Explore Scientific 20mm 100 degree eyepiece

[Lorne]

I got the chance to try my 20mm last night. The sky was clear but there seemed to be a bit of moisture in the air. Unlike John's original review I had nothing in a similar focal length to compare it with. A few examples of my targets...

M31, good view with SLIGHT hints of dust lane - probably due to the seeing, both companion galaxies visible JUST with good bit of eye movement, all 3 were easily visible in my SW 28mm Nirvana

M33, nicely framed showing well with a darker background than I'm used to seeing it. 

M81, 82, both easily fitting into the FOV with room to spare, no sign of NGC 3077 which was visible in the same FOV in my SW 28mm Nirvana

M42, (low in the sky) again, nicely framed looking good. The trapezium easily viewed.

Auriga clusters, Pleiedes, Hyades, Melotte 20, Double Cluster, These, in my opinion, bring the eyepiece to life. There seems almost a 3D feeling when looking at these type of objects - the spacewalk feeling.

I found the 20mm ES eyepiece easy and comfortable to use, although the eyecup - mentioned by John - is pretty flexible and tends to fold over.

Also, although this is not an issue for me, when swapping back and forth with my 14mm ES the range is far from being parfocal, almost the full travel of my focuser between the 2 EP's.

I know some people look for a range being parfocal.

I will miss my 28mm Nirvana but for the trade in more magnification (53X to 75X)  for slightly less FOV I think it was worth the change. As with John, I wouldn't hesitate to recommend this eyepiece to anyone.  

L.

[gooseholla]

Yeah I did notice that the 20mm for some reason focuses right at the beginning of the travel and all my other eyepieces focus well out from it. Like I said, I had to chop my pole down just to get it to focus.

Thanks for posting your observations.

John

[Lorne]

Chopping poles! that takes astronomy to the extreme!! anyway, thanks again for the original heads up to the Bresser sale link.

[gooseholla]

Hi all, 

Just an update on this excellent eyepiece. After using it for a while I decided to get rid of my Nagler T5 20mm. Viewing Jupiter and the Moon tonight was phenomenal and I have no regrets about getting rid of it, and didn't feel like the view was inferior in anyway whatsoever.

John

[John]

I did the same when I had the ES 20 / 100 John. It's an excellent eyepiece.

[Commanderfish]

Hi guys,

I have the ES20mm 100 degree and the Ethos 21mm.  I use longer focal length scopes (F6 ED Apo, F7.5 ED Apo and F10 SCT. 

I experience no coma in any of these scopes  with either eyepiece.  The views are lovely and sharp in both.  Contrast is very similar in both.  I'll test them some more to try and see if there is any difference at all. The Ethos is a slightly longer focal length so in theory it should have ever so slightly less contrast than the ES, but it doesn't, they are very similar.  It is therefore possible that the Ethos is technically a tiny bit better - but as I said, you're not actually going to see a difference. 

I did notice that on Jupiter in particular, the ES has a warmer colour tone, whereas the Ethos has a neutral, whiter tone.  However, this is only noticeable for the first second or two after changing the eyepiece, then the eye seems to stop registering the difference.  Not an issue at all for viewing, though people might feel a slight preference once way or the other.

The other difference I've noticed is that the ES does not seem to require as much movement of the eyeball to use the whole field.  The movement required to see the field up to the field stop in the Ethos does not bother me, but I do think it needs a bit more movement of the eye.  

I'll definitely be keeping both as they are such a useful length and field size in each of my scopes, and I tend to use 2 or 3 scopes simultaneously on my Ercole Grio mount.

Square Slice, I would recommend trying the ES 30mm 82 degree to replace your 28mm Nirvana.  It gives an appreciably bigger field than the Ethos 21/ES20 100 and produces lovely views.  It is the widest field EP in my case so gets a lot of use next to the Ethos 21 and the ES20 100.

[John]

Interesting report above. I moved onto the 21mm Ethos from the 20mm ES 100. Very little difference in performance in my scopes (F/5.3 - F/7.5). I found the useable eye relief of the 21mm Ethos a little more generous than the ES 20 / 100 was in that I needed the roll the rubber eyecup down on the ES to access the full FoV but I don't need to do that on the Ethos 21.

I use the 31mm Nagler as my "max field" eyepiece. I thought that the Ethos 21 / ES 20 100 might supplant it but I still find that I use the big Nagler a fair amount.

[gooseholla]

Interesting - I can use the ES 20mm with the eyecup in place and see to the edges. 

John 

[John]

38 minutes ago, gooseholla said:

Interesting - I can use the ES 20mm with the eyecup in place and see to the edges. 

John 

Different face ergonomics probably

 

[gooseholla]

Now the question is - do I go for the 9mm version or stick to 82 degrees and get the 8.8 mm? Hmmm.

John 

[John]

7 hours ago, gooseholla said:

Now the question is - do I go for the 9mm version or stick to 82 degrees and get the 8.8 mm? Hmmm.

John 

Having used 100 degree eyepieces from a number of different brands my feeling is that the manufacturers put their all into these ranges and see them as flagship products. The 100's have seemed to me a little better all round than the 82's from the same manufactuer. The penalties of the 100's are weight, bulk and cost though. Choices, choices

[gooseholla]

Money no object ;-) Weight doesn't really bother me. I think i'll get a 9mm and maybe 14mm. Not sure the 5.5mm is for me. I already have the 6 and a bit 82 degree version. 

John 

[niallk]

Hi - if you move the moon to the edge of the fov in your ES20, does it take on a strong yellow colouring - or does it remain sharp & neutral to the edge?  I'd be interested in comments on the 21E's performance too.  I've seen this effect at f/4.5

Thanks,

-Niall

[gooseholla]

It indeed takes on a yellow colouring. 

[Commanderfish]

I did a bit of experimenting using my ED127 F7.5 on the Double Cluster last night.  Near full moon at the other end of the sky, but the ED was cutting through producing some nice sharp views.  I switched between the Ethos 21 and ES20 100 several times noting any differences.   I found that there was more variation in the seeing conditions (which were fairly steady) than there were differences between the two EPs, except that I did notice that it was easier to see the red stars in the cluster using the Ethos 21.  I haven't actually noticed the red stars before.  Once I noticed them in the Ethos, I was then able to discern them as red in the ES20 100.  They were somewhat more red in the Ethos though.

The views in both EPs were sharp to the edge, high contrast, crisp and just damn fine. Note this is in an F7.5 scope The Ethos is a small bit better, but if you went out and bought two ES100s instead of an Ethos 21 you wouldn't regret it.  Can't go wrong with either.

A quick note on the Nagler T5 31mm and ES 30mm 82, which are very similar to each other in field size and performance:  you can try to replace these with an Ethos 21 or ES20 100, but ultimately the 31mm or 30mm are wider by around 23% diameter and you will notice the difference in field.  Still worth doing if that's what you need to do to get access to a 100 degree 20/21mm eyepiece.  Though at some point later you'll probably buy an ES 30mm 82 to get the widest field.  I did!

[niallk]

On 19/04/2016 at 00:28, gooseholla said:

It indeed takes on a yellow colouring. 

Hi - anyone know if the TV 21E behaves similarly? - Cheers!

[estwing]

Next time I have my scope out I will check on the 21e

[Daniel-K]

I never noticed with mine TBH. Kerry lewis now has mine maybe he can say.

 

[jetstream]

Almost all my eyepieces including the Ethos, ES 82's show a blue "ring of fire" at the field stop on the moon.

[John]

4 hours ago, jetstream said:

Almost all my eyepieces including the Ethos, ES 82's show a blue "ring of fire" at the field stop on the moon.

I agree - most of the 82 degree ones I've owned / used actually show a little more of this effect than the 100's, oddly enough.