Autumn Clusters

21 September 2019, 21:00 – 22:30 BST

Conditions: much the same as Thursday – very mild for time of year, bands of clouds moving slowly from the south.

Started off with a quick eyepiece comparison (viewing the Double Cluster): now I’ve looked through the Ethos a number of times, I can really see the flaws in the Orion Deepview 28mm. It has approximately the same size eye-lens, but that’s where the similarities end. The Deepview’s coatings are inferior (that’s obvious in daylight) and the sharpness falls off very quickly from the centre. I’ve also noticed before that when looking at a bright object like the moon in the Deepview, the shadow of the secondary mirror is visible. To be fair, the Deepview is a perfectly acceptable starter eyepiece (and easier to look through than ones I’ve used in the past), but I wonder if it’s really the best choice to bundle with an f/4.7 scope (especially one marketed in the "Plus" range). I doubt I’ll be using it again other than for demonstrating to others the difference between a budget and a premium eyepiece.

All subsequent observations with the Ethos 13mm.

NGC 6940, open cluster, Vulpecula
Rich, elongated cluster. On this occasion (and in this eyepiece) it looked a little like a swan in flight (which would be more apt if it were in Cygnus).

NGC 7160, open cluster, Cepheus
Attractive little cluster with five bright stars arranged in two groupings. One to revisit at 240x on a better night.

While sweeping the area around this cluster I stumbled upon Xi Cephei (Kurhah) – a really neat pairing of two bright stars. The colours were subtle, but the primary appeared to be white or very pale yellow, with a pale blue secondary roughly 10 arcseconds to the west.

NGC 7235, open cluster, Cepheus
Misty little spray of stars, 2 or 3 moderately bright members.

M34, open cluster, Perseus
Array of bright stars surrounded by a loose hexagon of stars, like a large spider sitting in a web. 2 close stars of equal brightness form the “eyes” of the spider. Looks good in the Ethos.

Nature note
Two large frogs (one of which left the pond to go roaming) and sixteen froglets.

Stars that pass in the night

19 September 2019, 21:15 – 22:00 BST

Conditions: good seeing, but a slight haze affecting transparency. Cloud cover increasing, curtailing session after 45 minutes.

With no time to waste changing eyepieces, all observations were carried out with the 13 mm Ethos.

After quick looks at the Double Cluster and the Saturn Nebula, I turned my attention to:

Veil Nebula, supernova remnant, Cygnus
Viewed unfiltered for a change. Both sides of the loop were visible, albeit very faintly. 52 Cygni was split nicely in the Ethos; the secondary showing up as a faint companion just six arcseconds from the primary.

M73, asterism, Aquarius
Four stars of similar brightness arranged in a tight “arrowhead” shape. Latest science suggests that this is just a chance alignment and the stars are not physically related.

Nature note
1 large frog in the pond, accompanied by 20+ froglets.

Finding Neptune

5 September 2019, 21:30 – 00:15 BST

Conditions: a near first-quarter moon low in the southeast ruled out observations in that part of the sky. A few small clouds passing overhead, air cooling noticeably, otherwise good for observing.

Albireo, double star, Cygnus
At 92x in the 13mm Ethos this presented as a golden primary and pale blue secondary suspended in a sea of stars. This might be the most beautiful view I’ve ever had of Albireo – certainly one worth savouring.

NGC 7027, planetary nebula, Cygnus
Revisiting one of last year’s targets. In the Ethos it resembled a defocused star. At 240x with the OIII filter it was very bright with a tantalising hint of structure. Quite small.

NGC 7039, open cluster, Cygnus
Looks good in the Ethos. A rich band of stars framed by a rhombus of brighter stars. Not far from the North America Nebula.

NGC 7048, planetary nebula, Cygnus
Just visible without the filter at 92x as a faint smudge of light with a star to the west. In the OIII it appeared as an elongated cone of light with a star at the apex. Unusual shape for a planetary nebula, but I think the star probably caused it to appear more distorted than it really is.

NGC 7000, North America Nebula, Cygnus
With the Ethos and the OIII filter, the “gulf coast” region of the nebula was clearly visible as a milky glow, resembling a large question-mark melting into the starry background. I didn’t think I’d be able to see it as well as this in the XT10.

M2, globular cluster, Aquarius
At 240x, the asymmetry noted before appears to be caused by two wings of stars sweeping back towards the west. The foreground star on the eastern side of the cluster seems to sit in its own pool of darkness, adding to the asymmetry. The cluster resolved really well with averted vision.

M15, globular cluster, Pegasus
Also observed at 240x. Member stars brighter than those of M2. Long loose “tail” of stars to north. Bright, dense core. The (rare) opportunity to view these globulars multiple times over the course of a fortnight really makes a difference – the more you look at them, the more you see.

Neptune 
Helpfully very close (maybe a little too close) to 4th magnitude Phi Aquarii, so (unlike last year) very easy to find. Viewed at 240x (5mm Nagler) and 333x (9mm Nagler + 2.5x Powermate). I need to try this again when the seeing is better, but Neptune was a tiny blue-grey disk (like a defocused star), contrasting nicely with the orangey-red Phi Aquarii. No sign of Triton.

M30, globular cluster, Capricornus
Small condensed blur, very low in the sky (-23 degrees declination). Bright leading star to west. Amazingly, with averted vision I could begin to resolve the cluster despite its low altitude: the most prominent features were a straight line of stars to the north and another fainter one (not radial to the core) to the northwest, giving the cluster a very distinctive lopsided, spiky appearance.

Just for fun, I also viewed M57 and M27 at 333x. Despite being on the light-polluted side of the meridian the Ring Nebula looked rather impressive at this high magnification (like a black-and-white photo); the Dumbbell not so much (it's large enough already that it doesn't really benefit from the extra power). But it's good to know I can use this magnification on some deepsky objects.

First Impressions of the Tele Vue 13 mm Ethos

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.