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In need of a good 2" wide field eyepiece, ca.85GBP/115 EUR


uhb1966
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I am primary an astrophotography guy, but for those special moments, i'd like an 2" EP with a good bang for the buck .

Maybe sth like

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p4921_TS-Okular-Expanse-3-5-mm-Weitwinkelokular-1-25-und-2-Zoll-Anschluss.html

or

http://www.teleskop-express.de/shop/product_info.php/info/p957_TS-WA38-ERFLE-Weitwinkel-Okular---38mm---2----70--Gesichtsfeld.html

However, there seems to be an issue with an 38er/32er EP in connection with a fast f4 scope like mine ?

Who could share some insight?  Thanks in advance!!

Edited by uhb1966
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The first one does not make sense, as it is only a 3.5mm EP. Its field of view fits easily in a 1.25" barrel.  Best value for money at the moment. In a fast scope like a Skywatcher Quattro (F/4, AFAIK), an Erfle will show severe astigmatism at the edges, so the second one is not ideal either. I would have a look at the bigger MaxVision EPs: http://www.explorescientific.de/Okulare/

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The TSWA'a look very like the WO SWANs and WO used to not recommend them on scopes slower then f/6 so your f/4 is too fast. Will say that the focal lengths given are different but the exterior looks very much the same on the 1.25" and the 2" EP's and so I am guessing they come from the same source.

The 2 links are to a 38mm EP and a 3.5mm EP, are they both correct ?

Just seems a big difference.

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AHA! Okay, after reading about astigmatism, and following michaels advice : how about

http://www.explorescientific.de/Okulare/Explore-Scientific-Maxvision-68-Okular-34mm.html

or

http://www.explorescientific.de/Okulare/Explore-Scientific-Maxvision-68-Okular-28mm.html

or

http://www.explorescientific.de/Okulare/Explore-Scientific-Maxvision-82-Okular-24mm.html

?

And - it looks like the shorter the focus of the eyepiece, the faster the scope might be? Interesting...

Edited by uhb1966
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The 24mm is likely to be the most effective with your F/4 scope. You might get away with the 28mm although the 7mm exit pupil is on the large side. The 34mm would not be too effective because it delivers an oversize exit pupil of 8.5mm.

Your scope will show some coma in the outer parts of the field of view which may bother you, or may not.

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The 82 deg EPs are said to be better corrected at F/4 than the 68 deg types. The latter are rated to be good down to F/5, although my 24mm did quite well in an F/4.1 scope. Of the ones listed, the 24mm would be best I feel, as it gives a wide, but still manageable 6mm exit pupil. I used my Nagler 22T4 and Olly's Nagler 26T5 to great effect in his 20" F/4.1 Dob, so I would expect the 24mm to work well in yours. The 28 and 34mm are 68 deg types, so might not work as well at F/4. Besides, they give exit pupils of 7 and 8.5mm respectively, which is a bit large (washed out background). Maybe an 18mm 82 deg type (max field of view in 1.25" barrel) would be a good option. The 4.5mm exit pupil means darker backgrounds

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  • 8 months later...

Thanks everbody!

From march to october, i did practically no viewing, but now, i'm using my gear more often and just placed the order for the 2" 24mm ES, as this seems to be the common sense of my fellow SGL'ers.

Thanks again for all your responses-

Regards, U.

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  • 6 months later...

So, after using the 82 deg 24mm at  http://www.explorescientific.de/Okulare/Explore-Scientific-Maxvision-82-Okular-24mm.html,

for some time now, i can confirm that this is a great eyepiece for an 8-inch F4 scope! It is, in fact, absolutely stunning! It feels a bit like really hanging in outer space, due to the wide field of view. It also looks (to me , a noob) like an incredible value for money.

Again, thanks a lot guys! This eyepiece, in fact, changed my habit from doing almost everything via photography to about 50-50 between astrophotography and visual observation.

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