Stickney Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stickney Observatory clear sky chart from 2005-11-06 to 2024-11-02.

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	18% 11% 4 8% 5% 4 4 4 5% 6% 30%	101336
	Night	19% 13% 4 9% 5% 4 4 3 5% 6% 30%	97646
Transparency	Day	52% 7% 12% 19% 9% 1	101093
	Night	55% 6% 11% 17% 9% 1	97509
Seeing	Day	26% 18% 28% 18% 8% 2	14836
	Night	25% 18% 26% 23% 8% 1	23830

By Month

Percentage Cloud Cover NE (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	16% 18% 11% 11% 6% 3 4 2 4 4 21%	2517
	11th to 20th	Day	13% 17% 8% 14% 10% 5% 3 3 4 4 19%	2520
	21st to end	Day	19% 20% 9% 10% 6% 4 3 3 4 4 19%	2804
February	1st to 10th	Day	16% 18% 5% 12% 7% 4 4 4 5% 5% 22%	1710
	11th to 20th	Day	14% 16% 8% 13% 6% 6% 4 3 4 4 24%	1848
	21st to end	Day	18% 15% 4 13% 6% 3 4 3 3 5% 26%	1570
March	1st to 10th	Day	22% 17% 5% 9% 5% 4 3 3 4 5% 24%	3116
	11th to 20th	Day	14% 20% 7% 10% 4 4 3 3 4 5% 26%	3272
	21st to end	Day	20% 11% 4 11% 4 4 4 3 4 5% 31%	4166
April	1st to 10th	Day	21% 15% 3 7% 5% 4 3 3 5% 5% 31%	2280
	11th to 20th	Day	16% 13% 3 7% 5% 5% 4 4 5% 5% 34%	2254
	21st to end	Day	21% 12% 3 6% 5% 4 4 4 5% 5% 30%	2399
May	1st to 10th	Day	28% 11% 3 7% 4 4 4 3 5% 6% 27%	4133
	11th to 20th	Day	19% 9% 3 7% 5% 4 5% 4 6% 7% 30%	4398
	21st to end	Day	14% 7% 2 6% 5% 4 5% 5% 6% 8% 39%	4837
June	1st to 10th	Day	19% 8% 3 7% 6% 5% 5% 5% 6% 9% 28%	2660
	11th to 20th	Day	20% 6% 2 6% 5% 4 5% 4 6% 10% 31%	2660
	21st to end	Day	20% 8% 2 6% 6% 5% 6% 4 7% 7% 28%	2660
July	1st to 10th	Day	14% 7% 3 7% 4 5% 6% 5% 7% 10% 33%	4440
	11th to 20th	Day	13% 7% 2 7% 6% 5% 5% 5% 8% 9% 33%	4440
	21st to end	Day	17% 8% 3 7% 5% 5% 5% 4 7% 8% 32%	4814
August	1st to 10th	Day	18% 8% 3 7% 4 5% 5% 5% 5% 8% 31%	4371
	11th to 20th	Day	15% 8% 3 8% 5% 5% 6% 4 7% 9% 30%	3794
	21st to end	Day	15% 5% 2 6% 4 4 5% 4 6% 9% 39%	4180
September	1st to 10th	Day	15% 7% 2 5% 4 4 4 4 5% 7% 42%	2280
	11th to 20th	Day	18% 5% 2 5% 3 4 3 3 5% 6% 46%	2171
	21st to end	Day	17% 7% 2 5% 4 4 4 4 6% 8% 39%	2090
October	1st to 10th	Day	24% 9% 3 7% 4 4 4 3 4 5% 33%	2019
	11th to 20th	Day	17% 11% 3 7% 4 3 3 4 5% 6% 36%	1877
	21st to end	Day	24% 13% 3 7% 4 4 4 4 4 6% 27%	1881
November	1st to 10th	Day	15% 12% 3 7% 3 3 4 3 4 7% 39%	1680
	11th to 20th	Day	17% 15% 3 9% 5% 3 4 3 4 5% 32%	1710
	21st to end	Day	19% 14% 4 9% 5% 4 4 4 4 5% 28%	1587
December	1st to 10th	Day	18% 21% 6% 11% 4 4 3 2 4 5% 20%	1520
	11th to 20th	Day	20% 19% 5% 9% 4 3 3 2 3 4 28%	1906
	21st to end	Day	20% 20% 4 11% 6% 5% 3 2 4 5% 20%	2772
January	1st to 10th	Night	14% 17% 8% 13% 5% 4 3 3 3 4 26%	4429
	11th to 20th	Night	13% 19% 8% 16% 10% 5% 4 3 3 5% 16%	4440
	21st to end	Night	22% 17% 6% 13% 6% 6% 4 2 3 3 17%	4850
February	1st to 10th	Night	16% 16% 5% 14% 7% 5% 4 4 5% 4 21%	2469
	11th to 20th	Night	13% 14% 6% 12% 8% 5% 5% 3 5% 5% 24%	2218
	21st to end	Night	16% 14% 5% 12% 5% 3 4 3 5% 5% 27%	1884
March	1st to 10th	Night	22% 12% 4 9% 6% 4 4 3 5% 5% 25%	3724
	11th to 20th	Night	13% 19% 6% 10% 5% 4 4 3 4 5% 28%	3685
	21st to end	Night	21% 16% 4 11% 4 3 3 3 3 4 30%	3466
April	1st to 10th	Night	20% 14% 4 7% 3 4 5% 3 5% 6% 29%	1900
	11th to 20th	Night	20% 13% 3 6% 4 4 4 4 5% 6% 32%	1875
	21st to end	Night	21% 13% 4 7% 4 3 4 3 4 5% 33%	1781
May	1st to 10th	Night	28% 11% 2 7% 4 4 4 4 4 6% 27%	2834
	11th to 20th	Night	17% 10% 3 9% 6% 5% 5% 4 5% 6% 29%	2496
	21st to end	Night	17% 6% 3 7% 5% 5% 4 3 7% 7% 36%	2738
June	1st to 10th	Night	20% 8% 3 6% 4 4 4 3 5% 8% 33%	1520
	11th to 20th	Night	21% 6% 1 5% 4 4 4 3 6% 8% 38%	1520
	21st to end	Night	15% 7% 3 5% 5% 4 5% 4 7% 7% 38%	1520
July	1st to 10th	Night	14% 9% 3 7% 5% 5% 6% 4 6% 7% 35%	2520
	11th to 20th	Night	20% 9% 3 7% 5% 4 4 3 5% 7% 34%	2520
	21st to end	Night	17% 8% 3 7% 5% 4 5% 4 5% 8% 35%	2739
August	1st to 10th	Night	27% 8% 2 5% 3 3 3 3 5% 7% 32%	2527
	11th to 20th	Night	17% 9% 3 7% 4 5% 4 4 6% 7% 34%	3029
	21st to end	Night	13% 7% 2 5% 3 4 4 4 5% 9% 44%	3476
September	1st to 10th	Night	17% 7% 2 6% 3 4 4 3 5% 5% 43%	1900
	11th to 20th	Night	17% 5% 2 5% 4 3 3 2 4 7% 49%	2009
	21st to end	Night	17% 7% 2 6% 5% 4 4 3 4 6% 42%	2090
October	1st to 10th	Night	23% 9% 3 6% 4 4 3 4 5% 5% 34%	2158
	11th to 20th	Night	17% 11% 3 6% 4 4 4 4 5% 6% 37%	2301
	21st to end	Night	24% 11% 3 7% 4 5% 3 3 5% 6% 27%	2717
November	1st to 10th	Night	16% 12% 3 7% 4 4 4 3 5% 5% 38%	2421
	11th to 20th	Night	18% 13% 3 7% 5% 4 5% 4 5% 5% 31%	2470
	21st to end	Night	15% 16% 4 8% 5% 4 5% 3 5% 5% 29%	2588
December	1st to 10th	Night	20% 20% 5% 10% 5% 4 4 3 4 4 21%	2660
	11th to 20th	Night	22% 16% 7% 10% 4 3 4 3 4 4 23%	3288
	21st to end	Night	23% 18% 7% 10% 4 4 4 3 4 4 20%	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	63% 8% 8% 16% 4	2518
	11th to 20th	Day	67% 8% 7% 13% 4 1	2520
	21st to end	Day	69% 5% 9% 12% 4 1	2804
February	1st to 10th	Day	65% 5% 9% 14% 6% 1	1710
	11th to 20th	Day	63% 5% 8% 15% 8% 1	1857
	21st to end	Day	61% 6% 9% 14% 9% 1	1570
March	1st to 10th	Day	63% 5% 12% 11% 9% 1	3119
	11th to 20th	Day	56% 8% 14% 11% 8% 2	3272
	21st to end	Day	54% 6% 7% 14% 17% 3	4166
April	1st to 10th	Day	56% 5% 8% 20% 9% 2	2280
	11th to 20th	Day	51% 7% 10% 18% 13% 1	2254
	21st to end	Day	54% 7% 8% 16% 11% 3	2399
May	1st to 10th	Day	57% 6% 11% 16% 9% 1	4147
	11th to 20th	Day	50% 8% 15% 18% 8% 1	4402
	21st to end	Day	39% 9% 14% 25% 12% 1	4837
June	1st to 10th	Day	50% 8% 15% 17% 9%	2660
	11th to 20th	Day	48% 7% 13% 20% 11% 1	2660
	21st to end	Day	52% 8% 12% 19% 8%	2660
July	1st to 10th	Day	44% 8% 12% 23% 12% 1	4370
	11th to 20th	Day	43% 9% 15% 23% 9%	4365
	21st to end	Day	47% 8% 15% 21% 10%	4661
August	1st to 10th	Day	49% 8% 14% 20% 8%	4357
	11th to 20th	Day	47% 8% 16% 23% 5% 1	3832
	21st to end	Day	40% 8% 14% 29% 9% 1	4180
September	1st to 10th	Day	40% 8% 12% 27% 13% 1	2280
	11th to 20th	Day	38% 6% 11% 25% 19% 1	2171
	21st to end	Day	42% 6% 13% 24% 13% 2	2090
October	1st to 10th	Day	54% 6% 9% 18% 11% 2	2019
	11th to 20th	Day	47% 7% 14% 22% 9% 1	1877
	21st to end	Day	59% 6% 11% 15% 9% 2	1881
November	1st to 10th	Day	45% 6% 14% 21% 13% 1	1680
	11th to 20th	Day	53% 6% 11% 16% 12% 1	1710
	21st to end	Day	56% 5% 16% 15% 7% 1	1587
December	1st to 10th	Day	67% 6% 9% 11% 6% 1	1520
	11th to 20th	Day	62% 4 11% 16% 6% 1	1906
	21st to end	Day	66% 7% 10% 11% 7%	2772
January	1st to 10th	Night	61% 6% 12% 13% 7% 1	4429
	11th to 20th	Night	67% 8% 9% 10% 5% 1	4440
	21st to end	Night	71% 5% 8% 10% 5% 1	4850
February	1st to 10th	Night	65% 6% 9% 13% 5% 1	2469
	11th to 20th	Night	60% 7% 10% 13% 9% 1	2220
	21st to end	Night	58% 6% 11% 16% 8% 2	1884
March	1st to 10th	Night	59% 6% 10% 16% 7% 1	3734
	11th to 20th	Night	56% 8% 12% 16% 7% 1	3686
	21st to end	Night	58% 5% 6% 12% 16% 3	3466
April	1st to 10th	Night	55% 6% 11% 17% 9% 1	1900
	11th to 20th	Night	52% 6% 10% 19% 12% 1	1875
	21st to end	Night	53% 6% 9% 16% 13% 3	1781
May	1st to 10th	Night	57% 7% 11% 15% 9% 1	2840
	11th to 20th	Night	53% 9% 15% 15% 7% 1	2497
	21st to end	Night	44% 9% 12% 20% 13% 2	2739
June	1st to 10th	Night	48% 6% 15% 21% 10%	1520
	11th to 20th	Night	43% 7% 17% 23% 11%	1520
	21st to end	Night	43% 8% 15% 23% 11% 1	1520
July	1st to 10th	Night	47% 7% 13% 18% 14%	2480
	11th to 20th	Night	49% 6% 12% 23% 10%	2472
	21st to end	Night	46% 7% 12% 24% 10% 1	2651
August	1st to 10th	Night	51% 7% 13% 20% 8%	2517
	11th to 20th	Night	47% 7% 16% 21% 8%	3057
	21st to end	Night	37% 6% 17% 29% 11%	3476
September	1st to 10th	Night	42% 7% 11% 26% 14% 1	1900
	11th to 20th	Night	36% 5% 12% 28% 18% 1	2009
	21st to end	Night	44% 6% 10% 25% 14% 2	2090
October	1st to 10th	Night	51% 6% 11% 21% 10% 2	2158
	11th to 20th	Night	47% 6% 16% 20% 10% 1	2301
	21st to end	Night	58% 6% 11% 16% 8% 1	2717
November	1st to 10th	Night	49% 5% 11% 19% 14% 2	2421
	11th to 20th	Night	52% 7% 11% 16% 11% 2	2470
	21st to end	Night	55% 7% 14% 17% 7%	2588
December	1st to 10th	Night	66% 7% 11% 11% 5%	2660
	11th to 20th	Night	63% 7% 11% 10% 8%	3288
	21st to end	Night	68% 5% 9% 13% 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	30% 29% 24% 14% 3	180
	11th to 20th	Day	32% 28% 28% 9% 1 1	180
	21st to end	Day	26% 29% 31% 9% 5%	207
February	1st to 10th	Day	36% 34% 23% 5% 1	270
	11th to 20th	Day	30% 33% 26% 10% 2	456
	21st to end	Day	34% 25% 26% 12% 2	382
March	1st to 10th	Day	32% 25% 26% 16% 2	460
	11th to 20th	Day	32% 26% 27% 11% 3	460
	21st to end	Day	33% 27% 22% 11% 5% 1	506
April	1st to 10th	Day	38% 20% 24% 12% 6% 1	460
	11th to 20th	Day	33% 24% 24% 12% 6% 2	452
	21st to end	Day	32% 18% 30% 13% 5% 2	460
May	1st to 10th	Day	34% 20% 26% 13% 6% 2	463
	11th to 20th	Day	25% 16% 33% 18% 5% 1	487
	21st to end	Day	22% 15% 29% 22% 9% 3	529
June	1st to 10th	Day	19% 15% 34% 21% 10% 1	490
	11th to 20th	Day	22% 12% 32% 24% 9% 1	490
	21st to end	Day	23% 18% 29% 20% 8% 2	490
July	1st to 10th	Day	17% 10% 32% 25% 14% 2	485
	11th to 20th	Day	15% 7% 36% 29% 11% 2	484
	21st to end	Day	15% 13% 37% 23% 11% 1	532
August	1st to 10th	Day	15% 12% 28% 29% 13% 5%	486
	11th to 20th	Day	17% 10% 31% 23% 13% 6%	479
	21st to end	Day	17% 11% 28% 26% 13% 5%	539
September	1st to 10th	Day	18% 12% 23% 26% 14% 6%	490
	11th to 20th	Day	17% 13% 23% 21% 17% 9%	490
	21st to end	Day	19% 13% 29% 20% 12% 7%	490
October	1st to 10th	Day	30% 12% 23% 18% 13% 3	490
	11th to 20th	Day	25% 19% 25% 20% 9% 1	477
	21st to end	Day	33% 15% 29% 19% 4	429
November	1st to 10th	Day	27% 21% 22% 20% 10% 1	368
	11th to 20th	Day	29% 28% 22% 15% 5% 1	370
	21st to end	Day	31% 25% 26% 15% 3	247
December	1st to 10th	Day	36% 25% 26% 9% 3	180
	11th to 20th	Day	41% 25% 24% 9% 2	180
	21st to end	Day	39% 23% 25% 11% 3	198
January	1st to 10th	Night	26% 28% 31% 13% 2	760
	11th to 20th	Night	29% 25% 26% 18% 2	760
	21st to end	Night	22% 26% 31% 18% 3	836
February	1st to 10th	Night	26% 28% 31% 15% 1	760
	11th to 20th	Night	25% 28% 30% 14% 2	743
	21st to end	Night	28% 25% 27% 17% 2	628
March	1st to 10th	Night	28% 22% 29% 18% 2	760
	11th to 20th	Night	28% 26% 26% 17% 3	760
	21st to end	Night	29% 23% 23% 18% 7%	836
April	1st to 10th	Night	29% 21% 27% 20% 4	760
	11th to 20th	Night	27% 20% 26% 19% 7%	751
	21st to end	Night	30% 16% 27% 21% 6% 1	641
May	1st to 10th	Night	28% 16% 25% 24% 7% 1	570
	11th to 20th	Night	23% 12% 29% 32% 4	375
	21st to end	Night	18% 10% 26% 34% 11% 1	411
June	1st to 10th	Night	22% 9% 25% 31% 12% 1	380
	11th to 20th	Night	21% 7% 23% 39% 10%	380
	21st to end	Night	17% 7% 27% 37% 11% 1	380
July	1st to 10th	Night	15% 5% 21% 44% 15% 1	370
	11th to 20th	Night	17% 5% 21% 39% 17% 1	368
	21st to end	Night	16% 5% 23% 41% 14% 1	416
August	1st to 10th	Night	16% 5% 19% 41% 18% 1	386
	11th to 20th	Night	19% 4 20% 34% 19% 4	706
	21st to end	Night	17% 6% 21% 33% 20% 1	836
September	1st to 10th	Night	20% 7% 25% 31% 16% 2	760
	11th to 20th	Night	19% 7% 19% 30% 20% 5%	760
	21st to end	Night	20% 12% 23% 29% 14% 3	760
October	1st to 10th	Night	28% 11% 20% 26% 13% 2	760
	11th to 20th	Night	24% 13% 27% 26% 10%	760
	21st to end	Night	32% 17% 26% 21% 4	836
November	1st to 10th	Night	25% 19% 25% 24% 6%	745
	11th to 20th	Night	25% 22% 28% 16% 7% 1	760
	21st to end	Night	27% 21% 29% 17% 6% 1	760
December	1st to 10th	Night	33% 26% 24% 13% 4	760
	11th to 20th	Night	30% 24% 26% 16% 3	760
	21st to end	Night	32% 26% 26% 14% 2	836

Page generated at 2024-10-30 01:22:55. Version ac07

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