Orion Nebula
- Thread starter John999R
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John999R
Member
Here is a multiple long exposure image of the Orion Nebula accompanying on the left side by the Running Man Nebula. I took this over a year ago from my backyard and from what I recall it was composed of approximately 24-30 sub-exposures ranging from 15 seconds to 3+ minutes. The maximum dictated by the histogram and light pollution. The 15-second exposures were to dampen the bright Orion core of stars called the Trapezium. I also took 20-24 darks at the same 800 ISO and exposure lengths during the same session because the ambient temperature between lights and darks must be equal. The darks were for noise subtraction in post processing purposes in PS. I also added a number of flat frames from a previous session and fast 1/4000 bias frames. Temp equalization is not a factor in flats and bias frames. This image was my early attempt at working with PS, but in the future I would increase the subs by 2x-3x and if I could, I would go to a darker sky location and limit the affects of light pollution.
I used a Canon 60Da DSLR. This camera has a factory modified sensor to allow more of the Ha wavelength to hit the sensor, Ha is common in nebulas and shows red. The Orion is a diffuse nebula, showing emission and reflection nebulas in the complex, which is huge by galactic measurements and encompasses a big chunk of sky. The above image encompasses just a small part of the region. The Running Man Nebula on the left is considered a reflection nebula, illuminated by giant blue stars. I didn't capture the extent of the blue within the Running Man, my processing skills fell short.
My pursuit of deep sky imaging is on a leave of absence for the foreseeable future as I'm dealing with an ill-performing mount, which is currently back at the factory again. It's tracking and guiding performance has been sub-standard since I bought it used a couple years back. I bought a replacement mount last year, but I won't start the learning curve until the current problem mount is fixed. I also have some medical issues to overcome before I can consider any serious effort again in this hobby.
I used a Canon 60Da DSLR. This camera has a factory modified sensor to allow more of the Ha wavelength to hit the sensor, Ha is common in nebulas and shows red. The Orion is a diffuse nebula, showing emission and reflection nebulas in the complex, which is huge by galactic measurements and encompasses a big chunk of sky. The above image encompasses just a small part of the region. The Running Man Nebula on the left is considered a reflection nebula, illuminated by giant blue stars. I didn't capture the extent of the blue within the Running Man, my processing skills fell short.
My pursuit of deep sky imaging is on a leave of absence for the foreseeable future as I'm dealing with an ill-performing mount, which is currently back at the factory again. It's tracking and guiding performance has been sub-standard since I bought it used a couple years back. I bought a replacement mount last year, but I won't start the learning curve until the current problem mount is fixed. I also have some medical issues to overcome before I can consider any serious effort again in this hobby.
Birds are so much easier to photograph. 
Wow, impressive shot and also impressive technique. I think I understood about 75% of what you said there. I do have a couple of questions though, if you don't mind.
First of all, what is a "bias frame"? Almost sounds like it's what the camera does for noise reduction, where it's used as a comparison? Is it something along those lines, or something totally different?
Second and third questions, which are probably related.
2) What are you using for a lens? Shooting through a telescope I presume?
3) I don't see mention of one critical component. In my very basic and simple astro-photography experimentation, I learned that stars blur quite quickly, say at about 25 seconds even at wide angles. I'm sure it's much worse at this magnification. If you're shooting through a telescope, presumably it has some sort of a tracking system that you're using? How does all this stuff fit together? (I won't even bother asking about cost, if you have to ask...)
First of all, what is a "bias frame"? Almost sounds like it's what the camera does for noise reduction, where it's used as a comparison? Is it something along those lines, or something totally different?
Second and third questions, which are probably related.
2) What are you using for a lens? Shooting through a telescope I presume?
3) I don't see mention of one critical component. In my very basic and simple astro-photography experimentation, I learned that stars blur quite quickly, say at about 25 seconds even at wide angles. I'm sure it's much worse at this magnification. If you're shooting through a telescope, presumably it has some sort of a tracking system that you're using? How does all this stuff fit together? (I won't even bother asking about cost, if you have to ask...)
John999R
Member
Hello Bob, Many cameras do have some form of internal noise reduction, if it's to reduce read noise then that is the same purpose of taking bias frames in astrophotography. However, in astrophotography, it is recommended that all camera functions like noise reduction, dust elimination, image processing and the like be turned off and shoot only in raw format. Those internal camera features can contribute to increased noise, whether electronic or thermal. Some cameras go too far processing images internally, like mistaking stars for noise and making them disappear. I've heard the Canon line has the least amount of internal image manipulation in raw shooting, it also helps most capture, guiding and processing software is Canon compatible. But, other brands are making their mark in this hobby, I expect to see more shifts in the near future.
Any kind of photography produces ADC readout or offset signal and bias frames are intended to capture the resulting noise. Some imagers contend taking bias frames have no appreciable gains, so they don't bother with them. I haven't personally compared my images with and without bias frames, I simply try and do what is recommended. However, taking a series of 50 to 100 bias frames is easy and some people don't know you have to take a lot of them to get any positive feedback. I have also created a library of bias frames and apply them as needed. You only have to take a series of bias frames a couple times a year, place them in a file so they are readily available anytime you want to use them. Depending on the quality of the image and duration, I may skip applying bias frames and flat frames and only apply darks. All of these elements are designed to reduce noise and uneven illumination. You can also create a library for flat frames and even dark frames too, but the darks must match the ISO, duration, and temperature of the lights, I've never explored making a dark frame library because of the many changes in temperatures from night to night, I just take them after each imaging session. However, you could set them aside and note the prevailing temps for each dark frame. The durations are already indicated and you could apply them to a future image session if they meet the same spec as your light frames. In short, aside from your light frames, corresponding darks, flats, bias and even flat darks have their own requirements.
Most of my sessions have been plagued with tracking and guiding issues and that is where I spend a lot of time trying to resolve. My mount is currently under repair at the factory and hopefully, they will fix it this time. Not achieving round stars in a deep sky image is a reject, that is why I haven't composed more photos. Even the ones I have processed, the stars are not what they should be, but I go through the motions for the sake of practice and learning anyway.
In response to your second question, I've only used a camera lens once to take any Milky Way shots, except for a rare shot of the moon, but camera lenses are used all the time in astrophotography, not just for the common Milky Way with foreground shots either. They are popular for wide field astrophotography and I've seen many beautiful compositions. Wide-field imaging gives you a different perspective on the wonders of our own galaxy. One day I would like to explore wide field imaging, the process is the same as deep sky imaging using a telescope and computer controlled German equatorial mount, but replacing the telescope with a wide field camera lens. This is one of the goals I have, but I found out early on astrophotography has many learning curves and I went into it without any computer knowledge and my only camera was a Canon point and shoot.
At the time I had a neat solar telescope called a PST. One day I decided to hold the camera up to the eyepiece, called eyepiece projection and clicked the shutter. Doing that changed everything.
A precise German equatorial mount is critical in astrophotography, the only thing limiting longer exposures is your local light pollution and associated noise unless you are using a cooled CCD camera and filters. At my location, I can take long exposures up to about 3.5 minutes with a DSLR before light pollution and thermal noise pushes the histogram too far to the right. To mitigate the effects of light and noise the more light and dark frames added to the stack helps, but ideally shooting at a dark sky location is the best remedy.
My imaging/light train set up is an AT106mm Apochromatic triplet f/6 refractor telescope. Also known as an APO or well corrected to eliminate spherical and chromatic aberrations, a death blow to respectable deep sky imaging. The higher quality APOs consist of three glass elements, low ED with the main lens highly figured. A very good to exceptional triplet lens APO, depending on aperture, can cost you anywhere from $3,500 to $10,000. There were some exceptions to this and the telescope I bought retailed for less yet performed as well as other higher priced triplet refractors. The company no longer makes the telescope with the premium 3rd glass, replacing it with a less expensive and likely less performing version. The above addresses just the refractor telescope and doesn't include other imaging telescopes like reflectors, RCs or Richey-Chretiens, SCTs or Smith Cassegrains, and a host of other variations of the SCT platform that are available. All have their pros and cons in both features and price, in fact, my EdgeHD is one of those variations of the SCT. The difference between a refractor telescope and the others mentioned is the fact the incoming light passes through only lenses while with reflector based telescopes and SCT variants, incoming light is reflected off mirrors before reaching focus at the eyepiece.
My focal ratio is considered moderately fast and can be reduced further by a reducer or combination reducer/field flattener. Doing this enables shorter exposure times and a wider imaging field. The longer your exposures the more guiding errors will creep into the image, that's
unless you invest in a high-quality mount. Like I said, this is the most important investment you can ever make when assembling an astrophotography kit.
I would narrow the telescope mount field to those in the $7k to $13k range and that includes four or five manufacturers that qualify. This also depends greatly on the size and weight of your telescope, the heavier it is the more expensive the mount to handle it. For example, I also have another telescope that weighs about 45 lbs in imaging mode. It's called the Celestron 11" EdgeHD, it's big. I bought the AP mount as a reaction to the problems associated with the other mount and also because it has a higher payload capacity and a long history of world renown reputation for precision and quality. But then I was told I needed hip replacement and ankle surgery, which has put a major damper on the size and weight issue and my ability to continue the hobby. Depending on the outcome of rehabilitation, I may have to downsize to a more manageable setup and I'm looking at up to a year before that happens. Or, I can continue to procrastinate. You can find high quality equatorial mounts on the used market, those designed to carry lighter weight telescopes. They will run about $3.5K on the lower end, I'm referring to the Takahashi brand EM200 mount. They have an excellent reputation with a payload limit of around 35 lbs or so.
Add to all this a DSLR camera with a modified sensor or if you want to take a big leap, enter the dizzy world of choices when it comes to CCD imaging. There are two options here, one shot color or monochrome. Monochrome is the preferred instrument for advanced imagers with their higher SNR and sensitivity, but both deliver cooling whereas DSLR cameras don't. The price range for monochrome astrophotography cameras range from the low end of $2k to the moon, but a well set up unit with an internal or external filter wheel, off-axis guiding port, maybe hookups for liquid supplemental cooling and a quality sensor can cost you in the $4k to $6k range. There are plenty of them available for a lot more money, offering more techno features, but I'm talking about a range of high-quality choices at relatively affordable prices for the intermediate to advanced imager.
Notwithstanding the obligatory guide scope and guiding camera if you want to take long exposure images, you can even put a third camera on your set-up, this one is for figuring your polar alignment. There are other ways to configure polar alignments too. If you don't have an accurate polar alignment, you might as well forget about achieving quality guiding. However, for tripod mounted DSLRs using a fast wide-angle 14mm-24mm lens for pictures of the Milky Way, guiding assistance isn't needed because your 15 to 20 second exposures are short enough before field rotation sets in. There is an available formula to figure out maximum exposure times based on what lens you are using, but I find it easy enough to do some quick trial and error shots and check them in live view.
In short, my imaging train for the deep sky: telescope, light suppression filter, field flattener or reducer, DSLR. For tracking and guiding, a guide scope that sends corrections to a computer controlled German Equatorial Mount. For short exposures of the Milky Way: fast camera lens 14-24mm is preferred, DSLR, and tripod. A light suppression filter is probably a good idea. Astronomik is known for making clip-on filters that attach just in front of the mirror, inside the camera.
I hope this clarifies a few things Bob. Attached are two pics, one is the big 11" EdgeHD atop the AP900GTO mount I mentioned. The set-up stands about 7' tall. The other is my usual imaging set up with the AT106 APO refractor. Both telescopes have smaller telescopes mounted on top, these are guiding scopes. For scale, note the size of the Canon 60Da DSLR on the back of the bigger telescope.
Any kind of photography produces ADC readout or offset signal and bias frames are intended to capture the resulting noise. Some imagers contend taking bias frames have no appreciable gains, so they don't bother with them. I haven't personally compared my images with and without bias frames, I simply try and do what is recommended. However, taking a series of 50 to 100 bias frames is easy and some people don't know you have to take a lot of them to get any positive feedback. I have also created a library of bias frames and apply them as needed. You only have to take a series of bias frames a couple times a year, place them in a file so they are readily available anytime you want to use them. Depending on the quality of the image and duration, I may skip applying bias frames and flat frames and only apply darks. All of these elements are designed to reduce noise and uneven illumination. You can also create a library for flat frames and even dark frames too, but the darks must match the ISO, duration, and temperature of the lights, I've never explored making a dark frame library because of the many changes in temperatures from night to night, I just take them after each imaging session. However, you could set them aside and note the prevailing temps for each dark frame. The durations are already indicated and you could apply them to a future image session if they meet the same spec as your light frames. In short, aside from your light frames, corresponding darks, flats, bias and even flat darks have their own requirements.
Most of my sessions have been plagued with tracking and guiding issues and that is where I spend a lot of time trying to resolve. My mount is currently under repair at the factory and hopefully, they will fix it this time. Not achieving round stars in a deep sky image is a reject, that is why I haven't composed more photos. Even the ones I have processed, the stars are not what they should be, but I go through the motions for the sake of practice and learning anyway.
In response to your second question, I've only used a camera lens once to take any Milky Way shots, except for a rare shot of the moon, but camera lenses are used all the time in astrophotography, not just for the common Milky Way with foreground shots either. They are popular for wide field astrophotography and I've seen many beautiful compositions. Wide-field imaging gives you a different perspective on the wonders of our own galaxy. One day I would like to explore wide field imaging, the process is the same as deep sky imaging using a telescope and computer controlled German equatorial mount, but replacing the telescope with a wide field camera lens. This is one of the goals I have, but I found out early on astrophotography has many learning curves and I went into it without any computer knowledge and my only camera was a Canon point and shoot.
At the time I had a neat solar telescope called a PST. One day I decided to hold the camera up to the eyepiece, called eyepiece projection and clicked the shutter. Doing that changed everything.
A precise German equatorial mount is critical in astrophotography, the only thing limiting longer exposures is your local light pollution and associated noise unless you are using a cooled CCD camera and filters. At my location, I can take long exposures up to about 3.5 minutes with a DSLR before light pollution and thermal noise pushes the histogram too far to the right. To mitigate the effects of light and noise the more light and dark frames added to the stack helps, but ideally shooting at a dark sky location is the best remedy.
My imaging/light train set up is an AT106mm Apochromatic triplet f/6 refractor telescope. Also known as an APO or well corrected to eliminate spherical and chromatic aberrations, a death blow to respectable deep sky imaging. The higher quality APOs consist of three glass elements, low ED with the main lens highly figured. A very good to exceptional triplet lens APO, depending on aperture, can cost you anywhere from $3,500 to $10,000. There were some exceptions to this and the telescope I bought retailed for less yet performed as well as other higher priced triplet refractors. The company no longer makes the telescope with the premium 3rd glass, replacing it with a less expensive and likely less performing version. The above addresses just the refractor telescope and doesn't include other imaging telescopes like reflectors, RCs or Richey-Chretiens, SCTs or Smith Cassegrains, and a host of other variations of the SCT platform that are available. All have their pros and cons in both features and price, in fact, my EdgeHD is one of those variations of the SCT. The difference between a refractor telescope and the others mentioned is the fact the incoming light passes through only lenses while with reflector based telescopes and SCT variants, incoming light is reflected off mirrors before reaching focus at the eyepiece.
My focal ratio is considered moderately fast and can be reduced further by a reducer or combination reducer/field flattener. Doing this enables shorter exposure times and a wider imaging field. The longer your exposures the more guiding errors will creep into the image, that's
I would narrow the telescope mount field to those in the $7k to $13k range and that includes four or five manufacturers that qualify. This also depends greatly on the size and weight of your telescope, the heavier it is the more expensive the mount to handle it. For example, I also have another telescope that weighs about 45 lbs in imaging mode. It's called the Celestron 11" EdgeHD, it's big. I bought the AP mount as a reaction to the problems associated with the other mount and also because it has a higher payload capacity and a long history of world renown reputation for precision and quality. But then I was told I needed hip replacement and ankle surgery, which has put a major damper on the size and weight issue and my ability to continue the hobby. Depending on the outcome of rehabilitation, I may have to downsize to a more manageable setup and I'm looking at up to a year before that happens. Or, I can continue to procrastinate. You can find high quality equatorial mounts on the used market, those designed to carry lighter weight telescopes. They will run about $3.5K on the lower end, I'm referring to the Takahashi brand EM200 mount. They have an excellent reputation with a payload limit of around 35 lbs or so.
Add to all this a DSLR camera with a modified sensor or if you want to take a big leap, enter the dizzy world of choices when it comes to CCD imaging. There are two options here, one shot color or monochrome. Monochrome is the preferred instrument for advanced imagers with their higher SNR and sensitivity, but both deliver cooling whereas DSLR cameras don't. The price range for monochrome astrophotography cameras range from the low end of $2k to the moon, but a well set up unit with an internal or external filter wheel, off-axis guiding port, maybe hookups for liquid supplemental cooling and a quality sensor can cost you in the $4k to $6k range. There are plenty of them available for a lot more money, offering more techno features, but I'm talking about a range of high-quality choices at relatively affordable prices for the intermediate to advanced imager.
Notwithstanding the obligatory guide scope and guiding camera if you want to take long exposure images, you can even put a third camera on your set-up, this one is for figuring your polar alignment. There are other ways to configure polar alignments too. If you don't have an accurate polar alignment, you might as well forget about achieving quality guiding. However, for tripod mounted DSLRs using a fast wide-angle 14mm-24mm lens for pictures of the Milky Way, guiding assistance isn't needed because your 15 to 20 second exposures are short enough before field rotation sets in. There is an available formula to figure out maximum exposure times based on what lens you are using, but I find it easy enough to do some quick trial and error shots and check them in live view.
In short, my imaging train for the deep sky: telescope, light suppression filter, field flattener or reducer, DSLR. For tracking and guiding, a guide scope that sends corrections to a computer controlled German Equatorial Mount. For short exposures of the Milky Way: fast camera lens 14-24mm is preferred, DSLR, and tripod. A light suppression filter is probably a good idea. Astronomik is known for making clip-on filters that attach just in front of the mirror, inside the camera.
I hope this clarifies a few things Bob. Attached are two pics, one is the big 11" EdgeHD atop the AP900GTO mount I mentioned. The set-up stands about 7' tall. The other is my usual imaging set up with the AT106 APO refractor. Both telescopes have smaller telescopes mounted on top, these are guiding scopes. For scale, note the size of the Canon 60Da DSLR on the back of the bigger telescope.
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