ED72 ~ A Review

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ED72 ~ A Review

Postby Nightspore » Sun Sep 08, 2019 4:42 pm

I’m physically disabled, so small, light and easily set up scopes tend to get more use. Notwithstanding the vagaries of the weather and available observing windows. My main grab and go rig was a modified (aftermarket rotating focuser) ST80 mounted on a Sky-Watcher AZ5. This was perfectly fine for rich field and occasional lunar and planetary observing. Any CA could be ameliorated with filters and the two-speed GSO Crayford enabled fine focusing. The Crayford made the ST80 rear heavy however and I had to swap the 2” accessories I originally used with 1.25” ones. This was especially true with the ST80 mounted on the AZ5 as I could use 2” EP’s with the Porta II fairly easily. I sometimes needed to use an extension tube to achieve focus.

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September last year I decided to invest in a Sky-Watcher Evostar 72ED DS Pro. The price was good (I actually have eyepieces that cost more), although it came with no accessories. It didn’t even include a 1.25” adapter. It was supplied with a case though.

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(2” Baader diagonal shown is my addition)

The doublet consists of a Schott crown but the actual flint element composition hasn’t yet been revealed by Synta. It is very possibly H-FK61 glass made by CDGM in China, which is reputedly very similar to the Japanese made Ohara FPL-51 glass.

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The OTA has a typical Sky-Watcher Black Diamond finish and the two-speed focuser is precise and very well made. I thought the finder shoe screw could be smoother but it does its job. The OTA has a detachable dewshield with a metal threaded dust cap and the objective appears well coated.

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At 23:30, 05/09/18, 2018 BST the ED72 was all set up. I had no dew control apart from an Omegon flexible dew shield as an extension to the Evostar’s own integral shield. There was light cloud and the transparency was below average with humidity at around 80%. A 2“ Baader Amici was in the focuser together with a 36mm Baader Hyperion Aspheric giving 11.6x and 6 arc degrees of TFOV.

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First light target was Albireo, and the two stars looked like beautiful jewels hanging in space. The colours and overall colour separation of the Evostar were exquisite. So far, so good. Next up was the Veil Nebula with a 2“ ES broadband OIII filter. This was one of the best views of the Veil that year and it was nice to use the 2“ EP’s after a year or so of neglect. I had no problems with balance or weight distribution and even rotating the diagonal wasn’t a real problem. I spent some time in the Summer Triangle (without the OIII) and I had some impressive views. I turned my attention to Cassiopeia and Perseus and all of the rich open clusters around the region. At around 00:36 while I was scanning around Triangulum I saw what appeared to be a formation of a dozen or so artificial satellites travelling towards the south. Eventually I decided to give the 19mm Celestron Luminos a spin. This 2“ EP weighs about a metric tonne and is very shiny. The Double Cluster looked very good on axis at 22.1x but the slight avian astigmatism perceivable in the ST80 was still there. Albeit now nearer the edge of field, I’d hoped the f/5.8 focal ratio might have ameliorated the seagulls somewhat. Undaunted, I had a good re-sweep of much of what I’d observed earlier with the 36mm Baader and found that the Luminos isn’t a terribly unmanageable eyepiece on the ED72.

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I returned to the 36mm Hyperion for a butcher’s hook at a rising Pleiades. The Andromeda Galaxy looked beautiful even with the bright Moon. I turned back to a low Summer Triangle around 02:00 and decided to try the Double Double. I split the first pair at 60x with a 7mm Sky-Watcher UWA. When attempting to use a Barlow with the 7mm UWA to see all four stars I discovered that I couldn’t achieve focus. As I was pondering this it was about 02:30 and the Altair RDF had dewed (the objective was completely dew free) and I was well knackered, so I decided to call it a night. It turns out that with eyepieces or eyepiece combinations with focal lengths of less than around 3.5mm a 1.25” diagonal was needed. The focal plane can vary with particular diagonals and is really a process of trial and error.

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After over a year of using the ED72 I’m still pretty impressed with it. Although I now mount it on a Vixen Porta II again, but with a Vixen Polaris tripod, plus the OTA is now fitted with an aftermarket visual back featuring a compression ring.

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I’ve had sharp magnifications of the Moon between around 160x to over 180x with no discernible CA. Jupiter and Saturn have shown a lot of detail anywhere between 100x and 140x, and in good conditions I’m sure higher could be achieved. It comes into its own as a rich field scope but it really is a quite flexible and adaptable ‘Jack of all trades’. In February, on my birthday, when I realised the weather would allow me to take a scope out for the first time this year, it was the ED72 that I chose.

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Nightspore
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Re: ED72 ~ A Review

Postby AstroChris » Sun Sep 08, 2019 7:40 pm

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Re: ED72 ~ A Review

Postby Nightspore » Sun Sep 08, 2019 8:33 pm

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