3 September 2019, 21:45 – 23:45 BST
So I’m a little late to the Ethos party, but this particular eyepiece has been in my sights for a while, for the following reasons:
As much as I love the 24 mm Panoptic (I originally got it for my 102 mm Vixen refractor), the large exit pupil and lower contrast at 50x means that a lot of the fainter stars and low-surface brightness DSOs that would otherwise be visible in the XT10 are washed out in my somewhat light-polluted sky. The Nagler 9 mm resolves those problems, but its smaller true field of view (0.59 degrees) makes it harder to tell where I am, and the larger star clusters and DSOs lose some of their visual impact. In the XT10 the Ethos produces nearly the same TFOV as the Panoptic, but at almost double the magnification. (For more on why this matters, see Al Nagler's essay on the Majesty Factor.) I'll still use the Panoptic (for large objects like the Veil and the North America Nebula that respond well to filters, it comes into its own), but the Ethos fills a gap in my eyepiece collection.
And, if that isn't justification enough, having started this hobby squinting through "drinking straw" 0.965" eyepieces, I can really appreciate the value and sheer comfort of looking through a high quality wide-field eyepiece. A recent S&T article on "hobby-killers" warned against small telescopes and their small eyepieces, but I think a case could made for starting small. It forces you to hone your observing skills and certainly gives you a greater appreciation for the good stuff when you can afford it.
Usually the purchase of new astronomical equipment is immediately followed by a month of bad weather, but fortunately I got a chance to try out the Ethos only the second night after it arrived. The forecast wasn’t promising and there were indeed a lot of clouds passing overhead, but there were just about enough gaps to make it worthwhile.
Initial Findings
The eyepiece needs the 2-inch extender to reach focus with the XT10’s Crayford focuser. The Ethos is heavy, but it’s nothing that a tightening of the altitude tension bearing can’t fix (and it’s not as heavy as the Canon 80D / 2.5x Powermate combination).
Because I was chasing the gaps in the clouds, the session was more of a whistle-stop tour than I would have liked, but I was able to make the following observations.
Field of View
I doubt I'm the first one to make this comparison, but going from an 82-degree Nagler to the 100-degree Ethos is like moving from CinemaScope to IMAX. I had to practically bury my eyeball in the eye-lens and move my head around just to see the field-stop. To call it immersive is an understatement. It’s the perfect eyepiece for sweeping along rich star fields, and I found it a very comfortable viewing experience. For telescopes which don't track - like Dobsonians - it's a godsend; you can keep the target in view for longer without having to constantly keep nudging the scope. If you’re into astro-sketching you might prefer a tighter field of view to work with, and putting bright objects outside the field-stop (to reveal faint neighbouring objects) is a little trickier than usual, but otherwise I can’t think of any downsides.
Sharpness
Star-testing confirmed my daylight observations with the TV-60: this eyepiece is extremely sharp on-axis – perhaps the sharpest I’ve ever looked through (and my other Tele Vues aren’t exactly lacking in this regard). I’ve read about this finding previously but I put it partly down to reviewer hyperbole until I saw it for myself. The stars boiled down to perfect little pin-pricks of light, which also made it easier to snap them into focus. As expected (the XT10 is a fast f/4.7 scope), stars towards the edge of the field exhibited the arrowhead shape characteristic of coma, but it wasn’t obtrusive, and the field of view is so huge I didn’t really notice the effect unless I specifically looked for it.
Colour
I couldn’t honestly tell if the eyepiece gave “warm” or “cold” views (I think that test will have to wait for when the moon is high in the sky), but I did notice that star colours stood out particularly well. The red giant stars in and around the Double Cluster were easy to pick out and the pale yellow / pale blue combination of Almach (Gamma Andromedae) made a lovely contrast.
The intensity of planetary nebula NGC 7662 (The Blue Snowball) seems to vary slightly each time I look at it (though that probably has as much to do with my eye as it does with the equipment and the sky conditions), but on this occasion it seemed to have a turquoise tinge. (I struggle to tell the difference between green and blue in low light, so take these types of colour observations with a pinch of salt.)
I won’t go through everything I looked at (for the most part I stuck to “showpiece” objects that I was already familiar with), but here are a few notes on specific DSOs worthy of mention:
The Double Cluster looks great in just about any scope, but this is by far the best view I’ve ever had of it. The field of view is just wide enough to encompass both clusters and some of the surrounding star field. Pinholes in black velvet? Diamond (and ruby) dust on silk? Words can’t really do justice to this vista any more than photos can.
M2 and M15: I think the 9 mm Nagler is still my eyepiece of choice for globular clusters, but the Ethos really makes it feel like you’re looking at them from a vantage point somewhere in deep space. M2 was a little washed out by light pollution, but still partially resolved, whereas M15 showed a sprinkling of stars all the way to the core.
With the addition of the Astronomik OIII filter, the Veil Nebula was an impressive sight. The view through the 24 mm Panoptic is perhaps aesthetically better (but only marginally) simply because the nebula covers such a large area of sky, but the fainter parts of the eastern and western arcs were easier to trace out in the Ethos, and I could see substantially more of Pickering’s/Fleming's Triangle, including part of the wispy section that trails off to the south. I think for detailed study of the Veil, the Ethos wins out.
With the OIII filter still in place I had a quick look at the Crescent Nebula in Cygnus before the clouds got to it. It resembled a letter C hanging in space, not unlike the white C on the underwing of a Comma Butterfly.
The Andromeda Galaxy was big and bright, with M32 occupying the same field of view. It only took a slight push of the telescope tube to locate M110, which also showed up very well. I'm looking forward to exploring the Virgo Cluster with this eyepiece.
The star clusters of Cassiopeia were rich and numerous in the Ethos; this eyepiece really gives you the best of both worlds in that you can view them in the context of the surrounding Milky Way and resolve them at the same time. I could easily spend a whole session just sweeping back and forth across this constellation, but perhaps the stand-out cluster was NGC 7789. In the 24 mm Panoptic many of its stars are just a little too faint to be resolved properly with direct vision, whereas in the 9 mm Nagler it fills the field of view to the point where it looks more like a rich portion of the Milky Way. The Ethos showed it in its full glory; lots more stars were resolved and I could see dark lanes appearing to curve through the cluster (not unlike the straight ones which cut through the Wild Duck Cluster). For the first time I could appreciate how it got its nickname “The Rose Cluster”. The individual groups of stars really did look like unfurling petals.
Disclaimer
I was not offered any incentive (financial or otherwise) by Tele Vue to write this post. Other wide-field eyepieces of similar focal length are available, comparison reviews of which can be found on sites such as Cloudy Nights, Stargazers' Lounge and Scope Reviews.
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