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Using spotting scope zoom eyepiece


bomberbaz

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I have seen a few times on hear a mention of the Leica Zoom and that it is a cracking zoom, but the only one I have seen is a spotting scope zoom.

I did a bit of looking around (far too much spare time these days) and found there are a lot of spotting scope zooms from some notable providers such as Nikon, Swarovski and similar but do these make a suitable companion for an astronomy scope.

For one you have to get one with a bayonet 1.25" fitting although I have no doubt a connection could be made with the various adaptors available these days.

Two is the specifications used by these providers for spotting zooms bear no resemblance to the enticements, sorry I mean descriptions 😂 we see for dedicated astronomy eyepiece.

I know zooms are generally quite tight in AFOV when compared to some of the ultra wide astro glass, so nothing new there in that the spotting variety seem to be of a similar disposition.  But what is the difference, if indeed any to astronomy mainstream zooms such as a Baader MkIII?

cheers

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Mostly better lens polish, coatings, and stray light control.  Most folks positively compare the Leica ASPH to the Pentax XW and Delos lines for sharpness and contrast.  There's also a Zeiss zoom with a wider range that is also well received for similar reasons, if just a bit behind the Leica image fidelity-wise.

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They are mostly pretty good for astronomy. The Leica ASPH really broke through into astronomy because apart from excellent optics, it offered a wide field throughout the range of powers, and it was sold with adapters for 1.25” diagonals by APM and Starlight (with Starlight being by far the best, though pricey). I’ve read good things about Swarovski zooms in telescopes. The Pentax zooms were developed for spotting scopes, and although the XF zoom is poor for nighttime astronomy, the XL zoom is used by lots of stargazers. Other names like Kowa and Meopta sometimes crop up on astro forums. And of course it works the other way - the current Baader zoom is used a lot on spotting scopes. The biggest drawback with the Leica I found was its limited range (9-18mm roughly), yet adding a barlow for more magnification  was a bit of a pain, and not something you wanted to do out at night. But it was a beautiful eyepiece, as Louis said keeping pace with Delos/XW.

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Got first light on my new Nikon MCii ebay purchase last night. It’s 7-21mm and barlowed fine. I’ve had it a while but it wouldn’t reach focus until i found a way to shorten the focuser stack with a low profile Baader ep holder.

I’d say it’s a cracking little ep- fairly narrow fov (40-60deg) but it’s nice that it expands as you zoom to higher mags. It displayed no annoyances like colour fringing and was sharp pretty much across the whole field. I didn’t once feel like i should swap to an ortho to get a sharper view- it seemed plenty sharp. No flaring or annoying reflections either.

I used a 23.2mm (microscope ep) to 1.25” adapter with a bit of tape to make it a tight fit on the nose of the MCii. 

DD52F5E1-DADD-49DC-91D0-A39E76F4C0A6.thumb.jpeg.2a709430c81f58b547c21365ba2e3cad.jpeg

0BE6A628-A74D-4F9D-B0F5-507DEA042428.thumb.jpeg.1731b8e68695bdd080f9b3b49628ce5c.jpeg

Mark

Edited by markse68
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Found this older thread comparing the older MC very favourably with the Leica asph zoom alluding to its excellent scatter control making it very fine for planetary as I found out last night. Wider view of the Pleiades (didn’t fit completely with my 750mm fl) wasn’t so good but i’ve yet to find a good ep for that target- always looks better in the finder haha. Not sure if it’s the scope or my eyes but lots of coma/astigmatism at edge of field.

Mark

Edited by markse68
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1 hour ago, markse68 said:

Found this older thread comparing the older MC very favourably with the Leica asph zoom alluding to its excellent scatter control making it very fine for planetary as I found out last night. Wider view of the Pleiades (didn’t fit completely with my 750mm fl) wasn’t so good but i’ve yet to find a good ep for that target- always looks better in the finder haha. Not sure if it’s the scope or my eyes but lots of coma/astigmatism at edge of field.

Mark

Pleaides would be excellent with a 30mm eyepiece that has no astigmatism, like an APM 30mm Ultra Flat Field--2.77° with a 750mm focal length.

Coma can only be solved with a coma corrector.

If the astigmatism is in your eye, you'll see it in the center of the field as well as the edge.  If only at the edge, it's the eyepiece

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1 hour ago, Don Pensack said:

Pleaides would be excellent with a 30mm eyepiece that has no astigmatism, like an APM 30mm Ultra Flat Field--2.77° with a 750mm focal length.

Coma can only be solved with a coma corrector.

If the astigmatism is in your eye, you'll see it in the center of the field as well as the edge.  If only at the edge, it's the eyepiece

can’t do the 30mm Don as it’s a 1.25” focuser that i don’t really want to change. I was thinking a 16mm T5 nag might just fit it all in but it’s a lot of money for one target! The best i’ve got is my vintage 19mm TV WF- it mostly gets it all in but with no room to spare and it really needs a border to make the most of it i think. The smaller exit pupil helps- pretty sure my eyes are astigmatic- really need to go get them tested. Darker background from shorter fl is nice too.

Mark

PS while we’re off topic, in 1.25”, 24mm UFF or HD-60 25mm?

Edited by markse68
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5 hours ago, markse68 said:

PS while we’re off topic, in 1.25”, 24mm UFF or HD-60 25mm?

Depends on your budget and ability to find the Meade used.  The 24mm UFF has a significantly wider TFOV (27.5mm FS) than the 25mm HD-60 (24.9mm).  It also has better edge correction, although the very edge sort of fuzzes out because the design was pushed too far.  Sharpness-wise, they're similar.  Usable eye relief is similar in both.  The UFF weighs 12.2 ounces while the HD-60 weighs 7.5 ounces.  Since I have 2" focusers, I much prefer the 22mm AT AF70 (Omegon Redline SW) at that TFOV and power.  It's better than either sharpness-wise across the field with about the same TFOV (28.6mm FS).  Oberwerk sells a 1.25" version singly if you contact them directly.

See below for images at f/6 in a field flattened 72ED:

23mm - 28mm.JPG23mm - 28mm AFOV 3.jpg

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