Breyo Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Breyo Observatory clear sky chart from 2005-11-06 to 2024-12-02.

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	16% 8% 3 8% 5% 5% 5% 4 6% 7% 34%	101616
	Night	17% 9% 3 8% 5% 4 4 4 5% 6% 33%	98011
Transparency	Day	47% 6% 13% 22% 11% 1	105123
	Night	50% 6% 12% 21% 11% 1	102593
Seeing	Day	22% 12% 29% 22% 11% 3	14903
	Night	22% 11% 30% 28% 8% 1	23979

By Month

Percentage Cloud Cover NE (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	13% 11% 5% 10% 7% 6% 6% 4 5% 6% 29%	2517
	11th to 20th	Day	16% 13% 4 13% 6% 5% 4 4 6% 5% 23%	2520
	21st to end	Day	20% 13% 4 9% 6% 5% 5% 3 5% 7% 23%	2866
February	1st to 10th	Day	17% 11% 4 7% 7% 5% 5% 5% 7% 8% 26%	1710
	11th to 20th	Day	12% 13% 4 9% 7% 5% 5% 4 6% 6% 28%	1824
	21st to end	Day	18% 11% 3 11% 5% 4 5% 4 5% 5% 29%	1570
March	1st to 10th	Day	24% 12% 5% 8% 5% 3 3 3 4 5% 29%	3116
	11th to 20th	Day	13% 13% 4 10% 5% 5% 4 3 5% 6% 33%	3288
	21st to end	Day	19% 8% 3 8% 5% 5% 5% 3 4 5% 35%	4161
April	1st to 10th	Day	18% 10% 4 7% 5% 4 4 3 5% 6% 34%	2280
	11th to 20th	Day	17% 8% 2 7% 5% 5% 5% 4 5% 6% 36%	2254
	21st to end	Day	20% 8% 3 7% 4 5% 4 4 5% 6% 33%	2367
May	1st to 10th	Day	23% 9% 3 7% 5% 4 4 3 5% 6% 30%	4187
	11th to 20th	Day	16% 8% 3 8% 5% 5% 5% 4 5% 7% 33%	4398
	21st to end	Day	10% 6% 2 6% 4 5% 5% 4 7% 9% 42%	4837
June	1st to 10th	Day	14% 6% 2 7% 5% 6% 6% 5% 7% 7% 34%	2660
	11th to 20th	Day	14% 6% 3 6% 5% 5% 5% 5% 7% 10% 34%	2660
	21st to end	Day	15% 7% 3 7% 4 5% 5% 5% 6% 8% 35%	2660
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 10% 37%	4440
	11th to 20th	Day	9% 6% 2 7% 5% 6% 6% 5% 7% 10% 37%	4440
	21st to end	Day	12% 6% 3 7% 5% 6% 6% 5% 8% 8% 35%	4814
August	1st to 10th	Day	15% 7% 2 7% 5% 5% 6% 5% 7% 8% 33%	4391
	11th to 20th	Day	13% 7% 2 7% 5% 5% 6% 5% 8% 9% 33%	3730
	21st to end	Day	10% 6% 2 6% 4 5% 5% 5% 7% 10% 39%	4180
September	1st to 10th	Day	12% 6% 2 5% 4 4 5% 4 5% 9% 43%	2280
	11th to 20th	Day	12% 5% 2 5% 3 4 4 3 5% 8% 48%	2191
	21st to end	Day	16% 5% 2 6% 4 4 5% 4 7% 6% 40%	2090
October	1st to 10th	Day	18% 8% 3 9% 5% 5% 4 4 4 5% 35%	1986
	11th to 20th	Day	14% 8% 3 8% 3 5% 4 4 6% 7% 39%	1900
	21st to end	Day	24% 8% 2 6% 5% 4 4 5% 6% 6% 30%	1887
November	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 6% 6% 43%	1761
	11th to 20th	Day	15% 8% 2 7% 5% 4 5% 4 5% 5% 38%	1800
	21st to end	Day	18% 10% 3 7% 4 4 5% 4 5% 7% 32%	1645
December	1st to 10th	Day	19% 13% 5% 8% 5% 5% 5% 4 5% 7% 25%	1528
	11th to 20th	Day	23% 12% 3 7% 5% 3 3 3 3 6% 32%	1906
	21st to end	Day	24% 16% 5% 9% 5% 5% 3 3 4 5% 21%	2772
January	1st to 10th	Night	16% 13% 4 10% 5% 5% 4 3 4 5% 31%	4429
	11th to 20th	Night	13% 14% 6% 11% 6% 5% 4 4 4 6% 26%	4440
	21st to end	Night	23% 12% 4 10% 7% 4 4 3 4 5% 24%	4788
February	1st to 10th	Night	16% 12% 5% 10% 6% 5% 4 4 6% 6% 27%	2470
	11th to 20th	Night	12% 11% 5% 11% 7% 5% 5% 4 6% 5% 30%	2241
	21st to end	Night	17% 11% 4 10% 6% 5% 4 4 5% 6% 29%	1884
March	1st to 10th	Night	24% 11% 4 9% 5% 4 4 4 4 5% 26%	3724
	11th to 20th	Night	17% 12% 3 8% 5% 4 5% 4 4 5% 33%	3656
	21st to end	Night	16% 11% 4 11% 5% 4 4 3 4 3 33%	3471
April	1st to 10th	Night	19% 11% 3 7% 5% 4 4 4 5% 7% 31%	1900
	11th to 20th	Night	20% 7% 3 8% 5% 5% 4 3 5% 6% 34%	1875
	21st to end	Night	20% 6% 3 7% 5% 3 4 4 5% 6% 37%	1811
May	1st to 10th	Night	22% 10% 3 8% 5% 4 4 3 4 5% 31%	2783
	11th to 20th	Night	16% 9% 2 9% 7% 5% 7% 4 6% 7% 29%	2495
	21st to end	Night	11% 6% 2 7% 6% 5% 4 4 6% 8% 39%	2738
June	1st to 10th	Night	16% 7% 2 5% 5% 5% 4 4 5% 8% 38%	1520
	11th to 20th	Night	15% 5% 2 5% 4 4 5% 5% 7% 8% 39%	1520
	21st to end	Night	13% 5% 2 6% 4 5% 4 5% 7% 9% 41%	1520
July	1st to 10th	Night	10% 6% 3 7% 6% 6% 6% 4 7% 7% 38%	2520
	11th to 20th	Night	14% 6% 2 7% 4 5% 5% 4 6% 8% 38%	2520
	21st to end	Night	12% 7% 3 7% 5% 5% 5% 4 6% 7% 39%	2739
August	1st to 10th	Night	20% 7% 2 7% 4 4 5% 3 6% 7% 33%	2506
	11th to 20th	Night	15% 7% 3 7% 5% 5% 4 4 6% 7% 37%	3083
	21st to end	Night	12% 6% 3 6% 4 4 5% 4 6% 8% 42%	3476
September	1st to 10th	Night	13% 8% 3 6% 4 3 4 4 5% 6% 43%	1900
	11th to 20th	Night	14% 4 2 4 3 3 3 3 5% 8% 51%	1988
	21st to end	Night	15% 6% 2 6% 5% 4 4 4 6% 6% 42%	2090
October	1st to 10th	Night	18% 8% 3 8% 4 5% 5% 3 5% 6% 35%	2190
	11th to 20th	Night	16% 6% 2 7% 5% 5% 4 5% 5% 6% 40%	2280
	21st to end	Night	23% 8% 3 6% 5% 4 4 4 5% 7% 31%	2709
November	1st to 10th	Night	15% 9% 3 6% 4 4 4 3 5% 5% 42%	2537
	11th to 20th	Night	16% 8% 3 8% 5% 4 5% 4 5% 5% 37%	2600
	21st to end	Night	16% 10% 3 7% 5% 4 5% 4 6% 6% 34%	2750
December	1st to 10th	Night	20% 12% 4 8% 4 5% 5% 4 5% 6% 28%	2686
	11th to 20th	Night	23% 10% 4 7% 5% 4 4 4 6% 6% 28%	3288
	21st to end	Night	26% 14% 5% 9% 5% 4 3 3 4 5% 22%	4884

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	53% 8% 11% 23% 6%	2518
	11th to 20th	Day	61% 6% 12% 15% 5% 1	2520
	21st to end	Day	62% 5% 13% 15% 5% 1	2866
February	1st to 10th	Day	55% 6% 14% 17% 7% 1	1710
	11th to 20th	Day	55% 6% 10% 19% 9% 1	1833
	21st to end	Day	56% 6% 10% 17% 11% 1	1570
March	1st to 10th	Day	58% 5% 13% 16% 7% 1	3119
	11th to 20th	Day	50% 5% 16% 18% 8% 2	3288
	21st to end	Day	50% 7% 6% 18% 17% 2	4161
April	1st to 10th	Day	51% 4 9% 22% 12% 2	2280
	11th to 20th	Day	47% 6% 10% 20% 15% 2	2254
	21st to end	Day	51% 5% 9% 18% 14% 3	2367
May	1st to 10th	Day	55% 4 10% 18% 11% 1	4201
	11th to 20th	Day	49% 5% 15% 21% 9% 2	4402
	21st to end	Day	37% 7% 14% 26% 14% 1	4837
June	1st to 10th	Day	46% 7% 14% 21% 11% 1	2660
	11th to 20th	Day	44% 6% 15% 21% 13% 1	2660
	21st to end	Day	45% 6% 15% 22% 11% 1	2660
July	1st to 10th	Day	40% 8% 13% 24% 14% 1	4370
	11th to 20th	Day	40% 7% 15% 26% 12%	4365
	21st to end	Day	43% 7% 16% 21% 12%	4661
August	1st to 10th	Day	47% 7% 15% 22% 9% 1	4377
	11th to 20th	Day	44% 7% 18% 25% 6%	3766
	21st to end	Day	38% 8% 15% 29% 10% 1	4180
September	1st to 10th	Day	37% 7% 13% 27% 15% 1	2280
	11th to 20th	Day	36% 5% 11% 27% 20% 1	2191
	21st to end	Day	41% 7% 11% 26% 13% 2	2090
October	1st to 10th	Day	45% 6% 8% 24% 16% 1	3298
	11th to 20th	Day	38% 5% 12% 29% 15% 1	3140
	21st to end	Day	38% 6% 15% 28% 12% 1	3087
November	1st to 10th	Day	40% 6% 14% 26% 12% 1	1761
	11th to 20th	Day	47% 6% 11% 21% 14% 2	1800
	21st to end	Day	51% 6% 16% 20% 7% 1	1645
December	1st to 10th	Day	60% 5% 11% 16% 7%	1528
	11th to 20th	Day	55% 5% 15% 18% 7% 1	1906
	21st to end	Day	67% 5% 8% 15% 5%	2772
January	1st to 10th	Night	54% 6% 14% 17% 8% 1	4429
	11th to 20th	Night	57% 7% 11% 16% 8% 1	4440
	21st to end	Night	64% 4 11% 16% 5% 1	4788
February	1st to 10th	Night	57% 5% 12% 17% 7% 1	2470
	11th to 20th	Night	54% 5% 12% 19% 9% 1	2243
	21st to end	Night	55% 5% 13% 17% 8% 2	1884
March	1st to 10th	Night	60% 5% 8% 18% 9% 1	3734
	11th to 20th	Night	53% 4 12% 22% 7% 1	3657
	21st to end	Night	52% 7% 5% 16% 16% 3	3471
April	1st to 10th	Night	52% 4 11% 21% 11% 2	1900
	11th to 20th	Night	49% 5% 9% 20% 15% 1	1875
	21st to end	Night	47% 5% 11% 19% 15% 4	1811
May	1st to 10th	Night	56% 5% 11% 15% 12% 2	2789
	11th to 20th	Night	53% 6% 12% 19% 8% 2	2496
	21st to end	Night	42% 6% 14% 21% 15% 2	2739
June	1st to 10th	Night	44% 5% 13% 24% 13% 1	1520
	11th to 20th	Night	41% 6% 17% 23% 12% 1	1520
	21st to end	Night	38% 8% 16% 24% 13% 1	1520
July	1st to 10th	Night	42% 8% 13% 20% 16% 1	2480
	11th to 20th	Night	41% 7% 13% 25% 13%	2472
	21st to end	Night	43% 6% 11% 27% 11% 1	2651
August	1st to 10th	Night	48% 8% 14% 22% 7% 1	2496
	11th to 20th	Night	45% 6% 17% 22% 9%	3113
	21st to end	Night	37% 7% 14% 31% 11% 1	3476
September	1st to 10th	Night	41% 6% 10% 27% 15% 1	1900
	11th to 20th	Night	33% 4 12% 27% 22% 1	1988
	21st to end	Night	41% 6% 11% 24% 17% 1	2090
October	1st to 10th	Night	49% 6% 11% 21% 13% 1	3658
	11th to 20th	Night	35% 6% 11% 27% 19% 1	3779
	21st to end	Night	43% 5% 13% 29% 10%	4459
November	1st to 10th	Night	43% 6% 11% 22% 16% 2	2537
	11th to 20th	Night	48% 5% 11% 22% 12% 2	2600
	21st to end	Night	50% 5% 16% 21% 8% 1	2750
December	1st to 10th	Night	56% 7% 13% 19% 6%	2686
	11th to 20th	Night	56% 6% 14% 16% 8% 1	3288
	21st to end	Night	65% 4 10% 17% 4	4884

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	25% 21% 27% 19% 6% 1	180
	11th to 20th	Day	33% 17% 28% 17% 3 1	180
	21st to end	Day	24% 16% 34% 17% 6% 1	225
February	1st to 10th	Day	32% 20% 37% 9% 1	270
	11th to 20th	Day	29% 22% 35% 12% 2	432
	21st to end	Day	30% 18% 30% 19% 3	382
March	1st to 10th	Day	28% 15% 33% 19% 5%	460
	11th to 20th	Day	29% 18% 30% 18% 4	460
	21st to end	Day	32% 18% 26% 14% 8% 1	506
April	1st to 10th	Day	32% 17% 26% 18% 6% 1	460
	11th to 20th	Day	27% 20% 26% 16% 9% 1	452
	21st to end	Day	29% 14% 32% 16% 6% 3	460
May	1st to 10th	Day	29% 11% 29% 19% 9% 2	463
	11th to 20th	Day	19% 12% 33% 26% 8% 2	487
	21st to end	Day	17% 8% 31% 28% 12% 4	529
June	1st to 10th	Day	18% 12% 31% 24% 12% 3	490
	11th to 20th	Day	18% 9% 30% 26% 16% 2	490
	21st to end	Day	18% 11% 33% 23% 13% 3	490
July	1st to 10th	Day	12% 7% 27% 32% 15% 6%	485
	11th to 20th	Day	12% 6% 27% 32% 17% 5%	484
	21st to end	Day	14% 5% 30% 30% 17% 4	532
August	1st to 10th	Day	16% 3 25% 31% 18% 7%	486
	11th to 20th	Day	16% 4 26% 29% 17% 9%	479
	21st to end	Day	13% 9% 25% 29% 18% 7%	539
September	1st to 10th	Day	17% 8% 24% 24% 18% 9%	490
	11th to 20th	Day	16% 7% 26% 19% 19% 14%	490
	21st to end	Day	19% 8% 25% 25% 16% 8%	490
October	1st to 10th	Day	23% 11% 26% 20% 15% 6%	490
	11th to 20th	Day	19% 15% 29% 23% 11% 2	490
	21st to end	Day	30% 11% 28% 23% 7%	432
November	1st to 10th	Day	22% 17% 25% 22% 13% 2	395
	11th to 20th	Day	25% 19% 30% 19% 6% 1	400
	21st to end	Day	29% 15% 28% 22% 5%	245
December	1st to 10th	Day	25% 15% 38% 16% 4 1	182
	11th to 20th	Day	28% 19% 36% 13% 5%	180
	21st to end	Day	28% 19% 33% 18% 2 1	198
January	1st to 10th	Night	23% 15% 37% 23% 3	760
	11th to 20th	Night	26% 16% 31% 24% 3	760
	21st to end	Night	21% 17% 35% 24% 3	836
February	1st to 10th	Night	24% 16% 37% 20% 2	760
	11th to 20th	Night	21% 18% 39% 21% 1	743
	21st to end	Night	25% 18% 33% 19% 4	628
March	1st to 10th	Night	25% 18% 34% 19% 3	760
	11th to 20th	Night	27% 17% 33% 20% 3	760
	21st to end	Night	24% 18% 30% 22% 5%	836
April	1st to 10th	Night	26% 16% 32% 23% 3	760
	11th to 20th	Night	25% 15% 33% 21% 5%	751
	21st to end	Night	23% 15% 31% 26% 5%	671
May	1st to 10th	Night	27% 13% 28% 25% 7%	545
	11th to 20th	Night	19% 11% 33% 29% 7% 1	374
	21st to end	Night	12% 8% 32% 37% 10% 1	411
June	1st to 10th	Night	19% 5% 32% 32% 11% 1	380
	11th to 20th	Night	17% 5% 29% 38% 11%	380
	21st to end	Night	14% 6% 28% 41% 12%	380
July	1st to 10th	Night	13% 3 28% 42% 14% 1	370
	11th to 20th	Night	14% 3 23% 41% 17% 1	368
	21st to end	Night	13% 3 22% 48% 13% 1	416
August	1st to 10th	Night	13% 3 21% 46% 17% 1	378
	11th to 20th	Night	14% 4 21% 38% 19% 4	736
	21st to end	Night	17% 4 21% 36% 19% 2	836
September	1st to 10th	Night	16% 5% 26% 36% 16% 1	760
	11th to 20th	Night	18% 4 24% 30% 20% 4	760
	21st to end	Night	18% 5% 26% 35% 15% 2	760
October	1st to 10th	Night	22% 8% 24% 30% 14% 2	760
	11th to 20th	Night	19% 9% 31% 32% 10%	760
	21st to end	Night	28% 8% 32% 26% 5%	836
November	1st to 10th	Night	22% 12% 32% 26% 8%	780
	11th to 20th	Night	22% 12% 34% 24% 7% 1	800
	21st to end	Night	23% 12% 34% 25% 6%	800
December	1st to 10th	Night	27% 16% 35% 19% 4	768
	11th to 20th	Night	28% 13% 30% 24% 4	760
	21st to end	Night	31% 14% 32% 21% 2	836

Page generated at 2024-11-29 10:43:07. Version ac07

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