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Kon Dealer
professor emeritus


Reged: 01/05/11

Loc: Cambridge UK
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
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
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
super member


Reged: 05/24/13

Loc: United States
Re: Izar and Porrima new [Re: WRAK]
      #5908459 - 06/07/13 05:53 PM Attachment (9 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
super member


Reged: 05/24/13

Loc: United States
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
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
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
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
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
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
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
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
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
Postmaster
*****

Reged: 12/02/04

Loc: Miami Valley Astronomical Soci...
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
super member


Reged: 05/24/13

Loc: United States
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
super member


Reged: 05/04/13

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
super member


Reged: 08/17/12

Loc: Arad,Romania,Eastern Europe
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
sage


Reged: 10/02/07

Loc: Parsippany, NJ
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
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
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
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
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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