Houghton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Houghton clear sky chart from 2005-11-06 to 2024-12-02.

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	13% 11% 4 10% 6% 5% 4 3 5% 6% 33%	101913
	Night	12% 13% 5% 12% 7% 6% 5% 3 5% 5% 28%	97867
Transparency	Day	52% 3 13% 22% 9% 1	105348
	Night	58% 3 11% 19% 8% 1	102506
Seeing	Day	19% 12% 31% 25% 11% 3	16201
	Night	19% 11% 28% 29% 12% 1	26121

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	8% 20% 14% 26% 8% 6% 5% 2 3 3 6%	2527
	11th to 20th	Day	9% 15% 6% 21% 25% 10% 4 1 3 1 5%	2530
	21st to end	Day	9% 18% 14% 16% 10% 8% 6% 4 3 3 9%	2783
February	1st to 10th	Day	8% 13% 6% 16% 13% 11% 7% 4 5% 4 13%	1610
	11th to 20th	Day	8% 13% 6% 16% 9% 11% 7% 4 4 4 19%	1738
	21st to end	Day	8% 16% 6% 14% 11% 8% 6% 4 6% 7% 16%	1570
March	1st to 10th	Day	8% 10% 4 14% 7% 5% 5% 3 6% 5% 33%	3118
	11th to 20th	Day	7% 12% 6% 15% 10% 6% 4 3 4 6% 28%	3274
	21st to end	Day	18% 13% 5% 18% 6% 4 4 3 4 4 20%	4165
April	1st to 10th	Day	14% 13% 4 8% 5% 4 6% 5% 5% 6% 29%	2280
	11th to 20th	Day	19% 11% 5% 9% 6% 5% 4 3 5% 6% 29%	2259
	21st to end	Day	18% 10% 4 7% 5% 4 4 3 6% 6% 34%	2470
May	1st to 10th	Day	16% 9% 3 7% 4 4 4 3 5% 6% 41%	4418
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 4 6% 7% 40%	4399
	21st to end	Day	13% 8% 3 8% 5% 4 4 4 5% 7% 39%	4837
June	1st to 10th	Day	11% 7% 2 6% 4 4 5% 4 7% 7% 44%	2660
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 4 6% 7% 42%	2660
	21st to end	Day	14% 6% 2 6% 4 4 4 4 6% 7% 43%	2660
July	1st to 10th	Day	12% 5% 2 5% 3 3 4 4 6% 8% 48%	4440
	11th to 20th	Day	7% 4 2 5% 4 3 4 3 6% 8% 53%	4440
	21st to end	Day	8% 5% 1 5% 3 3 3 3 5% 8% 56%	4814
August	1st to 10th	Day	9% 5% 2 8% 5% 4 4 4 6% 8% 44%	4423
	11th to 20th	Day	13% 6% 2 4 3 3 3 3 5% 7% 51%	4177
	21st to end	Day	13% 5% 2 5% 3 4 4 3 4 7% 48%	4180
September	1st to 10th	Day	14% 6% 2 6% 4 5% 4 3 6% 8% 44%	2280
	11th to 20th	Day	13% 8% 3 7% 4 4 4 3 6% 9% 39%	2199
	21st to end	Day	19% 9% 3 7% 5% 4 3 3 6% 7% 36%	2090
October	1st to 10th	Day	16% 12% 3 9% 5% 4 4 3 5% 7% 31%	1956
	11th to 20th	Day	21% 19% 4 8% 4 5% 5% 4 4 6% 20%	1827
	21st to end	Day	20% 22% 6% 10% 6% 4 4 3 4 4 17%	1881
November	1st to 10th	Day	17% 20% 5% 12% 4 5% 4 3 3 4 21%	1762
	11th to 20th	Day	15% 21% 8% 17% 8% 5% 4 3 3 4 13%	1661
	21st to end	Day	12% 21% 10% 21% 10% 4 4 4 3 3 9%	1600
December	1st to 10th	Day	9% 20% 13% 23% 10% 4 3 3 4 4 7%	1528
	11th to 20th	Day	15% 16% 9% 22% 10% 8% 4 3 3 3 7%	1914
	21st to end	Day	21% 21% 8% 18% 8% 5% 4 2 2 4 8%	2783
January	1st to 10th	Night	8% 21% 10% 27% 8% 7% 4 2 3 2 10%	4428
	11th to 20th	Night	8% 15% 9% 23% 19% 9% 5% 2 3 3 5%	4440
	21st to end	Night	8% 19% 11% 16% 10% 8% 6% 3 4 4 11%	4884
February	1st to 10th	Night	9% 14% 5% 14% 12% 12% 6% 4 4 4 16%	2565
	11th to 20th	Night	9% 13% 4 14% 12% 11% 7% 4 4 5% 17%	2328
	21st to end	Night	11% 16% 5% 12% 8% 7% 5% 4 5% 5% 22%	1884
March	1st to 10th	Night	7% 9% 4 11% 6% 5% 6% 5% 7% 8% 32%	3722
	11th to 20th	Night	7% 12% 7% 14% 6% 5% 5% 3 5% 6% 31%	3701
	21st to end	Night	17% 12% 6% 15% 7% 5% 4 4 5% 6% 20%	3466
April	1st to 10th	Night	16% 12% 4 8% 5% 7% 6% 4 5% 6% 26%	1900
	11th to 20th	Night	19% 11% 4 8% 5% 4 4 3 5% 5% 32%	1870
	21st to end	Night	18% 11% 4 7% 5% 4 4 3 4 6% 34%	1710
May	1st to 10th	Night	16% 7% 3 6% 4 5% 4 4 5% 6% 40%	2529
	11th to 20th	Night	12% 7% 3 8% 5% 5% 4 3 5% 6% 41%	2506
	21st to end	Night	14% 8% 3 8% 6% 6% 5% 4 6% 6% 34%	2750
June	1st to 10th	Night	13% 6% 2 6% 5% 5% 6% 4 6% 7% 40%	1520
	11th to 20th	Night	11% 7% 4 7% 6% 5% 6% 5% 6% 7% 37%	1520
	21st to end	Night	14% 6% 3 6% 4 5% 5% 4 6% 8% 39%	1520
July	1st to 10th	Night	10% 5% 2 6% 5% 5% 5% 3 5% 6% 47%	2530
	11th to 20th	Night	6% 4 2 4 4 4 4 5% 6% 9% 53%	2530
	21st to end	Night	7% 5% 2 4 4 4 3 4 6% 8% 53%	2750
August	1st to 10th	Night	12% 5% 2 6% 5% 5% 4 4 7% 7% 43%	2517
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 4 7% 52%	2653
	21st to end	Night	15% 6% 2 5% 4 4 3 3 4 6% 48%	3476
September	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 5% 6% 47%	1900
	11th to 20th	Night	12% 7% 3 6% 5% 5% 4 4 5% 7% 42%	1962
	21st to end	Night	17% 8% 3 8% 4 4 4 3 5% 6% 38%	2090
October	1st to 10th	Night	18% 9% 2 7% 5% 4 5% 3 5% 6% 36%	2222
	11th to 20th	Night	17% 16% 4 9% 6% 5% 5% 3 5% 5% 25%	2352
	21st to end	Night	20% 19% 4 10% 5% 5% 4 3 4 4 22%	2717
November	1st to 10th	Night	15% 21% 5% 10% 5% 4 4 3 5% 6% 22%	2536
	11th to 20th	Night	16% 18% 8% 15% 7% 5% 5% 2 4 4 16%	2735
	21st to end	Night	14% 18% 9% 19% 7% 5% 4 3 4 4 13%	2800
December	1st to 10th	Night	10% 19% 10% 22% 10% 6% 4 3 3 3 9%	2687
	11th to 20th	Night	10% 18% 7% 20% 10% 8% 5% 3 4 4 12%	3283
	21st to end	Night	19% 22% 8% 17% 8% 5% 4 2 3 3 10%	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	86% 2 5% 7% 1	2528
	11th to 20th	Day	90% 2 4 4	2530
	21st to end	Day	83% 2 8% 5% 1	2783
February	1st to 10th	Day	73% 4 10% 11% 2	1610
	11th to 20th	Day	70% 3 9% 15% 4	1747
	21st to end	Day	67% 5% 8% 13% 7% 1	1570
March	1st to 10th	Day	53% 3 13% 21% 10%	3120
	11th to 20th	Day	59% 2 16% 15% 7% 1	3274
	21st to end	Day	68% 3 8% 15% 5% 1	4165
April	1st to 10th	Day	53% 5% 10% 22% 10%	2280
	11th to 20th	Day	56% 4 8% 22% 9% 2	2259
	21st to end	Day	50% 4 9% 22% 13% 2	2470
May	1st to 10th	Day	45% 3 10% 25% 16% 1	4430
	11th to 20th	Day	45% 2 11% 30% 11% 1	4403
	21st to end	Day	46% 3 14% 20% 16% 1	4837
June	1st to 10th	Day	38% 3 16% 28% 14% 1	2660
	11th to 20th	Day	40% 4 15% 26% 14% 1	2660
	21st to end	Day	39% 4 16% 29% 12% 1	2660
July	1st to 10th	Day	35% 3 18% 29% 14% 1	4371
	11th to 20th	Day	28% 4 17% 36% 14% 1	4365
	21st to end	Day	28% 3 14% 39% 15% 1	4662
August	1st to 10th	Day	38% 4 18% 29% 10% 1	4408
	11th to 20th	Day	34% 4 22% 31% 9%	4219
	21st to end	Day	36% 5% 18% 28% 12% 1	4179
September	1st to 10th	Day	39% 4 15% 33% 10%	2280
	11th to 20th	Day	42% 4 23% 25% 6%	2199
	21st to end	Day	49% 3 16% 25% 7%	2090
October	1st to 10th	Day	41% 4 13% 34% 8%	3242
	11th to 20th	Day	60% 3 11% 16% 11%	3017
	21st to end	Day	64% 5% 12% 15% 4	3081
November	1st to 10th	Day	68% 3 10% 14% 5%	1762
	11th to 20th	Day	77% 3 9% 8% 3	1661
	21st to end	Day	82% 3 8% 5% 2	1600
December	1st to 10th	Day	82% 3 9% 6% 1	1528
	11th to 20th	Day	85% 2 7% 5% 2	1915
	21st to end	Day	83% 2 5% 9% 1	2783
January	1st to 10th	Night	84% 2 6% 8%	4428
	11th to 20th	Night	88% 2 7% 4	4440
	21st to end	Night	79% 3 13% 5% 1	4884
February	1st to 10th	Night	72% 4 10% 11% 3	2565
	11th to 20th	Night	69% 4 9% 14% 3	2329
	21st to end	Night	64% 3 10% 16% 6% 1	1884
March	1st to 10th	Night	49% 4 17% 20% 10%	3733
	11th to 20th	Night	55% 2 11% 22% 8% 1	3702
	21st to end	Night	66% 3 7% 16% 7% 1	3466
April	1st to 10th	Night	57% 4 8% 19% 10% 1	1900
	11th to 20th	Night	54% 4 9% 21% 11% 2	1870
	21st to end	Night	52% 3 7% 22% 15% 1	1710
May	1st to 10th	Night	45% 3 11% 27% 13% 1	2536
	11th to 20th	Night	45% 3 9% 26% 15% 2	2507
	21st to end	Night	50% 3 12% 18% 15% 1	2751
June	1st to 10th	Night	43% 4 11% 27% 14% 2	1520
	11th to 20th	Night	45% 5% 13% 22% 14% 1	1520
	21st to end	Night	42% 4 15% 24% 13% 1	1520
July	1st to 10th	Night	38% 5% 15% 27% 12% 3	2490
	11th to 20th	Night	26% 5% 16% 37% 15% 1	2482
	21st to end	Night	28% 4 13% 33% 21% 2	2662
August	1st to 10th	Night	39% 3 14% 30% 11% 2	2508
	11th to 20th	Night	33% 4 18% 32% 12% 1	2677
	21st to end	Night	38% 5% 14% 28% 13% 1	3476
September	1st to 10th	Night	37% 4 14% 33% 12% 1	1900
	11th to 20th	Night	42% 4 18% 30% 6%	1962
	21st to end	Night	47% 3 17% 26% 6% 1	2090
October	1st to 10th	Night	36% 4 11% 34% 14%	3703
	11th to 20th	Night	52% 3 11% 23% 11%	3901
	21st to end	Night	61% 3 15% 16% 4	4467
November	1st to 10th	Night	64% 4 10% 16% 6%	2536
	11th to 20th	Night	73% 3 10% 9% 5%	2735
	21st to end	Night	76% 4 10% 8% 2	2800
December	1st to 10th	Night	81% 3 7% 7% 1	2687
	11th to 20th	Night	77% 4 9% 8% 2	3281
	21st to end	Night	82% 2 7% 8% 1	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	17% 15% 36% 23% 6% 2	270
	11th to 20th	Day	19% 12% 38% 24% 6% 1	270
	21st to end	Day	21% 14% 41% 21% 2	297
February	1st to 10th	Day	20% 21% 37% 16% 4 1	270
	11th to 20th	Day	16% 30% 31% 16% 7%	270
	21st to end	Day	19% 25% 42% 12% 2	225
March	1st to 10th	Day	13% 20% 42% 19% 4 1	270
	11th to 20th	Day	15% 21% 36% 21% 6% 1	275
	21st to end	Day	24% 14% 31% 21% 8% 2	506
April	1st to 10th	Day	23% 10% 36% 25% 6% 1	460
	11th to 20th	Day	29% 13% 27% 21% 7% 2	452
	21st to end	Day	27% 10% 29% 22% 9% 3	460
May	1st to 10th	Day	19% 13% 36% 22% 8% 2	643
	11th to 20th	Day	16% 11% 37% 24% 8% 3	675
	21st to end	Day	18% 8% 30% 29% 13% 2	734
June	1st to 10th	Day	14% 9% 34% 29% 13% 2	680
	11th to 20th	Day	18% 7% 34% 28% 11% 3	680
	21st to end	Day	17% 9% 29% 28% 14% 4	680
July	1st to 10th	Day	9% 5% 31% 34% 16% 4	671
	11th to 20th	Day	11% 8% 30% 28% 17% 6%	668
	21st to end	Day	9% 6% 29% 33% 17% 5%	739
August	1st to 10th	Day	13% 8% 27% 32% 16% 4	676
	11th to 20th	Day	16% 5% 20% 31% 21% 7%	595
	21st to end	Day	19% 9% 22% 29% 17% 4	539
September	1st to 10th	Day	18% 6% 28% 27% 17% 4	490
	11th to 20th	Day	16% 8% 26% 29% 18% 2	490
	21st to end	Day	22% 10% 25% 24% 14% 3	490
October	1st to 10th	Day	23% 16% 26% 22% 11% 3	356
	11th to 20th	Day	32% 17% 31% 18% 2	300
	21st to end	Day	36% 17% 32% 13% 2 1	330
November	1st to 10th	Day	26% 21% 28% 20% 5% 1	300
	11th to 20th	Day	30% 18% 37% 11% 5%	300
	21st to end	Day	25% 20% 34% 15% 5% 1	300
December	1st to 10th	Day	23% 13% 36% 21% 7% 1	273
	11th to 20th	Day	26% 20% 34% 14% 4 1	270
	21st to end	Day	26% 16% 38% 16% 3	297
January	1st to 10th	Night	17% 17% 38% 22% 5% 1	950
	11th to 20th	Night	18% 14% 39% 21% 7% 2	950
	21st to end	Night	18% 14% 34% 25% 8% 1	1045
February	1st to 10th	Night	17% 17% 33% 25% 7% 1	950
	11th to 20th	Night	16% 17% 32% 24% 10% 1	854
	21st to end	Night	20% 10% 36% 27% 6%	628
March	1st to 10th	Night	14% 12% 30% 32% 10% 2	760
	11th to 20th	Night	17% 14% 31% 29% 8% 1	719
	21st to end	Night	22% 9% 23% 30% 14% 2	627
April	1st to 10th	Night	23% 6% 29% 33% 7% 2	570
	11th to 20th	Night	26% 8% 25% 30% 10% 1	563
	21st to end	Night	24% 6% 24% 32% 13% 2	570
May	1st to 10th	Night	20% 7% 27% 31% 13% 1	570
	11th to 20th	Night	19% 4 28% 33% 12% 3	561
	21st to end	Night	16% 5% 22% 37% 19% 1	617
June	1st to 10th	Night	17% 5% 19% 43% 14% 2	570
	11th to 20th	Night	15% 5% 21% 44% 14% 1	570
	21st to end	Night	17% 4 21% 38% 18% 2	570
July	1st to 10th	Night	10% 4 19% 43% 22% 3	555
	11th to 20th	Night	12% 6% 25% 31% 23% 2	552
	21st to end	Night	9% 3 21% 41% 23% 3	624
August	1st to 10th	Night	11% 2 21% 40% 24% 1	567
	11th to 20th	Night	12% 3 18% 30% 32% 4	564
	21st to end	Night	16% 5% 22% 31% 23% 2	627
September	1st to 10th	Night	16% 6% 20% 32% 22% 4	570
	11th to 20th	Night	17% 4 24% 33% 19% 3	632
	21st to end	Night	21% 7% 23% 31% 16% 1	760
October	1st to 10th	Night	24% 10% 26% 26% 14% 1	760
	11th to 20th	Night	27% 12% 27% 24% 9%	760
	21st to end	Night	31% 11% 23% 26% 7% 1	836
November	1st to 10th	Night	26% 14% 27% 27% 6% 1	780
	11th to 20th	Night	25% 17% 28% 21% 8% 1	935
	21st to end	Night	23% 18% 31% 24% 4	1000
December	1st to 10th	Night	21% 19% 34% 19% 7% 1	960
	11th to 20th	Night	19% 18% 33% 21% 9% 1	950
	21st to end	Night	27% 14% 33% 19% 6%	1045

Page generated at 2024-11-29 10:43:10. Version ac07

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