To start our journey, let's explore the basics of a DSLR camera.
Basics of the Basics
Focus - This is easy to understand. When the object is in focus, it appears sharp, else it's out of focus and blurred.
Aperture - This is how much light the camera allows, the larger the aperture, the more light that hits the camera sensor and hence, the brighter the image. It needs to be adjusted so that the right amount of light enters the camera. Too much light is over exposure and too little is under exposure.
Shutter Speed - Another lever that we can adjust. This is how long the shutter remains open. More the time it remains open, the slower the shutter speed, the more the light enters the camera, and the brighter the image.
ISO - In simple terms, think of this as sensitivity. High ISO means the camera becomes more light sensitive and images will look brighter.
All of the above can be adjusted in any DSLR camera in Manual mode.
DSLR cameras have an aperture, shutter speed, focal length, and ISO while telescopes have an aperture and a focal length. So in summary, the Aperture is the opening that allows light, focal length determines magnification, shutter speed is how long the aperture is open and ISO is how sensitive is the sensor to light.
Adjusting these is a must-do for any kind of night photography as explained below.
If you want to further deep dive on photography in general, then here are two of my ebooks to go deeper.
Astrophotography Basics
Dark nights and faint objects: The first thing that one needs to know about photographing the night sky is that nights are dark and objects we want to image are faint! So we need to keep the camera shutter open for a long time to capture faint objects in the night sky. Shutter speed therefore becomes the most crucial lever as the longer we keep the shutter open, the more light enters and hits the camera sensor. There is technically no limit to the time we can keep the camera shutter open. Note: This is where planetary and deep sky photography starts to differ since planets are brighter than deep sky objects but more on that later.
A word about ISO and Aperture: We have two other levers to control the amount of light that we can capture. But these have limitations and hence we mostly rely on shutter speed. Increasing ISO beyond a limit introduces camera noise ( Grainyness ) and we are limited by the highest aperture of the camera or telescope.
Earth's Rotation: Now keeping the shutter open for a certain amount of time seems like a good idea but beyond a point, we start to face a problem. This is because the earth is rotating, so after a few seconds, the camera is going to see something else as our target object moves out of view as the earth rotates. This is why we need tracking i.e. where the camera and telescope are following the object that we are trying to image. This is achieved through a device called the star tracker or an equatorial mount.
Camera - A DSLR camera ( with the kit lens removed ) or an Astro-dedicated camera is attached to the telescope. The telescope thus becomes the camera lens. The camera captures the images.
Telescope - Think of this as your camera lens. The lens is through which light passes and hits the sensor of the camera. The telescope has an aperture ( how much light can pass through or light gathering power and a focal length ( this is what gives you zoom or magnification). The bigger the aperture, the more the light-gathering power, and the larger the focal length, the more magnification you can get. There are many types of telescope and thats a topic for another article.
Mount - This is the device on which a telescope or a camera is mounted.
At its simplest, this is a tripod on which a DSLR camera is mounted.
I recommend a simple DSLR camera like the Canon EOS T7 with its included kit lens and a sturdy Tripod like the Manfrotto 190 Go
There are other cheaper tripods but if you plan to continue astro imaging with just a tripod and star tracker, don't go too cheap. Astrophotography needs a very steady tripod as slight shakes due to wind will ruin all the efforts.
The next level setup would be a DSLR camera ( which can be attached to a telescope ) mounted on a star tracker mounted on a tripod. This setup is limited by its weight-carrying capacity and also single-axis tracking.
I highly recommend the Star Adventurer 2i, I have had this and almost all my astrophotography have been with this. It is relatively very affordable and will serve you well. Of course do not expect automation as this is not a go to mount, so the positioning has to be done manually. Also it tracks only on one axis, hence its not as accurate as a dual axis equatorial go to mount.
If you do to invest a bit more on a 2 axis go to mount for ease of use and quicker photography sessions, then go for the Star Adventurer GTI. Again relatively affordable and has good reviews.
Finally, more advanced mounts are equatorial mounts which allow heavy equipment such as the telescope and the connected camera to move such that it can track the celestial object through slow but accurate movements along two axes.
I have the sturdy HEQ 5 from Skywatcher and it has served me very well so far. It has reduced my photography session times 3-4 times and once set up properly, its a breeze with pointing to the next object by go to functionality and shooting away from the comfort of ones room with wireless control using its app. Alternative cheaper version with lower weight carrying capacity is the HEQ EQM 35.
A good telescope to start with to mount on is the Skywatcher 72ED. This telescope again is relatively affordable and is wonderful and fully capable for astrophotography. Alternatively another great option is the SVBony SV 503
Armed with the technical basics, let's now enter the night sky and explore the fascinating jewels awaiting us.
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