Darkfire Observatory
Clear Sky Chart
History

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

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% 7% 2 6% 4 4 4 4 6% 7% 44%	100874
	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	98323
Transparency	Day	39% 4 10% 24% 19% 4	104562
	Night	35% 3 9% 24% 22% 6%	102776
Seeing	Day	14% 7% 21% 25% 22% 11%	15345
	Night	15% 7% 24% 32% 19% 3	25108

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	14% 15% 4 6% 4 3 2 2 3 5% 43%	2623
	11th to 20th	Day	20% 8% 2 7% 4 3 3 2 4 4 44%	2850
	21st to end	Day	21% 11% 3 6% 4 3 2 2 3 5% 39%	3135
February	1st to 10th	Day	20% 9% 4 7% 5% 3 3 2 4 5% 39%	1850
	11th to 20th	Day	20% 9% 3 6% 4 3 4 3 4 6% 39%	1848
	21st to end	Day	23% 10% 3 6% 5% 3 4 2 4 5% 36%	1570
March	1st to 10th	Day	18% 12% 4 9% 4 4 4 3 4 4 35%	3138
	11th to 20th	Day	14% 7% 3 7% 4 4 5% 3 4 5% 44%	3480
	21st to end	Day	12% 7% 3 8% 5% 5% 5% 3 4 6% 41%	4059
April	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 5% 6% 45%	2280
	11th to 20th	Day	16% 6% 2 6% 4 3 4 3 5% 6% 45%	2254
	21st to end	Day	14% 7% 2 6% 5% 5% 4 3 6% 6% 43%	2280
May	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 4 6% 9% 39%	3765
	11th to 20th	Day	13% 7% 2 7% 4 4 4 4 6% 10% 39%	4010
	21st to end	Day	11% 6% 2 7% 6% 6% 6% 5% 7% 10% 35%	4690
June	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 8% 44%	2660
	11th to 20th	Day	4 5% 2 5% 5% 4 5% 5% 7% 10% 48%	2660
	21st to end	Day	4 3 2 5% 5% 5% 5% 5% 8% 10% 48%	2660
July	1st to 10th	Day	7% 5% 2 6% 6% 6% 6% 5% 8% 10% 39%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 8% 10% 40%	4288
	21st to end	Day	15% 8% 3 9% 6% 5% 5% 4 6% 7% 32%	4465
August	1st to 10th	Day	4 3 1 4 3 4 4 3 6% 9% 59%	3799
	11th to 20th	Day	7% 4 2 5% 4 5% 5% 5% 7% 9% 47%	3729
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 6% 8% 52%	4180
September	1st to 10th	Day	10% 4 2 6% 5% 5% 5% 4 6% 8% 45%	2280
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 6% 8% 45%	2218
	21st to end	Day	11% 5% 2 5% 4 2 3 3 4 8% 53%	2090
October	1st to 10th	Day	7% 3 1 5% 3 3 4 3 5% 5% 60%	1980
	11th to 20th	Day	12% 5% 2 4 2 2 4 3 5% 6% 56%	1900
	21st to end	Day	18% 6% 1 4 2 2 4 3 3 4 53%	2090
November	1st to 10th	Day	13% 6% 2 3 3 3 2 2 4 5% 57%	1791
	11th to 20th	Day	13% 5% 2 5% 4 3 3 3 5% 5% 53%	1710
	21st to end	Day	18% 7% 3 6% 4 3 4 3 5% 5% 44%	1710
December	1st to 10th	Day	20% 10% 3 5% 3 3 4 2 4 5% 39%	1691
	11th to 20th	Day	15% 7% 3 6% 5% 5% 4 3 3 6% 44%	1918
	21st to end	Day	13% 11% 3 8% 5% 5% 4 4 5% 6% 35%	2783
January	1st to 10th	Night	19% 8% 2 6% 4 3 3 2 4 4 44%	4328
	11th to 20th	Night	18% 7% 2 5% 4 3 3 3 4 4 46%	4120
	21st to end	Night	23% 8% 2 5% 2 2 2 2 3 5% 45%	4532
February	1st to 10th	Night	20% 9% 3 7% 4 3 3 3 3 5% 41%	2328
	11th to 20th	Night	18% 8% 3 8% 4 3 3 2 3 5% 42%	2218
	21st to end	Night	20% 8% 3 6% 4 4 4 2 4 5% 40%	1884
March	1st to 10th	Night	19% 10% 3 6% 4 4 3 3 4 5% 40%	3733
	11th to 20th	Night	14% 7% 2 6% 4 3 3 3 4 6% 49%	3490
	21st to end	Night	13% 6% 2 6% 5% 4 4 4 6% 7% 43%	3572
April	1st to 10th	Night	10% 6% 2 5% 3 4 5% 4 5% 7% 49%	1900
	11th to 20th	Night	15% 5% 2 4 3 3 3 3 4 7% 50%	1875
	21st to end	Night	11% 7% 2 6% 4 4 3 3 5% 7% 49%	1900
May	1st to 10th	Night	18% 7% 3 5% 3 4 3 3 5% 8% 40%	3130
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 6% 6% 46%	2881
	21st to end	Night	9% 6% 2 6% 6% 4 5% 4 8% 9% 40%	2868
June	1st to 10th	Night	8% 5% 2 6% 5% 5% 4 4 7% 9% 46%	1520
	11th to 20th	Night	3 3 1 3 3 3 4 4 7% 9% 61%	1520
	21st to end	Night	2 3 1 3 4 3 5% 6% 6% 12% 55%	1520
July	1st to 10th	Night	6% 4 2 5% 4 4 5% 4 7% 11% 49%	2530
	11th to 20th	Night	6% 4 1 4 4 4 5% 4 6% 10% 52%	2678
	21st to end	Night	12% 8% 2 8% 5% 4 4 3 6% 8% 41%	3098
August	1st to 10th	Night	2 2 1 3 2 3 3 3 5% 8% 69%	3130
	11th to 20th	Night	3 3 2 4 4 4 4 4 6% 11% 55%	3100
	21st to end	Night	4 3 1 4 4 3 4 4 7% 8% 58%	3476
September	1st to 10th	Night	7% 4 2 6% 4 3 4 4 6% 7% 52%	1900
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 51%	1943
	21st to end	Night	10% 4 2 4 3 4 3 3 4 5% 57%	2090
October	1st to 10th	Night	7% 4 1 4 2 3 3 2 5% 7% 63%	2195
	11th to 20th	Night	10% 4 2 4 3 3 3 3 3 6% 59%	2280
	21st to end	Night	17% 6% 2 5% 3 3 3 2 4 4 53%	2508
November	1st to 10th	Night	12% 4 2 3 3 4 3 3 4 6% 55%	2489
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 7% 53%	2470
	21st to end	Night	15% 6% 1 5% 4 3 3 3 4 7% 49%	2470
December	1st to 10th	Night	17% 9% 3 6% 3 3 3 2 3 6% 45%	2484
	11th to 20th	Night	16% 6% 2 5% 4 3 3 3 4 6% 47%	3279
	21st to end	Night	15% 8% 2 7% 5% 5% 5% 4 5% 7% 36%	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	47% 1 4 24% 20% 3	2624
	11th to 20th	Day	47% 2 6% 25% 19% 1	2850
	21st to end	Day	50% 2 6% 20% 20% 3	3135
February	1st to 10th	Day	50% 2 7% 23% 16% 2	1850
	11th to 20th	Day	49% 2 7% 19% 18% 5%	1858
	21st to end	Day	52% 2 8% 16% 17% 6%	1570
March	1st to 10th	Day	54% 2 7% 13% 15% 9%	3138
	11th to 20th	Day	44% 2 8% 24% 18% 4	3480
	21st to end	Day	46% 2 8% 23% 20% 1	4059
April	1st to 10th	Day	39% 4 8% 25% 20% 3	2280
	11th to 20th	Day	41% 3 7% 23% 20% 5%	2254
	21st to end	Day	42% 3 9% 26% 19% 1	2280
May	1st to 10th	Day	43% 4 11% 25% 15% 2	3800
	11th to 20th	Day	42% 3 17% 24% 13% 1	4014
	21st to end	Day	42% 4 12% 29% 10% 1	4703
June	1st to 10th	Day	36% 5% 13% 25% 19% 2	2660
	11th to 20th	Day	29% 6% 12% 30% 19% 3	2660
	21st to end	Day	29% 7% 14% 28% 19% 4	2660
July	1st to 10th	Day	37% 6% 15% 27% 13% 2	4371
	11th to 20th	Day	36% 6% 12% 33% 10% 3	4213
	21st to end	Day	52% 6% 11% 23% 7% 1	4325
August	1st to 10th	Day	22% 4 17% 30% 24% 3	3786
	11th to 20th	Day	31% 6% 17% 27% 18% 2	3765
	21st to end	Day	29% 6% 9% 28% 25% 3	4179
September	1st to 10th	Day	36% 6% 9% 25% 18% 6%	2280
	11th to 20th	Day	37% 5% 10% 19% 24% 5%	2218
	21st to end	Day	32% 3 8% 23% 26% 7%	2090
October	1st to 10th	Day	17% 3 5% 15% 34% 25%	3292
	11th to 20th	Day	19% 2 4 21% 38% 16%	3140
	21st to end	Day	27% 2 3 27% 31% 10%	3428
November	1st to 10th	Day	32% 2 6% 26% 25% 8%	1791
	11th to 20th	Day	34% 3 7% 23% 26% 7%	1710
	21st to end	Day	43% 3 7% 20% 23% 5%	1710
December	1st to 10th	Day	49% 2 7% 20% 18% 4	1691
	11th to 20th	Day	45% 2 6% 21% 23% 4	1915
	21st to end	Day	50% 3 8% 23% 14% 2	2783
January	1st to 10th	Night	46% 1 4 23% 23% 3	4328
	11th to 20th	Night	44% 2 7% 23% 20% 4	4120
	21st to end	Night	45% 1 6% 24% 20% 3	4532
February	1st to 10th	Night	48% 2 8% 18% 20% 3	2328
	11th to 20th	Night	47% 2 6% 21% 18% 6%	2219
	21st to end	Night	48% 2 7% 17% 19% 7%	1884
March	1st to 10th	Night	49% 2 8% 15% 17% 9%	3733
	11th to 20th	Night	38% 2 7% 24% 20% 8%	3490
	21st to end	Night	41% 3 9% 22% 23% 2	3572
April	1st to 10th	Night	35% 4 10% 24% 22% 5%	1900
	11th to 20th	Night	35% 3 7% 23% 24% 7%	1875
	21st to end	Night	37% 3 9% 26% 22% 4	1900
May	1st to 10th	Night	44% 2 12% 24% 14% 3	3160
	11th to 20th	Night	40% 3 14% 28% 14% 1	2882
	21st to end	Night	39% 5% 12% 28% 14% 2	2876
June	1st to 10th	Night	34% 6% 12% 23% 23% 2	1520
	11th to 20th	Night	19% 4 15% 31% 25% 5%	1520
	21st to end	Night	21% 6% 18% 28% 22% 5%	1520
July	1st to 10th	Night	29% 4 21% 29% 15% 2	2490
	11th to 20th	Night	27% 5% 13% 37% 14% 3	2630
	21st to end	Night	43% 6% 14% 25% 12% 1	2999
August	1st to 10th	Night	15% 4 11% 42% 26% 2	3119
	11th to 20th	Night	24% 4 20% 30% 19% 2	3130
	21st to end	Night	23% 5% 13% 27% 28% 4	3476
September	1st to 10th	Night	31% 4 10% 24% 23% 8%	1900
	11th to 20th	Night	32% 4 9% 22% 26% 6%	1943
	21st to end	Night	31% 2 9% 24% 26% 9%	2090
October	1st to 10th	Night	15% 2 5% 18% 32% 27%	3663
	11th to 20th	Night	18% 2 3 17% 35% 25%	3779
	21st to end	Night	26% 2 5% 27% 25% 15%	4120
November	1st to 10th	Night	32% 2 6% 24% 28% 8%	2489
	11th to 20th	Night	32% 3 6% 22% 26% 10%	2470
	21st to end	Night	37% 3 7% 21% 26% 6%	2470
December	1st to 10th	Night	44% 3 8% 23% 18% 5%	2484
	11th to 20th	Night	40% 3 6% 23% 24% 5%	3281
	21st to end	Night	48% 3 7% 21% 16% 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	23% 14% 38% 16% 8% 1	270
	11th to 20th	Day	26% 16% 34% 19% 4 1	270
	21st to end	Day	23% 14% 40% 19% 3 1	297
February	1st to 10th	Day	25% 12% 39% 15% 8% 1	270
	11th to 20th	Day	33% 17% 35% 12% 3 1	270
	21st to end	Day	36% 19% 31% 9% 5%	225
March	1st to 10th	Day	23% 15% 34% 20% 6% 1	270
	11th to 20th	Day	21% 19% 34% 23% 1	270
	21st to end	Day	21% 16% 33% 21% 8% 1	439
April	1st to 10th	Day	17% 17% 31% 24% 9% 1	460
	11th to 20th	Day	20% 12% 33% 23% 8% 3	452
	21st to end	Day	18% 11% 32% 22% 13% 4	460
May	1st to 10th	Day	17% 11% 26% 29% 16% 2	463
	11th to 20th	Day	14% 6% 23% 24% 24% 10%	487
	21st to end	Day	11% 3 20% 30% 24% 12%	652
June	1st to 10th	Day	10% 4 14% 26% 27% 19%	680
	11th to 20th	Day	5% 2 14% 31% 34% 15%	680
	21st to end	Day	5% 1 15% 32% 31% 15%	680
July	1st to 10th	Day	7% 2 9% 27% 30% 25%	671
	11th to 20th	Day	8% 2 9% 23% 37% 21%	668
	21st to end	Day	8% 2 9% 26% 35% 20%	739
August	1st to 10th	Day	7% 3 6% 29% 35% 19%	500
	11th to 20th	Day	10% 3 9% 29% 37% 13%	479
	21st to end	Day	10% 2 6% 18% 37% 27%	539
September	1st to 10th	Day	9% 2 8% 28% 34% 19%	490
	11th to 20th	Day	11% 2 11% 23% 32% 21%	490
	21st to end	Day	15% 4 14% 29% 25% 12%	490
October	1st to 10th	Day	7% 4 16% 34% 30% 10%	380
	11th to 20th	Day	10% 7% 35% 28% 15% 5%	300
	21st to end	Day	22% 8% 29% 28% 10% 3	330
November	1st to 10th	Day	18% 6% 25% 34% 14% 4	297
	11th to 20th	Day	8% 12% 38% 28% 13% 1	270
	21st to end	Day	23% 11% 29% 20% 14% 3	270
December	1st to 10th	Day	23% 15% 33% 20% 8% 2	270
	11th to 20th	Day	22% 12% 35% 20% 9% 1	270
	21st to end	Day	22% 16% 38% 18% 5% 1	297
January	1st to 10th	Night	24% 11% 34% 25% 5%	950
	11th to 20th	Night	25% 13% 33% 25% 3	950
	21st to end	Night	22% 10% 39% 27% 2	1045
February	1st to 10th	Night	24% 11% 34% 27% 4	808
	11th to 20th	Night	23% 13% 36% 24% 3	743
	21st to end	Night	24% 15% 35% 23% 2	628
March	1st to 10th	Night	20% 12% 32% 30% 6%	760
	11th to 20th	Night	24% 9% 34% 27% 5% 1	580
	21st to end	Night	18% 9% 33% 29% 11%	627
April	1st to 10th	Night	15% 11% 35% 31% 9% 1	570
	11th to 20th	Night	17% 9% 31% 31% 12% 1	563
	21st to end	Night	15% 5% 34% 32% 11% 2	570
May	1st to 10th	Night	15% 7% 22% 40% 14% 2	570
	11th to 20th	Night	13% 5% 20% 39% 19% 4	561
	21st to end	Night	7% 3 16% 41% 27% 6%	617
June	1st to 10th	Night	9% 2 12% 38% 33% 6%	570
	11th to 20th	Night	3 1 10% 39% 45% 3	570
	21st to end	Night	4 1 10% 41% 39% 5%	570
July	1st to 10th	Night	3 2 9% 33% 43% 10%	555
	11th to 20th	Night	6% 2 7% 30% 42% 13%	552
	21st to end	Night	6% 1 6% 31% 44% 12%	624
August	1st to 10th	Night	5% 5% 31% 51% 8%	567
	11th to 20th	Night	5% 2 6% 35% 45% 7%	564
	21st to end	Night	7% 2 6% 27% 48% 10%	627
September	1st to 10th	Night	7% 3 7% 35% 43% 5%	570
	11th to 20th	Night	13% 3 9% 31% 36% 8%	613
	21st to end	Night	11% 3 13% 34% 34% 4	760
October	1st to 10th	Night	8% 3 17% 35% 33% 4	760
	11th to 20th	Night	13% 5% 24% 38% 18% 2	760
	21st to end	Night	20% 4 24% 35% 16% 1	836
November	1st to 10th	Night	13% 6% 24% 37% 17% 2	779
	11th to 20th	Night	13% 7% 33% 35% 11% 1	760
	21st to end	Night	18% 8% 32% 30% 11% 1	760
December	1st to 10th	Night	22% 11% 29% 32% 7%	774
	11th to 20th	Night	24% 9% 27% 32% 8%	950
	21st to end	Night	25% 12% 31% 28% 5%	1045

Page generated at 2024-11-07 05:55:47. Version ac07

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