choosing an EP family

[glend (Glen)]

I believe you need something like a 2" 30mm, my 30mm is the EP I always start out with on my pushto dob and when you barlow it you have a 15mm equivalent. I believe Televue's eyepiece paper, that; s sent out with new EPs, suggests field stop selection. If you go by Al Nagler's advice there he suggests a field stop of 40mm which equates on their spec list to a 31 Nagler 5 or a 35 Panoptic. The 31 Nagler 5 will give you a wider field of view than the Panoptic.

[JJDOBBER79 (Jas)]

I have just seen ES 100 degree 20mm at astropetes for $399
Also, I have just read a post on deep sky forum from someone claiming that they are almost as good as the ethos. There is certainly a massive price difference. Does anyone have the ES and use it with a 12" dob? I figure I should maybe start with this and barlow it up to 10mm. Maybe ok for galaxies at 20mm given the extreme FOV????

[Allan]

Picking which focal lengths to get is not too hard. At the low power end it's good to have something that approaches the largest exit pupil you can use in your scope. That will be an eyepiece that is good for cruising the sky and checking out larger objects. I can see M31, M32 and M110 in the same FOV in my 31 Nagler. Although if your site is a bit light polluted you might not use the 31 so much, but it is a magic eyepiece from a dark location. I probably use my 21 Ethos ten times more than my 31 Nagler in my yard, which is a bit light affected.

The high power end is limited by the atmosphere. I have found over time the 6mm is about the shortest focal length I like to use in my 12". You could always get a 12 and Barlow that.

So between low and high power you just fill in the gaps with logical steps. Just be aware that as the focal lengths get shorter, you need to have smaller gaps between focal lengths as the magnification rises rapidly.

The 24 Pan is a nice eyepiece, but seeing as you ask, it won't see much use on galaxies, except for the big show piece ones. Most galaxies are quite small. My most use eyepiece is the 10 Delos for galaxies as it hits a sweet spot for magnification and FOV.

The only thing the 17 Nagler does better than the Delos is a larger FOV. The Delos has the flattest FOV, best transmission, best colour rendition, better eye relief, is lighter. Having said that, I really like the 17 Nagler as it's a great eyepiece, but you are comparing it to the best widefield eyepiece you can buy. So IMO there is not much reason to buy the 17 Nagler when you can spend less money buying the 17.3 Delos and end up with a better eyepiece.

So a setup with a 31 Nagler then 17, 12 and 8 Delos is one option that ticks a lot of boxes. But you can kick this can around all day and keep coming up with different ideas. That's half the fun.

[Allan]

People who get the ES seem very happy with them. Almost as good as Ethos but a lot cheaper. The only negative thing I have read is the eye relief is quite tight in comparison to Ethos. But the FOV in the 20 is so wide it could work as your low power eyepiece.

I would have second thoughts about barlowing it though. These are big and heavy eyepieces.

[AstralTraveller (David)]

Keep an eye on the classifieds. You just missed a 20mm ES for $270. I bought all my premium wide-field eps though the classifieds (and deep bows to ep recyclers).

FWIW I suggest fewer good eps and I'm not too fussed on barlows. Maybe that's just a hangovers from too many cheap barlows. About you low power ep, if your pupil can open to, say, 6mm then the lowest useable mag = 300/6 = 50x. Assuming your 12" is f/5 then your widest ep would be a 30mm (or31). The 31 Nagler was beyond my budget so I wound up with a WO 28mm UWAN. I haven't done a side by side comparison with a 26 or 31 Nagler but it looks dang fine to me. It certainly doesn't lose much to my excellent 20mm Type 2. I spaced wide-field my eps in the ratio 3:2, so 28-20-13-9. That covers all bases. Then I have UO orthos for the planets.

[JJDOBBER79 (Jas)]

I really like the idea of the 100 degree ES. I think I will get one of those and for higher power I reckon a delos (mainly because of price) either 14 or 12 and a 2x TV barlow. (and maybe a 31 nagler down the track when my wallet recovers)
Allan, I forgot about the the extreme weight and size of the ES, wont be barlowing this. Given the extra wide FOV, does it mean that the ES would be more useful for a broader range of targets? David, I definately will keep an eye on the classifieds. I think everybody on this forum treat these kind of high end EP's like they are children so will be happy to buy off here.

[MattT]

Those were my ES 100º….maybe a bit too cheap…who cares... I don't. They were really terrific in my f8 6" and f9 100ED refractors, but not so good in my f12 6" refractor, don't know why. I have had them in my f4.8 Newt and didn't like them one bit…talk about coma city. So if you get the 100's you are going to have to get a coma corrector too, at least I had too, and that is a lot of tubes hanging out the focuser…a lot. Give me 68º eyepieces any day. Not so bad in the Newt without the CC perfect with the CC (coma corrector) and perfect in any of my refractors 70mm f7, 90mm f11, 100mm f9, 150mm f12, and not forgetting 50mm f12 What a little cutie it is.
If you haven't done so check out the Cloudy Nights eyepiece section…it's a mine of information…..
Shees where is Suzy when you need her, now her threads are really worth reading
Matt

[JJDOBBER79 (Jas)]

so, you wouldnt recommend the 100's in a 12" dob?
Is anyone out there using this combo because the problem with them being so big means that I cant barlow and I cant coma correct.

[jamespierce (James)]

My 2 cents.

If possible buy from the same series (you get constant field stop, colour and handling etc)... So I've gone with all Naglers, but you could go Ethos or ES etc...

Forget the barlows ... I have one, never use it ... I don't know a serious observer who uses one with any regularity... More glass, more flare, more weight and alignment issues.

As for what focal lengths to get...

Whatever gives you a 5-6mm exit pupil for your scope. Something around the 1.8-2mm range (this is basically the sweet spot). Something around the 1mm mark, and down the track, perhaps something pushing 0.5mm for very good nights on the planets...

In my 16" F4 I have 31,20,13,9,7 Nag ... The 20 and 13 see the most action, then then 9, followed by the 31 and 7. I also have a 5mm Tak LE for very very good nights - very sharp EP.

This calculator is very helpful - http://www.davidpaulgreen.com/tec.html

[Allan]

My coma corrector is an integrated part of my focuser and I just forget it's there, and I never think about coma. Having a big 100 degree eyepiece in a Paracorr is a big setup to have in your focuser, but I see plenty of people use that setup. If you don't want to do it that way you will have to get used to the coma.

I found my Ethos without the Paracorr is still ok, it's there but not too objectionable, they may be better corrected for coma than the ES. All these little improvements explain why Ethos are more expensive.

You won't notice much coma at all in the Delos because of the narrower FOV. You can get away without a Paracorr using them.

[MattT]

Allan are you binoing with the SIPS? You don't bottom out and hit the lens?
The ES 20mm weighed 990grams from memory and you can put a Coma corrector in the focuser they aren't that big…I just prefer the 68º eyepieces. 82º I tried but never really liked but the 68's hit the spot for me…and lots of others too. Can you try a 20 ES 100º and send it back and get something else if you don't like it? Worth asking.
The 20mm ES 68º I use in the Newt is Coma free to about 80% out. I'm a refractor user mostly and the ES 68's are all pin point sharp to 98% out. The last 2% isn't worth the hundreds of dollars extra to get Panoptics.
If you buy used most likely you can sell for much the same price if you decide you don't like it.

[Allan]

Hi Matt. No I am not bino viewing with the SIPS in. I replaced the Allen head screws in the Feathertouch with thumbscrews. So when I change from mono to bino I loosen the screws and remove the lens section, then refit the focuser. It takes no more than 20 seconds to change modes.

[JJDOBBER79 (Jas)]

Ok, I've made a final decision.

100 degree ES 20mm, not barlowed
14mm Delos
Xw10
2x TV Barlow
This will give me 20, 14, 10, 7, 5

The 14 Delos will come first as I feel it will be most useful. If I don't like any of these I will resell and get something else in the same focal length. Thanks for everyone's help with this. Big decision. I'm sure the collection will not stop there.

[Camelopardalis (Dunk)]

I think in a 12" Dob you'll use the 20 a lot, the others not so much

I can understand your compulsion to want to experiment, we've all been there but don't rush to buy the Barlow... you'll prolly find out (like the rest of us) that it's a lot of fumbling in the dark with expensive optics

[JJDOBBER79 (Jas)]

Yeah maybe. The Barlow will probably be last. It's just to push the power a bit on good nights. I'm hoping that quality like Delos and xw will handle this in good seeing.