Double stars with under arcsecond separation

[chiltonstar]

What an interesting list! My 180 Mak will reach in theory, and often in practice, 0.7 arcsec splits although it does require excellent seeing - usually warm summer evenings when the ground and air temperatures are similar and there are no thermals. How is the seeing and viewing conditions in your location Armand? The UK suffers from poor wet weather, with many Atlantic storms which means the number of evenings we can observe is often quite limited.

Chris

[markse68]

I took the liberty of making a SkySafari list of Armand's doubles in case anyone likes to try them- I figure there are so many doubles up there that you can easily get lost so having someone else's list helps

Mark

PS I added Tau Cyg as I found that one really tricky despite apparently being 1"

Armand’s Doubles.skylist

[Armand Popa]

21 minutes ago, chiltonstar said:

How is the seeing and viewing conditions in your location

Thank you Chris. I know about the general seeing problem in the UK. Here the situation is better, but I also have to wait for good seeing conditions. My habit, is to make observations from the backyard every evening when the sky is clear. If there is no moon, i am looking for galaxies, clusters or anything i can see from a bortle 7 or 8 sky...  ...

If there is Moon on the sky, or my neighbor forgets to shut down the lights, or the conditions are fare good, then I do doubles.

In generally 1 night out of 3-4 is suitable for under arc doubles

[Xilman]

20 hours ago, markse68 said:

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

Mark

Exactly.  They are widely separated and the secondary would be an easy binocular object if it wasn't so close to the primary.

Clean optics, acute vision and good seeing are essential to see the Pup in a small telescope. Or a big one, for that matter.

Much like seeing Galilean satellites with the naked eye, in other words. Possible, but very much not trivial

[wookie1965]

A great list the best I've done is 1.2° split but then I only have a 5"  Refractor not tried anything closer. 

My main objects are double and multiple star's and clusters just the same as you. 

[Armand Popa]

7 minutes ago, wookie1965 said:

he best I've done is 1.2° split but then I only have a 5"

1.2' with a 5" is amazing! congrats. You have great observational abilities 

With a 8" you will be able to make that list, i am s sure

[wookie1965]

3 hours ago, Armand Popa said:

1.2' with a 5" is amazing! congrats. You have great observational abilities 

With a 8" you will be able to make that list, i am s sure

I had a 8" reflector but I never used it, I bought a Tal 100rs for doubles then my Meade came up I got a dual speed focuser for it from a friend and had an adapter plate made to attach it from Moonraker Telescopes. 

[Armand Popa]

@wookie1965, that`s why I said your observational skills are great. The theoretical resolving power of an 5inch telescope is somewhere around 1 arc second. To do a 1.2" split with that, so close to the 1 arcsec limit is a great achievement. The 8inch reflector`s limit is 0.58 arc sec, so I encourage you to try the 8" reflector. I am sure that 0.9-1" will be very simple task for you! It is very important for the reflector to be well collimated for double stars

The Tal, as I know has amazing image, so I am sure that double stars looks great it that scope!   

 

[wookie1965]

8 hours ago, Armand Popa said:

@wookie1965, that`s why I said your observational skills are great. The theoretical resolving power of an 5inch telescope is somewhere around 1 arc second. To do a 1.2" split with that, so close to the 1 arcsec limit is a great achievement. The 8inch reflector`s limit is 0.58 arc sec, so I encourage you to try the 8" reflector. I am sure that 0.9-1" will be very simple task for you! It is very important for the reflector to be well collimated for double stars

The Tal, as I know has amazing image, so I am sure that double stars looks great it that scope!   

 

Thank you as I have been observing doubles now for a couple of years with the encouragement of a member on here it's all about finding the right magnification and sitting looking at the double stars for more than a second using averted  vision when necessary. You do need good seeing and transparency. 

I usually stick around 1.6° splits the lowest but when everything comes together it's nice go for the closer ones. 

Tegmine is my nemesis I've not split that yet into all 3 components, I would like a 6" Refractor but I will have to get a bigger mount first. 

[Armand Popa]

 

Last night I continued to make observations. Beside some DSO, I observed some under-arc-sec double stars. I used a 12" Dobsonian telesope, with Baader Hyperion Zoom 8-24 Mark IV, and two ortoscopical ep 

Const	Name	Separation	Mag A	Mag B	Comments
Aur	STF657	0.9	8.3	8.81	easy to separate in the  zoom baader 8-24 Mark IV eyepiece
Aur	STT 112	0.9	7.92	8.21	Easy to separate in the 6mm BGO ortoscopic ep
Cam	STF 531	0.9	7.69	8.76	A beautiful double star. Separated. It looks realy nice due the 1mag difference between the components
Cam	STT 88	0.8	7.21	8.34	A hard double. The mag. Difference is more than 1. I had to wait more then 5 minutes to split is. Separated in the 4mm Kasai ortoscopical ep
Cam	STF 635	1	8.56	8.82	Easy to separate in the 6mm BGO ortoscopic ep
Cam	STF 3115		6.55	7.51	A bit difficult to separate due the mag dif. The secondary component is visible under the main star in the 4mm Kasai ortoscopical ep.
Cam	STF 566 AB,C	0.9	5.56	7.49	Resolved but not separated. Perhaps due the big mag difference
Cas	STT50AB	0.9	8.43	8.46	a very nice double star. It is easy to see in the Baader Hyperion zoom 8-24 ep
Ori	STT 517 AB	0.7	6.79	6.99	A very beautiful and easy double. Separated in the 4mm Kasai ortoscopical ep
Psc	BU 1093	0.8	6.73	8.55	Big mag dif. I separated it, but it was the limit for me
Tau	STF 412 AB	0.8	6.6	6.86	part of a triple star. Easy to separate
Tau	A 2419	0.8	8.73	8.93	Beautiful double. Separated in the 4mm Kasai ortoscopical ep
Tau	KUI 15 AB	0.8	6.26	6.56	Beautiful double. Separated in the 4mm Kasai ortoscopical ep
Tau	STT 95	1	7.02	7.56	Easy to separate in the 6mm BGO ortoscopic ep
Tau	KU 23	0.9	6.97	8.59	Resolved but not separated. Both of the components is visible as a small 8 but I cannot separate the, Perhaps due the big mag difference

[John]

Another very impressive list

Your skies, scope and eye must be excellent to be able to split all those sub-arc second pairs and some easily as well.

What sort of 12 inch dobsonian are you using ?

 

[Armand Popa]

42 minutes ago, John said:

Another very impressive list

Your skies, scope and eye must be excellent to be able to split all those sub-arc second pairs and some easily as well.

What sort of 12 inch dobsonian are you using ?

 

The sky in my location is not a big deal..it is bortle 7 ,  I live very close to the center of my city. When I do astronomy from my backyard, I do doubles (light pollution in that case is not a problem at all), and I am shure everybody can split close doubles, but the eye needs training. So I do not have any special eye or ability, I have a lot of training and many hours at the ep...basically I do 2-3 hours of astronomy every time the sky is clear (thanks for my loving wife fort accepting this :)   

I am also sure that my telescope helps a lot. It is an Orion Skyquest 12" Telescope on Dobson mount.

[John]

Thanks for that information. My dobsonian is a 12 inch Orion Optics F/5.3. I usually prefer using my refractors for double star observing but I will need to try the dobsonian more often on those targets I think.

 

[Armand Popa]

58 minutes ago, John said:

12 inch Orion Optics F/5.3

John, your telescope is the good version of my scope! That is an amazing instrument. As I know it is made in the UK. Please let me know when you will make close double observations with it!

 

[Armand Popa]

In the last 3 month, there were few nights with good conditions for under arcsec double stars. Meanwhile I bought a 3.2mm Skywatcher planetary EP for double stars and I am impressed with it`s performance. As the 2.5mm TMB, it need good seeing conditions.

This is the list of the under arcsecond doubles observed in the last three month, made with my two dobsonian telescopes. 

HO22	ori	1" A difficult double, separated  in the 4mm Kasai ortoscopical ep	ORION 305/1500
14Ori	ori	1" easy split	OMEGON 203/1000
52Ori	ori	1" easy split	OMEGON 203/1000
7Tau	tau	0.8" easy split	OMEGON 203/1000
BU332	cmi	0.8" AB is only resolved. I couldn't see the airy disc, it only appeared as an elongated number eight. AC has big separation	OMEGON 203/1000
HR2950	cmi	0.8" splited with the 4mm Kasai ortho ep	OMEGON 203/1000
OME Leo	leo	0.9" easy split in the 3.2mm HR Planetary Skywatcher ep	ORION 305/1500
STF1037	gem	0.8" a very easy split	ORION 305/1500
STF1074AB	pup	0.7" I couldn`t separate the surely, but the double is resolved	OMEGON 203/1000
STF1331AB	uma	0.9" it is a very beautiful triple star, separated in the 3.2mm HR Planetary Skywatcher ep	ORION 305/1500
STF1426	leo	0.9" It was the most spectacular double/triple star ever splited. AB are the 0.9" star, splited in the 3.2mm HR, and  AC is 7"	ORION 305/1500
STF1517AB	leo	0.7" easy split in the 3.2mm HR Planetary Skywatcher ep. The HD name is HD97561	ORION 305/1500
STF799	aur	0.8" it vas very difficult to split in the  3.2mm HR Planetary Skywatcher ep. I observed it for more then 10minutes  to split it for seconds	ORION 305/1500
STT152	aur	0.8" resolved bunt not splited	ORION 305/1500
STT182	cmi	0.9" hard to split, due the big mag difference, and the main star is mag 8	OMEGON 203/1000
STT217	leo	0.8" easy to split in the 3.2mm HR Planetary Skywatcher ep	ORION 305/1500
STT227	leo	0.9" easy to split in the 3.2mm HR Planetary Skywatcher ep	ORION 305/1500
STT235	uma	1" resolved but not separated in the TMB 2.5mm ep	ORION 305/1500

[cloudsweeper]

Good work Armand @Armand Popa.  I recently managed STT95 Tau, 0.9soa with the 8" Cat at x 339.  

Few nights ago, I think I got 7Tau, 0.77soa with the 10" Dob, but clouds came in before I could be sure!

Doug.

[cotterless45]

Great reports Armand !

For those trying , our skies in the U.K. Haven't been the best with regards to seeing . Some nights even 2" stars jiggle about like a clacker toy ! The Jet stream has added to woes !

For those using Newtonian , a single vane or curved vanes eliminate the distracting spikes of cruciform secondary vanes.

My 200 f6 Orion Optics gives almost frac like views of binaries and clusters. Collimation must be spot on to get the most out of high magnification, as does getting "your eye in". Averted vision can help and sketching relaxes the eye , avoiding strain when you end up grimacing !

enjoy , careful now and here's to clear skies !

Nick.

[John]

3 hours ago, cotterless45 said:

For those using Newtonian , a single vane or curved vanes eliminate the distracting spikes of cruciform secondary vanes.

My 200 f6 Orion Optics gives almost frac like views of binaries and clusters. Collimation must be spot on to get the most out of high magnification, as does getting "your eye in". Averted vision can help and sketching relaxes the eye , avoiding strain when you end up grimacing !

 

Does your 200mm Orion Optics have curved secondary vanes or a single vane Nick ?

[cotterless45]

One vane straight across , blooming magical for star definition,

Nick.

[Armand Popa]

Thank you cotterless45! 

Is https://bestdoubles.wordpress.com/ your site? 

 

[Armand Popa]

 

As the sky was clear last night, a took my 305/1500 dobsonian to hunt some underarc doubles. Sadly the seeing was poor, and I struggled to obtain some results. So I managed to resolve some doubles, but I have some doubt of seeing surely the separation, so I decided to not report them as separated  

LY Aur	Aur							0.7	7.17	8.35	1.18		resolved but not split
	Hya			BU 591				1	7.79	8.87	1.08		Resolved but not surely separated, due to the atmospheric conditions
15Lyn	Lyn	26051		STT 159 AB				0.7	4.45	5.5	1.05	Y	Resolved but not separated. It is clearly elongated but I cannot separate them
	Lyn			STF 1093				0.9	8.79	8.98	0.19	Y	two 8mag stars, two tiny pairs. Very beautiful
	Lyn	61411		STF 1338 AB				1	6.72	7.08	0.36	Y	very easy split  in the  3.2mm Skywatcher HR Planetary ep

[Armand Popa]

Last night the seeing was near perfect at my site, so I observed other under arc second double stars from my list. I used my 305/1500 dobsonian with a TMB 2.5mm planetary eyepiece (the Chinese clone) and the 3.2mm Skywatcher planetary ep.

All the starts from the list below are separated with clearly visible airy discs.

A1110 ab	Boo	0.7" eyepiece:TMB planetary 2.5mm
Stf1866	Boo	0.7" eyepiece:Hr planetary 3.2mm
STT288	Boo	0.9" eyepiece:Hr planetary 3.2mm
STT 313	her	0.9mm eyepiece:hr planetary 3.2mm
STT 319	her	0.8"  eyepiece:hr planetary 3.2mm
STF 2203	her	0.8" eyepiece:hr planetary 3.2mm
STT 338 AB	her	0.8" eyepiece:hr planetary 3.2mm
HU 674	her	0.7" eyepiece:tmb planetary 2.5mm
STF 2292	her	0.8" eyepiece:hr planetary 3.2mm
BU 641	her	0.8" eyepiece:tmb planetary 2.5mm
STF 2320	her	0.9" eyepiece:tmb planetary 2.5mm
STT 359	her	0.8" eyepiece:tmb planetary 2.5mm
STF 1860	dra	1"  eyepiece:tmb planetary 2.5mm
STF 2054 AB	dra	1"  eyepiece:tmb planetary 2.5mm
H1-41/HD161692	dra	0.9" eyepiece:hr planetary 3.2mm
STT351AC/HD170109C	dra	0.8" eyepiece:hr planetary 3.2mm
STF2438	dra	0.9" eyepiece:hr planetary 3.2mm
STT369	dra	0.7" eyepiece:Hr planetary 3.2mm
HU66	dra	0.9" eyepiece:hr planetary 3.2mm

[Voyager 3]

Armand , 

Great list of doubles you've split there ! 

[Armand Popa]

 

I add 4 more under arc second double to my list, observed for the firs time last night. I used my 12" dobsonian (as 14th of september is John Dobson`s memorial day) and a 3.2mm Skywatcher planetary ep

Name	Constellation	Separation	Mag A	Mag B	Delta Mag
STF 2597 AB	Aql	0.7	6.94	7.98	1.04	a difficult double . Splited
STF 2729 AB	Aqr	0.8	6.4	7.43	1.03	quite difficult. Splited
BU 163 AB	Equ	0.9	7.31	8.88	1.57	splited. Even with big magnitude difference it was easy to split
STT 435	Equ	0.7	8.31	8.2	0.11	easy split, same magnitude. Nice pair of double. Easy