A Double star challenge Epsilon Lyrae.

[Stu]

It’s definitely a good challenge, and one I think may well be easier in refractors than newts due to the tighter star shapes.

I think I recall managing it at x55 in the FC-100 but would need to re-verify that.

It is certainly doable in quite small scopes. I’ve managed it in my TAL Alkor 65mm best, Zeiss Telementor 63mm f13.3 frac and the smallest was a Tak FS60C, 60mm apo doublet.

[Pixies]

31 minutes ago, Saganite said:

Well, I guess based on this, and John's excellent chart, I didn't split them but  merely resolved them, though at the time I certainly felt that I had. With a difference of  13x magnification it would have been a very fine line.....

At 68x I split one pair and resolved the other - using that excellent graphic to describe the difference.

[SiriusB]

11 hours ago, John said:

Last night I managed to split both pairs of Epsilon Lyrae with a 90mm F/11 refractor (cheapie !) at 74x. I was using a 7.2- 21.5mm zoom and gradually adjusting until I could just see the thin black gap between the star pairs.

I got Pi Aquilie with the scope as well but that needed 180x !

I use these guidelines when I'm working out whether I've got a split or not although I sometimes also throw in the terms "snowman" and "peanut" because that's what not-quite split sometimes looks like !

The above pairs were clearly "split" to me last night (and a few others too):

Thanks John,a good graphic, "split" is what we're looking for i think,less open to interpretation?

[SiriusB]

With large aperture or fast achro, maybe you could use a filter to dim/ or clean up the view?

It's not cheating~

I think that's what proper double star observers do when pushing the limits, bung in a green filter or something.

Won't help here, i don't posess one.

[John]

If filters are used the optical quality needs to be good enough that nothing undesirable is added to the view, eg: light scatter. Splitting tight doubles is a test of the whole optical system, and the observers eye !

Personally I have not found that filters help with double star splitting - even the really challenging ones such as Sirius.

People do use green filters for star testing scopes because you get a cleaner definition of the airy disk and diffraction rings.

 

[Whistlin Bob]

Well this is a good bit of fun for a moonlit cloud dodging type of evening- encouraged me to get the little scope out.

With etx105 mak and Baader 8-24 zoom and using the excellent guide above it was notched at 18mm (81x) and definitely split at 15mm (97x).

Very pleasing 😁

Next time I'll try it with the 14" dob...

Whilst I'm on here- lovely views of Jupiter and Saturn (despite altitude) with Jupiter showing 4 bands clearly. Saturn was a bit more of a struggle- hints of the Cassini division, but not really clear. I also split Izar and Iota Cass and had a nice view of Plato and Montes Jura on the moon. It's the first outing for the mak in over a year. Nice to have a scope you can pick up and wander round the garden with...

[John]

Got the split of Epsilon Lyrae with a Celestron 90mm mak-cassegrain at 90x tonight. Lower and the slightly wider pair stayed split but the closer pair became heavily notched but not quite split.

These little scopes are a lot of fun !

 

[markse68]

I had a go at the double double tonight- it’s been ages since I last looked at it. I had a clean split at 80x with my 20mm ep and it was split at 64x with my 25mm ortho but I find with bright stars and longer fl eps that I get a kind of flaring almost like astigmatism and i’m not sure what’s the cause- it may be my eyes I guess. It’s not the star shapes as such but some optical anomaly i think that prevent splitting at lower powers

[John]

4 minutes ago, markse68 said:

I had a go at the double double tonight- it’s been ages since I last looked at it. I had a clean split at 80x with my 20mm ep and it was split at 64x with my 25mm ortho but I find with bright stars and longer fl eps that I get a kind of flaring almost like astigmatism and i’m not sure what’s the cause- it may be my eyes I guess. It’s not the star shapes as such but some optical anomaly i think that prevent splitting at lower powers

What scope were you using Mark ?

[Ibbo!]

I did it some years ago with the FS60 with less than x50 and it was not just me 3 out of the 5 of us anged it .

Now I have the scope back I will see how I do 20 years on.

[markse68]

9 minutes ago, John said:

What scope were you using Mark ?

It was my old faithful 8” f8 dob John

[chiltonstar]

7 hours ago, John said:

Got the split of Epsilon Lyrae with a Celestron 90mm mak-cassegrain at 90x tonight. Lower and the slightly wider pair stayed split but the closer pair became heavily notched but not quite split.

These little scopes are a lot of fun !

 

Small can be fun! I used my ED80 on my Vixen Porta2 to split it at x110; the easier pair split at x80, but it needed more for the more difficult unequal pair. I then moved the mount and scope into a nearby field to have my first look of the season at Mars as it rose. No detail, but always a thrill.

Chris

[Surreydocker]

I'm a complete novice with a 102mm F7 refractor and by chance, I had a go at this on Wednesday night at 100X and failed.

Yesterday, a 4mm Nirvana arrived though the post and last night, at 180X I could clearly split both pairs, so I went back to 100X and I could see that they might be doubles but couldn't honestly split them.

I put it down to inexperience and old eyes !

 

[Stu]

5 minutes ago, Surreydocker said:

I'm a complete novice with a 102mm F7 refractor and by chance, I had a go at this on Wednesday night at 100X and failed.

Yesterday, a 4mm Nirvana arrived though the post and last night, at 180X I could clearly split both pairs, so I went back to 100X and I could see that they might be doubles but couldn't honestly split them.

I put it down to inexperience and old eyes !

 

It could also be the seeing conditions which for me were not very good last night. Keep trying and you may find a steadier night lets you split them at the lower power.

[RobertI]

From memory I believe I managed to just split* both pairs last week with my 66mm frac at around 110x (zoom ep at 8mm + 2.25x barlow). The split was very easy at 174x. Next time I will ‘zoom out’ to see how low I can get. 
 

* I will have another go to confirm whether the closer pair was really split or just well resolved. 

Edited July 31, 2020 by RobertI

[harpy]

Looking like partly cloudy skies here tonight going by the forecast. So might give this a go tonight if there's some clear sky..

[Stu]

On 31/07/2020 at 20:22, RobertI said:

From memory I believe I managed to just split* both pairs last week with my 66mm frac at around 110x (zoom ep at 8mm + 2.25x barlow). The split was very easy at 174x. Next time I will ‘zoom out’ to see how low I can get. 
 

* I will have another go to confirm whether the closer pair was really split or just well resolved. 

Definitely doable in a 66mm Robert, so I would be fairly confident you did it.

[Sunshine]

I want to give this a shot tonight but, I’m limited by my eyepiece selection.

[Pixies]

2 minutes ago, Sunshine said:

I want to give this a shot tonight but, I’m limited by my eyepiece selection.

Likewise, but I'll give it a shot too.

Does LP from a full moon affect the splitting of doubles?

[Sunshine]

32 minutes ago, Pixies said:

Likewise, but I'll give it a shot too.

Does LP from a full moon affect the splitting of doubles?

I really can’t see LP from the full moon affecting double splitting, I would be surprised to hear otherwise.

[Pixies]

11 minutes ago, Sunshine said:

I really can’t see LP from the full moon affecting double splitting, I would be surprised to hear otherwise.

I need all my excuses ready now

[John]

1 hour ago, Pixies said:

 

Does LP from a full moon affect the splitting of doubles?

It can impacts double stars where one component is very, very dim simply because the dim star is washed out. Otherwise, makes no difference.

One "quite interesting" factoid on Epsilon Lyrae is that the gap between the slightly easier pair is 2.4 arc seconds which is about the same as Neptune's apparent diameter at the moment. So when you are admiring the split and that tiny sliver of blackness between the stars you can imagine how small Neptune is in the eyepiece 

 

[Pixies]

OK - I gave it a shot tonight. I split both at 100x but could only split one at 67x - the other being a 'snowman'. 

I find it hard to confirm the split - it's almost as if my vision is blurring, a bit like floaters smudging the clarity of the stars. Is this my eyes or the viewing conditions?

Later, I tried Iota Cass for the first time. The triple is very beautiful and I managed to split the tighter pairing at 100x. It seemed much easier on the eyes, perhaps because of the colour differences.

 

So, I need a 15mm EP next, to give me 80x. Or perhaps a bit of overtime is required and I'll look to get a Baader Hyperion Zoom

[John]

Zooms are great for double star splitting. I use one practically all the time now for that purpose. Either the 7.2mm - 21.5mm plus 2.25x barlow or the Nagler 2mm - 4mm zoom.

 

[Barry-W-Fenner]

8 minutes ago, John said:

Zooms are great for double star splitting. I use one practically all the time now for that purpose. Either the 7.2mm - 21.5mm plus 2.25x barlow or the Nagler 2mm - 4mm zoom.

 

What barlow do you use John? I might upgrade mine with one that is more user friendly with my Morpheus.

 

Cheers