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Kon Dealer
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Reged: 01/05/11

Loc: Cambridge UK
Izar and Porrima
      #5781204 - 04/06/13 07:13 AM

Had two good nights observing these two doubles from my light-polluted back garden.
Get good splits on Izar at around x100 and Porrima at x180 with my 4" refractor.
Izar, in particular, is a beautiful sight- a large yellow/orange star next to a small sky blue one.
What do other people see?


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Rich (RLTYS)Moderator
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Reged: 12/18/04

Loc: New York (Long Island)
Re: Izar and Porrima new [Re: Kon Dealer]
      #5781231 - 04/06/13 07:41 AM

With my 10" refl at 74x all three stars of Mizar appear bluish white.

Rich (RLTYS)


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Bonco
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Re: Izar and Porrima new [Re: Rich (RLTYS)]
      #5782120 - 04/06/13 04:11 PM

Quote:

With my 10" refl at 74x all three stars of Mizar appear bluish white.

Rich (RLTYS)



I think the OP was about Izar in Bootes. His description is spot on. A beautiful colorful double.
Bill


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CelestronDaddy
scholastic sledgehammer
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Reged: 08/22/09

Re: Izar and Porrima new [Re: Kon Dealer]
      #5782129 - 04/06/13 04:17 PM

Good report and description... Tony

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Rich (RLTYS)Moderator
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Re: Izar and Porrima new [Re: CelestronDaddy]
      #5783239 - 04/07/13 07:54 AM

Your right, my mistake. With my 10" refl I've observed Izar (STF 1877) as Pale yellow and pale blue.

Rich (RLTYS)


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Rutilus
Carpal Tunnel


Reged: 12/17/10

Re: Izar and Porrima new [Re: Rich (RLTYS)]
      #5783264 - 04/07/13 08:12 AM Attachment (59 downloads)

I love Izar, one of my time favourite doubles.
In my refractors I see orange primary with a blue secondary.


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ziridava
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
Re: Izar and Porrima new [Re: Rutilus]
      #5783293 - 04/07/13 08:29 AM

I don't remember where but I remember reading that one of our great ancestors,Reverend Webb maybe,was able to split Izar in a 1.5 inch aperture telescope.
I'm very positive about splitting Porrima in my very small reflectors of 72mm F/11 and 76mm F/9.
But about Izar,I had a couple of times the impression I split it in the 76mm F/9 reflector but still not sure.

What is your experience about smallest telescope to split Izar and Porrima,please?

ziridava


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brianb11213
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Reged: 02/25/09

Loc: 55.215N 6.554W
Re: Izar and Porrima new [Re: ziridava]
      #5783365 - 04/07/13 09:11 AM

Quote:


What is your experience about smallest telescope to split Izar and Porrima,please?




Izar: Failed with 60mm, not too hard with 80mm.

Burnham's Celestial Handbook says

"generally a difficult object for a 3 inch glass and not exactly easy for beginners even with a 6 inch. T W Webb, however, observed the images clearly seperated with a 2.25 inch achromat, and also states that Buffham resolved the pair with a 9 inch mirror stopped down to 1.875 inches."

Ancient observations are still relevant as there has been no definite change in seperation since discovery though the position angle has increased from 321 deg in 1829 to 338 deg in 1962.

Porrima: the seperation has been increasing rapidly since 2005/6 when the seperation was only about 0.3 arc sec. Last year I found it pretty easy with 110 mm, this year it should be easier still.


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ziridava
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
Re: Izar and Porrima new [Re: brianb11213]
      #5783457 - 04/07/13 10:09 AM

Thank you Brian,I believe this is the information I remember.

I agree,Izar was not easy pray neither in my 125mm F/7 Newtonian.The main mirror in that telescope it is small but it has a lambda/24 accuracy according to the Millie-Lacroix test made by my friend Gavril Beches who made it and who was a very skilled mirror grinder.
Until I had a prism acting as a secondary mirror ,I was able to split Izar very rarely.Since I changed to a Chinese mirror secondary,I'm able to split Izar on any clear night when Bootis is above horizon.
I believe Izar will be one of the fire-test objects for my refractor under construction using a Carton 60x1000mm lens.


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Kon Dealer
professor emeritus


Reged: 01/05/11

Loc: Cambridge UK
Re: Izar and Porrima new [Re: ziridava]
      #5783805 - 04/07/13 01:32 PM

What's the current separation of Porrima?

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Rutilus
Carpal Tunnel


Reged: 12/17/10

Re: Izar and Porrima new [Re: ziridava]
      #5783808 - 04/07/13 01:34 PM Attachment (60 downloads)

With my 3 inch refractor the companion sits in the diffraction ring, with your 60mm I suspect the
companion will be visible in the inter space between the Airy disk and diffraction.
Carton lenses are great, I've built a scope based on the 100mm lens and it is a superb double star scope.
I will try my scope with a 60mm aperture mask. Here is a photo of my Carton build.


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brianb11213
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Reged: 02/25/09

Loc: 55.215N 6.554W
Re: Izar and Porrima new [Re: Kon Dealer]
      #5783938 - 04/07/13 02:33 PM

Quote:

What's the current separation of Porrima?



The 2013 British Astronomical Association Handbook "Ephemerides of Double Stars", which is kept pretty well up to date with modern measures, has the 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.


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Bonco
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Loc: Florida
Re: Izar and Porrima new [Re: ziridava]
      #5784450 - 04/07/13 06:12 PM

Quote:

I don't remember where but I remember reading that one of our great ancestors,Reverend Webb maybe,was able to split Izar in a 1.5 inch aperture telescope.
I'm very positive about splitting Porrima in my very small reflectors of 72mm F/11 and 76mm F/9.
But about Izar,I had a couple of times the impression I split it in the 76mm F/9 reflector but still not sure.

What is your experience about smallest telescope to split Izar and Porrima,please?

ziridava




I've had several 100% positive resolution views of Izar with my 60mm/900. On occasion its been easy, but also sometimes impossible. Same for Delta Cyg which is similar in difficulty.
Bill


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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Izar and Porrima new [Re: Bonco]
      #5786459 - 04/08/13 05:22 PM

I will have to wait for begin of June to see both Izar and Porrima in my field of view. Current separations should according to WDS be 3" resp. 1.7". Both doubles should therefore be resolvable with rather small apertures around 60mm. Ich will check this with the help of an iris diaphragm when times and clear skies come.
Wilfried


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ziridava
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
Re: Izar and Porrima new [Re: WRAK]
      #5789544 - 04/10/13 02:50 AM

Monday night I splitted Porrima in the 3 inch Newtonian F/9.2 at 93x/''orange'' Celestron Plossl 7.5 mm.
It was a clean, nice split.
No chance with Izar because of clouds.
Mircea


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cildastun
member


Reged: 08/08/12

Loc: Oxford, UK
Re: Izar and Porrima new [Re: ziridava]
      #5790529 - 04/10/13 03:14 PM

Izar (orange-yellow and blue-green to me) splits nicely in my ED80, but not I've not split Porrima with this easily. Splits nicely in my 5" Mak though.

Chris


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buddyjesus
Carpal Tunnel
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Reged: 07/07/10

Loc: Davison, Michigan
Re: Izar and Porrima new [Re: cildastun]
      #5791364 - 04/10/13 09:48 PM

I have issues with the jet stream and low altitude making it where I haven't been able to split Porrima since moving from Colorado. Maybe someday one or the other situation will improve.

Izar a beauty for sure


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ziridava
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
Re: Izar and Porrima new [Re: buddyjesus]
      #5792700 - 04/11/13 04:13 PM

Last night,after splitting Zeta Cnc at first view in my 125mm F.7 Dobsonian,I made some more experiments with Galilean oculars.Using a 24mm Galilean and 2x Barlow for 72x magnification,I splitted Algieba,Castor was seen in an eight shape and the companion of Izar was visible as a small sphere glued to the main star.No dark space but both diffraction discs clearly visible.
Good result for the oldest ocular known on planet Earth!
Mircea


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Izar and Porrima new [Re: ziridava]
      #5793274 - 04/11/13 09:13 PM

Mircea, your description of seeing Izar (Epsilon Bootis) as "a small sphere glued to the main star" with "both diffraction discs clearly visible" using 24mm aperture at 72x is a puzzle - first, because the Dawes Limit for a double with 24mm aperture is about 4.8", and this pair is, on recent measures, around 2.9" or 3.0". And it's uneven as well, by 2.2 magnitudes.

Izar is usually seen as needing much more than 24mm - the observation mentioned earlier in this thread, of Buffham resolving (whatever that term indicated) the pair with 1.875-inches (47.6mm, near enough twice your 24mm) is meant as a best case achievement. The separation has changed little if at all over time.

I note that Sissy Haas in her book records her own observation of Epsilon Boo as follows:
60mm, 120x: A brilliant amber-yellow star with a deep blue spur on its edge...

That's what we might expect of the pair with that size telescope at that magnification in good seeing. At 40% of the aperture and 60% of the magnification it's hard to believe it's possible to get a similar view.



Edited by fred1871 (04/12/13 02:24 AM)


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Bonco
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Loc: Florida
Re: Izar and Porrima new [Re: fred1871]
      #5793337 - 04/11/13 09:39 PM

Fred, Not a puzzle to me. If I read his email correctly he's using a 125mm f7 telescope with a 24mm eyepiece and a 2X barlow = 72X. I've had perfectly resolved views of Izar with my 60mm/900mm scope and find his observation credible.
Bill


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azure1961p
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Reged: 01/17/09

Loc: USA
Re: Izar and Porrima new [Re: Bonco]
      #5793570 - 04/11/13 11:45 PM

Agreed. However if indeed the scope had been a 24mm aperture, Fred's points would stand well of course.

Pete


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Izar and Porrima new [Re: azure1961p]
      #5793735 - 04/12/13 02:19 AM

I thought it was a reference to a galileo scope, such as I've seen some folk experimenting with - rather than a single-lens eyepiece. William Herschel used such single-element eyepieces at times, though that's rare in post-Huyghens observing. Ok, so it's an eyepiece. I shall simply express myself puzzled about combining a later type of telescope with a primitive eyepiece. Which I think is why I misread the note.

Question suggested by my earlier ramble - what's the smallest aperture that anyone's seen Izar split with? We know that 60mm does it, and Buffham with ~48mm. The latter (1.875" aperture, unobstructed) has a Dawes Limit of ~2.4", which suggests it might be near the best possible. Of course, "resolved" as we've often discussed here can mean anything from separated by a black space to vaguely elongated. Any offers of splits need to spell that out.

Edited by fred1871 (04/12/13 02:26 AM)


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ziridava
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
Re: Izar and Porrima new [Re: fred1871]
      #5794938 - 04/12/13 05:15 PM

Please accept my apologies I was unclear and I created confusion.
I was just using a Galilean ocular of 24mm focus at full aperture of my 125mm Newtonian.
I cannot reach focus with Galilean eyepieces without using a Barlow lens.For now I have and sometime use three Galilean oculars of 27mm ,24mm and 18 mm focus.
I like to use them in a sort of reenactment.
Galilean eyepieces were used until the end of XIX Century.
The last famous person to use them was Thomas Grubb.
Apart of historical flavor,they are optically very good.
A good Galilean ocular is able to compete with an orthoscopic.

Off-topic:I start thinking on this forum there are mind-reading people
Once it was unveiled,I have to recognise:it is true,I'm on my way building a Galilean refractor ,this week I made some progress on it.This was supposed to be for a while a ''secret project'' ,meant to be a tribute to the memory of Giovanni Hodierna,a reenactment of his observations.

Mircea


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Bonco
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Reged: 04/17/06

Loc: Florida
Re: Izar and Porrima new [Re: fred1871]
      #5795244 - 04/12/13 07:16 PM

Quote:

I thought it was a reference to a galileo scope, such as I've seen some folk experimenting with - rather than a single-lens eyepiece. William Herschel used such single-element eyepieces at times, though that's rare in post-Huyghens observing. Ok, so it's an eyepiece. I shall simply express myself puzzled about combining a later type of telescope with a primitive eyepiece. Which I think is why I misread the note.

Question suggested by my earlier ramble - what's the smallest aperture that anyone's seen Izar split with? We know that 60mm does it, and Buffham with ~48mm. The latter (1.875" aperture, unobstructed) has a Dawes Limit of ~2.4", which suggests it might be near the best possible. Of course, "resolved" as we've often discussed here can mean anything from separated by a black space to vaguely elongated. Any offers of splits need to spell that out.



Fred,
60mm/900mm telescope with 7mm .965 eyepiece = 128X. Izar perfectly resolved with dark space between the stars. 6mm resolved it too but better viewed with the 7mm.
Bill


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ziridava
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
Re: Izar and Porrima new [Re: Bonco]
      #5812874 - 04/21/13 11:48 AM

Soon I will be able to compare directly my 9mm Vixen orthoscopic to a brand new Galilean eyepiece of 9mm focus.

Coming back to double star observation,last night myself,with my 125mm F7 Dobsonian/ and my friend Emil with his 114mm F8.8 Bird-Jones Newtonian, were in front of the City Hall for a public star party as part of ISAN 6.

It was a nice surprise to be able to split Porrima and especially Izar at 140x/Faworski 10mm Plossl+1,8x Barlow in my 125mm Dobsonian,from that litle corner of Hell.
The complete list of stars on the double/multiple star menu of our ISAN 6 Star-Party were Alcor-Mizar,Castor,Porrima and Izar.
The light polution there is huge:only the Moon,Jupiter,Saturn were visible.I had to guess where to look for Porrima, Izar or Mizar.
After a while,by blind guessing ,I found also M44.
About 120-150 people had their first telescopic view of some heavenly bodies,including some very fine double stars.

Mircea


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Rutilus
Carpal Tunnel


Reged: 12/17/10

Re: Izar and Porrima new [Re: ziridava]
      #5813478 - 04/21/13 04:30 PM Attachment (30 downloads)

Last night I observed Izar with what I thought was a 60mm aperture mask on my 100mm f/13 Carton.
This morning I measured it again and found it to be 58mm. Still the companion was nicely seen with magnifications up to 260x.
The companion appeared to be extremely close to the inside edge of the first diffraction ring, with some light showing
up in the diffraction ring itself. Dark space clearly visible between the primary and companion.
Here is a quick drawing.


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Izar and Porrima new [Re: Rutilus]
      #5814326 - 04/21/13 10:35 PM

Good drawing, Rutilus - nicely shows the pair. Interesting, as you and Bill (Bonco) have now resolved this one with ~60mm at not much more magnification than Sissy Haas recorded with her 60mm refractor, but both of you got a clean separation which her description doesn't suggest she did. Better optics? Better atmospheric conditions? Who knows ....

No doubt the 60mm has a benefit from the placement of the first diffraction ring just outside where the secondary star is located. Interesting. I'll try Izar (Epsilon Bootis) again when my local weather improves. Maybe with my 80mm refractor, then stop it down to 60mm to see the difference (and, I hope, the companion). I don't think it's optically good enough to manage Izar at 50mm - but my very good 140mm refractor might be worth stopping down that far. Hmmm. Think I can hear an experiment suggesting itself.


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brianb11213
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Reged: 02/25/09

Loc: 55.215N 6.554W
Re: Izar and Porrima new [Re: fred1871]
      #5814627 - 04/22/13 04:20 AM

Quote:

I don't think it's optically good enough to manage Izar at 50mm



Stopping down an instrument usually results in the optics becoming near perfect even if they were a bit iffy at full aperture. Especially as the effects of "pinching" by the objective cell will disappear when the outer part of the objective is obscured. Also increasing the working focal ratio is beneficial given the very short focal ratios which seem to be fashionable these days ... it takes a pretty good eyepiece to work well at f/6 & even the better (more complex, well engineered) designs seem to work better at f/7 - f/8 than at shorter focal ratios.


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SeptemberEquinox
sage
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Reged: 01/29/12

Re: Izar and Porrima new [Re: brianb11213]
      #5823880 - 04/26/13 09:28 AM

"diffraction ring"

what is diffraction ring? And in your photos what are those rings around the star?

I was able to split Epsilon Boo(Izar) at 220X ish clearly for the first time last night.


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Rutilus
Carpal Tunnel


Reged: 12/17/10

Re: Izar and Porrima new [Re: SeptemberEquinox]
      #5825071 - 04/26/13 06:53 PM

The diffraction ring - "Diffraction is an optical effect caused by the interference of light
waves in passing around or through any opening, such as a lens or your eye.
A point source is seen as a tiny disk, surrounded by one or more faint rings of light"

"This diffraction pattern consists (assuming a circular objective) of a central bright disc, termed
the spurious disc or Airy disc, surrounded by alternate concentric rings of light and darkness-
the diffraction rings and interspaces".

Quotes taken from from Sam brown's book All about Telescopes and Sidgwick's book Amateur
Astronomers Handbook.

The ring around the star in the drawing is the first diffraction ring. Only on nights of excellent seeing do
I see the ring as a solid circular patern. Usually due to the seeings conditions, the ring appears broken,
often appearing as arcs of light


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SeptemberEquinox
sage
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Reged: 01/29/12

Re: Izar and Porrima new [Re: Rutilus]
      #5825199 - 04/26/13 07:36 PM

So the light is playing trick to our eyes. it's an optical illusion or visual phenomenon?

Thank you for explaining


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Bonco
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Loc: Florida
Re: Izar and Porrima new [Re: SeptemberEquinox]
      #5826697 - 04/27/13 04:36 PM

Quote:

So the light is playing trick to our eyes. it's an optical illusion or visual phenomenon?

Thank you for explaining



It's an artifact from the optical system. Bill


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Ain Soph Aur
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Reged: 08/11/11

Loc: West Tennessee
Re: Izar and Porrima new [Re: Bonco]
      #5831212 - 04/29/13 10:11 PM

Izar nicely split tonight with the Carton 100mm f/13 aperture reduced to 50mm f/26. Companion cleanly split sitting on the first diffraction ring.

I have a nested aperture reduction system in 10mm increments from 90mm to 50mm, I kinda wish I had also had 40mm and 30mm reduction rings made too. 1.2" f/43 could be fun just to see what it is capable of splitting....


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BuffaloTri
member


Reged: 04/23/12

Re: Izar and Porrima new [Re: Kon Dealer]
      #5835976 - 05/02/13 10:29 AM

I took my first attempt at Izar last night with my CT 102mm f/11. The seeing was bad - Arcturus was twinkling to the naked eye, and I was in a white zone.

I tried it at 32x, 110x, and 220x. At 32x I wondered if I was on the right star because there wasn't even a hint of a split. There were occasional hints of the secondary at 110x. I had a clean split at 220x; the primary looked yellow/orange and the secondary was blue. It was not a crisp image because of the poor seeing. The primary itself was boiling and fragments of a diffraction ring would appear and disappear. Still, it was fun to split this double. Hopefully tonight I'll be able to try some magnifications in between 110-220 and find the minimum I need for a clean split.

I also like the idea of an aperture mask. I've always assumed I needed aperture to overcome the LP, but maybe that isn't the case.


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Bill Boublitz
super member


Reged: 05/04/13

Re: Izar and Porrima new [Re: Kon Dealer]
      #5846909 - 05/07/13 11:47 PM

I saw your post and couldn't help responding. Izar is one of my favorites! Sort of like and old friend. It was the first double of any challenge I split through a scope. I view it almost every year. I have always seen the companion more grey-green than blue. But I attribute the color to the particular set of oculars I was given to work with. Most log the companion as blue. I first viewed it with a 101 mm refractor at x145. Truly beautiful object. I never tire of it. Happy to read your post! Thanks.

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aquariusnic
newbie


Reged: 05/11/13

Re: Izar and Porrima new [Re: Bill Boublitz]
      #5854778 - 05/12/13 03:08 AM

Hi,

That was last may 7th, after seeing the double Algieba - very nice - in Leonis i had no problem splitting Porrima in Virgo on my balcony. The seeing was excellent (9/10) and my Tasco 60/900 showed it very well at 90X and better at 144X (12,5mm barlowed) like two close little diamonds. But I never saw the Izar companion with this.


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StarDusty
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Reged: 10/02/07

Loc: Parsippany, NJ
Re: Izar and Porrima new [Re: aquariusnic]
      #5855541 - 05/12/13 01:55 PM

I have not looked at Izar this year yet, but imaged it last summer. (Sorry, not in color.)

For a black and white image go here:

http://www.clearskyobserver.com/index.php/component/jce/?view=popup&tmpl=...


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grom
member


Reged: 02/23/09

Loc: Spain
Re: Izar and Porrima new [Re: StarDusty]
      #5860232 - 05/14/13 03:32 PM

A few days ago, with good seeing. Porrima two Airy discs were touching or almost-touching in a 80mm APO.

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Silver Bear
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Reged: 04/02/13

Loc: Brazos Valley in Texas
Re: Izar and Porrima new [Re: grom]
      #5863042 - 05/15/13 07:55 PM

Two nights ago, I viewed Porrima, saw the color differences, but could not quite split the double under high magnification due to wind blowing against my light little telescope. Still, a very nice sight.

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Bill Boublitz
super member


Reged: 05/04/13

Re: Izar and Porrima new [Re: Silver Bear]
      #5878654 - 05/22/13 05:39 PM

My customary small instrument is a 101 mm refractor. Last night, I stopped it down to 60 mm with an aperture mask and split Izar quite easily. 1. The image was dimmer (than full aperture) 2. Colors seemed more vivid, more pronounced. 3. Prominent diffraction ring around primary - which is hardly noticeable at full aperture. Magnification was x225.

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John_G
sage


Reged: 01/18/10

Re: Izar and Porrima new [Re: Bill Boublitz]
      #5886596 - 05/27/13 05:24 AM

I had a great look at Izar last night at 237x with my 90mm. I saw the blue/green companion on the first diffraction ring. Very nice colors.

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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Izar and Porrima new [Re: Bill Boublitz]
      #5886604 - 05/27/13 06:00 AM

Bill, I think with some bright doubles the colours are better seen/more pronounced with less aperture. Almost as if the eye gets over-saturated with light in the manner of a camera sensor with larger telescopes. One I'm familiar with down here is Alpha Centauri, very very bright, and the colours (yellowish and deep yellow, contrasting) I find more obvious with 80mm than with 180mm or 235mm. The bigger telescopes tend to show it as near-white for both stars.

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Kon Dealer
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Re: Izar and Porrima new [Re: fred1871]
      #5886620 - 05/27/13 06:53 AM

Quote:

Bill, I think with some bright doubles the colours are better seen/more pronounced with less aperture. Almost as if the eye gets over-saturated with light in the manner of a camera sensor with larger telescopes. One I'm familiar with down here is Alpha Centauri, very very bright, and the colours (yellowish and deep yellow, contrasting) I find more obvious with 80mm than with 180mm or 235mm. The bigger telescopes tend to show it as near-white for both stars.



That's my experience too. I get better colour in my Kson102ED, than my 6SE and 8SE.
What is more viewing is much less "seeing" dependent.
Had my 6SE out last night and Izar was a constantly seething mess. Swapped it for the Kson and instantly stable.


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Bill Boublitz
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Re: Izar and Porrima new [Re: Kon Dealer]
      #5887755 - 05/27/13 07:37 PM

Fred, Kon, thanks for the input. Also, as Brian mentioned above, "Stopping down an instrument usually results in the optics becoming near perfect." I concur with this.

Not meaning to go off topic, but surveyed six doubles last night with the 60 mm aperture stop in place; 90 Leonis, 38 Lyncis, 65 Ursae Majoris, Struve 1881 in Virgo, 17 Draconis and Delta Serpentis. All wide pairs ranging from 2.5" to 4.0" in separation. I was stunned at the clarity of the images. The only pair that didn't hold up as well was Struve 1881. It was a split at x90, though x135 provided a pleasing view. At x225, the companion dissolved into a ghost like smudge. Had good sharp Airy on the primary, but a mere "cloud" in the P.A. of the companion.

I'm hooked. Every double star aficionado should experience stopping down an instrument they know well - especially a refractor.

So much to look at... so little time.


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WRAK
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Re: Izar and Porrima new [Re: Bill Boublitz]
      #5888844 - 05/28/13 12:12 PM

Yes, my experience too - reducing the aperture with masks or iris diaphragms results in more saturated colors, better seeing and therefore crisper spurious disks. Overall higher aesthetic pleasure.
Wilfried


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labmand
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Re: Izar and Porrima new [Re: WRAK]
      #5889502 - 05/28/13 06:30 PM

Was able to split Izar but not Porrima, when I tried to find the current PA I found 303, 11.1 and 10 for 2013 doing
a search and checking the WDS. The sep also came up with
1.9" and 4.5", please help me understand these numbers.

Edited by labmand (05/28/13 06:33 PM)


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Bill Boublitz
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Re: Izar and Porrima new [Re: labmand]
      #5891048 - 05/29/13 05:31 PM

Lab .... When I check the current WDS, this is what I find for Porrima; Last measurement 2011, companion was then in Position Angle 319 degrees, the separation then was 1.6 arc-seconds between the components, magnitude of A was 3.48, that of B; 3.53.

If this doesn't help clarify, ask a more direct question. Many of us would be glad to help you in anyway we can. ~Bill


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labmand
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Re: Izar and Porrima new [Re: Bill Boublitz]
      #5891255 - 05/29/13 08:10 PM

Thanks Bill,
When I go here (database for wds I think)
http://stelledoppie.goaction.it/index2.php?iddoppia=54650
I see 2013 pa as last=10 and also 303
sep shows 4.5"
so this is where I'm, a little confused.


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Bill Boublitz
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Re: Izar and Porrima new [Re: labmand]
      #5891314 - 05/29/13 08:49 PM

Hi Dave! Well, an interesting website. A quick glance seems to indicate a lot of accurate data. It is not the WDS. The actual WDS doesn't list current information, as they monitor thousands of stars and review each submission for accuracy before entering.

Porrima is a quick moving binary (period 169 yrs.) so one can observe significant change well within a lifetime. It was closest in 2005 and all but unsplitable in amateur scopes. I first split it around 2006/2007 with a 4" aperture. It may be resolvable with 80 mm at this time. I don't know. Haven't looked in two years.

Here's the Washington Double Star Catalog; http://ad.usno.navy.mil/wds/

I'll be out hopefully tonight, definitely tomorrow night, so I'll give Porrima a look and report back. Good wishes, don't give up!


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fred1871
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Re: Izar and Porrima new [Re: labmand]
      #5891347 - 05/29/13 09:06 PM

The WDS lists both the first measure of a double star, and the most recent. That appears to be where you've got confused. Porrima is a binary that's been changing quickly in recent years, so the numbers depend a lot on the date. Porrima was at 4.0" separation in 1980, 0.4" (!!) in 2004, and is now widening again.

The first good measure of it was by FGW Struve back in the early 1800s, and since then it's gone through more than a complete orbital revolution - the orbital period is listed at 169 years. And the orbit, as we see it from Earth, gives a huge variation in the separation of the stars.

The 2012 measure in the WDS is a separation of 1.7 arcseconds in PA 013 - just east of north. Because the pair are in the faster-moving part of their mutual orbit the numbers are changing quickly, and if I remember correctly the separation is now close to 2.0".

With this double as with others in the WDS, the summary line gives two time-slices - two dates of measures - which don't always provide a clear picture of what's happening. If you want more information on Porrima, the 6th Orbital Catalog, available on the USNO website along with the current WDS and other lists, has a diagram showing the measures superimposed on the calculated orbit - click on "P" on the far right of the data lines in the Orbit Catalog. There's also an ephemeris - presently, 2011-2015 - under "E" beside that.


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labmand
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Re: Izar and Porrima new [Re: fred1871]
      #5891646 - 05/30/13 12:43 AM

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.


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Jon Isaacs
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Re: Izar and Porrima new [Re: labmand]
      #5891894 - 05/30/13 07:48 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


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Silver Bear
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Re: Izar and Porrima new [Re: fred1871]
      #5904464 - 06/05/13 06:09 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.


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labmand
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Re: Izar and Porrima new [Re: Silver Bear]
      #5904832 - 06/05/13 10:07 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.


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Silver Bear
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Re: Izar and Porrima new [Re: labmand]
      #5905004 - 06/05/13 11:34 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...

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.


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labmand
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Re: Izar and Porrima new [Re: Silver Bear]
      #5906197 - 06/06/13 02:47 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.


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orion61

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Re: Izar and Porrima new [Re: Rutilus]
      #5906389 - 06/06/13 04:34 PM

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

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Cepheus Elf
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Re: Izar and Porrima new [Re: orion61]
      #5906461 - 06/06/13 05:24 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


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labmand
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Re: Izar and Porrima new [Re: Cepheus Elf]
      #5906679 - 06/06/13 07:27 PM

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


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fred1871
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Re: Izar and Porrima new [Re: orion61]
      #5907313 - 06/07/13 02:57 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.


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Kon Dealer
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Re: Izar and Porrima new [Re: Silver Bear]
      #5907334 - 06/07/13 04:47 AM

Quote:

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...

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


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WRAK
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Re: Izar and Porrima new [Re: fred1871]
      #5908352 - 06/07/13 04:49 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


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Nucleophile
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Re: Izar and Porrima new [Re: WRAK]
      #5908459 - 06/07/13 05:53 PM Attachment (8 downloads)

Quote:

... 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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Nucleophile
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Re: Izar and Porrima new [Re: Nucleophile]
      #5908463 - 06/07/13 05:57 PM Attachment (12 downloads)

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


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WRAK
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Re: Izar and Porrima new [Re: Nucleophile]
      #5909214 - 06/08/13 05:28 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


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ziridava
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Re: Izar and Porrima new [Re: WRAK]
      #5909563 - 06/08/13 11:11 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


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WRAK
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Re: Izar and Porrima new [Re: ziridava]
      #5910905 - 06/09/13 05:55 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


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ziridava
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Re: Izar and Porrima new [Re: WRAK]
      #5910987 - 06/09/13 08:47 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


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jgraham
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Re: Izar and Porrima new [Re: ziridava]
      #5911031 - 06/09/13 09:34 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.

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Nucleophile
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Re: Izar and Porrima new [Re: jgraham]
      #5911043 - 06/09/13 09:41 AM

Hi John,

What colors do you see when for this double?


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Bill Boublitz
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Re: Izar and Porrima new [Re: Nucleophile]
      #5911840 - 06/09/13 07:21 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.


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ziridava
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Re: Izar and Porrima new [Re: Bill Boublitz]
      #5922409 - 06/15/13 02:44 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


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StarDusty
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Re: Izar and Porrima new [Re: Bonco]
      #5924623 - 06/16/13 11:20 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.


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WRAK
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Re: Izar and Porrima new [Re: StarDusty]
      #5924860 - 06/17/13 04:23 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


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WRAK
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Re: Izar and Porrima new [Re: WRAK]
      #5952493 - 07/03/13 03:27 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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