ES 18mm vs 19mm Luminos

[Nightspore]

 

I love my 19mm Celestron Luminos. Yes, admittedly, the entire series has various peculiarities that irritate many people. These include: edge astigmatism, edge of field brightening, ghosting, glaring inter alia.  Notwithstanding the twist-up eyeguard and its heavy shroud mechanism. Even with these shortcomings I still enjoyed using the Luminos as a rich field eyepiece on my Evostar 72ED DS Pro. 

 

 

The 82° field of view together with a large accommodating eye lens and with a huge 30mm field stop gave a stunning 22.1x for a 3.2mm exit pupil. The 20mm eye relief made it ergonomically pleasant and physically undemanding to use. However, there was one huge drawback; it is bloody heavy! I make it 460g with my kitchen scales. The main complication with this weight was in using the ED72 on a Vixen Porta II mount. The Porta altitude clutch had to be set tight enough for there to be no drift, yet loose enough to be able to switch to a lighter 1.25” diagonal for higher magnifications. The ED72 can have in-focus problems with 2” diagonals and shorter focal length eyepieces. My first instinct was to eschew the 2” Baader dielectric for the 1.25” Amici and use my 19mm Panoptic instead. 

 

 

There was a viable alternative. The  2”, 18mm Explore Scientific has some similarities to the Luminos. Although the eye lens and eye relief are respectively smaller and shorter, the eye relief being 7mm less and the field stop is only 25.3mm. There are advantages however. I make it 370g, considerably lighter than the Luminos. The barrel plays nicer with the Baader twist-lock, the flip-up rubber eyeguard is reassuringly simpler and I believe the eyepiece features Lanthanum glass elements. On May the 29th I got first light with the ES 18mm. I’d waited several months for this eyepiece and actually ordered it the previous summer. I spent a good 90 minutes solely with the 18mm ES, much of it around and in a rising Summer Triangle. The closer eye relief didn’t bother me, although I wasn’t originally impressed with the field of view in daylight tests with my ED80. It seemed visually claustrophobic in an f/7.5 doublet. This eyepiece seems better suited to faster scopes in my opinion. In the ED72 the field seems large enough and with no astigmatism that I could detect. The image was bright and sharp. I easily found both globular clusters in Hercules at 23.3x and even got a hint of M57. The 18mm ES is definitely a keeper and the 19mm Luminos can be used with the ED80. 

 

Edited June 6, 2020 by Nightspore

[+Streetbob]

I like the ES 18mm too. I also like the 11mm. However I find the 82 Deg afov doesn’t work so well with my varifocal glasses and now prefer smaller afov.

[+RonC]

I have to take my glasses off to use an EP, never could get on wearing them when observing!

Perhaps that's why I like AP!!

 

Ron

[+Streetbob]

Unfortunately I need to wear mine to get good focus though I’d prefer not to.

[+bryand]

I have trouble with varifocals too, so I got a pair of cheap distance-only specs from Glasses Direct which I use for astro work.

[Nightspore]

4 hours ago, Streetbob said:

I like the ES 18mm too. I also like the 11mm. However I find the 82 Deg afov doesn’t work so well with my varifocal glasses and now prefer smaller afov.

I have difficulty seeing the entire field with a lot of smaller focal length 82° eyepieces, particularly the ES series. I think it's just the 'nature of the beast' so to speak. I don't wear glasses but ES tend to exaggerate the eye relief on many of their eyepieces in my experience. I'm pretty pleased with the 18mm in the ED72 though.

[Nightspore]

 

Eye and field lens comparison.

 

[+Streetbob]

5 hours ago, bryand said:

I have trouble with varifocals too, so I got a pair of cheap distance-only specs from Glasses Direct which I use for astro work.

Good plan. Maybe I’ll try a pair of cheap bifocals.