The BD Software Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The BD Software Observatory clear sky chart from 2005-11-06 to 2024-06-30.

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	18% 7% 2 6% 4 4 4 3 5% 7% 39%	89293
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 39%	89859
Transparency	Day	46% 3 11% 23% 15% 2	89012
	Night	47% 2 10% 23% 15% 2	89694
Seeing	Day	23% 16% 33% 20% 7% 2	14559
	Night	22% 13% 32% 24% 8% 1	23482

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	15% 7% 2 7% 3 3 4 3 4 6% 45%	2517
	11th to 20th	Day	17% 6% 3 8% 4 3 4 3 5% 6% 42%	2520
	21st to end	Day	20% 11% 3 7% 4 4 4 3 4 5% 35%	2772
February	1st to 10th	Day	19% 7% 3 6% 4 4 4 5% 6% 6% 36%	1761
	11th to 20th	Day	14% 8% 2 6% 4 5% 5% 4 5% 7% 39%	1848
	21st to end	Day	17% 10% 3 6% 4 5% 4 4 4 6% 36%	1570
March	1st to 10th	Day	26% 13% 3 6% 4 4 3 3 4 5% 30%	3116
	11th to 20th	Day	14% 7% 2 6% 4 4 4 4 6% 7% 40%	3350
	21st to end	Day	24% 10% 2 6% 4 3 4 4 6% 6% 33%	3999
April	1st to 10th	Day	19% 10% 3 7% 4 4 4 3 5% 6% 37%	2280
	11th to 20th	Day	18% 7% 2 5% 5% 4 5% 4 6% 7% 38%	2283
	21st to end	Day	20% 7% 3 6% 5% 4 4 3 5% 7% 36%	2470
May	1st to 10th	Day	22% 12% 3 9% 5% 4 4 3 5% 6% 28%	4106
	11th to 20th	Day	22% 9% 3 8% 5% 4 4 3 5% 6% 32%	4134
	21st to end	Day	14% 5% 2 5% 4 4 4 3 5% 8% 45%	4837
June	1st to 10th	Day	20% 6% 2 5% 4 6% 5% 4 6% 7% 35%	2660
	11th to 20th	Day	16% 6% 2 5% 5% 4 4 4 6% 8% 39%	2660
	21st to end	Day	18% 5% 2 6% 5% 5% 4 4 6% 9% 35%	2646
July	1st to 10th	Day	14% 6% 2 5% 5% 4 5% 4 6% 8% 41%	2520
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 4 7% 10% 40%	2520
	21st to end	Day	12% 4 2 6% 5% 5% 5% 5% 8% 9% 39%	2744
August	1st to 10th	Day	10% 5% 3 7% 5% 5% 7% 5% 7% 9% 38%	2347
	11th to 20th	Day	13% 6% 2 6% 4 4 6% 4 7% 8% 40%	2300
	21st to end	Day	12% 5% 1 5% 4 3 5% 4 6% 8% 46%	2376
September	1st to 10th	Day	14% 6% 2 5% 3 4 4 4 5% 7% 46%	2147
	11th to 20th	Day	15% 6% 2 4 4 2 3 2 4 6% 51%	1980
	21st to end	Day	17% 6% 2 5% 4 4 3 2 6% 6% 46%	1980
October	1st to 10th	Day	24% 5% 2 6% 3 4 3 3 5% 6% 40%	1980
	11th to 20th	Day	15% 6% 2 5% 3 4 4 3 5% 7% 46%	1759
	21st to end	Day	21% 6% 2 6% 4 4 4 3 5% 6% 39%	1782
November	1st to 10th	Day	16% 7% 2 5% 4 3 3 3 4 4 49%	1671
	11th to 20th	Day	19% 6% 2 5% 3 3 4 3 4 5% 46%	1710
	21st to end	Day	18% 7% 2 5% 3 4 4 3 4 6% 43%	1710
December	1st to 10th	Day	19% 7% 3 6% 4 4 4 3 5% 6% 40%	1560
	11th to 20th	Day	22% 7% 2 4 4 3 3 3 4 5% 44%	1906
	21st to end	Day	22% 10% 3 6% 5% 4 4 3 5% 6% 34%	2772
January	1st to 10th	Night	18% 7% 2 4 3 3 3 3 4 6% 46%	4429
	11th to 20th	Night	15% 8% 3 9% 5% 4 4 3 4 5% 40%	4440
	21st to end	Night	21% 13% 3 8% 5% 4 4 3 4 5% 30%	4884
February	1st to 10th	Night	16% 10% 3 6% 4 4 4 4 5% 6% 38%	2415
	11th to 20th	Night	14% 10% 3 6% 4 5% 3 4 5% 6% 40%	2218
	21st to end	Night	19% 8% 2 5% 4 3 3 4 4 6% 42%	1884
March	1st to 10th	Night	29% 10% 2 5% 3 3 3 3 4 5% 32%	3724
	11th to 20th	Night	12% 9% 3 8% 4 5% 5% 4 5% 6% 38%	3608
	21st to end	Night	25% 8% 3 6% 4 4 4 4 5% 4 33%	3630
April	1st to 10th	Night	20% 8% 2 6% 5% 5% 5% 4 5% 6% 35%	1900
	11th to 20th	Night	20% 8% 2 5% 4 4 4 3 4 7% 40%	1845
	21st to end	Night	21% 6% 2 6% 4 4 3 3 5% 6% 38%	1710
May	1st to 10th	Night	24% 12% 3 7% 5% 5% 4 3 5% 6% 27%	2834
	11th to 20th	Night	21% 9% 2 7% 5% 5% 6% 4 6% 8% 27%	2786
	21st to end	Night	18% 6% 3 6% 4 3 4 3 5% 7% 41%	2738
June	1st to 10th	Night	18% 9% 2 6% 4 5% 5% 4 4 6% 37%	1520
	11th to 20th	Night	17% 9% 2 7% 3 3 3 3 6% 9% 37%	1520
	21st to end	Night	16% 6% 2 5% 4 4 5% 3 7% 9% 38%	1512
July	1st to 10th	Night	15% 6% 2 6% 5% 5% 4 4 5% 8% 40%	1440
	11th to 20th	Night	12% 8% 2 6% 5% 5% 5% 5% 6% 8% 38%	1440
	21st to end	Night	13% 6% 2 6% 5% 5% 5% 3 6% 8% 42%	1574
August	1st to 10th	Night	10% 4 2 5% 4 5% 5% 6% 6% 9% 43%	1571
	11th to 20th	Night	11% 6% 2 8% 6% 6% 6% 5% 7% 7% 37%	1596
	21st to end	Night	13% 5% 2 4 4 4 4 4 5% 9% 46%	1980
September	1st to 10th	Night	13% 6% 2 6% 4 4 5% 3 5% 7% 47%	1813
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 4 6% 53%	1980
	21st to end	Night	16% 5% 2 6% 4 4 3 3 5% 7% 45%	1980
October	1st to 10th	Night	22% 6% 2 6% 4 4 3 3 5% 5% 41%	1980
	11th to 20th	Night	15% 5% 2 5% 4 3 5% 3 5% 7% 44%	2198
	21st to end	Night	22% 7% 2 6% 4 3 4 3 5% 6% 38%	2574
November	1st to 10th	Night	15% 5% 2 6% 4 3 4 3 4 6% 48%	2407
	11th to 20th	Night	17% 7% 2 5% 3 3 4 3 4 6% 46%	2470
	21st to end	Night	16% 7% 2 5% 4 3 4 3 5% 6% 44%	2470
December	1st to 10th	Night	19% 9% 3 7% 4 4 4 3 5% 5% 39%	2617
	11th to 20th	Night	20% 6% 2 5% 3 3 4 4 5% 6% 41%	3288
	21st to end	Night	21% 9% 3 6% 4 4 4 3 4 5% 36%	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	43% 1 8% 34% 13% 1	2518
	11th to 20th	Day	45% 3 10% 26% 14% 2	2520
	21st to end	Day	53% 2 9% 24% 10% 2	2772
February	1st to 10th	Day	48% 2 12% 21% 14% 3	1761
	11th to 20th	Day	45% 4 11% 22% 16% 3	1857
	21st to end	Day	49% 2 10% 21% 15% 3	1570
March	1st to 10th	Day	59% 1 9% 16% 12% 3	3119
	11th to 20th	Day	43% 1 12% 24% 16% 3	3350
	21st to end	Day	53% 1 4 17% 15% 8%	3999
April	1st to 10th	Day	50% 2 8% 18% 17% 4	2280
	11th to 20th	Day	46% 2 10% 23% 16% 3	2283
	21st to end	Day	49% 3 7% 21% 18% 4	2470
May	1st to 10th	Day	59% 2 10% 18% 10% 1	4120
	11th to 20th	Day	54% 2 14% 18% 11% 2	4138
	21st to end	Day	40% 2 12% 25% 19% 2	4837
June	1st to 10th	Day	48% 4 12% 23% 12% 1	2660
	11th to 20th	Day	43% 3 13% 22% 17% 2	2660
	21st to end	Day	46% 4 12% 24% 13% 1	2646
July	1st to 10th	Day	40% 4 12% 25% 16% 2	2450
	11th to 20th	Day	40% 3 13% 28% 14% 1	2445
	21st to end	Day	39% 3 14% 26% 14% 3	2591
August	1st to 10th	Day	41% 5% 13% 27% 13% 1	2333
	11th to 20th	Day	41% 4 14% 26% 14% 1	2300
	21st to end	Day	36% 4 11% 27% 19% 3	2376
September	1st to 10th	Day	37% 3 12% 26% 21% 1	2147
	11th to 20th	Day	37% 2 7% 29% 23% 2	1980
	21st to end	Day	41% 2 8% 25% 23% 3	1980
October	1st to 10th	Day	47% 3 9% 23% 14% 4	1980
	11th to 20th	Day	39% 2 10% 32% 15% 2	1759
	21st to end	Day	48% 2 11% 21% 15% 3	1782
November	1st to 10th	Day	40% 2 11% 27% 17% 3	1671
	11th to 20th	Day	43% 2 8% 24% 22% 3	1710
	21st to end	Day	43% 3 14% 23% 15% 2	1710
December	1st to 10th	Day	47% 3 14% 17% 18% 1	1560
	11th to 20th	Day	46% 2 11% 18% 17% 6%	1906
	21st to end	Day	54% 2 10% 22% 11% 1	2772
January	1st to 10th	Night	41% 2 11% 30% 13% 3	4429
	11th to 20th	Night	48% 3 10% 23% 14% 3	4440
	21st to end	Night	58% 2 8% 19% 11% 2	4884
February	1st to 10th	Night	48% 3 12% 21% 14% 3	2415
	11th to 20th	Night	45% 3 9% 22% 17% 4	2220
	21st to end	Night	44% 2 8% 26% 16% 4	1884
March	1st to 10th	Night	57% 1 8% 19% 12% 4	3734
	11th to 20th	Night	49% 2 11% 18% 18% 3	3609
	21st to end	Night	55% 1 4 15% 18% 7%	3630
April	1st to 10th	Night	50% 2 9% 18% 17% 3	1900
	11th to 20th	Night	47% 2 7% 22% 19% 3	1845
	21st to end	Night	49% 2 9% 19% 17% 3	1710
May	1st to 10th	Night	59% 2 11% 18% 8% 2	2840
	11th to 20th	Night	56% 2 15% 16% 9% 2	2787
	21st to end	Night	45% 2 14% 22% 16% 1	2739
June	1st to 10th	Night	49% 3 11% 24% 13% 1	1520
	11th to 20th	Night	44% 3 13% 22% 16% 2	1520
	21st to end	Night	42% 5% 13% 24% 14% 1	1512
July	1st to 10th	Night	42% 3 14% 24% 16% 1	1400
	11th to 20th	Night	42% 4 13% 28% 11% 1	1392
	21st to end	Night	40% 4 13% 30% 12% 2	1486
August	1st to 10th	Night	36% 5% 15% 27% 15% 2	1561
	11th to 20th	Night	45% 4 14% 22% 14% 1	1596
	21st to end	Night	36% 3 10% 28% 21% 1	1980
September	1st to 10th	Night	38% 3 12% 27% 20% 2	1813
	11th to 20th	Night	35% 2 9% 25% 27% 2	1980
	21st to end	Night	40% 3 7% 26% 21% 3	1980
October	1st to 10th	Night	47% 3 10% 24% 13% 4	1980
	11th to 20th	Night	40% 3 12% 30% 15% 1	2198
	21st to end	Night	49% 2 11% 22% 15% 1	2574
November	1st to 10th	Night	39% 3 11% 24% 20% 3	2407
	11th to 20th	Night	42% 2 9% 24% 20% 3	2470
	21st to end	Night	41% 3 13% 26% 15% 2	2470
December	1st to 10th	Night	48% 2 11% 23% 14% 1	2617
	11th to 20th	Night	45% 2 13% 18% 21% 1	3288
	21st to end	Night	52% 2 7% 26% 13% 1	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	26% 24% 27% 19% 3	180
	11th to 20th	Day	24% 29% 31% 13% 2 1	180
	21st to end	Day	22% 28% 34% 12% 4	198
February	1st to 10th	Day	29% 22% 35% 13% 1	371
	11th to 20th	Day	27% 26% 35% 11% 2	456
	21st to end	Day	26% 20% 35% 14% 4	382
March	1st to 10th	Day	27% 19% 37% 13% 3	460
	11th to 20th	Day	27% 25% 33% 11% 3 1	460
	21st to end	Day	31% 21% 30% 11% 6% 2	506
April	1st to 10th	Day	28% 27% 24% 15% 5% 1	460
	11th to 20th	Day	28% 23% 31% 14% 4	452
	21st to end	Day	27% 17% 35% 17% 2 1	460
May	1st to 10th	Day	31% 23% 28% 13% 4 1	463
	11th to 20th	Day	22% 18% 37% 19% 4 1	487
	21st to end	Day	19% 15% 37% 22% 6% 1	529
June	1st to 10th	Day	22% 11% 37% 20% 9% 1	490
	11th to 20th	Day	16% 18% 36% 22% 7% 2	490
	21st to end	Day	20% 12% 38% 23% 6% 2	486
July	1st to 10th	Day	19% 7% 33% 28% 10% 3	445
	11th to 20th	Day	16% 9% 32% 31% 11% 3	444
	21st to end	Day	13% 6% 36% 35% 9% 1	488
August	1st to 10th	Day	12% 9% 35% 30% 11% 3	446
	11th to 20th	Day	17% 7% 33% 27% 13% 4	439
	21st to end	Day	16% 7% 33% 27% 14% 3	495
September	1st to 10th	Day	19% 10% 30% 25% 13% 3	450
	11th to 20th	Day	22% 10% 30% 19% 11% 7%	450
	21st to end	Day	20% 12% 33% 23% 8% 5%	450
October	1st to 10th	Day	28% 11% 27% 21% 10% 4	450
	11th to 20th	Day	20% 18% 28% 23% 10% 2	393
	21st to end	Day	27% 15% 32% 17% 8% 1	396
November	1st to 10th	Day	18% 15% 36% 19% 10% 2	365
	11th to 20th	Day	28% 21% 30% 16% 5% 1	370
	21st to end	Day	25% 19% 31% 16% 6% 1	370
December	1st to 10th	Day	25% 25% 31% 15% 3	220
	11th to 20th	Day	31% 22% 37% 8% 2	180
	21st to end	Day	23% 26% 30% 15% 5% 2	198
January	1st to 10th	Night	22% 20% 37% 19% 3	760
	11th to 20th	Night	27% 20% 33% 18% 2	760
	21st to end	Night	21% 20% 35% 20% 4 1	836
February	1st to 10th	Night	23% 18% 35% 22% 2	760
	11th to 20th	Night	23% 18% 39% 17% 3	743
	21st to end	Night	26% 17% 33% 19% 4	628
March	1st to 10th	Night	26% 17% 35% 19% 4	760
	11th to 20th	Night	24% 17% 38% 17% 4	760
	21st to end	Night	26% 16% 33% 19% 5%	836
April	1st to 10th	Night	26% 18% 32% 21% 4	760
	11th to 20th	Night	26% 17% 33% 19% 5%	721
	21st to end	Night	24% 15% 32% 25% 3	570
May	1st to 10th	Night	28% 12% 33% 21% 5% 1	570
	11th to 20th	Night	23% 13% 34% 24% 5%	548
	21st to end	Night	21% 7% 32% 30% 10%	411
June	1st to 10th	Night	22% 6% 33% 29% 9% 1	380
	11th to 20th	Night	21% 5% 33% 32% 8% 1	380
	21st to end	Night	22% 4 31% 34% 9%	378
July	1st to 10th	Night	16% 4 28% 39% 11% 1	350
	11th to 20th	Night	14% 3 26% 40% 17% 1	348
	21st to end	Night	15% 3 30% 41% 11% 1	394
August	1st to 10th	Night	12% 3 31% 40% 14% 1	497
	11th to 20th	Night	14% 4 29% 36% 17%	532
	21st to end	Night	17% 3 23% 37% 17% 3	792
September	1st to 10th	Night	15% 5% 31% 33% 15% 1	720
	11th to 20th	Night	18% 6% 28% 26% 19% 3	720
	21st to end	Night	18% 7% 28% 29% 16% 2	720
October	1st to 10th	Night	25% 9% 26% 24% 14% 2	720
	11th to 20th	Night	19% 11% 33% 24% 12% 1	720
	21st to end	Night	27% 13% 31% 22% 7%	792
November	1st to 10th	Night	17% 14% 32% 27% 8% 1	740
	11th to 20th	Night	23% 17% 32% 20% 7%	760
	21st to end	Night	21% 22% 32% 19% 5%	760
December	1st to 10th	Night	26% 17% 36% 17% 4	760
	11th to 20th	Night	22% 20% 33% 21% 4 1	760
	21st to end	Night	26% 18% 34% 20% 2	836

Page generated at 2024-06-26 22:18:44. Version ac07

Copyright © 2024 Attilla Danko.