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Double stars with under arcsecond separation


Armand Popa
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Hello

As a live in very close to the center of my city, the sky from my backyard is very light polluted. Anyhow, it is not impossible to make astronomical observation, so my main targets on those nights when I can`t go to darker sites, or when the Moon is nearby,  are star clusters and double stars.  In the last period, I pointed my attention to those doubles, where the separation is 1 arcsecond and smaller. As I consider myself a beginner as an under arc second double star observer, i targeted those undersec doubles where the mag difference (delta mag)  is less then 2 , and the main stars mag is less then 10mag and the separation is between 0.6 - 1 arcsecond. Mainly I use two dobsonian telescopes (8 and 12" ) for this kind of observations and high magnifications with Kasai 4mm orhto, BGO 6mm ortho and a 2.5mm TMB planetary eyepiece. For finding I have a red dot finder and a right angle finder scope and an Ipad with SkySafari in night mode :) 

In the last 6 month I observed a ca. 50 under second double stars

I really encourage this kind of observations for light polluted sites, backyards, Moon nights for those who own telescopes with an aperture of 200mm or more .

The observed stars, and also my proposal for those who are interested are bellow: 

cst  name sep mag1 mag2 Comment Telescope
And STF 3056 AB 0.7 7.72 8.08 Part of multiple stars, separated  ORION 305/1500
And AC 14 0.7 8.29 8.88 The atmosphere was not great for under arcsecond doubles but after all I separated it with the 6mm BGO eyepiece ORION 305/1500
Aql A 1181 0.7 7.29 8.83 Delta mag is high, so it was quite difficult to resolve this double. The companion was seen on the diffraction circle of the principal star ORION 305/1500
Cap BU 1211 0.9 7.91 8.79 It is resolved but unseparated. Maybe It is too low in the sky, or the seeing was not good enough OMEGON 203/1000
Cas BU 394 AB 0.9 8.49 8.77 Separated with the BGO 6mm orthoscopical ep. OMEGON 203/1000
Cas BU 232 AB 0.8 8.46 8.79 it is a part of a triple star. In the ep it looks very spectacular. Separated with the 6mm BGO orthoscopic ep and a 2x barlow lens. OMEGON 203/1000
Cas BU 235 Aa,Ab 0.8 7.54 7.82 It was difficult. Separated but it needed patience.  OMEGON 203/1000
Cas STF 96 0.9 7.92 8.92 separated. It is a nice double with delta mag 1 ORION 305/1500
Cas A 816 0.9 7.5 7.81 It was a difficult double. The atmosphere was unstable,  and it needed patience to find some calm moments. After all it was splited. OMEGON 203/1000
Cas HU 1030 0.8 8.93 8.99 Separated with the Kasai 4mm orthoscopical eyepiece.  ORION 305/1500
Cas MLR 377 AB 0.7 8.42 8.7 It a difficult double, separated with the 4mm Kasai orthoscopical eyepiece ORION 305/1500
Cas STT 507 AB 0.7 6.76 7.76 It is part of a triple star with 50" sep between A and C, but the sep between AB is 0.7" It was easily splited in the 2.5mm TMB Eyepiece ORION 305/1500
Cep STF 2 0.9 6.68 6.89 Separated. It`s a very nice double OMEGON 203/1000
Cep STF 13 1 7.03 7.12 Separated. A very nice double ORION 305/1500
Cep STT 28 AB 0.9 7.55 8.75 It was difficult but after all it is separared. I think the delta mag and the seeing made it hard ORION 305/1500
Cep BU 472 0.8 8.76 8.8 This was a very hard double. It was difficult for me to find it and to separate it. It took more than 15min to split this double with the 6mm BGO orto and the 2x barlow OMEGON 203/1000
Cep STF 2780 AB 1 6.09 6.77 Separated ORION 305/1500
Cep H 1 48 0.8 7.21 7.33 Separated ORION 305/1500
Cep STT 458 AB 1 7.2 8.41 It was a difficult double. The mag dif is 1 and it was hard to see the companion.  After all it was splited with the 6mm BGO orto with a 2X barlow lens OMEGON 203/1000
Cep STF 2879 AB 0.7 7.99 8.26 nice double. Separated  ORION 305/1500
Cep STF 2872 BC 0.8 7.98 8 This is one of my favourite under arcsecond double star. The star is a triple star, A and B are quite tight, but BC is a 0.8 double. It is amazing! OMEGON 203/1000
Cyg STT 383 AB 0.8 7.03 8.28 separated ORION 305/1500
Cyg STT 384 AB 1 7.59 8.23 easy double. It was separated ORION 305/1500
Cyg STT 386 1 8.52 8.61 separated ORION 305/1500
Cyg A 378 1 8.48 8.98 separated ORION 305/1500
Cyg STT 403 AB 1 7.31 7.64 It is a part from a triple star. AB and AC was separated ORION 305/1500
Cyg STT 410 AB 0.9 6.73 6.83 easy double. It was separated in a generic 8-24 zoom eyepiece ORION 305/1500
Cyg STT 413 AB 0.9 4.73 6.26 separated with the 6mm BGO ortoscopic ep ORION 305/1500
Cyg BU 155 AB 0.7 7.36 8.13 separated. Nice double ORION 305/1500
Cyg STT 418 0.9 8.23 8.27 It is a very simple double. Separated ORION 305/1500
Del BU 63 AB 0.9 6.2 8.02 Rezolved but not separated. It is clearly elongated but I cannot separate them ORION 305/1500
Del STF 2723 AB 1 7.01 8.3 separated ORION 305/1500
Lac HO 180 AB 0.8 7.92 8.73 Separated with the 4mm Kasai ortoscopical eyepiece.  ORION 305/1500
Lyr STF 2422 0.8 7.93 8.25 separated ORION 305/1500
Lyr STT 371 AB 0.9 7.03 7.55 separated OMEGON 203/1000
Oph STF 2106 AB 0.8 7.07 8.2 Due the tulburent atmosphere , it needed more then 15min to separate this double ORION 305/1500
Oph STT 315 0.8 5.78 7.26 Delta mag is high, so it was quite difficult to rezolve this double.  ORION 305/1500
Oph STT 331 AB 1 7.74 8.82 The components has high mag, and the delta mag is 1.08, it was very difficult. After all it is separated ORION 305/1500
Oph STF 2281 AB 0.8 5.97 7.52 it was very difficult to separate this double. Delta mag is high and the atmosphere was tulburent ORION 305/1500
Peg COU 240 0.8 7.73 8.82 a very nice double. Separated ORION 305/1500
Peg BU 858 AB 0.8 7.81 8.78 not an easy double. It is separated ORION 305/1500
Peg STT 503 AB 1 8.26 8.63 It was easly separated in the Baader 8-24 Mark IV zoom ep ORION 305/1500
Per BU 1175 0.7 7.23 8.8 It was a hard to separate double. It was resolved in the 4mm Kasai ortoscopical ep, but it was separated only in the TMB 2.5mm planetary ep ORION 305/1500
Per HU 1058 0.9 8.22 8.83 easy, separated with the 6mm BGO orto ep ORION 305/1500
Per STT 66 1 8.11 8.54 separated with the 6mm BGO and the 2.5mm TMB ORION 305/1500
Ser AC 11 0.9 6.71 7.21 separated with the 6mm BGO ortoscopic ep ORION 305/1500
Sge STF 2651 AB 0.9 8.41 8.44 a beautiful double star. Separated  ORION 305/1500
Vul HO 580 0.7 8.57 8.9 nice double. Separated  ORION 305/1500
Vul STT 395 0.8 5.83 6.19 separated at 333X OMEGON 203/1000
Vul STT 417 AB 0.9 8.24 8.42 separated at 333X OMEGON 203/1000

Thank you,

Armand

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What an impressive list of doubles to have resolved !

Personally I find sub-arc second splits very hard to achieve. I might have managed a couple of them but that's all.

Well done for having the skill and patience to tackle such challenging targets.

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Thank you Doug. I am sure that with the 10" dobson and TV Radian EP (4-5mm) you will go under the magical 1". After your first under 1, you will become addicted :) 

For the beginning you should try STF2872 from CEP. It is high on the sky right now. It is a double star, where one of the components is also double (that is the under sec double - the right one in your eyepiece) Must be patient, must have a good collimation a perfect focus.   

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Thanks Armand, I shall try to get further into <1 soa doubles.  I'm already hooked on doubles in general!

I've usually used fracs for tight doubles, but maybe I'll try the Dob.  (It is well collimated, and I have fitted a dual-speed focuser.)

Thanks for your encouraging post!

Doug.

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6 minutes ago, Armand Popa said:

John, thank you. I like that kind of challenge :) It is really difficult to split, but the satisfaction is great :)

So do I but I just can't seem to split many of them !

 

 

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1 minute ago, John said:

So do I but I just can't seem to split many of them !

 

 

I didn't see it at first either. Best you can do, is to look at those double that are high in the sky for the moment, and look for those where both has the same mag. The atmosphere must be calm, and you must have a very good focus. You have to wait to see the airy disc and the diffraction circle around the airy. If you will see the circle you will surely see both stars.  

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1 minute ago, cloudsweeper said:

Well there's not much down for the rest of us then!  (Apart from Armand, that is!)

Doug.

I probably don't spend enough time trying Doug.

As I've posted elsewhere a few times, I don't really specialise in any particular type of target - I'm just a "sky tourist" really :rolleyes2:

I can split 52 Orionis with my 130mm triplet refractor which is about the toughest that I regularly observe.

Maybe I ought to spend more time on them with my 12 inch dob ?

I do enjoy trying for very uneven brightness doubles such as Sirius and Antares.

 

 

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the 12inch dobson will do it!

under arcsec double are like faint galaxies...at the beginning you can`t see .Then with some exercice and some ours spent at the ep , you see faint galaxies with advert vision and so on... 

It is the same with those "monster-doubles" 

I didn`t see Sirius as Double yet :(. I will try this year with the big dob, but I know that is very difficult...

 

STF2 in CEP is also a very simple under-arcsec double, it is easy to find and not so hard to split

 

 

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2 minutes ago, Armand Popa said:

I didn`t see Sirius as Double yet :(. I will try this year with the big dob, but I know that is very difficult...

I don't think you need a big scope to split sirius- just a lot of luck with seeing conditions! 

Mark

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3 minutes ago, John said:

I probably don't spend enough time trying Doug.

As I've posted elsewhere a few times, I don't really specialise in any particular type of target - I'm just a "sky tourist" really :rolleyes2:

I can split 52 Orionis with my 130mm triplet refractor which is about the toughest that I regularly observe.

Maybe I ought to spend more time on them with my 12 inch dob ?

I do enjoy trying for very uneven brightness doubles such as Sirius and Antares.

 

 

Same here John - I don't specialise, although I do have a particular attraction to doubles and clusters.  

I'd previously not used the Dob for doubles 'cos fracs do give sharper images of stars, but I'll certainly give it a try.  Uneven mag ones are are I think a different challenge to very tight doubles.  

Anyway, I'm fired up with a new goal - especially in view of the dreadful glare from a neighbour's house/garden which means nebs and most galaxies are out!

Doug.

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5 minutes ago, markse68 said:

That's really impressive Armand- if you don't mind I'm going to make a SS observing list out of your list :)

Mark

I can send an xls file if you want. 

I also offer my help to anyone who is interested in that kind of observations

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7 minutes ago, Armand Popa said:

 

I didn`t see Sirius as Double yet :(. I will try this year with the big dob, but I know that is very difficult...

 

STF2 in CEP is also a very simple under-arcsec double, it is easy to find and not so hard to split

 

 

Well Armand, at least that is something I have managed - I caught a glimpse of the Pup when the sky was not too dark.

Doug.

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I've split Sirius fairly regularly now for the past few years with my 12 inch dob and occasionally with my 130mm refractor as well. I've only managed Antares a couple of times and that was with the 130mm refractor.

I think you are further south than many of us @Armand Popa so Sirius should be that much easier perhaps ?

I'm at 52 degrees latitude here.

 

 

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2 minutes ago, John said:

I've split Sirius fairly regularly now for the past few years with my 12 inch dob and occasionally with my 130mm refractor as well. I've only managed Antares a couple of times and that was with the 130mm refractor.

I think you are further south than many of us @Armand Popa so Sirius should be that much easier perhaps ?

I'm at 52 degrees latitude here.

 

 

:) Yes, I am souther 46 degrees

I maybe need better conditions and must insist...till now I solved the Sirius problem with a "I can`t see the B"

 

 

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