Brodie Road Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brodie Road Observatory clear sky chart from 2005-11-06 to 2024-05-14.

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% 10% 3 8% 5% 4 4 4 5% 6% 32%	83363
	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 31%	86141
Transparency	Day	53% 3 11% 21% 11% 1	83068
	Night	56% 2 10% 20% 10% 1	85970
Seeing	Day	24% 16% 30% 19% 8% 2	13855
	Night	24% 14% 29% 24% 9% 1	23022

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	18% 16% 6% 13% 6% 4 4 3 4 4 23%	2517
	11th to 20th	Day	14% 15% 6% 11% 7% 6% 5% 4 5% 5% 23%	2520
	21st to end	Day	15% 19% 6% 9% 6% 5% 5% 4 6% 6% 19%	2776
February	1st to 10th	Day	15% 17% 4 11% 7% 4 4 4 4 5% 25%	1710
	11th to 20th	Day	14% 14% 5% 11% 7% 5% 4 3 4 6% 26%	1724
	21st to end	Day	20% 14% 5% 9% 5% 5% 4 3 4 5% 26%	1570
March	1st to 10th	Day	21% 13% 4 10% 6% 5% 4 3 4 5% 26%	3116
	11th to 20th	Day	13% 18% 5% 10% 6% 5% 4 3 4 5% 26%	3352
	21st to end	Day	16% 8% 3 8% 6% 4 4 3 4 6% 38%	4118
April	1st to 10th	Day	21% 12% 4 7% 5% 4 3 2 4 5% 32%	2280
	11th to 20th	Day	21% 10% 3 7% 5% 3 3 3 5% 5% 34%	2254
	21st to end	Day	23% 10% 3 8% 4 4 4 4 4 4 31%	2401
May	1st to 10th	Day	20% 8% 3 7% 5% 4 5% 3 5% 6% 33%	2660
	11th to 20th	Day	18% 7% 3 7% 4 4 4 3 5% 6% 38%	2520
	21st to end	Day	18% 7% 2 7% 5% 4 5% 4 6% 6% 36%	2725
June	1st to 10th	Day	24% 8% 2 7% 5% 4 4 4 5% 8% 29%	2520
	11th to 20th	Day	16% 6% 2 6% 4 5% 5% 4 6% 8% 37%	2520
	21st to end	Day	20% 7% 3 6% 5% 6% 5% 4 6% 7% 30%	2520
July	1st to 10th	Day	12% 7% 3 6% 6% 5% 5% 4 6% 8% 40%	2520
	11th to 20th	Day	13% 6% 2 6% 6% 5% 5% 5% 8% 9% 36%	2520
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 4 7% 9% 38%	2744
August	1st to 10th	Day	13% 6% 3 6% 5% 5% 5% 4 6% 9% 37%	2506
	11th to 20th	Day	10% 6% 2 6% 6% 5% 5% 4 6% 9% 40%	2264
	21st to end	Day	15% 5% 2 7% 4 5% 5% 4 7% 7% 40%	2376
September	1st to 10th	Day	14% 7% 2 5% 4 4 4 4 6% 8% 41%	2160
	11th to 20th	Day	14% 5% 2 5% 4 3 4 3 5% 7% 48%	2116
	21st to end	Day	17% 8% 2 5% 4 4 4 3 6% 7% 41%	1980
October	1st to 10th	Day	21% 7% 3 7% 4 4 4 4 4 6% 36%	1814
	11th to 20th	Day	21% 11% 3 9% 7% 5% 4 3 4 6% 28%	1796
	21st to end	Day	25% 11% 3 7% 4 4 5% 4 5% 5% 26%	1782
November	1st to 10th	Day	17% 9% 4 7% 5% 5% 5% 4 4 6% 33%	1671
	11th to 20th	Day	18% 12% 3 9% 6% 5% 5% 3 5% 6% 28%	1593
	21st to end	Day	21% 13% 4 9% 6% 6% 5% 3 6% 6% 22%	1520
December	1st to 10th	Day	24% 15% 4 11% 6% 5% 4 3 6% 4 17%	1520
	11th to 20th	Day	21% 15% 5% 10% 4 3 4 3 4 5% 24%	1906
	21st to end	Day	28% 18% 4 11% 4 3 3 2 3 3 20%	2772
January	1st to 10th	Night	17% 17% 6% 11% 5% 5% 4 3 4 5% 21%	4429
	11th to 20th	Night	13% 15% 5% 14% 7% 6% 6% 4 5% 5% 20%	4440
	21st to end	Night	16% 19% 6% 11% 6% 5% 4 3 4 5% 22%	4879
February	1st to 10th	Night	16% 13% 5% 11% 8% 6% 5% 4 6% 5% 23%	2470
	11th to 20th	Night	14% 12% 6% 11% 6% 6% 5% 4 5% 5% 27%	2340
	21st to end	Night	15% 14% 5% 10% 6% 4 4 4 4 5% 30%	1884
March	1st to 10th	Night	20% 11% 3 8% 5% 4 4 3 4 5% 32%	3724
	11th to 20th	Night	19% 17% 5% 10% 6% 4 4 2 4 5% 26%	3589
	21st to end	Night	14% 10% 4 9% 5% 4 4 3 4 4 38%	3512
April	1st to 10th	Night	22% 11% 3 7% 5% 4 3 4 4 6% 31%	1900
	11th to 20th	Night	22% 10% 3 7% 5% 4 4 3 5% 4 35%	1875
	21st to end	Night	22% 9% 2 7% 5% 4 4 3 5% 5% 34%	1786
May	1st to 10th	Night	21% 9% 2 6% 5% 4 4 4 5% 7% 34%	1530
	11th to 20th	Night	18% 9% 2 6% 4 3 3 3 4 7% 40%	1445
	21st to end	Night	14% 8% 2 6% 5% 4 5% 3 5% 8% 41%	1550
June	1st to 10th	Night	20% 7% 2 5% 5% 5% 5% 5% 7% 8% 30%	1440
	11th to 20th	Night	16% 7% 3 5% 4 4 5% 4 5% 7% 40%	1440
	21st to end	Night	17% 6% 3 7% 5% 4 6% 4 5% 8% 35%	1440
July	1st to 10th	Night	10% 5% 2 6% 5% 4 5% 4 5% 8% 45%	1440
	11th to 20th	Night	11% 6% 3 7% 4 4 4 4 7% 11% 40%	1440
	21st to end	Night	11% 6% 3 6% 4 4 4 5% 6% 9% 41%	1574
August	1st to 10th	Night	11% 5% 2 6% 4 4 5% 4 6% 10% 43%	1432
	11th to 20th	Night	12% 6% 3 5% 5% 4 4 4 5% 7% 45%	1615
	21st to end	Night	13% 6% 2 7% 5% 4 5% 4 5% 8% 42%	1980
September	1st to 10th	Night	11% 7% 2 7% 5% 5% 4 4 5% 7% 43%	1800
	11th to 20th	Night	16% 5% 2 5% 3 3 3 3 5% 7% 48%	1844
	21st to end	Night	17% 5% 2 5% 4 4 4 3 5% 6% 43%	1980
October	1st to 10th	Night	20% 7% 3 7% 4 4 5% 3 6% 7% 36%	2144
	11th to 20th	Night	20% 9% 3 8% 6% 5% 4 4 5% 5% 32%	2162
	21st to end	Night	24% 9% 4 8% 5% 5% 4 3 4 5% 28%	2574
November	1st to 10th	Night	20% 10% 3 7% 4 4 4 3 4 6% 33%	2407
	11th to 20th	Night	19% 10% 3 8% 5% 5% 5% 4 4 6% 31%	2584
	21st to end	Night	22% 13% 4 10% 6% 5% 5% 3 4 6% 25%	2660
December	1st to 10th	Night	21% 16% 6% 9% 7% 5% 4 4 4 5% 19%	2660
	11th to 20th	Night	22% 16% 4 9% 5% 4 4 3 4 4 25%	3288
	21st to end	Night	31% 17% 4 9% 4 3 3 2 3 4 20%	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	67% 1 13% 13% 5% 1	2518
	11th to 20th	Day	64% 1 11% 15% 8% 1	2520
	21st to end	Day	67% 3 13% 11% 5% 1	2776
February	1st to 10th	Day	63% 2 8% 20% 5% 2	1710
	11th to 20th	Day	60% 3 11% 18% 8% 1	1733
	21st to end	Day	62% 2 10% 14% 10% 2	1570
March	1st to 10th	Day	62% 1 8% 19% 8% 1	3119
	11th to 20th	Day	62% 1 10% 15% 10% 2	3352
	21st to end	Day	50% 1 6% 21% 19% 2	4118
April	1st to 10th	Day	56% 2 6% 20% 13% 3	2280
	11th to 20th	Day	53% 2 5% 21% 17% 2	2254
	21st to end	Day	57% 2 8% 16% 13% 4	2401
May	1st to 10th	Day	53% 3 6% 21% 15% 2	2660
	11th to 20th	Day	47% 3 8% 23% 16% 3	2524
	21st to end	Day	47% 3 13% 21% 14% 2	2725
June	1st to 10th	Day	54% 3 10% 20% 12% 1	2520
	11th to 20th	Day	45% 3 11% 25% 13% 3	2520
	21st to end	Day	51% 4 14% 20% 10% 1	2520
July	1st to 10th	Day	41% 4 12% 29% 14% 1	2450
	11th to 20th	Day	42% 4 14% 30% 10%	2445
	21st to end	Day	42% 4 16% 27% 11%	2591
August	1st to 10th	Day	42% 4 17% 28% 9%	2492
	11th to 20th	Day	40% 4 18% 27% 11%	2264
	21st to end	Day	42% 3 13% 28% 13% 1	2376
September	1st to 10th	Day	40% 3 14% 29% 13%	2160
	11th to 20th	Day	36% 3 11% 33% 15% 1	2116
	21st to end	Day	44% 3 14% 29% 10%	1980
October	1st to 10th	Day	50% 3 9% 26% 11%	1814
	11th to 20th	Day	59% 2 12% 19% 8%	1796
	21st to end	Day	60% 2 11% 18% 8% 1	1782
November	1st to 10th	Day	52% 3 13% 23% 9% 1	1671
	11th to 20th	Day	57% 4 11% 17% 11% 1	1593
	21st to end	Day	63% 4 13% 14% 5%	1520
December	1st to 10th	Day	69% 4 12% 12% 3	1520
	11th to 20th	Day	65% 3 13% 15% 4	1906
	21st to end	Day	72% 2 8% 14% 4	2772
January	1st to 10th	Night	67% 2 15% 12% 4	4429
	11th to 20th	Night	68% 2 11% 13% 5%	4440
	21st to end	Night	67% 2 12% 13% 6% 1	4879
February	1st to 10th	Night	63% 3 9% 17% 7% 1	2470
	11th to 20th	Night	58% 3 9% 20% 9% 1	2342
	21st to end	Night	58% 2 8% 18% 13% 1	1884
March	1st to 10th	Night	56% 1 8% 22% 10% 3	3734
	11th to 20th	Night	63% 1 9% 16% 9% 2	3590
	21st to end	Night	51% 1 4 24% 18% 3	3512
April	1st to 10th	Night	56% 2 7% 19% 14% 2	1900
	11th to 20th	Night	53% 3 6% 22% 15% 2	1875
	21st to end	Night	52% 2 7% 19% 15% 4	1786
May	1st to 10th	Night	51% 2 6% 20% 16% 4	1530
	11th to 20th	Night	46% 3 6% 22% 20% 4	1446
	21st to end	Night	42% 4 13% 21% 17% 3	1551
June	1st to 10th	Night	51% 3 11% 22% 12% 1	1440
	11th to 20th	Night	43% 4 11% 23% 18% 2	1440
	21st to end	Night	47% 4 13% 21% 14%	1440
July	1st to 10th	Night	36% 4 13% 28% 18% 1	1400
	11th to 20th	Night	39% 4 12% 32% 13%	1392
	21st to end	Night	38% 4 17% 27% 14% 1	1486
August	1st to 10th	Night	37% 4 19% 28% 12%	1422
	11th to 20th	Night	40% 3 16% 28% 12% 1	1615
	21st to end	Night	40% 3 15% 30% 11% 1	1980
September	1st to 10th	Night	43% 2 10% 28% 16% 1	1800
	11th to 20th	Night	37% 3 12% 35% 12% 1	1844
	21st to end	Night	42% 3 11% 31% 12%	1980
October	1st to 10th	Night	48% 4 10% 25% 13% 1	2144
	11th to 20th	Night	54% 3 11% 23% 9%	2162
	21st to end	Night	59% 3 12% 17% 9% 1	2574
November	1st to 10th	Night	53% 2 13% 22% 9% 1	2407
	11th to 20th	Night	55% 3 12% 20% 9% 1	2584
	21st to end	Night	61% 2 13% 17% 6%	2660
December	1st to 10th	Night	69% 3 9% 15% 4	2660
	11th to 20th	Night	65% 2 8% 18% 7% 1	3288
	21st to end	Night	72% 1 8% 14% 4	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	31% 16% 32% 18% 3	180
	11th to 20th	Day	32% 26% 27% 9% 4 1	180
	21st to end	Day	20% 21% 39% 18% 4	200
February	1st to 10th	Day	32% 30% 27% 9% 2	270
	11th to 20th	Day	27% 27% 38% 8%	331
	21st to end	Day	31% 20% 33% 15% 2	382
March	1st to 10th	Day	28% 22% 31% 15% 4	460
	11th to 20th	Day	29% 22% 33% 13% 2 1	460
	21st to end	Day	32% 22% 24% 14% 6% 1	506
April	1st to 10th	Day	31% 19% 31% 14% 5%	460
	11th to 20th	Day	34% 19% 26% 13% 6% 1	452
	21st to end	Day	32% 19% 29% 13% 7% 1	460
May	1st to 10th	Day	25% 17% 34% 16% 6% 1	463
	11th to 20th	Day	20% 17% 34% 20% 8% 2	459
	21st to end	Day	20% 18% 33% 21% 7% 1	485
June	1st to 10th	Day	28% 11% 31% 22% 6% 2	450
	11th to 20th	Day	18% 15% 32% 24% 8% 2	450
	21st to end	Day	23% 10% 34% 20% 11% 3	450
July	1st to 10th	Day	17% 7% 32% 27% 14% 3	445
	11th to 20th	Day	13% 11% 33% 28% 13% 2	444
	21st to end	Day	17% 8% 34% 28% 11% 2	488
August	1st to 10th	Day	16% 8% 28% 30% 14% 4	446
	11th to 20th	Day	15% 6% 28% 31% 13% 7%	439
	21st to end	Day	16% 10% 32% 22% 14% 6%	495
September	1st to 10th	Day	18% 9% 30% 21% 15% 6%	450
	11th to 20th	Day	16% 8% 28% 22% 17% 9%	450
	21st to end	Day	18% 14% 31% 19% 14% 4	450
October	1st to 10th	Day	24% 15% 26% 20% 12% 3	450
	11th to 20th	Day	26% 20% 27% 20% 7% 1	448
	21st to end	Day	34% 13% 29% 17% 6%	396
November	1st to 10th	Day	29% 17% 27% 19% 6% 1	365
	11th to 20th	Day	26% 24% 28% 17% 4	253
	21st to end	Day	28% 22% 28% 17% 6% 1	180
December	1st to 10th	Day	30% 17% 34% 15% 4	180
	11th to 20th	Day	32% 23% 32% 11% 1 1	180
	21st to end	Day	35% 24% 26% 14% 2	198
January	1st to 10th	Night	28% 18% 35% 15% 4	760
	11th to 20th	Night	29% 20% 26% 20% 5% 1	760
	21st to end	Night	21% 18% 34% 21% 5%	836
February	1st to 10th	Night	23% 19% 33% 22% 4	760
	11th to 20th	Night	23% 22% 34% 18% 4	743
	21st to end	Night	26% 18% 31% 23% 2	628
March	1st to 10th	Night	24% 19% 30% 23% 4	760
	11th to 20th	Night	27% 18% 32% 19% 3 1	760
	21st to end	Night	25% 17% 27% 25% 6% 1	836
April	1st to 10th	Night	31% 15% 29% 21% 4	760
	11th to 20th	Night	26% 19% 29% 21% 5%	751
	21st to end	Night	29% 14% 29% 20% 8%	646
May	1st to 10th	Night	26% 11% 30% 24% 7% 2	390
	11th to 20th	Night	23% 11% 29% 26% 10% 1	362
	21st to end	Night	17% 10% 37% 27% 9%	389
June	1st to 10th	Night	22% 8% 29% 31% 9% 1	360
	11th to 20th	Night	21% 8% 26% 31% 13% 1	360
	21st to end	Night	16% 8% 29% 28% 17% 1	360
July	1st to 10th	Night	12% 7% 30% 34% 16% 1	350
	11th to 20th	Night	14% 4 29% 36% 16%	348
	21st to end	Night	14% 4 32% 37% 13% 1	394
August	1st to 10th	Night	14% 6% 22% 37% 20% 1	358
	11th to 20th	Night	14% 2 26% 33% 22% 2	551
	21st to end	Night	16% 6% 28% 30% 18% 2	792
September	1st to 10th	Night	14% 6% 31% 34% 14% 1	720
	11th to 20th	Night	20% 6% 22% 30% 19% 3	720
	21st to end	Night	19% 10% 28% 24% 18% 2	720
October	1st to 10th	Night	24% 10% 27% 27% 11% 1	720
	11th to 20th	Night	25% 12% 29% 24% 10%	720
	21st to end	Night	29% 15% 28% 24% 4	792
November	1st to 10th	Night	27% 16% 24% 23% 8% 1	740
	11th to 20th	Night	24% 19% 32% 16% 9% 1	760
	21st to end	Night	28% 18% 26% 20% 7%	760
December	1st to 10th	Night	31% 18% 28% 19% 4	760
	11th to 20th	Night	31% 21% 26% 16% 5% 1	760
	21st to end	Night	38% 18% 26% 14% 4	836

Page generated at 2024-05-11 05:13:33. Version ac07

Copyright © 2024 Attilla Danko.