This page made possible by the sponsorship of: .

Beckstrom Observatory
Clear Sky Chart
History

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

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	13% 10% 4 8% 5% 5% 5% 4 6% 7% 33%	101108
	Night	14% 11% 4 8% 5% 5% 4 3 5% 6% 34%	97910
Transparency	Day	48% 7% 12% 20% 12% 1	104707
	Night	48% 6% 12% 21% 11% 1	102451
Seeing	Day	17% 15% 30% 22% 11% 4	15407
	Night	19% 12% 31% 27% 10% 1	24927

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	15% 19% 10% 13% 6% 4 4 3 3 4 19%	2527
	11th to 20th	Day	14% 20% 9% 15% 9% 9% 4 3 3 5% 10%	2530
	21st to end	Day	24% 20% 6% 10% 6% 4 3 3 4 5% 15%	3005
February	1st to 10th	Day	12% 17% 5% 13% 7% 5% 5% 3 5% 6% 22%	1710
	11th to 20th	Day	12% 15% 5% 12% 8% 6% 4 3 4 5% 26%	1757
	21st to end	Day	14% 16% 4 11% 6% 4 4 3 5% 5% 28%	1570
March	1st to 10th	Day	16% 15% 5% 9% 5% 5% 4 3 4 6% 28%	3206
	11th to 20th	Day	12% 14% 7% 10% 5% 4 5% 3 5% 7% 28%	3480
	21st to end	Day	17% 13% 5% 10% 6% 4 5% 3 5% 6% 27%	3815
April	1st to 10th	Day	15% 14% 4 9% 5% 4 4 3 5% 6% 30%	2204
	11th to 20th	Day	16% 10% 3 7% 5% 4 4 4 5% 7% 36%	2433
	21st to end	Day	16% 9% 3 8% 5% 5% 4 4 5% 6% 35%	2470
May	1st to 10th	Day	15% 8% 3 7% 4 4 5% 3 6% 7% 37%	4082
	11th to 20th	Day	16% 8% 3 7% 4 5% 5% 4 6% 8% 34%	4081
	21st to end	Day	10% 7% 2 6% 5% 4 4 3 5% 7% 48%	4635
June	1st to 10th	Day	11% 7% 2 7% 4 5% 4 4 6% 9% 40%	2850
	11th to 20th	Day	10% 6% 2 7% 4 5% 5% 4 6% 8% 42%	2850
	21st to end	Day	11% 6% 2 6% 5% 4 5% 4 8% 9% 40%	2850
July	1st to 10th	Day	10% 6% 3 8% 5% 6% 6% 5% 7% 8% 36%	4490
	11th to 20th	Day	8% 5% 2 6% 4 5% 5% 4 7% 9% 46%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 5% 4 8% 10% 41%	4602
August	1st to 10th	Day	11% 5% 2 6% 6% 6% 5% 5% 7% 8% 38%	4104
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 4 7% 9% 39%	4044
	21st to end	Day	10% 6% 3 7% 4 5% 5% 5% 6% 9% 41%	4532
September	1st to 10th	Day	11% 6% 3 8% 5% 5% 6% 5% 6% 8% 39%	2161
	11th to 20th	Day	12% 5% 2 6% 4 3 4 4 6% 8% 46%	2090
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 6% 9% 34%	2090
October	1st to 10th	Day	15% 8% 2 6% 6% 4 4 3 5% 6% 40%	2018
	11th to 20th	Day	20% 11% 3 8% 5% 4 4 4 6% 7% 29%	1900
	21st to end	Day	22% 12% 3 9% 4 4 5% 3 5% 8% 25%	1929
November	1st to 10th	Day	13% 13% 3 9% 6% 4 4 3 6% 6% 33%	1717
	11th to 20th	Day	14% 15% 5% 9% 6% 5% 4 4 6% 6% 27%	1688
	21st to end	Day	17% 15% 6% 12% 5% 5% 4 4 5% 5% 22%	1520
December	1st to 10th	Day	13% 18% 7% 15% 6% 5% 5% 3 4 4 19%	1520
	11th to 20th	Day	16% 16% 5% 11% 6% 5% 3 4 5% 5% 24%	1699
	21st to end	Day	26% 22% 8% 10% 5% 4 5% 3 4 5% 10%	2509
January	1st to 10th	Night	16% 14% 6% 12% 5% 5% 4 3 5% 6% 23%	4428
	11th to 20th	Night	13% 16% 7% 16% 8% 10% 4 3 4 4 13%	4440
	21st to end	Night	18% 17% 9% 11% 6% 4 4 3 4 5% 19%	4652
February	1st to 10th	Night	14% 17% 4 11% 6% 5% 5% 4 5% 6% 23%	2470
	11th to 20th	Night	13% 14% 5% 10% 6% 5% 5% 4 6% 5% 27%	2307
	21st to end	Night	16% 12% 4 10% 6% 5% 5% 4 5% 5% 26%	1884
March	1st to 10th	Night	13% 13% 4 7% 4 4 3 3 4 6% 39%	3647
	11th to 20th	Night	8% 8% 4 8% 5% 4 5% 4 6% 8% 39%	3480
	21st to end	Night	15% 11% 4 9% 5% 5% 5% 3 4 6% 33%	3817
April	1st to 10th	Night	18% 12% 4 7% 5% 3 4 3 5% 7% 33%	1990
	11th to 20th	Night	18% 8% 2 6% 5% 4 4 4 5% 7% 37%	1695
	21st to end	Night	17% 10% 3 8% 4 5% 4 3 5% 6% 36%	1710
May	1st to 10th	Night	13% 10% 3 6% 6% 5% 4 4 5% 7% 38%	2813
	11th to 20th	Night	13% 9% 3 8% 4 4 4 3 5% 7% 40%	2812
	21st to end	Night	10% 6% 2 5% 4 4 4 3 5% 7% 49%	2888
June	1st to 10th	Night	12% 6% 3 6% 6% 5% 5% 4 6% 6% 44%	1330
	11th to 20th	Night	10% 6% 2 5% 5% 3 4 4 6% 10% 44%	1330
	21st to end	Night	8% 5% 2 6% 4 5% 5% 4 6% 8% 47%	1330
July	1st to 10th	Night	7% 6% 3 6% 5% 4 4 4 5% 9% 46%	2461
	11th to 20th	Night	9% 4 2 4 3 4 4 3 6% 8% 53%	2530
	21st to end	Night	5% 4 2 6% 4 6% 5% 5% 7% 8% 48%	2955
August	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 5% 7% 47%	2825
	11th to 20th	Night	11% 6% 2 6% 4 4 5% 4 5% 8% 47%	2785
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 6% 8% 47%	3124
September	1st to 10th	Night	9% 5% 2 7% 4 5% 5% 4 6% 6% 47%	1996
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 4 7% 54%	2090
	21st to end	Night	14% 8% 3 7% 4 4 4 3 5% 7% 42%	2090
October	1st to 10th	Night	15% 7% 3 6% 3 3 3 3 5% 7% 44%	2161
	11th to 20th	Night	19% 11% 3 8% 4 3 5% 3 5% 6% 33%	2280
	21st to end	Night	21% 10% 4 9% 4 5% 4 3 5% 7% 29%	2665
November	1st to 10th	Night	13% 10% 4 7% 4 4 4 4 6% 6% 39%	2483
	11th to 20th	Night	14% 12% 4 9% 6% 6% 6% 4 6% 7% 26%	2489
	21st to end	Night	19% 15% 4 8% 5% 4 4 3 5% 7% 25%	2660
December	1st to 10th	Night	18% 16% 5% 10% 6% 5% 5% 4 6% 5% 20%	2660
	11th to 20th	Night	14% 14% 6% 12% 7% 5% 4 5% 5% 5% 22%	3493
	21st to end	Night	25% 23% 7% 10% 5% 4 4 2 4 4 13%	5140

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	67% 7% 10% 11% 4	2528
	11th to 20th	Day	77% 6% 7% 7% 2	2530
	21st to end	Day	72% 6% 11% 7% 3	3005
February	1st to 10th	Day	63% 6% 11% 15% 5%	1710
	11th to 20th	Day	61% 5% 10% 15% 9% 1	1766
	21st to end	Day	59% 5% 11% 16% 7% 1	1570
March	1st to 10th	Day	57% 5% 13% 19% 5% 1	3206
	11th to 20th	Day	55% 5% 13% 17% 9% 2	3480
	21st to end	Day	57% 6% 12% 15% 9% 2	3815
April	1st to 10th	Day	55% 5% 11% 18% 10% 1	2204
	11th to 20th	Day	48% 6% 12% 19% 13% 2	2433
	21st to end	Day	49% 7% 12% 18% 12% 1	2470
May	1st to 10th	Day	45% 6% 12% 19% 14% 2	4120
	11th to 20th	Day	44% 8% 14% 22% 10% 1	4085
	21st to end	Day	35% 7% 10% 19% 23% 6%	4649
June	1st to 10th	Day	39% 7% 12% 25% 15% 2	2850
	11th to 20th	Day	38% 7% 12% 23% 18% 2	2850
	21st to end	Day	39% 8% 12% 24% 15% 1	2850
July	1st to 10th	Day	43% 8% 12% 19% 15% 3	4421
	11th to 20th	Day	31% 8% 13% 33% 15% 1	4365
	21st to end	Day	36% 9% 14% 18% 21% 2	4456
August	1st to 10th	Day	39% 9% 13% 21% 16% 1	4091
	11th to 20th	Day	38% 8% 14% 28% 11% 1	4083
	21st to end	Day	38% 8% 13% 27% 14% 1	4531
September	1st to 10th	Day	40% 9% 13% 25% 12% 2	2161
	11th to 20th	Day	35% 8% 12% 30% 14% 1	2090
	21st to end	Day	47% 7% 13% 22% 11%	2090
October	1st to 10th	Day	34% 5% 10% 33% 16% 3	3356
	11th to 20th	Day	42% 6% 14% 24% 14%	3140
	21st to end	Day	51% 5% 13% 22% 8%	3153
November	1st to 10th	Day	50% 7% 12% 21% 9%	1717
	11th to 20th	Day	56% 6% 14% 15% 9%	1688
	21st to end	Day	62% 6% 15% 13% 4 1	1520
December	1st to 10th	Day	68% 7% 12% 10% 3	1520
	11th to 20th	Day	61% 6% 14% 16% 4	1695
	21st to end	Day	78% 6% 8% 6% 3	2509
January	1st to 10th	Night	60% 7% 13% 13% 6% 1	4428
	11th to 20th	Night	73% 7% 8% 9% 3	4440
	21st to end	Night	68% 6% 10% 13% 3	4652
February	1st to 10th	Night	60% 6% 11% 16% 7% 1	2470
	11th to 20th	Night	56% 6% 11% 17% 9% 1	2309
	21st to end	Night	59% 5% 10% 17% 8%	1884
March	1st to 10th	Night	46% 5% 15% 26% 7% 1	3647
	11th to 20th	Night	39% 6% 18% 22% 14% 1	3480
	21st to end	Night	51% 6% 13% 20% 9% 1	3817
April	1st to 10th	Night	50% 5% 10% 21% 12% 2	1990
	11th to 20th	Night	45% 6% 11% 19% 18% 2	1695
	21st to end	Night	48% 6% 10% 19% 15% 3	1710
May	1st to 10th	Night	43% 7% 11% 20% 14% 5%	2840
	11th to 20th	Night	42% 5% 12% 26% 12% 3	2813
	21st to end	Night	34% 7% 11% 22% 20% 6%	2895
June	1st to 10th	Night	38% 7% 10% 25% 18% 2	1330
	11th to 20th	Night	35% 7% 14% 22% 20% 3	1330
	21st to end	Night	34% 7% 13% 27% 17% 2	1330
July	1st to 10th	Night	35% 6% 13% 24% 15% 7%	2421
	11th to 20th	Night	27% 7% 12% 35% 17% 1	2482
	21st to end	Night	31% 9% 17% 21% 20% 2	2861
August	1st to 10th	Night	35% 7% 13% 29% 16% 1	2814
	11th to 20th	Night	34% 7% 14% 30% 13% 2	2812
	21st to end	Night	32% 9% 13% 31% 14% 1	3124
September	1st to 10th	Night	34% 9% 13% 28% 15% 1	1996
	11th to 20th	Night	29% 6% 12% 34% 18% 1	2090
	21st to end	Night	42% 7% 11% 28% 12% 1	2090
October	1st to 10th	Night	27% 5% 12% 31% 23% 1	3603
	11th to 20th	Night	44% 6% 11% 25% 15% 1	3779
	21st to end	Night	46% 5% 12% 27% 10% 1	4391
November	1st to 10th	Night	44% 6% 13% 25% 11% 1	2483
	11th to 20th	Night	55% 7% 13% 17% 7% 1	2489
	21st to end	Night	59% 6% 15% 15% 4 1	2660
December	1st to 10th	Night	64% 7% 12% 13% 4	2660
	11th to 20th	Night	61% 6% 14% 13% 5%	3496
	21st to end	Night	75% 6% 10% 6% 3	5140

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	24% 24% 34% 13% 4	270
	11th to 20th	Day	22% 21% 39% 15% 3	270
	21st to end	Day	26% 19% 34% 16% 3 1	297
February	1st to 10th	Day	21% 28% 36% 11% 3 1	270
	11th to 20th	Day	21% 28% 37% 13% 1	270
	21st to end	Day	25% 32% 31% 11% 2	225
March	1st to 10th	Day	28% 23% 31% 15% 3	317
	11th to 20th	Day	22% 17% 33% 21% 6% 1	460
	21st to end	Day	28% 17% 31% 19% 5% 1	506
April	1st to 10th	Day	21% 22% 32% 17% 6% 1	460
	11th to 20th	Day	26% 21% 26% 16% 7% 4	452
	21st to end	Day	21% 18% 33% 18% 8% 2	460
May	1st to 10th	Day	22% 18% 27% 23% 8% 2	463
	11th to 20th	Day	17% 13% 33% 21% 11% 4	487
	21st to end	Day	12% 11% 30% 27% 15% 5%	567
June	1st to 10th	Day	12% 13% 33% 29% 10% 3	680
	11th to 20th	Day	13% 11% 34% 27% 12% 3	680
	21st to end	Day	14% 10% 33% 28% 12% 4	680
July	1st to 10th	Day	9% 7% 28% 31% 17% 8%	671
	11th to 20th	Day	10% 9% 30% 30% 14% 7%	668
	21st to end	Day	8% 6% 29% 33% 17% 6%	616
August	1st to 10th	Day	10% 7% 23% 28% 21% 11%	486
	11th to 20th	Day	12% 5% 21% 29% 22% 12%	479
	21st to end	Day	12% 9% 21% 29% 22% 7%	539
September	1st to 10th	Day	13% 9% 27% 25% 18% 9%	490
	11th to 20th	Day	11% 7% 20% 26% 24% 12%	490
	21st to end	Day	17% 16% 22% 23% 16% 7%	490
October	1st to 10th	Day	19% 16% 25% 21% 15% 5%	490
	11th to 20th	Day	20% 20% 31% 22% 5% 1	490
	21st to end	Day	28% 19% 34% 14% 4 1	378
November	1st to 10th	Day	18% 25% 33% 17% 7%	285
	11th to 20th	Day	22% 24% 35% 14% 5%	259
	21st to end	Day	22% 21% 39% 14% 4	180
December	1st to 10th	Day	24% 25% 31% 16% 3 1	180
	11th to 20th	Day	28% 24% 37% 8% 2 1	180
	21st to end	Day	28% 24% 36% 9% 2	222
January	1st to 10th	Night	21% 20% 35% 19% 5% 1	950
	11th to 20th	Night	23% 18% 34% 19% 4 1	950
	21st to end	Night	19% 13% 37% 25% 6%	904
February	1st to 10th	Night	22% 17% 38% 20% 3	760
	11th to 20th	Night	22% 18% 33% 22% 5%	743
	21st to end	Night	22% 21% 34% 19% 3	628
March	1st to 10th	Night	20% 15% 35% 24% 6%	760
	11th to 20th	Night	16% 16% 38% 24% 5% 1	760
	21st to end	Night	22% 14% 31% 25% 7%	836
April	1st to 10th	Night	23% 16% 34% 22% 5%	660
	11th to 20th	Night	22% 14% 34% 22% 7% 2	563
	21st to end	Night	21% 11% 31% 29% 7%	570
May	1st to 10th	Night	17% 7% 34% 32% 9% 1	570
	11th to 20th	Night	19% 9% 29% 33% 10% 1	561
	21st to end	Night	13% 6% 29% 34% 16% 2	556
June	1st to 10th	Night	12% 7% 32% 38% 11%	380
	11th to 20th	Night	13% 5% 33% 38% 10%	380
	21st to end	Night	11% 6% 29% 40% 15%	380
July	1st to 10th	Night	8% 3 19% 43% 25% 2	512
	11th to 20th	Night	10% 3 22% 41% 21% 3	552
	21st to end	Night	7% 2 26% 43% 21% 1	624
August	1st to 10th	Night	10% 2 16% 45% 26% 2	567
	11th to 20th	Night	8% 4 21% 36% 28% 4	564
	21st to end	Night	11% 4 24% 34% 24% 3	627
September	1st to 10th	Night	11% 4 28% 32% 20% 5%	684
	11th to 20th	Night	12% 5% 19% 36% 25% 4	760
	21st to end	Night	17% 8% 24% 31% 16% 4	760
October	1st to 10th	Night	18% 10% 29% 27% 16% 1	760
	11th to 20th	Night	22% 15% 31% 24% 7% 1	760
	21st to end	Night	26% 13% 34% 22% 5%	836
November	1st to 10th	Night	20% 14% 31% 25% 10% 1	764
	11th to 20th	Night	21% 19% 34% 19% 7% 1	760
	21st to end	Night	26% 16% 36% 19% 4	760
December	1st to 10th	Night	26% 18% 34% 18% 4 1	760
	11th to 20th	Night	22% 19% 37% 19% 2 1	921
	21st to end	Night	30% 15% 35% 18% 2	1045

Page generated at 2024-11-03 13:19:00. Version ac07

Copyright © 2024 Attilla Danko.