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  #1  
Old 06-09-2017, 08:58 PM
Tropo-Bob (Bob)
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Epsilon Lyra- various scopes.

I have been casually observing Epsilon Lyra (the Double-double), which is often used in test reports on telescopes as a proof of satisfactory optics. So with a Full Moon tonight, I thought I would use it to test the performance of a number of small scopes. In all these scopes, the easier pair was also clearly split, but not always so with the tighter pair.

The splits were easy with an Orion Triplett (80mm, F6 (FL 480mm)) and a William Optics diagonal and a 5mm Delite EP (95x). This gave the best view of all the scopes as it distinctly split both pairs and really was a pleasure to view.

Both pairs were also split with a Vixen achromatic (80mm, F11.4 (FL910mm)) and a TeleVue diagonal and a 9mm Tak Ortho EP ( 101x). The more difficult double had the fainter star situated in the primaries diffraction ring. It could also be spilt with a non-branded 10mm Plossl.

Using a TeleVue Ranger (70mm, F6.8 (FL 480mm)), it was a shade more difficult again to see the split of the tighter pair. I again used the 5mm Delite, but with a televue diagonal.

Using a cheap Skywatcher 70mm achromatic ( F12.9, 900mm FL) was interesting as I could only sense a slight elongation with a non-branded diagonal, but could see this much more clearly when changing to a TeleVue diagonal. I used the 9mm Tak Ortho. However, it did split the fainter pair when I used a non-branded 7.5mm plossl (with the TeleVue diagonal)

I also tried my vintage 60mm (F15) Unitron. It gave a better sense of the tighter pair being double than did the skywatcher with the non-branded diagonal. I used a genuine 9mm Unitron Ortho. I tried higher powers, but still did not split the fainter pair. Only on putting it away did I notice that the Unitron diagonal looked liked it needed cleaning, so maybe this was not a fair test.

The other evening, I did use a 10" Dob to split both pairs at around 100x. However, I thought the view was ordinary (not crisp) and really prefered the view through the first 3 scopes tonight.
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  #2  
Old 07-09-2017, 03:14 AM
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For me, the 80mm f/6.5 achromat shows Epsilon nicely in four stars with a Vixen 6mm (85x). No problem with that, but the star reaches higher in the sky here (70) than in AU.
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  #3  
Old 07-09-2017, 07:10 AM
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Merlin66 (Ken)
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How low can you go..

An interesting experiment is to see what minimum magnification you need to still definitely split the double double.
I have managed to see them with x49 on the Genesis......
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  #4  
Old 07-09-2017, 03:54 PM
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Tinderboxsky (Steve)
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Interesting experiment Bob. Variation of the Sissy Hass double star project.
It is obviously very low in my skies and I have not been able to split the finer pairs to date. Plenty of colour in the main pair but there is just too much atmosphere to peer through unfortunately. I do keep revisiting it when near culmination trying to catch a lucky patch of exceptional seeing.
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Old 07-09-2017, 04:34 PM
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Atmos (Colin)
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I really should get a double star chart so that I can do some playing with 4" F/9, can binoview it all at 77x
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  #6  
Old 07-09-2017, 07:22 PM
Tropo-Bob (Bob)
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Quote:
Originally Posted by Merlin66 View Post
An interesting experiment is to see what minimum magnification you need to still definitely split the double double.
I have managed to see them with x49 on the Genesis......
I tried again tonight with my Vixen ED115mm (F7.7 FL890mm). I used increasing powers of magnification till I cleanly split both pairs with an 11mm Nagler (81x).

Ken, well done with the Genesis. What latitude did U make your observation from?

I see Cloudy nights had a thread where people were trying to split all 4 stars with low magnification.
https://www.cloudynights.com/topic/1...double-double/
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  #7  
Old 07-09-2017, 07:43 PM
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Merlin66 (Ken)
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Bob,
I was observing from Belgium, about 52 deg north.
IMHO it all comes down to practice, practice, practice.......
It's very interesting to observe things that were previously difficult or almost impossible.
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  #8  
Old 07-09-2017, 07:48 PM
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Merlin66 (Ken)
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A note, it's always easier to work downwards in magnification to find the limit....
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