Exploring Delphinus

1 September 2019, 21:30 – 01:00 BST

A cold night, and too breezy for imaging. Instead, for a change, I put the TV60 to use as an observing scope while the XT10 cooled to ambient temperature.

Transparency: not as good as 30 August
Seeing: Good to begin with, but worsened as the night progressed.

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TV60 + 24mm Panoptic (15x)
It’s a treat to just ramble along the Milky Way at this magnification, but the most noteworthy observations came when I added the OIII filter:

Veil Nebula, supernova remnant, Cygnus
Both arcs were visible (albeit faintly) in the same field of view. (This wasn't a surprise to me as I'd already tried this some years ago using the Ultrablock filter, although my notes from that time state that the western segment 6960 was only just on the threshold of visibility.) I think from a really dark site, Pickering’s/Fleming's Triangle might even be possible with this combination. Something to bear in mind perhaps the next time I take the TV60 on holiday.

NGC 7000, North America Nebula, Cygnus
Large and prominent at this magnification, and the OIII filter confirmed it as clearly nebulous in nature and not just a star-rich section of the Milky Way. The brightest section was the part adjoining the “Gulf of Mexico.” (Again, this replicated an observation made some years previously using the Ultrablock filter.)

NGC 281, Pac-man Nebula, Cassiopeia
Showed up well as an amorphous little glow, albeit devoid of detail.

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Other observations for the night were carried out with the XT10, using (unless otherwise stated) the 9mm Nagler (133x).

NGC 6716, open cluster, Sagittarius
Tight, boxy little cluster, shaped a bit like a backwards “2”.

Cr 394, open cluster, Sagittarius
Sprawling cluster, larger than 6716.

NGC 6818, Little Gem Nebula, Sagittarius
Tough to find (in a bright part of the sky with no naked eye stars nearby), but when I did track it down, it presented as a bright little disc, becoming even brighter with the Ultrablock filter (the OIII was still on the TV60). Prolonged examination revealed a dark core – a typical summer planetary. I also looked for the nearby Barnard’s Galaxy, but (as expected) it was hopelessly lost in the light pollution.

M75, globular cluster, Sagittarius
Grainy little fuzzball, washed out by light pollution. No stars resolved. Seemed quite small compared to other globulars, but perhaps I was only seeing the core region.

NGC 6934, globular cluster, Delphinus
Another grainy, unresolved glow. Appeared to have a slight bluish tinge. Bright field star to west.

Gamma Delphinus, double star
Impressively bright and close double star with an equally close (but fainter) pair of stars to the north. Reminiscent of Epsilon Lyrae.

NGC 7006, globular cluster, Delphinus
Faint round glow, brighter towards centre, but lacking the grainy appearance of the previous two globulars viewed tonight. Looked more like a comet than a globular cluster.

M72, globular cluster, Aquarius
Weak round glow, very faint for a Messier globular.

NGC 6891, planetary nebula, Delphinus
Very small disc of light, almost stellar (which explains why I overlooked it on 25 August). Needed the Nagler 5mm (240x) plus the Ultrablock to confirm its nature. Seemed slightly elongated at high magnification.

Couldn’t find NGC 6886 (I’m guessing it’s even tinier than 6891), but NGC 6905 (the Blue Flash Nebula) showed up well at 240x. Smoke ring of asymmetric brightness sitting in a triangle of stars.

NGC 185, galaxy, Cassiopeia
An exercise in frustration (the sky conditions didn’t really justify the amount of time I spent on this and 147), but eventually I located NGC 185 (one of M31’s outlying satellite galaxies). Soft round glow – very faint and featureless. No sign at all of NGC 147. Not a night for faint galaxies.

NGC 7293, Helix Nebula, Aquarius
A little more washed out by light pollution / poor transparency compared to Friday, but still impressive. With the Ultrablock I could make out several field stars surrounding the helix.

The Helix Nebula and other Highlights

30 August 2019, 22:30 – 01:00 BST

Much better transparency tonight – ideal for photographing my primary target for the autumn: M33. And the previous sessions had given me enough confidence in the imaging and autoguiding rig to leave it alone while it captured two hours’ worth of data. (With no bright stars nearby, the hardest part was getting the galaxy centred in the camera’s field of view.)

After idly touring the Milky Way while my eyes fully adapted to the dark, it seemed only right that I open the session with a closer look at the object I was imaging:

M33, Triangulum Galaxy
Viewed at both 50x and 133x; challenging as always. The northern spiral arm was easier to see than the southern one. The nucleus was star-like, with a faint star close to it (in line with NGC 604). Some of the other HII regions were suspected with averted vision, but not to the point where I could say I was confident of detecting them. I used a finder chart to pinpoint the location of the globular cluster C39 but, not surprisingly, it was below the threshold of visibility.

NGC 7331, spiral galaxy, Pegasus
Viewed at 133x and 240x. At the higher magnification there was perhaps a hint of one of the companion galaxies, but it was extremely subtle. Likewise, there was a very vague suggestion of a misty glow in the region where Stephan’s Quintet is supposed to be, but not convincing enough for me to call it.

NGC 7009, Saturn Nebula, Aquarius
Bright ellipse at 133x. At 240x with the OIII filter it became very bright, albeit devoid of detail. I couldn’t see the ansae directly, but with averted vision I could tell there was something “Saturn-like” about its shape. The nickname is well-deserved; at first glance it does look a lot like a ghost image of the ringed planet.

M2, globular cluster, Aquarius
Best view yet of this globular. Large, slightly elongated, well resolved, particularly with averted vision. The brightest member is just to the east-northeast of the core (though this may be a foreground star).

M15, globular cluster, Pegasus
Viewing one globular straight after another really allows you to appreciate the differences. M15 is brighter than M2 and clearly more condensed. Easier to resolve too (more stars visible in direct vision).

NGC 7293, Helix Nebula, Aquarius
With a declination of -21 degrees and a reputation for having a low surface brightness, I wasn’t sure if I was going to be able to see this planetary nebula, but a sweep of the area at 133x with the OIII filter quickly brought it into view. It showed up surprisingly well, looking not unlike its familiar photographic representation (albeit minus the colour). Even though I’d read about it before, I was still unprepared for just how big it appeared in the field of view. Overall it resembled a pair of large, ghostly overlapping smoke rings, with a darker cavity on the northwest edge and a hollowed-out interior. At 50x (still with the OIII filter) it was brighter still. The only other planetary nebula I can think of that vaguely resembles it is the Owl Nebula in Ursa Major, but the Helix is superior in every way (not just size). Easily the highlight of the evening. Afterwards, I removed the OIII filter to test if I could see it unaided, but it had left the field of view by the time I put the Panoptic back in and I couldn’t find it again. I’m pretty certain I was sweeping in the right area, so file that as another success for the OIII filter.

Nature note:
At least 10 frogs in the pond, including several of this year’s froglets and the large pale “telescope-hopper” from Monday night.

A Bow-tie in Cepheus

27 August 2019, 22:00 – 23:00 BST

The third clear night in a row, although the transparency was rather poor. The imaging target for the evening was the globular cluster M15.

Observations of M15, M71, M57 and NGC 7662 were affected by the conditions and so not really worthy of note-taking, although the latter (7662) did show a hint of a darker core at the higher magnification of 240x. However there were a couple of other highlights:

M103, open cluster, Cassiopeia
Triangular cluster with prominent red star at centre. While sweeping the scope towards Epsilon Cas I stumbled upon a tiny little cluster of stars, the four brightest stars of which formed an almost dead straight line. Not plotted in PSA, but confirmed in Uranometria as Trumpler 1.

NGC 40, The Bow-tie Nebula, Cepheus
Medium sized planetary nebula; faint envelope surrounding central star (not unlike the Crystal Ball Nebula in Taurus). The addition of the OIII filter gave a hint of a lobed structure, at the expense of the central star (which was swamped by the nebulosity). Worth revisiting under better sky conditions.

Other notes
Saw another late Perseid streaking through Lyra towards the end of the evening.

A Veil, a Snowball and a Bubble

26 August 2019, 22:00 – 23:30 BST

After the success of the previous night’s imaging session, it seemed only fair that I should photograph the other (eastern) half of the Veil Nebula, though without the benefit of a naked eye star (52 Cyg) to use as a target it took a little longer to get it centred.

Conditions: another warm night, slight haze affecting the transparency.

M71, globular cluster, Sagitta
Rich, filmy mass of stars in an already rich section of the Milky Way. More condensed than M11, but lacking the density of more typical globulars.

Albireo, Cygnus
Lovely double star; golden primary, pale blue secondary. (There isn’t really anything new I can say about Albireo, but I keep coming back to it.)

NGC 6819, open cluster, Cygnus
Cluster with a hat-shaped outline. Member stars not particularly bright. Central gap. Resides in a rich Milky Way field.

NGC 6866, open cluster, Cygnus
Another Cygnus cluster - like a larger, looser version of 6819.

Veil Nebula, supernova remnant, Cygnus
A comparison (at 50x) of the Ultrablock and the OIII filter. While both filters do an excellent job on this nebula, it was clear that the OIII provided a much darker background, thus making the nebula itself seem brighter. This also made it easier to see the overall shape of the two arcs and some of their internal structure, as well as the much fainter Pickering/Fleming’s Triangle. When I switched back to the Ultrablock, the triangle was just about visible, but I probably wouldn’t have noticed it if I hadn’t already seen it with the OIII.

Another thing I noticed with the OIII was that the area inside the loop seemed brighter than outside (particularly on the eastern side). This might be an illusion (long exposure images show that the visible nebulosity is confined to discrete sections), but the photos I took seem to hint at a greater star density inside the Veil. (Is the shockwave clearing away the interstellar medium, creating a window in that part of the Milky Way?)

NGC 7662, The Blue Snowball, Andromeda
Tough to find on this occasion for some reason. Otherwise as before, blue-green colour.

NGC 7331, spiral galaxy, Andromeda
Streak of light, no sign of the companion galaxies (the “fleas”), but not surprising given the less than optimal transparency.

NGC 281, emission nebula, Cassiopeia
I needed the OIII filter to see it (at 50x), but once I did the overall comma shape stood out well, with a suggestion of dark inlets cutting into the nebula.

NGC 7635, Bubble Nebula, Cassiopeia
With the OIII filter still in place, I pushed the telescope past M52, not really expecting to see anything, but the nebula stood out surprisingly well. Not so much a bubble as a little crescent-moon shaped patch of nebulosity. I swapped out the 24mm Panoptic for the 9mm Nagler (minus the filter), but the nebula was no longer visible.

I rounded off the evening with a quick look at two old favourites in Cassiopeia: M52 (a rich little cluster) and NGC 7789 (a rich large cluster with faint stars arranged in clumps).

Nature note
While I was taking a test shot of the Veil I heard a “clonk” from the XT10. Upon investigating with a red-light torch, I discovered that a large pale frog had hopped onto the base underneath the main mirror. It took some persuading to vacate its temporary home, but I eventually sent it safely on its way. Still, at least it blundered into that scope rather than the one taking long exposures.

Three Summer Planetaries

25 August 2019, 22:00 – 23:00 BST

The main objective for the evening was photographing the Veil Nebula (West) using 3-minute subs. This is twice as long as anything I’ve attempted before, providing my first real test of the autoguiding set-up. After the inevitable faffing around with polar alignment etc., I got about an hour’s worth of data before my target crossed the meridian.

Conditions: A very mild, still evening (perhaps a little too mild, judging by the sensor temperatures). Once the imaging rig was up and running, I sat down with the XT10 to look at three familiar targets and one not-so-familiar.

M15, globular cluster, Pegasus
Viewed at 240x and 133x (the latter giving the best view on this occasion). Takes a little longer to “get your eye in” on this globular compared to M13, but very rewarding once you do. Nicely resolved, particularly with averted vision.

M27, The Dumbbell Nebula, Vulpecula
9mm Nagler + OIII filter. Very bright with this filter – the apple-core fills in to become a football. But hard to make out detail other than a sharp edge on one side.

NGC 6905, The Blue Flash Nebula, Delphinus
A new object for me; it helps that there’s a large arrow in the sky (the constellation Sagitta) pointing towards it. At 133x it was obvious as a medium to large-sized, round planetary nebula, though I can’t say there was anything particularly blue about it. Appeared to be some brightness variations across the disc, including a slightly darker core. Field star to the north and a fainter one to the east.

M57, The Ring Nebula, Lyra
Beautiful ethereal ring of light. So bright in the XT10 that I can’t really compare it to a smoke-ring anymore; it’s closer to the photographic representation (minus the colour of course). With the OIII filter it was brighter still, and seemed slightly more elongated compared to the unfiltered view.

Nature note
3 frogs in the pond … and 5 tadpoles!