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Eyepiece suggestions for a 102 triplet

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#1 Neinball

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Posted 13 May 2021 - 02:59 AM

So I'm primarily an imager but lately I've gotten into observing as well and am wanting to get a set of eyepieces for a 102/714mm triplet, I'm trying to figure out what would give me a good magnification for lunar and casual planetary, or at least as good as can be for a scope of that class. Would I be right in thinking a 15mm + 2x Barlow would give me solid views or would I need to go for say a 10mm or higher mag EP? And is there a design that has enough eye relief at that power that I won't be stabbing myself in the eye to see into it like most kit eyepieces?

Edited by Neinball, 13 May 2021 - 03:01 AM.


#2 Ben the Ignorant

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Posted 13 May 2021 - 03:57 AM

Your triplet focuses light along an f/7 beam so the large magnifications of lunar and planetary gazing are obtained with eyepieces of half that number, 3.5mm focal length or so. The 110° Myriad or the Teleskop Service and APM clones would be great, they have only a very small amount of the usual shortcomings, very balanced performance and high performance, to boot.

 

This is an informed advice as I own the 9mm, 5mm and 3.5mm, all great and all affordable for the huge field they provide and the quality of its correction. My scope set includes an f/7 semi-apo, an f/6 triplet and recently grew with an f/7 115mm triplet, the Myriads just do everything right in all scopes. The 5mm would be a worthy colonel when general 3.5 can't operate because of turbulence.

 

But of course some very sharp and reasonably wide eyepieces are on the market in similar focal lengths, and they cost less if the ultrawide experience is not at the top of your observing priorities. But other forum members know them better than I do.



#3 Neinball

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Posted 13 May 2021 - 09:35 AM

Awesome I'll check those out thanks.

#4 Starman1

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Posted 13 May 2021 - 01:50 PM

So I'm primarily an imager but lately I've gotten into observing as well and am wanting to get a set of eyepieces for a 102/714mm triplet, I'm trying to figure out what would give me a good magnification for lunar and casual planetary, or at least as good as can be for a scope of that class. Would I be right in thinking a 15mm + 2x Barlow would give me solid views or would I need to go for say a 10mm or higher mag EP? And is there a design that has enough eye relief at that power that I won't be stabbing myself in the eye to see into it like most kit eyepieces?

I have an identical scope.

I find that 62°-65° eyepieces yield nice large true fields at near every magnification.

I am running the following eyepieces in the scope:

3mm, 4mm, 5mm, 7mm, 9mm, 11 or 13mm, 15 or 18.2mm TeleVue Delites and a 24mm APM Ultra Flat field.

All are usable with glasses and have long eye relief (otherwise I'd use a 24mm TeleVue Panoptic) and all are close to the same exact focus, and all are lightweight so no rebalancing is necessary.

I'm happy with 2.2° as a lot power view (though the scope can provide a larger view if desired), and the highest power, 238x, still has a 15' field, half as wide as the Full Moon.

There is always an appropriate magnification for every object.

You could create the high powers with a lower power eyepiece and a Barlow, and that could work quite well.  I wanted to keep the weight in the focuser to a smaller level.

And fortunately, these eyepieces came along.  I find them superb for lunar, planetary, double star, planetary nebulae, globular cluster use because they are so sharp.



#5 Ben the Ignorant

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Posted 13 May 2021 - 02:20 PM

I was so enthusiastic about the Myriads it made me forget other eyepieces I own, a 4mm/82° with generic but good optics that are sold in various housings, some fogproof, some not fogproof; a 20€ or 20$ difference could be due to this. It's part of a set of 4mm, 7mm and 16mm that many large optics stores sell under many names.

 

https://www.firstlig...-eyepieces.html

 

An Explore 4.7/82 in my set is very sharp but it has a little bit of a kink, it enhances chromatism in refractors, the semi-apo begins to look like a much improved achro, and the full apo looks like a top-end semi-apo. The effect is subtle and does not remove the eyepiece from its high grade pedestal, you could ignore the effect and just be aware of it as eyepiece trivia.

 

Having 5mm, 4.7mm, 4mm and 3.5mm focal lengths permits tayloring the magnifications (of several telescopes) to the highest value that air conditions will allow.



#6 SeattleScott

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Posted 13 May 2021 - 04:12 PM

You want something in the 3-4mm range. Lots of options, from the 3.7mm hyperwide mentioned to minimal glass options like TOE 3.3, to a 3-6mm Nagler zoom. Just depends on what you want, widest AFOV, maximum contrast, flexibility to dial in precise magnification to match seeing conditions, etc.

Scott

#7 cst4

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Posted 13 May 2021 - 04:59 PM

My main scope is a doublet of same specs. I typically go out with about 5 eyepieces a night somewhere between about 30mm and 3.5mm. Only 1 longer than 15mm the rest higher power.

 

TV Delites are great in this scope.  Nice size, very comfortable, very sharp.  Sometimes I go out with only my 18.5mm, 7mm, 4mm Delites and am perfectly content.  I recently picked up a 3mm Delite but have not tried it out in this scope yet.  I think it will be able to handle the power but likely not much more.  It will be for planets and double stars. TV T6 Naglers are also quite nice with big views in a small package, but admittedly less comfortable to me than Delites.  They are hard to beat if you don't need long eye relief.  

 

I probably use Morpheus eyepieces the most in all my scopes.  In this scope I use a 30mm UFF for low power, then 12.5, 6.5, 4.5mm Morpheus, then 3.5mm Delos.

Or sometimes instead of the Delos I use a 3.5mm APM XWA which is 110 degree. I do not think it is as sharp as the Delos but the extra drift time is wonderful when going manual. If you use a tracking mount then wide AFOV is not that necessary.

 

I also use a 4mm Nirvana like was linked above quite a bit.  It's a decent eyepiece, but I mainly like it because I find 4mm to be a wonderful high mag in this scope that is never degraded by seeing.  3.5mm is great but sometimes not as clear as a 4mm.

 

Good luck on your decisions!




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