this double. I know what the books say - identical F spectrum stars. What seemed persistent - even beautiful however was the fact that one seemed yellow the other a cold white or very light blue. I investigated this online and found it was a case of atmospheric dispersion. Its hard to believe though. The colors seemed to natural. Anyone else see this discrepency ever? Pete PS: Im 51 -I finally get a night thats good and clear for this double. The majority of my doubles observed however are from Vulpecula to Polaris as luck would have it I often always ended up with poor southern exposure no matter where I lived. Its got and upside as there are so many doubles now that Im only starting to see. In my 4 inch f/6 refractor a few weeks ago, the double was well resolved and both stars looked almost identical (an off-white color). They also look like that in my 9.25 inch SCT, although in that scope, they are more of a pure white color. Clear skies to you. Post Extras:       RLTYS Post Laureate Reged: 12/18/04 Loc: New York (Long Island) Re: Porrimas Albireo effect [Re: azure1961p]       #5276623 - 06/18/12 06:15 AM Edit   Reply   Quote Quick Reply   Observations with my 10" refl have shown the colors of Porrimas to be the same, bluish wht. I've had a similar experience with Gamma Del where the spectrum of both components are the same, so they should appear the same color but instead they appear pale yellow and greenish blue. You might want to check this star out. Rich (RLTYS) Post Extras:       blb Post Laureate Reged: 11/25/05 Loc: Piedmont NC Re: Porrimas Albireo effect [Re: RLTYS]       #5276847 - 06/18/12 10:19 AM Edit   Reply   Quote Quick Reply   Pete, I looked at Porrima, y Vir, STF 1670 last month with my 5-inch ETX 125, using a 7mm eyepiece at 271x. The stars were two equal magnitude off white stars seperated by a thin black line (Sep. = 1.6 seconds). I did not see any color differences in the stars but was very happy to split them, my closest pair split yet. Post Extras:       Rutilus Pooh-Bah Reged: 12/17/10 Re: Porrimas Albireo effect [Re: blb]       #5277278 - 06/18/12 03:07 PM Attachment (44 downloads) Edit   Reply   Quote Quick Reply   This is the view I had with my 6 inch Achromat fitted with a 100mm aperture mask. In my notes I wrote that both stars appeared off white/cream in colour. One of the stars appeared slightly darker than the other. Post Extras:       WRAK sage Reged: 02/18/12 Re: Porrimas Albireo effect [Re: Rutilus]       #5277524 - 06/18/12 06:18 PM Edit   Reply   Quote Quick Reply   This season I have missed most of the double stars in Virgo due to bad weather but in my notes from last year I found the remark "120mm refractor: Two white suns of similar size, clear split". Wilfried Post Extras:       Astrodj sage Reged: 08/24/11 Loc: Missouri Re: Porrimas Albireo effect [Re: WRAK]       #5277627 - 06/18/12 07:32 PM Edit   Reply   Quote Quick Reply   Pete, Last month I observed Porrima and did not note any yellow tints, but I did see an apparent color variation of sorts. Here are my notes from May 10th of this year: Gamma Virginis (Porrima) Date: 5/20/12 Time: 0238 UTC Seeing: 6 of 10 (Pickering) Transparency: 5 Instrument: XT10 Magnification: 150x Notes: Just split with a dark line between the components. Primary is pure white in color; the companion appears white with a blue tint. Post Extras:       azure1961p Postmaster Reged: 01/17/09 Loc: USA Re: Porrimas Albireo effect [Re: Astrodj]       #5277878 - 06/18/12 10:10 PM Edit   Reply   Quote Quick Reply   Here is an EXACT color ccd image of Porrima - its an atmospheric dispersion effect. Amazing. http://www.astropix.com/HTML/SHOW_DIG/Porrima_Gamma_Virginis.HTM Rich, nice rendering. Thanks guys for the reply. Pete Post Extras:       azure1961p Postmaster Reged: 01/17/09 Loc: USA Re: Porrimas Albireo effect [Re: blb]       #5277883 - 06/18/12 10:13 PM Edit   Reply   Quote Quick Reply   Quote: Pete, I looked at Porrima, y Vir, STF 1670 last month with my 5-inch ETX 125, using a 7mm eyepiece at 271x. The stars were two equal magnitude off white stars seperated by a thin black line (Sep. = 1.6 seconds). I did not see any color differences in the stars but was very happy to split them, my closest pair split yet. Ill bet it was a nice sight in the mak. Just when I tried to take it on with my 6"SCT my neighbor turnsw on the drier and it killed my seeing. Porrima was practicaly wedged it was so awful. Such is condo life. Pete Post Extras:       blb Post Laureate Reged: 11/25/05 Loc: Piedmont NC Re: Porrimas Albireo effect [Re: azure1961p]       #5277910 - 06/18/12 10:28 PM Edit   Reply   Quote Quick Reply   Quote: ...This is an effect seen in images and visually when an object is viewed or photographed at a low altitude and the light has to go through a lot of the Earth's atmosphere. The air mass acts as a prism, splitting the wavelengths of white light and diffracting the red light to the bottom of the object, and the blue light to the top. At the time this image was taken, Porrima was only about 33 degrees above the horizon. No doubt that this effect is a very interesting one. Perhaps I did not see it because Porrima was crossing my meridian and at it's highest for me when I observed it. Kind of makes me wont to reobserve this double star at a lower altitude and see what it looks like. Thanks for shareing the web site. Now all I need is a clear sky. Post Extras:       azure1961p Postmaster Reged: 01/17/09 Loc: USA Re: Porrimas Albireo effect [Re: blb]       #5277997 - 06/18/12 11:20 PM Edit   Reply   Quote Quick Reply   Very interesting, as thats how high the elevation was when I observed it! Pete Post Extras:       blb Post Laureate Reged: 11/25/05 Loc: Piedmont NC Re: Porrimas Albireo effect [Re: azure1961p]       #5278619 - 06/19/12 11:06 AM Edit   Reply   Quote Quick Reply   Prismatic atmospheric dispersion. I will bet that this is the reasion for spurious colors being reported by people who observe doubles. Unless the double is high in the sky, above 45 degrees altitude (one and a half atmospheres), how can you really say what colors the double stars are? Post Extras:       ken hubal Pooh-Bah Reged: 05/01/07 Re: Porrimas Albireo effect [Re: blb]       #5279043 - 06/19/12 03:04 PM Edit   Reply   Quote Quick Reply   Agreed! The effect you are referring to is actually called Differential Atmospheric Refraction. I've found that this has a profound effect on spurious color while observing multiple star systems. I've also seen it play a significant role in planetary observation as well when atmospheric conditions are right(dust, particulates, etc.). There was an article in S&T about a dozen or so years back about this phenomena. Post Extras:       JimP Pooh-Bah Reged: 04/22/03 Loc: South Carolina Re: Porrimas Albireo effect [Re: ken hubal]       #5279373 - 06/19/12 06:35 PM Edit   Reply   Quote Quick Reply   Pretty neat! Thanks for the image. Post Extras:       Pages: 1

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