Tricky Double & Others, Best Ever M13, Some Favourites

[cloudsweeper]

1.45am Tuesday – mild, still, clear – 10” Dob in action.  Corona Borealis high in south – arc of seven stars all clear.  Hopped from Epsilon CrB to:

Σ2022 CrB – double, 6^th and 10^th mags, 2.2 arcsec separation.  Not easy because of the Δm figure (delta-mag, difference in magnitudes).  And so it proved – I raised the magnification in several stages starting with x42, and didn’t spot the secondary until x254, and even then it was with AV.  Very faint, at 2 o’clock. Target was part of a triangle of stars, and just north of it was a smaller, fainter triangle (including stars with mags of 12.4 and 12.8) which helped keep the target in view as the magnification increased.  See sketch.

This was not really very pleasing in purely visual terms, but was certainly rewarding when finally split.  Quite a challenge, requiring good seeing.

Next, Iota CrB, and a hop to:

OΣ305 CrB – again, 6^th and 10^th mags, but wider at 5.0 arcsec.  Got the split at x127 – sec very faint, close, at 10 o’clock.

 M13 (GC) in Hercules was nearby, so I aimed at and got it easily with x42 / 1.94deg – a large, bright, clear patch in a busy field.  Although an easy and popular target, I had a Wow Moment at x212 when stars were resolved even in the dense core.  Best I’ve seen it!  At x254, it filled most of the 0.24deg FOV, and still looked good, since the seeing was favourable.

From Cabalrai in Ophiuchus I reached 61 Oph – triple, visual double, both 6^th mag, wide 21 arcsec separation.  Target was part of an equilateral triangle, and readily split at x42 – close, matched, sec at 2 o’clock.

Back to Cabalrai – in same FOV lay IC4665, the Summer Beehive Cluster – a large, loose cluster of several bright stars.  Nice.

Vega was high, east of south.  Spotted the Lyra Double Double to its east using x42 as usual to start – two unresolved pairs, brighter than their neighbours.  Got both of these split at x159, better at x190, 212.

I finished after two very pleasing hours, with the sky already getting lighter. I had also noticed a number of meteors, some without the ‘scope, and others whizzing across the EP view.

Doug.

[wookie1965]

Great report had check then for those doubles in CrB looked in Haas wasnt there then looked in Cambridge double star and found them I will write them down for next time.

[cloudsweeper]

1 hour ago, wookie1965 said:

Great report had check then for those doubles in CrB looked in Haas wasnt there then looked in Cambridge double star and found them I will write them down for next time.

Thanks Paul, much appreciated!  It was an informative session in terms of cracking doubles with differing properties.

Yes - it pays to check out Haas and CDSA.  Haas includes a lot of non-physical examples, whereas in CDSA they are usually physical rather than line-of-sight.

Doug.

[wookie1965]

Yes Doug I have both and usually use both to write my lists I missed those two don't know how. 

With them being I would say on the easier side not like 1.2° splits. 

Paul 

[cloudsweeper]

1 hour ago, wookie1965 said:

Yes Doug I have both and usually use both to write my lists I missed those two don't know how. 

With them being I would say on the easier side not like 1.2" splits. 

Paul 

Dead right Paul - approaching 1.0 arcsec gets harder.  I managed 1.3 arcsec with the long focus 127, but my best so far has been O Sigma 95 Tau, at 0.97 arcsec, using the 8SE.  The stars were well matched.  It gets harder of course if they are not matched, and seeing is poor.

But the first I mentioned above in CrB at 2.2 arcsec was not all that easy because of the large difference in magnitudes.  

Doubles-hunting is certainly interesting, as well as demanding!

Doug.

[wookie1965]

Doug,

             It certainly is interesting and with light pollution it doesn't really matter you can still get out and split them. 

I think I have done a 1.1° split in very good seeing conditions I may get 1° but that would be exceptional. 

I'm pretty sure I am getting a new mount and then save for a Skymax 150 Pro if I have a windfall I may go for the 180 that should put me on par with your 8se I think. 

Paul 

 

[Stu]

On 11/05/2021 at 07:59, cloudsweeper said:

This was not really very pleasing in purely visual terms, but was certainly rewarding when finally split.  Quite a challenge, requiring good seeing.

Do you think LP also played a role in this one being difficult Doug?

Nice set of observations, interesting read, thanks 👍

[cloudsweeper]

19 minutes ago, wookie1965 said:

Doug,

             It certainly is interesting and with light pollution it doesn't really matter you can still get out and split them. 

I think I have done a 1.1° split in very good seeing conditions I may get 1° but that would be exceptional. 

I'm pretty sure I am getting a new mount and then save for a Skymax 150 Pro if I have a windfall I may go for the 180 that should put me on par with your 8se I think. 

Paul 

 

Paul - Yes, the 8SE is good for doubles.  I must say I think the 10" Dob is a bit better for sharpness, but it hasn't got the GoTo, so it's hard to keep on target at the high mags required for tight doubles.

Talking about windfalls - when mine comes, I'm getting a CPC 1100 DeLuxe GoTo SCT.  That should sort out the tight doubles!  Dream on.....

Doug.

Edited May 15, 2021 by cloudsweeper

[Stu]

Just now, cloudsweeper said:

but it hasn't got the GoTo, so it's hard to keep on target at the high mags required for tight doubles.

EQ Platform?

[cloudsweeper]

5 minutes ago, Stu said:

Do you think LP also played a role in this one being difficult Doug?

Nice set of observations, interesting read, thanks 👍

I wouldn't say so Stu, after all, I could quite easily see 12th mag stars nearby.  The seeing was pretty good, as I went to x254.  I put it down mainly to the large delta-mag.

Doug.

[Stu]

5 minutes ago, cloudsweeper said:

I wouldn't say so Stu, after all, I could quite easily see 12th mag stars nearby.  The seeing was pretty good, as I went to x254.  I put it down mainly to the large delta-mag.

Doug.

Makes sense Doug. I just wondered because I do struggle to see some of these unequal pairs and have wondered if LP was a factor. As you say though, if you could see fainter stars ok then seems not. Thanks!

[cloudsweeper]

14 minutes ago, Stu said:

EQ Platform?

So tracking on one axis could be a bit easier.  My first 'scope was on a EQ, and I didn't take to it.  No - I want a large aperture GoTo on Altaz, when I come up on th' horses!  😉

Doug.

[Stu]

18 minutes ago, cloudsweeper said:

So tracking on one axis could be a bit easier.  My first 'scope was on a EQ, and I didn't take to it.  No - I want a large aperture GoTo on Altaz, when I come up on th' horses!  😉

Doug.

An EQ platform gives you tracking full stop for about 45 mins at a time, otherwise the scope basically performs as an alt-az. Might be an interim solution until your horsey comes in! 😀🐴🐴

[wookie1965]

There is a nice 10 inch goto dob for sale if I had the money I'd get that.