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Two challenging doubles: STT 377 and STF 2872

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#1 cloudbuster

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Posted 10 September 2019 - 02:58 AM

Last Sunday a clear night was predicted and I decided it was time to test my new eyepiece: the Televue Delite 3mm. And what better way to do this than on a tight double star? In Stelledoppie I used a filter to select a good candidate: magnitude less that 10, delta mag lower or equal to 0.1, separation between 0.8" and 0.9". I found two interesting ones.

 

First STT 377 in Cygnus. A and B are both m9.4 and are separated by 0.9". Funny thing is that they are located in open cluster Teutsch 35, well visible in the finder eyepiece. Even at 400x some of the brighter stars of this OC are still visible in the field and one of them is the tight double. Immediately I see two tiny white dots which are separated about 80% of the time. Not much diffraction is visible and it's a really nice sight. Also the C component is visible, a bit dimmer and at a large distance to the right of the couple.

 

 

STT 377.jpg

 

 

Then on to STF 2872 in Cepheus, which is a bit brighter and tighter. In the finder eyepiece A and B have a large separation and the delta mag is not big. With a white-lightblue glow it's a nice view. But I'm really after component C, at only 0.8" from B, so I switch the eyepiece to the DeLite once more. It's clear that I'm looking at a double star now, but the position is not readily visible. Both stars are moving fast through the field and almost seem to pulsate because of the (intermittent) diffraction rings around it. Despite, about 20% of the time they lose their hold on each other and at that time the PA can be confirmed. This is the tightest double star I've been able to split so far and I'm curious how far the 10" dobson can go. Perhaps I'll try a 0.7" double star in about two months when I'll be back on La Palma (and seeing will probably be near perfect...)

 

 

STF 2872.jpg

 

 

Regards, Martijn


Edited by cloudbuster, 10 September 2019 - 04:36 AM.

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#2 flt158

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Posted 10 September 2019 - 05:00 PM

Superb and delightful images as always, Martijn. 

 

May I have the pleasure of asking you as to how you decide what magnificent tight doubles to observe? 

Do you work off a programme on your PC or some heavily detailed books, e g, Burnham?

 

Please do keep your brilliant sketches coming. 

They bring great joy to many of us on Cloudy Nights!

 

I must observe STT 377 some time soon. 

At present, I am waiting for a clear night to hunt down some more binaries in Cassiopeia. 

 

Kindest regards from Aubrey. 


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#3 rugby

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Posted 10 September 2019 - 05:51 PM

congrats cloudbuster on separating these tight pairs. I will try these  pairs in a 10 f4.54 this evening should clouds allow. How do you like your 3mm? I will use the 3-6 zoom



#4 R Botero

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Posted 11 September 2019 - 01:48 AM

Great report and beautiful sketches Martijn! :bow:

I observed STF2872 in October last year. My notes were:
“Beautiful triple system. NE component is tight double with kissing discs. Single DR envelope. White blue equal at PA300”. This with my 10” f/20 Mak at 300x.

I’m still to observe STT377; thank you for pointing it out! :waytogo:

Roberto

Edited by R Botero, 11 September 2019 - 10:32 AM.


#5 cloudbuster

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Posted 11 September 2019 - 09:41 AM

Thank you all for your kind words flowerred.gif

 

Aubrey: Stelledoppie proves to be a great source for finding any type of double that you wish to observe. Simply go the database and perform a meticulous search. From the list of results, I usually pick either STF or STT, but there will be much more to choose from. Good luck in Cassiopeia when the clouds finally move away smile.png

 

rugby: I have not been using the 3mm much, but so far I like it. It's comfortable and gives a sharp image. The quality is similar to my range of Pentax XW's, but at a bit less apparent FOV.

 

Roberto: That is a nice description of STF 2872 and good to know that the split can be made at much less magnification (sketching it then would be a nightmare though...)

 

Regards, Martijn


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#6 rugby

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Posted 12 September 2019 - 11:45 PM

Bouyed by Martijn's success with STF2872 I tried my hand with it on Sept 12. The seeing was good but far from excellent and a very bright moon was on the rise. I used two scopes: one was a 120mm refractor, the other a 10-inch f 5.45 reflector

The ten did the job admirably. . 200x hinted of a companion with the airy disc an elongated bar. 400x showed two stars separated. There were a number of fainter stars around

I didnt get to study the pair in detail with the smaller aperture


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#7 R Botero

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Posted 14 September 2019 - 03:06 PM

I had a go at STT377 tonight before the full Moon rose above my house’s roof. My notes were:
“Difficult in brightening moonlit sky. Comes in and out of view. Tight equal white blue. Running NESW. Nice asterism.”
Thank you for pointing this one out Martijn! :waytogo:
Roberto

Edited by R Botero, 14 September 2019 - 03:07 PM.

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#8 azure1961p

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Posted 15 September 2019 - 08:07 AM

That Sumerian Alkaid us serving you well here Martijn.  Glad you add the diffraction effects too.  What's interesting here too are all the fieldstars you are pulling in where as with the Mak - plus the limiting NELM - the fields are often minimal of fainter stars. Pristine views but, lol, yes, less crowded.

 

I always appreciate the fidelity you put into your work.

 

Pete




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