"Astronomy compels the soul to look upward, and leads us from this world to another."
- Plato
How it began:
I started out in astrophotography without a clue how far I might take it. From starting off with the moon, I attempted every night to get a shot better than the night before. The moon is by far one of the easiest objects up there to get a picture of as there are many different ways to capture it. This can range from a landscape shot with the moon in the frame to a high resolution picture showing many of the craters on the surface or to a close-up consisting of a tiny patch of the moon's surface. My preferences are the latter two as I always challenge myself to see the finest of details every night I do lunar imaging.
Likewise, when I started out in deep-sky imaging and learnt the importance of exposure time, I have since set myself a minimum goal exposure I would want to reach to reveal as much of a nebula or galaxy as I can. It helps me to improve the image when I have a set number of hours of exposure I want to reach so I don't capture less than what I see as ideal. Not only is it the total exposure time that I set goals for, but I do it for sub-exposure lengths too. The longer the sub-exposures are, the better, but good guiding is a must in this situation. Setting exposure goals also helps me get a rough estimate on when I should be finished imaging a certain object based upon how much I capture per night.
I enjoy all aspects of astrophotography although, each celestial object has its own challenges. For example, deep-sky requires lots of hours of exposure and perfect tracking while planetary needs low atmospheric turbulence. Processing the images has fewer technical issues but relies hugely on personal preference for the final appearance of the image such as the colour. However, taking pictures on a clear night is a great excuse to go lie down outside and look up for a few hours.
Here are two images taken with the Nexstar 5SE and IMX224 camera. The left image was my very first moon mosaic and the right image is a mosaic consisting of stacked images. Both were taken just less than 2 years apart. Click to zoom
Here is a comparison between two images of the Orion nebula from 2021. The left image was taken using 10 second sub exposures while the right was taken with 2 minute subs. You can see how longer subs pull out far more of the nebulosity.
A Brief Introduction to Astrophotography:
What is astrophotography:
Astrophotography is a very different type of photography. Rather than terrestrial things being imaged, the heavens above the Earth are photographed instead. There is something so compelling about astrophotography in the way you're able to capture a vast scenery out there in the universe. Whether this be a nebula who's light has taken thousands of years of travelling through space only to be recorded on a camera chip or capturing the reflected sunlight of our closest celestial neighbour - the moon. A picture captivates people's imagination, makes them wonder and to some, can be quite an emotional realisation just how insignificant our presence is among the grand scale of the cosmos.
Do you need a lot of patience?
Yes. Absolutely do you need a lot of patience with astrophotography. You need a tonne of patience when everything is going right because of the long exposures that are required and you need even more when things are not going to plan. I have lost many nights before due to a variety of problems and had to wait many weeks for the weather to clear up for a single clear night. Most problems can be blamed on the weather (British weather for that matter). Weather forecast says clear, my observations show it's clear, proceeds to set up telescope. Once set up and the first light is coming through, thick clouds blanket the sky. Even worse, cloudy nights for weeks and when there finally is a clear night, it's either too windy, or the guiding is misbehaving.
A clear night can very quickly turn cloudy seen here as I try to image the Veil nebula.
Exposure and Stacking:
I have mentioned exposure a few times already but it is a vital part to getting a good image of a faint object in space. Simply put, exposure is how long light (signal) is recorded by the camera sensor. The longer the exposure, the greater the signal. You may have seen image noise - the grainy pattern when you take a picture. What you are looking for is far more signal than noise and to get this, you need longer exposures - a higher signal-to-noise ratio (SNR). If I took six 10 minute sub-exposures, each image will be relatively noisy, but when stacked (combined together), the signal amplifies, the noise is less apparent and overall, the image is higher quality. This stacked image is then the equivalent of a 1 hour exposure. Sub-exposures must also be of a certain length to capture the signal in the first place. You couldn't take 3600 1-second exposures and expect the same result because the camera hasn't effectively picked up the signal.
Above is a single 5-minute exposure on the Horsehead nebula. The shape can be made out fairly easily but upon a closer look, there is a great amount of noise
Why telescopes are the coolest tool for exploration:
The idea of a telescope is very simple, to magnify far away objects and gather as much light as possible. There are different types of telescope used for different purposes but they all have something in common and that is looking back into the past. Basically, telescopes are the closest thing we have to time machines. When you look through a telescope at say, the Andromeda galaxy, you're looking back in time about 2.5 million years from your own home... Now isn't that cool or what! They can be used to study the formation of stars and solar systems. By looking back in time, telescopes can also tell us the age of the universe by looking at the furthest (therefore, oldest) galaxies. Much larger telescopes like Hubble can see back in time to the early universe where galaxies are billions of years old. But telescopes don't just operate using visible light; the Planck telescope has been used to map the Cosmic Microwave Background (CMB) which is light so red-shifted from so long ago that it has become microwaves. This telescope shows us the radiation given off shortly after the big bang. So yes, technically, telescopes are the closest we have to time machines.
Below is a stacked image consisting of 120 5-minute exposures (10 hours total). You can see how much smoother and stronger the signal is of the nebula.
Skywatcher Evostar 80ED on NEQ6 - my deep-sky imaging setup. More about my equipment on the 'Equipment' page.
Swapping over from the C8 to the 80ED for a night of galaxy imaging.