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Yet Another Skywatcher ED80


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But this time it's a brand spanking new DS-Pro model with the older single speed Crayford focuser!

Bought primarily as a travel-scope, quick look terrestrial scope, portable white-light scope, and bought almost entirely because I'd had experience of these fpl-53 80mm f7.5 optics a few times before ;)

So, this is a pic of the scope on day 1 - note the bright dew-shield interior:

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Star tested it the other night and found it to be well aligned (though not quite perfectly, but I suspect strongly that the play in the focuser adapters I'm using contributed to the very small offset I saw). Indoor testing with a reflective Cheshire eyepiece seemed to confirm that. No astigmatism, a small amount of under-correction, but nice sharp colour-free stellar views in focus.

So today I took the thing apart and "did the necessary": Stripped the focuser, lubed and adjusted where necessary; flocked the dew-shield and OTA to first baffle, flat-blacked first baffle and screw-heads inside OTA, slightly loosed the lens retaining ring to "just so", and finally.... cleaned and polished!

Note improved darkness inside dew-shield and OTA:

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The metallic gold-fleck paint is really hard to photograph. These shots are slightly over-exposed to show the flecks, but even so it's far better in the flesh:

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If anyone's got a spare ED80 aluminium case to protect and transport it, I'd be interested... ;)

And yes, I realie that the adapter foot on underside of the OTA will attache to the plate on the AZ3. I had it like that most of the day but was using the rings to rotate the tube for little jobs, and forgot to de-tube and mount it directly! It's pretty portable and easy to use in that configuration. :)

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Ant :D

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  • 2 weeks later...

Has anybody else seen this? When inserting an eyepiece in daylight I get a torus or ring of light around the exit pupil. In my other scopes the ring is non-existent or much less pronounced. Is this normal? I honestly hadn't noticed it before until doing some daylight viewing with this scope...

ekrijd.jpg

Ant

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Yes indeed, Jim. Two different diagonals and several different eyepieces. Here's a snap of the same eyepiece in a different scope: 60mm f13.5.

15cizrd.jpg

As you can see, there is still a hint of torus but it's a lot less noticable.

I have flocked the dewshield and inside the 80ED OTA to first baffle, and the only ring of light I can see inside the OTA is looking in from the rear with no diagonal or eyepiece in place. I can just make out a bright rind around the objective. Does this mean the first baffle is not placed forward enough perhaps?

Ant

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I see what you're saying about the baffle position, couldn't you test that out though by making a longer dew shield and trimming the light cone that way?

What gets me wondering about eyepieces is if the thing isn't properly baffled then it could be scatter from unsufficiently baffled light cone hitting shiny bits on diagonal or eyepiece. In the higher fr scope it would be reduced due to the area of the light down the eyepiece end

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Well, the diagonal is flat blacked (including leading edge of nosepiece) so I don't think anything's reflecting off that.

How does extending the dew shield trim the light cone? I don't follow that I'm afraid.

The longer (and smaller) refractor is indeed baffled too.

What I might do tomorrow is make a paper baffle of slightly smaller diameter and sit it in front of the first baffle to see if that blocks the ring of light I'm seeing. If that works, then the baffle will be at fault and I can then work around it (not that I should need to on a new scope, mind you...)

Thanks for the thoughts,

Ant

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