B & P Myers Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the B & P Myers Observatory clear sky chart from 2005-11-06 to 2024-08-30.

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% 12% 4 9% 5% 5% 5% 4 5% 6% 28%	95902
	Night	16% 13% 5% 10% 6% 5% 4 3 5% 6% 27%	93159
Transparency	Day	54% 7% 12% 18% 8% 1	95621
	Night	57% 7% 11% 16% 8% 1	92994
Seeing	Day	26% 16% 27% 19% 8% 2	14403
	Night	24% 15% 27% 25% 8% 1	23509

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	11% 21% 12% 17% 6% 4 3 3 3 4 16%	2517
	11th to 20th	Day	13% 19% 11% 18% 11% 5% 3 2 4 3 11%	2520
	21st to end	Day	15% 23% 9% 14% 7% 7% 4 3 4 3 11%	2973
February	1st to 10th	Day	13% 18% 6% 16% 9% 7% 5% 3 4 4 15%	1710
	11th to 20th	Day	11% 18% 7% 17% 9% 4 3 3 4 4 20%	1720
	21st to end	Day	17% 16% 5% 14% 8% 5% 5% 4 4 5% 18%	1570
March	1st to 10th	Day	20% 18% 5% 12% 5% 4 3 3 3 5% 23%	3116
	11th to 20th	Day	9% 22% 8% 10% 5% 5% 4 3 4 5% 25%	3470
	21st to end	Day	14% 13% 5% 11% 6% 4 3 3 4 5% 32%	4038
April	1st to 10th	Day	19% 16% 4 8% 4 4 3 2 4 5% 31%	2280
	11th to 20th	Day	18% 12% 3 7% 5% 4 4 3 5% 6% 33%	2254
	21st to end	Day	20% 13% 3 8% 4 4 4 3 5% 5% 30%	2298
May	1st to 10th	Day	22% 11% 3 7% 5% 4 4 3 5% 6% 31%	4422
	11th to 20th	Day	18% 9% 3 9% 5% 5% 5% 4 6% 7% 29%	4398
	21st to end	Day	14% 6% 2 6% 4 4 5% 4 7% 8% 38%	4837
June	1st to 10th	Day	20% 8% 2 8% 6% 5% 5% 4 7% 8% 29%	2660
	11th to 20th	Day	18% 7% 2 6% 5% 5% 4 5% 7% 8% 34%	2660
	21st to end	Day	18% 7% 3 7% 6% 5% 6% 4 7% 7% 30%	2660
July	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 10% 35%	4440
	11th to 20th	Day	10% 7% 3 7% 5% 5% 7% 5% 8% 10% 33%	4440
	21st to end	Day	12% 6% 3 7% 6% 6% 6% 5% 7% 8% 33%	4814
August	1st to 10th	Day	15% 6% 2 7% 5% 5% 6% 4 7% 10% 34%	2555
	11th to 20th	Day	15% 7% 3 8% 5% 5% 6% 5% 6% 8% 32%	2348
	21st to end	Day	15% 6% 2 7% 4 5% 5% 5% 7% 9% 35%	2486
September	1st to 10th	Day	16% 6% 2 6% 5% 5% 6% 4 6% 8% 37%	2160
	11th to 20th	Day	16% 7% 2 6% 3 4 4 5% 6% 7% 41%	2146
	21st to end	Day	19% 7% 2 7% 4 5% 4 4 5% 8% 36%	1949
October	1st to 10th	Day	23% 9% 3 8% 6% 4 4 3 4 5% 30%	1800
	11th to 20th	Day	20% 11% 3 8% 4 5% 4 4 6% 7% 27%	1800
	21st to end	Day	26% 14% 4 8% 4 4 6% 4 5% 4 22%	1854
November	1st to 10th	Day	13% 15% 4 11% 6% 5% 5% 3 5% 5% 28%	1671
	11th to 20th	Day	15% 17% 4 10% 5% 5% 4 4 4 7% 25%	1618
	21st to end	Day	17% 21% 6% 11% 6% 4 4 3 5% 5% 19%	1520
December	1st to 10th	Day	18% 25% 8% 12% 5% 4 5% 3 4 4 13%	1520
	11th to 20th	Day	18% 18% 10% 16% 6% 4 3 2 3 4 14%	1906
	21st to end	Day	22% 20% 10% 12% 6% 4 4 2 2 4 13%	2772
January	1st to 10th	Night	15% 21% 9% 16% 6% 5% 4 3 4 4 14%	4429
	11th to 20th	Night	11% 15% 8% 22% 13% 7% 4 3 3 3 11%	4440
	21st to end	Night	16% 18% 7% 16% 8% 6% 5% 3 4 3 13%	4678
February	1st to 10th	Night	12% 16% 7% 16% 9% 7% 5% 3 5% 5% 15%	2470
	11th to 20th	Night	11% 13% 7% 16% 9% 7% 5% 4 5% 5% 19%	2345
	21st to end	Night	15% 13% 5% 12% 7% 5% 5% 5% 5% 6% 21%	1884
March	1st to 10th	Night	17% 15% 5% 12% 7% 4 5% 3 3 4 24%	3724
	11th to 20th	Night	14% 18% 7% 10% 6% 5% 4 3 4 5% 23%	3488
	21st to end	Night	17% 11% 5% 11% 5% 4 4 3 4 4 31%	3594
April	1st to 10th	Night	18% 14% 4 7% 6% 4 4 3 5% 6% 28%	1900
	11th to 20th	Night	18% 12% 3 7% 5% 5% 5% 3 4 6% 32%	1875
	21st to end	Night	17% 11% 2 7% 5% 4 4 3 4 6% 35%	1881
May	1st to 10th	Night	24% 9% 3 7% 5% 4 5% 5% 5% 5% 28%	2546
	11th to 20th	Night	17% 11% 4 8% 4 4 4 4 5% 6% 34%	2495
	21st to end	Night	14% 8% 3 7% 4 4 4 3 6% 8% 40%	2738
June	1st to 10th	Night	16% 6% 2 8% 4 4 5% 4 6% 7% 36%	1520
	11th to 20th	Night	16% 6% 2 5% 5% 4 4 4 5% 7% 41%	1520
	21st to end	Night	17% 7% 2 7% 4 4 4 4 7% 8% 37%	1520
July	1st to 10th	Night	10% 7% 3 8% 6% 5% 5% 4 5% 8% 38%	2520
	11th to 20th	Night	12% 6% 3 7% 5% 5% 4 3 5% 7% 43%	2520
	21st to end	Night	11% 8% 3 6% 4 4 3 3 6% 9% 43%	2739
August	1st to 10th	Night	14% 7% 2 7% 3 4 4 4 6% 7% 43%	1600
	11th to 20th	Night	14% 6% 3 8% 5% 4 4 4 6% 8% 38%	1754
	21st to end	Night	12% 6% 2 5% 4 4 5% 3 7% 7% 45%	2080
September	1st to 10th	Night	14% 7% 3 5% 4 4 5% 4 6% 7% 43%	1800
	11th to 20th	Night	14% 6% 2 7% 3 3 4 3 4 5% 48%	1813
	21st to end	Night	17% 6% 2 7% 4 5% 5% 4 5% 8% 38%	2007
October	1st to 10th	Night	21% 10% 3 8% 5% 5% 4 3 5% 5% 31%	2160
	11th to 20th	Night	20% 10% 3 8% 6% 5% 5% 4 6% 6% 30%	2160
	21st to end	Night	24% 13% 3 9% 5% 5% 4 3 5% 6% 22%	2500
November	1st to 10th	Night	14% 12% 3 9% 7% 4 5% 4 4 5% 32%	2407
	11th to 20th	Night	17% 15% 4 8% 6% 5% 5% 3 4 6% 27%	2560
	21st to end	Night	15% 18% 6% 11% 6% 5% 5% 4 5% 6% 20%	2660
December	1st to 10th	Night	17% 22% 7% 12% 6% 5% 4 3 5% 5% 14%	2660
	11th to 20th	Night	18% 19% 6% 13% 6% 5% 5% 3 4 3 16%	3288
	21st to end	Night	24% 19% 8% 10% 5% 4 3 2 4 5% 14%	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	72% 6% 10% 10% 3	2518
	11th to 20th	Day	76% 8% 7% 6% 3 1	2520
	21st to end	Day	77% 7% 7% 6% 3 1	2973
February	1st to 10th	Day	73% 5% 9% 10% 3 1	1710
	11th to 20th	Day	68% 5% 9% 12% 5% 1	1729
	21st to end	Day	67% 7% 10% 10% 6%	1570
March	1st to 10th	Day	63% 5% 11% 12% 7% 1	3119
	11th to 20th	Day	58% 7% 16% 10% 7% 1	3470
	21st to end	Day	52% 6% 9% 18% 13% 2	4038
April	1st to 10th	Day	56% 5% 8% 19% 11% 2	2280
	11th to 20th	Day	51% 6% 10% 21% 11% 1	2254
	21st to end	Day	55% 6% 9% 16% 11% 3	2298
May	1st to 10th	Day	53% 7% 10% 19% 10% 1	4436
	11th to 20th	Day	50% 9% 12% 22% 7% 1	4402
	21st to end	Day	39% 10% 15% 24% 12% 1	4837
June	1st to 10th	Day	51% 8% 12% 18% 11%	2660
	11th to 20th	Day	45% 8% 13% 23% 9% 1	2660
	21st to end	Day	49% 8% 15% 19% 9% 1	2660
July	1st to 10th	Day	42% 6% 15% 26% 11%	4370
	11th to 20th	Day	43% 6% 15% 28% 8%	4365
	21st to end	Day	45% 7% 15% 23% 10%	4661
August	1st to 10th	Day	42% 9% 16% 22% 11% 1	2541
	11th to 20th	Day	46% 9% 16% 22% 7%	2348
	21st to end	Day	41% 8% 15% 27% 9% 1	2486
September	1st to 10th	Day	42% 8% 13% 24% 12%	2160
	11th to 20th	Day	40% 6% 13% 27% 14% 1	2146
	21st to end	Day	46% 7% 11% 24% 11% 1	1949
October	1st to 10th	Day	55% 6% 11% 18% 9% 1	1800
	11th to 20th	Day	54% 8% 14% 19% 5% 1	1800
	21st to end	Day	63% 8% 11% 10% 7% 1	1854
November	1st to 10th	Day	55% 7% 14% 15% 9%	1671
	11th to 20th	Day	58% 6% 12% 14% 7% 2	1618
	21st to end	Day	66% 7% 14% 10% 4	1520
December	1st to 10th	Day	75% 6% 10% 7% 2	1520
	11th to 20th	Day	75% 6% 8% 8% 3	1906
	21st to end	Day	77% 5% 5% 10% 3	2772
January	1st to 10th	Night	73% 8% 7% 8% 4	4429
	11th to 20th	Night	77% 7% 7% 6% 2 1	4440
	21st to end	Night	75% 6% 7% 8% 3 1	4678
February	1st to 10th	Night	69% 7% 10% 10% 4	2470
	11th to 20th	Night	66% 6% 9% 13% 6%	2347
	21st to end	Night	63% 7% 11% 12% 6%	1884
March	1st to 10th	Night	61% 7% 8% 15% 7% 1	3734
	11th to 20th	Night	61% 6% 13% 14% 4	3489
	21st to end	Night	55% 6% 7% 20% 11% 2	3594
April	1st to 10th	Night	57% 5% 10% 18% 8% 2	1900
	11th to 20th	Night	53% 8% 9% 18% 12% 1	1875
	21st to end	Night	49% 6% 12% 17% 14% 3	1881
May	1st to 10th	Night	55% 8% 10% 14% 11% 2	2552
	11th to 20th	Night	49% 8% 14% 19% 8% 1	2496
	21st to end	Night	41% 9% 12% 20% 17% 1	2739
June	1st to 10th	Night	44% 9% 14% 21% 11% 1	1520
	11th to 20th	Night	40% 8% 15% 22% 13% 2	1520
	21st to end	Night	44% 7% 14% 24% 11% 1	1520
July	1st to 10th	Night	46% 5% 14% 19% 15% 1	2480
	11th to 20th	Night	41% 5% 16% 26% 12%	2472
	21st to end	Night	39% 5% 13% 29% 13% 1	2651
August	1st to 10th	Night	40% 7% 15% 28% 9% 1	1590
	11th to 20th	Night	44% 8% 15% 24% 9%	1754
	21st to end	Night	35% 9% 15% 28% 12%	2080
September	1st to 10th	Night	39% 9% 14% 26% 11% 1	1800
	11th to 20th	Night	39% 6% 11% 27% 16% 1	1813
	21st to end	Night	42% 8% 12% 25% 12% 1	2007
October	1st to 10th	Night	54% 6% 12% 16% 11% 1	2160
	11th to 20th	Night	54% 9% 14% 16% 6% 1	2160
	21st to end	Night	63% 7% 11% 11% 7% 1	2500
November	1st to 10th	Night	52% 7% 13% 16% 9% 2	2407
	11th to 20th	Night	56% 7% 11% 15% 8% 2	2560
	21st to end	Night	64% 8% 12% 13% 3 1	2660
December	1st to 10th	Night	72% 7% 10% 9% 2	2660
	11th to 20th	Night	71% 8% 9% 8% 4	3288
	21st to end	Night	72% 7% 10% 9% 3	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	32% 19% 28% 16% 5%	180
	11th to 20th	Day	34% 28% 28% 8% 1 1	180
	21st to end	Day	24% 25% 35% 13% 3	256
February	1st to 10th	Day	40% 24% 27% 8%	270
	11th to 20th	Day	35% 28% 30% 6%	327
	21st to end	Day	36% 19% 31% 12% 2	382
March	1st to 10th	Day	31% 21% 30% 15% 3	460
	11th to 20th	Day	29% 26% 29% 13% 3	460
	21st to end	Day	34% 24% 25% 12% 4 1	506
April	1st to 10th	Day	38% 19% 24% 14% 4 1	460
	11th to 20th	Day	33% 22% 21% 12% 9% 3	452
	21st to end	Day	32% 20% 27% 14% 5% 2	460
May	1st to 10th	Day	31% 19% 27% 14% 7% 2	463
	11th to 20th	Day	24% 12% 31% 23% 8% 2	487
	21st to end	Day	19% 13% 29% 23% 13% 2	529
June	1st to 10th	Day	23% 17% 29% 22% 8% 2	490
	11th to 20th	Day	20% 12% 29% 26% 10% 3	490
	21st to end	Day	22% 14% 32% 21% 8% 2	490
July	1st to 10th	Day	17% 9% 27% 27% 16% 4	485
	11th to 20th	Day	17% 6% 28% 31% 14% 3	484
	21st to end	Day	15% 8% 33% 30% 11% 2	532
August	1st to 10th	Day	17% 10% 24% 28% 15% 6%	486
	11th to 20th	Day	19% 7% 24% 30% 13% 8%	479
	21st to end	Day	17% 12% 27% 24% 14% 6%	532
September	1st to 10th	Day	17% 10% 26% 22% 17% 8%	450
	11th to 20th	Day	17% 10% 25% 22% 16% 9%	450
	21st to end	Day	20% 10% 29% 23% 13% 4	450
October	1st to 10th	Day	29% 12% 27% 16% 13% 4	450
	11th to 20th	Day	28% 18% 27% 18% 8% 1	450
	21st to end	Day	37% 17% 22% 20% 4	432
November	1st to 10th	Day	27% 20% 21% 23% 9%	365
	11th to 20th	Day	29% 26% 24% 18% 3 1	278
	21st to end	Day	37% 19% 28% 14% 1	180
December	1st to 10th	Day	36% 19% 31% 11% 4	180
	11th to 20th	Day	33% 25% 28% 13% 1	180
	21st to end	Day	37% 22% 30% 11%	198
January	1st to 10th	Night	29% 23% 28% 16% 3	760
	11th to 20th	Night	29% 22% 30% 16% 3	760
	21st to end	Night	19% 23% 35% 20% 3	836
February	1st to 10th	Night	25% 23% 34% 18% 1	760
	11th to 20th	Night	25% 22% 36% 14% 2	743
	21st to end	Night	27% 22% 32% 17% 2	628
March	1st to 10th	Night	26% 20% 32% 21% 2	760
	11th to 20th	Night	29% 19% 30% 18% 3 1	760
	21st to end	Night	25% 20% 30% 18% 6% 1	836
April	1st to 10th	Night	27% 18% 30% 23% 2	760
	11th to 20th	Night	26% 17% 30% 19% 7% 1	751
	21st to end	Night	27% 15% 27% 24% 7%	741
May	1st to 10th	Night	26% 10% 28% 26% 10%	399
	11th to 20th	Night	19% 13% 29% 33% 6% 1	374
	21st to end	Night	15% 7% 27% 37% 12% 1	411
June	1st to 10th	Night	18% 8% 21% 43% 9% 1	380
	11th to 20th	Night	20% 7% 22% 37% 14%	380
	21st to end	Night	18% 6% 25% 39% 11% 1	380
July	1st to 10th	Night	12% 5% 20% 42% 19% 1	370
	11th to 20th	Night	15% 3 18% 42% 21% 1	368
	21st to end	Night	15% 3 20% 44% 16% 1	416
August	1st to 10th	Night	18% 4 19% 38% 20% 1	466
	11th to 20th	Night	19% 4 17% 35% 22% 3	630
	21st to end	Night	14% 6% 19% 39% 20% 1	832
September	1st to 10th	Night	17% 7% 22% 35% 17% 2	720
	11th to 20th	Night	18% 6% 21% 30% 20% 4	720
	21st to end	Night	21% 9% 24% 28% 16% 1	720
October	1st to 10th	Night	28% 12% 23% 21% 15% 1	720
	11th to 20th	Night	28% 14% 24% 27% 7% 1	720
	21st to end	Night	34% 14% 28% 21% 3	792
November	1st to 10th	Night	24% 14% 28% 26% 8%	740
	11th to 20th	Night	28% 18% 27% 21% 5% 1	760
	21st to end	Night	28% 19% 29% 19% 5%	760
December	1st to 10th	Night	32% 21% 29% 15% 3	760
	11th to 20th	Night	32% 20% 28% 16% 3 1	760
	21st to end	Night	33% 22% 28% 16% 1	836

Page generated at 2024-08-27 09:49:41. Version ac07

Copyright © 2024 Attilla Danko.