Red River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red River Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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	13% 6% 2 6% 4 4 4 3 5% 7% 47%	101640
	Night	13% 5% 2 5% 3 3 3 3 5% 6% 52%	98554
Transparency	Day	36% 5% 10% 23% 20% 6%	105303
	Night	32% 4 9% 22% 23% 9%	103017
Seeing	Day	14% 6% 20% 27% 24% 9%	15390
	Night	14% 6% 24% 34% 20% 2	25276

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	18% 6% 2 6% 4 4 3 2 3 4 48%	2847
	11th to 20th	Day	13% 6% 2 4 2 2 3 2 4 4 58%	2850
	21st to end	Day	23% 8% 3 6% 3 2 3 2 3 3 44%	3135
February	1st to 10th	Day	22% 9% 2 7% 4 4 3 2 3 4 40%	1710
	11th to 20th	Day	20% 7% 3 6% 4 4 3 3 4 4 43%	1780
	21st to end	Day	26% 8% 1 5% 2 2 4 2 3 5% 43%	1714
March	1st to 10th	Day	18% 8% 2 7% 4 3 3 3 4 6% 43%	3436
	11th to 20th	Day	17% 7% 3 7% 4 5% 4 3 5% 6% 39%	3480
	21st to end	Day	18% 8% 3 7% 4 4 4 3 4 6% 39%	3814
April	1st to 10th	Day	14% 7% 2 7% 4 4 3 2 5% 6% 46%	2131
	11th to 20th	Day	17% 6% 2 5% 4 4 3 3 5% 6% 44%	2254
	21st to end	Day	15% 7% 2 6% 4 4 4 4 5% 6% 44%	2280
May	1st to 10th	Day	20% 8% 2 7% 5% 5% 4 3 5% 7% 36%	4018
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 5% 7% 43%	4082
	21st to end	Day	18% 8% 3 8% 5% 4 4 4 5% 7% 35%	4477
June	1st to 10th	Day	7% 4 2 6% 4 5% 5% 5% 6% 10% 45%	2470
	11th to 20th	Day	7% 5% 2 6% 5% 5% 5% 5% 6% 8% 46%	2470
	21st to end	Day	5% 4 2 4 4 4 5% 5% 7% 10% 51%	2470
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	4120
	11th to 20th	Day	4 3 1 4 3 3 5% 4 6% 9% 57%	4120
	21st to end	Day	10% 7% 3 9% 5% 5% 5% 5% 6% 9% 36%	4465
August	1st to 10th	Day	3 2 1 3 3 3 4 4 5% 8% 65%	4104
	11th to 20th	Day	5% 4 2 5% 4 4 4 5% 7% 9% 53%	3959
	21st to end	Day	5% 4 2 5% 5% 6% 6% 5% 7% 10% 46%	4180
September	1st to 10th	Day	10% 5% 3 6% 3 4 5% 3 5% 5% 51%	2204
	11th to 20th	Day	11% 5% 2 6% 5% 4 4 4 6% 7% 47%	2090
	21st to end	Day	9% 4 1 4 4 4 4 3 5% 6% 57%	2090
October	1st to 10th	Day	8% 3 1 4 3 3 4 4 5% 6% 59%	1919
	11th to 20th	Day	14% 5% 1 4 3 2 3 2 2 4 59%	1900
	21st to end	Day	17% 5% 2 5% 3 3 4 2 4 4 53%	2090
November	1st to 10th	Day	13% 7% 2 5% 3 4 4 3 4 7% 50%	1958
	11th to 20th	Day	12% 5% 2 5% 4 3 3 2 3 5% 57%	2000
	21st to end	Day	17% 8% 2 4 3 2 2 2 3 5% 51%	1810
December	1st to 10th	Day	18% 5% 2 5% 3 3 3 3 4 5% 49%	1800
	11th to 20th	Day	17% 8% 2 7% 4 3 4 3 4 6% 42%	2251
	21st to end	Day	19% 9% 3 6% 3 3 3 2 4 5% 44%	3162
January	1st to 10th	Night	16% 8% 2 5% 3 2 3 2 4 5% 50%	4108
	11th to 20th	Night	16% 6% 1 3 3 2 2 2 3 4 57%	4120
	21st to end	Night	24% 6% 2 5% 3 2 3 2 3 3 46%	4532
February	1st to 10th	Night	19% 6% 2 5% 3 3 3 3 3 5% 47%	2470
	11th to 20th	Night	19% 7% 2 4 3 3 3 4 3 4 47%	2302
	21st to end	Night	18% 7% 2 4 3 3 2 2 3 4 50%	1738
March	1st to 10th	Night	20% 8% 3 7% 4 3 3 2 4 6% 40%	3419
	11th to 20th	Night	15% 8% 2 6% 4 3 4 3 4 6% 45%	3480
	21st to end	Night	15% 6% 2 6% 4 4 3 3 5% 6% 45%	3817
April	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 5% 6% 50%	2047
	11th to 20th	Night	13% 6% 2 4 4 4 4 3 5% 7% 49%	1875
	21st to end	Night	12% 5% 2 5% 4 2 3 3 4 7% 52%	1900
May	1st to 10th	Night	16% 7% 3 8% 4 4 4 3 5% 7% 38%	2869
	11th to 20th	Night	13% 6% 2 6% 4 3 4 3 6% 8% 46%	2823
	21st to end	Night	14% 7% 3 6% 4 5% 4 4 5% 8% 42%	3090
June	1st to 10th	Night	5% 4 2 5% 4 4 3 3 6% 10% 55%	1710
	11th to 20th	Night	5% 3 1 4 3 3 3 3 6% 9% 61%	1710
	21st to end	Night	4 3 1 3 3 3 4 3 6% 10% 61%	1710
July	1st to 10th	Night	8% 3 2 4 3 4 4 4 7% 11% 50%	2850
	11th to 20th	Night	5% 3 1 4 3 2 2 3 5% 11% 62%	2850
	21st to end	Night	6% 5% 2 6% 4 5% 5% 4 7% 9% 46%	3098
August	1st to 10th	Night	2 2 1 2 2 2 2 2 4 8% 73%	2836
	11th to 20th	Night	4 2 1 3 2 3 3 4 6% 12% 60%	2877
	21st to end	Night	3 3 1 5% 4 4 5% 5% 7% 9% 55%	3476
September	1st to 10th	Night	6% 5% 2 5% 4 3 3 3 5% 8% 56%	1970
	11th to 20th	Night	11% 4 1 4 4 4 4 4 5% 7% 52%	2090
	21st to end	Night	7% 3 1 4 3 3 3 2 5% 6% 63%	2090
October	1st to 10th	Night	7% 3 1 4 3 2 3 2 4 6% 64%	2240
	11th to 20th	Night	12% 4 1 3 3 2 2 2 4 5% 61%	2280
	21st to end	Night	16% 5% 2 4 3 2 2 2 3 4 59%	2508
November	1st to 10th	Night	13% 5% 1 4 4 2 3 2 4 5% 57%	2340
	11th to 20th	Night	10% 6% 2 5% 3 3 2 2 4 5% 59%	2400
	21st to end	Night	15% 5% 2 5% 3 3 3 2 3 5% 53%	2585
December	1st to 10th	Night	15% 6% 3 5% 2 3 3 3 5% 5% 50%	2600
	11th to 20th	Night	16% 7% 2 5% 4 4 3 2 4 4 48%	3166
	21st to end	Night	17% 7% 2 5% 3 2 3 2 4 5% 49%	4578

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	42% 2 6% 22% 24% 4	2848
	11th to 20th	Day	31% 3 9% 28% 25% 4	2850
	21st to end	Day	47% 3 4 17% 21% 9%	3135
February	1st to 10th	Day	50% 3 6% 17% 18% 6%	1710
	11th to 20th	Day	46% 3 6% 20% 19% 6%	1789
	21st to end	Day	47% 2 5% 15% 23% 8%	1714
March	1st to 10th	Day	43% 4 8% 14% 23% 8%	3436
	11th to 20th	Day	45% 5% 10% 19% 17% 4	3480
	21st to end	Day	46% 5% 9% 20% 18% 2	3814
April	1st to 10th	Day	41% 3 8% 22% 18% 8%	2131
	11th to 20th	Day	41% 4 9% 19% 19% 7%	2254
	21st to end	Day	40% 5% 9% 21% 21% 4	2280
May	1st to 10th	Day	47% 6% 9% 24% 11% 2	4055
	11th to 20th	Day	39% 7% 10% 23% 20% 1	4086
	21st to end	Day	48% 7% 12% 19% 12% 3	4489
June	1st to 10th	Day	33% 8% 13% 28% 15% 2	2470
	11th to 20th	Day	34% 8% 13% 24% 19% 2	2470
	21st to end	Day	26% 8% 13% 32% 19% 2	2470
July	1st to 10th	Day	35% 8% 20% 26% 10% 1	4056
	11th to 20th	Day	23% 6% 12% 36% 23% 1	4051
	21st to end	Day	42% 7% 14% 27% 10%	4325
August	1st to 10th	Day	17% 5% 13% 30% 27% 8%	4090
	11th to 20th	Day	26% 6% 19% 36% 11% 2	3998
	21st to end	Day	30% 9% 15% 30% 14% 2	4179
September	1st to 10th	Day	35% 6% 10% 20% 20% 10%	2204
	11th to 20th	Day	34% 7% 11% 21% 20% 7%	2090
	21st to end	Day	28% 5% 11% 20% 25% 12%	2090
October	1st to 10th	Day	16% 3 7% 11% 30% 33%	3192
	11th to 20th	Day	21% 2 4 18% 34% 22%	3140
	21st to end	Day	29% 3 5% 28% 27% 8%	3428
November	1st to 10th	Day	35% 4 8% 21% 23% 9%	1958
	11th to 20th	Day	32% 3 7% 20% 29% 10%	2000
	21st to end	Day	38% 2 6% 18% 28% 8%	1810
December	1st to 10th	Day	38% 4 9% 23% 20% 6%	1800
	11th to 20th	Day	44% 4 5% 18% 22% 7%	2249
	21st to end	Day	44% 3 6% 18% 23% 6%	3162
January	1st to 10th	Night	37% 4 6% 17% 31% 5%	4108
	11th to 20th	Night	33% 3 9% 20% 27% 8%	4120
	21st to end	Night	44% 3 7% 14% 23% 9%	4532
February	1st to 10th	Night	41% 4 7% 19% 20% 9%	2470
	11th to 20th	Night	42% 3 7% 17% 23% 8%	2303
	21st to end	Night	40% 3 7% 16% 23% 12%	1738
March	1st to 10th	Night	47% 3 6% 14% 17% 12%	3419
	11th to 20th	Night	40% 5% 8% 21% 16% 10%	3480
	21st to end	Night	39% 4 9% 19% 25% 3	3817
April	1st to 10th	Night	35% 5% 9% 19% 19% 12%	2047
	11th to 20th	Night	35% 5% 8% 20% 21% 11%	1875
	21st to end	Night	32% 5% 10% 24% 24% 4	1900
May	1st to 10th	Night	44% 8% 9% 21% 14% 5%	2896
	11th to 20th	Night	35% 7% 12% 24% 19% 2	2824
	21st to end	Night	39% 8% 14% 21% 12% 6%	3099
June	1st to 10th	Night	25% 7% 13% 29% 22% 4	1710
	11th to 20th	Night	21% 5% 12% 35% 22% 5%	1710
	21st to end	Night	19% 7% 13% 30% 28% 4	1710
July	1st to 10th	Night	26% 7% 20% 30% 15% 1	2805
	11th to 20th	Night	19% 5% 11% 38% 24% 4	2796
	21st to end	Night	32% 7% 16% 28% 15% 1	2999
August	1st to 10th	Night	11% 4 14% 27% 38% 7%	2826
	11th to 20th	Night	18% 5% 17% 37% 20% 4	2904
	21st to end	Night	23% 7% 14% 28% 24% 2	3476
September	1st to 10th	Night	27% 6% 11% 22% 23% 12%	1970
	11th to 20th	Night	31% 6% 10% 23% 21% 10%	2090
	21st to end	Night	23% 4 9% 22% 27% 15%	2090
October	1st to 10th	Night	14% 3 5% 14% 23% 41%	3734
	11th to 20th	Night	18% 2 4 15% 36% 26%	3779
	21st to end	Night	24% 3 5% 24% 28% 15%	4120
November	1st to 10th	Night	31% 4 8% 18% 26% 12%	2340
	11th to 20th	Night	29% 3 7% 18% 28% 14%	2400
	21st to end	Night	37% 2 6% 19% 27% 9%	2585
December	1st to 10th	Night	37% 4 9% 19% 22% 9%	2600
	11th to 20th	Night	42% 3 5% 17% 23% 11%	3167
	21st to end	Night	39% 3 7% 20% 24% 7%	4578

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	25% 9% 35% 26% 6%	270
	11th to 20th	Day	20% 17% 35% 21% 6% 1	270
	21st to end	Day	22% 14% 37% 18% 9%	297
February	1st to 10th	Day	28% 10% 37% 19% 6%	270
	11th to 20th	Day	26% 14% 37% 17% 5%	270
	21st to end	Day	36% 14% 37% 9% 3	225
March	1st to 10th	Day	21% 13% 36% 23% 6%	270
	11th to 20th	Day	21% 19% 35% 17% 7% 1	270
	21st to end	Day	20% 15% 38% 22% 4	297
April	1st to 10th	Day	19% 16% 35% 23% 7% 1	311
	11th to 20th	Day	23% 15% 28% 26% 8% 1	452
	21st to end	Day	18% 12% 32% 27% 9% 2	460
May	1st to 10th	Day	15% 9% 30% 34% 11% 1	614
	11th to 20th	Day	15% 6% 26% 32% 18% 3	675
	21st to end	Day	12% 6% 21% 37% 19% 6%	734
June	1st to 10th	Day	8% 2 13% 32% 35% 10%	680
	11th to 20th	Day	6% 3 12% 34% 36% 9%	680
	21st to end	Day	6% 1 12% 29% 35% 16%	680
July	1st to 10th	Day	8% 1 9% 28% 38% 16%	671
	11th to 20th	Day	4 1 6% 29% 41% 19%	668
	21st to end	Day	6% 2 5% 27% 41% 19%	739
August	1st to 10th	Day	4 2 6% 26% 47% 15%	676
	11th to 20th	Day	10% 1 5% 25% 46% 13%	622
	21st to end	Day	8% 1 4 19% 40% 27%	539
September	1st to 10th	Day	10% 1 6% 24% 38% 21%	414
	11th to 20th	Day	5% 1 9% 27% 35% 22%	300
	21st to end	Day	11% 2 13% 29% 25% 21%	300
October	1st to 10th	Day	5% 14% 40% 29% 11%	300
	11th to 20th	Day	13% 6% 27% 30% 17% 7%	300
	21st to end	Day	22% 9% 23% 24% 18% 3	330
November	1st to 10th	Day	16% 9% 29% 26% 16% 4	300
	11th to 20th	Day	15% 8% 30% 34% 12% 2	300
	21st to end	Day	21% 13% 27% 26% 11% 2	300
December	1st to 10th	Day	20% 9% 33% 27% 9% 2	300
	11th to 20th	Day	24% 11% 36% 19% 9% 1	300
	21st to end	Day	24% 12% 38% 19% 6% 2	306
January	1st to 10th	Night	20% 9% 31% 33% 7%	950
	11th to 20th	Night	21% 11% 35% 26% 8%	950
	21st to end	Night	20% 8% 35% 31% 6%	1045
February	1st to 10th	Night	23% 9% 33% 29% 5%	950
	11th to 20th	Night	24% 10% 35% 29% 3	828
	21st to end	Night	24% 13% 36% 24% 3	482
March	1st to 10th	Night	20% 11% 32% 31% 6%	570
	11th to 20th	Night	18% 11% 31% 35% 5% 1	570
	21st to end	Night	17% 10% 38% 29% 7%	627
April	1st to 10th	Night	13% 11% 38% 31% 7%	570
	11th to 20th	Night	15% 11% 36% 27% 12%	563
	21st to end	Night	14% 8% 38% 29% 11% 1	570
May	1st to 10th	Night	10% 7% 33% 40% 10% 1	570
	11th to 20th	Night	12% 5% 27% 37% 18% 2	561
	21st to end	Night	10% 5% 22% 39% 21% 3	617
June	1st to 10th	Night	6% 2 10% 41% 38% 3	570
	11th to 20th	Night	6% 1 11% 48% 31% 2	570
	21st to end	Night	3 1 9% 38% 42% 7%	570
July	1st to 10th	Night	5% 1 4 35% 49% 5%	555
	11th to 20th	Night	3 5% 36% 49% 7%	552
	21st to end	Night	4 5% 33% 48% 9%	624
August	1st to 10th	Night	3 1 4 35% 52% 5%	567
	11th to 20th	Night	7% 1 5% 32% 50% 5%	564
	21st to end	Night	5% 5% 36% 47% 7%	627
September	1st to 10th	Night	8% 2 7% 31% 47% 6%	570
	11th to 20th	Night	13% 9% 34% 41% 4	570
	21st to end	Night	8% 2 11% 39% 35% 4	570
October	1st to 10th	Night	8% 1 12% 45% 31% 3	720
	11th to 20th	Night	13% 4 21% 42% 18% 2	760
	21st to end	Night	17% 7% 25% 32% 17% 2	836
November	1st to 10th	Night	16% 3 23% 41% 15% 1	780
	11th to 20th	Night	13% 7% 28% 40% 12% 1	800
	21st to end	Night	18% 9% 29% 31% 13% 1	985
December	1st to 10th	Night	18% 8% 29% 38% 7%	1000
	11th to 20th	Night	22% 8% 29% 34% 7%	1000
	21st to end	Night	21% 9% 31% 31% 8%	1063

Page generated at 2024-12-21 03:13:48. Version ac07

Copyright © 2024 Attilla Danko.