Sulem Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sulem Lake clear sky chart from 2005-11-06 to 2024-12-06.

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% 8% 3 8% 5% 4 4 4 5% 7% 39%	102219
	Night	11% 8% 3 8% 5% 4 4 3 5% 6% 42%	97590
Transparency	Day	42% 7% 13% 24% 12% 1	105855
	Night	41% 6% 13% 24% 14% 2	102094
Seeing	Day	15% 10% 31% 27% 13% 3	16062
	Night	14% 10% 35% 30% 10% 1	25980

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	10% 16% 4 19% 10% 5% 3 4 4 5% 21%	2527
	11th to 20th	Day	6% 13% 5% 11% 6% 7% 8% 6% 8% 6% 23%	2790
	21st to end	Day	6% 14% 9% 15% 7% 6% 6% 4 5% 6% 24%	3135
February	1st to 10th	Day	7% 11% 5% 11% 8% 7% 6% 5% 6% 7% 27%	1710
	11th to 20th	Day	9% 11% 5% 10% 7% 6% 7% 4 6% 7% 30%	1664
	21st to end	Day	13% 10% 4 10% 7% 3 4 4 5% 7% 33%	1470
March	1st to 10th	Day	14% 10% 4 8% 4 4 3 3 5% 7% 38%	3436
	11th to 20th	Day	10% 10% 3 8% 3 4 4 3 5% 8% 41%	3480
	21st to end	Day	25% 14% 5% 11% 5% 4 3 3 4 4 23%	3814
April	1st to 10th	Day	18% 9% 3 6% 4 5% 4 4 6% 7% 34%	2230
	11th to 20th	Day	20% 10% 4 6% 5% 4 4 3 4 6% 34%	2336
	21st to end	Day	24% 11% 3 6% 4 4 4 3 4 6% 31%	2470
May	1st to 10th	Day	17% 7% 2 6% 5% 4 4 4 7% 8% 36%	4082
	11th to 20th	Day	14% 7% 3 6% 4 4 4 3 4 7% 45%	4353
	21st to end	Day	17% 6% 2 7% 5% 5% 5% 4 6% 7% 38%	4824
June	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 6% 8% 47%	2660
	11th to 20th	Day	14% 5% 3 6% 5% 4 5% 4 6% 8% 41%	2732
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 6% 8% 45%	2850
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 6% 5% 6% 10% 41%	4662
	11th to 20th	Day	5% 3 1 4 3 4 4 3 5% 8% 58%	4440
	21st to end	Day	5% 4 2 5% 4 4 5% 4 7% 9% 51%	4472
August	1st to 10th	Day	12% 7% 2 6% 4 4 4 4 6% 7% 43%	4104
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	4041
	21st to end	Day	8% 5% 2 6% 3 4 4 4 6% 7% 52%	4416
September	1st to 10th	Day	12% 4 2 5% 3 3 3 3 4 7% 52%	2280
	11th to 20th	Day	11% 5% 2 5% 3 3 4 3 5% 7% 52%	2142
	21st to end	Day	13% 6% 2 5% 4 4 4 3 5% 7% 48%	2066
October	1st to 10th	Day	15% 6% 2 5% 4 3 4 3 4 6% 47%	1900
	11th to 20th	Day	14% 7% 2 4 4 4 4 3 4 5% 47%	1900
	21st to end	Day	17% 7% 4 7% 4 3 3 3 5% 6% 43%	2090
November	1st to 10th	Day	12% 8% 4 6% 3 3 5% 4 5% 7% 43%	1682
	11th to 20th	Day	11% 11% 4 11% 5% 5% 4 3 5% 5% 37%	1600
	21st to end	Day	11% 9% 4 9% 5% 3 4 3 6% 6% 39%	1600
December	1st to 10th	Day	11% 11% 4 11% 8% 5% 4 4 5% 7% 30%	1560
	11th to 20th	Day	10% 14% 5% 10% 5% 4 5% 4 5% 7% 31%	1918
	21st to end	Day	18% 12% 4 19% 5% 3 4 3 4 6% 21%	2783
January	1st to 10th	Night	9% 12% 5% 19% 9% 5% 3 3 4 5% 23%	4428
	11th to 20th	Night	5% 11% 5% 13% 8% 7% 9% 6% 8% 6% 22%	4175
	21st to end	Night	8% 15% 8% 15% 6% 4 4 3 4 5% 26%	4532
February	1st to 10th	Night	9% 11% 4 9% 6% 6% 5% 5% 5% 6% 34%	2470
	11th to 20th	Night	9% 10% 3 7% 5% 5% 5% 4 6% 7% 38%	2403
	21st to end	Night	10% 9% 3 8% 6% 5% 4 5% 7% 7% 37%	2000
March	1st to 10th	Night	9% 8% 3 8% 4 3 3 3 4 5% 49%	3419
	11th to 20th	Night	10% 6% 3 6% 5% 4 5% 5% 6% 6% 44%	3480
	21st to end	Night	28% 11% 4 10% 4 3 2 2 4 4 27%	3817
April	1st to 10th	Night	14% 8% 3 7% 5% 4 4 3 5% 6% 39%	1949
	11th to 20th	Night	17% 9% 3 8% 5% 4 3 3 3 6% 40%	1793
	21st to end	Night	19% 9% 2 6% 3 3 3 3 5% 6% 40%	1710
May	1st to 10th	Night	16% 7% 2 5% 4 4 4 3 4 5% 44%	2823
	11th to 20th	Night	12% 5% 2 5% 3 4 3 3 5% 7% 50%	2552
	21st to end	Night	17% 7% 2 5% 4 3 3 4 4 7% 44%	2743
June	1st to 10th	Night	9% 4 1 4 3 3 4 4 7% 7% 53%	1520
	11th to 20th	Night	10% 4 2 5% 4 4 5% 4 7% 7% 48%	1439
	21st to end	Night	7% 4 1 4 3 3 3 3 5% 8% 58%	1330
July	1st to 10th	Night	9% 4 1 5% 4 4 5% 4 7% 8% 49%	2303
	11th to 20th	Night	3 3 1 4 3 3 3 4 5% 8% 64%	2530
	21st to end	Night	4 3 1 4 4 3 4 4 6% 8% 59%	3088
August	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 5% 7% 50%	2836
	11th to 20th	Night	11% 4 2 4 4 3 3 3 6% 7% 53%	2798
	21st to end	Night	8% 5% 2 6% 4 3 4 3 5% 7% 53%	3245
September	1st to 10th	Night	9% 4 2 4 3 3 2 2 5% 6% 61%	1900
	11th to 20th	Night	9% 5% 1 4 3 3 4 3 5% 7% 56%	2033
	21st to end	Night	9% 5% 2 4 3 3 4 3 5% 5% 56%	2095
October	1st to 10th	Night	13% 5% 2 5% 3 4 3 3 4 6% 51%	2280
	11th to 20th	Night	14% 8% 2 5% 3 3 3 3 4 5% 49%	2280
	21st to end	Night	15% 8% 3 7% 4 3 3 3 5% 6% 44%	2508
November	1st to 10th	Night	12% 7% 2 6% 4 4 4 3 5% 5% 47%	2611
	11th to 20th	Night	10% 9% 4 10% 6% 4 4 3 5% 5% 40%	2800
	21st to end	Night	11% 9% 4 8% 5% 4 4 3 5% 6% 41%	2800
December	1st to 10th	Night	9% 10% 5% 11% 7% 5% 4 4 5% 5% 34%	2737
	11th to 20th	Night	10% 11% 5% 10% 5% 5% 5% 5% 6% 6% 31%	3279
	21st to end	Night	19% 12% 5% 13% 5% 5% 5% 3 5% 5% 23%	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	66% 5% 10% 14% 4	2528
	11th to 20th	Day	57% 5% 9% 23% 6%	2790
	21st to end	Day	60% 7% 14% 14% 4	3135
February	1st to 10th	Day	54% 7% 14% 16% 8% 1	1710
	11th to 20th	Day	53% 7% 12% 19% 7% 2	1673
	21st to end	Day	50% 7% 13% 17% 11% 2	1470
March	1st to 10th	Day	45% 7% 11% 26% 11%	3436
	11th to 20th	Day	40% 6% 11% 28% 11% 3	3480
	21st to end	Day	65% 7% 10% 12% 5%	3814
April	1st to 10th	Day	48% 7% 15% 21% 9% 1	2230
	11th to 20th	Day	51% 5% 12% 19% 11% 1	2336
	21st to end	Day	53% 6% 11% 21% 8% 1	2470
May	1st to 10th	Day	43% 9% 13% 22% 13%	4120
	11th to 20th	Day	38% 7% 11% 27% 15% 2	4357
	21st to end	Day	43% 8% 12% 25% 12% 1	4837
June	1st to 10th	Day	34% 9% 15% 27% 14% 1	2660
	11th to 20th	Day	40% 9% 13% 21% 16% 2	2732
	21st to end	Day	36% 7% 16% 26% 14% 2	2850
July	1st to 10th	Day	36% 9% 20% 24% 10% 1	4590
	11th to 20th	Day	24% 6% 14% 35% 18% 2	4365
	21st to end	Day	26% 9% 16% 31% 17% 1	4331
August	1st to 10th	Day	40% 7% 11% 28% 12% 2	4090
	11th to 20th	Day	39% 8% 16% 28% 8% 1	4080
	21st to end	Day	32% 7% 17% 29% 14% 2	4415
September	1st to 10th	Day	32% 6% 13% 30% 18% 1	2280
	11th to 20th	Day	31% 7% 16% 32% 13% 1	2142
	21st to end	Day	34% 6% 12% 30% 16% 1	2066
October	1st to 10th	Day	27% 4 8% 31% 30% 1	3160
	11th to 20th	Day	36% 4 12% 25% 20% 2	3140
	21st to end	Day	40% 4 13% 29% 13% 1	3428
November	1st to 10th	Day	39% 7% 14% 21% 16% 4	1682
	11th to 20th	Day	49% 7% 12% 21% 10% 1	1600
	21st to end	Day	46% 6% 17% 19% 11% 1	1600
December	1st to 10th	Day	54% 7% 16% 14% 9% 1	1560
	11th to 20th	Day	52% 6% 19% 17% 5%	1915
	21st to end	Day	63% 6% 12% 14% 5% 1	2783
January	1st to 10th	Night	63% 5% 9% 16% 6%	4428
	11th to 20th	Night	58% 6% 12% 16% 7%	4175
	21st to end	Night	58% 6% 12% 15% 8%	4532
February	1st to 10th	Night	50% 6% 13% 21% 9% 2	2470
	11th to 20th	Night	44% 7% 13% 22% 12% 2	2404
	21st to end	Night	44% 7% 14% 21% 12% 3	2000
March	1st to 10th	Night	37% 5% 10% 31% 16% 1	3419
	11th to 20th	Night	38% 6% 10% 29% 16% 1	3480
	21st to end	Night	62% 6% 12% 14% 6% 1	3817
April	1st to 10th	Night	45% 7% 12% 25% 11% 1	1949
	11th to 20th	Night	46% 5% 11% 19% 17% 2	1793
	21st to end	Night	44% 6% 10% 25% 13% 2	1710
May	1st to 10th	Night	41% 7% 11% 19% 20% 2	2850
	11th to 20th	Night	32% 8% 11% 25% 19% 5%	2553
	21st to end	Night	39% 6% 12% 25% 16% 2	2751
June	1st to 10th	Night	28% 8% 16% 27% 17% 3	1520
	11th to 20th	Night	32% 9% 16% 20% 20% 3	1439
	21st to end	Night	25% 6% 17% 32% 18% 2	1330
July	1st to 10th	Night	30% 7% 22% 26% 13% 2	2266
	11th to 20th	Night	18% 6% 14% 36% 23% 3	2482
	21st to end	Night	21% 7% 17% 32% 20% 2	2990
August	1st to 10th	Night	33% 6% 13% 28% 17% 3	2826
	11th to 20th	Night	30% 7% 17% 32% 12% 1	2825
	21st to end	Night	29% 7% 18% 26% 18% 2	3245
September	1st to 10th	Night	26% 4 14% 33% 22% 2	1900
	11th to 20th	Night	28% 6% 15% 32% 17% 2	2033
	21st to end	Night	29% 6% 11% 30% 22% 2	2095
October	1st to 10th	Night	23% 4 6% 28% 35% 4	3800
	11th to 20th	Night	27% 4 12% 30% 23% 4	3779
	21st to end	Night	40% 4 12% 29% 14% 1	4120
November	1st to 10th	Night	39% 5% 15% 21% 17% 3	2611
	11th to 20th	Night	45% 7% 12% 22% 13% 2	2800
	21st to end	Night	44% 6% 16% 23% 11% 1	2800
December	1st to 10th	Night	49% 7% 15% 20% 8%	2737
	11th to 20th	Night	50% 7% 17% 19% 6%	3281
	21st to end	Night	61% 6% 9% 18% 5%	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	13% 14% 36% 25% 10% 2	270
	11th to 20th	Day	17% 14% 37% 25% 6% 1	270
	21st to end	Day	13% 10% 39% 27% 8% 2	297
February	1st to 10th	Day	12% 20% 41% 23% 4	270
	11th to 20th	Day	12% 18% 40% 25% 4	270
	21st to end	Day	18% 17% 37% 25% 3	225
March	1st to 10th	Day	20% 14% 42% 22% 3	270
	11th to 20th	Day	22% 11% 37% 21% 7% 1	270
	21st to end	Day	30% 12% 28% 21% 8% 1	297
April	1st to 10th	Day	26% 15% 34% 21% 5%	410
	11th to 20th	Day	25% 17% 28% 22% 7% 1	534
	21st to end	Day	27% 14% 29% 19% 8% 3	650
May	1st to 10th	Day	21% 14% 33% 23% 8% 2	653
	11th to 20th	Day	21% 11% 29% 24% 12% 3	675
	21st to end	Day	17% 10% 28% 30% 12% 2	734
June	1st to 10th	Day	11% 7% 25% 33% 19% 5%	680
	11th to 20th	Day	15% 7% 34% 31% 11% 2	680
	21st to end	Day	12% 8% 31% 31% 16% 2	680
July	1st to 10th	Day	7% 6% 22% 33% 27% 6%	671
	11th to 20th	Day	6% 5% 31% 32% 20% 6%	668
	21st to end	Day	7% 3 24% 40% 22% 5%	739
August	1st to 10th	Day	9% 4 23% 36% 22% 5%	676
	11th to 20th	Day	13% 5% 22% 31% 25% 4	665
	21st to end	Day	8% 4 30% 34% 19% 5%	684
September	1st to 10th	Day	14% 7% 28% 30% 18% 3	490
	11th to 20th	Day	9% 4 36% 32% 16% 3	352
	21st to end	Day	15% 13% 27% 27% 12% 5%	300
October	1st to 10th	Day	19% 12% 30% 24% 11% 5%	300
	11th to 20th	Day	16% 18% 38% 19% 7% 1	300
	21st to end	Day	22% 17% 36% 19% 5% 1	330
November	1st to 10th	Day	20% 13% 36% 22% 7% 2	300
	11th to 20th	Day	17% 22% 37% 20% 4	300
	21st to end	Day	19% 18% 35% 21% 7%	300
December	1st to 10th	Day	14% 9% 45% 23% 8% 1	285
	11th to 20th	Day	16% 13% 42% 23% 6%	270
	21st to end	Day	25% 16% 36% 21% 2	297
January	1st to 10th	Night	11% 13% 43% 25% 7% 1	950
	11th to 20th	Night	13% 14% 39% 27% 6% 1	950
	21st to end	Night	16% 13% 37% 28% 5%	1045
February	1st to 10th	Night	14% 14% 41% 26% 6% 1	950
	11th to 20th	Night	14% 13% 41% 25% 5% 1	929
	21st to end	Night	14% 12% 40% 25% 7% 1	744
March	1st to 10th	Night	15% 11% 40% 25% 8% 1	570
	11th to 20th	Night	18% 12% 39% 26% 6%	570
	21st to end	Night	24% 10% 31% 26% 8% 1	627
April	1st to 10th	Night	19% 14% 40% 23% 4	570
	11th to 20th	Night	21% 13% 33% 24% 8% 1	563
	21st to end	Night	20% 12% 36% 25% 7% 1	570
May	1st to 10th	Night	18% 9% 35% 30% 7% 1	570
	11th to 20th	Night	18% 8% 31% 30% 11% 1	561
	21st to end	Night	17% 9% 29% 33% 12%	617
June	1st to 10th	Night	9% 6% 30% 38% 16% 1	570
	11th to 20th	Night	11% 3 34% 42% 10%	570
	21st to end	Night	11% 3 27% 45% 13% 1	570
July	1st to 10th	Night	5% 3 24% 40% 26% 2	555
	11th to 20th	Night	3 2 27% 44% 22% 1	552
	21st to end	Night	3 1 22% 50% 21% 2	624
August	1st to 10th	Night	8% 2 19% 46% 24% 1	567
	11th to 20th	Night	8% 3 21% 43% 22% 3	564
	21st to end	Night	6% 4 28% 41% 19% 2	627
September	1st to 10th	Night	11% 4 26% 41% 17% 1	570
	11th to 20th	Night	11% 5% 33% 35% 14% 2	570
	21st to end	Night	10% 10% 35% 31% 13% 1	575
October	1st to 10th	Night	16% 10% 33% 29% 12% 1	760
	11th to 20th	Night	16% 14% 36% 26% 7%	760
	21st to end	Night	19% 14% 32% 28% 7%	836
November	1st to 10th	Night	15% 13% 38% 25% 9%	951
	11th to 20th	Night	14% 15% 43% 23% 6%	1000
	21st to end	Night	16% 14% 40% 24% 6%	1000
December	1st to 10th	Night	14% 11% 42% 26% 6%	978
	11th to 20th	Night	18% 10% 38% 27% 7% 1	950
	21st to end	Night	22% 13% 37% 23% 5%	1045

Page generated at 2024-12-03 05:45:08. Version ac07

Copyright © 2024 Attilla Danko.