Dragonflies and Damselflies

[ISv]

Great photo’s!

This is the obelisk posture, to minimize the area exposed to the sun and prevent overheating.

See: https://en.wikipedia.org/wiki/Obelisk_posture

Without knowing the species behavior the explanation "to minimize the area exposed to the sun and prevent overheating" could be misleading for the Obelisk posture: see the link you posted!

 

[Maximilian]

@Maximilian recently posted some pictures of a large white-faced darter or yellow-spotted whiteface (Leucorrhinia pectoralis) in the obelisk posture and has changed his profile picture.

See: https://www.canonrumors.com/forum/threads/dragonflies-and-damselflies.35543/post-1047073

Thank you for noticing and mentioning the change of my profile photo.
I am sure, I will return to the drinking barn swallow someday but that whiteface is IMO one of my best and important (protection of species) photos in 2026.
I recognized that obelisk posture with several dragonfly species, like common and ruddy darters as well. You mentioned in your posts above that a lot of species do it.

 

[Maximilian]

Am I the only poster here who, despite having a great deal of familiarity (and comfort) with the 'metric' system of measurements, prefers the Fahrenheit scale (over the Celsius scale) for discussion of everyday temperatures?

In a way, the Fahrenheit scale is sort of 'metric-y' in that I daresay that the vast majority of humans on earth (?) live in regions where the temperatures generally range from 0-100 degrees Fahrenheit (two powers of ten!).

To answer your question:
It depends on with which system you grew up.

For me as a German and Continental European the Système international d'unités (SI system) is the one to choose And Celsius is closer to Kelvin than any else.

I teach technical training courses where physical calculations are part of everyday work. For customers from every part of the world.
I keep repeating, like a mantra, that you always have to check the units if you don’t use the formula on a daily basis.
When it comes to temperature scales, I always joke that it just depends on which liquid you consider more important in life:
whether it’s water (Celsius) or ethanol (Fahrenheit and Réaumur).
(disclaimer: I know that this is physically not correct. But jokes don't have to be correct )

 

[AlanF]

To answer your question:
It depends on with which system you grew up.

For me as a German and Continental European the Système international d'unités (SI system) is the one to choose And Celsius is closer to Kelvin than any else.

I teach technical training courses where physical calculations are part of everyday work. For customers from every part of the world.
I keep repeating, like a mantra, that you always have to check the units if you don’t use the formula on a daily basis.
When it comes to temperature scales, I always joke that it just depends on which liquid you consider more important in life:
whether it’s water (Celsius) or ethanol (Fahrenheit and Réaumur).
(disclaimer: I know that this is physically not correct. But jokes don't have to be correct )

Everything in this thread has to be correct.

 

[AlanF]

I just had a visitor in my kitchen, who was quite difficult to remove. He ignored all the signs. I suppose the Southern ones can't read.

 

[P-visie]

EDIT #2 (a comment and a question):

Am I the only poster here who, despite having a great deal of familiarity (and comfort) with the 'metric' system of measurements, prefers the Fahrenheit scale (over the Celsius scale) for discussion of everyday temperatures?

In a way, the Fahrenheit scale is sort of 'metric-y' in that I daresay that the vast majority of humans on earth (?) live in regions where the temperatures generally range from 0-100 degrees Fahrenheit (two powers of ten!).

To add to @Maximilian’s answer: The US is the only large country that uses the Fahrenheit scale. Only 11 countries exclusively use Fahrenheit and 8 countries use Fahrenheit next to Celsius.

Source: https://worldpopulationreview.com/country-rankings/countries-that-use-fahrenheit

 

[AlanF]

I thought I had better go out and do some DIF after the Southern Hawker (R5ii + RF 100-500mm). Four-spotted Chaser, Ruddy Darter, and Blacktailed Skimmer.

 

[josephandrews222]

Good comments here. Where I reside, the temperature is almost always between 0 and 100 degrees Fahrenheit...nice round numbers.

And...in my head, when the temperature reaches 100, it is 100% hot, and when it dives to 0, it is really, really cold (0% hot).

So 0-100 works for me, in this narrow context.

I always enjoy teaching the nuts and bolts of the Kelvin scale (in particular its importance in various constants), and this morning learned something new (to me):

However, the kelvin has been redefined in terms of the Boltzmann constant, which relates the amount of thermodynamic energy in a substance to its temperature. When the revised SI was approved in November 2018, the new definition became:

The kelvin, symbol K, is the SI unit of thermodynamic temperature; its magnitude is set by fixing the numerical value of the Boltzmann constant to be equal to exactly 1.380649 × 10-23...J K-1[joules per kelvin].

=====

EDIT...rest of this post has been moved to where it belongs

 

[Click]

I thought I had better go out and do some DIF after the Southern Hawker (R5ii + RF 100-500mm). Four-spotted Chaser, Ruddy Darter, and Blacktailed Skimmer.

Another beautiful series, Alan. Well done.

 

[ISv]

I thought I had better go out and do some DIF after the Southern Hawker (R5ii + RF 100-500mm). Four-spotted Chaser, Ruddy Darter, and Blacktailed Skimmer.

View attachment 230503View attachment 230504View attachment 230505View attachment 230506

"I thought I had better go out and do some DIF"...
I would like to add "or any other wildlife" - usually it's better than just sitting at home (usually!!!)!

 

[Helmi2010]

A few dragonflies—I took most of these photos with a Canon.
The last two shots, the Southern Hawker and the Migrant Hawker, were focused manually.
I used to have better eyesight and reflexes...
Nowadays, I use a combination of MF and AF: MF for rough focusing, and AF for fine-tuning.


Feuerlibelle by Helmut Gloor, auf Flickr

Herbst-Mosaikjungfer by Helmut Gloor, auf Flickr

2018 fotografiert, 2026 auf einer alten Speicherkarte entdeckt by Helmut Gloor, auf Flickr

Herbst-Mosaikjungfer by Helmut Gloor, auf Flickr


Aeshna cyanea by Helmut Gloor, auf Flickr

Migrant Hawker by Helmut Gloor, auf Flickr

 

[AlanF]

Good comments here. Where I reside, the temperature is almost always between 0 and 100 degrees Fahrenheit...nice round numbers.

And...in my head, when the temperature reaches 100, it is 100% hot, and when it dives to 0, it is really, really cold (0% hot).

So 0-100 works for me, in this narrow context.

I always enjoy teaching the nuts and bolts of the Kelvin scale (in particular its importance in various constants), and this morning learned something new (to me):

However, the kelvin has been redefined in terms of the Boltzmann constant, which relates the amount of thermodynamic energy in a substance to its temperature. When the revised SI was approved in November 2018, the new definition became:

The kelvin, symbol K, is the SI unit of thermodynamic temperature; its magnitude is set by fixing the numerical value of the Boltzmann constant to be equal to exactly 1.380649 × 10-23...J K-1[joules per kelvin].

=====

EDIT...rest of this post has been moved to where it belongs

And so when it is 50, it's exactly midway in between and so lovely and warm, just right. The beauty of the definition of K in SI for us is that if you know the internal energy of a dragonfly, you divide it by 1.380649 × 10-23...J K-1[joules per kelvin] and you know its temperature in K.

 

[Click]

Excellent series, Helmut. I really like the first shot.