SPARQ Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SPARQ Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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	9% 5% 2 4 3 2 3 3 4 6% 57%	74684
	Night	11% 6% 2 4 4 2 3 4 4 6% 53%	75069
Transparency	Day	29% 4 9% 20% 24% 15%	74404
	Night	32% 4 9% 19% 22% 15%	74871
Seeing	Day	11% 11% 23% 30% 19% 6%	14228
	Night	12% 5% 15% 31% 30% 6%	23595

By Month

Percentage Cloud Cover SW (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	22% 7% 3 5% 5% 2 4 3 5% 5% 39%	1623
	11th to 20th	Day	16% 6% 3 5% 5% 2 4 3 4 5% 47%	1639
	21st to end	Day	14% 7% 3 6% 4 4 5% 3 5% 7% 42%	1782
February	1st to 10th	Day	17% 5% 2 6% 5% 3 4 3 4 4 47%	1620
	11th to 20th	Day	13% 6% 2 6% 4 2 4 4 5% 7% 45%	1606
	21st to end	Day	17% 7% 2 3 5% 2 3 3 4 6% 48%	1480
March	1st to 10th	Day	18% 9% 3 6% 5% 3 4 4 5% 6% 37%	1974
	11th to 20th	Day	18% 7% 3 5% 4 3 5% 5% 5% 7% 38%	1980
	21st to end	Day	15% 5% 3 5% 4 3 5% 4 5% 7% 44%	2183
April	1st to 10th	Day	15% 7% 3 5% 5% 3 4 4 6% 7% 41%	2160
	11th to 20th	Day	9% 5% 3 4 4 3 4 4 5% 6% 53%	2129
	21st to end	Day	7% 4 2 3 3 2 3 3 5% 9% 57%	2160
May	1st to 10th	Day	7% 5% 2 4 3 2 3 3 4 7% 61%	2306
	11th to 20th	Day	7% 4 2 3 3 2 3 3 5% 7% 61%	2337
	21st to end	Day	6% 6% 2 5% 4 2 3 3 5% 7% 59%	2723
June	1st to 10th	Day	7% 5% 2 4 3 2 3 3 4 9% 59%	2520
	11th to 20th	Day	2 2 1 2 2 1 2 4 3 6% 74%	2520
	21st to end	Day	3 3 2 3 2 2 2 2 3 4 75%	2520
July	1st to 10th	Day	2 4 2 3 2 1 3 3 2 5% 75%	2520
	11th to 20th	Day	1 4 2 3 3 1 2 2 4 7% 72%	2349
	21st to end	Day	1 3 2 3 3 1 2 3 3 5% 73%	2546
August	1st to 10th	Day	2 4 2 3 3 2 3 3 4 6% 68%	2328
	11th to 20th	Day	1 3 2 3 3 1 2 3 4 6% 72%	2240
	21st to end	Day	2 5% 2 4 3 2 2 3 4 6% 67%	2376
September	1st to 10th	Day	1 3 1 3 2 1 2 2 4 5% 76%	2160
	11th to 20th	Day	4 4 2 4 3 2 3 3 4 7% 64%	2148
	21st to end	Day	4 2 1 3 2 1 2 3 3 6% 73%	1900
October	1st to 10th	Day	7% 3 1 2 3 2 3 3 4 6% 67%	1800
	11th to 20th	Day	9% 3 2 3 4 1 3 4 4 5% 63%	1800
	21st to end	Day	11% 3 1 3 3 1 3 3 4 6% 60%	1980
November	1st to 10th	Day	11% 4 2 4 4 3 4 4 5% 6% 55%	1842
	11th to 20th	Day	12% 5% 3 5% 5% 3 4 3 4 8% 49%	1671
	21st to end	Day	11% 4 2 4 3 2 5% 4 5% 6% 54%	1520
December	1st to 10th	Day	18% 6% 3 5% 4 2 3 4 4 6% 44%	1520
	11th to 20th	Day	32% 8% 3 5% 4 2 3 3 5% 5% 30%	1928
	21st to end	Day	22% 9% 3 5% 5% 3 3 3 4 7% 35%	2794
January	1st to 10th	Night	18% 8% 3 5% 4 3 5% 4 5% 9% 36%	2537
	11th to 20th	Night	18% 5% 2 5% 5% 2 3 4 5% 5% 44%	2377
	21st to end	Night	16% 6% 2 4 4 2 4 4 4 6% 47%	2574
February	1st to 10th	Night	17% 5% 2 4 4 2 3 4 4 6% 49%	2340
	11th to 20th	Night	13% 6% 3 5% 4 3 4 4 5% 8% 45%	2240
	21st to end	Night	15% 5% 2 3 2 2 4 3 4 6% 53%	1776
March	1st to 10th	Night	18% 9% 4 6% 4 3 5% 4 4 5% 39%	1983
	11th to 20th	Night	16% 7% 3 5% 4 2 3 4 6% 8% 42%	1980
	21st to end	Night	16% 7% 2 4 3 2 3 3 4 5% 51%	2171
April	1st to 10th	Night	11% 6% 3 5% 5% 2 4 4 4 6% 50%	1800
	11th to 20th	Night	9% 7% 2 4 4 3 3 3 3 7% 55%	1779
	21st to end	Night	7% 5% 2 3 3 2 4 4 4 6% 62%	1800
May	1st to 10th	Night	6% 5% 2 5% 4 2 3 2 5% 6% 59%	1651
	11th to 20th	Night	5% 4 2 4 4 3 4 4 4 8% 59%	1554
	21st to end	Night	5% 5% 3 5% 3 2 2 4 5% 7% 60%	1552
June	1st to 10th	Night	6% 6% 2 3 3 2 3 4 4 8% 58%	1440
	11th to 20th	Night	2 3 1 3 3 2 2 3 3 6% 72%	1440
	21st to end	Night	4 4 3 3 3 1 2 2 3 4 70%	1440
July	1st to 10th	Night	2 3 2 3 2 2 2 3 3 6% 72%	1440
	11th to 20th	Night	2 4 1 4 3 1 3 4 4 6% 68%	1607
	21st to end	Night	1 5% 3 6% 5% 2 4 4 5% 7% 56%	1773
August	1st to 10th	Night	2 7% 2 5% 4 2 3 3 3 7% 61%	1611
	11th to 20th	Night	1 4 3 5% 4 2 5% 4 5% 7% 60%	1660
	21st to end	Night	1 6% 3 5% 5% 2 3 3 4 6% 62%	1980
September	1st to 10th	Night	1 3 1 3 3 2 3 3 4 7% 71%	1800
	11th to 20th	Night	5% 6% 2 5% 4 2 3 3 4 7% 59%	1808
	21st to end	Night	3 5% 1 4 2 1 3 3 4 5% 69%	2060
October	1st to 10th	Night	5% 5% 1 4 4 1 3 3 4 6% 64%	2160
	11th to 20th	Night	7% 3 2 6% 5% 2 3 4 5% 5% 58%	2160
	21st to end	Night	9% 3 2 3 3 2 4 4 4 7% 59%	2376
November	1st to 10th	Night	10% 5% 2 4 4 2 3 3 5% 8% 53%	2234
	11th to 20th	Night	12% 6% 2 5% 3 2 3 4 5% 7% 50%	2508
	21st to end	Night	10% 4 1 4 4 2 4 3 5% 6% 56%	2660
December	1st to 10th	Night	20% 6% 3 5% 4 2 3 3 4 6% 44%	2660
	11th to 20th	Night	32% 6% 2 4 4 2 4 3 5% 6% 32%	3276
	21st to end	Night	22% 8% 2 5% 5% 3 4 4 4 5% 37%	4862

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	49% 4 12% 21% 9% 6%	1623
	11th to 20th	Day	41% 4 10% 16% 16% 13%	1639
	21st to end	Day	43% 4 10% 16% 20% 8%	1782
February	1st to 10th	Day	42% 4 6% 19% 20% 9%	1620
	11th to 20th	Day	39% 5% 8% 21% 19% 7%	1615
	21st to end	Day	39% 4 9% 25% 15% 7%	1480
March	1st to 10th	Day	48% 6% 10% 17% 16% 3	1974
	11th to 20th	Day	45% 5% 9% 22% 14% 5%	1980
	21st to end	Day	40% 6% 13% 20% 17% 3	2183
April	1st to 10th	Day	43% 5% 13% 20% 15% 4	2160
	11th to 20th	Day	32% 5% 14% 23% 20% 6%	2132
	21st to end	Day	25% 5% 14% 30% 22% 4	2160
May	1st to 10th	Day	25% 4 9% 29% 26% 7%	2306
	11th to 20th	Day	23% 4 9% 34% 22% 7%	2340
	21st to end	Day	26% 6% 16% 29% 20% 3	2724
June	1st to 10th	Day	25% 5% 11% 28% 25% 6%	2520
	11th to 20th	Day	13% 3 11% 21% 37% 15%	2520
	21st to end	Day	14% 2 4 17% 36% 26%	2520
July	1st to 10th	Day	14% 2 4 13% 27% 40%	2451
	11th to 20th	Day	14% 3 7% 13% 29% 35%	2279
	21st to end	Day	14% 1 5% 10% 29% 41%	2405
August	1st to 10th	Day	17% 2 6% 17% 31% 26%	2312
	11th to 20th	Day	13% 1 7% 12% 37% 29%	2240
	21st to end	Day	18% 2 6% 13% 36% 25%	2376
September	1st to 10th	Day	11% 1 5% 12% 32% 39%	2160
	11th to 20th	Day	21% 3 7% 25% 33% 12%	2148
	21st to end	Day	15% 3 5% 23% 30% 24%	1900
October	1st to 10th	Day	21% 3 6% 17% 31% 23%	1800
	11th to 20th	Day	23% 4 8% 19% 25% 21%	1800
	21st to end	Day	26% 4 8% 21% 25% 16%	1980
November	1st to 10th	Day	30% 5% 8% 28% 18% 11%	1842
	11th to 20th	Day	36% 5% 11% 23% 17% 9%	1671
	21st to end	Day	32% 4 11% 20% 19% 13%	1520
December	1st to 10th	Day	41% 6% 8% 18% 19% 9%	1520
	11th to 20th	Day	58% 3 7% 12% 15% 5%	1928
	21st to end	Day	49% 5% 13% 20% 9% 4	2794
January	1st to 10th	Night	46% 5% 12% 21% 11% 6%	2537
	11th to 20th	Night	42% 4 10% 17% 14% 14%	2377
	21st to end	Night	39% 4 12% 13% 22% 11%	2574
February	1st to 10th	Night	38% 4 7% 20% 19% 12%	2340
	11th to 20th	Night	38% 4 10% 19% 21% 8%	2242
	21st to end	Night	33% 4 11% 25% 21% 6%	1776
March	1st to 10th	Night	48% 6% 10% 15% 17% 4	1983
	11th to 20th	Night	41% 3 10% 21% 19% 5%	1980
	21st to end	Night	37% 4 13% 23% 17% 5%	2171
April	1st to 10th	Night	36% 6% 14% 20% 20% 5%	1800
	11th to 20th	Night	31% 3 12% 26% 18% 10%	1779
	21st to end	Night	24% 4 11% 31% 24% 6%	1800
May	1st to 10th	Night	28% 4 6% 21% 31% 10%	1651
	11th to 20th	Night	25% 5% 9% 27% 26% 8%	1555
	21st to end	Night	25% 5% 13% 30% 23% 5%	1552
June	1st to 10th	Night	25% 4 10% 23% 30% 8%	1440
	11th to 20th	Night	15% 2 8% 22% 34% 19%	1440
	21st to end	Night	19% 2 5% 13% 32% 29%	1440
July	1st to 10th	Night	15% 2 4 11% 28% 41%	1400
	11th to 20th	Night	18% 1 7% 12% 25% 37%	1554
	21st to end	Night	27% 1 6% 8% 21% 39%	1674
August	1st to 10th	Night	25% 1 5% 15% 25% 29%	1602
	11th to 20th	Night	21% 2 6% 11% 27% 34%	1660
	21st to end	Night	23% 2 6% 13% 27% 29%	1980
September	1st to 10th	Night	13% 2 5% 9% 31% 39%	1800
	11th to 20th	Night	25% 2 7% 18% 33% 15%	1808
	21st to end	Night	18% 1 4 22% 27% 27%	2060
October	1st to 10th	Night	21% 2 8% 17% 27% 25%	2160
	11th to 20th	Night	27% 3 6% 19% 22% 22%	2160
	21st to end	Night	26% 3 8% 19% 25% 18%	2376
November	1st to 10th	Night	31% 4 11% 26% 18% 11%	2234
	11th to 20th	Night	33% 4 12% 25% 17% 9%	2508
	21st to end	Night	30% 3 10% 20% 23% 14%	2660
December	1st to 10th	Night	42% 4 9% 16% 19% 10%	2660
	11th to 20th	Night	54% 4 9% 13% 15% 4	3276
	21st to end	Night	50% 6% 11% 18% 11% 4	4862

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% 13% 25% 18% 11% 4	284
	11th to 20th	Day	22% 12% 24% 24% 16% 3	347
	21st to end	Day	16% 12% 23% 28% 18% 3	374
February	1st to 10th	Day	19% 12% 20% 24% 20% 4	340
	11th to 20th	Day	17% 18% 28% 23% 13% 1	349
	21st to end	Day	17% 16% 27% 25% 14% 1	346
March	1st to 10th	Day	26% 17% 27% 20% 7% 2	420
	11th to 20th	Day	25% 14% 28% 20% 10% 4	420
	21st to end	Day	16% 19% 32% 24% 9% 1	462
April	1st to 10th	Day	17% 20% 29% 22% 10% 2	420
	11th to 20th	Day	14% 21% 30% 21% 10% 4	412
	21st to end	Day	8% 19% 29% 26% 12% 5%	420
May	1st to 10th	Day	11% 17% 29% 26% 13% 3	423
	11th to 20th	Day	11% 15% 31% 26% 13% 4	448
	21st to end	Day	11% 13% 24% 29% 18% 5%	485
June	1st to 10th	Day	10% 12% 26% 31% 15% 7%	450
	11th to 20th	Day	5% 12% 29% 37% 13% 3	450
	21st to end	Day	3 5% 27% 36% 24% 5%	450
July	1st to 10th	Day	6% 4 21% 43% 22% 4	446
	11th to 20th	Day	2 1 18% 43% 28% 8%	444
	21st to end	Day	1 2 11% 48% 30% 8%	487
August	1st to 10th	Day	4 4 20% 42% 23% 8%	447
	11th to 20th	Day	3 3 19% 38% 27% 9%	437
	21st to end	Day	5% 2 20% 38% 28% 8%	495
September	1st to 10th	Day	2 4 19% 40% 26% 9%	450
	11th to 20th	Day	6% 7% 22% 34% 22% 8%	450
	21st to end	Day	6% 8% 21% 34% 24% 7%	450
October	1st to 10th	Day	6% 10% 24% 26% 24% 11%	450
	11th to 20th	Day	8% 8% 18% 29% 26% 11%	450
	21st to end	Day	13% 8% 17% 30% 24% 7%	495
November	1st to 10th	Day	12% 10% 17% 26% 28% 7%	438
	11th to 20th	Day	10% 9% 15% 27% 25% 14%	251
	21st to end	Day	10% 9% 24% 26% 20% 10%	180
December	1st to 10th	Day	18% 18% 14% 21% 18% 10%	180
	11th to 20th	Day	24% 12% 21% 18% 16% 8%	180
	21st to end	Day	20% 14% 23% 23% 16% 4	198
January	1st to 10th	Night	21% 6% 16% 29% 23% 4	760
	11th to 20th	Night	20% 7% 15% 33% 21% 5%	732
	21st to end	Night	19% 5% 15% 33% 24% 4	792
February	1st to 10th	Night	20% 5% 13% 36% 24% 2	720
	11th to 20th	Night	16% 8% 19% 31% 22% 4	704
	21st to end	Night	17% 10% 20% 32% 18% 2	592
March	1st to 10th	Night	22% 9% 19% 27% 19% 4	720
	11th to 20th	Night	19% 7% 17% 32% 22% 3	720
	21st to end	Night	18% 7% 26% 30% 16% 3	792
April	1st to 10th	Night	13% 9% 25% 31% 19% 3	720
	11th to 20th	Night	11% 13% 23% 28% 20% 5%	711
	21st to end	Night	9% 11% 26% 25% 23% 6%	720
May	1st to 10th	Night	9% 7% 21% 32% 27% 4	571
	11th to 20th	Night	6% 4 21% 31% 35% 3	492
	21st to end	Night	7% 9% 21% 30% 29% 4	389
June	1st to 10th	Night	8% 6% 21% 33% 29% 2	360
	11th to 20th	Night	4 5% 18% 43% 28% 2	360
	21st to end	Night	4 1 15% 38% 38% 3	360
July	1st to 10th	Night	3 1 10% 35% 45% 5%	350
	11th to 20th	Night	3 1 4 30% 48% 13%	510
	21st to end	Night	4 1 4 32% 49% 10%	591
August	1st to 10th	Night	5% 1 9% 31% 44% 11%	537
	11th to 20th	Night	2 1 7% 33% 47% 10%	592
	21st to end	Night	4 1 7% 32% 49% 8%	792
September	1st to 10th	Night	3 1 8% 30% 48% 10%	720
	11th to 20th	Night	7% 3 10% 35% 37% 9%	720
	21st to end	Night	5% 3 13% 32% 36% 11%	720
October	1st to 10th	Night	7% 4 15% 31% 34% 10%	720
	11th to 20th	Night	9% 3 13% 29% 38% 8%	720
	21st to end	Night	10% 4 11% 29% 33% 12%	792
November	1st to 10th	Night	11% 4 15% 28% 33% 9%	740
	11th to 20th	Night	14% 3 13% 35% 30% 6%	760
	21st to end	Night	11% 6% 16% 35% 27% 6%	760
December	1st to 10th	Night	22% 6% 13% 31% 22% 6%	760
	11th to 20th	Night	27% 6% 14% 29% 20% 3	760
	21st to end	Night	23% 7% 19% 32% 17% 2	836

Page generated at 2024-01-10 07:16:14. Version ac07

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