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Izar and Porrima

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#51 labmand

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Posted 29 May 2013 - 11:43 PM

Thanks Bill and Fred for the help, I had better luck tonight with my 8" sct 9.7mm x206, was able to split
Porrima, very tight, the pa does look to be about 10 degrees
I reread the posts in this thread and brianb11213 #5783938 - 04/07/13 02:33 PM post
"seperation increasing from 1.95 arc sec at the beginning of 2013 to 2.11 arc sec at the beginning of 2014,
with the position angle slowly decreasing from 11.1 deg to 8.4 deg"
Looks like good info to me.

#52 Jon Isaacs

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Posted 30 May 2013 - 06:48 AM

Sky Tools 3 computes the separation of short period binaries from the orbital data. Currently Porrima it reports Porrima at 2.02 arc-seconds. The Dawes limit for a 60mm is 1.93 arc-seconds, the Rayleigh Criterion is 2.3 arc-seconds, Porrima is near the Dawes limit for a 60mm, a tough split.

Monday night I had my 60mm x 800mm Asahi-Pentax refractor out in the backyard, I turned it toward Porrima and at 200x, I was able to catch glimpses of a split, the seeing wasn't steady but there were moments when I could see a slight line between the pair.

Izar has always been an easy split for that scope, the first time I pointed it at Izar, I was surprised to see the companion at 90x, I thought it must be an optical defect but increasing the magnification show it was real and I have split Izar many times with it since.

Other splits that evening were Xi Bootes at 5.8 arc-seconds and magnitudes 4.5-7, Pi Bootes at 5.5 arc-seconds and magnitudes 4.5 and 5.9. I also checked out Algieba.

Tuesday night I had out my NP-101, Porrima was a easy split. Alula Australis at 1.68 arc-seconds was doable but it was low over the house and quite unstable.

Jon

#53 Silver Bear

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Posted 05 June 2013 - 05:09 PM

Have been busy, else I'd posted this yesterday!

Finally got a good seeing night here the other night, and was rewarded with my first splitting of of Porrima after several tries. Beautiful double, and had to go very high on magnification with this little telescope to get it...but it was rewarding.

Then, I thought I could split Izar...but I think I spent all my good opportunity on Porrima, as Izar was a no-go...again.

#54 labmand

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Posted 05 June 2013 - 09:07 PM

Ted, I too had a clear night, with my Meade 312 For me, Izar
was an easier split then Porrima, Had to use 2x barrlow
8mm =225, I tried using a mirror diag vs prism and a
raci diag, mirror and prism were close, maybe mirror
a little better, but with raci diag split was very faint.
Another thing I tried was using my Ultima 2x vs my Tele vue
1.8 barlow, The Ultima was winner by a mile.

#55 Silver Bear

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Posted 05 June 2013 - 10:34 PM

My 4" Nexstar is a Maksutov-Cassegrain style telescope, and has a usable magnification limit of ~200X. Of the eyepieces coming in the standard Celestron kit, the 6mm un-Barlowed hits 221X - I cannot use it without the image being affected.

If I run my 8mm eyepiece at a 2X Barlow, it nets me 330X - I see nothing but a blur. Hence, I can only run down to my 13mm eyepiece with my 2X Barlow for 203X - right at my workable limit.

At that magnification, I detected a split with Porrima's companion - but closely.

At this same magnification, I have yet to be able to split Izar, in spite of several attempts. But, hey! I'm still really new at this. I've seen others post above they've split Izar easily at ~165X magnification. For my own lack of results, though, I'm sure it must be an operator issue... :grin:

One day I'll see it, and like Porrima, it will just jump out at me like it was there all along.

Glad you had a really good night as well.

#56 labmand

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Posted 06 June 2013 - 01:47 PM

Ted,
Maybe try "reducing the aperture with masks or iris diaphragms results in more saturated colors, better seeing and therefore crisper spurious disks" as stated in this thread, I know 4" is not alot but may be worth a try.

#57 orion61

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Posted 06 June 2013 - 03:34 PM

Anyone know what the min/max seperation of Izar is and how many years it takes to complete a revolution.

#58 Cepheus Elf

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Posted 06 June 2013 - 04:24 PM

The companion to Izar was the first star which actually appeared to be a true green colour to me. I had used 6" F13 SCT (Opticraft, British made)about 20 years ago. Subsequent views through a variety of other scopes have always shown it to be pale blue. I have often wondered if the fact the old SCT had an uncoated corrector had an impact on the star colours???? I have to say my favourite view was with the old SCT!!

Cheers,
Mick

#59 labmand

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Posted 06 June 2013 - 06:27 PM

orion61
fred1871's and Bill Boublitz
post "orbital period is listed at 169 years"
can't help ya with min/max

#60 fred1871

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Posted 07 June 2013 - 01:57 AM

Separation - minimum was around 2005, less than 0.5", possibly only 0.3" - I'm away from my astro library at the moment so checking full details isn't possible. Max separation is nearly 6", to be reached again in the 2080s.

Previous time it reached minimum (mid-1830s) it was said that no telescope in the world could separate it. Obviously at maximum it's very easy; already it's back to being splittable in quite small telescopes.

#61 Kon Dealer

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Posted 07 June 2013 - 03:47 AM

My 4" Nexstar is a Maksutov-Cassegrain style telescope, and has a usable magnification limit of ~200X. Of the eyepieces coming in the standard Celestron kit, the 6mm un-Barlowed hits 221X - I cannot use it without the image being affected.

If I run my 8mm eyepiece at a 2X Barlow, it nets me 330X - I see nothing but a blur. Hence, I can only run down to my 13mm eyepiece with my 2X Barlow for 203X - right at my workable limit.

At that magnification, I detected a split with Porrima's companion - but closely.

At this same magnification, I have yet to be able to split Izar, in spite of several attempts. But, hey! I'm still really new at this. I've seen others post above they've split Izar easily at ~165X magnification. For my own lack of results, though, I'm sure it must be an operator issue... :grin:

One day I'll see it, and like Porrima, it will just jump out at me like it was there all along.

Glad you had a really good night as well.

Sounds to me like you need to collimate your Mak. I was looking at Izar with my 6SE two nights ago and struggled to split it, yet my 102ED did it easy at x87. Last night I made sure my 6SE's collimation was spot on. Izar was a clean split at just over x100. Seeing was similar on both nights and my 102ED, did the split at x87 again :)

#62 WRAK

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Posted 07 June 2013 - 03:49 PM

Cannot yet contribute recent observations of Izar/Eps Boo/STF1877 due to ongoing cloudy nights but according to my notes from July last year I tried to estimate the separation with the position of the companion in the diffraction pattern with different apertures. Starting with 140mm the position of the companion was outside the first diffraction ring and got closer with reduced apertures and it seemed to sit directly in the first diffraction ring with 70mm. Calculated with 550nm wavelength this would mean ~2.65 arcsecs - at least a reasonable good enough approximation it seems. Surprisinlgy the position of the companion remained unchanged in the first diffraction ring when I reduced the aperture further down to 60 and 50mm so this method is obviously not of much use. But 50mm aperture was certainly enough to split Izar.
Another effect of reducing the aperture was the increased saturation of the impressive orange hue of the primary - the hue of the secondary did not catch my attention so I missed any blue notes (or even green, but this seems of low probability to me ... never heard of a green star, maybe an optical illusion caused by the orange primary).
Wilfried

#63 Nucleophile

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Posted 07 June 2013 - 04:53 PM

... never heard of a green star, maybe an optical illusion caused by the orange primary).
Wilfried


Many observers, including myself through my 15 inch reflector, report seeing the companion of Antares as green.
Through this same instrument, the Izar companion is distinctly blue. That is how my Nikon sees it as well.

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#64 Nucleophile

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Posted 07 June 2013 - 04:57 PM

Also Cor Caroli hints a green hue to me.
this shot was through my 8 inch reflector:

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#65 WRAK

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Posted 08 June 2013 - 04:28 AM

This looks certainly greenish - if not too much image processing is involved here this would count as proof at least for your instrument. Nice photos anyway.
Wilfried

#66 ziridava

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Posted 08 June 2013 - 10:11 AM

This is OT because is not about a double star,please accept my apologies.
I saw many times Zubeneschamali in Libra as green,with naked eye,binoculars and 60x700 mm refractor.
When sky conditions are bad,I see it as some sort of white.
Mircea

#67 WRAK

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Posted 09 June 2013 - 04:55 AM

Last night finally a clear sky with NEML ~3.5mag and even better later on. Seeing moderate with ~6 Pickering. High humidity giving halo to bright objects. Had only my 120mm refractor available without aperture masks, so just for pleasure a look at Izar. x45 was not enough magnification for a split but with x100 it was easy - primary orange yellow as usual, companion rather white. As already mentioned I seem not this sensitive for color hues.
Did some more doubles in Bootes and had a relative success with A2071 1.3" +9.34/9.95mag: With x180 no split but a notched rod indicating the correct position of the companion. Good enough for 120mm to be included in my data set of limit observations, don't think a much smaller aperture could provide a similar result.
Wilfried

#68 ziridava

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Posted 09 June 2013 - 07:47 AM

Only recently I started to observe with my 100mm F/14 Maksutov-Cassegrain telescope.
The mounting is a home made altaz 1,5'' pipe-mount.
I'm not familiar at all with Cass telescopes.
Last night I was observing in the straight-trough mode,using my IOR binocular head adapted to astronomical use,25mm IOR Huygenian eyepieces,magnification of 56x.
Observations made trough sucker holes,high nebulosity in the atmosphere,seeing at Pickering 6.
At Izar I saw a small bright dot,let say a ''sphere'' glued to the main star at eleven o'clock,without any trace of a split with black space.

My personal history of observing Izar is not a smooth one.In the past,for at least ten years ,I was able to see the companion of Izar only once or twice a year.Latter I learned what precluded me was the use of a 25mm prism instead of a secondary mirror in my 125mm Dobsonian.
After changing the 25mm prism with a good 35mm secondary mirror,it was like to have a new,much,much stronger telescope.And splitting Izar become a routine.But usually this happen at magnifications above 100x.
As I said,last night was not a split,but I clearly saw the spurious disk of the companion.
Based on the difficulties I had at splitting Izar, I was first thinking about seeing an artifact.
If this was an artifact of the optical system,why I did not saw the same on stars similar to Epsilon Boo?

To finish my comments,I used the same setup to observe Rasalgheti/ Alpha Her,where the split was complete,with plenty of black space between the stars and where the companion had a strong green hue.

Other stars on my ''bino double star '' menu last night were Graffias/Beta Scorpii and Delta Serpentis,both easy split,great,great views.

The bino head is easy on the sight and no,but absolutely no floaters.

Mircea

#69 jgraham

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Posted 09 June 2013 - 08:34 AM

Izar has become one of my favorite spring doubles. In my 10" f/6.3 LX6 and binoviewers it is simply beautiful. Wonderful contrast.

#70 Nucleophile

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Posted 09 June 2013 - 08:41 AM

Hi John,

What colors do you see when for this double?

#71 Bill Boublitz

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Posted 09 June 2013 - 06:21 PM

Yes, colors are quite an (enjoyable) illusion. Search the archives and you find all manner of interesting descriptions when it comes to hue. You have atmosphere, the particular set of optics used, interplay between members of the system and of course, the observer's vision.

I most often see greenish tints to stars when they are coupled with a red-orange primary. Intuitively, I've always assumed it was my eyes and the light interplay.

#72 ziridava

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Posted 15 June 2013 - 01:44 PM

I know,colors in double stars are tricky.
It is strange that Zubeneschamali in Libra is not a double star but many people,including me,are seeing it as a green star.Simply,beautiful.

Coming back to double stars,Thursday this week I saw for the first time in my 60x700mm refractor, the spurious discs of Porrima as two but touching discs.This and the embraced difraction rings made for an image resembling a scarab.Simply,beautiful!
I used 140x/Vixen 5mm Orthoscopic ocular.

Mircea

#73 StarDusty

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Posted 16 June 2013 - 10:20 PM

I was able to observe Izar last night. Here is my log.

Izar
2013 June 15 10:59p at Jenny Jump by Allen with 4" Schiefspiegler f/29
Multiple Star System in Boötes, R.A. 14h45m36.0s Dec. +27°01'12", Mag's listed at 2.4 and 4.8, Separation listed at 2.9"

Poor to Good Seeing, Clear

Sirius Plössl 40mm, 73x,Sirius Plössl 17mm, 172x,Sirius Plössl 10mm, 292x, Clearly separate at 292x, also separate at 172x, but not at 73x. Minor in ring at 172x. Possible elongation at 73x but only discernible after having seen separation at higher powers. Major much brighter and yellow. Minor gray, green blue. Nice close double star.

Seeing was not good enough to obtain usable avi file. May try again later.

#74 WRAK

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Posted 17 June 2013 - 03:23 AM

Had yesterday despite half moon excellent seeing conditions. Using a 120mm refractor Eps Boo showed an egg with x45 and I got a clear split with x100 and a very generous split with x180. Excellent image with 2 very precise disks, one of them a tad smaller and fainter - it looked therefore a bit "cooler" but as usual I could not dedect any specific blue or green color hues. Reducing the aperture with masks I got down to 50mm with still a very crisp disk for the companion touching the disk of the primary. With 40mm the image was no longer crisp but the companion was still to see as faint fuzzy blob sitting on the primary.
Wilfried

#75 WRAK

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Posted 03 July 2013 - 02:27 AM

Last night thin transparent clouds with only the brightest stars shining through. No regular observing possible but time for a small experiment: Trying first time the 60mm off axis aperture mask for my C925 giving nearly a f/40 scope without central obstruction. Had to try several times to locate Izar through the haze but finally got it - and the view with x180 was instantly gratifying: A very crisp and bright yellow-orange disk for the primary and sitting directly in the quite stable first diffraction ring the greenish-gray secondary (giving a separation of 2.85" calculated with 510mm for dark adapted eyes).
Image without the mask significantly less impressive: Two fuzzy spots barely separated without any color indication.
Wilfried






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