Guinea Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Guinea Observing Site clear sky chart from 2005-11-06 to 2026-10-14.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	13% 6% 2 6% 4 4 4 4 6% 8% 43%	148623
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 44%	143107
Transparency	Day	38% 4 12% 23% 18% 4	152228
	Night	39% 4 10% 23% 19% 5%	147571
Seeing	Day	19% 11% 26% 25% 14% 5%	17681
	Night	17% 10% 27% 31% 13% 2	27445

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	15% 6% 2 5% 3 3 4 3 4 5% 50%	5258
	11th to 20th	Day	13% 6% 2 4 3 2 3 2 4 4 56%	5280
	21st to end	Day	15% 7% 2 7% 4 4 4 3 4 5% 46%	5780
February	1st to 10th	Day	12% 8% 2 6% 5% 5% 5% 4 6% 7% 42%	1890
	11th to 20th	Day	22% 7% 1 4 4 3 3 4 4 6% 42%	1865
	21st to end	Day	19% 7% 2 6% 4 5% 4 3 5% 6% 37%	1803
March	1st to 10th	Day	17% 6% 2 7% 4 4 5% 4 5% 6% 39%	5045
	11th to 20th	Day	11% 5% 2 5% 3 3 4 3 5% 6% 52%	5090
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 5% 6% 42%	5586
April	1st to 10th	Day	10% 5% 2 5% 4 4 4 4 5% 7% 51%	2488
	11th to 20th	Day	12% 5% 2 5% 4 4 3 3 5% 7% 50%	2494
	21st to end	Day	16% 6% 3 6% 4 4 3 3 5% 8% 43%	2520
May	1st to 10th	Day	14% 6% 2 6% 4 5% 5% 5% 6% 9% 39%	7557
	11th to 20th	Day	17% 6% 2 5% 4 4 5% 4 6% 8% 39%	7626
	21st to end	Day	19% 6% 2 6% 4 4 4 4 5% 7% 40%	8745
June	1st to 10th	Day	10% 4 2 5% 4 5% 5% 4 7% 11% 44%	2940
	11th to 20th	Day	10% 4 1 5% 5% 5% 5% 5% 6% 10% 43%	2940
	21st to end	Day	8% 4 2 6% 4 5% 5% 5% 7% 11% 43%	2940
July	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 5% 7% 12% 42%	7784
	11th to 20th	Day	11% 6% 2 6% 5% 6% 6% 5% 9% 13% 30%	7680
	21st to end	Day	10% 6% 2 6% 5% 6% 5% 5% 7% 10% 37%	8340
August	1st to 10th	Day	14% 7% 3 7% 5% 5% 6% 5% 8% 12% 28%	6014
	11th to 20th	Day	8% 5% 2 7% 5% 5% 6% 6% 9% 11% 35%	5764
	21st to end	Day	8% 4 2 5% 4 4 5% 4 7% 10% 47%	6080
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 4 7% 49%	2520
	11th to 20th	Day	13% 6% 2 6% 4 4 3 4 5% 7% 45%	2455
	21st to end	Day	22% 6% 3 7% 4 4 4 4 5% 6% 36%	2225
October	1st to 10th	Day	16% 5% 2 5% 4 4 3 2 4 5% 50%	2100
	11th to 20th	Day	16% 4 1 4 2 3 3 3 4 6% 53%	2030
	21st to end	Day	13% 5% 2 5% 3 2 4 3 4 6% 55%	2200
November	1st to 10th	Day	12% 4 1 5% 3 3 2 4 4 6% 55%	2057
	11th to 20th	Day	15% 6% 2 5% 3 4 3 2 5% 6% 50%	1926
	21st to end	Day	14% 5% 2 5% 3 3 3 3 5% 6% 52%	1680
December	1st to 10th	Day	12% 5% 2 5% 4 3 4 4 5% 5% 50%	2680
	11th to 20th	Day	19% 6% 2 5% 3 3 3 2 4 6% 47%	3070
	21st to end	Day	16% 6% 2 6% 4 4 4 4 5% 7% 43%	4171
January	1st to 10th	Night	12% 6% 2 5% 3 4 4 3 4 6% 52%	7635
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 3 4 57%	7680
	21st to end	Night	16% 6% 2 5% 3 3 3 3 5% 6% 50%	8401
February	1st to 10th	Night	14% 7% 2 5% 4 4 4 3 5% 7% 44%	2730
	11th to 20th	Night	20% 7% 2 5% 4 3 3 3 4 6% 42%	2639
	21st to end	Night	15% 7% 2 5% 4 4 4 3 5% 6% 45%	2000
March	1st to 10th	Night	16% 5% 2 5% 4 4 4 3 5% 6% 46%	5028
	11th to 20th	Night	12% 4 2 4 3 2 3 3 5% 8% 54%	5090
	21st to end	Night	13% 6% 2 6% 4 4 3 4 5% 6% 47%	5588
April	1st to 10th	Night	14% 6% 2 6% 3 3 4 3 5% 7% 45%	2130
	11th to 20th	Night	11% 5% 2 5% 4 3 4 4 5% 8% 50%	2075
	21st to end	Night	14% 7% 2 4 4 4 4 4 5% 7% 47%	2100
May	1st to 10th	Night	13% 7% 2 8% 5% 5% 5% 4 6% 8% 37%	5339
	11th to 20th	Night	17% 6% 3 5% 4 4 5% 3 5% 7% 40%	5234
	21st to end	Night	21% 7% 2 6% 4 4 4 3 5% 8% 36%	5405
June	1st to 10th	Night	10% 5% 2 5% 4 5% 5% 4 7% 9% 44%	1680
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 3 8% 10% 41%	1680
	21st to end	Night	8% 5% 2 5% 4 5% 5% 4 7% 11% 44%	1680
July	1st to 10th	Night	10% 6% 2 7% 5% 4 6% 5% 7% 10% 37%	5155
	11th to 20th	Night	13% 8% 3 8% 6% 6% 7% 5% 7% 9% 27%	5277
	21st to end	Night	12% 7% 3 9% 6% 6% 6% 5% 7% 8% 31%	5736
August	1st to 10th	Night	16% 8% 3 7% 5% 4 5% 5% 8% 11% 28%	4135
	11th to 20th	Night	10% 6% 3 8% 5% 5% 6% 5% 8% 10% 34%	4234
	21st to end	Night	9% 6% 2 7% 5% 4 5% 4 6% 9% 42%	5045
September	1st to 10th	Night	12% 5% 2 5% 4 4 3 4 5% 7% 48%	2100
	11th to 20th	Night	13% 5% 2 6% 4 4 4 4 5% 6% 46%	2161
	21st to end	Night	24% 8% 3 6% 4 4 5% 3 4 6% 35%	2394
October	1st to 10th	Night	16% 6% 2 6% 4 4 3 3 4 5% 47%	2520
	11th to 20th	Night	16% 5% 2 4 3 4 3 3 5% 5% 50%	2437
	21st to end	Night	13% 5% 2 5% 3 3 3 3 4 6% 53%	2640
November	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 4 6% 52%	2461
	11th to 20th	Night	14% 6% 2 4 3 4 3 3 5% 6% 51%	2684
	21st to end	Night	13% 4 2 4 3 3 4 3 6% 6% 51%	2940
December	1st to 10th	Night	10% 6% 2 4 3 3 4 3 5% 5% 54%	4720
	11th to 20th	Night	20% 8% 2 6% 4 4 4 3 4 5% 41%	5345
	21st to end	Night	15% 7% 2 5% 3 4 4 3 6% 7% 44%	7009

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	38% 2 8% 24% 22% 7%	5259
	11th to 20th	Day	34% 2 4 18% 29% 14%	5280
	21st to end	Day	42% 2 5% 28% 18% 4	5780
February	1st to 10th	Day	42% 3 9% 26% 16% 4	1890
	11th to 20th	Day	44% 3 5% 22% 21% 5%	1874
	21st to end	Day	48% 4 10% 16% 18% 6%	1803
March	1st to 10th	Day	45% 3 8% 19% 16% 9%	5045
	11th to 20th	Day	33% 2 8% 22% 25% 10%	5090
	21st to end	Day	44% 2 10% 19% 18% 6%	5586
April	1st to 10th	Day	33% 3 11% 23% 21% 8%	2488
	11th to 20th	Day	34% 2 11% 25% 21% 6%	2494
	21st to end	Day	41% 3 11% 25% 16% 4	2520
May	1st to 10th	Day	42% 5% 13% 23% 15% 1	7591
	11th to 20th	Day	44% 4 11% 24% 17% 1	7630
	21st to end	Day	44% 4 13% 19% 17% 3	8760
June	1st to 10th	Day	34% 5% 16% 27% 17% 1	2940
	11th to 20th	Day	35% 6% 17% 24% 16% 1	2940
	21st to end	Day	33% 6% 17% 27% 15% 2	2940
July	1st to 10th	Day	34% 8% 21% 23% 12% 3	7719
	11th to 20th	Day	41% 9% 20% 20% 8% 1	7611
	21st to end	Day	40% 8% 13% 21% 17%	8156
August	1st to 10th	Day	47% 8% 21% 19% 4	6001
	11th to 20th	Day	37% 9% 22% 22% 9% 1	5803
	21st to end	Day	30% 6% 19% 27% 17% 1	6080
September	1st to 10th	Day	36% 4 14% 20% 23% 4	2520
	11th to 20th	Day	38% 4 9% 26% 20% 3	2455
	21st to end	Day	48% 4 9% 19% 16% 4	2225
October	1st to 10th	Day	35% 2 7% 20% 30% 6%	3360
	11th to 20th	Day	25% 2 5% 23% 31% 14%	3270
	21st to end	Day	21% 3 10% 28% 26% 13%	3538
November	1st to 10th	Day	31% 2 8% 26% 27% 5%	2057
	11th to 20th	Day	36% 2 9% 23% 22% 8%	1926
	21st to end	Day	35% 3 8% 24% 25% 5%	1680
December	1st to 10th	Day	35% 3 8% 26% 19% 8%	2680
	11th to 20th	Day	40% 2 11% 24% 18% 5%	3066
	21st to end	Day	42% 3 11% 26% 17% 1	4171
January	1st to 10th	Night	35% 2 9% 22% 22% 9%	7636
	11th to 20th	Night	33% 2 4 20% 30% 11%	7680
	21st to end	Night	38% 1 5% 28% 20% 6%	8401
February	1st to 10th	Night	40% 2 11% 25% 19% 3	2730
	11th to 20th	Night	44% 2 7% 20% 20% 7%	2641
	21st to end	Night	41% 3 7% 23% 19% 7%	2000
March	1st to 10th	Night	40% 2 6% 22% 21% 9%	5028
	11th to 20th	Night	30% 3 7% 19% 29% 12%	5090
	21st to end	Night	38% 3 9% 23% 21% 6%	5588
April	1st to 10th	Night	39% 3 11% 18% 22% 6%	2130
	11th to 20th	Night	33% 3 11% 25% 22% 6%	2075
	21st to end	Night	38% 4 11% 25% 18% 5%	2100
May	1st to 10th	Night	44% 5% 14% 23% 11% 2	5366
	11th to 20th	Night	44% 4 11% 26% 14% 1	5235
	21st to end	Night	48% 4 12% 20% 14% 2	5412
June	1st to 10th	Night	36% 5% 14% 26% 18% 1	1680
	11th to 20th	Night	37% 5% 19% 23% 15% 2	1680
	21st to end	Night	34% 6% 14% 24% 19% 3	1680
July	1st to 10th	Night	41% 9% 17% 21% 11% 2	5112
	11th to 20th	Night	50% 10% 15% 16% 7% 1	5226
	21st to end	Night	49% 8% 12% 17% 14%	5606
August	1st to 10th	Night	49% 9% 17% 19% 5%	4124
	11th to 20th	Night	41% 9% 19% 23% 8%	4261
	21st to end	Night	38% 6% 14% 28% 13% 2	5045
September	1st to 10th	Night	36% 5% 13% 22% 18% 6%	2100
	11th to 20th	Night	38% 5% 9% 23% 22% 2	2161
	21st to end	Night	52% 4 9% 17% 15% 4	2394
October	1st to 10th	Night	40% 4 9% 19% 24% 5%	4040
	11th to 20th	Night	26% 3 6% 22% 31% 12%	3936
	21st to end	Night	23% 2 5% 31% 27% 13%	4252
November	1st to 10th	Night	35% 3 8% 22% 27% 5%	2461
	11th to 20th	Night	36% 2 7% 21% 24% 9%	2684
	21st to end	Night	34% 2 8% 26% 24% 6%	2940
December	1st to 10th	Night	32% 2 7% 28% 25% 5%	4720
	11th to 20th	Night	46% 3 9% 18% 16% 7%	5348
	21st to end	Night	40% 2 10% 28% 17% 2	7009

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	31% 24% 26% 13% 6% 1	330
	11th to 20th	Day	29% 26% 33% 10% 2	330
	21st to end	Day	27% 23% 37% 10% 3	363
February	1st to 10th	Day	24% 25% 36% 13% 2	330
	11th to 20th	Day	39% 23% 27% 9% 2	352
	21st to end	Day	30% 16% 33% 17% 4	446
March	1st to 10th	Day	24% 19% 32% 18% 6%	540
	11th to 20th	Day	24% 20% 30% 20% 5% 1	540
	21st to end	Day	24% 19% 37% 15% 4 1	594
April	1st to 10th	Day	22% 18% 32% 19% 8% 1	540
	11th to 20th	Day	20% 14% 35% 20% 9% 3	532
	21st to end	Day	22% 11% 34% 22% 8% 2	540
May	1st to 10th	Day	23% 13% 34% 19% 8% 2	543
	11th to 20th	Day	23% 6% 29% 25% 15% 2	567
	21st to end	Day	22% 6% 21% 28% 18% 5%	617
June	1st to 10th	Day	9% 6% 29% 30% 20% 6%	570
	11th to 20th	Day	11% 6% 25% 34% 16% 9%	570
	21st to end	Day	11% 5% 23% 33% 22% 7%	570
July	1st to 10th	Day	12% 1 15% 34% 26% 12%	565
	11th to 20th	Day	7% 3 15% 35% 29% 13%	564
	21st to end	Day	10% 3 21% 30% 26% 10%	620
August	1st to 10th	Day	16% 3 20% 28% 25% 9%	566
	11th to 20th	Day	12% 1 17% 34% 25% 11%	559
	21st to end	Day	10% 2 20% 30% 22% 15%	627
September	1st to 10th	Day	14% 5% 17% 29% 19% 15%	570
	11th to 20th	Day	15% 4 16% 31% 22% 12%	570
	21st to end	Day	28% 7% 22% 27% 12% 4	570
October	1st to 10th	Day	23% 4 20% 28% 17% 8%	570
	11th to 20th	Day	18% 11% 23% 27% 18% 3	542
	21st to end	Day	17% 13% 30% 26% 10% 3	583
November	1st to 10th	Day	16% 10% 30% 28% 12% 4	535
	11th to 20th	Day	20% 15% 30% 24% 11% 1	434
	21st to end	Day	23% 20% 27% 20% 7% 3	220
December	1st to 10th	Day	23% 17% 38% 17% 4 1	220
	11th to 20th	Day	28% 13% 29% 24% 5% 1	220
	21st to end	Day	29% 14% 31% 18% 8% 1	272
January	1st to 10th	Night	20% 19% 35% 24% 2	840
	11th to 20th	Night	20% 19% 32% 25% 4	840
	21st to end	Night	21% 16% 38% 23% 2	924
February	1st to 10th	Night	18% 16% 37% 24% 3	840
	11th to 20th	Night	26% 18% 37% 17% 1	823
	21st to end	Night	23% 15% 35% 24% 2	692
March	1st to 10th	Night	20% 16% 34% 26% 3	840
	11th to 20th	Night	21% 15% 36% 22% 5% 1	840
	21st to end	Night	18% 15% 39% 23% 5%	924
April	1st to 10th	Night	19% 16% 37% 22% 6%	840
	11th to 20th	Night	14% 13% 37% 28% 8%	831
	21st to end	Night	16% 9% 36% 31% 8%	840
May	1st to 10th	Night	17% 10% 31% 32% 8% 1	667
	11th to 20th	Night	17% 5% 27% 37% 14% 1	621
	21st to end	Night	17% 3 19% 37% 22% 3	558
June	1st to 10th	Night	11% 2 19% 44% 23%	420
	11th to 20th	Night	12% 4 19% 40% 23% 3	420
	21st to end	Night	9% 3 17% 46% 24% 1	420
July	1st to 10th	Night	11% 1 12% 40% 31% 4	570
	11th to 20th	Night	6% 2 11% 42% 34% 5%	612
	21st to end	Night	10% 1 16% 42% 27% 3	690
August	1st to 10th	Night	14% 3 11% 44% 25% 3	627
	11th to 20th	Night	13% 3 9% 42% 30% 2	685
	21st to end	Night	12% 2 14% 37% 30% 5%	924
September	1st to 10th	Night	14% 2 12% 35% 30% 6%	840
	11th to 20th	Night	15% 2 13% 35% 30% 4	840
	21st to end	Night	29% 4 14% 32% 19% 2	840
October	1st to 10th	Night	20% 3 19% 30% 22% 6%	840
	11th to 20th	Night	20% 8% 24% 31% 16% 1	813
	21st to end	Night	15% 9% 28% 33% 13% 2	880
November	1st to 10th	Night	16% 8% 27% 33% 13% 2	820
	11th to 20th	Night	17% 13% 29% 30% 10% 1	840
	21st to end	Night	15% 14% 29% 32% 9% 1	840
December	1st to 10th	Night	22% 10% 36% 26% 6% 1	840
	11th to 20th	Night	20% 10% 33% 32% 5%	840
	21st to end	Night	22% 13% 28% 33% 4	924

Page generated at 2026-10-11 05:06:32. Version ac07

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