I wrote this article in anticipation of a workshop I will be doing with Astrotourism WA (Western Australia) group sometime this year. Having heard of them from friends in Australia, I feel it is a worthwhile efforts by the local communities to band together and give us information on where and how to enjoy the night skies of WA.
The Camera + on-camera Accessories
These days most cameras, including entry level ones will do the trick so long they have the following functions within the camera.
- There are differing views about MFT and astrophotography but I prefer to use a larger sensor, at the minimum APS-C.
- Full Manual Mode. This is the most basic requirement so even the entry-level DSLR/Mirrorless should be able to have. But this is just the first requirement.
- Second step is the ability to use BULB mode. This mode is to allow you to shoot longer than the 30 seconds. It may sound excessive especially when you heard about the 500 rule. More on that later.
- A wired remote trigger. While some may say using a timer is good enough, it is still not the most precise if you are planning to blend 2-3 images into one image.
I usually would love to shoot landscape with the night sky and hence do not really use a telephoto/zoom lens for my Astro shots. Hence I go primarily with ultra wide-angle lens. On top of wide-angle lens, having the widest aperture gave me more options while on in the field.
Using an f4 lens maybe cheaper but that would mean another 2 stops of more in terms of exposure time or increase of ISO both of which are not that helpful
- Tokina 11-16mm f2.8 for APS-C (equivalent to 17- 24mm Full Frame)
- Samyang/Rokinon 12mm f2.8 for APS-C (equivalent to 18mm Full Frame)
- 7Artisan 7.5mm fish-eye f2.8 for APS-C (equivalent to 12mm Full Frame). My review here
- Venus Optics Laowa 12mm f2.8 for all sensors (equivalent to 18mm Full Frame)
- Canon/Nikon/Sony/Fujifilm ultra-wide at f2.8 usually have no problems. Above are the cheaper alternatives.
If you are purchasing any of the lens you can check them out with this link
Please use code “WILZGEAR” to support my site
The 500 Rule
There is a basic rule called the “500” rule is to calculate the maximum exposure time you will need for the camera to use when using a particular lens without the starlight trails being recorded because the Earth is always rotating.
Below are some examples of the calculation based on say the Laowa 12mm f2.8 lens
- Full frame = 500 / Focal Length = 500/12 = 41 seconds
- Nikon/Fuji/Sony APS-C (1.5x crop factor) = 500/12/1.5 = 27 seconds
- Canon APS-C (1.6x crop factor) = 500/12/1.6 = 26 seconds
- Olympus/Panasonic Micro Four Thirds (2x crop factor) = 500/12/2 = 20 seconds
Simply put, the smaller the sensor, the short the exposure time and that will also mean needing an even wider ultra-wide angle lens.
The limitation of the 500 Rule
In night photography, especially very dark night sky elements, the longer the camera can expose the better it is. However, due to the fact that the earth moves as well, the amount of time the camera can expose is severely limited if you want to avoid light trails from the stars.
That means if you have had a full-frame camera, coupled with a fisheye lens of 7.5mm the maximum exposure you can go is (500/7.5=) 66 seconds or 1 minute. That is not a lot of time.
I would also want to use an ISO value in the low hundreds so as to avoid as little unwanted colour dots in my images as well. Yes, I can get the colours but sharpening the images later will result in more dots than I like.
The Star Tracker: Breaking the 500 Rule Limitations
I want to use low ISO and expose the camera for more than a minute or more, than I would need to use a Star tracker.
What the star tracker does is to track the star and ensuring the star stays in one place in the image. It does that by countering or moving in opposite direction of the earth’s rotation.
The advantages of having a star tracker:
- the star trail is kept to the minimum or none at all if the tracker is set up accurately
- with very little movement from the stars, that means my exposure time with the camera can be drastically increased, from 25 seconds to more than 2 minutes. My longest was around 5 minutes to avoid the sensor from overheating
- because I can do very long exposure right now, my sensor can be desensitised further using the low ISO values. That would mean I need not buy the more expensive full frame sensors too. On top of that, there is lesser ISO noise I need to edit away in editing.
Usually such star trackers are expensive and cumbersome but I chanced upon a firm called Move Shoot Move that produces value for money trackers without the bulk. It can support camera+lens of up to 3KG so Mirrorless with light fisheye or ulta-wide angle lens is not an issue.
You can buy the MSM Star Tracker with the link here
Do remember to use the Discount Code “SPIN” for a 5% discount!
Tripods + Tripod Heads
Most of the tripod heads are workable but I find ball head tripod heads are a bit tougher to control when you are trying to find the northern and southern points in the sky.
I highly recommend getting a 2-way Pan/Tilt tripod head. It allows TWO 360 rotation for the camera as well as for the whole head and camera. I am now using the Andoer VH-10R where I mount the tracker and then a ball head to the tracker for the camera.
Future Workshops in 2020
I will be working with Western Australia Astrotourism to visit their back country, or what they call Outback to gaze the night sky. As Western Australia’s capital city Perth is situated between the green oasis to the South and the desert landscape to the North and East, there is very little light pollution once you go to the outback.
The workshop is slated to be either in mid-June or mid-July. The workshop/gathering is mainly to organise a shooting session with all the enthusiasts/learners and if time permits, showing how I do my quick edits with Lightroom and Photoshop.
If you are interested to join me, you can follow me at https://www.facebook.com/WilzWorkz or email me at firstname.lastname@example.org so I can keep you informed.
About Wilson Wong
Founder of the 10500+ members Singapore Photography Interest Network photography group, avid gadget lover and budget wanderluster. He also writes for Techgoondu.com a tech website for the non-techies about the latest trends in personal tech. His wish is to help people get the right stuff and enjoy life without cutting off limbs to do so.