Pembroke
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pembroke clear sky chart from 2005-11-06 to 2024-05-13.

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% 11% 4 9% 5% 5% 5% 4 5% 6% 31%	83422
	Night	17% 12% 4 9% 5% 5% 4 3 5% 6% 29%	86076
Transparency	Day	52% 7% 11% 19% 10% 1	83127
	Night	55% 7% 11% 18% 9% 1	85905
Seeing	Day	22% 13% 29% 22% 11% 3	13686
	Night	23% 11% 28% 28% 10% 1	22988

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	17% 16% 6% 15% 7% 5% 4 3 3 3 21%	2517
	11th to 20th	Day	13% 13% 5% 18% 8% 6% 4 3 4 5% 20%	2520
	21st to end	Day	14% 20% 7% 15% 6% 5% 4 3 4 4 19%	2973
February	1st to 10th	Day	11% 17% 6% 14% 7% 5% 5% 4 5% 5% 21%	1710
	11th to 20th	Day	12% 15% 5% 10% 7% 5% 4 4 5% 7% 25%	1663
	21st to end	Day	17% 15% 4 9% 6% 6% 5% 4 4 6% 25%	1508
March	1st to 10th	Day	21% 15% 4 8% 5% 4 3 3 4 5% 28%	3234
	11th to 20th	Day	11% 15% 6% 12% 6% 5% 5% 3 4 5% 27%	3480
	21st to end	Day	13% 8% 3 7% 5% 4 4 3 5% 6% 44%	3938
April	1st to 10th	Day	21% 13% 2 6% 5% 4 4 4 5% 5% 30%	2280
	11th to 20th	Day	22% 10% 2 6% 5% 4 4 3 4 5% 35%	2254
	21st to end	Day	21% 9% 3 8% 4 4 4 3 5% 5% 33%	2453
May	1st to 10th	Day	19% 8% 3 8% 5% 4 4 3 5% 6% 35%	2659
	11th to 20th	Day	17% 8% 3 8% 5% 5% 4 3 5% 5% 36%	2509
	21st to end	Day	14% 7% 2 7% 6% 4 5% 4 6% 8% 37%	2725
June	1st to 10th	Day	20% 8% 2 8% 5% 5% 4 5% 4 7% 31%	2520
	11th to 20th	Day	15% 5% 3 6% 5% 5% 5% 5% 6% 8% 39%	2520
	21st to end	Day	15% 8% 3 7% 5% 5% 6% 5% 6% 7% 33%	2520
July	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 4 7% 8% 40%	2520
	11th to 20th	Day	11% 6% 2 6% 6% 6% 6% 5% 7% 8% 37%	2520
	21st to end	Day	11% 6% 2 7% 6% 5% 5% 4 7% 9% 38%	2744
August	1st to 10th	Day	10% 6% 2 8% 6% 6% 6% 5% 6% 8% 37%	2409
	11th to 20th	Day	13% 6% 2 7% 4 5% 6% 4 6% 8% 38%	2303
	21st to end	Day	13% 7% 2 7% 4 5% 5% 5% 7% 9% 36%	2413
September	1st to 10th	Day	14% 5% 3 7% 4 4 4 4 6% 8% 41%	2160
	11th to 20th	Day	13% 7% 3 6% 5% 4 4 3 5% 6% 43%	2160
	21st to end	Day	18% 7% 2 7% 4 5% 5% 5% 5% 7% 35%	1895
October	1st to 10th	Day	19% 9% 3 7% 4 5% 5% 4 4 6% 34%	1800
	11th to 20th	Day	24% 12% 3 9% 5% 4 5% 4 4 6% 25%	1800
	21st to end	Day	27% 10% 3 9% 5% 4 5% 3 5% 7% 22%	1886
November	1st to 10th	Day	15% 10% 4 7% 5% 5% 5% 4 5% 7% 33%	1591
	11th to 20th	Day	18% 14% 4 10% 6% 5% 5% 4 5% 5% 24%	1520
	21st to end	Day	24% 17% 5% 10% 6% 5% 4 4 5% 4 16%	1520
December	1st to 10th	Day	21% 19% 5% 9% 6% 5% 5% 4 5% 4 16%	1520
	11th to 20th	Day	20% 17% 5% 12% 5% 5% 4 4 4 5% 21%	1906
	21st to end	Day	27% 19% 6% 14% 3 2 3 1 2 4 18%	2772
January	1st to 10th	Night	16% 19% 7% 13% 6% 5% 4 3 4 4 17%	4429
	11th to 20th	Night	13% 13% 4 14% 8% 6% 6% 4 5% 6% 20%	4440
	21st to end	Night	13% 21% 7% 12% 7% 6% 4 3 4 4 19%	4678
February	1st to 10th	Night	13% 15% 6% 14% 7% 5% 5% 3 5% 5% 21%	2470
	11th to 20th	Night	13% 14% 6% 12% 7% 5% 5% 3 4 6% 26%	2403
	21st to end	Night	15% 14% 4 10% 7% 5% 4 4 5% 5% 27%	1946
March	1st to 10th	Night	20% 12% 4 10% 5% 4 4 2 4 4 31%	3601
	11th to 20th	Night	16% 17% 5% 10% 5% 4 4 4 5% 6% 24%	3479
	21st to end	Night	14% 8% 3 9% 5% 5% 4 3 5% 6% 36%	3693
April	1st to 10th	Night	19% 12% 3 9% 5% 4 4 4 4 6% 30%	1900
	11th to 20th	Night	20% 10% 3 6% 4 4 4 3 5% 5% 36%	1875
	21st to end	Night	21% 10% 3 9% 5% 4 4 3 5% 6% 32%	1743
May	1st to 10th	Night	18% 9% 3 6% 4 4 3 3 5% 7% 37%	1520
	11th to 20th	Night	20% 7% 2 6% 4 4 5% 3 4 7% 38%	1439
	21st to end	Night	13% 5% 2 5% 4 5% 5% 4 6% 7% 44%	1550
June	1st to 10th	Night	17% 7% 2 7% 6% 5% 4 5% 6% 7% 35%	1440
	11th to 20th	Night	15% 5% 2 6% 4 4 5% 5% 6% 8% 42%	1440
	21st to end	Night	16% 9% 2 4 6% 4 5% 4 7% 8% 35%	1440
July	1st to 10th	Night	11% 4 2 7% 4 4 4 5% 8% 7% 44%	1440
	11th to 20th	Night	12% 7% 2 5% 3 6% 5% 5% 6% 9% 42%	1440
	21st to end	Night	9% 5% 2 6% 5% 6% 5% 5% 6% 9% 43%	1574
August	1st to 10th	Night	10% 4 2 8% 6% 4 5% 4 6% 7% 43%	1526
	11th to 20th	Night	9% 5% 2 7% 4 4 5% 4 7% 9% 44%	1598
	21st to end	Night	11% 7% 2 6% 5% 5% 5% 4 5% 9% 42%	1924
September	1st to 10th	Night	12% 6% 2 7% 5% 4 4 4 6% 7% 45%	1800
	11th to 20th	Night	15% 5% 2 6% 3 3 3 4 5% 7% 46%	1800
	21st to end	Night	18% 7% 3 7% 4 4 3 3 4 7% 41%	2063
October	1st to 10th	Night	20% 7% 3 7% 4 4 3 3 5% 6% 38%	2160
	11th to 20th	Night	22% 10% 3 8% 6% 5% 4 4 4 6% 28%	2160
	21st to end	Night	24% 12% 4 8% 5% 5% 5% 3 4 6% 26%	2470
November	1st to 10th	Night	18% 11% 3 7% 5% 5% 5% 3 5% 6% 32%	2483
	11th to 20th	Night	18% 12% 4 10% 7% 5% 4 3 5% 6% 26%	2660
	21st to end	Night	23% 16% 4 11% 5% 4 4 3 5% 5% 19%	2660
December	1st to 10th	Night	22% 19% 5% 11% 6% 5% 4 3 4 5% 17%	2660
	11th to 20th	Night	20% 19% 5% 9% 5% 4 4 3 4 5% 22%	3288
	21st to end	Night	28% 19% 5% 12% 4 3 3 2 3 3 16%	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	66% 8% 11% 9% 6%	2518
	11th to 20th	Day	66% 6% 9% 12% 6% 1	2520
	21st to end	Day	70% 4 9% 10% 5% 1	2973
February	1st to 10th	Day	64% 6% 9% 16% 5% 1	1710
	11th to 20th	Day	58% 6% 13% 13% 8% 1	1672
	21st to end	Day	60% 5% 9% 15% 10% 1	1508
March	1st to 10th	Day	59% 5% 9% 16% 10% 1	3237
	11th to 20th	Day	58% 6% 11% 14% 9% 1	3480
	21st to end	Day	41% 4 10% 23% 18% 4	3938
April	1st to 10th	Day	55% 4 8% 19% 11% 3	2280
	11th to 20th	Day	52% 4 7% 22% 14% 2	2254
	21st to end	Day	53% 5% 7% 16% 16% 3	2453
May	1st to 10th	Day	48% 7% 9% 19% 13% 5%	2659
	11th to 20th	Day	49% 5% 7% 19% 17% 2	2513
	21st to end	Day	44% 7% 12% 21% 13% 4	2725
June	1st to 10th	Day	51% 7% 10% 19% 12% 1	2520
	11th to 20th	Day	42% 7% 11% 23% 14% 3	2520
	21st to end	Day	47% 9% 11% 20% 12% 1	2520
July	1st to 10th	Day	37% 8% 12% 27% 14% 1	2450
	11th to 20th	Day	39% 9% 13% 25% 13% 1	2445
	21st to end	Day	40% 9% 15% 27% 9%	2591
August	1st to 10th	Day	43% 9% 15% 22% 12%	2395
	11th to 20th	Day	41% 9% 18% 24% 8% 1	2303
	21st to end	Day	41% 9% 16% 23% 10% 1	2413
September	1st to 10th	Day	39% 7% 15% 27% 12%	2160
	11th to 20th	Day	39% 7% 12% 31% 10% 1	2160
	21st to end	Day	47% 8% 13% 24% 8%	1895
October	1st to 10th	Day	51% 8% 10% 20% 11% 1	1800
	11th to 20th	Day	61% 6% 14% 15% 4 1	1800
	21st to end	Day	61% 6% 12% 15% 5% 1	1886
November	1st to 10th	Day	49% 7% 14% 22% 6%	1591
	11th to 20th	Day	60% 7% 13% 13% 6% 1	1520
	21st to end	Day	70% 7% 10% 8% 5%	1520
December	1st to 10th	Day	71% 6% 10% 9% 4	1520
	11th to 20th	Day	65% 8% 7% 13% 7%	1906
	21st to end	Day	74% 3 7% 13% 3	2772
January	1st to 10th	Night	69% 9% 12% 9% 3	4429
	11th to 20th	Night	62% 9% 13% 12% 4	4440
	21st to end	Night	69% 5% 9% 10% 6%	4678
February	1st to 10th	Night	64% 6% 10% 14% 6% 1	2470
	11th to 20th	Night	60% 4 11% 18% 6%	2405
	21st to end	Night	57% 6% 9% 18% 9% 1	1946
March	1st to 10th	Night	56% 5% 13% 16% 8% 1	3611
	11th to 20th	Night	58% 6% 13% 14% 8% 1	3480
	21st to end	Night	45% 6% 10% 20% 15% 3	3693
April	1st to 10th	Night	56% 5% 7% 18% 12% 2	1900
	11th to 20th	Night	50% 5% 8% 21% 14% 2	1875
	21st to end	Night	53% 5% 7% 16% 16% 2	1743
May	1st to 10th	Night	47% 5% 8% 20% 16% 4	1520
	11th to 20th	Night	45% 6% 7% 21% 17% 3	1440
	21st to end	Night	37% 7% 15% 20% 17% 3	1551
June	1st to 10th	Night	46% 8% 12% 23% 10% 1	1440
	11th to 20th	Night	37% 9% 11% 24% 16% 2	1440
	21st to end	Night	44% 8% 14% 21% 13% 1	1440
July	1st to 10th	Night	34% 9% 13% 24% 18% 2	1400
	11th to 20th	Night	38% 8% 13% 27% 13% 1	1392
	21st to end	Night	35% 9% 16% 28% 11%	1486
August	1st to 10th	Night	38% 8% 16% 24% 13%	1516
	11th to 20th	Night	33% 10% 18% 27% 11% 1	1598
	21st to end	Night	37% 8% 16% 27% 11% 1	1924
September	1st to 10th	Night	38% 7% 13% 28% 14% 1	1800
	11th to 20th	Night	37% 7% 16% 31% 9%	1800
	21st to end	Night	42% 8% 14% 28% 8%	2063
October	1st to 10th	Night	47% 6% 11% 23% 13%	2160
	11th to 20th	Night	57% 6% 12% 18% 7%	2160
	21st to end	Night	60% 7% 11% 15% 7%	2470
November	1st to 10th	Night	52% 7% 14% 19% 8%	2483
	11th to 20th	Night	58% 7% 12% 14% 7% 1	2660
	21st to end	Night	65% 7% 11% 13% 3	2660
December	1st to 10th	Night	70% 6% 9% 11% 4	2660
	11th to 20th	Night	64% 6% 10% 14% 7%	3288
	21st to end	Night	74% 4 7% 11% 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% 13% 34% 22% 6% 1	180
	11th to 20th	Day	28% 14% 34% 18% 3 2	180
	21st to end	Day	25% 15% 31% 19% 9% 1	256
February	1st to 10th	Day	25% 19% 36% 16% 4 1	270
	11th to 20th	Day	23% 24% 39% 13%	270
	21st to end	Day	30% 17% 33% 18% 2	320
March	1st to 10th	Day	24% 15% 35% 21% 4 1	460
	11th to 20th	Day	23% 17% 32% 22% 5% 1	460
	21st to end	Day	27% 17% 29% 19% 6% 1	506
April	1st to 10th	Day	28% 17% 30% 14% 9% 1	460
	11th to 20th	Day	33% 15% 22% 17% 10% 4	452
	21st to end	Day	29% 15% 30% 17% 7% 3	460
May	1st to 10th	Day	25% 12% 27% 24% 8% 3	463
	11th to 20th	Day	19% 16% 29% 22% 11% 3	456
	21st to end	Day	18% 11% 35% 21% 12% 3	485
June	1st to 10th	Day	24% 9% 32% 23% 11% 1	450
	11th to 20th	Day	17% 12% 28% 25% 13% 6%	450
	21st to end	Day	18% 10% 30% 23% 16% 3	450
July	1st to 10th	Day	10% 7% 25% 38% 16% 4	445
	11th to 20th	Day	12% 8% 30% 29% 18% 4	444
	21st to end	Day	13% 8% 29% 30% 17% 4	488
August	1st to 10th	Day	13% 7% 26% 29% 18% 7%	446
	11th to 20th	Day	15% 3 23% 29% 21% 9%	439
	21st to end	Day	14% 9% 28% 24% 16% 8%	495
September	1st to 10th	Day	13% 8% 28% 24% 18% 8%	450
	11th to 20th	Day	15% 9% 23% 24% 19% 10%	450
	21st to end	Day	16% 12% 28% 22% 16% 6%	450
October	1st to 10th	Day	26% 13% 22% 20% 15% 4	450
	11th to 20th	Day	29% 18% 28% 17% 7% 1	450
	21st to end	Day	32% 14% 25% 21% 6% 1	448
November	1st to 10th	Day	24% 16% 31% 21% 8% 1	285
	11th to 20th	Day	23% 21% 37% 11% 7% 1	180
	21st to end	Day	33% 22% 30% 10% 3 3	180
December	1st to 10th	Day	28% 12% 38% 16% 6% 1	180
	11th to 20th	Day	27% 19% 34% 14% 3 2	180
	21st to end	Day	28% 22% 27% 19% 3 2	198
January	1st to 10th	Night	26% 14% 31% 24% 4	760
	11th to 20th	Night	28% 13% 28% 24% 7%	760
	21st to end	Night	20% 11% 32% 29% 8%	836
February	1st to 10th	Night	21% 14% 36% 24% 5% 1	760
	11th to 20th	Night	21% 13% 36% 25% 5%	743
	21st to end	Night	23% 15% 30% 27% 5%	628
March	1st to 10th	Night	24% 13% 32% 26% 5%	760
	11th to 20th	Night	24% 16% 30% 23% 6% 1	760
	21st to end	Night	21% 12% 32% 26% 8%	836
April	1st to 10th	Night	26% 13% 29% 26% 6%	760
	11th to 20th	Night	26% 13% 31% 23% 8%	751
	21st to end	Night	26% 10% 26% 27% 10% 1	603
May	1st to 10th	Night	23% 5% 29% 32% 10% 1	380
	11th to 20th	Night	21% 9% 28% 33% 8% 1	360
	21st to end	Night	15% 6% 33% 33% 12% 1	389
June	1st to 10th	Night	19% 5% 29% 40% 7% 1	360
	11th to 20th	Night	15% 8% 27% 35% 15% 1	360
	21st to end	Night	19% 7% 25% 34% 14% 1	360
July	1st to 10th	Night	10% 5% 26% 42% 15% 1	350
	11th to 20th	Night	14% 3 23% 41% 18% 1	348
	21st to end	Night	10% 4 25% 44% 17% 1	394
August	1st to 10th	Night	11% 3 20% 38% 26% 1	452
	11th to 20th	Night	11% 3 16% 40% 27% 3	534
	21st to end	Night	13% 7% 23% 36% 19% 2	736
September	1st to 10th	Night	14% 5% 27% 31% 21% 2	720
	11th to 20th	Night	18% 6% 20% 30% 21% 4	720
	21st to end	Night	21% 8% 21% 27% 20% 2	720
October	1st to 10th	Night	25% 7% 27% 26% 14% 2	720
	11th to 20th	Night	28% 10% 30% 21% 9% 1	720
	21st to end	Night	30% 12% 25% 27% 6% 1	792
November	1st to 10th	Night	24% 14% 25% 28% 8% 1	740
	11th to 20th	Night	23% 17% 31% 19% 9% 1	760
	21st to end	Night	32% 15% 23% 24% 6%	760
December	1st to 10th	Night	30% 15% 29% 19% 6%	760
	11th to 20th	Night	28% 14% 30% 23% 5% 1	760
	21st to end	Night	34% 13% 26% 22% 4	836

Page generated at 2024-05-10 12:39:03. Version ac07

Copyright © 2024 Attilla Danko.