7 Tauri at last

[Nik271]

I finally managed to bag this triple star yesterday, after reading about it on this forum.

It was a misty and very still night yesterday, the Met office and CO agreed there should be a clear spell around 9pm and they were right, hurrah!

My 180 Skymax lives in the shed and I quickly put it on the EQ5. At this time I was almost sure it will come to nothing because as of 7pm I could not see a single star!

Amazingly the sky started to clear from 8pm. It never really cleared completely and I could only see stars up to 2-3 magnitide, just enough for navigation with the 9x50 finder. Luckily 7 Tauri is easy to find: continue a line from Atlas to Alcyone, the handle of the 'mini big dipper' of the Pleaides asterism and you are going to hit 7 Tauri, a bright 6-th magnitude star after going on  about 2 degrees from the Pleiades.

I tested the seeing first with Theta Aurigae (easy at x350) and Delta 3 Tauri in the Hyades (quite hard but intermittently visible, separation is 1.8'' and magnitude difference is 3.5). Even at x350 the stars looked stable. So I aimed at 7 Tauri with confidence. 

The distant component C (10-th magnitude, NE of the primary) was easily visible, but at first it looked that my focus on the primary star was slightly off. As some of you know these Maks are no joy to focus with the knob at high magnification. Eventually I realized that I'm in focus - simply the star is very close pair 🙂 It looked like a figure 8 oriented north south, both components of equal brightness. The separation is just .7'' and the two diffraction patterns were intersecting and looked like tiny ripples in the blackness. I kept looking at it for 15 minutes at least, and the view was very steady.

I was hoping to contiue with some other tough doubles (Dubhe?) but when I looked up again I could not see any stars, just milky glow from the Moon.

My hands were frozen from the manual tracking - too excited to connect the cables for the RA drive. When I packed the scope at 10pm the Moon had a halo. Everything was so still it felt like being in another world.

Very pleased with this session! The high pressure air sitting over us will be worth the foggy days  if the night skies clear a few more times.

Cheers and clear skies!

 

Nik

Edited December 22, 2021 by Nik271
typo corrected

[John]

Excellent report and a lovely description Nik

My clear(ish) patch last night only lasted long enough to have a look at Jupiter, Nepune, the rising moon and Theta Aurigae before the cloud cover thickened.

I'd like to have a crack at 7 Tauri with my 130mm refractor when I get a chance

[Sunshine]

Nice report, it is satisfying when you finally split a tough double.

[Mr Spock]

Nice report. I’m looking forward to getting the 250 on it and hopefully get a good split. The old  C9.25 used to do it. 

[JeremyS]

Well done, Nik 👍🏻

[cloudsweeper]

Nice work Nik, 0.77" is very good going.  I've only managed just below the 1.00" mark so far!

Doug.

[glafnazur]

Nice report, I'll have a crack at that when I'm next out

[MylesGibson]

I've never managed below 1.2" so far!

[Nik271]

37 minutes ago, MylesGibson said:

I've never managed below 1.2" so far!

You should try Tegmine (Zeta Cancri). The separation is 1.1'' and the two components are of equal brightness. A four inch scope in good seeing should be able to show the separation.

[MylesGibson]

48 minutes ago, Nik271 said:

You should try Tegmine (Zeta Cancri). The separation is 1.1'' and the two components are of equal brightness. A four inch scope in good seeing should be able to show the separation.

I have tried that one a number of times, but the seeing is just never quite there to split into 3. I've been close and once I thought I had it but wasn't sure. I'll get it one day!

[John]

The seeing has to be pretty good for me to get sub-arc second splits here. Tegmine is a good test.

52 and 32 Orionis are another couple that stretch the scope and seeing (and observer !). 32 is 1.3 arc second split and (usually) doable. 53 is fractionally under an arc second and can be very tough. Both nicely on show in the top half of Orion's "torso" currently.

 

 

Edited January 7, 2022 by John

[John]

Had a crack at 7 Tauri with my 130mm refractor just now. At 300x - 400x I got the bright pair of stars as a clear "∞" or "peanut" or "snowman" or "waisted pair" form with just a few tantalising suggestions of the actual split from time to time during the moments of steady seeing. The 10th magnitude star further away was quite easy to see.

Thanks for the "heads up" on this one Nik. Well worth seeking out

 

Edited January 14, 2022 by John

[chiltonstar]

7 Tauri is on my list - sounds like a nice multiple to test system and eyes.

If you struggle with focus at high mag Nik, a decent focuser is a great help - I added one a year or so ago and it really makes it easy, particularly for imaging. I can send a pic if you like.

Chris

[Nik271]

Well done, John! Excellent seeing and a good refractor are a winning combination, plus an experienced observer of course!

What focuser do you have Chris? I have a 1.2inch helical focuser from SVbony but find it not very precise and slipping a bit with a diagonal and a heavy EP.

[chiltonstar]

18 minutes ago, Nik271 said:

Well done, John! Excellent seeing and a good refractor are a winning combination, plus an experienced observer of course!

What focuser do you have Chris? I have a 1.2inch helical focuser from SVbony but find it not very precise and slipping a bit with a diagonal and a heavy EP.

Revelation 2" SCT Crayford, dual speed. Fits on easily, said to vignette at low power with a wf eyepiece, but I've not noticed it.

Chris

[Nik271]

Thanks! I don't mind vignetting at the low powers, it's the high powers where fine focusing is needed.

[Captain Scarlet]

I have one of those revelation focusers going spare, but it would need to be collected from Sunbury on Thames as I am not in the UK to be able to post it. I got it intending precisely to put on my own skymax 180, where it works fine just as @chiltonstar says. But then a feathertouch cpc8 came up and I now use that. Incidentally there is also one of those apparently available on ABS but they are pricey https://www.astrobuysell.com/uk/propview.php?view=181010

Magnus

Edited January 15, 2022 by Captain Scarlet

[chiltonstar]

Last night's seeing was excellent here despite the Moon, and the thick hoar frost covering everything underfoot, so an evening to try 7 Tauri with the 180 Mak.

The faint, wide mag 10 component was clear despite the sky brightness, and the main pair looked to be a double even at low mag. High mag (x375) showed the pair as a very white close pair like car headlamps seen at a distance, with clear dark space between them, and a stable single diffraction ring. I was surprised by how good the separation was - it almost looked more than the 0.8 arcsec listed in Stelle Doppie, but a tribute maybe to the wonderful seeing.

A lovely multiple, thanks again Nik for the heads up.

Chris

[Jiggy 67]

Never tried this one so thanks for the tip. I’m gonna give it a go this week, possibly tonight. Moonlit nights tend to mean I use the the 4 inch frac so I’m guessing 7 Tauri will be a challenge 

[Nik271]

 

1 hour ago, chiltonstar said:

Last night's seeing was excellent here despite the Moon, and the thick hoar frost covering everything underfoot, so an evening to try 7 Tauri with the 180 Mak.

The faint, wide mag 10 component was clear despite the sky brightness, and the main pair looked to be a double even at low mag. High mag (x375) showed the pair as a very white close pair like car headlamps seen at a distance, with clear dark space between them, and a stable single diffraction ring. I was surprised by how good the separation was - it almost looked more than the 0.8 arcsec listed in Stelle Doppie, but a tribute maybe to the wonderful seeing.

A lovely multiple, thanks again Nik for the heads up.

Chris

I observed it too last night with my 180 Mak. Indeed the seeing was so good it seemed almost too easy!

 

@Jiggy 67, if the seeing stays like this with a 4 inch you should be able to see at least an elongation or a 'peanut' shape.

[John]

2 hours ago, Nik271 said:

 

 

@Jiggy 67, if the seeing stays like this with a 4 inch you should be able to see at least an elongation or a 'peanut' shape.

Yes, I got that quite clearly with my 100mm refractor last night. Not much of a "waist" to it but no doubt that it is a pair of stars

Somewhere between "elongated" and "resolved" from the guide below, with the 100mm:

 

 

Edited January 18, 2022 by John

[Jiggy 67]

2 hours ago, John said:

Yes, I got that quite clearly with my 100mm refractor last night. Not much of a "waist" to it but no doubt that it is a pair of stars

Somewhere between "elongated" and "resolved" from the guide below, with the 100mm:

 

 

Thanks John but……that chart changes my definition of “resolved” and could result in a lot of work for me to go back over all my written records!!!!! 🤣

[John]

Good seeing tonight. I split 7 Tauri with my 12 inch dobsonian quite clearly using 338x (Ethos SX 4.7mm). Very pleasing looking system with the 10th magnitude star a little further from the very close pair.

I don't manage sub-arc second splits that often and this is one of the nicest I've done

[mdstuart]

John

With my 4.7mm eyepiece it looks like a North South line with the other star below the line. Presumably need a bit more mag to get a peanut split! in the 8 inch dob.

I might try Tegmine next.

Mark

[catburglar]

Just managed to split 7 Tau this evening in my 10 inch SCT. Seeing was not quite as good as last week and the split was suspected at 250x with a 10mm Ortho. At 357x with the 7mm ortho the split was clear- two tight airy disks with a shared diffraction ring in a north / south line with the C component clearly separate some distance to the north.