Iris Nebula, NGC7023

Iris Nebula
Iris Nebula

Reprocessed with yet more data. I don’t know that this is significantly better than my previous results ( here and here and here ). But NGC7023 is a fascinating object, and I will probably return to it for the rest of my life. As always, the images available from Wikipedia are worth a pause.

IC2574

IC2574
IC2574

IC2574 is the faint smudge in the center, 13 million light-years away. A dim dwarf spiral galaxy. According to Wikipedia, approximately 90% of its mass is dark matter.

Taken with a 110mm F/7 refractor. Total exposure time is about 13 hours.

Annotated IC2574
An annotated version

 

M63

M63

Sometimes referred to as “the Sunflower Galaxy”. This image has about 7 hours total exposure time.  It is quite a pretty galaxy — if you zoom in (ie, click on the picture), it looks like a swirl of altocumulus clouds on a spring day.

 

M102

M101

M102 is a difficult object for my setup and conditions. It is, apparently, known as the “Spindle Galaxy”.

A five or six times blowup of the above image does manage to show the “spindle”, barely:

This Hubble image gives a better idea of how it got the name.

Another M101

M101
M101

I am slowly accumulating more time on M101. This image is over 8 hours total exposure, under generally poor conditions — not quite double the previous version. It’s a good thing the telescope mostly runs unattended.

The blurred spot in the lower right corner is NGC 5474, a true physical companion of M101 that is classified as a “peculiar dwarf galaxy”.

The above image is without noise reduction processing.

Here’s a version with PixInsight’s “Multiscale Linear Transform” noise reduction:

M101 with PixInsight noise reduction

And here it is with Gimp’s noise reduction algorithm:

M101 with Gimp noise reduction

It is hard to tell the difference. A large-screen monitor is probably helpful.

[Edit: I tried looking at this post on my phone. The experience is just not the same as on my desktop monitor. Well, duh.]

Heroes of another kind

Posted on wall at Castle Wertheim
Posted on the walls of Castle Wertheim, high above the town of Wertheim

April Fools is a widespread tradition, so I am suspicious of this placard posted on the walls of Castle Wertheim.

Fountain in Seville

Accidents happen.  The stop in Seville was less than ideal: dock in Cadiz, catch an early morning bus, then a walking tour of a couple of high points of Seville. Back to the bus, back to the ship. I don’t remember taking this picture, but there are many other images of the area on my camera, so I must have. Anyway, I thought it was nice:

Seville

It’s a color image, though it looks B&W.

La Palma

La Palma is rugged.

One of the finest astronomical sites on Earth hides serenely above those clouds.

The people of La Palma are proud of their astronomical connection — here’s a signpost from a roadside viewpoint:

Polaris:4,077,487,635,167,800km

There are about 20 large telescopes on the top of the North Peak.

On September 19, 2021, a major volcanic eruption took place on La Palma.  Lava flows wiped out a relatively small part of the island, but our guide told us ash falls covered a large area — “like very fine black flour”. We didn’t see any sign of the ash seven months later. The eruption wasn’t a severe problem for the large telescopes, though a couple of instruments were affected.

La Palma is also very green.

Hikers in a deep green canyon

It’s a short hike to the waterfall up ahead:

Note the green metal railings, the rectangular cave mouth, and the concrete structures going back further up the canyon– this is a developed park, not a wilderness area. The canyons are deep and rugged but still modified by human occupation.

This canyon has been developed as a source of fresh water but retains a wild scenic character — a mix of community park, water project, and wilderness area. Further down the trail was an open rectangular water tank, 10′ x 10′ x 6′ deep, with the same damp old concrete.

On the trail to the waterfall

Down the canyon, the almost vertical walls were terraced.

Terraces in the canyon wall

(The picture is misleading. It’s perhaps a hundred feet from the flowers in the foreground to the trees across the canyon; the canyon floor is a hundred feet below.)

A mile or so further, the canyon widens, and the terraces are well-tended:

People have been living here for a long time.


Well, there was more, but this post is too long already. La Palma was my favorite of our stops. It is unlikely we will ever be there again, but if I had another life, I would like to spend more time there.

Grammar Gripe

There is a rule about punctuation I can’t bring myself to follow: “In the United States, commas and periods go inside the quotation marks”. I just broke it there.

The rule I follow is that everything inside the quotation marks is part of the quote:

Here is a quoted fragment of text: “a quoted fragment of text:”.

The “:” inside the quotes is part of what is quoted. The “.” defines the sentence structure.

Or consider:

A. The final “word”.

vs

B. The final “word.”

B looks strange to me — the period is part of the sentence structure, not part of the quoted text, so B is a sentence without its final period. It should be

B. The final “word.”.

if you want to quote

“word.”

What about even stranger cases:

Brian flew to a place in the clouds where punctuation marks included  “%$^&”.

I think like this because of long exposure to computer languages, where the syntax rules are much more regular. You can always distinguish between the syntactically live use of punctuation and syntactically lifeless punctuation inside quotes. Any text can be unambiguously quoted.

English usage is like a woodland path — it is where it is because that’s where people walked. For many years I walked somewhere else, and I’m very comfortable there.

Rough Seas

Last night was a rough passage for a landlubber like me, with strong winds and 10-foot swells. The night before, the ship was rocking, but last night it was pounding. The captain apologetically announced that conditions would be a bit uncomfortable, but our situation wasn’t bad, and just enough to remind us that we were really at sea.

Of course, it can get much worse — here’s a youtube video where it was substantially worse — you can hear an authentic example of the emergency signal (7 short blasts, then a long one).

The rocking motions are roll, pitch, and yaw, like an airplane. Yaw wasn’t noticeable, but roll and pitch were strong enough to make it impossible to walk in a straight line. Roll and pitch are rhythmic vertical motions, with the ship’s buoyancy trying to return to level. Roll had a period of a few seconds; pitch had a longer duration. (On the other hand, yaw is a horizontal rotation with no vertical component and no passive returning force. A yaw motion is essentially a tiny course change that requires autopilot or human correction to undo.)

Of course, all these motions combine unpredictably. The ship moves as a rigid body in a complex dance, and as long as it’s not too bad, you can enjoy it.

However, when conditions got slightly worse, the water slapped the hull explosively, and a new form of motion manifested. Rather than moving as a rigid body, the ship vibrated like a colossal gong, with a pitch of about 1.5Hz. This ringing sometimes persisted for several seconds (though generally less than 10 seconds). I suspect this vibration came from the waves striking the ship’s bow at an angle.

When the ship slammed even harder, though, sometimes there was a higher frequency vibration, maybe 5Hz, that decayed within 2-3 seconds — a violent shaking motion that rattled small objects.

These vibratory modes must be from the flexing of the ship itself, and the frequencies probably reflect the natural resonant frequencies of the ship.