#nebulae

M27 Dumbbell Nebula

250P - 25mm + UHC (48x)

Low powers are best here. Faint elliptical outline. Very rich star field. Obvious two-lobed.

Twilight glow now visible.

M57 Ring Nebula

250P - 2.5x Barlow + 10mm (300x)

a slightly oval, ghostly donut. I suspect there is a bright bit in the core.

A "UHC" Filter or Ultra-High-Contrast filter, is a little bit of special green film you can screw onto your eyepiece or camera. It blocks all wavelengths of light except for the ones emitted by oxygen and hydrogen within nebulae (the O-III and H-beta lines). The purpose is to cut down on light pollution. This probably worked a little better when we used sodium bulbs rather than LEDs, but it does still work a little bit on emission nebulae and planetary nebulae. Note that it won't work on stars and things made of stars (galaxies and star clusters), because stars emit a continuous spectrum and you're blocking out starlight just as much as the light pollution.

I use a UHC filter fairly often on planetary nebulae, since the O-III line is generally very bright in these objects. I've also had luck with a dedicated narrowband O-III filter.

I have a fun little anecdote about Messier 57. This story was relayed to me by the former director of the observatory I volunteer at, originally told by San Francisco sidewalk astronomer and telescope builder John Dobson. Dobson was showing off M57 with a large aperture telescope in a star party in a national park, and a kid came up to look through the eyepiece, stopped, and gasped. "That looks like the ghost of a cheerio," they said.

NGC 2371 Planetary Nebula in Gemini

200x w/ UHC - 250P

Bortle 5

The right lobe of this two-lobed PN is brighter and more concentrated. The other lobe is dimmer but not any harder. I can see it with direct vision but [illegible] needs averted vision. A vanishingly thin haze connects the 2 lobes. Nice, but difficult challenge.

This one is a bit off the beaten path. You won't see this recommended in beginner's guides, and it's not in the famous Messier catalogue. I found it in Skiff & Luginbuhl's Observing Handbook. It's one of my prouder finds--remember that I'm pointing my telescope manually using star atlases and pattern recognition to locate objects.

This is essentially another dumbbell-style nebula, but with even less equatorial material, and much much smaller or more distant. Compare this nebula at 200x with the Dumbbell at 48x--the latter is much larger.

The funny thing about amateur astronomers with big telescopes is that you end up chasing objects that are difficult to detect and don't look very big or dramatic. Once you've seen the big showpiece objects enough times you start to want to go deeper, so it is not so uncommon that an amateur astronomer will be very pleased just to see a faint fuzzy dot.

Of course some people go the other way, reasoning that if there is joy to be had in faint fuzzy dots, may as well use very small telescopes and look for just the showpiece objects. I'll do a post on small-scope observing before too long.

Also in Gemini is NGC 2392, mislabelled here as 2932. Due to a resemblance in photographs to a head in a fuzzy parka, the nebula's official name refers to a slur used against the Inuit people, so let's all agree to not call it that, and call it the Clown Face or the Lion's Mane nebula instead.

This one is a more attainable beginner's object, listed in various more beginner-friendly resources, and I've see it in telescopes as small as 80mm aperture.

It's a roughly spherical bubble of a nebula, with its central star still plainly visible. A star of similar brightness is visible not far away, so you can make sure your telescope is actually focused and what you are seeing is not just an unfocused star!

2021-February-7-08:00 PM EST

Near Wasat in Gemini.

NGC 2392[sic] is clearly nonstellar with 10" Dobsonian at 48x. With a neighbor of similar magnitude which is a regular star.

63 Geminorum & NGC 2923. 10" Dob, 25mm Plossl, 48x. (sketch of full fov)

NGC2923[sic], 10" Dob, 6mm Goldline, 2.5x Barlow. (sketch of magnified view in a box)

I can easily see the central star! The nebula is a round, featureless puff which is bright at the center and dims at the edges.

With a UHC filter, it seemed like there was some mottled/patchy structure in the nebula. Hard to hold onto.

There are a few decent planetary nebulae that I don't have pictures of but which are attainable at a beginner-to-intermediate level. The Saturn Nebula (so named due to its elliptical shape), the Blue Snowball nebula (so named as it's relatively easy to see its color).

This one is a favorite of mine. This is winter/spring open star cluster Messier 46 in Puppis. It's right next door to a showpiece cluster M47, and it's not hard to find using a star hop off the legs of Canis Major. But in the background of the star cluster is NGC 2438, a planetary nebula! This drawing was with a 5" tabletop-dob telescope--much smaller than the 10" dob I've been using for most of these drawings.

Zhumell Z130 - 15mm Goldline + 2.5x Barlow (108x)

Messier 46 cluster & Planetary Nebula

Both the cluster's stars and the nebula are very faint, but the PN is certain with averted vision, in the view with the UHC filter. Stars drawn without UHC, nebula drawn with UHC. Without UHC, the nebula is juuuussssttt barely visible, suspected, but the UHC view confirms it.

The nebula itself is fairly difficult to see from light polluted areas, sometimes requiring averted vision (i.e., pay attention to where the nebula is, but point your eyes away from it. this uses more light sensitive cells at the edge of your retina). But since the star cluster is relatively easy to find, it's a good thing to try, and useful for training yourself to see faint objects.

2021-July-12 10:40 PM EDT

NGC 6572 - Planetary Nebula in Ophiuchus

10" f/5 Dobsonian, 2.5x Barlow, 7mm 58° eyepiece, 429x, UHC filter

The planetary nebula is a brilliant pale-blue at low power, its color and peculiar behavior under averted vision being the only thing which reveals its non-stellar nature. At 171x, it is noticeably elongated and yet retains significant surface brightness at a small size. It is almost stellar at first glance. At 429x, with the UHC filter, the blue coloration is even more dramatic and the nebula becomes a bright blue ball with a slightly dimmer elliptical fringe elongated N/S, and slightly more sharply elongated in the North.

I also observed the object with the CPC800 (8", 250x, no filter) belonging to the Observatory, during a practice session on the Thursday before our re-opening to the public. It almost seemed to show a little better contrast though less saturation, and I felt it had a bit sharper edges and pointier ends. But this is the sort of thing your brain imagines. I got a brief impression out of observatory director--something to the effect of "nice color." (Later: but not large or obvious enough to show during public nights.) Another observatory volunteer mistook it for a star at first.

This is another difficult one off the beaten path, I think this was either for a Roger Ivester Observer's Challenge or another one I found in the Observer's Handbook.

I believe this one was indeed from a Roger Ivester Observer's Challenge, and my observation was included in the observing report compilation. Oh! Also this was the night my dog got skunked, which put an end to my observing session that night.

The text from my report reads:

Here is my sketch of Messier 76 from 2020 December 5th at around 7:30 PM EST from Bortle 6 skies, including a visual description of the star hop I used to find it:

M76 is close to halfway between Ruchbah in Cassiopeia and Almach in Andromeda. Closer to a third from Almach to Ruchbah is a 3.8th magnitude star called Nembus, which is part of a noticeable trapezoidal asterism in an 8x50mm finderscope. Near that trapezoid is a square/paralellogram. Following it northeast you reach a star of similar magnitude to the square stars, and going farther east you reach a wide optical double star Phi Persei (3.9th mag). Go from Phi in the opposite direction from its companion, and you'll reach a star of about the same magnitude as that companion, and just west of that is M76.

M76 wasn't visible to me in my conditions with the finderscope, but it was easily visible as nonstellar at 38x, with a noticeable hint of two-lobed structure. The star to the east is easily visible in the finderscope and you could probably hop directly to it from the finderscope.

notes read:

Messier 76, "Little Dumbbell." SkyWatcher FlexTube 250P. 10mm Plossl [120x] + UHC Filter. Nebula can be seen w/ direct vision as a two-lobed object. It is brighter w/ [averted] vision.

This is quite a pretty little nebula and how easily its structure is made apparent is quite pleasant. It isn't high surface brightness, but the view through the 10" dob at 120x reminds me of the Dumbbell with the 6" Dobsonian at 38x.

My notes from November 13th, 2017, while I was taking Observational Astronomy 251 in college, using the 24" CDK at the Observatory:

M76 - Planetary Nebula. 28mm [142x]. Little Dumbbell. More obviously separated lobes than Big Dumbbell, but dimmer. w/ averted vision, an ellipse holds M76's lobes within.

w/ OIII Filter, averted vision reveals better view of elliptical bubble. Each lobe is more obviously separated, and one lobe is significantly brighter. Good one to show! [at friday night public viewing sessions]

Finally, some sketches from my 2020 astronomy log, done on graph-paper so it's not as pretty:

M27: SkyScanner 100 (4" tabletop dob, sort of on the limit between toy and serious. This scope, nicknamed 'Rover,' belongs to my friend @thefallencomet). Faint, small smudge, but the two lobed structure is--just barely--visible.

Here are the ring nebula and the dumbbel nebula (as well as the whirlpool galaxy--more on galaxies in a future post), with a 6" Dobsonian.

2020-August-9 09:31 PM EDT.

New constellation under summer triangle. "Delphinus." I'm sure I've seen it before, but it's usually too dim to see with naked eye.

Ring Nebula. 15mm 2.5x DT6 (200x)

Strikingly beautiful even at 200x. Pale ghostly green color. Averted vision at 15mm without barlow (80x) reveals hints of bright core / central star. 10/10 object.

9:44 PM -- very dark. 10% clouds going through south & east sky.

M27 - 32mm - DT6 (37.5x)

Wow. Dumbbell is easily visible. Secondary elliptical region perpindicular to dumbbell visible with averted vision.

DT6 - 32mm (37.5x) M51 Whirlpool Galaxy