Bloomfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bloomfield clear sky chart from 2005-11-06 to 2024-12-24.

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	14% 9% 3 7% 4 4 4 4 6% 8% 38%	101487
	Night	15% 9% 3 7% 4 4 4 3 5% 7% 39%	98672
Transparency	Day	42% 6% 11% 23% 15% 2	105137
	Night	43% 6% 11% 22% 16% 2	103163
Seeing	Day	18% 11% 26% 24% 15% 5%	15695
	Night	19% 9% 27% 29% 14% 2	25557

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	14% 16% 7% 10% 4 4 4 3 5% 6% 27%	2527
	11th to 20th	Day	17% 13% 4 12% 6% 6% 7% 5% 4 4 21%	2530
	21st to end	Day	27% 19% 6% 8% 4 3 2 2 3 4 22%	2979
February	1st to 10th	Day	19% 11% 6% 8% 4 3 4 4 5% 5% 30%	1900
	11th to 20th	Day	17% 11% 4 9% 5% 4 3 3 6% 6% 33%	1848
	21st to end	Day	17% 13% 3 10% 4 3 4 4 4 5% 32%	1570
March	1st to 10th	Day	23% 14% 3 7% 3 3 3 2 4 4 34%	3120
	11th to 20th	Day	14% 7% 3 7% 3 3 3 3 5% 7% 44%	3306
	21st to end	Day	15% 10% 4 8% 5% 5% 5% 4 6% 7% 32%	4084
April	1st to 10th	Day	17% 9% 3 5% 5% 4 4 3 5% 7% 38%	2280
	11th to 20th	Day	18% 9% 3 6% 3 4 3 4 6% 6% 39%	2254
	21st to end	Day	20% 7% 3 7% 5% 4 3 3 4 6% 38%	2380
May	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 5% 7% 9% 28%	4082
	11th to 20th	Day	20% 8% 2 6% 4 4 4 4 5% 7% 37%	4081
	21st to end	Day	12% 7% 2 7% 5% 4 5% 4 7% 8% 38%	4619
June	1st to 10th	Day	11% 7% 2 6% 4 4 4 5% 6% 8% 44%	2660
	11th to 20th	Day	9% 5% 2 5% 4 5% 5% 4 7% 9% 46%	2660
	21st to end	Day	10% 6% 2 5% 5% 5% 5% 4 5% 10% 43%	2660
July	1st to 10th	Day	14% 6% 3 6% 4 5% 4 4 6% 11% 39%	4440
	11th to 20th	Day	7% 4 1 5% 4 4 5% 4 7% 12% 46%	4440
	21st to end	Day	10% 6% 3 7% 6% 6% 7% 6% 8% 10% 30%	4720
August	1st to 10th	Day	7% 5% 2 6% 4 4 4 3 7% 11% 48%	4085
	11th to 20th	Day	9% 5% 2 7% 4 6% 6% 4 7% 10% 40%	3729
	21st to end	Day	5% 4 2 5% 3 3 4 4 6% 9% 54%	4180
September	1st to 10th	Day	12% 6% 2 6% 5% 4 5% 3 5% 7% 46%	2280
	11th to 20th	Day	9% 5% 2 5% 5% 4 4 4 6% 8% 49%	2090
	21st to end	Day	12% 5% 1 5% 4 3 4 3 4 7% 50%	2090
October	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 4 7% 53%	2090
	11th to 20th	Day	15% 7% 2 6% 3 3 4 3 5% 7% 45%	1950
	21st to end	Day	19% 9% 2 5% 4 4 4 3 4 6% 39%	1881
November	1st to 10th	Day	10% 6% 2 6% 4 3 3 3 5% 6% 52%	1762
	11th to 20th	Day	18% 9% 3 6% 4 3 3 3 4 6% 41%	1800
	21st to end	Day	20% 12% 4 5% 3 3 3 3 4 5% 37%	1800
December	1st to 10th	Day	19% 14% 4 8% 5% 4 4 3 4 5% 32%	1800
	11th to 20th	Day	17% 15% 7% 9% 4 3 4 3 4 6% 29%	2003
	21st to end	Day	22% 21% 7% 7% 4 4 4 3 4 4 19%	2807
January	1st to 10th	Night	19% 14% 6% 9% 5% 4 4 4 5% 5% 26%	4428
	11th to 20th	Night	17% 19% 5% 10% 6% 6% 4 3 3 4 23%	4440
	21st to end	Night	27% 18% 5% 7% 4 3 3 3 3 5% 23%	4679
February	1st to 10th	Night	20% 11% 4 8% 5% 5% 4 4 5% 5% 27%	2280
	11th to 20th	Night	15% 11% 3 9% 6% 5% 4 3 4 7% 33%	2218
	21st to end	Night	20% 12% 3 8% 4 4 4 3 5% 5% 32%	1884
March	1st to 10th	Night	23% 14% 3 7% 4 3 3 3 3 5% 32%	3733
	11th to 20th	Night	14% 7% 2 6% 4 3 4 3 4 6% 48%	3654
	21st to end	Night	18% 8% 2 7% 5% 4 4 3 5% 6% 38%	3576
April	1st to 10th	Night	14% 10% 2 7% 4 4 4 3 5% 8% 40%	1900
	11th to 20th	Night	17% 7% 2 6% 4 3 4 3 5% 7% 42%	1875
	21st to end	Night	17% 8% 3 6% 5% 4 5% 4 5% 6% 37%	1799
May	1st to 10th	Night	18% 10% 3 7% 5% 5% 4 4 7% 9% 29%	2813
	11th to 20th	Night	18% 6% 2 5% 3 5% 4 4 6% 7% 40%	2812
	21st to end	Night	11% 5% 2 6% 5% 5% 5% 4 6% 10% 42%	2937
June	1st to 10th	Night	9% 7% 2 6% 4 4 3 4 6% 9% 48%	1520
	11th to 20th	Night	8% 4 1 6% 3 4 5% 4 7% 9% 49%	1520
	21st to end	Night	6% 3 1 5% 4 5% 5% 4 8% 10% 48%	1520
July	1st to 10th	Night	10% 6% 3 7% 4 3 4 3 5% 8% 47%	2530
	11th to 20th	Night	5% 4 1 4 4 4 4 4 6% 8% 54%	2530
	21st to end	Night	9% 7% 3 8% 5% 6% 5% 4 7% 8% 36%	2838
August	1st to 10th	Night	7% 5% 2 6% 3 4 4 3 5% 9% 52%	2841
	11th to 20th	Night	6% 5% 2 6% 5% 4 5% 4 6% 9% 48%	3100
	21st to end	Night	3 3 2 5% 3 4 4 4 6% 9% 57%	3476
September	1st to 10th	Night	9% 6% 2 5% 4 5% 4 4 5% 6% 50%	1900
	11th to 20th	Night	7% 4 2 5% 4 3 4 3 5% 7% 55%	2071
	21st to end	Night	12% 6% 2 5% 3 3 3 4 5% 7% 49%	2090
October	1st to 10th	Night	8% 4 2 4 4 3 3 3 5% 6% 57%	2090
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 5% 6% 49%	2223
	21st to end	Night	18% 8% 2 6% 3 3 3 3 5% 6% 41%	2717
November	1st to 10th	Night	12% 8% 2 6% 4 3 4 3 4 6% 49%	2536
	11th to 20th	Night	14% 9% 3 6% 4 4 3 3 5% 6% 42%	2600
	21st to end	Night	21% 11% 4 6% 4 3 3 3 4 6% 36%	2600
December	1st to 10th	Night	18% 11% 5% 8% 6% 3 3 3 4 7% 32%	2600
	11th to 20th	Night	19% 12% 3 9% 4 3 4 3 5% 4 33%	3409
	21st to end	Night	25% 19% 4 8% 5% 4 3 3 4 4 20%	4933

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	57% 5% 9% 20% 7% 1	2528
	11th to 20th	Day	63% 5% 14% 13% 5%	2530
	21st to end	Day	66% 5% 8% 17% 3 1	2979
February	1st to 10th	Day	55% 5% 9% 20% 9% 2	1900
	11th to 20th	Day	51% 5% 10% 22% 11% 1	1858
	21st to end	Day	53% 4 9% 21% 9% 3	1570
March	1st to 10th	Day	55% 4 6% 19% 12% 3	3120
	11th to 20th	Day	39% 5% 11% 28% 15% 1	3306
	21st to end	Day	47% 9% 12% 22% 9% 1	4084
April	1st to 10th	Day	44% 7% 12% 21% 15% 1	2280
	11th to 20th	Day	44% 5% 10% 24% 13% 3	2254
	21st to end	Day	48% 5% 10% 24% 11% 3	2380
May	1st to 10th	Day	47% 10% 15% 21% 7%	4120
	11th to 20th	Day	46% 8% 10% 25% 11%	4085
	21st to end	Day	39% 9% 13% 19% 18% 3	4632
June	1st to 10th	Day	36% 8% 12% 24% 17% 3	2660
	11th to 20th	Day	32% 8% 14% 23% 20% 4	2660
	21st to end	Day	36% 8% 15% 20% 17% 4	2660
July	1st to 10th	Day	40% 7% 12% 22% 18% 2	4371
	11th to 20th	Day	28% 7% 14% 31% 18% 1	4365
	21st to end	Day	44% 9% 16% 18% 12% 1	4571
August	1st to 10th	Day	30% 6% 15% 33% 16% 1	4072
	11th to 20th	Day	37% 8% 12% 26% 16% 1	3765
	21st to end	Day	25% 6% 16% 33% 16% 4	4179
September	1st to 10th	Day	37% 6% 10% 23% 19% 4	2280
	11th to 20th	Day	32% 6% 12% 27% 20% 3	2090
	21st to end	Day	33% 5% 10% 25% 24% 3	2090
October	1st to 10th	Day	21% 4 6% 28% 39% 2	3480
	11th to 20th	Day	28% 4 8% 27% 31% 2	3218
	21st to end	Day	37% 4 8% 24% 26% 2	3081
November	1st to 10th	Day	33% 4 11% 30% 17% 5%	1762
	11th to 20th	Day	44% 5% 9% 21% 16% 4	1800
	21st to end	Day	49% 4 9% 22% 15% 1	1800
December	1st to 10th	Day	55% 4 11% 19% 10% 1	1800
	11th to 20th	Day	57% 5% 8% 22% 8% 1	2000
	21st to end	Day	67% 5% 10% 12% 6%	2807
January	1st to 10th	Night	57% 7% 12% 17% 7%	4428
	11th to 20th	Night	65% 4 10% 13% 7%	4440
	21st to end	Night	65% 4 8% 16% 8% 1	4679
February	1st to 10th	Night	57% 5% 12% 17% 7% 1	2280
	11th to 20th	Night	52% 3 11% 20% 13% 1	2219
	21st to end	Night	54% 5% 10% 18% 10% 2	1884
March	1st to 10th	Night	55% 5% 7% 21% 12% 1	3733
	11th to 20th	Night	36% 7% 11% 23% 22% 1	3654
	21st to end	Night	46% 6% 11% 26% 9% 1	3576
April	1st to 10th	Night	42% 5% 10% 26% 14% 2	1900
	11th to 20th	Night	42% 4 10% 20% 19% 5%	1875
	21st to end	Night	46% 6% 10% 22% 13% 3	1799
May	1st to 10th	Night	48% 12% 13% 20% 7% 1	2840
	11th to 20th	Night	41% 8% 14% 25% 11% 1	2813
	21st to end	Night	35% 10% 14% 21% 16% 4	2945
June	1st to 10th	Night	33% 7% 10% 25% 21% 4	1520
	11th to 20th	Night	30% 8% 11% 23% 21% 7%	1520
	21st to end	Night	27% 10% 14% 23% 20% 6%	1520
July	1st to 10th	Night	36% 7% 8% 25% 20% 3	2490
	11th to 20th	Night	25% 7% 13% 32% 21% 2	2482
	21st to end	Night	42% 7% 15% 21% 13% 2	2748
August	1st to 10th	Night	28% 8% 14% 37% 12% 2	2830
	11th to 20th	Night	31% 7% 15% 28% 18% 1	3130
	21st to end	Night	23% 7% 14% 29% 23% 4	3476
September	1st to 10th	Night	32% 7% 10% 25% 20% 6%	1900
	11th to 20th	Night	28% 5% 11% 25% 27% 5%	2071
	21st to end	Night	33% 7% 10% 22% 23% 5%	2090
October	1st to 10th	Night	18% 4 8% 19% 47% 4	3480
	11th to 20th	Night	25% 3 7% 26% 36% 3	3694
	21st to end	Night	34% 4 7% 23% 26% 6%	4467
November	1st to 10th	Night	36% 4 9% 25% 21% 5%	2536
	11th to 20th	Night	41% 4 10% 22% 19% 4	2600
	21st to end	Night	50% 4 10% 22% 13% 1	2600
December	1st to 10th	Night	53% 4 11% 20% 12% 1	2600
	11th to 20th	Night	53% 5% 11% 19% 12% 1	3411
	21st to end	Night	67% 5% 8% 11% 7% 1	4933

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	27% 22% 26% 19% 5%	270
	11th to 20th	Day	31% 21% 32% 14% 1	270
	21st to end	Day	32% 21% 31% 12% 4	297
February	1st to 10th	Day	27% 24% 34% 13% 1	270
	11th to 20th	Day	25% 26% 33% 13% 2 1	270
	21st to end	Day	32% 20% 35% 11% 2	225
March	1st to 10th	Day	24% 26% 34% 14% 3	270
	11th to 20th	Day	28% 21% 34% 13% 4 1	351
	21st to end	Day	29% 19% 31% 16% 5%	506
April	1st to 10th	Day	22% 20% 30% 21% 6% 1	460
	11th to 20th	Day	23% 21% 23% 21% 10% 2	452
	21st to end	Day	24% 21% 31% 15% 8% 1	460
May	1st to 10th	Day	21% 15% 29% 25% 7% 3	463
	11th to 20th	Day	22% 8% 26% 26% 13% 5%	487
	21st to end	Day	13% 6% 28% 25% 18% 9%	607
June	1st to 10th	Day	13% 5% 26% 29% 21% 5%	680
	11th to 20th	Day	10% 6% 25% 33% 21% 5%	680
	21st to end	Day	13% 6% 29% 27% 19% 7%	680
July	1st to 10th	Day	12% 4 17% 27% 25% 15%	671
	11th to 20th	Day	8% 4 20% 33% 23% 11%	668
	21st to end	Day	11% 2 19% 30% 30% 7%	682
August	1st to 10th	Day	10% 3 16% 29% 28% 13%	486
	11th to 20th	Day	13% 3 19% 29% 29% 6%	479
	21st to end	Day	8% 1 14% 31% 32% 14%	539
September	1st to 10th	Day	11% 4 16% 31% 29% 8%	490
	11th to 20th	Day	9% 2 14% 33% 31% 11%	490
	21st to end	Day	17% 8% 21% 25% 21% 8%	490
October	1st to 10th	Day	10% 5% 29% 31% 20% 5%	490
	11th to 20th	Day	16% 13% 36% 21% 10% 4	376
	21st to end	Day	28% 16% 35% 19% 2	330
November	1st to 10th	Day	12% 18% 34% 25% 8% 3	300
	11th to 20th	Day	23% 19% 31% 19% 6% 2	300
	21st to end	Day	32% 9% 33% 20% 6%	300
December	1st to 10th	Day	23% 22% 34% 14% 6% 1	300
	11th to 20th	Day	27% 18% 33% 17% 4 1	300
	21st to end	Day	32% 18% 32% 14% 2 1	306
January	1st to 10th	Night	23% 16% 34% 23% 4	950
	11th to 20th	Night	28% 16% 33% 19% 3	950
	21st to end	Night	23% 16% 35% 24% 2	998
February	1st to 10th	Night	26% 12% 37% 23% 2	760
	11th to 20th	Night	23% 15% 38% 22% 2	743
	21st to end	Night	28% 15% 36% 20% 1	628
March	1st to 10th	Night	27% 15% 30% 24% 3	760
	11th to 20th	Night	23% 13% 35% 22% 6% 1	760
	21st to end	Night	25% 11% 32% 27% 5%	698
April	1st to 10th	Night	19% 14% 31% 29% 6% 1	570
	11th to 20th	Night	20% 12% 30% 28% 10% 1	563
	21st to end	Night	19% 9% 35% 28% 7% 1	570
May	1st to 10th	Night	19% 8% 32% 30% 11%	570
	11th to 20th	Night	19% 4 24% 34% 17% 2	561
	21st to end	Night	12% 3 21% 36% 24% 4	617
June	1st to 10th	Night	11% 3 20% 41% 23% 1	570
	11th to 20th	Night	10% 3 19% 44% 23% 1	570
	21st to end	Night	8% 3 22% 38% 28% 1	570
July	1st to 10th	Night	10% 1 12% 34% 33% 9%	555
	11th to 20th	Night	7% 3 13% 39% 34% 5%	552
	21st to end	Night	9% 2 14% 37% 34% 4	624
August	1st to 10th	Night	8% 2 9% 39% 36% 5%	567
	11th to 20th	Night	7% 2 11% 40% 36% 4	564
	21st to end	Night	6% 2 12% 35% 40% 5%	627
September	1st to 10th	Night	12% 3 12% 36% 32% 4	570
	11th to 20th	Night	9% 3 14% 35% 33% 6%	741
	21st to end	Night	14% 7% 20% 31% 24% 4	760
October	1st to 10th	Night	10% 4 22% 38% 23% 4	760
	11th to 20th	Night	18% 9% 29% 27% 16% 1	760
	21st to end	Night	22% 11% 33% 25% 8%	836
November	1st to 10th	Night	15% 8% 34% 30% 11% 1	780
	11th to 20th	Night	19% 15% 29% 28% 9%	800
	21st to end	Night	27% 15% 26% 24% 8%	800
December	1st to 10th	Night	25% 11% 36% 23% 5%	800
	11th to 20th	Night	27% 10% 32% 25% 5% 1	990
	21st to end	Night	31% 15% 32% 19% 3	1063

Page generated at 2024-12-21 04:13:49. Version ac07

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