Picking a Great Spot for Observing
I’ve commented before that the start of summer is a pretty rubbish time for me to rekindle my old love of astronomy.
This was forcefully proved to me again this week when trying to observe the stunning conjunction of Jupiter and Venus.
At 11pm it was still only dusky; I could see the moon but still not a solitary star. I walked around my house to try and get a good view of the west, knowing that Venus should be the first ‘star’ I would spot.
What that little exercise revealed was…
… how little of the sky I could see from my own home!
I’d never considered it before, but a combination of neighbours’ houses, trees and fences means I can probably only see about 50% of the observable sky from my garden!
That set me thinking: where the heck am I going to observe the night sky from once the darkness lasts more than four hours long again?
Using a little bit of research, what follows is the list of considerations we amateurs need to have when selecting an observing location:
1. Dark Skies
Let’s start with the obvious: it’s going to be much more rewarding astronomy if it’s done in a dark sky location!
Light pollution comes from street lights, factories, houses and roads – so find a spot as far from all of those as is reasonable. This is most likely to be many miles away from the hazy glow of a town or city.
To help find the nearest dark sky to you, use this ‘blue marble’ light pollution map to get a sense of how dark or light polluted your neighbourhood is.
As an aside, our eyes take 20 minutes to fully adjust to be the most sensitive they can in the dark – that time is something to factor in to getting the best from an observing session.
2. Easy Access
I’m going to have equipment to take with me, so regardless of whether I walk from my back door (preferable) or have to drive and then walk from my parking spot to my observation location, I want to make sure that it’s not too hard.
Thinking about how that equipment is all going to be carried (I’ll be returning to equipment for an observing session in my next post) I am going to make sure to do a dry run in daylight.
Why would I do that?
Well, I think I’d like to understand how I’m going to pack it all around my person, how much that weighs and how hard or easy it is to carry.
Then, for the route itself, I want to know how easy the trail from the road to the site will be to follow, and the quality of the path itself – is it wide and straight with good ground, or narrow, bendy and uneven – if it’s the latter, darkness will only make it more difficult!
As I write, it seems to me that a good plan would be to get to the observing site at dusk as I get used to setting up the equipment… even though the walk back will be in the dark.
3. Great Night Sky Views
I want to be able to see a lot more of the sky than I can from my house.
I’m thinking flat ground and open vistas from horizon to horizon, i.e. a 360 degree unobstructed view of the sky from zenith to ground.
If I can’t achieve this perfect position, then my night of observing may need a bit more planning: the last thing I want to do is turn up my preferred location to find the view of the planet I desperately wanted to see is blocked by a hill a mile away.
4. The Moon
Or, more specifically, the full moon.
Unless you are planning to study it, the full moon definitely can fall under the heading of ‘light pollution’.
I am going to be careful to check my moon phase charts before setting off to try and glimpse some faint, deep sky object.
Turning up to the site, getting set up and my eyes adjusted and peering into the lens… just as a bright, full moon leaps over the horizon is unlikely to make for a happy amateur astronomer.
What’s the impact of the full moon on observing the night sky?
Well, I couldn’t find any properly scientific numbers, but budding experts put the number visible stars in a dark location under a full moon at between a quarter and a half of what they would be with no moon in the sky!
5. Ground Quality
Simple this one – do not get to your planned location off a map to find that it is uneven or boggy.
You’ll no doubt have read as much as I have that setting up a delicate instrument like a telescope or camera needs a solid mount, but that is as much use (I suspect) as a chocolate barbecue if you’re then forced to stand it on marshy ground!
A couple of other points to watch out for: if you’ve found a field that is used for livestock, you probably don’t want to run the risk of setting foot (or telescope) in the middle of a cow poo in the dark…
… hey, also think: if you have found cow muck (or sheep, bison or goat, for that matter) when carrying out your recon, you should probably consider the risk of turning up there again ‘for real’ only to find your field full of cows!
As above, my plan is to do my homework in the daylight.
Find a suitable location, walk there, set up… and discover at that point if it feels like a suitable place to spend time astronomising (which is definitely a word).
6. Who’s Land is it?
Make sure that the spot you pick is either:
- Public land which you have the right to be on
- Private (but dare I say it) remote and barren (please don’t damage a farmer’s crops) enough that you are unlikely to be challenged for using it in the middle of the night
- Private, but you have the permission of the land owner to use it
I don’t think it’s any more complex than that, really.
7. Nighttime Weather Conditions
The astronomer’s most fickle friend or foe has to be the weather.
Cloud cover is the big one, obviously, so be glued to an accurate forecast in the hours leading up to your planned observations.
Wind is another issue – though maybe less obvious than cloud – but getting great views of the stars is made significantly more challenging when you and your equipment are being buffeted by the wind.
Finally, air quality plays its part in the details you’ll be able to observe.
Those who have many, many years more experience than me at this recommend high pressure and colder air mass above warmer ground provide the most clear and still air conditions.
Weather fronts, low pressure and high humidity are all air-disruptive and so will degrade the clarity of your observations.
8. Observing at Altitude
There is another element that you might be fortunate enough to bring into play for your air quality, and that is altitude.
As a rule, the higher you go the thinner the air, which equals clearer viewing conditions.
This is not a choice that I have open to me in the middle of England, but if you can find a spot somewhere between 5,000 and 8,000 feet above sea level, you are going to have significantly better quality air than those of us lower down.
9. Be Safe!
I’ve covered a lot already that could fall under being safe, such as the quality of the route to and from your site and whether there are any animals that might fancy haring you are nearby.
But, specifically here, I’m thinking about the quality of your telephone signal in case of emergencies.
I’ve said “get remote” because that means less light pollution, but it probably also means a rubbish phone signal.
If that’s the case, let someone who cares about you know where you are going and when you expect to be back… better safe than sorry!
When the night sky returns, I want to be ready to make good use of it.
So, site selection and preparation is key for me at the moment.
If you’re going through the same process, think about the fixed elements of where you’ll observe – such as access and visibilty, as well as the variable, such as the weather and moon.
If you already have a special place for observing (that’s not a custom-built telescope shed in your back yard which will make the rest of us jealous) then please share with us the things that make it your perfect site.
For a bit of inspiration, check out these best places to observe the night sky from… which include the lovely Cherry Springs State Park, shown in the picture below.
Next time, I’m going to share what I’ve thought about in terms of equipment needed for that first observing session
(Since writing this post, I have discovered that I shouldn’t beat myself up too much: by the time it was dark enough for me to have seen the conjunction here in the UK, the pair were so close the horizon I’d have needed to be in the middle of a field to see them!)