Splitting Double Double Lyrae

[Piero]

I was able to detect the two pairs at 103x, although the separation was more obvious at 206x.

Very nice star system. I was impressed. 

How much magnification do you generally use for splitting epsilon 1 and epsilon 2 with your telescope(s)? 

[Stu]

I was able to detect the two pairs at 103x, although the separation was more obvious at 206x.

Very nice star system. I was impressed.

How much magnification do you generally use for splitting epsilon 1 and epsilon 2 with your telescope(s)?

This will get them going Piero

I believe the lowest I've read about is around x50 - Ken (Merlin66) with his Genesis.

I've managed splits at a little above this, x55 or x60 if I remember correctly, in a 4" scope. Must try the Tak 100. I think I managed at a similar level to you in my WO66.

I generally prefer to see the splits more clearly so would use anything from x100 upwards. I like sharp stars and a nice clear black gap :-)

Sent from my iPad using Tapatalk

[Piero]

mm.. that's interesting! I will try with the 5mm next time. That is 72x. I doubt I can split them at ~50x. There might be a 'hint' of double star at that magnification but I am a bit sceptical it will be sufficient after trying at 103x. But who knows of course  

[cotterless45]

X48 with 25mm Bst in 150 achro f8. I didn't notice it until LeeB pointed it out.

Nick.

[chiltonstar]

Best for me (Mak) is about x150 to x250 to show the Airy disks and diffraction rings most clearly. Below x100, it's obviously a pair of doubles but the rings don't show clearly to me.

I was looking at Epsilon Lyrae and Zeta Her last night from my garden, moving the scope around to different positions. Interesting how clean the split was with the scope on grass cpd with concrete, which was very much less cleanly split!

Chris

[Piero]

Best for me (Mak) is about x150 to x250 to show the Airy disks and diffraction rings most clearly. Below x100, it's obviously a pair of doubles but the rings don't show clearly to me.

I was looking at Epsilon Lyrae and Zeta Her last night from my garden, moving the scope around to different positions. Interesting how clean the split was with the scope on grass cpd with concrete, which was very much less cleanly split!

Chris

Similar thing. At 103x the rings were almost overlapped. I could see that there were 2 pairs but this was not obvious. At 206x the separation was clearly there. Should have said that I observed at 11pm and the sky was not dark yet. Plus the moon was there too. Although this does not really affect at 206x due to the very small exit pupil, it does a bit at 103x I think. 

Interesting you find differences between observing on grass or concrete. Do you think this is due to vibration dumping or turbulence in the nearby air (released by concrete) or.. ?

I cannot test this one as I always observe in a field. 

[Roy Challen]

I got a definite split with an ED70 and 7.5mm TMB Pl 2. I was surprised, but the sky was reasonably dark and seeing was good.

[chiltonstar]

Interesting you find differences between observing on grass or concrete. Do you think this is due to vibration dumping or turbulence in the nearby air (released by concrete) or.. ?

I cannot test this one as I always observe in a field. 

The old textbooks usually say to avoid putting your scope on a hard surface to prevent thermals - grass is the best.

[YKSE]

I got my first clear night in weeks, and what a bright night, not even the main stars in Cygnus were naked eye objects in midnight.

The split in 120ED was 64x with 14mm, and in 80ED was 60x with 10mm BCO. seeing was reasonably steady, 6mm BCO with 2.25x barlow showed almost none-broken diffraction rings.

I prefer to find out the lowerest possbile split in observing double, with just black line between the stars, and work my way up from low mag.

[Piero]

From wikipedia (http://en.wikipedia.org/wiki/Epsilon_Lyrae):

"The component stars of ε1 have magnitudes of 4.7 and 6.2 separated by 2.6" and [...] the component stars of ε2 have magnitudes 5.1 and 5.5 separated by 2.3". " 

Unfortunately it is not specified whether these measures are based on Dawes or Rayleigh formula. 

Apparently my TV60 has Dawes resolution of 1.93" or Rayleigh resolution of 2.33", so these doubles are almost at the limit in my case.

Curious to try with a 5mm in a moon-less night. 

[chiltonstar]

From wikipedia (http://en.wikipedia.org/wiki/Epsilon_Lyrae):

"The component stars of ε1 have magnitudes of 4.7 and 6.2 separated by 2.6" and [...] the component stars of ε2 have magnitudes 5.1 and 5.5 separated by 2.3". " 

Unfortunately it is not specified whether these measures are based on Dawes or Rayleigh formula. 

Apparently my TV60 has Dawes resolution of 1.93" or Rayleigh resolution of 2.33", so these doubles are almost at the limit in my case.

Curious to try with a 5mm in a moon-less night. 

Certainly my ED80 does a good split on both pairs, with clear dark space between, so on a good night I imagine a 60mm frac is up for it!

Chris

[Merlin66]

Observing close double stars can be a lot of fun, challenging and very rewarding.

The Dawes limit is based on the "minimum" contrast difference between almost overlapping Airy Disks.....

This means that the rings will be interfering and when looking a really close star the disks will appear as a "dumbbell" rather than two distinct stellar disks.

Work downwards from your "easy split" magnification, take your time, hold your breath ( to pump oxygen into your brain - trust me it works) and you'll find with practise that it is still possible to distinguish the pair as separate "entities" at much lower magnifications.

I used a 10.4mm plossl on the 4" f5 Genesis.

Try it.

[Stu]

From wikipedia (http://en.wikipedia.org/wiki/Epsilon_Lyrae):

"The component stars of ε1 have magnitudes of 4.7 and 6.2 separated by 2.6" and [...] the component stars of ε2 have magnitudes 5.1 and 5.5 separated by 2.3". "

Unfortunately it is not specified whether these measures are based on Dawes or Rayleigh formula.

Apparently my TV60 has Dawes resolution of 1.93" or Rayleigh resolution of 2.33", so these doubles are almost at the limit in my case.

Curious to try with a 5mm in a moon-less night.

You should definitely be able to split these Pierre, I've done it many times with 66mm and 60mm apo doublets.

Because they are relatively similar brightness they are not as difficult as some with similar separations

[Stu]

From wikipedia (http://en.wikipedia.org/wiki/Epsilon_Lyrae):

"The component stars of ε1 have magnitudes of 4.7 and 6.2 separated by 2.6" and [...] the component stars of ε2 have magnitudes 5.1 and 5.5 separated by 2.3". "

Unfortunately it is not specified whether these measures are based on Dawes or Rayleigh formula.

Apparently my TV60 has Dawes resolution of 1.93" or Rayleigh resolution of 2.33", so these doubles are almost at the limit in my case.

Curious to try with a 5mm in a moon-less night.

You should definitely be able to split these Pierre, I've done it many times with 66mm and 60mm apo doublets.

Because they are relatively similar brightness they are not as difficult as some with similar separations

[Mr Spock]

Back in the '70s when I had my Prinz 550 60mm, that would split them. I used to use a 12mm Kellner which was x75 (still have that somewhere).

[YKSE]

Work downwards from your "easy split" magnification, take your time, hold your breath ( to pump oxygen into your brain - trust me it works) and you'll find with practise that it is still possible to distinguish the pair as separate "entities" at much lower magnifications.

I used a 10.4mm plossl on the 4" f5 Genesis.

Is it a way to better use our brains?

Interesting discussions here where 2' to 3' is assumed to be about mininum seperations for somewhat equal doubles.

[Piero]

Thanks a lot all of you for your support! 

Lyra constellation is one of my favourite. So small, but also so rich! 

Observing close double stars can be a lot of fun, challenging and very rewarding.

The Dawes limit is based on the "minimum" contrast difference between almost overlapping Airy Disks.....

This means that the rings will be interfering and when looking a really close star the disks will appear as a "dumbbell" rather than two distinct stellar disks.

Work downwards from your "easy split" magnification, take your time, hold your breath ( to pump oxygen into your brain - trust me it works) and you'll find with practise that it is still possible to distinguish the pair as separate "entities" at much lower magnifications.

I used a 10.4mm plossl on the 4" f5 Genesis.

Try it.

Thanks for your explanation and advices! I agree with you that relaxation is one of the best techniques when observing. I will try it for sure! 

[Piero]

Is it a way to better use our brains?

Interesting discussions here where 2' to 3' is assumed to be about mininum seperations for somewhat equal doubles.

Yong, the link you provided is very interesting. Thanks for linking it to this post. 

It also makes me curious to dig into the maths reported by 'EdZ' properly. Nice way of reasoning about this topic. 

Said this, now I am also curious to test the double double with:  

- Nag 7mm (51x)

- Nag 13mm + Barlow 2x (55.4x)

- Vixen 5mm (72x) 

Don't know the formulae calculating 'visual acuity', but can find these out too  

Will report the results of course. 

[RikM]

64x for me with a 10mm XW in an older TV Pronto.

[Ibbo!]

I have done it with the baby tak 60mm but cannot rem what eyepiece was used

[RLWP]

Back in the '70s when I had my Prinz 550 60mm, that would split them. I used to use a 12mm Kellner which was x75 (still have that somewhere).

This is very encouraging - I'm using a Prinz 550. I'll check my eyepieces and go out appropriately armed next time

Richard

[jabeoo1]

I am certain I split them @ x61 back in the winter aimed more towards the zenith, last night I needed to get up to x106 to see separation. Its really a surprise how tidy that double double system looks. To me they can look like two filled in 8's under certain magnification / conditions.  

[Piero]

Okay, here an update. 

- Nagler 7mm (51x). I could not split the two. The image suggested a possible elongation of the two stars, but this was not obvious. I would not have detected it if I had not known that they are doubles. I carefully focused inward and outward to reach the optimum, but this was not sufficient. 

- Nagler 3.5mm (103x). Just managed to see the two pairs, although the separation was not clear. They appeared just a tiny more than elongated stars. I am not sure, but I suspect this was more due to the Nagler 3.5mm. 

I was silly because I meant to take the 5mm out to also see Saturn at 144x with a barlow, but for unknown reasons I picked up the 3.5mm. The seeing was moderate-good, whereas transparency was medium. I will check this next time.

[philj]

60mm Swift 339 at 70x was a memorable split for me. Up till then I didnt appreciate just how good some 60mm scopes could be.

I usually recommend beginners to try it at 100x ish to guarantee a good split.Yes it can be split much lower but you need to have your "eye in", plus seeing conditions etc

[Piero]

Last update:

Tested it at 72x. The split was there and possibly epsilon1 (the North pair) appeared a tiny bit more separated.

Although it is possible to split this double pair using magnifications below 100x, to me 100x is the minimum for really appreciating it.

Thanks everyone for your comments and help!