Conversation

Notices

1. Embed this notice
   Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:34 JST Dr. Alexandre Santerne 🌍

   in reply to

   1️⃣ 4️⃣
   Now, I will give you some advices on how to make GREAT or WOW star trails. Everything is about ... the foreground. You can see star trailing everywhere on earth (although limited by light pollution). So what will make the difference is your foreground !
   As astronomer, I have the opportunity to make star trail from amazing observatories, such as the European Southern Observatory, in Chile. This is from the La Silla observatory.

   • Doughnut Lollipop 【記録係】:blobfoxgooglymlem: likes this.
   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:36 JST Dr. Alexandre Santerne 🌍

     in reply to

     1️⃣ 3️⃣
     Be extremely careful to a few things that happened to me (do not laught at me):
     - check that the lens cap is OUT ?
     - check that the auto-focus is disable (otherwise your camera will spend time failing doing focus)
     - do not leave your polarisation / density filter on ?
     - check that your memory card is not protected in writing ?
     - check that your batteries are full
     - ....

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:37 JST Dr. Alexandre Santerne 🌍

     in reply to

     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. ⌚

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:38 JST Dr. Alexandre Santerne 🌍

     in reply to

     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

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:39 JST Dr. Alexandre Santerne 🌍

     in reply to

     ?
     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.

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:41 JST Dr. Alexandre Santerne 🌍

     in reply to

     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.

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:42 JST Dr. Alexandre Santerne 🌍

     in reply to

     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.

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:43 JST Dr. Alexandre Santerne 🌍

     in reply to

     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. ?

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:45 JST Dr. Alexandre Santerne 🌍

     in reply to

     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 ?

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:46 JST Dr. Alexandre Santerne 🌍

     in reply to

     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.

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:48 JST Dr. Alexandre Santerne 🌍

     in reply to

     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.

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:50 JST Dr. Alexandre Santerne 🌍

     in reply to

     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.

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:52 JST Dr. Alexandre Santerne 🌍

     in reply to

     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 ⤵️

   • Embed this notice
     Dr. Alexandre Santerne 🌍 (alexsanterne@astrodon.social)'s status on Sunday, 18-Dec-2022 23:45:54 JST Dr. Alexandre Santerne 🌍

     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