Red Buttes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Buttes Observatory clear sky chart from 2005-11-06 to 2024-10-25.

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	3 6% 2 7% 5% 5% 5% 4 6% 8% 48%	101371
	Night	3 5% 2 6% 4 4 4 4 6% 8% 54%	97673
Transparency	Day	16% 50% 6% 13% 11% 5%	101114
	Night	14% 50% 7% 15% 11% 3	97520
Seeing	Day	12% 24% 32% 20% 9% 2	15656
	Night	8% 27% 32% 24% 9% 1	25645

By Month

Percentage Cloud Cover SW (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	3 3 8% 8% 5% 5% 3 5% 6% 53%	2538
	11th to 20th	Day	6% 4 10% 8% 6% 6% 4 6% 8% 41%	2571
	21st to end	Day	1 4 2 7% 4 4 4 4 6% 8% 57%	3146
February	1st to 10th	Day	1 6% 3 10% 7% 5% 5% 4 6% 7% 46%	1710
	11th to 20th	Day	1 6% 3 8% 6% 5% 7% 4 7% 8% 47%	1765
	21st to end	Day	1 6% 3 7% 5% 4 4 4 7% 8% 51%	1570
March	1st to 10th	Day	2 6% 4 8% 4 4 5% 5% 6% 8% 49%	3130
	11th to 20th	Day	2 9% 3 7% 4 5% 5% 4 7% 8% 45%	3486
	21st to end	Day	2 9% 3 9% 7% 6% 6% 5% 6% 9% 39%	4031
April	1st to 10th	Day	4 10% 2 6% 5% 5% 5% 4 6% 8% 45%	2280
	11th to 20th	Day	5% 12% 4 9% 6% 5% 5% 3 6% 8% 36%	2251
	21st to end	Day	6% 11% 4 8% 6% 4 5% 4 5% 7% 38%	2280
May	1st to 10th	Day	7% 14% 4 10% 6% 5% 5% 4 6% 7% 33%	4174
	11th to 20th	Day	7% 6% 2 6% 6% 6% 7% 6% 7% 7% 39%	4388
	21st to end	Day	5% 6% 2 6% 5% 5% 6% 5% 7% 8% 44%	4825
June	1st to 10th	Day	4 4 2 5% 4 5% 6% 5% 9% 10% 45%	2660
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 8% 50%	2660
	21st to end	Day	3 3 1 5% 5% 4 5% 6% 8% 8% 52%	2660
July	1st to 10th	Day	4 4 2 5% 4 5% 5% 5% 7% 8% 52%	4430
	11th to 20th	Day	2 3 1 5% 5% 5% 7% 5% 7% 9% 49%	4430
	21st to end	Day	4 4 2 6% 5% 5% 6% 5% 7% 9% 49%	4772
August	1st to 10th	Day	4 4 2 6% 5% 6% 6% 5% 9% 10% 43%	4092
	11th to 20th	Day	4 4 2 6% 5% 5% 6% 5% 6% 8% 49%	3827
	21st to end	Day	4 4 2 5% 4 5% 5% 4 6% 8% 54%	4180
September	1st to 10th	Day	4 5% 2 4 4 3 5% 4 4 8% 58%	2280
	11th to 20th	Day	4 4 2 4 3 3 5% 4 5% 7% 59%	2280
	21st to end	Day	5% 5% 2 5% 3 3 4 2 4 6% 62%	2063
October	1st to 10th	Day	6% 5% 2 6% 4 4 4 3 5% 6% 56%	1900
	11th to 20th	Day	4 6% 2 4 4 4 3 4 4 6% 59%	1900
	21st to end	Day	3 7% 3 6% 4 3 3 3 5% 5% 58%	1953
November	1st to 10th	Day	2 4 2 4 4 4 3 3 6% 9% 59%	1673
	11th to 20th	Day	2 7% 2 5% 3 3 3 3 6% 8% 57%	1706
	21st to end	Day	1 6% 3 7% 5% 4 5% 3 5% 7% 54%	1520
December	1st to 10th	Day	1 5% 3 7% 5% 4 5% 4 7% 8% 51%	1520
	11th to 20th	Day	2 5% 2 5% 4 4 4 3 7% 11% 52%	1926
	21st to end	Day	1 6% 4 11% 7% 5% 4 3 6% 6% 49%	2794
January	1st to 10th	Night	5% 3 11% 6% 4 4 3 5% 8% 51%	4417
	11th to 20th	Night	6% 4 10% 5% 4 5% 3 5% 8% 50%	4430
	21st to end	Night	1 6% 3 7% 4 4 5% 3 5% 7% 56%	4521
February	1st to 10th	Night	1 6% 3 9% 5% 4 4 3 5% 7% 52%	2470
	11th to 20th	Night	1 6% 3 7% 6% 5% 6% 4 6% 6% 50%	2301
	21st to end	Night	1 7% 3 8% 4 4 4 3 4 7% 56%	1884
March	1st to 10th	Night	1 5% 3 7% 4 4 5% 4 6% 7% 53%	3734
	11th to 20th	Night	2 9% 4 6% 4 4 4 3 5% 7% 52%	3490
	21st to end	Night	3 9% 3 8% 5% 4 5% 4 5% 7% 47%	3615
April	1st to 10th	Night	3 7% 2 6% 5% 4 4 3 6% 7% 51%	1900
	11th to 20th	Night	5% 10% 3 6% 5% 4 4 3 6% 7% 46%	1877
	21st to end	Night	7% 10% 3 7% 4 3 3 3 6% 6% 48%	1900
May	1st to 10th	Night	5% 9% 3 7% 5% 4 5% 4 5% 7% 46%	2777
	11th to 20th	Night	7% 5% 2 7% 4 5% 6% 4 7% 9% 45%	2517
	21st to end	Night	5% 5% 2 4 4 4 5% 4 7% 7% 53%	2762
June	1st to 10th	Night	3 2 1 3 3 4 4 5% 7% 11% 54%	1520
	11th to 20th	Night	4 3 1 4 3 3 5% 4 6% 8% 60%	1520
	21st to end	Night	3 3 2 4 3 4 3 3 5% 9% 60%	1520
July	1st to 10th	Night	3 3 2 4 4 4 4 4 6% 8% 58%	2540
	11th to 20th	Night	2 2 1 3 3 5% 5% 6% 8% 10% 55%	2540
	21st to end	Night	2 2 1 5% 4 4 5% 5% 7% 9% 58%	2787
August	1st to 10th	Night	3 3 1 5% 4 5% 5% 5% 8% 11% 50%	2847
	11th to 20th	Night	2 4 2 6% 4 4 5% 5% 8% 10% 50%	3012
	21st to end	Night	3 3 2 4 3 3 4 4 7% 9% 58%	3487
September	1st to 10th	Night	5% 4 2 4 3 3 4 3 5% 8% 59%	1900
	11th to 20th	Night	3 4 1 4 3 3 5% 3 4 6% 64%	1900
	21st to end	Night	5% 3 1 4 3 3 4 3 5% 6% 63%	2113
October	1st to 10th	Night	4 5% 2 4 4 4 3 5% 6% 7% 56%	2280
	11th to 20th	Night	4 4 2 4 2 4 4 2 5% 7% 63%	2280
	21st to end	Night	4 8% 2 5% 3 4 3 3 4 7% 57%	2490
November	1st to 10th	Night	3 5% 1 4 3 3 4 3 5% 8% 62%	2405
	11th to 20th	Night	2 6% 2 4 4 3 4 4 4 7% 59%	2473
	21st to end	Night	2 6% 3 6% 4 3 4 3 7% 8% 55%	2660
December	1st to 10th	Night	1 5% 3 6% 4 4 4 4 5% 7% 57%	2660
	11th to 20th	Night	1 5% 3 5% 4 4 4 4 6% 10% 54%	3271
	21st to end	Night	1 7% 3 9% 5% 4 4 4 6% 8% 48%	4873

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	19% 45% 7% 10% 17% 2	2539
	11th to 20th	Day	23% 47% 12% 9% 7% 2	2571
	21st to end	Day	11% 41% 13% 21% 11% 2	3146
February	1st to 10th	Day	12% 65% 7% 7% 6% 2	1710
	11th to 20th	Day	7% 66% 4 13% 7% 2	1774
	21st to end	Day	10% 66% 3 11% 9% 1	1570
March	1st to 10th	Day	17% 44% 4 22% 11% 2	3130
	11th to 20th	Day	21% 43% 11% 19% 4 1	3486
	21st to end	Day	22% 45% 8% 22% 3 1	4031
April	1st to 10th	Day	11% 67% 5% 12% 5% 1	2280
	11th to 20th	Day	16% 68% 3 8% 6% 1	2254
	21st to end	Day	18% 66% 3 10% 4	2280
May	1st to 10th	Day	29% 45% 4 9% 10% 4	4174
	11th to 20th	Day	20% 45% 7% 17% 10% 1	4392
	21st to end	Day	18% 43% 5% 16% 14% 3	4825
June	1st to 10th	Day	9% 67% 6% 9% 7% 2	2660
	11th to 20th	Day	11% 66% 4 9% 7% 2	2660
	21st to end	Day	11% 65% 4 10% 8% 2	2660
July	1st to 10th	Day	13% 37% 6% 9% 20% 14%	4361
	11th to 20th	Day	18% 39% 6% 13% 13% 11%	4355
	21st to end	Day	16% 37% 6% 10% 16% 15%	4621
August	1st to 10th	Day	19% 42% 8% 16% 9% 6%	4078
	11th to 20th	Day	18% 41% 8% 10% 18% 6%	3865
	21st to end	Day	15% 39% 7% 11% 17% 11%	4179
September	1st to 10th	Day	11% 60% 3 9% 12% 4	2280
	11th to 20th	Day	8% 60% 3 10% 14% 4	2280
	21st to end	Day	10% 60% 3 7% 15% 5%	2063
October	1st to 10th	Day	11% 60% 4 10% 10% 5%	1900
	11th to 20th	Day	8% 59% 4 11% 14% 5%	1900
	21st to end	Day	11% 60% 4 14% 9% 3	1953
November	1st to 10th	Day	8% 60% 5% 15% 10% 2	1673
	11th to 20th	Day	8% 60% 3 16% 10% 2	1706
	21st to end	Day	14% 60% 4 11% 9% 2	1520
December	1st to 10th	Day	11% 63% 7% 11% 7% 1	1520
	11th to 20th	Day	12% 49% 6% 21% 10% 1	1924
	21st to end	Day	21% 40% 4 16% 13% 6%	2794
January	1st to 10th	Night	21% 41% 7% 20% 9% 2	4417
	11th to 20th	Night	19% 43% 14% 9% 10% 5%	4430
	21st to end	Night	15% 41% 15% 19% 8% 2	4521
February	1st to 10th	Night	11% 66% 8% 8% 6% 1	2470
	11th to 20th	Night	8% 65% 5% 12% 7% 2	2302
	21st to end	Night	9% 65% 4 10% 10% 2	1884
March	1st to 10th	Night	15% 44% 4 21% 12% 3	3734
	11th to 20th	Night	19% 41% 9% 21% 9% 1	3490
	21st to end	Night	20% 43% 10% 23% 4 1	3615
April	1st to 10th	Night	10% 67% 6% 10% 7% 1	1900
	11th to 20th	Night	13% 66% 4 11% 5% 1	1877
	21st to end	Night	15% 66% 4 10% 5%	1900
May	1st to 10th	Night	21% 44% 3 14% 15% 3	2777
	11th to 20th	Night	19% 44% 9% 20% 6% 3	2518
	21st to end	Night	15% 42% 8% 18% 16%	2762
June	1st to 10th	Night	5% 66% 9% 10% 8% 2	1520
	11th to 20th	Night	8% 66% 5% 11% 7% 3	1520
	21st to end	Night	9% 63% 3 12% 9% 3	1520
July	1st to 10th	Night	15% 37% 5% 14% 18% 11%	2500
	11th to 20th	Night	13% 38% 8% 19% 15% 7%	2492
	21st to end	Night	13% 36% 6% 17% 16% 12%	2700
August	1st to 10th	Night	16% 40% 13% 15% 13% 3	2838
	11th to 20th	Night	19% 41% 12% 13% 10% 6%	3040
	21st to end	Night	14% 38% 10% 12% 21% 6%	3487
September	1st to 10th	Night	8% 60% 4 12% 11% 5%	1900
	11th to 20th	Night	7% 60% 4 12% 13% 5%	1900
	21st to end	Night	10% 60% 3 9% 13% 5%	2113
October	1st to 10th	Night	11% 60% 4 10% 10% 5%	2280
	11th to 20th	Night	6% 60% 3 13% 13% 6%	2280
	21st to end	Night	12% 61% 5% 12% 8% 2	2490
November	1st to 10th	Night	9% 59% 5% 14% 11% 2	2405
	11th to 20th	Night	9% 61% 4 14% 10% 3	2473
	21st to end	Night	13% 61% 5% 12% 8% 2	2660
December	1st to 10th	Night	10% 61% 7% 13% 8% 2	2660
	11th to 20th	Night	13% 49% 6% 21% 11% 1	3272
	21st to end	Night	19% 41% 5% 16% 15% 4	4873

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	16% 33% 29% 14% 6% 2	270
	11th to 20th	Day	16% 47% 24% 12% 1	270
	21st to end	Day	10% 45% 34% 8% 3	297
February	1st to 10th	Day	20% 52% 23% 5% 1	270
	11th to 20th	Day	19% 41% 32% 8%	270
	21st to end	Day	24% 41% 27% 8%	225
March	1st to 10th	Day	14% 43% 31% 10% 3	270
	11th to 20th	Day	15% 31% 37% 14% 2	456
	21st to end	Day	17% 35% 33% 12% 2	506
April	1st to 10th	Day	20% 35% 34% 9% 2	460
	11th to 20th	Day	22% 39% 27% 8% 3	452
	21st to end	Day	17% 31% 33% 14% 3 1	460
May	1st to 10th	Day	21% 25% 31% 15% 7% 1	596
	11th to 20th	Day	16% 19% 33% 21% 9% 2	675
	21st to end	Day	12% 20% 29% 25% 11% 2	734
June	1st to 10th	Day	6% 16% 30% 29% 16% 3	680
	11th to 20th	Day	9% 18% 40% 24% 8% 2	680
	21st to end	Day	4 16% 36% 26% 16% 2	680
July	1st to 10th	Day	6% 6% 28% 34% 23% 4	671
	11th to 20th	Day	4 7% 31% 34% 21% 3	668
	21st to end	Day	6% 6% 27% 34% 24% 4	721
August	1st to 10th	Day	9% 7% 41% 31% 9% 2	487
	11th to 20th	Day	7% 8% 35% 35% 12% 4	477
	21st to end	Day	7% 10% 37% 29% 13% 3	539
September	1st to 10th	Day	9% 14% 31% 30% 13% 3	490
	11th to 20th	Day	4 18% 41% 22% 12% 2	490
	21st to end	Day	7% 20% 33% 20% 15% 5%	304
October	1st to 10th	Day	9% 21% 30% 23% 12% 5%	300
	11th to 20th	Day	16% 28% 30% 17% 6% 3	300
	21st to end	Day	12% 37% 36% 12% 3 1	311
November	1st to 10th	Day	15% 35% 32% 11% 6% 1	270
	11th to 20th	Day	16% 41% 34% 7% 2	270
	21st to end	Day	13% 44% 30% 11% 2	270
December	1st to 10th	Day	18% 45% 28% 5% 4	270
	11th to 20th	Day	16% 52% 25% 7%	270
	21st to end	Day	20% 46% 23% 8% 2 1	297
January	1st to 10th	Night	10% 42% 30% 13% 5% 1	950
	11th to 20th	Night	8% 53% 25% 10% 4	950
	21st to end	Night	5% 47% 32% 12% 4	836
February	1st to 10th	Night	10% 48% 30% 8% 4	760
	11th to 20th	Night	7% 42% 33% 16% 1	744
	21st to end	Night	11% 45% 34% 10% 1	628
March	1st to 10th	Night	7% 36% 38% 16% 3	760
	11th to 20th	Night	8% 28% 37% 23% 5%	760
	21st to end	Night	10% 29% 39% 17% 5% 1	713
April	1st to 10th	Night	10% 27% 40% 19% 3	570
	11th to 20th	Night	12% 26% 39% 19% 4	563
	21st to end	Night	14% 21% 32% 25% 7% 1	570
May	1st to 10th	Night	12% 19% 35% 25% 9% 1	570
	11th to 20th	Night	12% 12% 32% 31% 12% 1	561
	21st to end	Night	7% 14% 33% 29% 16% 1	617
June	1st to 10th	Night	4 11% 31% 37% 16% 2	570
	11th to 20th	Night	6% 12% 39% 35% 9%	570
	21st to end	Night	5% 7% 30% 42% 16% 1	570
July	1st to 10th	Night	4 3 24% 47% 22% 1	555
	11th to 20th	Night	3 1 22% 49% 22% 2	552
	21st to end	Night	4 2 20% 47% 26% 2	624
August	1st to 10th	Night	4 3 22% 50% 20% 1	567
	11th to 20th	Night	4 3 22% 50% 19% 2	564
	21st to end	Night	4 3 24% 42% 25% 2	627
September	1st to 10th	Night	8% 5% 24% 43% 17% 3	570
	11th to 20th	Night	4 7% 28% 42% 16% 2	570
	21st to end	Night	6% 11% 31% 36% 15% 1	598
October	1st to 10th	Night	7% 19% 33% 28% 12% 1	760
	11th to 20th	Night	9% 25% 33% 23% 9% 1	760
	21st to end	Night	11% 26% 41% 16% 5% 1	866
November	1st to 10th	Night	8% 32% 39% 16% 5% 1	925
	11th to 20th	Night	12% 40% 35% 12% 1	950
	21st to end	Night	6% 39% 39% 14% 2	950
December	1st to 10th	Night	11% 45% 31% 11% 2	950
	11th to 20th	Night	8% 48% 30% 12% 2	950
	21st to end	Night	12% 48% 26% 10% 4	1045

Page generated at 2024-10-22 18:20:59. Version ac07

Copyright © 2024 Attilla Danko.