Starting in Astrophotography
Hello again! Recently I've seen the same question repeated a lot of times in the Weekly Ask Anything Thread in this subreddit, the question is: What do I need to get started on Astrophotography?
Well, this might sound like an easy question with an easy response, but it is not. First of all, you need to decide which kind of Astrophotography you want to practice. There are two major categories:
So what do you need for DSO? Let's dive into this!
And what's a GoTo? GoTo is a hand controller/computer that makes calculations given the hour, date and position so you can find and aim, automatically, objects in the sky. The mount has also the ability to "follow" those objects, and that's why GEMs are so good. Any other mount won't work or will do but a notorious loss of efficiency.
One thing to take into account is the payload capacity of the mount. Each mount has its payload capacity but, when practicing DSO Astrophotography, that payload gets reduced by 40%. This is for avoiding vibrations and errors during the tracking. So, for instance, the EQ5-PRO has a payload capacity of 14 Kg, but the effective capacity for DSO is 8.40 Kg. This is important because the mount can condition your telescope and gear you can use.
The mount I recommend is the HEQ5-PRO from Skywatcher, which is the one I use. It has a really good tracking system, very precise and has a reasonable payload capacity.
Also, a big telescope requires a better mount because of the mount's payload capacity.
For DSO we need "fast" telescopes. We say a telescope is fast when the "f-number" or "f-ratio" has a low value. This value is specified by the manufacturer, and its expressed with this symbol: f/. The faster the telescope is, the faster it "captures" light from targets.
To calculate the f-number is easy, you only need to divide the focal length by the aperture of the scope. E.g.: A telescope with a focal length of 1500mm and aperture of 200mm is an f/7.5 telescope; a telescope of 750mm of focal length and an aperture of 150mm is an f/5 telescope.
Usually, an f/7.5 or less is fast enough for DSO.
Another thing to take into account is the maximum magnifications the telescope has. Exceed that maximum will lead us to obtain non-nitid images. Again, to calculate this value is very easy, you just need to multiply the aperture by 2 (This is not exactly true, but we will cover it later). So, following the same example as above, the first telescope has ~400x magnifications and the second has ~300x.
So, which telescope do I recommend? Well, there are two kinds of telescopes that work very well for beginners (and no-beginners too):
Reflectors are, in general, very fast telescopes with an f/5. They work really well, but there are things to consider.
First, reflectors need to be collimated at the beginning of each session. To collimate a reflector means to perfectly align the first mirror (the bottom one) with the secondary (the one close to the entry). An uncollimated reflector won't focus well.
To collimate a Newtonian is easy but, in the beginning, it can be a little bit tricky.
Second, is the comma error. Comma error is a deformation that suffers the image on the edges due to the concave form of the mirror. This is not a horrible problem and you can get rid of it using a comma corrector or just modifying or cropping the image on post-processing, but it's something to take into account.
Another thing to mention is, do you remember what I said above about the maximum magnification? On Newtonian telescopes, the multiplier is not 2, it's around 1.5 and 1.8. So, in terms of magnification, is not as efficient as a reflector.
Despite all this, reflectors are a really good alternative and work really well. A 750/150 reflector is enough to get started in my opinion.
Refractors are more manageable telescopes than reflectors. There are refractors for all f-numbers, but remember we want fast scopes, an f/10 won't be ideal. However, like everything, these telescopes have their cons.
First, unless you acquire an apochromatic refractor, you can suffer something called chromatic aberration. Chromatic aberration is when the colors reach a focus on different distances. Apochromatic telescopes solve this as well as other problems, but they are a little bit more expensive than normal achromatic reflectors.
Another thing you have to take care of when using a refractor is the Dew. Dew can wet your lenses and get into the tube. A wet lens means a session over. It is important to keep the lenses dry, otherwise, fungus can grow up there and ruin our telescope. The fungus can appear on reflector mirrors too, but they are much easier to clean. For avoiding the Dew there are many options, such as Dew Heaters or dew Shields. Dew Heaters are thermic tapes that warm up the tube a couple of degrees above the environment, avoiding this way the dew in the scope. Dew shields are like a plastic extension of the scope that avoids the dew to reach the lens.
In my opinion, refractors are more fragile than reflectors, but the results are better. Regarding details, Apochromatic refractors are the best.
There's a Skywatcher called Evostar 80ED which is a very good choice.
DSLRs are a good choice to get into the DSO, they are cheap, can be modded and are easy to use. Most common cameras in DSO are from Canon or Nikon. You don't need a lens for the camera, your telescope will be the lens. What we do is to attach the camera in where the eyepiece is attached, for that, we use something called T-ring and T-adaptor. The camera will do long time exposure shots, between 1 minute and 10, to capture the maximum possible light from the target.
Now, depending on the size of the sensor, you will have one or another magnification. Do you remember the formula to calculate the eyepiece magnification? For DSLRs works as well, but you have to use the diagonal size instead of the focal length of the eyepiece.
There's a software called Stellarium in where you can emulate your camera sensor, as well as your telescope and eyepiece, to check how the objects would look with your equipment.
If everything goes well, you can acquire a guiding solution, Bahtinov mask, Light Pollution Suppress Filter, Narrowband filter, dedicated cameras... But those are topics for another post.
And this is all you need to know to get started into DSO Astrophotography. Let's move to Planetary!
For planetary, the payload capacity gets not reduced. Of course, a motorized mount will do things easier, but I have seen people doing the movement by hand. This is possible due to the way to take "photos" in planetary, which take us to the camera.
But for getting good details, we have to talk about the telescope, so let's go!
So, knowing this, big reflectors, such as 200/1000 will work great for planetary. Also, big refractors will do the job, but usually, they are heavier than reflectors. But there's another kind of telescope, really good for planetary, that combines reflectors and refractors. Those are the Maksutov-Cassegrain.
Maksutov-Cassegrains use a corrector lens on the entry and a set of mirrors, one the bottom of the tube and another one just behind the corrector lens. This gives us super long focal lengths in a really reduced space.
As an instance, the Skywatcher Maksutov-Cassegrain 150 has 150 mm of aperture, which is traduced to ~300x magnifications, and 1800 mm of focal length. So using a normal planetary camera with around 6 mm of diagonal, you will have 1800/6 = 300x magnifications. And remember, from 180x magnifications, the details of the planets are revealed.
And this is all I know about Planetary Astrophotography. In my opinion, it is more easy and cheaper than DSO. But you also need to be more patient in planetary, for example, Mars enters into its opposition every 2 years more or less, which means that the best moment to shoot to Mars happens every 2 years. Also, DSO is really beautiful, but Planetary is too! To see the belts of Saturn with the Cassini Division or Jupiter with its storm and Galilean moons are awesome and beautiful too.
There's no category better than the other, both are beautiful and fascinating. Both imply a lot of learning and work, frustrations and success. The most important is you like what you do.
So, decide what you want to practice, buy your equipment and join the Astro-community!
Thanks for reading me, clear skies!
Well, this might sound like an easy question with an easy response, but it is not. First of all, you need to decide which kind of Astrophotography you want to practice. There are two major categories:
- Deep Sky Objects (DSO)
- Planetary
Deep Sky Object
Galaxies, Nebulae, Open Clusters... Everything that is outside of the Solar System is considered DSO. If you want to capture Andromeda Galaxy or the Orion's Nebula, this is your discipline. But also, take into account that this is, probably, the most expensive and frustrating branch of astrophotography.So what do you need for DSO? Let's dive into this!
Mount
This is, with no doubt, the most important part of the equipment, it's the brain of the equipment. There are a lot of mounts in the market, but you need one specific model, you need a German Equatorial Mount (GEM). Equatorial mounts have the ability to stay fixed pointing an object and move with the same movement as the sky "moves". But this movement must be soft and smooth, so it cannot be done by hand, so you need a mount with a GoTo and tracking system. |
| German Equatorial Mount |
And what's a GoTo? GoTo is a hand controller/computer that makes calculations given the hour, date and position so you can find and aim, automatically, objects in the sky. The mount has also the ability to "follow" those objects, and that's why GEMs are so good. Any other mount won't work or will do but a notorious loss of efficiency.
One thing to take into account is the payload capacity of the mount. Each mount has its payload capacity but, when practicing DSO Astrophotography, that payload gets reduced by 40%. This is for avoiding vibrations and errors during the tracking. So, for instance, the EQ5-PRO has a payload capacity of 14 Kg, but the effective capacity for DSO is 8.40 Kg. This is important because the mount can condition your telescope and gear you can use.
The mount I recommend is the HEQ5-PRO from Skywatcher, which is the one I use. It has a really good tracking system, very precise and has a reasonable payload capacity.
 |
| Skywatcher HEQ5-PRO |
Telescope
If the mount is the brain for DSO, the Telescope is the eyes. Acquiring a good (enough) telescope is crucial for this hobby. One might think that the biggest the telescope is, the better pictures you take. Well, this is not always true, for small DSOs a big telescope will work very well, but there are very big DSOs that won't fit in a big telescope. As an instance, the Andromeda Galaxy has 3 times the size of the full moon, the problem is we cannot see it at the naked eye. |
| Andromeda compared to the Moon |
Also, a big telescope requires a better mount because of the mount's payload capacity.
For DSO we need "fast" telescopes. We say a telescope is fast when the "f-number" or "f-ratio" has a low value. This value is specified by the manufacturer, and its expressed with this symbol: f/. The faster the telescope is, the faster it "captures" light from targets.
To calculate the f-number is easy, you only need to divide the focal length by the aperture of the scope. E.g.: A telescope with a focal length of 1500mm and aperture of 200mm is an f/7.5 telescope; a telescope of 750mm of focal length and an aperture of 150mm is an f/5 telescope.
f = focal_length / aperture
Usually, an f/7.5 or less is fast enough for DSO.
Another thing to take into account is the maximum magnifications the telescope has. Exceed that maximum will lead us to obtain non-nitid images. Again, to calculate this value is very easy, you just need to multiply the aperture by 2 (This is not exactly true, but we will cover it later). So, following the same example as above, the first telescope has ~400x magnifications and the second has ~300x.
Magnifications ~= 2 x aperture
This is important to know so we can select our camera properly, but we will talk about this later.
So, to calculate the magnifications that an eyepiece gives you, you only have to divide the focal length of your telescope by the focal length of the eyepiece.
Eyepiece_Mag = telescope_focal_length / eyepiece_focal_length
The same example again, given a 21mm eyepiece, with the first telescope it gives us ~71.5x magnifications and with the second ~35.7x.
So, which telescope do I recommend? Well, there are two kinds of telescopes that work very well for beginners (and no-beginners too):
- Reflectors (Newtonians)
- Refractors
Reflectors
This kind of telescope uses no lenses but a concave mirror on the bottom of the tube that reflects the image to another mirror that reflects the light right to the eyepiece/camera |
| Reflector telescope mechanism |
Reflectors are, in general, very fast telescopes with an f/5. They work really well, but there are things to consider.
First, reflectors need to be collimated at the beginning of each session. To collimate a reflector means to perfectly align the first mirror (the bottom one) with the secondary (the one close to the entry). An uncollimated reflector won't focus well.
 |
| Uncollimated reflector |
To collimate a Newtonian is easy but, in the beginning, it can be a little bit tricky.
Second, is the comma error. Comma error is a deformation that suffers the image on the edges due to the concave form of the mirror. This is not a horrible problem and you can get rid of it using a comma corrector or just modifying or cropping the image on post-processing, but it's something to take into account.
 | |
| Comma error |
Another thing to mention is, do you remember what I said above about the maximum magnification? On Newtonian telescopes, the multiplier is not 2, it's around 1.5 and 1.8. So, in terms of magnification, is not as efficient as a reflector.
Despite all this, reflectors are a really good alternative and work really well. A 750/150 reflector is enough to get started in my opinion.
Refractors
Refractors are the typical telescope that uses lenses to magnify the image. |
| Refractor telescope |
Refractors are more manageable telescopes than reflectors. There are refractors for all f-numbers, but remember we want fast scopes, an f/10 won't be ideal. However, like everything, these telescopes have their cons.
First, unless you acquire an apochromatic refractor, you can suffer something called chromatic aberration. Chromatic aberration is when the colors reach a focus on different distances. Apochromatic telescopes solve this as well as other problems, but they are a little bit more expensive than normal achromatic reflectors.
 |
| Chromatic aberration |
Another thing you have to take care of when using a refractor is the Dew. Dew can wet your lenses and get into the tube. A wet lens means a session over. It is important to keep the lenses dry, otherwise, fungus can grow up there and ruin our telescope. The fungus can appear on reflector mirrors too, but they are much easier to clean. For avoiding the Dew there are many options, such as Dew Heaters or dew Shields. Dew Heaters are thermic tapes that warm up the tube a couple of degrees above the environment, avoiding this way the dew in the scope. Dew shields are like a plastic extension of the scope that avoids the dew to reach the lens.
 |
| Dew heater - black tape |
 |
| Dew shield - Black extension |
In my opinion, refractors are more fragile than reflectors, but the results are better. Regarding details, Apochromatic refractors are the best.
There's a Skywatcher called Evostar 80ED which is a very good choice.
Camera
There's a whole world of cameras for astrophotography: CMOS Color, CMOS Monochrome, CCD Monochrome... But this is a "getting started" post, so the best way to get started on DSO Astrophotography is using a conventional DSLR.DSLRs are a good choice to get into the DSO, they are cheap, can be modded and are easy to use. Most common cameras in DSO are from Canon or Nikon. You don't need a lens for the camera, your telescope will be the lens. What we do is to attach the camera in where the eyepiece is attached, for that, we use something called T-ring and T-adaptor. The camera will do long time exposure shots, between 1 minute and 10, to capture the maximum possible light from the target.
 |
| Telescope - T-adaptor - T-ring - DSLR |
Now, depending on the size of the sensor, you will have one or another magnification. Do you remember the formula to calculate the eyepiece magnification? For DSLRs works as well, but you have to use the diagonal size instead of the focal length of the eyepiece.
DSLR_mag = telescope_focal_length / sensor_diagonal
There's a software called Stellarium in where you can emulate your camera sensor, as well as your telescope and eyepiece, to check how the objects would look with your equipment.
Ready to go
With these 3 things, you can start learning how to do DSO Astrophotography and trust me, you will have to learn a lot: how to control your equipment, software for taking frames, calibration frames, post-editing...If everything goes well, you can acquire a guiding solution, Bahtinov mask, Light Pollution Suppress Filter, Narrowband filter, dedicated cameras... But those are topics for another post.
DSO - The Cheap Way
There's another way to practice DSO in a more cheap way. for this you only will need:- A DSLR
- A good camera lens
- A portable star tracker
 |
| Star Adventurer - Skywatcher Star Tracker |
And this is all you need to know to get started into DSO Astrophotography. Let's move to Planetary!
Planetary
If DSO is everything outside the Solar System, Planetary is the complementary, i.e.: everything that's into the Solar System. Planets, comets, moon, even the sun! Unfortunately, I didn't practice this discipline, but I can tell you what I know.Mount
For planetary, the mount is not such relevant as in DSO. Here you can use different models of mount: equatorial, altazimuth, Dobsonian... |
| Different mounts |
For planetary, the payload capacity gets not reduced. Of course, a motorized mount will do things easier, but I have seen people doing the movement by hand. This is possible due to the way to take "photos" in planetary, which take us to the camera.
Camera
Do you remember in DSO the camera does long time exposures? Well, in planetary astrophotography photos are not taken, video is recorded. Solar System objects are bright enough so you don't need to do long exposures to obtain details, instead of that, you take video, which is a lot of images per second. For this reason, a good planetary camera with high FPS will be ideal. The way the planetary images are processed consists of recording between 1 and 3 minutes of video, convert the video into images, stack the images and select the 1000 better images. So, with a 24 FPS camera, in one minute we have 1440 images; with a 60 FPS one, we have 3600 images. The more FPS the camera has, the more images per second you will capture, the more detail you will get. |
| ZWO ASIO 120MC - Planetary Camera |
But for getting good details, we have to talk about the telescope, so let's go!
Telescope
Here we have to recover what we know about magnifications. The details of the planets are revealed with a 180x magnification or more. And what gives us the maximum magnification of a telescope? The aperture! So we want telescopes with big apertures. But this is not everything, if you remember, the magnifications given by an eyepiece or camera sensor are directly proportional to the focal length of the telescope, so we also want a telescope with long focal lengths!So, knowing this, big reflectors, such as 200/1000 will work great for planetary. Also, big refractors will do the job, but usually, they are heavier than reflectors. But there's another kind of telescope, really good for planetary, that combines reflectors and refractors. Those are the Maksutov-Cassegrain.
Maksutov-Cassegrains use a corrector lens on the entry and a set of mirrors, one the bottom of the tube and another one just behind the corrector lens. This gives us super long focal lengths in a really reduced space.
 |
| Maksutov-Cassegrain |
As an instance, the Skywatcher Maksutov-Cassegrain 150 has 150 mm of aperture, which is traduced to ~300x magnifications, and 1800 mm of focal length. So using a normal planetary camera with around 6 mm of diagonal, you will have 1800/6 = 300x magnifications. And remember, from 180x magnifications, the details of the planets are revealed.
Special cases
If you want to shot the Moon or the Sun you need special filters. Sun and Moon are, obviously, the more brightness objects in the sky. For Lunar you need a filter that reduces the amount of light in at least 13%. For the Sun is extremely dangerous to use the telescope without a filter. There are filters that reduce the light from the Sun in 90% - 99%. Also, there are special telescopes for Solar Photography.And this is all I know about Planetary Astrophotography. In my opinion, it is more easy and cheaper than DSO. But you also need to be more patient in planetary, for example, Mars enters into its opposition every 2 years more or less, which means that the best moment to shoot to Mars happens every 2 years. Also, DSO is really beautiful, but Planetary is too! To see the belts of Saturn with the Cassini Division or Jupiter with its storm and Galilean moons are awesome and beautiful too.
Conclusion
As you could see, DSO and Planetary are not similar at all, each one uses different techniques, equipment, and software (we didn't talk about this...). So, the most important question you have to ask yourself is: What kind of astrophotography do I want to practice?There's no category better than the other, both are beautiful and fascinating. Both imply a lot of learning and work, frustrations and success. The most important is you like what you do.
So, decide what you want to practice, buy your equipment and join the Astro-community!
Thanks for reading me, clear skies!
Videos of interest:
Astrobackyard beginners guide
Astrobackyard Starting astrophotography
Astrobackyard Beginner Astrophotography
Astrobackyard Beginner telescope
Astrobackyard Choosing Startracker
AstroFarsography Beginners guide
Links of interest:
- German Equatorial Mount: https://en.wikipedia.org/wiki/Equatorial_mount#German_equatorial_mount
- Skywatcher HEQ5-PRO: http://skywatcher.com/product/heq5-synscan/
- Reflector Telescope: https://en.wikipedia.org/wiki/Reflecting_telescope
- Skywatcher 150/750: http://skywatcher.com/product/bkp-150-ds/
- Refractor Telescope: https://en.wikipedia.org/wiki/Refracting_telescope
- Skywatcher Evostar 80ED: http://skywatcher.com/product/bk-80ed-otaw/
- Skywatcher Skyadventurer: http://skywatcher.com/product/star-adventurer/
- ZWO ASI 120MC Planetary Camera: https://astronomy-imaging-camera.com/product/asi120mc-s
- Skywatcher 200/1000: http://skywatcher.com/product/bkp-p200-ds/
- Skywatcher Maksutov-Cassegrain 150: http://skywatcher.com/product/bk-mak150-otaw/
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