Bartole Observing Platform
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bartole Observing Platform clear sky chart from 2005-11-06 to 2024-07-02.

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	15% 10% 3 9% 5% 5% 5% 4 6% 7% 32%	90028
	Night	15% 11% 4 9% 6% 5% 5% 4 5% 6% 30%	89146
Transparency	Day	52% 4 12% 20% 10% 1	89752
	Night	54% 4 12% 19% 9% 1	88977
Seeing	Day	17% 8% 27% 26% 16% 6%	14308
	Night	19% 8% 29% 31% 13% 1	23323

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	15% 13% 4 10% 6% 6% 6% 4 5% 5% 25%	2517
	11th to 20th	Day	9% 15% 7% 18% 9% 7% 4 4 6% 5% 15%	2717
	21st to end	Day	17% 19% 6% 13% 8% 6% 5% 3 4 5% 15%	3124
February	1st to 10th	Day	12% 15% 6% 13% 8% 8% 7% 5% 5% 5% 18%	1710
	11th to 20th	Day	12% 12% 6% 13% 8% 6% 5% 5% 4 6% 24%	1663
	21st to end	Day	15% 14% 5% 11% 7% 5% 4 4 6% 6% 22%	1452
March	1st to 10th	Day	17% 12% 4 8% 6% 4 5% 4 4 5% 31%	3432
	11th to 20th	Day	10% 14% 5% 10% 6% 6% 6% 4 6% 5% 28%	3480
	21st to end	Day	15% 8% 3 10% 5% 5% 5% 4 5% 5% 36%	3815
April	1st to 10th	Day	17% 12% 4 9% 6% 5% 5% 4 5% 5% 30%	2243
	11th to 20th	Day	19% 9% 2 6% 4 4 4 3 5% 7% 36%	2345
	21st to end	Day	19% 9% 3 7% 6% 4 3 3 4 6% 35%	2470
May	1st to 10th	Day	15% 8% 3 8% 5% 5% 4 4 6% 7% 36%	4108
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 4 6% 8% 36%	4398
	21st to end	Day	12% 5% 2 6% 4 4 4 4 5% 7% 46%	4837
June	1st to 10th	Day	16% 6% 3 7% 4 4 5% 4 6% 7% 38%	2660
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 4 7% 9% 41%	2746
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 4 6% 8% 40%	2850
July	1st to 10th	Day	9% 5% 2 5% 5% 5% 5% 5% 7% 8% 46%	2677
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 5% 6% 8% 41%	2520
	21st to end	Day	10% 5% 3 6% 6% 6% 5% 4 7% 10% 38%	2595
August	1st to 10th	Day	10% 5% 3 6% 5% 5% 6% 4 6% 9% 42%	2327
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 5% 8% 9% 41%	2303
	21st to end	Day	12% 5% 2 6% 5% 4 5% 4 7% 9% 40%	2491
September	1st to 10th	Day	14% 6% 3 6% 4 5% 5% 4 6% 7% 41%	2160
	11th to 20th	Day	13% 6% 2 6% 4 5% 4 4 6% 8% 43%	2052
	21st to end	Day	14% 6% 2 8% 5% 6% 6% 4 6% 7% 37%	1945
October	1st to 10th	Day	20% 7% 3 8% 5% 5% 5% 4 5% 6% 33%	1800
	11th to 20th	Day	20% 11% 4 10% 6% 5% 5% 4 6% 6% 25%	1800
	21st to end	Day	26% 13% 4 10% 5% 4 4 4 5% 6% 20%	1980
November	1st to 10th	Day	14% 13% 4 9% 5% 5% 5% 4 6% 7% 28%	1573
	11th to 20th	Day	13% 17% 4 9% 8% 6% 6% 5% 5% 7% 21%	1520
	21st to end	Day	18% 18% 4 11% 6% 6% 6% 3 5% 6% 17%	1520
December	1st to 10th	Day	16% 18% 7% 15% 8% 6% 5% 4 5% 5% 12%	1520
	11th to 20th	Day	17% 14% 4 11% 6% 7% 6% 5% 5% 6% 19%	1906
	21st to end	Day	26% 18% 6% 14% 6% 5% 4 3 4 4 11%	2772
January	1st to 10th	Night	15% 18% 6% 12% 7% 5% 6% 4 5% 5% 16%	4429
	11th to 20th	Night	13% 12% 6% 15% 11% 8% 7% 4 5% 5% 15%	4239
	21st to end	Night	18% 15% 7% 12% 8% 6% 5% 5% 5% 5% 15%	4532
February	1st to 10th	Night	12% 16% 5% 13% 8% 7% 5% 5% 6% 5% 19%	2470
	11th to 20th	Night	12% 14% 5% 12% 7% 6% 5% 4 6% 6% 23%	2403
	21st to end	Night	14% 11% 5% 12% 6% 5% 5% 4 5% 6% 26%	1995
March	1st to 10th	Night	16% 10% 4 9% 6% 5% 4 4 5% 6% 31%	3408
	11th to 20th	Night	12% 11% 4 9% 5% 5% 5% 4 6% 6% 33%	3479
	21st to end	Night	15% 7% 4 10% 6% 5% 5% 4 5% 7% 33%	3817
April	1st to 10th	Night	18% 12% 3 8% 5% 5% 5% 4 5% 6% 30%	1936
	11th to 20th	Night	18% 8% 3 7% 4 4 4 4 5% 7% 37%	1800
	21st to end	Night	17% 9% 4 9% 5% 4 4 4 4 6% 36%	1710
May	1st to 10th	Night	17% 6% 2 6% 5% 4 4 3 5% 7% 40%	2833
	11th to 20th	Night	15% 7% 2 6% 4 4 5% 4 6% 8% 39%	2495
	21st to end	Night	10% 5% 2 6% 3 4 5% 4 5% 8% 50%	2738
June	1st to 10th	Night	14% 6% 2 7% 3 5% 5% 4 6% 8% 40%	1520
	11th to 20th	Night	9% 4 2 6% 5% 6% 5% 5% 6% 9% 43%	1426
	21st to end	Night	10% 7% 2 7% 5% 5% 4 4 5% 8% 43%	1330
July	1st to 10th	Night	6% 5% 3 6% 3 3 3 4 5% 6% 56%	1304
	11th to 20th	Night	9% 6% 2 4 4 4 5% 4 5% 8% 48%	1440
	21st to end	Night	8% 5% 2 5% 4 5% 6% 3 6% 8% 48%	1720
August	1st to 10th	Night	9% 5% 1 5% 4 5% 3 4 7% 9% 49%	1611
	11th to 20th	Night	7% 4 1 6% 4 4 4 4 7% 9% 50%	1598
	21st to end	Night	11% 5% 2 5% 4 5% 5% 5% 6% 8% 44%	1846
September	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 7% 7% 45%	1800
	11th to 20th	Night	13% 5% 2 5% 3 3 4 4 6% 7% 49%	1906
	21st to end	Night	15% 8% 2 6% 5% 3 3 4 5% 5% 42%	2014
October	1st to 10th	Night	18% 8% 3 7% 5% 4 4 4 6% 7% 35%	2160
	11th to 20th	Night	18% 10% 4 7% 6% 5% 5% 4 4 6% 29%	2160
	21st to end	Night	23% 12% 3 7% 7% 5% 4 4 6% 6% 23%	2376
November	1st to 10th	Night	18% 10% 3 8% 5% 4 6% 4 5% 7% 32%	2499
	11th to 20th	Night	16% 15% 5% 10% 6% 5% 4 4 6% 7% 24%	2660
	21st to end	Night	18% 16% 5% 8% 6% 5% 5% 4 6% 6% 21%	2660
December	1st to 10th	Night	18% 18% 6% 14% 7% 5% 5% 3 4 5% 16%	2660
	11th to 20th	Night	16% 16% 5% 13% 7% 6% 5% 4 5% 6% 17%	3288
	21st to end	Night	27% 18% 6% 15% 6% 4 4 2 4 4 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	62% 4 16% 14% 5%	2518
	11th to 20th	Day	71% 4 11% 10% 4	2717
	21st to end	Day	73% 3 10% 10% 4 1	3124
February	1st to 10th	Day	67% 6% 8% 15% 4	1710
	11th to 20th	Day	62% 3 10% 17% 7% 1	1672
	21st to end	Day	62% 3 11% 16% 7%	1452
March	1st to 10th	Day	56% 3 13% 18% 10%	3435
	11th to 20th	Day	59% 3 11% 18% 8% 1	3480
	21st to end	Day	51% 3 9% 20% 15% 2	3815
April	1st to 10th	Day	56% 5% 8% 20% 10% 1	2243
	11th to 20th	Day	48% 4 9% 22% 15% 1	2345
	21st to end	Day	51% 4 11% 19% 13% 3	2470
May	1st to 10th	Day	47% 3 11% 24% 14% 2	4120
	11th to 20th	Day	47% 5% 14% 23% 10% 1	4402
	21st to end	Day	38% 4 14% 24% 17% 3	4837
June	1st to 10th	Day	44% 5% 12% 24% 14% 1	2660
	11th to 20th	Day	38% 5% 13% 27% 16% 1	2746
	21st to end	Day	43% 5% 13% 24% 15% 1	2850
July	1st to 10th	Day	34% 5% 14% 26% 19% 2	2605
	11th to 20th	Day	38% 7% 13% 30% 11% 1	2445
	21st to end	Day	41% 7% 13% 25% 13% 1	2450
August	1st to 10th	Day	37% 6% 16% 26% 12% 2	2314
	11th to 20th	Day	36% 7% 18% 28% 10% 1	2303
	21st to end	Day	39% 6% 15% 27% 12% 1	2491
September	1st to 10th	Day	42% 6% 12% 29% 11% 2	2160
	11th to 20th	Day	40% 4 13% 29% 12% 1	2052
	21st to end	Day	46% 6% 13% 27% 8%	1945
October	1st to 10th	Day	51% 4 13% 20% 11% 1	1800
	11th to 20th	Day	59% 4 13% 18% 5% 1	1800
	21st to end	Day	65% 4 13% 12% 5%	1980
November	1st to 10th	Day	55% 5% 14% 20% 6% 1	1573
	11th to 20th	Day	61% 6% 13% 13% 6% 1	1520
	21st to end	Day	68% 6% 11% 13% 2	1520
December	1st to 10th	Day	73% 4 11% 10% 2	1520
	11th to 20th	Day	67% 6% 11% 12% 3	1906
	21st to end	Day	79% 2 9% 8% 1	2772
January	1st to 10th	Night	69% 4 14% 10% 3	4429
	11th to 20th	Night	71% 4 12% 10% 3	4239
	21st to end	Night	71% 3 11% 10% 3 1	4532
February	1st to 10th	Night	64% 5% 10% 17% 3 1	2470
	11th to 20th	Night	60% 5% 11% 18% 6%	2405
	21st to end	Night	59% 3 12% 17% 8% 1	1995
March	1st to 10th	Night	55% 2 11% 22% 8% 1	3418
	11th to 20th	Night	51% 3 14% 23% 8% 1	3480
	21st to end	Night	51% 3 9% 22% 13% 1	3817
April	1st to 10th	Night	55% 4 9% 20% 12% 1	1936
	11th to 20th	Night	47% 5% 9% 21% 16% 2	1800
	21st to end	Night	51% 3 10% 18% 16% 2	1710
May	1st to 10th	Night	45% 3 13% 20% 17% 3	2840
	11th to 20th	Night	43% 4 14% 25% 12% 2	2496
	21st to end	Night	34% 4 14% 27% 19% 2	2739
June	1st to 10th	Night	42% 5% 11% 25% 15% 2	1520
	11th to 20th	Night	37% 5% 12% 24% 21% 1	1426
	21st to end	Night	39% 5% 13% 26% 15% 1	1330
July	1st to 10th	Night	28% 5% 11% 31% 23% 2	1268
	11th to 20th	Night	34% 4 13% 33% 15% 1	1392
	21st to end	Night	33% 6% 13% 31% 15% 2	1624
August	1st to 10th	Night	32% 4 19% 31% 14% 1	1600
	11th to 20th	Night	29% 6% 19% 30% 16% 1	1598
	21st to end	Night	37% 7% 15% 26% 14% 1	1846
September	1st to 10th	Night	37% 5% 15% 29% 13% 2	1800
	11th to 20th	Night	34% 4 13% 33% 15% 1	1906
	21st to end	Night	44% 4 13% 28% 10%	2014
October	1st to 10th	Night	48% 5% 12% 21% 13% 1	2160
	11th to 20th	Night	55% 5% 13% 21% 7%	2160
	21st to end	Night	61% 6% 11% 15% 8%	2376
November	1st to 10th	Night	51% 6% 12% 23% 8% 1	2499
	11th to 20th	Night	60% 5% 13% 15% 6% 1	2660
	21st to end	Night	64% 5% 15% 15% 1	2660
December	1st to 10th	Night	70% 4 13% 10% 3	2660
	11th to 20th	Night	67% 5% 13% 12% 2	3288
	21st to end	Night	79% 3 9% 8% 2	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	15% 11% 39% 23% 10% 2	180
	11th to 20th	Day	19% 11% 40% 22% 7% 2	237
	21st to end	Day	21% 8% 35% 28% 7% 1	297
February	1st to 10th	Day	17% 14% 44% 16% 7% 1	270
	11th to 20th	Day	18% 16% 39% 24% 2	270
	21st to end	Day	24% 19% 32% 23% 2	231
March	1st to 10th	Day	18% 10% 37% 25% 9%	460
	11th to 20th	Day	17% 12% 35% 26% 8% 1	460
	21st to end	Day	25% 8% 32% 23% 11% 1	506
April	1st to 10th	Day	19% 15% 30% 25% 9% 2	460
	11th to 20th	Day	26% 10% 28% 19% 12% 5%	452
	21st to end	Day	23% 10% 25% 26% 12% 4	460
May	1st to 10th	Day	17% 7% 25% 30% 16% 5%	463
	11th to 20th	Day	15% 6% 21% 31% 20% 7%	487
	21st to end	Day	15% 4 22% 31% 21% 7%	529
June	1st to 10th	Day	16% 6% 24% 29% 22% 3	490
	11th to 20th	Day	13% 6% 23% 31% 23% 5%	576
	21st to end	Day	17% 5% 24% 31% 17% 5%	680
July	1st to 10th	Day	10% 4 18% 32% 29% 8%	590
	11th to 20th	Day	13% 2 20% 27% 27% 11%	444
	21st to end	Day	12% 2 15% 39% 22% 10%	488
August	1st to 10th	Day	10% 2 17% 27% 29% 15%	446
	11th to 20th	Day	9% 3 16% 28% 29% 15%	439
	21st to end	Day	14% 3 21% 27% 24% 11%	495
September	1st to 10th	Day	14% 4 20% 26% 24% 12%	450
	11th to 20th	Day	11% 4 19% 27% 23% 16%	450
	21st to end	Day	14% 6% 25% 25% 21% 8%	450
October	1st to 10th	Day	20% 7% 24% 24% 16% 9%	450
	11th to 20th	Day	23% 10% 34% 23% 8% 1	450
	21st to end	Day	31% 9% 31% 21% 7%	495
November	1st to 10th	Day	21% 16% 29% 21% 11% 1	235
	11th to 20th	Day	21% 18% 32% 21% 6% 2	180
	21st to end	Day	27% 13% 37% 19% 4	180
December	1st to 10th	Day	19% 17% 38% 21% 4 1	180
	11th to 20th	Day	21% 18% 37% 17% 6% 1	180
	21st to end	Day	27% 8% 41% 21% 4	198
January	1st to 10th	Night	22% 10% 40% 20% 7% 1	760
	11th to 20th	Night	25% 8% 33% 27% 7%	760
	21st to end	Night	19% 6% 33% 32% 9% 1	836
February	1st to 10th	Night	19% 9% 41% 27% 4	760
	11th to 20th	Night	19% 10% 37% 29% 6%	743
	21st to end	Night	19% 10% 36% 29% 5%	628
March	1st to 10th	Night	18% 9% 36% 31% 7%	760
	11th to 20th	Night	17% 10% 36% 29% 7% 1	760
	21st to end	Night	20% 8% 31% 29% 11%	836
April	1st to 10th	Night	23% 9% 31% 30% 6%	760
	11th to 20th	Night	20% 7% 31% 30% 10% 2	676
	21st to end	Night	21% 7% 27% 31% 13%	570
May	1st to 10th	Night	18% 2 23% 38% 17% 2	570
	11th to 20th	Night	17% 4 24% 40% 14% 1	374
	21st to end	Night	10% 5% 20% 43% 21% 1	411
June	1st to 10th	Night	16% 5% 24% 40% 14% 1	380
	11th to 20th	Night	9% 6% 20% 47% 17% 1	380
	21st to end	Night	14% 3 19% 42% 19% 2	380
July	1st to 10th	Night	6% 5% 16% 48% 25% 1	354
	11th to 20th	Night	11% 4 21% 41% 22% 2	348
	21st to end	Night	10% 3 17% 44% 25% 1	540
August	1st to 10th	Night	10% 3 13% 42% 30% 2	537
	11th to 20th	Night	5% 2 14% 38% 36% 4	534
	21st to end	Night	12% 3 20% 34% 28% 3	658
September	1st to 10th	Night	13% 5% 18% 35% 23% 6%	720
	11th to 20th	Night	14% 4 19% 32% 23% 7%	720
	21st to end	Night	18% 6% 21% 30% 19% 5%	720
October	1st to 10th	Night	20% 5% 28% 28% 17% 3	720
	11th to 20th	Night	22% 11% 30% 27% 9% 1	720
	21st to end	Night	29% 10% 30% 25% 6%	792
November	1st to 10th	Night	22% 10% 28% 27% 12% 1	740
	11th to 20th	Night	23% 14% 34% 21% 8% 1	760
	21st to end	Night	26% 13% 32% 24% 4	760
December	1st to 10th	Night	27% 13% 37% 18% 5% 1	760
	11th to 20th	Night	22% 12% 38% 21% 5% 1	760
	21st to end	Night	28% 10% 34% 24% 3	836

Page generated at 2024-06-29 07:12:34. Version ac07

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