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Old 06-09-2017, 08:58 PM
Tropo-Bob (Bob)
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Join Date: Sep 2013
Location: Cairns
Posts: 1,584
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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