Banner Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Banner Creek Observatory 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	11% 7% 2 6% 4 4 4 3 5% 7% 46%	101004
	Night	10% 7% 2 6% 3 3 4 3 5% 7% 50%	98259
Transparency	Day	35% 6% 13% 25% 18% 3	104680
	Night	33% 6% 12% 26% 20% 3	102710
Seeing	Day	13% 10% 30% 29% 15% 3	15718
	Night	13% 9% 33% 34% 11% 1	25566

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	12% 11% 4 10% 4 4 3 3 6% 7% 35%	2847
	11th to 20th	Day	9% 12% 4 9% 5% 6% 5% 3 4 4 39%	2850
	21st to end	Day	11% 14% 6% 10% 3 4 4 3 4 5% 36%	3135
February	1st to 10th	Day	11% 12% 3 8% 4 4 4 3 5% 6% 40%	1710
	11th to 20th	Day	9% 9% 3 8% 4 4 4 4 6% 7% 43%	1711
	21st to end	Day	9% 8% 3 8% 4 3 3 3 6% 6% 47%	1575
March	1st to 10th	Day	12% 8% 2 5% 3 3 3 3 4 6% 50%	3436
	11th to 20th	Day	11% 7% 2 5% 3 3 3 4 5% 6% 52%	3480
	21st to end	Day	14% 11% 6% 7% 5% 4 4 3 5% 5% 36%	3814
April	1st to 10th	Day	13% 7% 2 6% 4 3 4 3 4 5% 48%	2143
	11th to 20th	Day	13% 7% 2 7% 6% 4 5% 4 5% 7% 41%	2295
	21st to end	Day	18% 7% 3 5% 4 5% 4 3 6% 6% 38%	2470
May	1st to 10th	Day	17% 8% 3 6% 5% 4 3 3 5% 6% 41%	4082
	11th to 20th	Day	17% 6% 2 7% 4 4 4 3 5% 7% 42%	4082
	21st to end	Day	14% 5% 2 6% 4 4 4 4 5% 7% 45%	4477
June	1st to 10th	Day	6% 4 2 5% 4 4 5% 4 7% 9% 51%	2560
	11th to 20th	Day	7% 5% 2 6% 4 4 5% 5% 6% 9% 48%	2660
	21st to end	Day	7% 4 2 4 4 5% 5% 4 6% 9% 50%	2491
July	1st to 10th	Day	12% 5% 2 5% 4 4 5% 4 7% 8% 44%	4120
	11th to 20th	Day	6% 3 2 5% 4 4 5% 4 7% 9% 51%	4120
	21st to end	Day	6% 4 1 4 4 4 5% 4 7% 10% 51%	4465
August	1st to 10th	Day	6% 4 1 5% 4 4 4 4 6% 8% 53%	4104
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 7% 47%	4041
	21st to end	Day	6% 4 1 5% 3 4 4 4 6% 9% 55%	4381
September	1st to 10th	Day	11% 3 1 4 4 4 4 2 5% 7% 55%	2210
	11th to 20th	Day	8% 4 2 5% 5% 5% 4 3 5% 7% 50%	2090
	21st to end	Day	9% 4 2 4 4 3 4 3 5% 6% 57%	2090
October	1st to 10th	Day	11% 5% 1 4 3 2 3 3 4 7% 55%	1938
	11th to 20th	Day	11% 5% 2 4 2 3 3 3 4 5% 59%	1900
	21st to end	Day	13% 6% 2 5% 3 3 3 3 3 5% 53%	2090
November	1st to 10th	Day	9% 6% 2 4 4 3 3 3 5% 6% 56%	1863
	11th to 20th	Day	11% 8% 2 4 4 2 3 3 3 5% 55%	1719
	21st to end	Day	13% 9% 3 5% 3 2 3 3 5% 6% 50%	1546
December	1st to 10th	Day	9% 7% 3 6% 4 4 4 4 6% 6% 47%	1520
	11th to 20th	Day	9% 10% 3 8% 5% 4 4 3 4 6% 44%	1918
	21st to end	Day	15% 12% 7% 15% 4 4 4 3 5% 6% 26%	3071
January	1st to 10th	Night	8% 8% 4 14% 5% 4 4 3 4 6% 38%	4108
	11th to 20th	Night	9% 9% 4 7% 4 6% 6% 4 4 5% 43%	4120
	21st to end	Night	14% 13% 4 9% 4 3 4 3 4 5% 39%	4532
February	1st to 10th	Night	10% 10% 3 7% 6% 4 4 3 5% 6% 41%	2470
	11th to 20th	Night	10% 8% 2 7% 4 4 4 4 4 7% 45%	2373
	21st to end	Night	10% 8% 2 5% 4 4 3 4 5% 6% 50%	1878
March	1st to 10th	Night	11% 7% 2 5% 3 3 3 3 4 5% 54%	3419
	11th to 20th	Night	10% 5% 2 4 3 3 4 3 5% 6% 55%	3480
	21st to end	Night	17% 10% 3 8% 4 3 3 3 5% 6% 39%	3817
April	1st to 10th	Night	10% 5% 2 5% 5% 3 3 3 6% 6% 52%	2035
	11th to 20th	Night	12% 7% 2 6% 3 4 4 2 6% 5% 47%	1830
	21st to end	Night	16% 6% 2 6% 3 4 4 3 5% 6% 44%	1710
May	1st to 10th	Night	17% 7% 2 4 4 4 4 3 5% 6% 45%	2823
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 5% 8% 46%	2823
	21st to end	Night	12% 5% 2 5% 3 3 3 3 5% 8% 51%	3090
June	1st to 10th	Night	6% 4 2 3 3 3 5% 3 6% 9% 57%	1610
	11th to 20th	Night	6% 4 1 5% 3 4 3 4 6% 11% 53%	1520
	21st to end	Night	4 3 1 4 4 2 4 3 6% 9% 61%	1678
July	1st to 10th	Night	10% 5% 2 6% 4 3 4 3 5% 7% 50%	2850
	11th to 20th	Night	2 2 1 4 3 3 4 4 7% 9% 62%	2850
	21st to end	Night	6% 3 1 4 3 3 4 4 6% 10% 56%	3098
August	1st to 10th	Night	2 2 1 5% 3 3 4 4 6% 10% 59%	2836
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 7% 51%	2798
	21st to end	Night	5% 4 2 5% 3 3 4 3 5% 7% 59%	3280
September	1st to 10th	Night	10% 4 1 4 3 3 3 3 4 6% 59%	1966
	11th to 20th	Night	9% 4 2 4 3 3 4 3 5% 7% 56%	2090
	21st to end	Night	9% 4 2 3 2 3 3 3 4 6% 62%	2090
October	1st to 10th	Night	12% 5% 2 4 3 3 3 2 4 6% 55%	2223
	11th to 20th	Night	12% 4 1 4 3 2 3 2 4 5% 59%	2280
	21st to end	Night	14% 7% 2 3 3 2 3 2 4 5% 55%	2508
November	1st to 10th	Night	8% 5% 1 4 3 3 3 3 5% 6% 60%	2433
	11th to 20th	Night	9% 6% 2 4 3 3 4 4 4 5% 56%	2484
	21st to end	Night	12% 6% 2 5% 3 3 3 3 4 6% 53%	2630
December	1st to 10th	Night	8% 7% 2 5% 4 4 4 4 5% 6% 49%	2660
	11th to 20th	Night	11% 9% 3 7% 3 3 3 3 5% 5% 48%	3279
	21st to end	Night	17% 14% 6% 10% 4 3 3 2 4 5% 33%	4588

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	48% 6% 12% 23% 10% 1	2848
	11th to 20th	Day	49% 4 15% 19% 12% 1	2850
	21st to end	Day	50% 5% 13% 18% 13% 1	3135
February	1st to 10th	Day	45% 6% 14% 21% 10% 3	1710
	11th to 20th	Day	40% 6% 13% 25% 13% 3	1720
	21st to end	Day	37% 5% 12% 24% 18% 4	1575
March	1st to 10th	Day	35% 5% 10% 22% 24% 4	3436
	11th to 20th	Day	32% 6% 11% 27% 22% 2	3480
	21st to end	Day	47% 7% 17% 22% 5% 1	3814
April	1st to 10th	Day	37% 6% 13% 22% 19% 3	2143
	11th to 20th	Day	42% 6% 12% 23% 16% 1	2295
	21st to end	Day	44% 8% 11% 26% 11% 1	2470
May	1st to 10th	Day	43% 7% 11% 23% 14% 2	4120
	11th to 20th	Day	40% 9% 12% 22% 17%	4086
	21st to end	Day	35% 9% 12% 28% 13% 2	4489
June	1st to 10th	Day	28% 9% 16% 29% 17% 2	2560
	11th to 20th	Day	30% 8% 15% 29% 17% 2	2660
	21st to end	Day	28% 8% 17% 27% 16% 4	2491
July	1st to 10th	Day	36% 7% 14% 24% 16% 3	4056
	11th to 20th	Day	27% 7% 13% 33% 17% 3	4051
	21st to end	Day	25% 7% 16% 31% 17% 4	4325
August	1st to 10th	Day	28% 7% 14% 26% 22% 3	4090
	11th to 20th	Day	36% 6% 15% 24% 17% 1	4080
	21st to end	Day	26% 6% 16% 28% 18% 6%	4380
September	1st to 10th	Day	30% 5% 13% 25% 21% 6%	2210
	11th to 20th	Day	32% 8% 11% 25% 21% 3	2090
	21st to end	Day	27% 6% 9% 30% 25% 2	2090
October	1st to 10th	Day	18% 4 8% 20% 43% 7%	3224
	11th to 20th	Day	18% 4 6% 29% 34% 10%	3140
	21st to end	Day	30% 4 10% 27% 25% 4	3428
November	1st to 10th	Day	29% 6% 13% 28% 19% 5%	1863
	11th to 20th	Day	34% 3 9% 28% 23% 3	1719
	21st to end	Day	36% 5% 9% 26% 22% 1	1546
December	1st to 10th	Day	36% 5% 15% 29% 14% 1	1520
	11th to 20th	Day	42% 5% 13% 26% 11% 1	1915
	21st to end	Day	59% 6% 10% 16% 8% 1	3071
January	1st to 10th	Night	45% 7% 13% 21% 12% 1	4108
	11th to 20th	Night	43% 5% 13% 22% 15% 1	4120
	21st to end	Night	48% 5% 15% 19% 12% 2	4532
February	1st to 10th	Night	44% 6% 12% 21% 14% 4	2470
	11th to 20th	Night	39% 6% 12% 24% 16% 4	2374
	21st to end	Night	35% 6% 9% 23% 21% 7%	1878
March	1st to 10th	Night	32% 6% 9% 26% 24% 4	3419
	11th to 20th	Night	30% 6% 9% 26% 25% 5%	3480
	21st to end	Night	44% 8% 17% 23% 7% 1	3817
April	1st to 10th	Night	33% 6% 11% 24% 21% 5%	2035
	11th to 20th	Night	37% 6% 11% 26% 18% 3	1830
	21st to end	Night	39% 6% 13% 24% 16% 1	1710
May	1st to 10th	Night	38% 9% 13% 21% 16% 3	2850
	11th to 20th	Night	37% 6% 13% 25% 19%	2824
	21st to end	Night	31% 7% 13% 29% 18% 1	3099
June	1st to 10th	Night	23% 8% 16% 34% 15% 3	1610
	11th to 20th	Night	25% 8% 14% 31% 18% 4	1520
	21st to end	Night	21% 6% 14% 33% 22% 4	1678
July	1st to 10th	Night	33% 6% 13% 23% 19% 6%	2805
	11th to 20th	Night	17% 6% 13% 36% 25% 3	2796
	21st to end	Night	22% 6% 19% 32% 20% 1	2999
August	1st to 10th	Night	19% 6% 19% 26% 24% 5%	2826
	11th to 20th	Night	34% 5% 14% 26% 20% 1	2825
	21st to end	Night	25% 5% 14% 33% 19% 5%	3280
September	1st to 10th	Night	27% 5% 11% 27% 22% 8%	1966
	11th to 20th	Night	28% 5% 11% 28% 24% 4	2090
	21st to end	Night	25% 5% 9% 26% 31% 4	2090
October	1st to 10th	Night	20% 3 7% 18% 46% 6%	3704
	11th to 20th	Night	19% 3 5% 30% 29% 13%	3779
	21st to end	Night	30% 3 8% 29% 28% 2	4120
November	1st to 10th	Night	26% 4 13% 27% 24% 6%	2433
	11th to 20th	Night	29% 5% 11% 28% 23% 5%	2484
	21st to end	Night	33% 4 11% 28% 21% 3	2630
December	1st to 10th	Night	34% 6% 13% 27% 18% 1	2660
	11th to 20th	Night	37% 5% 11% 31% 15% 1	3281
	21st to end	Night	56% 5% 9% 20% 9% 2	4588

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	18% 17% 35% 21% 9%	270
	11th to 20th	Day	21% 17% 38% 22% 3	270
	21st to end	Day	13% 12% 48% 23% 4	297
February	1st to 10th	Day	19% 20% 43% 15% 4	270
	11th to 20th	Day	16% 17% 47% 13% 7%	270
	21st to end	Day	15% 20% 47% 15% 4	225
March	1st to 10th	Day	16% 17% 43% 20% 4	270
	11th to 20th	Day	25% 17% 34% 19% 5% 1	270
	21st to end	Day	28% 23% 35% 11% 2 1	297
April	1st to 10th	Day	21% 16% 37% 20% 6%	323
	11th to 20th	Day	18% 14% 40% 22% 5% 1	493
	21st to end	Day	20% 18% 33% 18% 9% 1	650
May	1st to 10th	Day	19% 14% 37% 22% 8% 1	653
	11th to 20th	Day	19% 9% 28% 29% 12% 2	675
	21st to end	Day	17% 10% 29% 28% 13% 3	734
June	1st to 10th	Day	5% 4 25% 32% 26% 7%	680
	11th to 20th	Day	6% 4 31% 37% 17% 5%	680
	21st to end	Day	6% 7% 35% 37% 13% 2	680
July	1st to 10th	Day	9% 4 15% 34% 30% 8%	671
	11th to 20th	Day	4 3 19% 41% 26% 7%	668
	21st to end	Day	7% 2 18% 38% 29% 6%	739
August	1st to 10th	Day	7% 3 17% 41% 30% 3	676
	11th to 20th	Day	9% 4 18% 41% 24% 4	665
	21st to end	Day	9% 3 15% 34% 31% 8%	662
September	1st to 10th	Day	10% 2 19% 34% 30% 4	420
	11th to 20th	Day	6% 3 23% 37% 26% 5%	300
	21st to end	Day	13% 7% 29% 33% 15% 3	300
October	1st to 10th	Day	16% 5% 29% 29% 15% 5%	300
	11th to 20th	Day	8% 16% 41% 24% 9% 2	300
	21st to end	Day	17% 16% 38% 20% 8% 2	330
November	1st to 10th	Day	14% 14% 34% 28% 9% 1	300
	11th to 20th	Day	15% 16% 37% 23% 7% 1	273
	21st to end	Day	20% 11% 37% 21% 10%	270
December	1st to 10th	Day	8% 16% 40% 28% 7% 2	270
	11th to 20th	Day	17% 14% 39% 22% 7%	270
	21st to end	Day	20% 19% 42% 18% 2	297
January	1st to 10th	Night	11% 12% 39% 31% 7%	950
	11th to 20th	Night	15% 13% 35% 30% 6%	950
	21st to end	Night	14% 11% 42% 29% 4	1045
February	1st to 10th	Night	15% 13% 41% 27% 3	950
	11th to 20th	Night	14% 13% 39% 30% 4	899
	21st to end	Night	16% 13% 42% 24% 5%	622
March	1st to 10th	Night	13% 13% 42% 27% 5%	570
	11th to 20th	Night	18% 10% 37% 28% 6%	570
	21st to end	Night	25% 11% 38% 21% 4	627
April	1st to 10th	Night	13% 13% 44% 24% 5%	570
	11th to 20th	Night	16% 14% 37% 28% 5%	563
	21st to end	Night	17% 11% 41% 25% 6% 1	570
May	1st to 10th	Night	15% 12% 33% 34% 7% 1	570
	11th to 20th	Night	16% 7% 29% 36% 11%	561
	21st to end	Night	11% 7% 32% 35% 14% 1	617
June	1st to 10th	Night	6% 3 25% 43% 22%	570
	11th to 20th	Night	7% 3 29% 45% 16%	570
	21st to end	Night	5% 5% 32% 45% 12%	570
July	1st to 10th	Night	6% 3 17% 44% 29% 1	555
	11th to 20th	Night	2 1 17% 53% 24% 2	552
	21st to end	Night	6% 1 17% 48% 27% 1	624
August	1st to 10th	Night	4 1 18% 49% 27% 1	567
	11th to 20th	Night	6% 2 15% 49% 25% 3	564
	21st to end	Night	6% 2 17% 42% 31% 2	627
September	1st to 10th	Night	12% 2 21% 42% 20% 3	570
	11th to 20th	Night	10% 3 22% 40% 22% 2	570
	21st to end	Night	10% 4 27% 40% 17% 1	570
October	1st to 10th	Night	14% 6% 29% 33% 17% 1	703
	11th to 20th	Night	14% 8% 41% 29% 8%	760
	21st to end	Night	17% 13% 31% 30% 8%	836
November	1st to 10th	Night	9% 11% 34% 36% 10%	873
	11th to 20th	Night	13% 11% 40% 29% 7%	956
	21st to end	Night	15% 11% 35% 30% 8%	950
December	1st to 10th	Night	13% 12% 37% 31% 6% 1	950
	11th to 20th	Night	17% 10% 38% 30% 5%	950
	21st to end	Night	18% 14% 37% 26% 5%	1045

Page generated at 2024-11-08 21:45:40. Version ac07

Copyright © 2024 Attilla Danko.