Starship Asterisk*

Bird_Man wrote: ↑Sat Apr 13, 2024 8:37 pm

johnnydeep wrote: ↑Sat Apr 13, 2024 4:00 pm One of the links mentions that the length of totality varies - significantly - at different locations. Why is this? Complex orbital motions or something simpler?

https://science.nasa.gov/solar-system/skywatching/how-is-the-2024-total-solar-eclipse-different-than-the-2017-eclipse/ wrote:In April, totality will last longer than it did in 2017. Seven years ago, the longest period of totality was experienced near Carbondale, Illinois, at 2 minutes, 42 seconds.

For the upcoming eclipse, totality will last up to 4 minutes, 28 seconds, in an area about 25 minutes northwest of Torreón, Mexico. As the eclipse enters Texas, totality will last about 4 minutes, 26 seconds at the center of the eclipse's path. Durations longer than 4 minutes stretch as far north as Economy, Indiana. Even as the eclipse exits the U.S. and enters Canada, the eclipse will last up to 3 minutes, 21 seconds.

During any total solar eclipse, totality lasts the longest near the center of the path, widthwise, and decreases toward the edge. But those seeking totality shouldn’t worry that they need to be exactly at the center. The time in totality falls off pretty slowly until you get close to the edge.

Is it simply due to the different shadow widths? Or is the speed of the orbit also involved?

It appears that the moon is closer, making the shadow bigger and that causes totality to last longer. this article from Space.com seems to explain that. https://www.space.com/how-total-solar-e ... lar-eclips

During the peak of the 2017 eclipse, the moon was 231,155 miles (372,008 km) from Earth, while on April 8, it will be 223,392 miles (359,515 km) away. On April 8, the moon will be a couple thousand miles closer, so its conical shadow that falls on Earth will have a larger diameter. In 2017, the path of totality was 62 to 71 miles wide, according to NASA, while on April 8, it will range between 108 and 122 miles wide, covering much more of Earth.

johnnydeep wrote: ↑Sat Apr 13, 2024 4:00 pm One of the links mentions that the length of totality varies - significantly - at different locations. Why is this? Complex orbital motions or something simpler?

https://science.nasa.gov/solar-system/skywatching/how-is-the-2024-total-solar-eclipse-different-than-the-2017-eclipse/ wrote:In April, totality will last longer than it did in 2017. Seven years ago, the longest period of totality was experienced near Carbondale, Illinois, at 2 minutes, 42 seconds.

For the upcoming eclipse, totality will last up to 4 minutes, 28 seconds, in an area about 25 minutes northwest of Torreón, Mexico. As the eclipse enters Texas, totality will last about 4 minutes, 26 seconds at the center of the eclipse's path. Durations longer than 4 minutes stretch as far north as Economy, Indiana. Even as the eclipse exits the U.S. and enters Canada, the eclipse will last up to 3 minutes, 21 seconds.

During any total solar eclipse, totality lasts the longest near the center of the path, widthwise, and decreases toward the edge. But those seeking totality shouldn’t worry that they need to be exactly at the center. The time in totality falls off pretty slowly until you get close to the edge.

Is it simply due to the different shadow widths? Or is the speed of the orbit also involved?

Chris Peterson wrote: ↑Sat Apr 13, 2024 6:38 pm

johnnydeep wrote: ↑Sat Apr 13, 2024 6:17 pm

Chris Peterson wrote: ↑Sat Apr 13, 2024 4:05 pm

PNG is good for graphics and text images, because it is usually written in a lossless format (but it doesn't have to be... lossy PNG creates much smaller files, more similar to JPEG). So for screen captures, PNG is usually a better format unless you actively require a small file and can accommodate some artifacts. As noted by the OP, there's rarely a reason to use PNG for photographic images.

FWIW, the MS snipping tool can write JPEG files, and if you tell it to do so, it will write all future captures that way until you change back.

Well, it seems I always have to change the default Snipping tool format to JPG, or else it reverts back to PNG the next time I launch it. Is the change supposed to last between app closings/restarts? The same thing happens with the default file save folder: always reverts back to some folder I don't want on OneDrive.

For me, it always saves in the same format I previously used. I don't see it reset itself to PNG. It also tries to save to the last folder I used. I have the option to automatically save disabled. This is under Win 11 with Snipping Tool 11.2303.17.0 (visible in the settings dialog).

johnnydeep wrote: ↑Sat Apr 13, 2024 6:17 pm

Chris Peterson wrote: ↑Sat Apr 13, 2024 4:05 pm

johnnydeep wrote: ↑Sat Apr 13, 2024 3:59 pm

Interest - thanks. At times I've often wondered - briefly - why a PNG format file is so much larger than a JPEG and now I know! Never took an interest in the particular formats used in the APODs though. I guess my connection speed is fast enough.

PNG is also the default format that the MS Snipping tool saves in, which is why PNG format annoys me, since I often use it.

PNG is good for graphics and text images, because it is usually written in a lossless format (but it doesn't have to be... lossy PNG creates much smaller files, more similar to JPEG). So for screen captures, PNG is usually a better format unless you actively require a small file and can accommodate some artifacts. As noted by the OP, there's rarely a reason to use PNG for photographic images.

FWIW, the MS snipping tool can write JPEG files, and if you tell it to do so, it will write all future captures that way until you change back.

Well, it seems I always have to change the default Snipping tool format to JPG, or else it reverts back to PNG the next time I launch it. Is the change supposed to last between app closings/restarts? The same thing happens with the default file save folder: always reverts back to some folder I don't want on OneDrive.

Chris Peterson wrote: ↑Sat Apr 13, 2024 4:05 pm

johnnydeep wrote: ↑Sat Apr 13, 2024 3:59 pm

DanielCuriousLayman wrote: ↑Sat Apr 13, 2024 11:46 am Hello!

Today's APOD image is considerably larger in file size than it needs to be, as it's been saved using the PNG format. It should likely be using JPEG instead. I am referring to the image at this path: https://apod.nasa.gov/apod/image/2404/p ... lm1024.png

I have confirmed I can download the approximately 1 Megabyte PNG file and re-save in PNG format and achieve something like a 78% file size reduction to bring down to around 215 Kilobytes.

It's possible few APOD users will notice, what with prevalence of high-speed broadband these days, but I thought I'd share this IT professional's suggestion anyway!

By the way, for those curious:

PNG is excellent for images that feature sharp lines and flat colors, such as screenshots of computer software. As PNG is a 'lossless' encoder, it's ideal at preserving the fine structure in things like logos, Excel spreadsheets, charts, info graphics, etc. Additionally, PNG supports images having regions of transparency where a background color or image can 'peek through', something you can't do with JPEG.

JPEG is an excellent choice for non-professional photography where lossy encoding is acceptable. It's a particularly good choice for photographic images that have already been modified and edited in a higher-quality 'RAW' format before being saved again for distribution to others, including over the internet. It provides a reasonable balance between image quality and file size. It is worth reiterating that not only is JPEG lossy, it also suffers from something called 'generation loss', where repeatedly decoding and re-encoding an image to save it again causes a loss of information each time, degrading the image.

Anyway, thanks for having me!

Daniel
Melbourne, Australia

Interest - thanks. At times I've often wondered - briefly - why a PNG format file is so much larger than a JPEG and now I know! Never took an interest in the particular formats used in the APODs though. I guess my connection speed is fast enough.

PNG is also the default format that the MS Snipping tool saves in, which is why PNG format annoys me, since I often use it.

PNG is good for graphics and text images, because it is usually written in a lossless format (but it doesn't have to be... lossy PNG creates much smaller files, more similar to JPEG). So for screen captures, PNG is usually a better format unless you actively require a small file and can accommodate some artifacts. As noted by the OP, there's rarely a reason to use PNG for photographic images.

FWIW, the MS snipping tool can write JPEG files, and if you tell it to do so, it will write all future captures that way until you change back.

johnnydeep wrote: ↑Sat Apr 13, 2024 3:59 pm

DanielCuriousLayman wrote: ↑Sat Apr 13, 2024 11:46 am Hello!

Today's APOD image is considerably larger in file size than it needs to be, as it's been saved using the PNG format. It should likely be using JPEG instead. I am referring to the image at this path: https://apod.nasa.gov/apod/image/2404/p ... lm1024.png

I have confirmed I can download the approximately 1 Megabyte PNG file and re-save in PNG format and achieve something like a 78% file size reduction to bring down to around 215 Kilobytes.

It's possible few APOD users will notice, what with prevalence of high-speed broadband these days, but I thought I'd share this IT professional's suggestion anyway!

By the way, for those curious:

PNG is excellent for images that feature sharp lines and flat colors, such as screenshots of computer software. As PNG is a 'lossless' encoder, it's ideal at preserving the fine structure in things like logos, Excel spreadsheets, charts, info graphics, etc. Additionally, PNG supports images having regions of transparency where a background color or image can 'peek through', something you can't do with JPEG.

JPEG is an excellent choice for non-professional photography where lossy encoding is acceptable. It's a particularly good choice for photographic images that have already been modified and edited in a higher-quality 'RAW' format before being saved again for distribution to others, including over the internet. It provides a reasonable balance between image quality and file size. It is worth reiterating that not only is JPEG lossy, it also suffers from something called 'generation loss', where repeatedly decoding and re-encoding an image to save it again causes a loss of information each time, degrading the image.

Anyway, thanks for having me!

Daniel
Melbourne, Australia

Interest - thanks. At times I've often wondered - briefly - why a PNG format file is so much larger than a JPEG and now I know! Never took an interest in the particular formats used in the APODs though. I guess my connection speed is fast enough.

PNG is also the default format that the MS Snipping tool saves in, which is why PNG format annoys me, since I often use it.

https://science.nasa.gov/solar-system/skywatching/how-is-the-2024-total-solar-eclipse-different-than-the-2017-eclipse/ wrote:In April, totality will last longer than it did in 2017. Seven years ago, the longest period of totality was experienced near Carbondale, Illinois, at 2 minutes, 42 seconds.

For the upcoming eclipse, totality will last up to 4 minutes, 28 seconds, in an area about 25 minutes northwest of Torreón, Mexico. As the eclipse enters Texas, totality will last about 4 minutes, 26 seconds at the center of the eclipse's path. Durations longer than 4 minutes stretch as far north as Economy, Indiana. Even as the eclipse exits the U.S. and enters Canada, the eclipse will last up to 3 minutes, 21 seconds.

During any total solar eclipse, totality lasts the longest near the center of the path, widthwise, and decreases toward the edge. But those seeking totality shouldn’t worry that they need to be exactly at the center. The time in totality falls off pretty slowly until you get close to the edge.

DanielCuriousLayman wrote: ↑Sat Apr 13, 2024 11:46 am Hello!

Today's APOD image is considerably larger in file size than it needs to be, as it's been saved using the PNG format. It should likely be using JPEG instead. I am referring to the image at this path: https://apod.nasa.gov/apod/image/2404/p ... lm1024.png

I have confirmed I can download the approximately 1 Megabyte PNG file and re-save in PNG format and achieve something like a 78% file size reduction to bring down to around 215 Kilobytes.

It's possible few APOD users will notice, what with prevalence of high-speed broadband these days, but I thought I'd share this IT professional's suggestion anyway!

By the way, for those curious:

PNG is excellent for images that feature sharp lines and flat colors, such as screenshots of computer software. As PNG is a 'lossless' encoder, it's ideal at preserving the fine structure in things like logos, Excel spreadsheets, charts, info graphics, etc. Additionally, PNG supports images having regions of transparency where a background color or image can 'peek through', something you can't do with JPEG.

JPEG is an excellent choice for non-professional photography where lossy encoding is acceptable. It's a particularly good choice for photographic images that have already been modified and edited in a higher-quality 'RAW' format before being saved again for distribution to others, including over the internet. It provides a reasonable balance between image quality and file size. It is worth reiterating that not only is JPEG lossy, it also suffers from something called 'generation loss', where repeatedly decoding and re-encoding an image to save it again causes a loss of information each time, degrading the image.

Anyway, thanks for having me!

Daniel
Melbourne, Australia