Canfield
Clear Sky Chart
History

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

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 8% 5% 5% 4 4 5% 7% 31%	101146
	Night	17% 11% 4 8% 5% 4 4 3 5% 6% 32%	97969
Transparency	Day	50% 7% 12% 20% 10% 1	104809
	Night	50% 7% 11% 19% 11% 1	102445
Seeing	Day	21% 14% 28% 21% 12% 4	14665
	Night	22% 11% 27% 27% 12% 1	24391

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	19% 22% 8% 12% 5% 4 3 3 3 6% 16%	2836
	11th to 20th	Day	14% 24% 8% 12% 7% 5% 3 2 4 5% 16%	2840
	21st to end	Day	26% 20% 10% 13% 7% 3 3 2 4 4 9%	3124
February	1st to 10th	Day	18% 19% 4 11% 8% 4 3 2 3 4 22%	1710
	11th to 20th	Day	15% 14% 6% 14% 7% 4 5% 3 5% 5% 21%	1672
	21st to end	Day	20% 15% 4 11% 5% 4 4 3 5% 5% 24%	1570
March	1st to 10th	Day	22% 12% 6% 8% 5% 4 3 3 5% 5% 27%	3423
	11th to 20th	Day	13% 12% 5% 10% 6% 5% 5% 3 3 5% 34%	3480
	21st to end	Day	20% 11% 5% 9% 5% 4 4 3 4 6% 29%	3815
April	1st to 10th	Day	16% 14% 3 7% 5% 4 5% 3 4 8% 30%	2161
	11th to 20th	Day	18% 11% 3 7% 5% 4 4 4 5% 6% 33%	2350
	21st to end	Day	21% 11% 3 7% 5% 3 3 3 5% 6% 33%	2470
May	1st to 10th	Day	22% 9% 3 7% 5% 5% 5% 4 5% 6% 28%	4082
	11th to 20th	Day	21% 9% 2 7% 5% 5% 4 4 5% 7% 31%	4081
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 6% 8% 39%	4661
June	1st to 10th	Day	15% 7% 2 6% 6% 4 5% 4 7% 8% 34%	2660
	11th to 20th	Day	14% 6% 3 7% 5% 5% 5% 4 6% 9% 36%	2660
	21st to end	Day	13% 5% 2 6% 5% 5% 5% 5% 7% 10% 38%	2660
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 5% 6% 10% 40%	4230
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 5% 8% 10% 40%	4120
	21st to end	Day	11% 7% 2 7% 6% 6% 5% 5% 6% 8% 37%	4466
August	1st to 10th	Day	16% 8% 3 7% 6% 5% 6% 5% 6% 8% 31%	4104
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 5% 8% 9% 33%	4044
	21st to end	Day	9% 5% 3 7% 5% 6% 5% 5% 7% 9% 39%	4384
September	1st to 10th	Day	14% 6% 2 5% 4 4 5% 3 5% 7% 45%	2237
	11th to 20th	Day	12% 6% 3 6% 4 4 5% 4 6% 8% 44%	2090
	21st to end	Day	20% 8% 3 7% 4 4 4 3 5% 7% 36%	2090
October	1st to 10th	Day	15% 7% 2 7% 5% 4 5% 4 6% 7% 37%	1929
	11th to 20th	Day	19% 10% 3 8% 6% 5% 4 3 5% 5% 33%	1900
	21st to end	Day	22% 11% 3 7% 4 5% 4 3 4 7% 30%	2090
November	1st to 10th	Day	12% 8% 3 8% 5% 4 4 3 5% 6% 40%	1814
	11th to 20th	Day	16% 16% 4 7% 4 4 5% 4 4 6% 29%	1630
	21st to end	Day	17% 16% 7% 11% 4 5% 4 4 5% 6% 23%	1520
December	1st to 10th	Day	21% 19% 6% 11% 6% 4 4 4 5% 4 17%	1520
	11th to 20th	Day	18% 18% 8% 13% 4 4 4 3 5% 6% 17%	1910
	21st to end	Day	26% 24% 7% 10% 5% 4 3 2 3 4 11%	2813
January	1st to 10th	Night	16% 21% 8% 14% 5% 5% 3 3 4 5% 16%	4109
	11th to 20th	Night	15% 19% 8% 16% 6% 5% 6% 4 3 4 13%	4120
	21st to end	Night	27% 17% 9% 13% 5% 4 3 2 3 3 14%	4532
February	1st to 10th	Night	21% 13% 6% 10% 6% 6% 4 3 4 5% 22%	2470
	11th to 20th	Night	17% 14% 6% 12% 6% 6% 4 3 5% 4 23%	2391
	21st to end	Night	20% 14% 5% 10% 5% 5% 4 3 4 5% 24%	1884
March	1st to 10th	Night	23% 14% 3 6% 4 3 3 2 3 5% 32%	3428
	11th to 20th	Night	18% 11% 5% 8% 4 4 4 4 4 6% 32%	3480
	21st to end	Night	18% 11% 4 8% 4 4 4 3 4 5% 37%	3817
April	1st to 10th	Night	16% 14% 3 7% 5% 4 4 3 5% 6% 33%	2019
	11th to 20th	Night	16% 10% 3 7% 4 5% 4 4 6% 7% 34%	1796
	21st to end	Night	16% 10% 2 7% 5% 4 4 3 6% 7% 36%	1710
May	1st to 10th	Night	27% 9% 3 7% 4 4 4 3 5% 6% 28%	2813
	11th to 20th	Night	17% 9% 3 7% 4 4 4 3 5% 8% 36%	2812
	21st to end	Night	10% 5% 2 4 4 4 4 4 7% 11% 44%	2889
June	1st to 10th	Night	9% 5% 3 7% 6% 6% 5% 4 6% 6% 43%	1520
	11th to 20th	Night	10% 5% 3 6% 5% 5% 5% 4 6% 8% 43%	1520
	21st to end	Night	11% 4 2 7% 5% 5% 4 5% 7% 9% 42%	1520
July	1st to 10th	Night	11% 7% 2 7% 5% 5% 4 4 5% 8% 43%	2711
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 7% 9% 47%	2840
	21st to end	Night	9% 6% 2 7% 5% 4 5% 4 7% 8% 43%	3087
August	1st to 10th	Night	13% 8% 4 8% 4 5% 5% 4 5% 7% 38%	2825
	11th to 20th	Night	13% 7% 3 7% 4 4 4 3 5% 6% 43%	2785
	21st to end	Night	8% 4 2 7% 5% 5% 5% 5% 7% 8% 45%	3238
September	1st to 10th	Night	13% 5% 2 6% 3 3 4 3 5% 6% 49%	1941
	11th to 20th	Night	11% 4 2 5% 3 4 4 3 5% 8% 52%	2090
	21st to end	Night	18% 7% 3 5% 4 4 4 4 5% 7% 39%	2090
October	1st to 10th	Night	15% 5% 2 5% 5% 5% 4 4 5% 7% 45%	2251
	11th to 20th	Night	17% 7% 3 7% 5% 5% 5% 3 5% 7% 36%	2280
	21st to end	Night	23% 8% 2 6% 4 4 4 3 4 6% 35%	2508
November	1st to 10th	Night	15% 9% 2 4 4 4 4 4 5% 7% 43%	2481
	11th to 20th	Night	17% 15% 4 8% 5% 4 4 3 5% 5% 31%	2569
	21st to end	Night	19% 16% 4 8% 5% 4 5% 3 4 6% 27%	2660
December	1st to 10th	Night	21% 18% 6% 10% 5% 4 4 3 4 5% 20%	2660
	11th to 20th	Night	17% 20% 6% 11% 5% 4 3 3 5% 5% 21%	3285
	21st to end	Night	26% 20% 7% 9% 5% 4 4 3 4 4 12%	4838

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	70% 6% 8% 12% 3	2837
	11th to 20th	Day	71% 5% 9% 12% 3	2840
	21st to end	Day	80% 6% 6% 6% 2	3124
February	1st to 10th	Day	68% 4 8% 12% 6%	1710
	11th to 20th	Day	65% 7% 9% 13% 7%	1681
	21st to end	Day	61% 7% 10% 14% 7% 1	1570
March	1st to 10th	Day	57% 8% 10% 20% 4	3423
	11th to 20th	Day	50% 9% 13% 22% 6% 1	3480
	21st to end	Day	54% 7% 10% 17% 12% 1	3815
April	1st to 10th	Day	52% 7% 11% 17% 12% 1	2161
	11th to 20th	Day	50% 7% 11% 17% 13% 2	2350
	21st to end	Day	51% 6% 11% 20% 9% 2	2470
May	1st to 10th	Day	53% 9% 10% 19% 8% 1	4120
	11th to 20th	Day	49% 9% 12% 20% 9% 1	4085
	21st to end	Day	38% 10% 14% 21% 13% 4	4675
June	1st to 10th	Day	45% 8% 13% 22% 11% 1	2660
	11th to 20th	Day	43% 9% 13% 21% 13% 1	2660
	21st to end	Day	39% 9% 14% 24% 13% 1	2660
July	1st to 10th	Day	38% 7% 14% 23% 15% 3	4165
	11th to 20th	Day	36% 8% 13% 26% 17% 1	4051
	21st to end	Day	42% 8% 13% 19% 16% 1	4324
August	1st to 10th	Day	48% 8% 14% 21% 9%	4091
	11th to 20th	Day	41% 9% 13% 28% 8% 1	4083
	21st to end	Day	38% 9% 13% 27% 12% 2	4384
September	1st to 10th	Day	40% 7% 12% 21% 17% 3	2237
	11th to 20th	Day	37% 8% 13% 24% 17% 1	2090
	21st to end	Day	47% 7% 12% 21% 11% 1	2090
October	1st to 10th	Day	33% 6% 13% 28% 19% 1	3202
	11th to 20th	Day	47% 6% 11% 19% 14% 4	3140
	21st to end	Day	40% 5% 12% 26% 15% 1	3428
November	1st to 10th	Day	43% 7% 12% 22% 16% 2	1814
	11th to 20th	Day	55% 7% 11% 17% 8% 3	1630
	21st to end	Day	61% 7% 11% 15% 6% 1	1520
December	1st to 10th	Day	70% 6% 11% 11% 3	1520
	11th to 20th	Day	67% 7% 9% 14% 3	1906
	21st to end	Day	78% 5% 9% 7% 2	2813
January	1st to 10th	Night	70% 7% 10% 10% 3	4109
	11th to 20th	Night	73% 6% 9% 9% 2	4120
	21st to end	Night	77% 4 6% 11% 2	4532
February	1st to 10th	Night	64% 5% 10% 15% 5%	2470
	11th to 20th	Night	63% 5% 10% 15% 6%	2393
	21st to end	Night	62% 6% 8% 14% 8% 1	1884
March	1st to 10th	Night	55% 5% 10% 21% 8%	3428
	11th to 20th	Night	50% 8% 15% 19% 6% 1	3480
	21st to end	Night	47% 7% 11% 21% 12% 1	3817
April	1st to 10th	Night	51% 6% 11% 17% 13% 2	2019
	11th to 20th	Night	48% 7% 12% 16% 14% 2	1796
	21st to end	Night	45% 7% 13% 19% 14% 2	1710
May	1st to 10th	Night	55% 7% 9% 19% 9% 2	2840
	11th to 20th	Night	44% 9% 11% 23% 10% 2	2813
	21st to end	Night	30% 10% 17% 26% 14% 3	2896
June	1st to 10th	Night	37% 9% 13% 23% 15% 2	1520
	11th to 20th	Night	37% 7% 15% 23% 16% 2	1520
	21st to end	Night	37% 9% 13% 23% 17% 1	1520
July	1st to 10th	Night	40% 7% 12% 21% 18% 2	2666
	11th to 20th	Night	32% 8% 14% 29% 16% 1	2786
	21st to end	Night	37% 8% 13% 17% 23% 2	2988
August	1st to 10th	Night	44% 7% 12% 23% 13% 1	2814
	11th to 20th	Night	40% 7% 11% 28% 14% 1	2812
	21st to end	Night	34% 8% 12% 30% 13% 2	3238
September	1st to 10th	Night	34% 7% 12% 24% 18% 4	1941
	11th to 20th	Night	30% 7% 14% 25% 22% 2	2090
	21st to end	Night	44% 6% 12% 20% 17% 1	2090
October	1st to 10th	Night	34% 5% 10% 27% 23% 1	3758
	11th to 20th	Night	40% 7% 12% 23% 13% 7%	3779
	21st to end	Night	37% 5% 10% 30% 17% 2	4120
November	1st to 10th	Night	40% 7% 11% 23% 15% 3	2481
	11th to 20th	Night	55% 6% 10% 17% 8% 3	2569
	21st to end	Night	58% 7% 12% 18% 5% 1	2660
December	1st to 10th	Night	67% 7% 11% 11% 4	2660
	11th to 20th	Night	65% 7% 11% 14% 3	3288
	21st to end	Night	73% 8% 9% 8% 1	4838

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	33% 22% 31% 11% 4	270
	11th to 20th	Day	33% 21% 34% 9% 3	270
	21st to end	Day	29% 26% 32% 10% 3 1	297
February	1st to 10th	Day	31% 20% 39% 9% 1	270
	11th to 20th	Day	29% 27% 32% 9% 2	270
	21st to end	Day	35% 23% 34% 9%	225
March	1st to 10th	Day	28% 17% 34% 16% 4	448
	11th to 20th	Day	30% 16% 33% 14% 5% 2	460
	21st to end	Day	33% 19% 26% 17% 4 1	506
April	1st to 10th	Day	24% 23% 30% 15% 7% 1	460
	11th to 20th	Day	29% 15% 28% 15% 10% 4	452
	21st to end	Day	27% 17% 32% 18% 6% 2	460
May	1st to 10th	Day	27% 18% 24% 19% 8% 3	463
	11th to 20th	Day	23% 11% 30% 24% 9% 3	487
	21st to end	Day	15% 9% 26% 27% 17% 6%	529
June	1st to 10th	Day	15% 10% 31% 28% 11% 4	490
	11th to 20th	Day	17% 10% 26% 27% 17% 4	490
	21st to end	Day	14% 11% 33% 24% 13% 4	490
July	1st to 10th	Day	13% 6% 20% 28% 22% 12%	485
	11th to 20th	Day	11% 8% 25% 29% 18% 8%	484
	21st to end	Day	13% 4 26% 29% 19% 9%	532
August	1st to 10th	Day	13% 7% 21% 30% 19% 10%	486
	11th to 20th	Day	15% 6% 24% 25% 19% 11%	479
	21st to end	Day	10% 5% 23% 29% 21% 11%	539
September	1st to 10th	Day	15% 8% 21% 26% 21% 9%	490
	11th to 20th	Day	10% 4 20% 32% 25% 10%	490
	21st to end	Day	25% 10% 23% 22% 13% 7%	490
October	1st to 10th	Day	13% 11% 26% 26% 19% 6%	490
	11th to 20th	Day	21% 15% 34% 18% 9% 2	490
	21st to end	Day	30% 15% 29% 20% 5%	539
November	1st to 10th	Day	18% 22% 32% 16% 10% 2	352
	11th to 20th	Day	30% 19% 25% 17% 6% 2	231
	21st to end	Day	23% 22% 43% 12% 1	180
December	1st to 10th	Day	33% 24% 26% 11% 3 2	180
	11th to 20th	Day	30% 19% 37% 10% 4	180
	21st to end	Day	37% 21% 27% 12% 2	211
January	1st to 10th	Night	27% 21% 32% 16% 4	760
	11th to 20th	Night	30% 18% 32% 15% 4	760
	21st to end	Night	28% 18% 30% 21% 4	836
February	1st to 10th	Night	29% 16% 31% 22% 2	760
	11th to 20th	Night	27% 16% 36% 19% 2	743
	21st to end	Night	29% 15% 33% 19% 3	628
March	1st to 10th	Night	25% 16% 33% 24% 3	760
	11th to 20th	Night	24% 17% 29% 23% 6% 1	760
	21st to end	Night	25% 14% 32% 24% 5% 1	836
April	1st to 10th	Night	24% 15% 30% 25% 6%	760
	11th to 20th	Night	23% 12% 33% 23% 8% 1	672
	21st to end	Night	20% 9% 35% 29% 6%	570
May	1st to 10th	Night	22% 9% 26% 31% 11% 1	570
	11th to 20th	Night	20% 6% 24% 35% 12% 1	561
	21st to end	Night	11% 3 24% 38% 20% 3	504
June	1st to 10th	Night	11% 3 27% 43% 15% 1	380
	11th to 20th	Night	10% 6% 24% 46% 14% 1	380
	21st to end	Night	11% 4 26% 40% 19% 1	380
July	1st to 10th	Night	7% 4 16% 42% 26% 6%	478
	11th to 20th	Night	11% 3 19% 38% 26% 4	552
	21st to end	Night	12% 1 15% 43% 27% 2	624
August	1st to 10th	Night	11% 3 14% 43% 27% 2	567
	11th to 20th	Night	15% 3 12% 37% 28% 5%	564
	21st to end	Night	13% 2 20% 33% 28% 5%	689
September	1st to 10th	Night	15% 5% 17% 33% 25% 5%	760
	11th to 20th	Night	12% 3 14% 36% 30% 5%	760
	21st to end	Night	20% 8% 22% 27% 19% 4	760
October	1st to 10th	Night	17% 7% 25% 28% 20% 3	760
	11th to 20th	Night	20% 13% 30% 27% 10% 1	760
	21st to end	Night	29% 10% 28% 27% 6%	836
November	1st to 10th	Night	20% 10% 30% 28% 11%	780
	11th to 20th	Night	27% 16% 30% 20% 7% 1	765
	21st to end	Night	29% 16% 28% 22% 5% 1	760
December	1st to 10th	Night	32% 18% 27% 18% 5%	760
	11th to 20th	Night	27% 19% 30% 20% 4	760
	21st to end	Night	31% 16% 31% 20% 2	836

Page generated at 2024-11-08 22:45:39. Version ac07

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