Taurus Double Doubles & Subarcsecond

[cloudsweeper]

 

6.45pm Monday – clear, still, cold.  Using 8SE for a change – aiming for a subarcsecond double, and manual tracking is difficult at high magnification.  Aligned on Aldebaran.  Started in each case with x48/1.34deg.

 OΣ95 (STT95) – 7^th mag, 0.9” separation.  GoTo spot on.  Only a faint pair above.  x203, x303 – less sharp – needed a tad more mag – x339 – Bingo! – well matched pair, very close, sec at 4 o’clock – focus critical – great result, for separation of 0.9”.

The following two are less than 0.5deg apart:

 Σ674 (STF674)  also CD Tau – 6^th & 9^th mag, 9.9”, (2)+1, status uncertain. 

Σ680 (STF680) – also 6^th & 9^th mag, 9.2”.

GoTo spot on again – both the above were in the same FOV (1.34deg).  The fainter secondaries were not immediately apparent, but appeared on close inspection – very faint, very close in each case, at 7 o’clock and 5 o’clock respectively.  A bit clearer at x56.  So – a double double, but a much better spectacle was to come……

The following two are less than 0.25deg apart (i.e. <900arcsec, whilst the Lyra Double Double pairs are about 210arcsec apart):

ΣI7 (STFA7) – 7^th mag, 44”.

Σ401 (STF401) – 6^th mag, 11”.

GoTo not spot on, but targets quickly found nearby.  Same FOV as before – two near-matched pairs, similar brightnesses  – brighter than the previous pairs, and pairs closer, separations greater, secondaries at 7 o’clock and 8 o’clock respectively – very easily seen, a fine double double, beautiful!

 Very pleasing views, and the satisfaction of breaking the 1” separation barrier!

Doug.

 

[Stu]

Well done Doug! Sub arcsecond doubles are pretty tough!

[cloudsweeper]

23 minutes ago, Stu said:

Well done Doug! Subarcsecond doubles are pretty tough!

Dead right Stu!  They are only manageable with similar magnitudes and high altitudes.  I've managed a few  - they really give you a buzz when you crack them!

Doug.

[chiltonstar]

Good stuff - sub arcsec can be a challenge unless the seeing is excellent!

I'm still waiting for someone to come up with a triple-triple!

Chris

[Epick Crom]

Well done Doug👍 Going past the 1" mark is a great achievement

[dannybgoode]

It's reports like this that inspire me to try some double stars as it's not something I've done before. 

The next clear night I may well give it a go - any hints or pointers and any good starter pairs to go for in the Eastern hemisphere (my view westward is blocked by houses)?

[cloudsweeper]

8 minutes ago, dannybgoode said:

It's reports like this that inspire me to try some double stars as it's not something I've done before. 

The next clear night I may well give it a go - any hints or pointers and any good starter pairs to go for in the Eastern hemisphere (my view westward is blocked by houses)?

Thanks Danny.  I recommend the Cambridge Double Star Atlas, or Sissy Haas's Double Stars For Small Telescopes.  Meanwhile, could you view Ursa Major in the east?  Try the well-known Mizar/Alcor double there.  Also: 

Sigma 1258 - matched, 7th mag, 10" separation, SAO 042512

Sigma 1315 - matched, 7th mag, 25", SAO 014808

Sigma 1349 - one fainter, 19", SAO 014903

Sigma 1561 - fairly bright primary, 9.1", SAO 043841

Sigma 1559 - mismatched, just 2" sepn, SAO 015580 - this requires more mag, something in the region of x150.

Happy hunting!

Doug.

9 hours ago, chiltonstar said:

Good stuff - sub arcsec can be a challenge unless the seeing is excellent!

I'm still waiting for someone to come up with a triple-triple!

Chris

Thanks Chris - there must be loads of line-of-sight triple triples out there.  I'll be on the lookout now as I scan the skies!

Doug.

8 hours ago, Epick Crom said:

Well done Doug👍 Going past the 1" mark is a great achievement

Thanks Joe.  Yes - it takes aperture, decent seeing, small delta-mag, and highish altitude.  The Cat did well to separate the stars at x339.  An 8 inch frac would have been better though!  😉

Doug.

And I hope you'll all allow me the indulgence of an attempt at better sketches............................

[dannybgoode]

@cloudsweeper thank you,  appreciated. Yes I've been looking at getting the double star atlas for some time. Birthday coming up so perhaps I'll ask Santa for it

[johninderby]

I’ve been trying to decide if I should get the Cambridge Doible Star Atlas or An Anthology of Visual Double Stars. The Sissy Hass book now is nearly £100.00 used and insane money new.

[cloudsweeper]

1 hour ago, johninderby said:

I’ve been trying to decide if I should get the Cambridge Doible Star Atlas or An Anthology of Visual Double Stars. The Sissy Hass book now is nearly £100.00 used and insane money new.

Blimey - I didn't pay anything like that for SH a few years ago.  Not heard about that Anthology - must look it up.  CDSA is very good - I prefer it to SH, as it also gives SAO numbers to aid location, whereas SH only gives RA and Dec.  Plus, SH has a great number of line-of-sight doubles, while CDSA has mainly physical ones.

Doug.

Edit - it seems the Anthology gives details of 175 examples.  SH and CDSA each have over 2000 examples, so perhaps constitute better value?

Edited March 2, 2021 by cloudsweeper

[wookie1965]

Wow great separation 0.9° I have done a 1° never thought I could get less than that next time I am out all being well I will give it a go. 

Great report Doug that scope is well worth keeping. 

[johninderby]

1 hour ago, cloudsweeper said:

 

Edit - it seems the Anthology gives details of 175 examples.  SH and CDSA each have over 2000 examples, so perhaps constitute better value?

Think the Anthology is the better beginners book as it goes into far more detail with a lot of background info and is a “readable” book that should be a lot easier to get into. Notice that the Anthology and CDSA are recommended as companion volumes so buying both looks like a good idea.

Or start with the Anthology and buy the CDSA next. 🤔

[mikeDnight]

6 hours ago, johninderby said:

I’ve been trying to decide if I should get the Cambridge Doible Star Atlas or An Anthology of Visual Double Stars. The Sissy Hass book now is nearly £100.00 used and insane money new.

I gave the Sissy Hass book away not long ago. If I tell you who I gave it to you could go and mug him!  An Anthology of Visual Double Stars isn't as good as I thought it might be and i find it a bit disappointing,  but I find the Cambridge Double Star Atlas quite valuable as an observing aid.

[cloudsweeper]

51 minutes ago, mikeDnight said:

I gave the Sissy Hass book away not long ago. If I tell you who I gave it to you could go and mug him!  An Anthology of Visual Double Stars isn't as good as I thought it might be and i find it a bit disappointing,  but I find the Cambridge Double Star Atlas quite valuable as an observing aid.

Not seen the Anthology - I suppose a collection of "showpiece" doubles would be good to get someone started, but CDSA also indicates best examples with an asterisk and some description.  And having all the data lets you decide if it's worthwhile (or even possible) to try for a given target.  Sissy Haas gives examples not in CDSA - generally optical (line-of-sight) ones - which can of course also make pleasing targets.  CDSA and SH both have good introductory sections too.

Doug.

[Waddensky]

Lovely, nothing like spending a still night Struve hunting. These are some challenging doubles, great results!

[domstar]

I've just had a fantastic night looking for doubles in Taurus. It was great having some direction and focus on a largely unfamiliar part of the sky. I found the first double double at the second attempt and it took me a long time to find the other pair- in fact I only found one double and missed the other. I need to go back soon. I also found a couple near Aldebaran. Thanks a lot for enthusing me. 

One other double worth mentioning is HD 37013- beautiful and just about splittable at 45x in the same field of view as the Crab Nebula. 

Edited March 2, 2021 by domstar
typo

[cloudsweeper]

22 minutes ago, domstar said:

I've just had a fantastic night looking for doubles in Taurus. It was great having some direction and focus on a largely unfamiliar part of the sky. I found the first double double at the second attempt and it took me a long time to find the other pair- in fact I only found one double and missed the other. I need to go back soon. I also found a couple near Aldebaran. Thanks a lot for enthusing me. 

One other double worth mentioning is HD 37013- beautiful and just about splittable at 45x in the same field of view as the Crab Nebula. 

Glad you enjoyed the viewing Dom.  HD 37013 / Sigma 742 is on my list  - something for next time!

Doug.

[Pixies]

Have just bought the Anthology, as I found it secondhand for not too much.

It looks just the job for me. I like the readable style and I find that the context makes my observing more satisfying.