River Ridge Observatory
Clear Sky Chart
History

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

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	12% 6% 2 6% 4 4 4 4 5% 7% 45%	100599
	Night	12% 5% 2 5% 4 3 4 3 5% 7% 51%	98486
Transparency	Day	37% 6% 10% 23% 20% 5%	104243
	Night	33% 5% 9% 23% 23% 7%	102982
Seeing	Day	14% 10% 22% 27% 21% 6%	15362
	Night	14% 8% 26% 33% 18% 2	25140

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	17% 8% 3 7% 3 3 3 2 3 4 45%	2847
	11th to 20th	Day	11% 10% 2 6% 4 4 3 3 3 5% 50%	2850
	21st to end	Day	25% 7% 1 5% 3 2 3 2 3 3 47%	3135
February	1st to 10th	Day	20% 8% 3 5% 4 3 3 3 4 4 43%	1710
	11th to 20th	Day	17% 7% 4 6% 4 4 3 3 5% 5% 43%	1779
	21st to end	Day	21% 9% 3 7% 4 4 4 3 4 5% 37%	1627
March	1st to 10th	Day	19% 9% 3 7% 4 4 3 2 4 4 40%	3436
	11th to 20th	Day	13% 6% 3 6% 4 5% 4 3 4 6% 46%	3480
	21st to end	Day	16% 9% 3 6% 4 3 4 2 4 5% 43%	3814
April	1st to 10th	Day	13% 6% 2 5% 5% 4 4 4 5% 7% 45%	2271
	11th to 20th	Day	15% 6% 2 7% 4 4 4 3 4 6% 46%	2254
	21st to end	Day	15% 6% 3 6% 5% 4 4 4 5% 6% 41%	2280
May	1st to 10th	Day	16% 7% 3 8% 4 5% 4 3 5% 7% 38%	3765
	11th to 20th	Day	11% 5% 2 5% 5% 4 5% 4 6% 8% 43%	4068
	21st to end	Day	11% 7% 3 8% 6% 5% 6% 6% 6% 8% 34%	4477
June	1st to 10th	Day	8% 5% 2 6% 5% 4 5% 5% 7% 9% 43%	2589
	11th to 20th	Day	4 4 2 5% 5% 6% 5% 5% 8% 10% 46%	2656
	21st to end	Day	4 3 1 5% 5% 5% 6% 5% 8% 9% 49%	2470
July	1st to 10th	Day	8% 5% 2 5% 5% 5% 6% 5% 8% 10% 40%	4120
	11th to 20th	Day	6% 3 2 4 4 4 5% 4 7% 8% 53%	4120
	21st to end	Day	11% 9% 3 9% 5% 5% 6% 4 7% 9% 33%	4465
August	1st to 10th	Day	4 2 1 4 3 4 4 4 6% 8% 60%	4104
	11th to 20th	Day	10% 5% 2 6% 4 4 4 5% 8% 10% 41%	3765
	21st to end	Day	5% 4 2 5% 5% 4 5% 5% 6% 8% 52%	4180
September	1st to 10th	Day	12% 5% 2 5% 5% 3 5% 4 5% 7% 47%	2280
	11th to 20th	Day	14% 5% 2 5% 3 4 5% 4 5% 6% 47%	2277
	21st to end	Day	10% 5% 2 5% 3 4 5% 4 5% 6% 53%	1981
October	1st to 10th	Day	6% 4 2 5% 3 3 3 3 5% 6% 59%	1900
	11th to 20th	Day	13% 5% 2 4 3 3 2 3 4 5% 58%	1900
	21st to end	Day	18% 4 2 4 3 3 3 2 4 5% 52%	2090
November	1st to 10th	Day	12% 5% 2 4 3 3 2 3 4 6% 56%	1898
	11th to 20th	Day	9% 6% 2 5% 3 3 2 3 5% 6% 56%	1844
	21st to end	Day	17% 8% 2 5% 4 3 3 2 3 6% 46%	1654
December	1st to 10th	Day	18% 7% 2 5% 4 2 3 3 5% 5% 47%	1520
	11th to 20th	Day	13% 9% 3 7% 4 5% 4 3 4 4 44%	1918
	21st to end	Day	12% 7% 3 8% 5% 5% 5% 4 5% 6% 39%	3075
January	1st to 10th	Night	15% 7% 3 7% 4 3 3 3 4 5% 45%	4108
	11th to 20th	Night	16% 6% 2 4 3 3 3 2 4 4 53%	4120
	21st to end	Night	24% 7% 1 3 2 3 3 2 3 4 48%	4532
February	1st to 10th	Night	19% 8% 3 6% 3 3 3 3 4 6% 43%	2470
	11th to 20th	Night	17% 8% 3 6% 3 3 3 2 4 5% 45%	2286
	21st to end	Night	18% 8% 2 4 3 3 3 3 5% 4 47%	1841
March	1st to 10th	Night	20% 7% 3 6% 4 3 3 3 5% 5% 41%	3419
	11th to 20th	Night	15% 7% 2 6% 3 3 3 2 4 5% 51%	3480
	21st to end	Night	12% 6% 3 7% 5% 4 4 3 5% 8% 44%	3817
April	1st to 10th	Night	11% 6% 2 5% 4 3 3 3 5% 7% 51%	1907
	11th to 20th	Night	12% 5% 2 4 3 4 4 4 5% 7% 51%	1875
	21st to end	Night	13% 6% 1 7% 4 3 3 4 4 6% 48%	1900
May	1st to 10th	Night	14% 7% 3 7% 5% 4 5% 4 5% 8% 40%	3130
	11th to 20th	Night	13% 7% 3 6% 4 3 4 3 5% 7% 44%	2833
	21st to end	Night	13% 7% 2 6% 5% 5% 4 3 6% 7% 41%	3090
June	1st to 10th	Night	5% 5% 1 4 4 4 4 3 6% 10% 54%	1582
	11th to 20th	Night	3 4 2 3 3 3 4 4 4 9% 59%	1520
	21st to end	Night	3 3 1 4 3 3 3 4 6% 9% 61%	1699
July	1st to 10th	Night	7% 4 2 5% 4 4 4 4 6% 10% 48%	2850
	11th to 20th	Night	5% 3 1 4 3 3 4 3 6% 9% 59%	2850
	21st to end	Night	7% 7% 3 8% 5% 5% 5% 4 7% 9% 42%	3098
August	1st to 10th	Night	3 2 1 3 3 3 3 3 5% 8% 68%	2836
	11th to 20th	Night	4 3 1 4 3 4 4 4 6% 10% 56%	3063
	21st to end	Night	3 2 1 4 4 4 5% 4 7% 9% 57%	3476
September	1st to 10th	Night	7% 4 2 5% 3 4 4 3 5% 6% 57%	1900
	11th to 20th	Night	11% 5% 2 5% 3 4 4 3 5% 7% 52%	1900
	21st to end	Night	8% 4 2 4 3 3 2 3 6% 7% 58%	2177
October	1st to 10th	Night	8% 3 1 4 3 3 3 3 4 6% 62%	2280
	11th to 20th	Night	10% 4 2 4 3 2 3 2 3 5% 62%	2280
	21st to end	Night	17% 5% 1 4 4 3 3 2 3 4 55%	2508
November	1st to 10th	Night	11% 4 2 5% 3 3 3 2 5% 5% 57%	2280
	11th to 20th	Night	11% 4 1 3 3 3 3 3 4 7% 57%	2331
	21st to end	Night	13% 6% 2 5% 4 3 3 3 4 5% 51%	2522
December	1st to 10th	Night	17% 5% 2 5% 4 4 3 3 5% 5% 46%	2660
	11th to 20th	Night	15% 6% 2 6% 4 4 3 3 3 4 49%	3279
	21st to end	Night	14% 7% 3 6% 5% 4 4 3 4 6% 44%	4587

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	44% 3 5% 25% 20% 4	2848
	11th to 20th	Day	40% 3 10% 22% 22% 3	2850
	21st to end	Day	45% 3 6% 17% 23% 7%	3135
February	1st to 10th	Day	45% 4 9% 21% 16% 4	1710
	11th to 20th	Day	45% 4 6% 20% 19% 5%	1788
	21st to end	Day	50% 4 7% 15% 16% 8%	1627
March	1st to 10th	Day	49% 4 7% 13% 18% 10%	3436
	11th to 20th	Day	40% 4 9% 23% 19% 4	3480
	21st to end	Day	45% 4 8% 21% 20% 1	3814
April	1st to 10th	Day	37% 6% 9% 22% 21% 5%	2271
	11th to 20th	Day	41% 5% 9% 22% 17% 7%	2254
	21st to end	Day	43% 6% 9% 20% 20% 2	2280
May	1st to 10th	Day	45% 7% 11% 21% 15% 2	3800
	11th to 20th	Day	37% 8% 12% 27% 16% 1	4072
	21st to end	Day	45% 9% 11% 21% 12% 2	4489
June	1st to 10th	Day	35% 8% 14% 24% 16% 2	2589
	11th to 20th	Day	29% 8% 14% 28% 19% 2	2656
	21st to end	Day	29% 8% 11% 28% 20% 4	2470
July	1st to 10th	Day	34% 10% 14% 29% 12% 1	4056
	11th to 20th	Day	27% 6% 9% 32% 23% 3	4051
	21st to end	Day	46% 8% 14% 23% 9%	4325
August	1st to 10th	Day	20% 6% 15% 30% 23% 6%	4090
	11th to 20th	Day	36% 7% 13% 31% 11% 1	3801
	21st to end	Day	28% 7% 12% 31% 19% 3	4179
September	1st to 10th	Day	36% 8% 10% 20% 19% 8%	2280
	11th to 20th	Day	37% 6% 11% 18% 23% 5%	2277
	21st to end	Day	32% 5% 7% 21% 26% 8%	1981
October	1st to 10th	Day	16% 3 5% 13% 37% 26%	3160
	11th to 20th	Day	19% 2 3 20% 38% 18%	3140
	21st to end	Day	31% 4 5% 28% 26% 6%	3428
November	1st to 10th	Day	31% 4 8% 27% 23% 8%	1898
	11th to 20th	Day	29% 4 9% 21% 28% 9%	1844
	21st to end	Day	43% 3 6% 18% 24% 6%	1654
December	1st to 10th	Day	42% 3 8% 24% 18% 6%	1520
	11th to 20th	Day	44% 3 6% 20% 22% 5%	1915
	21st to end	Day	44% 5% 9% 18% 18% 6%	3075
January	1st to 10th	Night	42% 3 5% 19% 28% 3	4108
	11th to 20th	Night	36% 4 10% 21% 25% 5%	4120
	21st to end	Night	42% 3 9% 18% 23% 4	4532
February	1st to 10th	Night	45% 3 8% 20% 19% 6%	2470
	11th to 20th	Night	43% 3 6% 21% 21% 6%	2287
	21st to end	Night	41% 3 8% 17% 21% 9%	1841
March	1st to 10th	Night	43% 6% 8% 13% 18% 11%	3419
	11th to 20th	Night	37% 4 8% 26% 19% 6%	3480
	21st to end	Night	39% 5% 8% 25% 21% 2	3817
April	1st to 10th	Night	33% 4 11% 22% 20% 10%	1907
	11th to 20th	Night	32% 5% 8% 23% 22% 9%	1875
	21st to end	Night	36% 4 10% 25% 21% 3	1900
May	1st to 10th	Night	43% 7% 10% 23% 14% 3	3160
	11th to 20th	Night	39% 6% 13% 27% 14% 1	2834
	21st to end	Night	40% 7% 14% 23% 13% 3	3099
June	1st to 10th	Night	24% 7% 15% 31% 20% 2	1582
	11th to 20th	Night	23% 5% 12% 31% 27% 3	1520
	21st to end	Night	19% 7% 13% 30% 24% 7%	1699
July	1st to 10th	Night	30% 8% 16% 29% 16% 1	2805
	11th to 20th	Night	21% 6% 12% 33% 24% 3	2796
	21st to end	Night	38% 8% 13% 26% 15%	2999
August	1st to 10th	Night	15% 5% 16% 33% 26% 5%	2826
	11th to 20th	Night	22% 6% 18% 37% 15% 2	3093
	21st to end	Night	22% 6% 13% 30% 26% 3	3476
September	1st to 10th	Night	27% 6% 10% 26% 21% 9%	1900
	11th to 20th	Night	31% 7% 9% 21% 26% 6%	1900
	21st to end	Night	25% 4 11% 21% 29% 9%	2177
October	1st to 10th	Night	16% 3 7% 15% 29% 31%	3800
	11th to 20th	Night	16% 2 4 15% 38% 24%	3779
	21st to end	Night	28% 3 5% 22% 29% 13%	4120
November	1st to 10th	Night	30% 4 7% 23% 25% 11%	2280
	11th to 20th	Night	29% 4 5% 24% 28% 10%	2331
	21st to end	Night	36% 4 7% 20% 28% 6%	2522
December	1st to 10th	Night	40% 3 9% 20% 21% 7%	2660
	11th to 20th	Night	40% 3 5% 21% 25% 6%	3281
	21st to end	Night	41% 5% 8% 23% 20% 4	4587

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	27% 15% 33% 19% 5% 1	270
	11th to 20th	Day	26% 21% 36% 16% 2	270
	21st to end	Day	19% 26% 33% 16% 6%	297
February	1st to 10th	Day	27% 19% 33% 17% 4	270
	11th to 20th	Day	27% 26% 29% 14% 4	270
	21st to end	Day	34% 25% 30% 9% 2	225
March	1st to 10th	Day	23% 22% 31% 19% 6%	270
	11th to 20th	Day	26% 26% 34% 14% 1	270
	21st to end	Day	26% 22% 35% 13% 4	297
April	1st to 10th	Day	19% 18% 34% 20% 7% 1	451
	11th to 20th	Day	21% 20% 30% 21% 7%	452
	21st to end	Day	20% 15% 33% 21% 10% 1	460
May	1st to 10th	Day	17% 16% 29% 28% 10% 1	463
	11th to 20th	Day	14% 7% 26% 31% 19% 3	661
	21st to end	Day	8% 8% 25% 33% 21% 5%	734
June	1st to 10th	Day	10% 4 19% 30% 28% 8%	680
	11th to 20th	Day	5% 2 16% 38% 31% 8%	680
	21st to end	Day	4 3 17% 37% 28% 10%	680
July	1st to 10th	Day	5% 4 11% 32% 36% 12%	671
	11th to 20th	Day	4 2 12% 33% 33% 16%	668
	21st to end	Day	8% 3 8% 32% 34% 15%	739
August	1st to 10th	Day	6% 1 11% 36% 36% 10%	676
	11th to 20th	Day	14% 3 8% 29% 35% 11%	503
	21st to end	Day	10% 2 6% 24% 38% 20%	539
September	1st to 10th	Day	11% 2 10% 27% 37% 13%	490
	11th to 20th	Day	12% 2 14% 24% 36% 12%	487
	21st to end	Day	12% 6% 19% 35% 21% 7%	300
October	1st to 10th	Day	7% 4 25% 35% 24% 5%	300
	11th to 20th	Day	13% 11% 32% 26% 15% 2	300
	21st to end	Day	25% 14% 29% 22% 9% 1	330
November	1st to 10th	Day	16% 13% 32% 22% 15% 2	282
	11th to 20th	Day	11% 18% 35% 27% 8% 1	270
	21st to end	Day	24% 18% 26% 23% 9% 1	270
December	1st to 10th	Day	22% 20% 31% 17% 9% 1	270
	11th to 20th	Day	25% 17% 31% 19% 8%	270
	21st to end	Day	19% 23% 37% 17% 4	297
January	1st to 10th	Night	21% 13% 34% 28% 5%	950
	11th to 20th	Night	20% 15% 35% 25% 4	950
	21st to end	Night	20% 12% 38% 26% 4	1045
February	1st to 10th	Night	22% 14% 34% 26% 4	950
	11th to 20th	Night	21% 13% 41% 24% 1	811
	21st to end	Night	23% 16% 38% 20% 2	585
March	1st to 10th	Night	19% 10% 36% 31% 4	570
	11th to 20th	Night	20% 13% 34% 28% 5%	570
	21st to end	Night	15% 12% 38% 28% 7%	627
April	1st to 10th	Night	16% 12% 36% 30% 6%	570
	11th to 20th	Night	15% 11% 38% 27% 9% 1	563
	21st to end	Night	13% 10% 38% 29% 9%	570
May	1st to 10th	Night	14% 6% 27% 44% 9%	570
	11th to 20th	Night	15% 7% 27% 32% 18% 2	561
	21st to end	Night	9% 4 22% 38% 24% 4	617
June	1st to 10th	Night	5% 2 14% 40% 35% 5%	570
	11th to 20th	Night	3 1 10% 47% 35% 3	570
	21st to end	Night	4 1 11% 41% 38% 5%	570
July	1st to 10th	Night	4 1 8% 40% 41% 6%	555
	11th to 20th	Night	4 1 8% 36% 45% 7%	552
	21st to end	Night	4 1 8% 36% 43% 8%	624
August	1st to 10th	Night	4 1 5% 39% 44% 6%	567
	11th to 20th	Night	7% 1 8% 37% 40% 6%	564
	21st to end	Night	6% 1 9% 32% 47% 6%	627
September	1st to 10th	Night	7% 1 8% 38% 41% 4	570
	11th to 20th	Night	13% 1 10% 35% 38% 3	570
	21st to end	Night	9% 3 15% 34% 35% 4	659
October	1st to 10th	Night	9% 2 17% 36% 32% 3	760
	11th to 20th	Night	12% 6% 27% 38% 17% 1	760
	21st to end	Night	18% 8% 27% 32% 15% 1	836
November	1st to 10th	Night	13% 7% 25% 41% 14% 1	760
	11th to 20th	Night	13% 11% 30% 36% 11%	760
	21st to end	Night	15% 13% 30% 30% 11%	812
December	1st to 10th	Night	21% 9% 34% 31% 6%	950
	11th to 20th	Night	23% 11% 27% 33% 6%	950
	21st to end	Night	20% 15% 31% 29% 4	1045

Page generated at 2024-11-03 01:11:29. Version ac07

Copyright © 2024 Attilla Danko.