Monswath observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monswath observatory clear sky chart from 2005-11-06 to 2024-04-03.

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 6% 5% 3 4 5% 5% 7% 42%	78913
	Night	13% 8% 4 6% 5% 3 4 4 5% 6% 43%	81263
Transparency	Day	41% 7% 12% 23% 15% 2	78624
	Night	42% 6% 11% 23% 16% 3	81073
Seeing	Day	16% 11% 27% 26% 15% 4	14733
	Night	16% 11% 30% 29% 12% 1	24762

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% 13% 6% 9% 8% 3 4 5% 5% 6% 31%	2527
	11th to 20th	Day	12% 11% 4 7% 7% 5% 6% 4 5% 5% 34%	2795
	21st to end	Day	19% 16% 8% 7% 5% 3 3 4 3 5% 28%	3135
February	1st to 10th	Day	14% 11% 5% 8% 5% 4 5% 4 4 6% 34%	1710
	11th to 20th	Day	13% 10% 4 5% 5% 3 5% 4 5% 7% 38%	1780
	21st to end	Day	13% 12% 4 7% 6% 2 4 4 3 6% 39%	1570
March	1st to 10th	Day	14% 10% 4 5% 6% 3 4 4 4 5% 41%	1976
	11th to 20th	Day	18% 9% 3 6% 5% 3 4 4 5% 5% 37%	2090
	21st to end	Day	20% 11% 4 8% 6% 3 5% 4 5% 6% 29%	2384
April	1st to 10th	Day	12% 6% 3 6% 6% 3 5% 5% 5% 7% 42%	2184
	11th to 20th	Day	18% 9% 3 5% 5% 3 4 4 5% 5% 41%	2134
	21st to end	Day	19% 7% 3 6% 5% 3 4 5% 5% 8% 35%	2160
May	1st to 10th	Day	16% 7% 3 6% 5% 3 5% 5% 6% 8% 36%	2204
	11th to 20th	Day	16% 7% 2 5% 4 3 5% 5% 5% 8% 39%	2479
	21st to end	Day	11% 6% 3 6% 6% 4 5% 5% 7% 9% 38%	2725
June	1st to 10th	Day	7% 5% 2 5% 4 3 5% 5% 8% 9% 46%	2520
	11th to 20th	Day	8% 5% 2 4 4 3 4 5% 6% 9% 49%	2520
	21st to end	Day	5% 4 2 4 5% 4 6% 7% 7% 10% 47%	2520
July	1st to 10th	Day	9% 4 2 5% 5% 3 5% 5% 7% 11% 44%	2520
	11th to 20th	Day	5% 3 2 4 5% 3 5% 6% 7% 9% 52%	2520
	21st to end	Day	7% 5% 2 5% 5% 3 6% 5% 6% 9% 46%	2561
August	1st to 10th	Day	8% 4 2 6% 6% 4 6% 7% 6% 10% 42%	2328
	11th to 20th	Day	8% 5% 2 6% 6% 4 6% 6% 7% 10% 41%	2164
	21st to end	Day	7% 5% 2 5% 4 3 4 5% 5% 9% 51%	2376
September	1st to 10th	Day	13% 5% 2 4 4 3 4 4 6% 8% 48%	2160
	11th to 20th	Day	9% 6% 1 5% 4 3 4 4 5% 9% 51%	2160
	21st to end	Day	7% 5% 2 5% 4 2 3 5% 5% 8% 54%	1930
October	1st to 10th	Day	11% 5% 2 5% 4 3 3 4 5% 6% 54%	1800
	11th to 20th	Day	16% 6% 2 5% 4 2 2 3 4 5% 51%	1800
	21st to end	Day	17% 9% 2 5% 3 2 3 4 3 5% 46%	1980
November	1st to 10th	Day	10% 5% 3 4 3 2 3 4 4 7% 54%	1692
	11th to 20th	Day	14% 6% 4 5% 4 3 4 4 5% 6% 46%	1710
	21st to end	Day	16% 9% 3 6% 5% 2 3 3 4 5% 43%	1578
December	1st to 10th	Day	12% 12% 3 7% 5% 2 3 4 3 8% 41%	1520
	11th to 20th	Day	14% 9% 4 7% 4 3 4 3 5% 7% 40%	1918
	21st to end	Day	18% 13% 5% 10% 6% 4 5% 4 5% 5% 25%	2783
January	1st to 10th	Night	13% 10% 7% 10% 6% 3 4 4 4 4 35%	4428
	11th to 20th	Night	13% 10% 5% 10% 7% 4 7% 5% 4 5% 30%	4170
	21st to end	Night	22% 15% 6% 7% 5% 2 3 3 3 4 28%	4532
February	1st to 10th	Night	14% 11% 5% 8% 5% 3 5% 4 5% 6% 34%	2470
	11th to 20th	Night	14% 7% 4 7% 6% 3 3 4 5% 6% 41%	2285
	21st to end	Night	16% 10% 3 6% 5% 2 3 3 5% 5% 42%	1884
March	1st to 10th	Night	16% 11% 3 5% 4 3 4 3 4 4 44%	2218
	11th to 20th	Night	17% 8% 3 6% 6% 3 4 4 4 6% 38%	2090
	21st to end	Night	19% 11% 5% 7% 5% 2 5% 4 6% 6% 29%	2212
April	1st to 10th	Night	11% 6% 3 6% 5% 2 4 4 6% 7% 46%	1820
	11th to 20th	Night	13% 7% 3 6% 4 4 4 3 5% 7% 44%	1775
	21st to end	Night	19% 8% 3 5% 4 2 4 4 4 6% 41%	1800
May	1st to 10th	Night	15% 5% 3 4 5% 2 4 5% 5% 8% 44%	1752
	11th to 20th	Night	16% 6% 3 6% 5% 2 4 3 4 7% 44%	1416
	21st to end	Night	10% 6% 3 5% 6% 3 5% 5% 7% 9% 41%	1551
June	1st to 10th	Night	6% 4 2 4 5% 4 4 6% 6% 8% 51%	1440
	11th to 20th	Night	6% 4 2 4 5% 3 5% 5% 6% 8% 53%	1440
	21st to end	Night	4 3 2 4 4 3 5% 5% 6% 10% 54%	1440
July	1st to 10th	Night	10% 3 2 4 4 3 4 4 6% 10% 51%	1440
	11th to 20th	Night	6% 3 1 3 4 2 4 4 6% 11% 56%	1440
	21st to end	Night	7% 3 2 4 5% 3 5% 5% 6% 10% 50%	1753
August	1st to 10th	Night	6% 3 2 4 5% 3 5% 5% 7% 8% 52%	1611
	11th to 20th	Night	6% 4 3 5% 4 2 5% 4 5% 9% 53%	1737
	21st to end	Night	6% 3 2 4 4 3 4 5% 6% 8% 56%	1980
September	1st to 10th	Night	13% 4 2 4 3 2 3 3 5% 7% 54%	1800
	11th to 20th	Night	8% 4 2 5% 5% 3 4 3 6% 7% 54%	1800
	21st to end	Night	7% 4 1 4 4 3 5% 4 5% 6% 57%	2009
October	1st to 10th	Night	8% 4 2 4 4 2 4 3 4 7% 57%	2160
	11th to 20th	Night	13% 5% 2 5% 4 2 3 4 4 6% 51%	2160
	21st to end	Night	17% 8% 2 4 4 2 4 4 3 5% 47%	2376
November	1st to 10th	Night	10% 5% 2 4 4 2 3 5% 4 5% 56%	2383
	11th to 20th	Night	13% 6% 2 5% 5% 2 3 4 4 6% 50%	2470
	21st to end	Night	16% 9% 3 4 4 2 4 4 4 5% 44%	2598
December	1st to 10th	Night	14% 11% 4 6% 6% 3 5% 4 5% 6% 36%	2660
	11th to 20th	Night	15% 8% 4 7% 5% 3 4 4 5% 6% 39%	3279
	21st to end	Night	17% 19% 6% 9% 7% 3 4 4 4 4 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	51% 7% 11% 21% 9% 1	2528
	11th to 20th	Day	50% 6% 13% 20% 11%	2795
	21st to end	Day	58% 4 10% 15% 11% 1	3135
February	1st to 10th	Day	51% 5% 12% 21% 10% 1	1710
	11th to 20th	Day	46% 5% 11% 20% 15% 3	1789
	21st to end	Day	47% 5% 8% 21% 13% 4	1570
March	1st to 10th	Day	45% 5% 9% 23% 15% 2	1976
	11th to 20th	Day	49% 6% 11% 18% 13% 3	2090
	21st to end	Day	55% 7% 11% 17% 9% 1	2384
April	1st to 10th	Day	41% 6% 11% 25% 16% 1	2184
	11th to 20th	Day	46% 5% 10% 23% 13% 3	2134
	21st to end	Day	47% 6% 13% 20% 14% 1	2160
May	1st to 10th	Day	46% 8% 14% 22% 9% 1	2204
	11th to 20th	Day	42% 9% 12% 22% 14% 1	2483
	21st to end	Day	41% 8% 14% 20% 14% 2	2725
June	1st to 10th	Day	31% 9% 15% 28% 15% 2	2520
	11th to 20th	Day	30% 7% 15% 24% 20% 4	2520
	21st to end	Day	29% 10% 17% 25% 15% 5%	2520
July	1st to 10th	Day	32% 9% 16% 27% 12% 4	2451
	11th to 20th	Day	26% 9% 16% 27% 19% 3	2445
	21st to end	Day	32% 8% 14% 30% 14% 2	2419
August	1st to 10th	Day	34% 9% 16% 26% 14% 1	2314
	11th to 20th	Day	36% 9% 14% 26% 14% 1	2164
	21st to end	Day	30% 7% 13% 23% 21% 5%	2376
September	1st to 10th	Day	34% 6% 12% 25% 19% 5%	2160
	11th to 20th	Day	30% 5% 11% 27% 23% 4	2160
	21st to end	Day	28% 7% 10% 28% 25% 3	1930
October	1st to 10th	Day	32% 5% 10% 26% 23% 4	1800
	11th to 20th	Day	36% 5% 9% 24% 22% 5%	1800
	21st to end	Day	41% 5% 9% 24% 17% 3	1980
November	1st to 10th	Day	31% 4 13% 25% 21% 5%	1692
	11th to 20th	Day	38% 4 10% 24% 20% 4	1710
	21st to end	Day	45% 4 10% 26% 14%	1578
December	1st to 10th	Day	44% 5% 13% 25% 12% 1	1520
	11th to 20th	Day	44% 6% 12% 23% 13% 2	1915
	21st to end	Day	60% 7% 9% 15% 8% 1	2783
January	1st to 10th	Night	52% 6% 10% 23% 9% 1	4428
	11th to 20th	Night	57% 5% 9% 19% 9% 1	4170
	21st to end	Night	60% 4 9% 20% 6% 1	4532
February	1st to 10th	Night	51% 6% 10% 19% 12% 2	2470
	11th to 20th	Night	45% 5% 10% 22% 16% 3	2286
	21st to end	Night	46% 4 11% 21% 15% 3	1884
March	1st to 10th	Night	45% 4 9% 23% 16% 2	2218
	11th to 20th	Night	47% 5% 10% 21% 13% 3	2090
	21st to end	Night	54% 8% 11% 19% 8% 1	2212
April	1st to 10th	Night	37% 6% 11% 24% 18% 4	1820
	11th to 20th	Night	39% 6% 10% 22% 17% 5%	1775
	21st to end	Night	44% 5% 10% 22% 17% 1	1800
May	1st to 10th	Night	39% 8% 15% 20% 17% 1	1752
	11th to 20th	Night	40% 8% 12% 23% 15% 2	1417
	21st to end	Night	37% 9% 15% 19% 17% 3	1552
June	1st to 10th	Night	27% 8% 16% 28% 18% 3	1440
	11th to 20th	Night	29% 7% 12% 25% 24% 4	1440
	21st to end	Night	25% 8% 15% 28% 18% 6%	1440
July	1st to 10th	Night	28% 9% 14% 32% 12% 4	1400
	11th to 20th	Night	23% 6% 16% 29% 23% 3	1392
	21st to end	Night	28% 7% 13% 32% 18% 2	1656
August	1st to 10th	Night	27% 8% 16% 32% 15% 2	1601
	11th to 20th	Night	29% 7% 12% 30% 21% 1	1737
	21st to end	Night	24% 8% 16% 24% 22% 6%	1980
September	1st to 10th	Night	30% 6% 11% 25% 23% 6%	1800
	11th to 20th	Night	29% 7% 10% 24% 25% 4	1800
	21st to end	Night	27% 7% 9% 26% 28% 4	2009
October	1st to 10th	Night	28% 6% 11% 25% 25% 5%	2160
	11th to 20th	Night	34% 4 8% 28% 20% 6%	2160
	21st to end	Night	40% 5% 8% 21% 21% 4	2376
November	1st to 10th	Night	31% 6% 12% 25% 21% 6%	2383
	11th to 20th	Night	36% 4 8% 27% 21% 4	2470
	21st to end	Night	43% 5% 11% 24% 16% 2	2598
December	1st to 10th	Night	48% 6% 10% 23% 11% 1	2660
	11th to 20th	Night	46% 4 10% 23% 16% 1	3281
	21st to end	Night	64% 6% 9% 12% 7% 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	21% 24% 34% 17% 4	270
	11th to 20th	Day	31% 21% 33% 14%	270
	21st to end	Day	18% 22% 43% 15% 3	297
February	1st to 10th	Day	24% 24% 36% 14% 2	270
	11th to 20th	Day	26% 23% 31% 17% 3 1	270
	21st to end	Day	29% 20% 37% 12% 2	225
March	1st to 10th	Day	21% 23% 42% 13% 1	270
	11th to 20th	Day	30% 21% 31% 15% 2 1	270
	21st to end	Day	33% 19% 31% 14% 3	382
April	1st to 10th	Day	19% 14% 40% 20% 7%	428
	11th to 20th	Day	25% 17% 29% 21% 8% 1	412
	21st to end	Day	26% 14% 33% 21% 5% 1	420
May	1st to 10th	Day	18% 15% 34% 25% 7% 1	459
	11th to 20th	Day	19% 12% 28% 26% 12% 2	625
	21st to end	Day	13% 10% 28% 28% 14% 7%	679
June	1st to 10th	Day	9% 4 22% 34% 24% 7%	630
	11th to 20th	Day	10% 4 21% 36% 24% 4	630
	21st to end	Day	5% 7% 30% 37% 17% 4	630
July	1st to 10th	Day	11% 2 16% 28% 32% 11%	621
	11th to 20th	Day	5% 4 23% 35% 27% 6%	618
	21st to end	Day	8% 4 18% 34% 30% 6%	684
August	1st to 10th	Day	9% 2 17% 39% 26% 7%	626
	11th to 20th	Day	9% 4 18% 35% 27% 7%	478
	21st to end	Day	9% 2 17% 32% 31% 10%	495
September	1st to 10th	Day	13% 4 17% 33% 25% 8%	450
	11th to 20th	Day	8% 3 17% 33% 28% 11%	450
	21st to end	Day	6% 10% 23% 30% 24% 7%	390
October	1st to 10th	Day	11% 14% 27% 31% 14% 3	270
	11th to 20th	Day	21% 21% 30% 23% 6%	270
	21st to end	Day	29% 19% 31% 17% 3	297
November	1st to 10th	Day	13% 15% 35% 24% 10% 3	270
	11th to 20th	Day	21% 19% 33% 17% 9% 2	270
	21st to end	Day	26% 15% 31% 23% 3 1	270
December	1st to 10th	Day	16% 20% 39% 15% 6% 4	270
	11th to 20th	Day	22% 17% 36% 20% 5%	270
	21st to end	Day	25% 25% 36% 12% 2	297
January	1st to 10th	Night	18% 17% 39% 20% 5%	950
	11th to 20th	Night	22% 18% 36% 19% 4 1	950
	21st to end	Night	19% 19% 38% 22% 2	1045
February	1st to 10th	Night	21% 16% 38% 23% 2	950
	11th to 20th	Night	21% 17% 38% 21% 2	810
	21st to end	Night	24% 19% 38% 18% 2	628
March	1st to 10th	Night	23% 16% 39% 20% 3	698
	11th to 20th	Night	21% 14% 35% 25% 5%	570
	21st to end	Night	25% 15% 35% 21% 4	627
April	1st to 10th	Night	16% 17% 37% 25% 5%	546
	11th to 20th	Night	17% 14% 34% 28% 8%	533
	21st to end	Night	21% 11% 39% 24% 5%	540
May	1st to 10th	Night	15% 11% 32% 32% 9% 1	540
	11th to 20th	Night	19% 7% 27% 32% 14% 1	531
	21st to end	Night	12% 4 27% 36% 19% 2	584
June	1st to 10th	Night	7% 2 21% 41% 27% 1	540
	11th to 20th	Night	8% 2 23% 45% 20% 1	540
	21st to end	Night	4 2 26% 46% 21% 1	540
July	1st to 10th	Night	10% 2 8% 41% 34% 5%	525
	11th to 20th	Night	5% 2 15% 43% 32% 2	522
	21st to end	Night	8% 2 16% 40% 33% 2	591
August	1st to 10th	Night	7% 1 13% 44% 32% 2	537
	11th to 20th	Night	7% 1 16% 41% 31% 4	534
	21st to end	Night	6% 2 15% 38% 36% 3	594
September	1st to 10th	Night	14% 2 16% 38% 25% 5%	540
	11th to 20th	Night	10% 3 16% 35% 32% 4	540
	21st to end	Night	8% 7% 23% 34% 24% 5%	692
October	1st to 10th	Night	9% 6% 29% 32% 20% 4	720
	11th to 20th	Night	16% 13% 32% 29% 10%	720
	21st to end	Night	22% 13% 34% 24% 7%	792
November	1st to 10th	Night	11% 10% 39% 29% 10%	740
	11th to 20th	Night	17% 16% 34% 26% 7%	760
	21st to end	Night	22% 14% 35% 23% 6%	888
December	1st to 10th	Night	21% 15% 36% 22% 5% 1	950
	11th to 20th	Night	23% 13% 32% 28% 4	950
	21st to end	Night	25% 20% 34% 19% 2	1045

Page generated at 2024-03-31 05:08:52. Version ac07

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