Richard Schueller Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Richard Schueller Observatory clear sky chart from 2005-11-06 to 2024-12-02.

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	17% 7% 2 6% 4 4 4 4 5% 7% 38%	101485
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 39%	98150
Transparency	Day	43% 7% 12% 22% 15% 2	105036
	Night	43% 6% 12% 21% 15% 2	102688
Seeing	Day	23% 17% 32% 19% 7% 2	15102
	Night	21% 14% 33% 25% 7% 1	24009

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% 4 4 3 3 5% 6% 44%	2517
	11th to 20th	Day	17% 7% 3 7% 4 4 5% 3 5% 5% 41%	2520
	21st to end	Day	21% 11% 3 6% 4 4 4 3 4 5% 34%	2772
February	1st to 10th	Day	19% 8% 3 4 5% 4 5% 5% 5% 6% 36%	1755
	11th to 20th	Day	13% 8% 2 7% 4 4 6% 3 6% 7% 39%	1848
	21st to end	Day	18% 9% 3 7% 5% 4 4 4 4 5% 37%	1570
March	1st to 10th	Day	24% 14% 2 6% 4 4 4 2 5% 5% 30%	3116
	11th to 20th	Day	14% 8% 2 6% 4 5% 4 4 6% 6% 41%	3338
	21st to end	Day	22% 9% 3 6% 4 4 4 4 5% 6% 34%	4029
April	1st to 10th	Day	18% 10% 3 7% 5% 4 3 3 4 7% 36%	2280
	11th to 20th	Day	17% 7% 2 5% 4 5% 5% 4 6% 7% 38%	2273
	21st to end	Day	22% 6% 2 7% 5% 4 4 3 5% 6% 35%	2470
May	1st to 10th	Day	23% 11% 3 8% 5% 5% 4 3 5% 7% 27%	4106
	11th to 20th	Day	23% 7% 3 8% 4 4 4 3 5% 7% 33%	4171
	21st to end	Day	15% 4 2 5% 4 4 4 4 6% 8% 45%	4837
June	1st to 10th	Day	19% 6% 2 6% 5% 5% 5% 4 6% 8% 34%	2660
	11th to 20th	Day	16% 6% 2 6% 4 4 5% 4 6% 8% 39%	2660
	21st to end	Day	18% 6% 3 7% 5% 4 5% 4 6% 8% 35%	2660
July	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 4 8% 9% 37%	4440
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 7% 10% 40%	4440
	21st to end	Day	17% 7% 2 8% 5% 4 4 4 6% 8% 35%	4814
August	1st to 10th	Day	15% 6% 3 7% 5% 5% 6% 4 7% 9% 34%	4170
	11th to 20th	Day	14% 7% 3 7% 4 5% 5% 4 6% 7% 37%	3996
	21st to end	Day	8% 4 2 6% 5% 5% 6% 5% 7% 9% 45%	4180
September	1st to 10th	Day	14% 5% 2 5% 4 4 4 4 6% 6% 47%	2277
	11th to 20th	Day	16% 6% 2 5% 3 3 2 2 5% 5% 51%	2090
	21st to end	Day	16% 6% 2 6% 4 4 3 3 5% 7% 44%	2090
October	1st to 10th	Day	22% 7% 2 7% 3 4 3 3 5% 6% 39%	2090
	11th to 20th	Day	15% 4 2 5% 4 3 4 3 5% 7% 47%	1848
	21st to end	Day	22% 6% 3 5% 4 3 3 3 4 6% 40%	1881
November	1st to 10th	Day	15% 6% 2 5% 4 3 3 2 4 5% 50%	1761
	11th to 20th	Day	18% 6% 2 5% 3 3 3 3 4 5% 48%	1800
	21st to end	Day	19% 7% 2 5% 3 3 3 4 5% 5% 43%	1800
December	1st to 10th	Day	18% 7% 3 7% 5% 4 3 4 5% 6% 39%	1548
	11th to 20th	Day	22% 6% 2 5% 3 4 2 3 3 5% 44%	1906
	21st to end	Day	23% 10% 3 6% 4 4 4 3 4 6% 33%	2772
January	1st to 10th	Night	18% 9% 2 5% 3 3 3 2 4 5% 46%	4429
	11th to 20th	Night	14% 8% 3 10% 5% 5% 4 3 4 5% 40%	4440
	21st to end	Night	21% 14% 4 7% 4 4 4 3 4 5% 30%	4884
February	1st to 10th	Night	16% 9% 2 6% 5% 4 5% 4 5% 5% 38%	2419
	11th to 20th	Night	14% 9% 3 6% 4 4 5% 3 5% 7% 40%	2218
	21st to end	Night	18% 9% 2 6% 4 3 4 3 5% 6% 41%	1884
March	1st to 10th	Night	27% 11% 2 5% 3 4 3 3 4 5% 32%	3724
	11th to 20th	Night	12% 9% 4 8% 5% 5% 6% 4 5% 6% 38%	3621
	21st to end	Night	25% 8% 2 5% 4 4 5% 4 6% 5% 33%	3599
April	1st to 10th	Night	19% 8% 2 7% 5% 5% 4 3 5% 7% 36%	1900
	11th to 20th	Night	21% 8% 2 5% 4 4 3 4 4 5% 40%	1856
	21st to end	Night	21% 7% 2 6% 5% 4 4 3 4 6% 39%	1710
May	1st to 10th	Night	24% 11% 3 8% 5% 4 4 3 5% 7% 26%	2834
	11th to 20th	Night	20% 8% 3 8% 4 5% 6% 5% 6% 7% 28%	2750
	21st to end	Night	16% 6% 3 7% 4 3 4 3 5% 7% 41%	2738
June	1st to 10th	Night	18% 8% 3 7% 5% 4 4 3 5% 6% 38%	1520
	11th to 20th	Night	19% 7% 2 5% 5% 4 4 4 5% 8% 37%	1520
	21st to end	Night	16% 6% 2 6% 5% 4 5% 4 6% 9% 38%	1520
July	1st to 10th	Night	12% 6% 3 7% 5% 6% 5% 5% 6% 10% 36%	2520
	11th to 20th	Night	11% 6% 3 7% 5% 5% 6% 3 7% 8% 39%	2520
	21st to end	Night	15% 8% 2 7% 4 4 4 4 6% 7% 38%	2739
August	1st to 10th	Night	19% 6% 3 8% 4 5% 5% 5% 5% 6% 34%	2726
	11th to 20th	Night	11% 7% 3 8% 4 5% 6% 5% 7% 8% 37%	2814
	21st to end	Night	10% 3 1 4 4 3 4 3 6% 8% 55%	3476
September	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 5% 6% 49%	1902
	11th to 20th	Night	14% 5% 2 4 4 3 3 2 5% 6% 52%	2090
	21st to end	Night	18% 5% 3 5% 3 3 4 4 5% 6% 45%	2090
October	1st to 10th	Night	20% 6% 2 6% 4 4 4 2 5% 5% 41%	2090
	11th to 20th	Night	16% 5% 1 5% 3 4 4 4 6% 6% 47%	2328
	21st to end	Night	22% 6% 1 6% 3 4 4 3 4 5% 39%	2717
November	1st to 10th	Night	15% 5% 1 5% 4 3 4 4 5% 5% 49%	2537
	11th to 20th	Night	18% 6% 2 5% 4 3 3 3 4 5% 47%	2600
	21st to end	Night	16% 7% 2 6% 4 3 4 2 5% 6% 44%	2600
December	1st to 10th	Night	19% 9% 3 6% 4 4 4 3 5% 5% 38%	2663
	11th to 20th	Night	20% 6% 2 5% 4 4 3 4 5% 6% 41%	3288
	21st to end	Night	21% 10% 3 7% 5% 4 3 3 5% 5% 34%	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	40% 5% 12% 32% 10% 1	2518
	11th to 20th	Day	44% 7% 10% 25% 12% 1	2520
	21st to end	Day	51% 6% 10% 22% 9% 2	2772
February	1st to 10th	Day	46% 7% 12% 19% 13% 3	1755
	11th to 20th	Day	43% 7% 12% 20% 15% 3	1857
	21st to end	Day	49% 5% 11% 19% 13% 3	1570
March	1st to 10th	Day	57% 5% 10% 15% 10% 3	3119
	11th to 20th	Day	37% 9% 16% 21% 14% 3	3338
	21st to end	Day	50% 4 7% 16% 16% 7%	4029
April	1st to 10th	Day	48% 5% 9% 17% 16% 3	2280
	11th to 20th	Day	44% 7% 11% 19% 16% 3	2273
	21st to end	Day	48% 6% 8% 17% 17% 4	2470
May	1st to 10th	Day	55% 8% 11% 15% 10% 1	4120
	11th to 20th	Day	50% 7% 15% 16% 10% 2	4175
	21st to end	Day	35% 8% 13% 23% 19% 2	4837
June	1st to 10th	Day	47% 8% 12% 21% 12%	2660
	11th to 20th	Day	42% 8% 14% 18% 16% 3	2660
	21st to end	Day	45% 9% 12% 21% 12% 1	2660
July	1st to 10th	Day	42% 8% 12% 21% 15% 1	4370
	11th to 20th	Day	38% 7% 16% 25% 13% 1	4365
	21st to end	Day	47% 7% 12% 20% 13% 2	4661
August	1st to 10th	Day	45% 9% 15% 22% 8% 1	4156
	11th to 20th	Day	43% 8% 14% 26% 9% 1	4035
	21st to end	Day	33% 7% 12% 29% 17% 2	4180
September	1st to 10th	Day	36% 6% 12% 24% 20% 2	2277
	11th to 20th	Day	36% 4 9% 26% 22% 2	2090
	21st to end	Day	40% 6% 9% 22% 21% 2	2090
October	1st to 10th	Day	44% 5% 9% 21% 19% 2	3480
	11th to 20th	Day	31% 5% 8% 28% 24% 3	3051
	21st to end	Day	34% 4 8% 31% 20% 3	3081
November	1st to 10th	Day	37% 5% 12% 27% 17% 2	1761
	11th to 20th	Day	39% 4 8% 23% 22% 3	1800
	21st to end	Day	42% 5% 15% 23% 13% 2	1800
December	1st to 10th	Day	47% 5% 14% 17% 16% 1	1548
	11th to 20th	Day	43% 4 14% 18% 16% 5%	1906
	21st to end	Day	52% 6% 12% 19% 10% 1	2772
January	1st to 10th	Night	40% 5% 14% 27% 12% 3	4429
	11th to 20th	Night	45% 5% 13% 20% 12% 3	4440
	21st to end	Night	55% 6% 10% 17% 10% 2	4884
February	1st to 10th	Night	46% 6% 13% 20% 13% 2	2419
	11th to 20th	Night	44% 5% 12% 21% 16% 4	2220
	21st to end	Night	44% 5% 9% 23% 15% 4	1884
March	1st to 10th	Night	54% 5% 10% 19% 10% 3	3734
	11th to 20th	Night	43% 9% 14% 17% 16% 3	3622
	21st to end	Night	50% 5% 7% 13% 18% 7%	3599
April	1st to 10th	Night	46% 6% 12% 17% 15% 3	1900
	11th to 20th	Night	45% 5% 10% 19% 18% 3	1856
	21st to end	Night	46% 5% 12% 17% 16% 4	1710
May	1st to 10th	Night	56% 7% 12% 15% 8% 2	2840
	11th to 20th	Night	52% 10% 15% 12% 9% 2	2751
	21st to end	Night	40% 8% 15% 21% 14% 2	2739
June	1st to 10th	Night	47% 6% 12% 22% 12%	1520
	11th to 20th	Night	44% 8% 13% 19% 14% 2	1520
	21st to end	Night	41% 9% 15% 21% 13% 1	1520
July	1st to 10th	Night	42% 9% 12% 21% 15%	2480
	11th to 20th	Night	41% 7% 16% 21% 14% 1	2472
	21st to end	Night	45% 7% 12% 20% 15% 1	2651
August	1st to 10th	Night	50% 8% 12% 19% 10% 1	2716
	11th to 20th	Night	42% 10% 14% 23% 10%	2841
	21st to end	Night	27% 6% 15% 28% 22% 1	3476
September	1st to 10th	Night	36% 6% 12% 25% 19% 1	1902
	11th to 20th	Night	33% 6% 11% 23% 26% 2	2090
	21st to end	Night	39% 7% 10% 24% 19% 2	2090
October	1st to 10th	Night	40% 5% 15% 23% 15% 2	3480
	11th to 20th	Night	27% 5% 11% 27% 27% 3	3864
	21st to end	Night	35% 4 12% 31% 17% 2	4467
November	1st to 10th	Night	37% 6% 11% 22% 20% 3	2537
	11th to 20th	Night	40% 4 10% 22% 20% 3	2600
	21st to end	Night	41% 5% 14% 24% 15% 2	2600
December	1st to 10th	Night	47% 5% 12% 22% 13% 1	2663
	11th to 20th	Night	43% 6% 15% 17% 18% 1	3288
	21st to end	Night	50% 6% 9% 24% 10% 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% 25% 31% 15% 3	180
	11th to 20th	Day	34% 21% 32% 11% 2 1	180
	21st to end	Day	24% 26% 35% 11% 4	198
February	1st to 10th	Day	32% 19% 34% 14% 1	357
	11th to 20th	Day	28% 29% 31% 11% 2	456
	21st to end	Day	28% 20% 35% 13% 3	382
March	1st to 10th	Day	29% 20% 36% 12% 3	460
	11th to 20th	Day	28% 24% 32% 11% 3 1	460
	21st to end	Day	31% 23% 29% 10% 5% 2	506
April	1st to 10th	Day	28% 26% 26% 13% 6% 1	460
	11th to 20th	Day	29% 25% 29% 11% 6%	452
	21st to end	Day	27% 19% 34% 15% 3 2	460
May	1st to 10th	Day	31% 22% 30% 11% 4 2	463
	11th to 20th	Day	23% 17% 38% 17% 4 1	487
	21st to end	Day	19% 14% 38% 22% 6% 1	529
June	1st to 10th	Day	20% 15% 37% 18% 8% 1	490
	11th to 20th	Day	15% 18% 36% 22% 7% 1	490
	21st to end	Day	19% 16% 36% 19% 8% 2	490
July	1st to 10th	Day	17% 10% 31% 29% 11% 3	485
	11th to 20th	Day	15% 7% 34% 29% 13% 2	484
	21st to end	Day	13% 9% 37% 30% 9% 1	532
August	1st to 10th	Day	12% 10% 34% 30% 13% 2	486
	11th to 20th	Day	17% 10% 27% 28% 14% 4	479
	21st to end	Day	12% 9% 34% 26% 14% 4	539
September	1st to 10th	Day	18% 11% 29% 22% 15% 5%	490
	11th to 20th	Day	20% 14% 26% 19% 12% 9%	490
	21st to end	Day	19% 13% 32% 22% 9% 5%	490
October	1st to 10th	Day	27% 13% 24% 22% 10% 4	490
	11th to 20th	Day	20% 18% 28% 23% 10% 2	433
	21st to end	Day	28% 14% 32% 18% 7% 1	429
November	1st to 10th	Day	22% 15% 33% 19% 9% 2	395
	11th to 20th	Day	31% 20% 28% 16% 5% 1	400
	21st to end	Day	30% 18% 30% 15% 6% 1	400
December	1st to 10th	Day	22% 28% 32% 14% 3	202
	11th to 20th	Day	32% 25% 32% 9% 2	180
	21st to end	Day	23% 29% 29% 14% 4 2	198
January	1st to 10th	Night	21% 20% 39% 18% 3	760
	11th to 20th	Night	27% 19% 34% 18% 2	760
	21st to end	Night	21% 20% 36% 20% 3	836
February	1st to 10th	Night	23% 17% 38% 21% 2	760
	11th to 20th	Night	21% 21% 39% 17% 2	743
	21st to end	Night	25% 19% 32% 20% 3	628
March	1st to 10th	Night	26% 18% 35% 19% 3	760
	11th to 20th	Night	22% 21% 37% 16% 4	760
	21st to end	Night	26% 19% 32% 19% 4	836
April	1st to 10th	Night	24% 19% 33% 20% 4	760
	11th to 20th	Night	25% 19% 33% 17% 5%	732
	21st to end	Night	23% 16% 37% 22% 2 1	570
May	1st to 10th	Night	27% 14% 34% 20% 5%	570
	11th to 20th	Night	22% 14% 37% 22% 5%	525
	21st to end	Night	18% 10% 35% 30% 7%	411
June	1st to 10th	Night	20% 8% 34% 29% 8% 1	380
	11th to 20th	Night	18% 9% 34% 30% 7% 1	380
	21st to end	Night	19% 5% 37% 32% 7%	380
July	1st to 10th	Night	15% 5% 29% 41% 9% 1	370
	11th to 20th	Night	13% 4 27% 42% 13% 1	368
	21st to end	Night	13% 5% 29% 43% 10%	416
August	1st to 10th	Night	12% 5% 28% 41% 12% 1	507
	11th to 20th	Night	13% 6% 30% 38% 13% 1	581
	21st to end	Night	14% 5% 25% 39% 16% 2	836
September	1st to 10th	Night	16% 4 34% 32% 14% 1	760
	11th to 20th	Night	16% 8% 26% 28% 19% 3	760
	21st to end	Night	20% 7% 27% 30% 13% 2	760
October	1st to 10th	Night	24% 10% 26% 26% 12% 2	760
	11th to 20th	Night	19% 12% 31% 25% 11% 1	760
	21st to end	Night	25% 13% 32% 23% 5%	836
November	1st to 10th	Night	18% 13% 34% 26% 8% 1	780
	11th to 20th	Night	22% 18% 32% 21% 6% 1	800
	21st to end	Night	24% 19% 33% 20% 4 1	800
December	1st to 10th	Night	25% 17% 36% 18% 4	768
	11th to 20th	Night	24% 17% 32% 23% 3 1	760
	21st to end	Night	25% 17% 35% 19% 3	836

Page generated at 2024-11-29 10:43:04. Version ac07

Copyright © 2024 Attilla Danko.