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Micro session with tiny scope


Stu

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When I popped out to put the bins out and make the bunnies fox proof last night,  I noticed the sky was very clear and dark ish for round here.

The weapon of choice for this, another of my micro sessions was the Tal Alkor 65mm Light Thimble, on my Ercole mount, and I just thought I would grab a few doubles before my dear lady questioned my absence!

Four doubles; Algieba, Castor, Polaris and finally Izar.

The Alkor has three options for magnification, x33, x88 and x133. I used the lowest as a finder power and them switched to highest.

Algieba is a mag 2.2 and mag 3.6 pair at 4.6" separation. Their colour is listed as orange, but they appeared white to me. For such a small scope, the rendition of the stars is wonderful. Beautiful bullseyes with one diffraction ring. They were clearly separated and the magnitude difference was clear. A lovely sight.

Castor was not dissimilar actually. 1.6 and 3 magnitude with a 5.2" separation, again beautifully resolved as two white, uneven bullseyes.

Polaris was much more difficult, to begin with I didn't think I would get it, but on a few occasions when the seeing stilled I caught the tiny mag 9.1 secondary, right on the limit for this scope under my conditions. The Mel Bartels calculator gives between 8.8 and 9.8 for this aperture under mag 18.5 skies, so I'm confident it was doable.

So finally Izar, a good challenge for the Light Thimble!

Again, when I first looked I couldn't detect the secondary, just an unsteady diffraction ring. However, after careful focussing and observing for a little while it was clear that the secondary was buried in the diffraction ring (I've seen this effect on Izar before) , and was present in the correct position (verified later). One trick I've tried with the Alkor before is to pull the eyepiece out of the extension a little and the extension out of the Barlow. This gives a bit more power, I'm guessing at x150 or x160 and the secondary became clearer once I had done that. I didnt get the same sense of colour as I do with a larger scope with these two, the secondary just looked duller than the primary but I was just happy to get it at all.

This scope really is amazingly sharp, 60 times mag per inch or there abouts is pretty impressive, and the star shapes are way better than many larger dobs I've used. Without making any permanent changes, I've removed this Alkor from its normal mount and fitted it with rings, albeit Munsen rings which are the only ones I could find to fit! Fitted to a short dovetail, it rides on a standard mount very nicely. I've also fitted the shoe for a Rigel finder which makes life much easier than the standard two part rifle sight.

So, another something and nothing report from me, just trying to keep my eye in and enjoy a challenge with whichever scope I manage to get out for 15 mins ?

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Good fun Stu! I use my ED80 for similar quick sessions sometimes when I've got an early night, or we've got guests wanting their glasses refilled. I'm surprised that Algieba was bleached out with the 62mm - with 80mm the pair are definitely orange.

Chris

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7 minutes ago, chiltonstar said:

Good fun Stu! I use my ED80 for similar quick sessions sometimes when I've got an early night, or we've got guests wanting their glasses refilled. I'm surprised that Algieba was bleached out with the 62mm - with 80mm the pair are definitely orange.

Chris

It was Chris, thanks.

I was a bit surprised there wasn't more colour too, same for Izar. Not sure of the reason as the transparency looked pretty good.

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2 hours ago, DirkSteele said:

Sounds like a lovely little scope.  Any photos of the little champ you can share?

It is indeed Matthew. These are the only two I could find, will take some more soon. First is in original configuration, second is after I had put rings on it and was using it on a manual Vixen GP mount. It would be good on a goto actually as often just holding the top of the tube to nudge it creates tube currents which take a few moments to settle.

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Nice report, and lovely little scope. I generally use the APM 80mm F/6 as wide-field scope for shortish sessions, but I might want to try it on double stars as well. I should also blow the dust of the little table-top mini-Dob I built for the kids, collimate it properly and see what it can do.

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The boys don't seem to want to use it. I might donate it to the outreach group of the Kapteyn Astronomical Institute here in Groningen

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Looks a great little scope Michael, would be good for someone to get use out of it. Ideal for children with its low eyepiece height and would be pretty stable I guess.

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