The Crescent Nebula is an emission nebula in the constellation Cygnus, about 5,000 light-years away from Earth. It's formed by the fast stellar wind from a Wolf-Rayet star colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. It was discovered by William Herschel in 1792.
I captured this with narrowband filters to help protect against severe light pollution since I live only 20 minutes from downtown Detroit.
With today's advanced imaging equipment, it no longer has that crescent shape (that its nickname is derived from) since more detail can be revealed.
Follow me on Instagram if you would like to see what's possible to be captured from our own backyard and to see what telescopes I use.
Capture Details:
I captured data from two different years, 2018 and 2019, and combined the data (18.85 of exposure time) to create this image.
Hardware:
Imaging Telescope: Explore Scientific 127mm ED Refractor (952 focal length)
Imaging Camera: ZWO ASI1600MM Cool
Mount: Celestron CGX
Note: A lot of people ask this, but how does my telescope stay on target if the Earth rotates. My camera and telescope sit on a motorized mount and with the help of computer software, it stays on target.
If you wanna know more about Astrophotography, and why you can get such long expsosures, read on.
I'm going to assume you know nothing about cameras, so ilk start from the top.
So each camera has an eye (the sensor). The longer the exposure the more light. However, you also get some blurring effect with moving objects. Example . Long expsosures are good as it gathers more light and these galaixes are very faint in the sky, so you want to capture as much as possible. There is a catch though, the sky moves. If you just took a long expsosure of the night sky it would blur as the stars move.
To combat this, you use a star tracker. These rotate the camera in the opposite direction as the earth spins, so it cancels out the movement. This keeps the image still, so you can take long expsosures. With one, you can do expsosures up to 10minutes where as without one you can only do a few seconds.
However, in the title OP said multiple hours of data. This is where stacking is involved. If you take a bunch of small photos, and stack each one on top you can improve the image. Every photo has this thing called noise, and thats this weird grainy effect. Also high altitude winds can make images look blurry.
To combat this you 'stack' the images. Since the distortions and noise is completely random, you can essentially find the 'true' value of a pixel by finding average of it. However to find an average you need lots of data, which is why you take lots of photos. For an example to find the average age of a classroom you don't take 2 pupils dates, but maybe 15. Same thing. You stack all your photos and your left with a 'stacked image'.
This is where editing comes into play. Editing is probably about 50% of the effort spent and takes a fair amount of skill. I know for my last image I spent 10 or so.hours over a weekend editing my image.
Within editing there are 3 main catagories - Colour, Noise reduction and star reduction. Colour well is essentiually making the Nebula pop out of the screen by only editing that part of the image. Many Astrophotographers edit their nebula using a starless image, as it is a lot easier this way. Colour can also involve making the background 'sky' more even, as light pollsution can cause large brightness differences at the tom and bottom of the image. Star reduction is another crucial part of editing as by making the stars smaller you can also make the nebula seem more visiable. Finally noise reduction, astrophotographers hate noise haha. Not really that crucial unless youre photographing something really dim and you need to 'push' the data a lot, meaning make it brighter, but as a sideeffect you make the noise brighter.
The point of editing isn't to make up colours, instead it's to bring the faint stuff into view. If most of the interesting stuff is between 0-5% brightness, you want to make the 0-5% (the faint stuff), 0-90%. The rest of the stuff you don't really care about gets squished to one end. This is called streching the data.
Image processing is a skill and not really something that comes naturally to a lot of people. I started astrophotography 2 months ago, and this is how much my editing has improved. Both these shots used essentially the same gear. If youre curious this is what the before of the bottom shot looks like, not a lot haha.
chucksastro on March 17th, 2020 at 03:00 UTC »
The Crescent Nebula is an emission nebula in the constellation Cygnus, about 5,000 light-years away from Earth. It's formed by the fast stellar wind from a Wolf-Rayet star colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. It was discovered by William Herschel in 1792.
I captured this with narrowband filters to help protect against severe light pollution since I live only 20 minutes from downtown Detroit.
With today's advanced imaging equipment, it no longer has that crescent shape (that its nickname is derived from) since more detail can be revealed.
Follow me on Instagram if you would like to see what's possible to be captured from our own backyard and to see what telescopes I use.
Capture Details:
I captured data from two different years, 2018 and 2019, and combined the data (18.85 of exposure time) to create this image.
Hardware:
Imaging Telescope: Explore Scientific 127mm ED Refractor (952 focal length)
Imaging Camera: ZWO ASI1600MM Cool
Mount: Celestron CGX
Note: A lot of people ask this, but how does my telescope stay on target if the Earth rotates. My camera and telescope sit on a motorized mount and with the help of computer software, it stays on target.
ghahhah on March 17th, 2020 at 03:48 UTC »
Crescent nebulae or close up of fruity pebble 🤔🤔
LtChestnut on March 17th, 2020 at 05:16 UTC »
how does OP take these images?
If you wanna know more about Astrophotography, and why you can get such long expsosures, read on.
I'm going to assume you know nothing about cameras, so ilk start from the top.
So each camera has an eye (the sensor). The longer the exposure the more light. However, you also get some blurring effect with moving objects. Example . Long expsosures are good as it gathers more light and these galaixes are very faint in the sky, so you want to capture as much as possible. There is a catch though, the sky moves. If you just took a long expsosure of the night sky it would blur as the stars move.
To combat this, you use a star tracker. These rotate the camera in the opposite direction as the earth spins, so it cancels out the movement. This keeps the image still, so you can take long expsosures. With one, you can do expsosures up to 10minutes where as without one you can only do a few seconds.
However, in the title OP said multiple hours of data. This is where stacking is involved. If you take a bunch of small photos, and stack each one on top you can improve the image. Every photo has this thing called noise, and thats this weird grainy effect. Also high altitude winds can make images look blurry.
To combat this you 'stack' the images. Since the distortions and noise is completely random, you can essentially find the 'true' value of a pixel by finding average of it. However to find an average you need lots of data, which is why you take lots of photos. For an example to find the average age of a classroom you don't take 2 pupils dates, but maybe 15. Same thing. You stack all your photos and your left with a 'stacked image'.
This is where editing comes into play. Editing is probably about 50% of the effort spent and takes a fair amount of skill. I know for my last image I spent 10 or so.hours over a weekend editing my image.
Within editing there are 3 main catagories - Colour, Noise reduction and star reduction. Colour well is essentiually making the Nebula pop out of the screen by only editing that part of the image. Many Astrophotographers edit their nebula using a starless image, as it is a lot easier this way. Colour can also involve making the background 'sky' more even, as light pollsution can cause large brightness differences at the tom and bottom of the image. Star reduction is another crucial part of editing as by making the stars smaller you can also make the nebula seem more visiable. Finally noise reduction, astrophotographers hate noise haha. Not really that crucial unless youre photographing something really dim and you need to 'push' the data a lot, meaning make it brighter, but as a sideeffect you make the noise brighter.
The point of editing isn't to make up colours, instead it's to bring the faint stuff into view. If most of the interesting stuff is between 0-5% brightness, you want to make the 0-5% (the faint stuff), 0-90%. The rest of the stuff you don't really care about gets squished to one end. This is called streching the data.
Image processing is a skill and not really something that comes naturally to a lot of people. I started astrophotography 2 months ago, and this is how much my editing has improved. Both these shots used essentially the same gear. If youre curious this is what the before of the bottom shot looks like, not a lot haha.
Wow this is long lol, hope you stuck through it.