Gittins Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gittins Observatory clear sky chart from 2005-11-06 to 2024-10-24.

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% 4 4 4 4 6% 8% 42%	101187
	Night	13% 8% 3 6% 4 4 4 3 5% 6% 43%	97667
Transparency	Day	40% 6% 12% 25% 15% 2	100980
	Night	42% 5% 11% 24% 16% 2	97545
Seeing	Day	16% 11% 28% 26% 15% 4	15651
	Night	16% 11% 30% 29% 12% 1	25445

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	11% 12% 6% 12% 5% 4 5% 3 5% 7% 31%	2527
	11th to 20th	Day	13% 10% 4 9% 7% 8% 4 4 5% 5% 31%	2726
	21st to end	Day	19% 17% 8% 8% 6% 3 3 3 3 5% 26%	3135
February	1st to 10th	Day	15% 12% 3 9% 5% 4 4 3 5% 6% 33%	1710
	11th to 20th	Day	14% 10% 2 7% 5% 5% 5% 4 5% 7% 35%	1783
	21st to end	Day	16% 12% 3 6% 4 3 4 4 4 6% 37%	1570
March	1st to 10th	Day	16% 12% 3 6% 4 3 3 3 4 5% 42%	3212
	11th to 20th	Day	10% 8% 2 5% 4 4 4 4 5% 7% 47%	3480
	21st to end	Day	16% 10% 4 8% 5% 4 5% 3 6% 6% 33%	3991
April	1st to 10th	Day	13% 8% 2 7% 5% 5% 4 4 5% 7% 41%	2280
	11th to 20th	Day	16% 9% 3 6% 4 4 4 2 4 7% 41%	2254
	21st to end	Day	19% 7% 2 7% 4 4 5% 3 6% 8% 36%	2280
May	1st to 10th	Day	13% 8% 3 8% 5% 5% 5% 5% 7% 9% 33%	3930
	11th to 20th	Day	17% 8% 2 6% 5% 4 4 4 5% 7% 38%	4399
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 7% 47%	4824
June	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 7% 10% 47%	2660
	11th to 20th	Day	8% 3 2 5% 4 5% 5% 4 7% 8% 49%	2660
	21st to end	Day	6% 4 2 5% 6% 5% 5% 4 7% 10% 46%	2660
July	1st to 10th	Day	13% 6% 3 6% 3 4 5% 4 8% 10% 39%	4440
	11th to 20th	Day	5% 4 2 6% 5% 4 5% 4 6% 10% 49%	4440
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 5% 8% 11% 40%	4571
August	1st to 10th	Day	5% 4 2 5% 4 5% 5% 5% 7% 10% 49%	4104
	11th to 20th	Day	12% 6% 2 5% 5% 5% 5% 4 7% 9% 42%	3793
	21st to end	Day	5% 4 2 5% 4 4 4 4 7% 11% 50%	4180
September	1st to 10th	Day	13% 4 2 4 3 3 4 3 5% 6% 53%	2280
	11th to 20th	Day	10% 4 2 5% 3 4 4 4 6% 7% 51%	2277
	21st to end	Day	8% 5% 2 6% 4 3 4 4 5% 9% 51%	2043
October	1st to 10th	Day	10% 5% 2 5% 3 3 3 3 4 6% 54%	1900
	11th to 20th	Day	15% 6% 3 5% 3 3 3 3 4 6% 49%	1900
	21st to end	Day	18% 9% 2 5% 3 3 3 2 4 4 46%	2002
November	1st to 10th	Day	11% 6% 2 4 4 4 4 3 4 6% 54%	1672
	11th to 20th	Day	14% 8% 3 7% 3 3 3 3 5% 6% 45%	1710
	21st to end	Day	16% 11% 3 7% 4 3 2 3 5% 5% 40%	1573
December	1st to 10th	Day	12% 12% 4 6% 5% 3 4 4 4 6% 40%	1520
	11th to 20th	Day	14% 9% 3 7% 5% 4 5% 3 5% 6% 39%	1918
	21st to end	Day	20% 14% 5% 10% 6% 4 4 3 4 5% 24%	2783
January	1st to 10th	Night	13% 12% 6% 10% 5% 5% 5% 3 4 4 33%	4428
	11th to 20th	Night	12% 14% 5% 11% 5% 5% 7% 6% 4 4 27%	4239
	21st to end	Night	22% 17% 5% 9% 4 3 3 3 5% 6% 23%	4532
February	1st to 10th	Night	15% 12% 5% 9% 5% 4 4 3 4 6% 33%	2470
	11th to 20th	Night	14% 8% 4 7% 5% 4 5% 3 4 6% 41%	2283
	21st to end	Night	16% 10% 3 6% 3 4 3 2 5% 5% 43%	1884
March	1st to 10th	Night	21% 11% 2 5% 4 3 3 3 3 4 42%	3669
	11th to 20th	Night	14% 6% 2 4 4 3 3 3 4 5% 51%	3480
	21st to end	Night	18% 11% 4 8% 5% 4 3 3 5% 6% 32%	3640
April	1st to 10th	Night	13% 7% 3 5% 5% 4 4 3 5% 7% 45%	1900
	11th to 20th	Night	13% 7% 2 5% 4 3 5% 4 4 7% 45%	1875
	21st to end	Night	18% 7% 2 7% 4 4 4 3 5% 5% 41%	1900
May	1st to 10th	Night	16% 8% 3 6% 4 4 5% 4 6% 8% 37%	2964
	11th to 20th	Night	14% 8% 2 6% 4 4 4 3 5% 7% 42%	2506
	21st to end	Night	9% 5% 2 6% 4 3 4 4 6% 10% 48%	2743
June	1st to 10th	Night	7% 4 2 5% 3 4 4 3 7% 9% 51%	1520
	11th to 20th	Night	6% 5% 1 5% 5% 3 4 5% 6% 7% 52%	1520
	21st to end	Night	6% 3 1 5% 4 5% 4 4 7% 9% 51%	1520
July	1st to 10th	Night	11% 7% 3 6% 4 5% 5% 4 6% 8% 42%	2530
	11th to 20th	Night	4 3 1 4 3 3 4 3 5% 9% 60%	2530
	21st to end	Night	8% 6% 2 7% 5% 5% 5% 4 7% 10% 42%	2988
August	1st to 10th	Night	6% 3 1 4 3 4 3 3 5% 9% 60%	2836
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 5% 7% 50%	3037
	21st to end	Night	5% 3 1 4 3 4 4 3 7% 10% 55%	3476
September	1st to 10th	Night	12% 5% 2 3 2 3 3 4 6% 6% 55%	1900
	11th to 20th	Night	8% 5% 2 5% 3 4 4 4 6% 8% 51%	1900
	21st to end	Night	7% 5% 2 5% 3 4 3 3 6% 7% 55%	2115
October	1st to 10th	Night	9% 4 2 5% 3 3 3 3 4 7% 58%	2280
	11th to 20th	Night	13% 5% 2 5% 3 2 3 3 4 6% 53%	2280
	21st to end	Night	18% 7% 2 5% 3 4 3 3 4 5% 45%	2420
November	1st to 10th	Night	9% 7% 2 5% 3 3 3 3 4 6% 55%	2406
	11th to 20th	Night	13% 6% 3 5% 4 4 3 3 5% 6% 49%	2470
	21st to end	Night	16% 10% 3 6% 4 3 3 4 4 5% 43%	2603
December	1st to 10th	Night	14% 11% 4 7% 5% 4 5% 3 6% 6% 35%	2660
	11th to 20th	Night	16% 9% 3 7% 4 3 4 3 5% 6% 41%	3279
	21st to end	Night	20% 19% 6% 10% 6% 5% 4 2 4 4 21%	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	52% 5% 10% 22% 9% 1	2528
	11th to 20th	Day	52% 6% 13% 19% 10%	2726
	21st to end	Day	62% 4 9% 14% 10% 1	3135
February	1st to 10th	Day	51% 6% 11% 21% 10% 2	1710
	11th to 20th	Day	47% 6% 12% 19% 14% 2	1792
	21st to end	Day	47% 4 9% 24% 13% 3	1570
March	1st to 10th	Day	46% 4 8% 22% 18% 2	3212
	11th to 20th	Day	36% 5% 13% 26% 17% 3	3480
	21st to end	Day	50% 8% 17% 19% 6% 1	3991
April	1st to 10th	Day	42% 6% 10% 25% 15% 1	2280
	11th to 20th	Day	44% 5% 9% 26% 14% 3	2254
	21st to end	Day	46% 6% 12% 21% 14% 1	2280
May	1st to 10th	Day	44% 9% 14% 23% 10% 1	3965
	11th to 20th	Day	46% 7% 10% 26% 11% 1	4403
	21st to end	Day	35% 7% 10% 24% 23% 1	4837
June	1st to 10th	Day	30% 8% 15% 29% 15% 3	2660
	11th to 20th	Day	30% 7% 12% 26% 21% 3	2660
	21st to end	Day	31% 10% 15% 24% 17% 3	2660
July	1st to 10th	Day	39% 7% 11% 28% 13% 2	4371
	11th to 20th	Day	30% 6% 14% 29% 19% 2	4365
	21st to end	Day	34% 9% 19% 26% 11% 1	4427
August	1st to 10th	Day	29% 7% 15% 35% 14% 1	4090
	11th to 20th	Day	38% 6% 13% 27% 15% 1	3830
	21st to end	Day	27% 7% 16% 32% 14% 4	4179
September	1st to 10th	Day	31% 7% 11% 25% 22% 5%	2280
	11th to 20th	Day	31% 5% 9% 28% 22% 4	2277
	21st to end	Day	30% 5% 12% 27% 23% 3	2043
October	1st to 10th	Day	31% 6% 9% 25% 26% 4	1900
	11th to 20th	Day	36% 4 9% 23% 24% 4	1900
	21st to end	Day	43% 4 8% 24% 18% 3	2002
November	1st to 10th	Day	32% 4 12% 26% 20% 5%	1672
	11th to 20th	Day	40% 4 9% 24% 19% 4	1710
	21st to end	Day	47% 5% 10% 26% 13%	1573
December	1st to 10th	Day	45% 6% 13% 23% 12% 1	1520
	11th to 20th	Day	45% 6% 11% 25% 11% 2	1915
	21st to end	Day	62% 6% 10% 15% 7% 1	2783
January	1st to 10th	Night	54% 4 10% 23% 8% 1	4428
	11th to 20th	Night	59% 4 9% 19% 8%	4239
	21st to end	Night	63% 4 9% 18% 6% 1	4532
February	1st to 10th	Night	53% 5% 10% 19% 11% 2	2470
	11th to 20th	Night	45% 4 10% 23% 15% 2	2284
	21st to end	Night	45% 4 11% 24% 14% 3	1884
March	1st to 10th	Night	47% 4 8% 24% 16% 1	3669
	11th to 20th	Night	36% 5% 10% 25% 21% 4	3480
	21st to end	Night	53% 7% 10% 24% 6%	3640
April	1st to 10th	Night	38% 6% 11% 25% 16% 4	1900
	11th to 20th	Night	38% 5% 10% 23% 18% 4	1875
	21st to end	Night	45% 5% 8% 22% 18% 2	1900
May	1st to 10th	Night	43% 8% 16% 20% 12% 1	2994
	11th to 20th	Night	41% 7% 12% 27% 13%	2507
	21st to end	Night	31% 7% 14% 21% 23% 3	2751
June	1st to 10th	Night	28% 7% 15% 28% 19% 4	1520
	11th to 20th	Night	29% 7% 11% 23% 26% 4	1520
	21st to end	Night	27% 7% 17% 25% 18% 6%	1520
July	1st to 10th	Night	38% 7% 10% 31% 12% 2	2490
	11th to 20th	Night	21% 6% 11% 37% 22% 2	2482
	21st to end	Night	35% 7% 17% 26% 14% 1	2893
August	1st to 10th	Night	22% 6% 17% 36% 18% 1	2826
	11th to 20th	Night	33% 5% 11% 28% 22% 1	3066
	21st to end	Night	24% 5% 18% 32% 17% 4	3476
September	1st to 10th	Night	29% 5% 10% 24% 25% 7%	1900
	11th to 20th	Night	30% 6% 9% 24% 26% 5%	1900
	21st to end	Night	29% 6% 8% 26% 27% 4	2115
October	1st to 10th	Night	28% 5% 10% 24% 28% 5%	2280
	11th to 20th	Night	33% 5% 8% 28% 22% 5%	2280
	21st to end	Night	41% 5% 8% 20% 22% 3	2420
November	1st to 10th	Night	30% 5% 13% 26% 20% 6%	2406
	11th to 20th	Night	36% 4 9% 28% 19% 4	2470
	21st to end	Night	44% 4 11% 24% 15% 2	2603
December	1st to 10th	Night	50% 5% 12% 22% 10% 1	2660
	11th to 20th	Night	46% 4 10% 24% 15% 1	3281
	21st to end	Night	67% 5% 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	24% 21% 33% 18% 5%	270
	11th to 20th	Day	30% 20% 35% 14% 1	270
	21st to end	Day	18% 24% 39% 16% 3	297
February	1st to 10th	Day	27% 19% 39% 13% 2	270
	11th to 20th	Day	26% 22% 33% 14% 4	270
	21st to end	Day	27% 20% 39% 13% 1	225
March	1st to 10th	Day	20% 26% 40% 13% 1	270
	11th to 20th	Day	29% 18% 34% 16% 2	270
	21st to end	Day	33% 18% 32% 14% 3	397
April	1st to 10th	Day	21% 14% 39% 19% 5% 1	460
	11th to 20th	Day	23% 17% 31% 20% 8% 1	452
	21st to end	Day	20% 20% 36% 20% 4 1	460
May	1st to 10th	Day	17% 16% 36% 23% 7% 1	503
	11th to 20th	Day	19% 12% 29% 26% 13% 1	675
	21st to end	Day	14% 10% 30% 27% 13% 6%	734
June	1st to 10th	Day	8% 6% 26% 31% 22% 7%	680
	11th to 20th	Day	9% 5% 25% 37% 20% 4	680
	21st to end	Day	7% 7% 31% 37% 15% 3	680
July	1st to 10th	Day	11% 4 15% 32% 27% 11%	671
	11th to 20th	Day	6% 4 20% 38% 26% 6%	668
	21st to end	Day	9% 2 20% 34% 28% 6%	739
August	1st to 10th	Day	8% 3 20% 36% 25% 8%	676
	11th to 20th	Day	10% 3 18% 34% 26% 8%	519
	21st to end	Day	9% 2 15% 34% 31% 8%	539
September	1st to 10th	Day	13% 4 18% 27% 29% 9%	490
	11th to 20th	Day	9% 3 18% 34% 27% 10%	490
	21st to end	Day	11% 9% 24% 29% 20% 7%	443
October	1st to 10th	Day	12% 10% 29% 29% 14% 5%	300
	11th to 20th	Day	19% 20% 31% 22% 8%	300
	21st to end	Day	28% 18% 32% 17% 5%	306
November	1st to 10th	Day	12% 13% 40% 22% 10% 3	270
	11th to 20th	Day	23% 16% 34% 20% 6% 1	270
	21st to end	Day	26% 14% 35% 20% 4 1	270
December	1st to 10th	Day	14% 19% 41% 17% 7% 2	270
	11th to 20th	Day	22% 18% 40% 17% 3	270
	21st to end	Day	25% 26% 34% 14% 1	297
January	1st to 10th	Night	18% 18% 38% 21% 5%	950
	11th to 20th	Night	22% 18% 35% 19% 5%	950
	21st to end	Night	20% 18% 38% 22% 2	1045
February	1st to 10th	Night	22% 17% 37% 23% 2	950
	11th to 20th	Night	20% 17% 37% 22% 3	808
	21st to end	Night	23% 21% 35% 19% 2	628
March	1st to 10th	Night	21% 17% 39% 19% 3	722
	11th to 20th	Night	23% 11% 35% 25% 6%	570
	21st to end	Night	25% 13% 34% 23% 4	627
April	1st to 10th	Night	16% 19% 36% 26% 4	570
	11th to 20th	Night	16% 15% 34% 26% 8% 1	563
	21st to end	Night	21% 11% 39% 25% 5%	570
May	1st to 10th	Night	16% 8% 34% 33% 8% 1	570
	11th to 20th	Night	16% 9% 28% 33% 13% 1	561
	21st to end	Night	12% 5% 26% 36% 19% 2	617
June	1st to 10th	Night	7% 4 25% 41% 22% 1	570
	11th to 20th	Night	8% 3 25% 42% 20% 2	570
	21st to end	Night	5% 2 27% 43% 21% 1	570
July	1st to 10th	Night	11% 2 13% 35% 33% 5%	555
	11th to 20th	Night	6% 2 17% 45% 27% 3	552
	21st to end	Night	7% 1 15% 43% 32% 2	624
August	1st to 10th	Night	9% 2 9% 44% 32% 3	567
	11th to 20th	Night	8% 2 15% 39% 32% 4	564
	21st to end	Night	6% 1 15% 37% 39% 3	627
September	1st to 10th	Night	13% 3 17% 36% 26% 5%	570
	11th to 20th	Night	10% 2 18% 36% 30% 5%	570
	21st to end	Night	11% 7% 23% 33% 23% 4	742
October	1st to 10th	Night	9% 6% 29% 31% 21% 3	760
	11th to 20th	Night	16% 11% 34% 28% 11% 1	760
	21st to end	Night	23% 14% 32% 24% 6%	805
November	1st to 10th	Night	13% 11% 40% 26% 10%	740
	11th to 20th	Night	18% 14% 37% 25% 6% 1	760
	21st to end	Night	21% 15% 36% 22% 5%	893
December	1st to 10th	Night	20% 16% 37% 22% 5% 1	950
	11th to 20th	Night	23% 14% 32% 26% 5%	950
	21st to end	Night	25% 18% 34% 21% 2	1045

Page generated at 2024-10-21 01:19:59. Version ac07

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