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Double stars in small refractors

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#1 Robert Zebahl

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Posted 22 January 2019 - 12:24 PM

The last evenings I mainly observed double stars using my small refractors. The observation notes can be found on my website. One of the highlights was 12 Lyn and Rigel, which I also sketched. It was a pleasure to observe and sketch them.

Attached Thumbnails

  • 2019-01-21_stf668.jpg
  • 2019-01-21_stf948.jpg

Edited by Robert Zebahl, 22 January 2019 - 01:15 PM.

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#2 acr_astro

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Posted 22 January 2019 - 12:48 PM

Hi Robert,

great sketches docunenting your observations!

Clear skies,

Achim

#3 ziridava

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Posted 22 January 2019 - 02:41 PM

Robert

 

Thank you for sharing.

I'm very impressed by your sketch and separation of Rigel with a 55mm refractor.

I remember once I read about a spliting of Rigel with a 45mm refractor by Kitchiner.

Unfortunately I didn't  bookmarked that information and I'm not able to find it again.

The smallest telescope quoted in old books to split Rigel is a three inch refractor- this is what I found.

Do you intend to continue this topic ,please ?

 

Ziridava



#4 frank5817

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Posted 23 January 2019 - 12:21 AM

Robert,

 

Very good captures.

 

Frank :)



#5 Robert Zebahl

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Posted 23 January 2019 - 04:42 AM


Do you intend to continue this topic ,please ?

Yes, I will smile.gif

 

Yesterday I had another chance to observe some doubles and used my 63/840mm refractor (Zeiss Telementor I). I observed 12 Lyn again and it was quite interesting to see the differences by just increasing the aperture a little bit. Just compare the sketches of 12 Lyn with 55mm und 63mm.

 

What's also interesting: When the difference in brightness of the two components increases, the fainter companion might be only visible as a brightening on the first diffraction ring of the main component. This I saw again yesterday when observing 38 Lyn. Today I will probably observe 38 Lyn again with my 70mm refractor to have a comparison.

Attached Thumbnails

  • 2019-01-22_stf948.jpg
  • 2019-01-22_stf1334.jpg

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#6 Asbytec

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Posted 23 January 2019 - 05:15 AM

Very cool, welcome aboard. :)

 

I like 38 Cyg...looks difficult. The way I like them. 



#7 Uwe Pilz

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Posted 23 January 2019 - 06:00 AM

Double stars are more rewarding than mos think. I have Sissy Haas' book which gives additional encouragement.


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#8 Asbytec

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Posted 23 January 2019 - 09:04 AM

Double stars are more rewarding than mos think. I have Sissy Haas' book which gives additional encouragement.

I agree. I ignored them for decades in search of larger prey. Only when I moved to excellent seeing did I dabble with doubles and realized what I was missing all those years. Some challenging, some beautiful...all rewarding. 


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#9 niteskystargazer

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Posted 23 January 2019 - 11:17 AM

Robert,

 

Welcome to CN .

 

Nice sketches of  Double stars (In Small Refractors) smile.gif .

 

CS,KLU,

 

thanx.gif ,

 

Tom



#10 Robert Zebahl

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Posted 09 February 2019 - 01:15 PM

Not sketched, but observed: 32 Eri

 

Uwe recommended this double star. I had a look at 32 Eri with my 55mm refractor a few days ago. Very nice, especially the colors! My notes:

 

At 27x split, but still tight with noticeable difference in brightness. A slight difference in colors could be seen. At 56x the color difference was very evident: The brighter component appeared slightly yellowish, the fainter one slightly bluish. Highly recommended!

 

Many thanks to Uwe for this little gem bow.gif


Edited by Robert Zebahl, 09 February 2019 - 01:37 PM.

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#11 Robert Zebahl

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Posted 09 February 2019 - 06:24 PM

Today I had the chance to observe some more doubles with my little 55mm refractor. I also observed 32 Eri again to make a sketch showing the colors. Because I only draw with pencils I added the color in the post-processing step.

Attached Thumbnails

  • 2019-02-09_32_eri.jpg
  • 2019-02-09_65_uma.jpg
  • 2019-02-09_gamma_leo.jpg
  • 2019-02-09_xi_uma.jpg

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#12 ziridava

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Posted 10 February 2019 - 01:01 PM

Robert 

 

Your 55mm refractor is doing a very good job.

Xi UMa is not a very easy double star for bigger telescopes.

 

I checked my logbook and I split 32 Eri on January 30 , 2012 using a 125mm F/6.9 reflector and a 76mm F/9 reflector.

Unfortunately I did not registered nothing else except 32 Eri and 62 Eri were resolved also by the 76mm reflector , which  being a second hand bought commercial instrument , was at that time  ''on probation'' regarding optical performance.

Webb Deep Sky Society site is stating  close to 32 Eri ,at PA=165 deg, there is a 10.5 mv star which is suspected to be member of these system.

 

https://www.webbdeep...t?object=32+Eri

 

Ziridava


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#13 Robert Zebahl

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Posted 10 February 2019 - 01:27 PM

Xi UMa is not a very easy double star for bigger telescopes.

It depends on the current distance, which changes over the years. Last measurement from 2017 stated 1.9 arcsecs and its getting greater the next years.

 

And yes, I'm very happy about this little refractor. I just bought the lens and assembled the telescope based on an old 70/700mm refractor tube. It is mechanically a very simple telescope, but the optical performance is quite decent, even though the coating is not perfect anymore (very sensible when cleaning the lens).


Edited by Robert Zebahl, 10 February 2019 - 01:28 PM.


#14 Astrojensen

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Posted 10 February 2019 - 02:19 PM

Robert

 

Thank you for sharing.

I'm very impressed by your sketch and separation of Rigel with a 55mm refractor.

I remember once I read about a spliting of Rigel with a 45mm refractor by Kitchiner.

Unfortunately I didn't  bookmarked that information and I'm not able to find it again.

The smallest telescope quoted in old books to split Rigel is a three inch refractor- this is what I found.

Do you intend to continue this topic ,please ?

 

Ziridava

"Practical Observations on Telescopes, Opera-Glasses and Spectacles" William Kitchiner, 1800, p. 18 and 19. https://books.google...escopes&f=false

 

I've split Rigel with a 42mm f/28 achromat (80/1200 stopped down to 42mm), using a magnification of 48x.

 

 

Clear skies!
Thomas, Denmark



#15 ziridava

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Posted 12 February 2019 - 11:50 AM

Thomas 

 

Thank you ,thank you very much !!! bow.gif

 

First , congratulations for splitting Rigel with a 42mm aperture ,that is really awesome!

Second, this is the information I was recollecting.

Now I understand where I was at mistake because I kept on looking and searching in the books of Lockyer.

Don't ask me why...

Oh , Kitchiner is an author very dear to my heart ,I printed his Astronomy and Optics books and read them.

Those pages are crammed with information , so it happen to remember an information but not the source.

 

Robert

 

Thank you for the details about the refractor ,clear sky , Mircea


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#16 frank5817

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Posted 12 February 2019 - 07:27 PM

Robert,

 

More fine looking sketches here.

 

Your doing very nice work.

 

Frank :)



#17 Robert Zebahl

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Posted 28 February 2019 - 12:34 PM

Some days ago I visitied a very fine triple in Cancer: zeta Cnc. Besides 12 Lyn this is one of the finest triple stars I observed. I used my 120mm f/5 achromat, because the angular distance between component A & B is about 1.1" - probably nothing for 55mm aperture.

Attached Thumbnails

  • 2019-02-24_stf1196.jpg

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#18 frank5817

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Posted 02 March 2019 - 07:07 PM

Robert,

 

This triple (Zeta Cnc.) in Cancer is a very nice one in your sketch.

 

Frank :)



#19 Robert Zebahl

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Posted 10 March 2019 - 11:30 AM

On Friday I finally received the book by Sissy Haas. Yesterday evening it was quite stormy, but I still wanted to observe something. While looking through the Sissy I became aware of a few double stars which I would not choose purely from the data. The wonderful description of Sissy pushed me with the 55mm refractor to the inner yard.

 

The colored drawings were sketched with Faber-Castell Polychromos on black photo paper and then edited with Darktable. The sketch of 90 Leo is a pure pencil sketch.

 

88 Leo
At 42x well split with moderate distance. Primary component appeared white-yellowish. Pretty unequal pair.

 

90 Leo
At 42x A and B very tight and unequal. Far away much fainter component C. All components almost in line. Very nice view.

 

83 Leo & tau Leo

Two wonderful double stars in very beautiful field. Both showed a slight color contrast. The B-components looked gray-bluishish, the A-components white-yellowish, where tau Leo's showed a hint of orange.

 

gamma Leo

This double I observed again at 59x and paid more attention to the color: A appeared yellow-orange, B white-blue.

Attached Thumbnails

  • 2019-03-09_90_leo.jpg
  • 2019-03-09_83_leo_tau_leo.jpg
  • 2019-03-09_gamma_leo.jpg

Edited by Robert Zebahl, 10 March 2019 - 11:37 AM.

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#20 Robert Zebahl

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Posted 10 March 2019 - 11:31 AM

Sometimes I ask myself how colored sketches come about. Here is the raw scan of one of my sketches.

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  • 2019-03-09_83_leo_tau_leo_01.jpg

Edited by Robert Zebahl, 10 March 2019 - 11:31 AM.

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#21 Anthony236J

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Posted 13 March 2019 - 08:22 AM

These are some really nice observations and sketches! Thanks for posting.

#22 Marty0750

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Posted 16 March 2019 - 09:28 AM

I have seen Rigel companion in 60mm refractor with difficulty This has more to do with aging eye otherwise I am sure it would be easier. The refractor is the one in my signature. A 60mm cheapo from ebay. Bought it for $60 more for curiosity to see how well it performed.

 

I was rather surprised to see airy disks  at high magnification like your sketches. But star testing by focusing in and out showed pinched optics.  I separated the achromatic elements, discarded the thin spacing ring and added a drop of salad oil and pressed the two elements together until the oil spread evenly in the gap (can be a messy job). But this immediately improved viewing contrast by eliminating two air/glass surfaces but also cured the pinched optics (hint, just screw the retaining ring down so that it only gently presses on the top element).

 

Now the stars are even crisper and binaries like Alpha Centauri, Alpha Crucis and Castor are text book examples with very clean separated airy disks. Star clusters are fine clean sprinklings of stars.  As small apertures are less subject to seeing effects I was sometimes during bad seeing able to see more detail in Jupiter in the 60mm  than with my 90mm Maksutov!

 

I will endeavour to post some sketches.


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#23 Robert Zebahl

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Posted 05 April 2019 - 07:46 AM

I could observe some double stars again the last days smile.gif Here is a selection of my observations...

 

44 Boo
I had picked it out in the Sissy Haas and tried with the 70mm ED refractor. In Sissy's book this double star was stated with a distance of 1.9". Probably a mistake, because in the WDS it is given with 0.9". However, I had found this out after a failed attempt to separate the two stars. Later I visited this double star again with the new 4-inch f/11 ED refractor, but the air was very turbulent. Only in short moments you could see a slight elongation.

 

39 Boo
In the 70mm ED refractor at 44x elongated, partly with constriction. At 67x separated, but very tight. There was no difference in brightness. At 133x clearly separated with a small difference in brightness. A looked pale yellowish, B rather warm-white.

 

mu 1/2 Boo (STFA 28 & STF 1938)
A very nice triple system! First I had observed only the wide pair (STFA 28) in the 70mm ED refractor at 22x: Striking, large distance and difference in brightness. A: white-yellowish, B: gray. Later I sketched this with the 4 inch ED refractor and also captured the tighter component.

 

 

Attached Thumbnails

  • 2019-04-04_mu_boo.jpg

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#24 dUbeni

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Posted 05 April 2019 - 10:20 AM

Hi Robert Zebahl, I've been enjoying this topic for a while and I like the interesting choice of apertures for the different doubles.

 

Thank you for your posts

 

CS

Bernardo



#25 frank5817

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Posted 05 April 2019 - 11:57 AM

Robert,

 

Nice additional double and multiple star sketches here. waytogo.gif 

 

Frank




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