Are coastal locations more likely to have better skies than inland ones?

[MKHACHFE]

Hi all,

After the wonderful success a few weeks ago with my first dark site trip, I am planning the next one with much excitement.

I have narrowed it down to a few locations in either Wales (inland) or the middle of nowhere north of Cornwall (coastal).
Both have pretty much the same SQM reading according to the light pollution map (21.8 supposedly) and both are about the same distance from our house. They are also similarly far from any large sources of city lights.

Clearly the coastal location will provide more open skies, especially to the south, where the milky way will be brightest, but I'm curious if any more seasoned members can tell me if the open sea/ocean skies would tend to be hazier than inland ones.

Thanks in advance and yes, I know to take the values on that map with a pinch of salty realism.

 

Cheers

[Ships and Stars]

Probably not a huge difference between them. It's down to many little factors, including elevation, wind and weather, amount of passing cars at night, amount of visible sky as you mention. Higher up is good, less atmosphere, but not if it's so windy the scope won't stay still.  Inland, the elevations we are talking about in the UK perhaps won't make a huge difference, but low areas can gather dew/fog easier when it settles in my experience.  As well all know, beaches can be very windy too, esp in winter. Having sand and salty air blowing around my gear is not too appealing. Coastal would be better in a protected spot or grassy area inland form the beach itself or up on a cliff or hill over the sea. On the upside, you should have a clear run of dark sky looking out to sea with near-zero light pollution.

Hills can create turbulence which affects seeing, coastal or island peaks can be smoother if a steady settled breeze is coming off the water without turbulence, but these things apply more to world-class sites like La Palma or Mauna Kea.

Older but excellent article on astronomical seeing by Merle http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1984ESOC...18....3W&defaultprint=YES&filetype=.pdf

I like to use Google Maps, then go to street view (if available) to get some sense of the area if I've not been. There might be a shop or farm within 500m or so with floodlights etc, you never know. Some farms have really powerful lights. Worse thing is to arrive somewhere after a long drive, and discover it's nothing like what the map suggested, even Google Earth. That's why I like streetview.

Personally, I would lean towards the Welsh site if at some altitude, but check wind conditions first. You'll still have clear views to the south if not blocked in by hills.

On the other hand, Cornwall is quite nice too! Again, check the weather and wind, SW England has that 'Cornish drizzle' that sets in quickly. 

Good luck!

Edited February 4, 2020 by Ships and Stars

[George Gearless]

I have access to a summerhouse on a small island. Not only is it very dark, since there are only about 100 local inhabitants and no public lightning. But I've often found that when people on the mainland complain about grey skies or even rain, it's (almost) clear skies over the island. There's propably a meteological explanation for this, although I don't know it. In fairness, if the whole region is covered in thick heavy clouds, then so are the skies over the islands. It's not like islands are perpetualy cloudfree (if they were, I'd quit my job and move there tomorrow  ). I just think they're more likely to have clear skies than mainland areas.

Island weather and costal weather are propably not the same. But then again neither is costal and inland weather. So it's an interesting issue to ponder when searching for a good site.

[bingevader]

We live not too far from the coast and the weather can be a bit unpredictable.

There's a reasonably sized town 6 miles away and the difference between the two can be astounding at times.

Yes, your coastal site should have much better uninterrupted views out to sea, but if that is to the North, it's not necessarily an advantage.

I'm not a meteorologist, but an on shore breeze in winter is likely to be warmer and wetter than the surrounding land.

We have the odd bit of sea mist or fog too that rolls in all of a sudden and puts a halt to any stargazing!

Put it this way, I wouldn't set off with out knowing what the weather was going to be like, but then I suppose that goes for the inland site too!

[joe aguiar]

It could be alot more dewy where dew caps wont do and powered dew control and all that hassle comes into effect

Also if u near oceans all that salt water may cause other issues

Not to mention that all that water vapor in air may make seeing not so good

Trading one for another isn't all good

Joejaguar 

Edited February 5, 2020 by joe aguiar

[Paul M]

I'm on a west facing coast so do have access to a pristine west horizon (other than the 15 trillion or so wind turbines scattered between us and the IOM, each with a red light on top). Not to mention the bright lights of Blackpool 6 miles to the south.

Our air is clean, if nothing else but it picks up a lot of moisture.  Even on not so windy days you can see the haze drifting inland, occasionally this cools into very dense sea fog. The humidity is usually there to some degree but if a wind is present it'll carry salt too. It covers windows and cars some distance inland. Not something you want on exposed optics! 

In general we get more cloud and rain than the east coast and certainly more than the south coast.

 

[Mick H]

As mentioned in the Anybody Playing Tonight thread.

Here in North Norfolk we can have brilliant skies, but we have mist which rolls in of the sea.

Even in height of summer when it's baking hot inland, when the sea mist rolls in it is very very cold.

[Hawksmoor]

I live close to the North Sea. Weather is often variable and affected by the tide. So clear skies are difficult to predict and often at odds with the met office. The one big issue I have is 'condensation'. With standard insulation jackets, camera lenses dew up after an hour, so I now use battery powered 'Dew-zappers' on all my camera lenses and telescope objective lenses. 

Hope helpful 

George in moist Lowestoft

[MKHACHFE]

2 hours ago, Hawksmoor said:

I live close to the North Sea. Weather is often variable and affected by the tide. So clear skies are difficult to predict and often at odds with the met office. The one big issue I have is 'condensation'. With standard insulation jackets, camera lenses dew up after an hour, so I now use battery powered 'Dew-zappers' on all my camera lenses and telescope objective lenses. 

Hope helpful 

George in moist Lowestoft

Sadly, I have recently become very well aquatinted with the dew problem. It is definitely a session killer and like you, I have also bought a usb powered heating strap which does work up to a point. I need a few more though. 

 

Cheers

[MKHACHFE]

5 hours ago, Paul M said:

I'm on a west facing coast so do have access to a pristine west horizon (other than the 15 trillion or so wind turbines scattered between us and the IOM, each with a red light on top). Not to mention the bright lights of Blackpool 6 miles to the south.

Our air is clean, if nothing else but it picks up a lot of moisture.  Even on not so windy days you can see the haze drifting inland, occasionally this cools into very dense sea fog. The humidity is usually there to some degree but if a wind is present it'll carry salt too. It covers windows and cars some distance inland. Not something you want on exposed optics! 

In general we get more cloud and rain than the east coast and certainly more than the south coast.

 

Thanks for the information. Much appreciated.

[MKHACHFE]

5 hours ago, joe aguiar said:

It could be alot more dewy where dew caps wont do and powered dew control and all that hassle comes into effect

Also if u near oceans all that salt water may cause other issues

Not to mention that all that water vapor in air may make seeing not so good

Trading one for another isn't all good

Joejaguar 

Well, that's really what I was asking. In your opinion, would dew be more common at coastal locations?

As for the salt water, I'm not concerned with that as I would only be there for an evening or two at the most.

 

Cheers

[joe aguiar]

1 hour ago, MKHACHFE said:

Well, that's really what I was asking. In your opinion, would dew be more common at coastal locations?

As for the salt water, I'm not concerned with that as I would only be there for an evening or two at the most.

 

Cheers

for sure 100%

salt water over time rusts alumunum or steep parts and over time coating too

joejaguar

Edited February 6, 2020 by joe aguiar

[MKHACHFE]

23 hours ago, joe aguiar said:

for sure 100%

salt water over time rusts alumunum or steep parts and over time coating too

joejaguar

I understand. Thanks for the reply.

[Phil Fargaze]

In the spring and autumn I take myself off to Suffolk to a dark site with a claim of SQM being 21.75 and located about 3.5 miles in from the coast of the North Sea. I have had occasions of dew and fog but at least I can go prepared for the dew. When the sea mist is about it can be patchy so I usually end up chasing gaps, but also with a bit of preparation I can be ready for this as well. For me, any disadvantage to being near the coast is offset by the convenience of a two hour straight forward drive up the A12 to get to the site. 

[Carbon Brush]

It is interesting to hear how various members make their plans to locate good dark sites and how to handle the dew problems.
There is some very good advice in the posts.

It is though a sad statement on the state of UK light pollution when many of us have to travel long distances to find a dark sky.

Phil's comment 'the convenience of a two hour straight run' sums it up for me.

A short run (20/30mins) to a dark site allows a trip out if it looks (at short notice) like it might be a good night.
But two hours each way. Then setup and pack away time. Not when you have to be up early for for work the next day.😪

David.

 

[Phil Fargaze]

When I do my two hour journey it is to camp out for at least two nights. I wouldn't fancy going too far on a working week either. I don't usually do short trips because they would not be beneficial enough. So I just have my twice yearly camping trip to look forward to which is timed for a New Moon and the weekend so I can never be sure what the weather will be up to.

 

Edited February 8, 2020 by Phil Fargaze

[scarp15]

That is also what I plan to do more of, to camp out for a night. This will enable a slightly longer journey (more than an hour each way), requires being flexible though around new moon times. Cannot add anything further to what has already been said concerning coastal observing. Often, I quite like to go onto higher open ground to maybe reduce the extent of condensation building up.

[alacant]

Hi. I think it depends on the wind/airflow direction. We're 10km inland in SE Spain. Westerlies -coming from the interior- are dry and provide good seeing. OTOH the coastal strip here is narrow and onshore easterlies play havoc with the seeing as the moist air hits the mountains a few km to our west. This often creates a haze.

My conclusion would be that if you have a choice, go with inland.

Cheers and HTH.

Edited February 8, 2020 by alacant

[ollypenrice]

On 05/02/2020 at 22:44, joe aguiar said:

 

Not to mention that all that water vapor in air may make seeing not so good

 

On the other hand it might make it better. Damian Peach has done some very famous high res. planetary imaging from Barbados, which he chose for its seeing rather than its transparency, which is not particularly good. Haze and good seeing often go hand in hand, just as do high high transparency and poor seeing. (Yet another astro-hassle!!)

Olly

Edited February 9, 2020 by ollypenrice

[CraigT82]

1 hour ago, ollypenrice said:

Damian Peach has done some very famous high res. planetary imaging from Barbados, which he chose for its seeing rather than its transparenc

Indeed... Barbados has great laminar atmospheric air flow, straight off the Atlantic.  The air flows undisturbed for thousand of miles before getting to the island which makes for lovely steady seeing.  

[Louis D]

The annual Winter Star Party (WSP) is held at Camp Jackson Sawyer on Scout Key in far south Florida, USA.  The viewing conditions are generally rated among the best anywhere.  The laminar air flow off the Gulf of Mexico helps immensely.