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Cape Verde astronomical seeing conditions? Impressions anyone?


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Hi all,

Doing a bit (well, a lot) of dreaming recently about truly exceptional quality dark-sky sites.

As in the absolute best observing locations on Planet Earth.

I know the Rocque de la Muchachos observatory on La Palma in the Canary Islands gets a silver medal, second only to Mauna Kea in Hawaii, for low humidity and cloud cover, stable laminar airflow off the ocean, low-ish light pollution and high elevation generally above the temperature inversion which tends to trap moisture and aerosol pollutants, etc.

Some of the western islands of Cape Verde seem like an almost equally brilliant location, but I can't find anything online about Cape Verde star-gazing/astronomy other than a few mentions here and some online adverts for hotel-run trips to darkish spots outside of the tourists areas at low elevations.

I am really interested in the more remote, non-touristy islands to the west and south which have several peaks in excess of 1000m, with one in particular reaching almost 3000m and Bortle 1 skies throughout large parts of the islands, probably a good nine hours of true nightly darkness throughout the year, and average temps at lower elevations between 23 and 27C year-round. Sounds terrible, doesn't it?

These non-touristy islands seen like very remote places with only a few tiny villages or clusters of small houses up on higher ground, possibly even without any visible 4x4 tracks on satellite imagery, but some of the more established roads (gravel tracks actually, from what I can tell) over the mountain passes must offer simply incredible seeing conditions.

Has any intrepid stargazer ventured up on any of the high ground on say Santo Antao or Fogo, with a telescope or even binos?

Is Cape Verde hampered by mist and clouds more than the Canary Islands? I seem to get that impression from what reports I've read, but rainfall is virtually zero most of the year. It's a very arid place from what I gather.

By the way, I have read the excellent Merle Walker article on high quality astronomical sites, a great resource for any fellow dark-sky dreamers. He mentions Cape Verde in a single sentence or table entry, but seems to discount it for reasons unknown. 

http://adsabs.harvard.edu/full/1984ESOC...18....3W

Cheers all.

 

 

Edited by Ships and Stars
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There must be a reason why none of the world's largest telescopes are situated on the Cape Verde islands. I couldn't guess why, but a great deal of "on the ground" work goes into selecting suitable sites. It is telling that the paper you cited shows only 16 observable nights in 1.6 months from Cape Verde (see page 10).

One benefit that Cape Verde has over the Canaries is being closer to the equator. That means the difference between day / night (and hence the number of dark hours each night) lessens the closer you get to 0° As does the seasonal variation.
And, of course, it makes more southern hemisphere targets easier (or possible) to view.

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I was on holiday a few years ago in Margarita in the Caribbean.  We took a trip to Los Roques archipelgo.  We were forced to have an overnight stay because the plane's don't fly at night as there is no electricity for the runway.   Though having thought about it there must be some electricity for the restaurants and homes there, but I think there was no street lighting.

I recall stepping out of the restaurant and looking out to sea (not sure which direction this was, but Orion was visible so I presume south).

My jaw nearly dropped off with the numbers of stars I could see and they looked like they were sticking out on stalks it was so clear.  I had no equipment with me and indeed had no idea I would be having this experience, and it's a shame my mum who was holidaying with me was taken ill and we had to dash back to our accommodation as I was unable to enjoy this for long.  

Carole 

Edited by carastro
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1 hour ago, pete_l said:

There must be a reason why none of the world's largest telescopes are situated on the Cape Verde islands. I couldn't guess why, but a great deal of "on the ground" work goes into selecting suitable sites. It is telling that the paper you cited shows only 16 observable nights in 1.6 months from Cape Verde (see page 10).

One benefit that Cape Verde has over the Canaries is being closer to the equator. That means the difference between day / night (and hence the number of dark hours each night) lessens the closer you get to 0° As does the seasonal variation.
And, of course, it makes more southern hemisphere targets easier (or possible) to view.

Hi Pete, Yes I was thinking that it was 'relatively' cloudier for some reason. 16 nights out of approximately 48 isn't brilliant for observable conditions, but perhaps that was just a seasonable thing or an unusual annual cycle. Having said that, I think the winds converge around Cape Verde, with a southern wind meeting a northerly perhaps causing a local weather front to hang in the area (not 100% on this). Although it didn't make the cut for the world's top telescopes, maybe it just missed the selection? It's a long way to go to find out I suppose, but I'd love to visit sometime. I'll keep a closer eye on the weather there over the next few months, might book an investigatory flight later in the year.

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1 hour ago, carastro said:

I was on holiday a few years ago in Margarita in the Caribbean.  We took a trip to Los Roques archipelgo.  We were forced to have an overnight stay because the plane's don't fly at night as there is no electricity for the runway.   Though having thought about it there must be some electricity for the restaurants and homes there, but I think there was no street lighting.

I recall stepping out of the restaurant and looking out to sea (not sure which direction this was, but Orion was visible so I presume south).

My jaw nearly dropped off with the numbers of stars I could see and they looked like they were sticking out on stalks it was so clear.  I had no equipment with me and indeed had no idea I would be having this experience, and it's a shame my mum who was holidaying with me was taken ill and we had to dash back to our accommodation as I was unable to enjoy this for long.  

Carole 

 

46 minutes ago, Nigella Bryant said:

I took a 3 day trip to tendaba Gambia when in Gambia, no light pollution a small campsite. Stars reflecting in the water. 

Both places sound wonderful! I've had some exceptionally clear nights in rural Scotland, but it was about -10C and I only seem to get those a few times each winter. My only tropical experience was Koh Tarutao near the Thai mainland, but there was a persistent haze. The best night I've had was SW Ireland in County Kerry. Milky Way was unbelievable. I'm still longing for a more tropical setting however!

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1 hour ago, clarkpm4242 said:

There is a rainy season, late summer and autumn.  https://www.holiday-weather.com/cape_verde/averages/

 

Actually it's very, very low precipitation, Cape Verde gets virtually no rain year-round except in those three months, mainly September (notably the inverse of the Canary Islands). Compared to La Palma, it's very much a desert! Actually it is sort of a desert, that's one thing that kind of puts me off the landscape there. The photos I've seen remind me of the Middle East, except a few small areas with some greenery. I think a lot of the drinking water or tap water comes from desalinisation plants or is imported.

Good website by the way for averages. I had forgotten about this one. Here's La Palma, Canary Islands for comparison on the rain:

https://www.holiday-weather.com/la_palma/averages/

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7 minutes ago, Ships and Stars said:

Here's La Palma, Canary Islands for comparison on the rain

Yes.  I've been to La Palma a dozen or so times...though half were primarily for mountain biking.  The observatories above the inversion layer will have  a vastly different profile.  The NE of La Palma is a rainforest!

I think a key factor is the consistent seeing i.e. laminar airflow from the NE Trade winds that the pro astronomers require for their work.  I expect that Cape Verde would be fantastic for ourselves.  La Palma is also feeling the encroachment of light pollution  :( 

Hope you can post pics from your future visit!

Cheers

Paul

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1 hour ago, clarkpm4242 said:

Yes.  I've been to La Palma a dozen or so times...though half were primarily for mountain biking.  The observatories above the inversion layer will have  a vastly different profile.  The NE of La Palma is a rainforest!

I think a key factor is the consistent seeing i.e. laminar airflow from the NE Trade winds that the pro astronomers require for their work.  I expect that Cape Verde would be fantastic for ourselves.  La Palma is also feeling the encroachment of light pollution  :( 

Hope you can post pics from your future visit!

Cheers

Paul

Thanks for the info Paul, yes I was thinking that while Cape Verde may not cut the mustard for world-leading scientific research compared to a handful of other top locations, for us mortals it can't be too bad, especially at the higher altitudes if they are accessible by car or 4x4. I should point out a lot of the higher ground on CV islands seems to be protected by the government, which is great, but may not in turn allows access by anything other than foot or pack animal. A US university set up a weather station on the top of Fogo island I think, and a CV army helicopter was used to lift the equipment up the volcanic cone (still active, by the way!). I will definitely do a write up if I ever make a trip down there with a nice little refractor or some good binos.

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I was in Boa Vista in April and go there (and Sal) fairly often.

I wouldn't recommend it as a PRISTINE place to see the stars.....its NOT BAD, but with it

being pretty windy there a lot of the time, theres often poor transparency with lots of sand

and dust in the air. 

I really need to take a small scope and mount there someday. We have stayed on the south side (at the Tourareg) 3 times

and it has a good clear view of the southern sky despite light pollution from the hotel. I was observing Omega Cent and the Southern cross

in April, and the fabulous area around there and it was a most memorable view.

Weather wise its usually good between October and May sort of time but there are cloudy days for sure.

June - Sept can be much more unsettled with rain and cloud. The can even get the odd tropical storm from time to time.

Temperature wise is nice : not too hot, not too cold. Usually in the day its around 24-28ºC with quite a tropical feel at times.

Its rarely over 30º though, but remember, its in the Atlantic, with its active weather and wind.

 

Its quite a good place for dust devils if you like spotting them ! 

Its a nice place to visit if you want to chill out and do nothing for 2 weeks. Probably why i like it !

Flying time from the UK is just under 6 hours.

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Hello Tubby Bear, Thanks for the information (sorry for my delay in replying!). I thought the desert-like conditions might play a detrimental role in transparency and it seems a fair bit windier than the Canary Islands looking at weather averages. On the light pollution map, Boa Vista outside of Sal Rei is very dark with little light pollution in comparison to Sal. Boa Vista appears to have Bortle 1 skies all along the eastern side (well for now anyway!).

Cape Verde sounds chilled out, I don't need a lot of things going on, sleepy is what I prefer most of the time, it sounds nice there. A trip to Santo Antao with a scope is my dream at the moment to check out conditions at the top of a mountain pass at night.

 

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To be honest, the wind was far worse in Fuerteventura when we holidayed there 3 or 4 years ago.

That windy at times there, you'd struggle to any observing there at all.

 

You are correct  : the Eastern side of Boa Vista, is very under developed : there is literally nothing there.

Access would the one issue : theres no roads, as you'd expect, only dirt tracks.

The Cape Verdes (certainly Sal) often remind me of the surface of Mars)

Lots of dust and dirt and sand for the wind to whip up. A bit like Mars !

 

 

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Yes the Google Earth views don't indicate much in the way of vegetation, just lots of dirt, sand and rocks! I'll venture down one of these days for a look. Still sounds intriguing and I can brush up on my ten words I know in Portuguese 😀. Thanks very much for the information!

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  • 3 years later...

Sorry to resurrect an old thread, but probably more logical than starting a new one. I was wondering if anyone had the chance to visit Fogo or Santo Antao? Most photos I see on google show haze and clouds, but not many taken 1'000m+ asl. Learnt on the Canaries, that close proximity to the mainland often means Calima = double-triple headache for the astronomer (head, eyes and the fine bits of your telescope mount/photo gear) hence asking about islands further West.

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I think the Saharas relatively close proximity means theres often lots of haze and dust in the atmosphere.

I've not been to Fogo or San Antao, only Sal and Boa Vista.

Fogo is interesting (it translates as 'fire' - Sal is 'salt' : its produced there, and Boa Vista is 'nice view' or 'good view')

Fire in that its actively volcanic, and there was a minor eruption there 5-10 years ago. The scenery and unspoilt volcanic landscapes look amazing. The volcano is over 9000 ft tall. I'd love to visit there someday.

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I know all the ins and outs of the Canaries and definitely see that Fuerte and Lanza is a no-go if there is any easterly in the wind. Never seen Calima on La Gomera and Palma. Could have been though, as we unfortunately spend less than a month on the islands each year. Very likely the same applies to the Cape Verde's.

Fogo is like a Northern Mauna Kea, seen many photos with tourists above the clouds (=inversion/cleaning layer!). However, getting there is not easy no roads to the rim of the Caldera.

Might be beating a dead horse here, I have no idea what seeing conditions are available in South Africa (twice the distance, but about the same cost to get down there). First class dark sky is available in SA too.

 

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