Hawkeye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawkeye Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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% 9% 3 7% 5% 4 4 4 5% 7% 38%	101429
	Night	14% 9% 4 7% 4 4 4 3 5% 6% 39%	97679
Transparency	Day	44% 6% 12% 24% 13% 1	104968
	Night	44% 5% 11% 23% 15% 2	102280
Seeing	Day	17% 10% 29% 25% 14% 5%	15869
	Night	17% 9% 31% 30% 12% 1	25706

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	12% 14% 9% 14% 5% 4 4 4 3 4 26%	2527
	11th to 20th	Day	12% 12% 5% 16% 5% 4 5% 9% 8% 6% 19%	2530
	21st to end	Day	17% 19% 10% 11% 4 3 3 3 4 5% 20%	2947
February	1st to 10th	Day	12% 14% 7% 9% 5% 5% 5% 4 5% 6% 30%	1710
	11th to 20th	Day	13% 10% 3 8% 5% 6% 4 3 4 6% 36%	1800
	21st to end	Day	14% 14% 4 10% 5% 4 4 3 4 5% 33%	1570
March	1st to 10th	Day	13% 9% 3 7% 4 4 4 3 5% 7% 41%	3120
	11th to 20th	Day	11% 7% 3 8% 5% 4 4 3 5% 7% 43%	3352
	21st to end	Day	21% 13% 4 10% 5% 5% 5% 3 4 5% 24%	4123
April	1st to 10th	Day	18% 12% 3 8% 5% 4 4 4 4 6% 31%	2280
	11th to 20th	Day	17% 10% 3 7% 5% 4 4 4 5% 7% 34%	2254
	21st to end	Day	20% 10% 2 7% 5% 4 4 4 4 6% 34%	2332
May	1st to 10th	Day	16% 8% 3 8% 5% 4 5% 4 5% 7% 35%	4173
	11th to 20th	Day	16% 6% 2 6% 4 4 4 4 4 7% 44%	4399
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 5% 6% 9% 39%	4824
June	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 4 6% 8% 43%	2660
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 9% 45%	2660
	21st to end	Day	12% 6% 2 6% 6% 4 4 5% 7% 10% 38%	2660
July	1st to 10th	Day	11% 8% 3 7% 5% 5% 6% 4 7% 9% 34%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 9% 51%	4440
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 4 6% 9% 41%	4813
August	1st to 10th	Day	10% 5% 2 6% 4 5% 6% 4 7% 9% 42%	4329
	11th to 20th	Day	11% 5% 2 5% 4 3 4 4 6% 8% 47%	3775
	21st to end	Day	9% 6% 2 6% 4 4 4 3 6% 8% 47%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 3 5% 8% 47%	2280
	11th to 20th	Day	12% 3 1 4 3 4 3 3 5% 8% 52%	2214
	21st to end	Day	12% 6% 4 6% 4 4 4 4 5% 7% 45%	2090
October	1st to 10th	Day	14% 6% 2 4 4 3 3 3 4 7% 49%	1949
	11th to 20th	Day	19% 8% 3 6% 4 5% 3 4 5% 6% 37%	1900
	21st to end	Day	19% 10% 3 5% 5% 3 4 3 3 7% 39%	1920
November	1st to 10th	Day	12% 9% 3 6% 4 3 4 3 4 6% 46%	1708
	11th to 20th	Day	13% 13% 3 9% 5% 4 5% 4 5% 6% 33%	1710
	21st to end	Day	16% 14% 2 8% 4 3 3 3 4 6% 37%	1539
December	1st to 10th	Day	14% 14% 4 9% 5% 5% 4 3 4 6% 31%	1520
	11th to 20th	Day	14% 14% 5% 9% 5% 5% 5% 4 5% 6% 29%	1918
	21st to end	Day	21% 20% 10% 12% 6% 4 3 3 3 4 14%	2783
January	1st to 10th	Night	13% 15% 8% 11% 5% 4 3 3 3 4 31%	4428
	11th to 20th	Night	13% 17% 7% 13% 6% 4 4 6% 6% 4 20%	4440
	21st to end	Night	17% 19% 8% 10% 6% 5% 4 2 4 5% 22%	4718
February	1st to 10th	Night	13% 14% 5% 7% 6% 5% 4 3 4 5% 33%	2470
	11th to 20th	Night	12% 11% 4 7% 5% 4 4 3 5% 6% 39%	2266
	21st to end	Night	18% 11% 4 7% 4 4 3 3 5% 5% 37%	1884
March	1st to 10th	Night	19% 9% 3 5% 4 3 4 3 4 5% 41%	3733
	11th to 20th	Night	9% 6% 2 7% 5% 5% 4 3 5% 8% 47%	3623
	21st to end	Night	24% 11% 4 10% 5% 4 3 3 3 5% 28%	3508
April	1st to 10th	Night	17% 11% 3 5% 5% 4 4 3 5% 5% 39%	1900
	11th to 20th	Night	19% 9% 3 8% 4 3 4 2 5% 5% 39%	1875
	21st to end	Night	17% 8% 2 7% 4 3 4 4 7% 6% 36%	1848
May	1st to 10th	Night	17% 6% 3 7% 4 4 5% 4 6% 7% 36%	2722
	11th to 20th	Night	14% 6% 2 6% 4 4 5% 5% 6% 7% 41%	2506
	21st to end	Night	10% 7% 2 6% 4 4 4 5% 6% 7% 45%	2743
June	1st to 10th	Night	8% 4 1 5% 4 5% 5% 4 7% 9% 47%	1520
	11th to 20th	Night	11% 5% 2 5% 4 3 4 4 6% 9% 46%	1520
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 5% 7% 46%	1520
July	1st to 10th	Night	14% 6% 3 6% 4 4 4 4 6% 8% 40%	2530
	11th to 20th	Night	5% 4 2 4 3 3 4 3 6% 9% 56%	2530
	21st to end	Night	7% 5% 2 6% 4 4 6% 5% 7% 8% 46%	2750
August	1st to 10th	Night	8% 3 2 6% 4 4 4 3 5% 9% 52%	2607
	11th to 20th	Night	9% 5% 2 5% 4 4 3 4 5% 7% 51%	3042
	21st to end	Night	9% 4 2 5% 4 5% 4 3 5% 8% 51%	3476
September	1st to 10th	Night	9% 6% 1 5% 4 3 3 3 4 6% 57%	1900
	11th to 20th	Night	11% 4 1 5% 4 3 5% 3 5% 7% 53%	1947
	21st to end	Night	11% 5% 2 6% 4 4 4 3 5% 7% 50%	2090
October	1st to 10th	Night	12% 6% 2 6% 3 3 4 3 4 5% 51%	2228
	11th to 20th	Night	17% 7% 2 6% 4 3 4 2 4 6% 45%	2280
	21st to end	Night	19% 8% 3 6% 4 4 4 3 5% 7% 37%	2676
November	1st to 10th	Night	12% 8% 3 6% 3 3 3 3 4 5% 50%	2470
	11th to 20th	Night	14% 11% 3 8% 5% 4 4 4 5% 6% 36%	2470
	21st to end	Night	18% 10% 3 7% 5% 3 4 3 4 6% 38%	2636
December	1st to 10th	Night	15% 13% 4 9% 5% 5% 4 4 4 6% 31%	2660
	11th to 20th	Night	15% 13% 5% 9% 5% 4 4 3 5% 6% 31%	3279
	21st to end	Night	22% 16% 6% 11% 5% 5% 4 3 4 5% 19%	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	62% 5% 12% 15% 6%	2528
	11th to 20th	Day	60% 6% 14% 12% 8% 1	2530
	21st to end	Day	68% 4 9% 14% 5%	2947
February	1st to 10th	Day	55% 4 13% 16% 11% 1	1710
	11th to 20th	Day	49% 5% 11% 24% 9% 2	1810
	21st to end	Day	53% 6% 8% 20% 10% 2	1570
March	1st to 10th	Day	43% 6% 11% 26% 10% 3	3120
	11th to 20th	Day	39% 5% 11% 33% 11% 1	3352
	21st to end	Day	62% 6% 12% 15% 4 1	4123
April	1st to 10th	Day	54% 5% 10% 20% 10%	2280
	11th to 20th	Day	50% 6% 9% 21% 12% 2	2254
	21st to end	Day	51% 5% 12% 17% 13% 2	2332
May	1st to 10th	Day	47% 6% 11% 20% 15% 1	4211
	11th to 20th	Day	40% 7% 11% 30% 13%	4403
	21st to end	Day	39% 8% 12% 22% 15% 4	4837
June	1st to 10th	Day	38% 8% 13% 24% 16% 1	2660
	11th to 20th	Day	35% 7% 13% 24% 19% 2	2660
	21st to end	Day	40% 9% 13% 23% 12% 2	2660
July	1st to 10th	Day	44% 7% 13% 24% 9% 2	4371
	11th to 20th	Day	28% 7% 17% 30% 18% 1	4365
	21st to end	Day	38% 8% 15% 17% 19% 3	4662
August	1st to 10th	Day	37% 8% 15% 27% 13% 1	4314
	11th to 20th	Day	33% 6% 13% 33% 14% 1	3811
	21st to end	Day	34% 6% 12% 30% 16% 1	4179
September	1st to 10th	Day	37% 6% 10% 26% 20% 2	2280
	11th to 20th	Day	30% 6% 12% 32% 18% 2	2214
	21st to end	Day	39% 6% 9% 27% 18% 1	2090
October	1st to 10th	Day	24% 4 7% 38% 26% 1	3235
	11th to 20th	Day	34% 3 10% 27% 24% 2	3140
	21st to end	Day	42% 3 9% 29% 14% 3	3145
November	1st to 10th	Day	41% 5% 14% 24% 14% 2	1708
	11th to 20th	Day	51% 5% 13% 20% 10% 1	1710
	21st to end	Day	50% 5% 14% 23% 8%	1539
December	1st to 10th	Day	54% 5% 15% 17% 8% 1	1520
	11th to 20th	Day	55% 5% 15% 15% 8% 2	1915
	21st to end	Day	75% 4 8% 8% 5%	2783
January	1st to 10th	Night	57% 5% 10% 19% 9% 1	4428
	11th to 20th	Night	64% 4 10% 13% 9%	4440
	21st to end	Night	66% 4 8% 15% 6% 1	4718
February	1st to 10th	Night	54% 4 10% 19% 12% 1	2470
	11th to 20th	Night	47% 5% 12% 22% 14% 1	2267
	21st to end	Night	50% 4 11% 20% 11% 3	1884
March	1st to 10th	Night	45% 6% 12% 22% 11% 5%	3733
	11th to 20th	Night	36% 5% 11% 30% 16% 2	3623
	21st to end	Night	60% 5% 8% 18% 8% 1	3508
April	1st to 10th	Night	47% 6% 10% 22% 13% 2	1900
	11th to 20th	Night	48% 4 7% 20% 18% 4	1875
	21st to end	Night	44% 7% 13% 22% 12% 2	1848
May	1st to 10th	Night	45% 8% 12% 17% 17% 2	2749
	11th to 20th	Night	40% 9% 12% 25% 14% 1	2507
	21st to end	Night	34% 9% 13% 20% 20% 3	2751
June	1st to 10th	Night	31% 8% 14% 26% 20% 1	1520
	11th to 20th	Night	33% 7% 10% 25% 23% 3	1520
	21st to end	Night	36% 7% 13% 22% 18% 3	1520
July	1st to 10th	Night	42% 6% 15% 22% 12% 3	2490
	11th to 20th	Night	24% 5% 16% 34% 19% 2	2482
	21st to end	Night	32% 8% 16% 20% 20% 4	2662
August	1st to 10th	Night	30% 5% 14% 30% 19% 2	2598
	11th to 20th	Night	31% 6% 13% 31% 18% 1	3071
	21st to end	Night	31% 6% 13% 30% 17% 4	3476
September	1st to 10th	Night	30% 5% 11% 26% 24% 2	1900
	11th to 20th	Night	31% 6% 9% 32% 19% 3	1947
	21st to end	Night	34% 6% 10% 29% 19% 2	2090
October	1st to 10th	Night	25% 4 6% 35% 29% 1	3722
	11th to 20th	Night	33% 4 8% 26% 26% 3	3779
	21st to end	Night	43% 4 9% 26% 15% 3	4401
November	1st to 10th	Night	37% 5% 9% 27% 18% 3	2470
	11th to 20th	Night	48% 6% 12% 21% 12% 1	2470
	21st to end	Night	48% 5% 12% 23% 11% 1	2636
December	1st to 10th	Night	55% 5% 11% 20% 8% 1	2660
	11th to 20th	Night	54% 4 13% 19% 8% 1	3281
	21st to end	Night	68% 5% 8% 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	19% 15% 29% 30% 7%	270
	11th to 20th	Day	21% 15% 37% 21% 4 1	270
	21st to end	Day	24% 11% 39% 21% 4 1	297
February	1st to 10th	Day	18% 20% 37% 19% 6%	270
	11th to 20th	Day	22% 21% 33% 21% 3	270
	21st to end	Day	25% 18% 42% 12% 4	225
March	1st to 10th	Day	19% 21% 42% 14% 4	270
	11th to 20th	Day	24% 17% 38% 14% 6% 1	270
	21st to end	Day	29% 14% 31% 17% 6% 2	477
April	1st to 10th	Day	26% 16% 32% 22% 5%	460
	11th to 20th	Day	24% 20% 26% 19% 8% 3	452
	21st to end	Day	25% 12% 30% 23% 8% 2	460
May	1st to 10th	Day	21% 13% 31% 24% 8% 3	515
	11th to 20th	Day	22% 9% 31% 23% 12% 3	675
	21st to end	Day	18% 10% 26% 23% 16% 7%	734
June	1st to 10th	Day	10% 7% 31% 30% 18% 5%	680
	11th to 20th	Day	12% 7% 32% 29% 15% 5%	680
	21st to end	Day	15% 7% 28% 30% 16% 5%	680
July	1st to 10th	Day	10% 2 17% 32% 26% 13%	671
	11th to 20th	Day	9% 6% 27% 30% 19% 9%	668
	21st to end	Day	8% 4 24% 36% 21% 7%	739
August	1st to 10th	Day	7% 3 22% 34% 24% 9%	676
	11th to 20th	Day	11% 6% 21% 26% 21% 15%	513
	21st to end	Day	11% 5% 18% 30% 26% 10%	539
September	1st to 10th	Day	15% 6% 24% 26% 23% 6%	490
	11th to 20th	Day	10% 3 22% 29% 24% 11%	490
	21st to end	Day	14% 12% 26% 24% 17% 7%	490
October	1st to 10th	Day	15% 10% 28% 27% 17% 3	349
	11th to 20th	Day	26% 19% 31% 16% 7%	300
	21st to end	Day	28% 15% 31% 19% 6%	330
November	1st to 10th	Day	17% 17% 35% 20% 9% 2	282
	11th to 20th	Day	19% 20% 36% 18% 7% 1	270
	21st to end	Day	28% 10% 37% 20% 4	270
December	1st to 10th	Day	17% 19% 40% 17% 4 3	270
	11th to 20th	Day	20% 12% 40% 20% 8% 1	270
	21st to end	Day	27% 16% 39% 15% 2	297
January	1st to 10th	Night	18% 13% 36% 26% 6% 1	950
	11th to 20th	Night	20% 13% 37% 24% 5% 1	950
	21st to end	Night	21% 11% 36% 26% 5%	1045
February	1st to 10th	Night	21% 13% 37% 24% 5%	950
	11th to 20th	Night	18% 14% 38% 24% 5%	791
	21st to end	Night	25% 13% 37% 20% 4	628
March	1st to 10th	Night	21% 12% 37% 24% 6%	760
	11th to 20th	Night	16% 13% 36% 28% 7%	661
	21st to end	Night	24% 9% 34% 25% 6% 1	627
April	1st to 10th	Night	22% 12% 37% 25% 4	570
	11th to 20th	Night	21% 15% 29% 28% 7%	563
	21st to end	Night	21% 8% 34% 28% 8% 1	570
May	1st to 10th	Night	18% 8% 34% 31% 8% 1	570
	11th to 20th	Night	20% 6% 31% 32% 11%	561
	21st to end	Night	13% 5% 31% 35% 16% 1	617
June	1st to 10th	Night	9% 6% 26% 43% 15% 1	570
	11th to 20th	Night	11% 5% 31% 40% 13%	570
	21st to end	Night	10% 5% 27% 40% 17% 1	570
July	1st to 10th	Night	8% 2 15% 42% 30% 3	555
	11th to 20th	Night	8% 2 21% 42% 24% 3	552
	21st to end	Night	9% 2 16% 47% 24% 1	624
August	1st to 10th	Night	5% 2 16% 45% 28% 3	567
	11th to 20th	Night	9% 2 15% 38% 30% 6%	564
	21st to end	Night	9% 2 17% 42% 27% 2	627
September	1st to 10th	Night	10% 3 23% 34% 26% 4	570
	11th to 20th	Night	11% 3 22% 36% 25% 3	617
	21st to end	Night	12% 8% 26% 31% 21% 2	760
October	1st to 10th	Night	14% 6% 30% 32% 17% 1	760
	11th to 20th	Night	20% 11% 32% 27% 10%	760
	21st to end	Night	22% 11% 33% 25% 8% 1	836
November	1st to 10th	Night	16% 10% 40% 23% 10% 1	760
	11th to 20th	Night	19% 13% 36% 25% 6%	760
	21st to end	Night	23% 11% 35% 23% 7%	926
December	1st to 10th	Night	22% 11% 38% 23% 6% 1	950
	11th to 20th	Night	24% 11% 34% 26% 5% 1	950
	21st to end	Night	28% 13% 35% 23% 2	1045

Page generated at 2024-11-03 01:11:23. Version ac07

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