Sam's Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sam's Point clear sky chart from 2005-11-06 to 2024-11-25.

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	17% 7% 3 6% 5% 4 5% 4 6% 7% 37%	101547
	Night	18% 7% 2 6% 4 4 4 3 5% 7% 39%	97917
Transparency	Day	43% 7% 12% 22% 14% 2	105066
	Night	42% 7% 12% 23% 14% 2	102474
Seeing	Day	23% 16% 28% 21% 9% 3	14951
	Night	21% 14% 28% 27% 10% 1	24093

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	14% 8% 3 5% 4 4 4 4 5% 5% 43%	2517
	11th to 20th	Day	14% 10% 4 10% 6% 5% 5% 4 6% 6% 30%	2520
	21st to end	Day	19% 13% 5% 8% 4 4 3 3 4 5% 31%	2978
February	1st to 10th	Day	15% 10% 3 7% 6% 5% 5% 4 6% 6% 33%	1710
	11th to 20th	Day	13% 8% 2 7% 6% 5% 5% 3 5% 6% 40%	1816
	21st to end	Day	20% 10% 3 7% 5% 4 4 3 4 5% 37%	1570
March	1st to 10th	Day	25% 9% 3 7% 4 4 3 3 4 4 34%	3116
	11th to 20th	Day	9% 7% 3 7% 6% 5% 5% 5% 7% 8% 39%	3370
	21st to end	Day	22% 8% 2 6% 4 4 4 3 4 5% 38%	4120
April	1st to 10th	Day	18% 8% 2 7% 5% 4 4 4 5% 6% 36%	2280
	11th to 20th	Day	17% 7% 2 7% 5% 4 5% 3 5% 6% 39%	2254
	21st to end	Day	19% 6% 3 7% 5% 4 4 4 5% 6% 37%	2308
May	1st to 10th	Day	26% 8% 2 6% 4 4 4 4 5% 6% 30%	4170
	11th to 20th	Day	21% 7% 3 7% 5% 5% 5% 4 6% 7% 31%	4398
	21st to end	Day	13% 5% 2 5% 4 4 5% 4 8% 10% 41%	4837
June	1st to 10th	Day	17% 5% 2 7% 4 5% 5% 5% 7% 9% 34%	2660
	11th to 20th	Day	15% 6% 2 7% 5% 4 5% 5% 7% 9% 35%	2660
	21st to end	Day	13% 6% 2 7% 4 5% 6% 4 7% 9% 36%	2660
July	1st to 10th	Day	11% 6% 2 8% 5% 6% 5% 5% 7% 9% 35%	4440
	11th to 20th	Day	11% 5% 2 6% 5% 4 6% 4 8% 11% 37%	4440
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 5% 6% 8% 34%	4814
August	1st to 10th	Day	21% 6% 2 6% 5% 5% 5% 4 6% 7% 32%	4256
	11th to 20th	Day	14% 5% 2 6% 4 4 5% 5% 8% 8% 38%	3730
	21st to end	Day	14% 5% 2 5% 3 4 4 4 6% 10% 44%	4180
September	1st to 10th	Day	15% 6% 2 6% 5% 4 4 3 6% 6% 43%	2280
	11th to 20th	Day	15% 4 1 5% 3 3 4 3 5% 7% 50%	2214
	21st to end	Day	19% 6% 2 5% 4 4 4 4 5% 6% 40%	2090
October	1st to 10th	Day	20% 7% 2 5% 4 4 4 4 4 5% 41%	1955
	11th to 20th	Day	16% 5% 2 5% 4 4 5% 4 6% 7% 42%	1900
	21st to end	Day	22% 8% 2 4 5% 4 4 4 5% 7% 35%	1938
November	1st to 10th	Day	14% 7% 2 5% 3 3 3 2 4 6% 50%	1761
	11th to 20th	Day	17% 6% 2 6% 3 4 4 4 6% 6% 42%	1800
	21st to end	Day	17% 9% 2 6% 4 4 4 4 5% 7% 37%	1607
December	1st to 10th	Day	18% 8% 4 8% 6% 4 4 4 6% 6% 31%	1520
	11th to 20th	Day	22% 6% 2 5% 4 3 4 3 5% 6% 39%	1906
	21st to end	Day	19% 10% 4 10% 7% 5% 5% 4 6% 6% 26%	2772
January	1st to 10th	Night	16% 7% 2 7% 4 4 4 3 5% 6% 42%	4429
	11th to 20th	Night	14% 8% 4 10% 5% 4 4 4 5% 7% 36%	4440
	21st to end	Night	22% 12% 3 5% 4 4 5% 3 5% 6% 30%	4660
February	1st to 10th	Night	15% 9% 3 6% 5% 4 4 3 6% 7% 38%	2470
	11th to 20th	Night	14% 8% 3 7% 5% 4 4 5% 6% 7% 38%	2248
	21st to end	Night	18% 8% 3 6% 4 4 4 3 4 5% 40%	1884
March	1st to 10th	Night	24% 10% 2 5% 4 4 4 3 4 5% 35%	3724
	11th to 20th	Night	11% 8% 2 7% 4 5% 5% 4 7% 7% 40%	3587
	21st to end	Night	15% 10% 3 8% 4 4 4 3 5% 5% 39%	3511
April	1st to 10th	Night	18% 7% 2 7% 5% 5% 5% 4 6% 6% 35%	1900
	11th to 20th	Night	19% 7% 3 6% 4 4 4 3 5% 8% 37%	1875
	21st to end	Night	20% 6% 2 6% 4 4 3 3 4 6% 41%	1872
May	1st to 10th	Night	27% 8% 3 6% 3 3 4 3 6% 7% 31%	2784
	11th to 20th	Night	23% 9% 3 7% 4 3 3 3 5% 6% 32%	2495
	21st to end	Night	14% 6% 2 6% 4 5% 4 3 6% 8% 41%	2738
June	1st to 10th	Night	16% 6% 2 6% 4 4 4 4 5% 9% 41%	1520
	11th to 20th	Night	14% 7% 2 4 4 4 4 4 7% 9% 42%	1520
	21st to end	Night	12% 5% 1 4 3 4 3 4 7% 11% 44%	1520
July	1st to 10th	Night	12% 5% 3 6% 5% 4 5% 5% 7% 9% 40%	2520
	11th to 20th	Night	14% 5% 2 5% 5% 4 4 4 6% 10% 41%	2520
	21st to end	Night	18% 6% 2 6% 4 4 5% 4 5% 7% 38%	2739
August	1st to 10th	Night	21% 6% 2 6% 4 5% 4 4 5% 7% 35%	2655
	11th to 20th	Night	16% 6% 3 6% 4 4 4 4 5% 6% 43%	3080
	21st to end	Night	13% 5% 1 4 4 3 4 3 5% 6% 52%	3476
September	1st to 10th	Night	15% 6% 2 5% 4 3 4 3 5% 7% 47%	1900
	11th to 20th	Night	14% 4 2 4 3 3 3 3 5% 7% 53%	1966
	21st to end	Night	18% 7% 2 5% 3 4 3 3 6% 6% 44%	2090
October	1st to 10th	Night	22% 6% 2 6% 4 3 4 3 4 5% 41%	2222
	11th to 20th	Night	18% 5% 2 5% 3 3 3 3 6% 6% 46%	2280
	21st to end	Night	23% 7% 2 5% 4 3 4 3 5% 7% 38%	2660
November	1st to 10th	Night	13% 5% 3 6% 4 4 4 3 4 6% 48%	2537
	11th to 20th	Night	20% 7% 2 4 3 4 4 3 4 6% 43%	2600
	21st to end	Night	16% 7% 2 6% 4 4 3 4 6% 7% 41%	2663
December	1st to 10th	Night	19% 7% 2 6% 4 4 4 3 6% 7% 36%	2660
	11th to 20th	Night	20% 8% 2 5% 4 3 4 4 6% 7% 35%	3288
	21st to end	Night	21% 10% 3 7% 4 4 4 3 5% 6% 34%	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	38% 8% 11% 33% 9% 2	2518
	11th to 20th	Day	50% 9% 10% 21% 8% 2	2520
	21st to end	Day	55% 6% 9% 21% 8% 1	2978
February	1st to 10th	Day	50% 7% 11% 19% 13% 1	1710
	11th to 20th	Day	44% 6% 10% 21% 16% 3	1825
	21st to end	Day	49% 5% 11% 21% 12% 2	1570
March	1st to 10th	Day	53% 5% 11% 18% 11% 2	3119
	11th to 20th	Day	38% 9% 13% 29% 10% 1	3370
	21st to end	Day	46% 6% 7% 16% 21% 4	4120
April	1st to 10th	Day	48% 6% 9% 20% 13% 4	2280
	11th to 20th	Day	44% 6% 11% 21% 15% 3	2254
	21st to end	Day	46% 6% 10% 20% 14% 4	2308
May	1st to 10th	Day	52% 8% 11% 15% 12% 2	4184
	11th to 20th	Day	51% 8% 13% 18% 8% 1	4402
	21st to end	Day	33% 10% 14% 26% 15% 1	4837
June	1st to 10th	Day	42% 10% 14% 19% 13% 1	2660
	11th to 20th	Day	42% 10% 13% 23% 11% 1	2660
	21st to end	Day	41% 10% 12% 24% 13% 1	2660
July	1st to 10th	Day	43% 9% 13% 20% 15% 1	4370
	11th to 20th	Day	37% 9% 16% 23% 14% 1	4365
	21st to end	Day	47% 7% 12% 18% 14% 2	4661
August	1st to 10th	Day	49% 8% 13% 20% 9%	4242
	11th to 20th	Day	39% 8% 17% 26% 10%	3766
	21st to end	Day	34% 6% 13% 31% 14% 1	4180
September	1st to 10th	Day	41% 7% 11% 22% 17% 1	2280
	11th to 20th	Day	34% 6% 10% 25% 24% 2	2214
	21st to end	Day	43% 7% 10% 21% 17% 2	2090
October	1st to 10th	Day	41% 5% 7% 19% 24% 3	3241
	11th to 20th	Day	32% 5% 9% 27% 24% 3	3140
	21st to end	Day	32% 5% 16% 26% 18% 4	3176
November	1st to 10th	Day	36% 5% 13% 25% 18% 3	1761
	11th to 20th	Day	41% 5% 11% 22% 18% 3	1800
	21st to end	Day	45% 6% 13% 25% 9% 1	1607
December	1st to 10th	Day	50% 8% 13% 16% 12% 1	1520
	11th to 20th	Day	44% 8% 15% 22% 10% 2	1906
	21st to end	Day	55% 9% 10% 18% 7%	2772
January	1st to 10th	Night	41% 7% 12% 27% 11% 3	4429
	11th to 20th	Night	47% 7% 12% 22% 10% 2	4440
	21st to end	Night	52% 7% 10% 19% 9% 1	4660
February	1st to 10th	Night	45% 6% 15% 21% 12% 1	2470
	11th to 20th	Night	44% 7% 11% 18% 17% 3	2250
	21st to end	Night	45% 5% 9% 24% 14% 4	1884
March	1st to 10th	Night	51% 5% 12% 19% 12% 2	3734
	11th to 20th	Night	38% 8% 16% 25% 11% 1	3588
	21st to end	Night	45% 6% 8% 16% 20% 4	3511
April	1st to 10th	Night	48% 6% 10% 19% 14% 2	1900
	11th to 20th	Night	45% 7% 10% 19% 18% 1	1875
	21st to end	Night	44% 6% 10% 21% 16% 4	1872
May	1st to 10th	Night	51% 6% 11% 20% 11% 1	2790
	11th to 20th	Night	51% 8% 13% 17% 10% 1	2496
	21st to end	Night	37% 10% 15% 25% 12% 1	2739
June	1st to 10th	Night	41% 7% 10% 24% 17% 1	1520
	11th to 20th	Night	37% 10% 16% 27% 10%	1520
	21st to end	Night	32% 8% 17% 27% 15% 1	1520
July	1st to 10th	Night	38% 9% 17% 19% 14% 3	2480
	11th to 20th	Night	38% 8% 15% 25% 13% 1	2472
	21st to end	Night	43% 7% 14% 17% 16% 2	2651
August	1st to 10th	Night	49% 7% 16% 19% 8% 1	2645
	11th to 20th	Night	42% 6% 14% 28% 10%	3110
	21st to end	Night	32% 6% 12% 34% 15% 1	3476
September	1st to 10th	Night	38% 7% 12% 26% 17% 1	1900
	11th to 20th	Night	32% 6% 10% 26% 25% 1	1966
	21st to end	Night	39% 7% 10% 22% 21% 1	2090
October	1st to 10th	Night	42% 5% 10% 22% 20% 1	3703
	11th to 20th	Night	28% 4 10% 29% 24% 4	3779
	21st to end	Night	34% 5% 14% 29% 17% 1	4372
November	1st to 10th	Night	37% 6% 11% 23% 21% 3	2537
	11th to 20th	Night	42% 4 11% 21% 18% 3	2600
	21st to end	Night	40% 6% 15% 28% 10% 1	2663
December	1st to 10th	Night	46% 7% 13% 22% 11% 1	2660
	11th to 20th	Night	45% 7% 15% 18% 13% 2	3288
	21st to end	Night	51% 6% 13% 21% 9%	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	28% 22% 29% 16% 6%	180
	11th to 20th	Day	33% 29% 24% 11% 2 1	180
	21st to end	Day	22% 28% 32% 13% 5%	258
February	1st to 10th	Day	35% 26% 27% 10% 2	270
	11th to 20th	Day	28% 29% 30% 11% 1	424
	21st to end	Day	33% 22% 29% 14% 3	382
March	1st to 10th	Day	26% 22% 31% 16% 5%	460
	11th to 20th	Day	29% 25% 27% 16% 3 1	460
	21st to end	Day	31% 20% 29% 13% 4 2	506
April	1st to 10th	Day	31% 22% 26% 14% 6% 1	460
	11th to 20th	Day	29% 24% 27% 12% 7% 2	452
	21st to end	Day	29% 21% 28% 14% 6% 2	460
May	1st to 10th	Day	35% 18% 26% 13% 6% 2	463
	11th to 20th	Day	21% 16% 33% 22% 7% 2	487
	21st to end	Day	19% 10% 31% 24% 14% 2	529
June	1st to 10th	Day	20% 14% 30% 21% 13% 1	490
	11th to 20th	Day	18% 14% 27% 28% 12% 2	490
	21st to end	Day	16% 13% 30% 27% 11% 2	490
July	1st to 10th	Day	14% 9% 28% 28% 16% 4	485
	11th to 20th	Day	13% 7% 27% 32% 17% 4	484
	21st to end	Day	14% 8% 33% 30% 11% 3	532
August	1st to 10th	Day	13% 8% 27% 31% 14% 6%	486
	11th to 20th	Day	17% 7% 24% 30% 16% 6%	479
	21st to end	Day	13% 10% 27% 28% 14% 7%	539
September	1st to 10th	Day	21% 9% 24% 24% 15% 7%	490
	11th to 20th	Day	15% 10% 24% 22% 16% 12%	490
	21st to end	Day	21% 13% 24% 26% 11% 4	490
October	1st to 10th	Day	27% 13% 21% 21% 13% 5%	490
	11th to 20th	Day	18% 17% 28% 23% 11% 2	490
	21st to end	Day	25% 13% 33% 19% 9% 1	459
November	1st to 10th	Day	20% 17% 26% 26% 9% 2	395
	11th to 20th	Day	24% 23% 25% 22% 6% 1	400
	21st to end	Day	26% 22% 29% 19% 5% 1	243
December	1st to 10th	Day	26% 30% 28% 11% 6%	180
	11th to 20th	Day	38% 16% 29% 14% 3	180
	21st to end	Day	27% 26% 28% 16% 3	198
January	1st to 10th	Night	20% 20% 37% 20% 3	760
	11th to 20th	Night	24% 18% 30% 24% 3	760
	21st to end	Night	19% 20% 35% 23% 3	836
February	1st to 10th	Night	22% 19% 34% 24% 1	760
	11th to 20th	Night	22% 22% 37% 17% 1	743
	21st to end	Night	27% 18% 35% 16% 4	628
March	1st to 10th	Night	25% 19% 32% 20% 4	760
	11th to 20th	Night	23% 23% 29% 21% 4	760
	21st to end	Night	22% 21% 33% 20% 5%	836
April	1st to 10th	Night	24% 18% 32% 21% 4	760
	11th to 20th	Night	24% 16% 30% 25% 5%	751
	21st to end	Night	24% 16% 28% 24% 6% 1	732
May	1st to 10th	Night	26% 13% 27% 25% 8%	546
	11th to 20th	Night	22% 11% 30% 31% 7%	374
	21st to end	Night	16% 8% 21% 39% 15% 1	411
June	1st to 10th	Night	17% 6% 26% 36% 14% 1	380
	11th to 20th	Night	16% 6% 23% 38% 17% 1	380
	21st to end	Night	12% 4 24% 46% 14% 1	380
July	1st to 10th	Night	15% 4 18% 42% 21% 1	370
	11th to 20th	Night	11% 4 19% 46% 18% 1	368
	21st to end	Night	13% 5% 20% 44% 17% 1	416
August	1st to 10th	Night	12% 2 21% 44% 20% 2	462
	11th to 20th	Night	14% 4 18% 38% 23% 2	733
	21st to end	Night	16% 6% 16% 36% 25% 2	836
September	1st to 10th	Night	17% 6% 22% 34% 19% 2	760
	11th to 20th	Night	16% 7% 20% 30% 22% 5%	760
	21st to end	Night	20% 8% 21% 32% 17% 3	760
October	1st to 10th	Night	24% 11% 22% 25% 16% 2	760
	11th to 20th	Night	20% 13% 25% 32% 10% 1	760
	21st to end	Night	27% 13% 30% 23% 7%	836
November	1st to 10th	Night	17% 13% 31% 29% 10%	780
	11th to 20th	Night	24% 19% 26% 24% 7% 1	800
	21st to end	Night	21% 17% 29% 25% 7% 1	779
December	1st to 10th	Night	26% 17% 30% 22% 5%	760
	11th to 20th	Night	24% 21% 26% 25% 4	760
	21st to end	Night	27% 16% 34% 22% 2	836

Page generated at 2024-11-22 08:02:28. Version ac07

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