Wow, the best-seller book "Understanding (almost) everything about the #climate " by @bonpoteofficiel Anne Brès and Claire Marc (@cnrs @CNRS_INSU) is now fully available online.

This #book is easy to read and understand by everyone, even kids. It is written by climate experts.

Definetely a must-read 📖

here: https://www.calameo.com/read/0064605871f75f8b9ee81

Please share it in your community 🔄

#ClimateChange #climate #Books #IPCC #outreach #science #openaccess #CNRS

Wow, this @xkcd is really excellent.

#Space tip: if you’re ever lost in the inner #solar system, you can just type out the phrase “Optimistic #Aliens measure space typographically” in times new roman and use the dots as a #map

😅

from: https://xkcd.com/2863/

#Astronomy #Meme #Mastodon

#Today, I am celebrating my 4 years without flying ✈️.

The #Earth’s #climate is perturbed by #human activites. One of the easiest things to do towards #sustainability is to cut air travels. Thus, 4 years ago, I cut my frequent flyer cards and decided to #StayGrounded, using only low-#carbon travel means such as #train.

#sobrietyversary #ClimateChange #climatecrisis #globalwarming #climateemergency #sustainabletransport @StayGrounded_net @labos1point5 @academicchatter

“Next year, #SpaceX aims to average one launch every 2.5 days” source: https://arstechnica.com/space/2023/10/next-year-spacex-aims-to-average-one-launch-every-2-5-days/

We have clear evidence now of the impact of #rocket 🚀 launches on the #environment and the #atmosphere, together with the impact of #satellite 🛰️ entries. Still, #Musk wants to increase the frequency of #SpaceX launch next year !

At some point, it will be a crime.

credits: SpaceX

#Space #sustainability #climate #ClimaChange #climatecrisis

@jknodlseder @sundogplanets I thought it was few years for LEO, few decades for MEO and few centuries for GEO (likely the same source).

Bottom line: exact time doesn’t matter, it’s way too long anyway.

The #night #sky in 2023.

This shocking #photography was obtained from #Montana (#USA) over 17 minutes. It reveals the crazy number of #satellites orbiting the #Earth. Most of them are #StarLink (from #SpaceX / #Musk) and aim at providing internet to some remote places.

StarLink is not the only project for space-based #internet: there are also #Kuiper (#Amazon), #oneWeb, #Iris2 (@EU_Commission), etc... which will send even more satellites into #space

#Astronomy

Credits: Matt C. Jackson

@feditips note that the software @sengi_app allows us to schedule toots which includes image description, unlike @apps (from what I could see). Also note that time on fedilab / mastodon is likely in UT and not in local time (Sengi is in local time).

The Mastodon scheduler online tool doesn’t allow us post images at all.

Hey @feditips, any way to efficiently schedule toots with picture attached ? Mastodon scheduling does not allow me to join a picture. Sengi is working fine, but limits to only 20 scheduled toots.

Any other tips ?

Do you want to know how to make #stunning #astronomy #picture of the #night #sky without having a large #telescope ?

So just follow this #thread about #StarTrail or #StarCircle and you shall be able to produce #photography like those attached.

All the #images I will show in this thread are mine and available under Creative Commons Attribution 4.0 International License (CC-BY-4.0). Credits are available in the description.

1️⃣ / XX

2️⃣
The method is quite straightforward: as the Earth rotates along the celestial poles, a long-exposure photography ? of the night sky ? will reveal that stars are trailing. ?

in short, it would like like this ⤵️

3️⃣
As the Earth is spherical, if we point towards the celestial pole, star will slowly trail drawing a circle. If we point towards the celestial equator, star are quickly trailing along a line.

If your field-of-view is large enough, you can even get both the celestial pole and equator.

4️⃣
To make this kind of astrophoto, you don't need to have a telescope. You basically need to drop a camera on a tripod with its lens. Easy.

However, after 30s of exposure, you would get only this. If you have a large field-of-view with your short focal lens, it does not trail much.

5️⃣
if you want to make a star trail, you need to do a very long exposure. This is what you would get over :
- 10 minutes
- 30 minutes
- 1 hour
- 2 hour
The more you can last, the better it is.

6️⃣
The result is available below, after more than 4 hours of exposure.

My record is almost 13 hours of exposure. As an evidence for the long-exposure, you can see that the star Polaris has made half a circule, revealing half of the earth rotation.

But, how can we reach such a long exposure time ?

7️⃣
Long time ago, when we were shooting with film camera, it was so difficult. We were doing just one long-exposure. We had to balance between film sensitivity, focal ratio of the lens and star trail span.

Here is a star trail I did in 2005 with a film camera over 2 hours at 200ISO and f/11. ?

8️⃣
Today, we are using digital camera which is so much better. However, we can't do just one long exposure as with film. Electronic noise does not allow us to do very long exposure. On top of that light pollution will contribute to fill out a bright sky.

If one tries a long exposure of a few hours, he would get something like that, hence a completely saturated image.

Instead of that, we do short (<1 minute) exposure and we then co-added them altogether.

9️⃣
So, what you actually need to do these pictures ?
- a digital camera with a manual or BULB mode
- a stable tripod
- a lens, preferentially with a large field of view
- intervalometer (or something that can control the exposure)

This is what I use: a Canon 5D mk III with a Samyang 14mm f/2.8. The best tripod of the market (from swarovski optik) and a basic intervalometer.

?
My default setup is exposure of 60s every 61s. Star does not move quickly in the sky if you have a short focal length. However, if you leave gaps between 2 pictures, it will make wholes in the start trail, which are not great. This is a zoom of my previous star trail. Earth dash is the result of a 30s trail of a star, and the space between them is the result of 1s interruption to record the image and start the next exposure. Even 1s is enough to be clearly visible in the picture.

1️⃣ 1️⃣
The way I proceed is the following:
1- set up the camera during twilight (before it is dark)
2- point you camera the way you like making sure your camera is perfectly horizontal
3- do the focus (can use auto-focus since it's still bright)
4- put the camera in mode BULB
5- turn OFF the auto-focus and do not touch anymore the lens focus.
6- set the camera sensitivity (up to 6400ISO with my 5DIII)
7- set up the intervalometer
8- come back when it's dark
9- start the sequence
10- wait for long

1️⃣ 2️⃣
11- transfer all frames to a computer
12- use dedicated software to build the startrail. I used softwares like StartStaX, Startrails, etc... depending on whether you are on windows, mac or linux.
(13- submit it to APOD: https://apod.nasa.gov/apod/ap090314.html)

that's it.

So basically, it's 5-10 minutes preparation. Several hours to wait, 5-10 minutes to transfert all the frames to a computer, 5 minutes to process them. ⌚