An Extra-galactic Globular

6 September 2021, 22:15 – 00:00 (BST)

Seeing: Poor

Transparency: Average

Conditions: A still night, very warm and mild for the time of year. Some high, patchy cloud which cleared as the night drew on. Thin layer of condensation on the scope by the end of the session.

After allowing time for the scope to reach equilibrium (and my eyes to dark-adapt), I started with a look at the autumn highlight globular clusters M15 and M2 at 171x, although the iffy seeing prohibited me from resolving the fine detail I was hoping for.

After a quick look at Saturn, I then paid a return visit to NGC 7814, which was very faint tonight. Supernova 2021rhu, unsurprisingly, was no longer visible.

However, NGC 404 (Mirach’s Ghost) was quite obvious at 171x, even with Mirach in the field. Mirach itself is worth looking at, as it has a distinctly reddish hue.

M32, satellite galaxy, Andromeda

171x. Small, round and very bright. Condensed core with a star-like nucleus. With prolonged examination there seemed to be just a hint of elongation along the axis pointing towards M31.

Mayall II (G1), globular cluster, Andromeda

171x. Finally tracked down the Andromeda Galaxy’s biggest and “brightest” globular cluster. I reached it via a careful and somewhat complicated star-hop from M32, but it was visible with averted vision as a tiny fuzzy spot flanked by one or two faint foreground stars. Most sources give the magnitude at somewhere around 13.7, but fortunately its light is very concentrated, which helps with its visibility.

G1 was a little more obvious at 240x (still using averted vision), but it was still very challenging. Now I know how to find it, I might try this again on a better night when M31 is nearer the zenith.

I finished off with a look at Jupiter at 240x and 342x (171x + 2x Barlow). All four Galilean moons were west of the planet. Indifferent seeing smeared out most of the fine detail, but one brown barge was visible near the western limb. The orange colour surrounding the NEB appeared to have spread farther into the EZ, and the northern polar region seemed to have a slightly blue-ish tone (compared to the southern region). I’ve noticed this before but I haven’t seen it on images, so I’m wondering if this is an illusion caused by atmospheric dispersion or contrast effects.

Nature (and other) notes:

The frogs were quite vocal tonight. Also, lots of air traffic flying east (out of the country). Oddly, I didn’t see any flying west.

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.

Galaxies and Ice Giants

4 October 2018, 21:45 – 00:00 BST

Conditions: The seeing was quite good but the sky was a little hazy, affecting the transparency.

NGC 7479, galaxy in Pegasus
Viewed at 133x (9mm Nagler): faint, extended streak of light with bright star at one end and a fainter one at the other. First impression - not unlike NGC 891. Sky transparency not good enough to see spiral arms, but suggestion of mottled structure along central axis.

NGC 404, Mirach’s Ghost, galaxy in Andromeda
Follow up observation at 240x (5mm Nagler). Showed up very well. High power made it easier to keep Mirach out of the field of view and to see more detail in the galaxy itself: condensed core and suggestion of nested structure rather than smooth gradation – arranged in two or three “shells” of brightness.

Neptune
Appeared as a blue “out of focus” star. The colour made it stand out from neighbouring stars. Hard to resolve, even at 240x. Two faint stars in vicinity.

Uranus
Obvious green-grey disc even at 133x. Clearly resolved at 240x – no detail or moons seen.

NGC 7331, spiral galaxy in Pegasus
Bright core, extended envelope, sharp cut-off on one side, indicative of dust lane. Very much like a smaller copy of M31. Could probably take 240x.

M74, spiral galaxy in Pisces
Faint, but still obvious despite its reputation as the toughest Messier. At 133x it showed a condensed core surrounded by a large faint disc. Hard to see any detail, but darker areas possibly indicating regions between spiral arms.

NGC 772, spiral galaxy in Aries
Small asymmetric patch of light, lacking same degree of condensation as M74. Seemingly irregular. My old notes tell me that I did see this with the Vixen 102, describing it as looking like a "ghost globular".

NGC 925, spiral galaxy in Triangulum
Extremely faint, amorphous patch of light. Could be easily overlooked if just sweeping through the area.

M33, spiral galaxy in Triangulum
Seemed positively bright compared to the previous three galaxies. One spiral arm clearly seen: clumpy patch of light curling from core towards a bright field star. The question remains (as with NGC 891) as to how much of this I would be able to see if I wasn’t already familiar with the photographic representation.

A quick look at the M31 satellite galaxies:
M32, Andromeda: star-like core.
M110, Andromeda: faint field star nearby perhaps matching location of globular? Maybe that's wishful thinking, but the G1 globular should just about be within my the range of my scope. Will need a detailed finder chart or photo to verify.

A quick look at two open clusters in Perseus:
NGC 1528 & NGC 1513: misty patches at 50x, partially resolved.

NGC 1664, open cluster in Auriga
Very distinctive cluster; stars form an outline resembling a kite or a stingray.

NGC 1579, emission nebula in Perseus
Very faint patch of light, possibly doubled. Somehow managed to lose track of it when I put in the Ultrablock. Though I might have been hampered by condensation.


Eventually the session was curtailed by condensation on the secondary mirror (although the primary remained dry). Could mean that I’ll be limited to two-hour sessions between now and spring.

Nature Note:
3 frogs in the pond: 1 big, 2 small.

A Nebula in another Galaxy

14 September 2018, 23:00 – 01:00 BST

Started by looking for Neptune but I couldn’t be sure I’d found it, even at higher magnification. Lack of bright stars nearby makes it difficult to star-hop with the EZ Finder.

M31, Andromeda Galaxy
Satellite galaxies M32 and M110 showed up well at 133x, but M31 still frustratingly bland apart from the dark lanes.

M33, galaxy in Triangulum
Viewed at 133x for a change and very quickly spotted the star-forming region NGC 604 as a small but obviously non-stellar patch of nebulosity close to a foreground star. I could still see it when I switched to 50x, though it’s easy to overlook at lower magnification. (Certainly much easier to pick out than the NGC 206 star-cloud in Andromeda.) With hindsight I probably could have seen it with the Vixen 102 if I’d known where to look, but now I can use it as a reference point to trace out the spiral arms. It's kind of mind-boggling to realise that I’m looking at a nebula in another galaxy. A reminder that higher magnifications are worth trying even on low surface brightness objects like M33.

NGC 891, edge-on galaxy in Andromeda
Still very challenging, but an improvement on my last attempt. Appeared as a very faint spindle of light, a little brighter on one side. Central dark dust lane seen fleetingly with averted vision as a narrow bar of empty space. I'm not familiar with using averted vision to see a dark or “absent” object (especially when I'm already using averted vision just to see the galaxy), so the effect was slightly disconcerting. It was as if the dark lane was right in front of my eyes the whole time, but for whatever reason I had to “allow” my brain to see it. Would I have noticed that level of detail if I hadn’t already seen so many photos of NGC 891? That's a tough question to answer, but I'd like to observe this galaxy again on a really dark, transparent night to put it beyond doubt.

Almach, double star in Andromeda
Very pretty at 133x – straw coloured primary, aquamarine secondary. Shows what an improvement steady atmosphere and properly-cooled mirror make not just to resolution, but colour perception too.

NGC 1023, galaxy in Perseus
Extended ellipse of light with a bright core, not unlike 7331 in Andromeda.

NGC 1245, open cluster in Perseus
Faint but rich sprinkling of stars, shaped like a large swift or a bow “aimed” at a brighter nearby star.

Double Cluster, Perseus
Hard to put into words how stunning this is through a telescope. Red giant stars showed up better with improved seeing and higher altitude. Exquisite resolution of bright and faint stars in the densest regions of the clusters.

Pleiades (M45), Taurus
Too large for field even at 50x. Definite mistiness around some stars – reflection nebula at last? Need to cross-check against photo, and inspect at higher magnification.

Andromeda – Cassiopeia – Perseus

5-6 August 2018, 23:00 – 02:00 BST

As expected, I wasted a lot of time getting the SP/TV-60 combo polar-aligned and focused (but in my defence I hadn’t done it since May). I took a couple of test shots of the Veil Nebula but, realistically, exposures longer than about 90 seconds will need autoguiding – especially the further I get away from the pole. But on the plus side, I appear to have fixed the issue with the declination worm gear.

Anyway, I switched to a brighter object and shot 60 x 1 min exposures of M27, the Dumbbell Nebula. While that was in progress I pointed the XT10 at the following targets:

Saturn showed fleeting moments of good seeing, but again, not enough to justify shooting video clips. It’s noticeably lower in the sky now, so it’s unlikely it’ll look as good as it did on 25 June (at least for this year).

The Witch’s Broom segment of the Veil Nebula was faintly visible at 50x, brushing against 52 Cygni – the first time I’ve seen any part of the Veil without having to use the Ultrablock filter. Though I’m not sure I would have noticed it if I hadn’t already known it was there.

Double Cluster in Perseus
Spectacular as always. No significant increase in the number of stars I could see, but they were all that much brighter. The usual red giant stars were prominent – particularly the one halfway between the two clusters.

M31, Andromeda Galaxy
With the higher altitude I could get a sense of the galaxy extending beyond the dark dust lanes. The star cloud NGC 206 seemed to be visible with averted vision, but I’m still getting my bearings with Andromeda. The 24 mm Panoptic is better for getting more of M31 in the frame, but higher magnification might improve the contrast around its constituent parts.

M33, Triangulum Galaxy
Some tantalising structure starting to emerge, but needs to be higher in the sky. Again, higher magnification and a detailed finder chart might help with this one.

NGC 752, open cluster in Andromeda
Bright stars, but a large and very loose cluster. Better suited to the TV-60 or binoculars.

NGC 891, edge-on galaxy in Andromeda
Took a long time to find it, and even then it was extremely faint. I think I was expecting something smaller and brighter, but perhaps (although I couldn't see it) the light from the rising moon was already starting to interfere.

M76, Little Dumbbell Nebula in Perseus
Bright both with and without the filter. Double-lobed structure with one lobe clearly brighter than the other. Light greenish colour.

Then followed a quick tour of Cassiopeia to reacquaint myself with its many star clusters; not much to add on the notes from the old SP-102 log but now all the clusters are resolved to varying degrees (sometimes to their detriment, as the larger, looser clusters are hard to distinguish from the background Milky Way):
NGC 457, Owl Cluster: like meeting an old friend; one of the most distinctive clusters not in the Messier Catalogue
M103: very pretty little cluster
NGC 663, 659 and 654: 3+ clusters in the same patch of sky; potential astrophoto target
NGC 7789: very rich cluster
M52: also rich, but smaller than 7789; Bubble Nebula suspected, but not confirmed
Stock 2: large, sprawling cluster, more like a denser section of the Milky Way

NGC 281, Pacman Nebula (surrounding IC 1590 cluster) in Cassiopeia
Faintly visible without the Ultrablock filter, the addition of which increases its size as well revealing a trace of mottled detail. Very obvious dark bay eating into nebula. Sparse but tight grouping of stars at centre – more like a multiple star system than a cluster. Its size (about the same area as the moon) makes this another potential photo target for the TV-60.

Other Notes
Perseid meteors becoming more frequent.
NELM: Approximately 6 naked-eye stars counted in the square of Pegasus, indicating a limiting magnitude between 5.25 and 5.5 tonight.

Nature Note
One bat, a curlew (and some other bird – likely a wader) calling in the distance, and two frogs in the pond (one big, one little).