ForestGate Farm Observatory
Clear Sky Chart
History

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

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	14% 12% 4 10% 5% 5% 5% 4 5% 6% 31%	101599
	Night	13% 12% 4 10% 6% 5% 4 3 5% 6% 30%	97506
Transparency	Day	54% 2 11% 22% 10% 1	101358
	Night	55% 2 11% 21% 9% 1	97365
Seeing	Day	23% 15% 33% 19% 8% 2	16067
	Night	21% 13% 32% 25% 9% 1	25930

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	10% 16% 9% 21% 8% 5% 5% 4 4 5% 14%	2527
	11th to 20th	Day	8% 19% 5% 15% 11% 10% 8% 4 5% 5% 11%	2530
	21st to end	Day	9% 19% 9% 19% 7% 5% 5% 3 4 4 14%	2783
February	1st to 10th	Day	8% 14% 6% 12% 8% 7% 7% 5% 7% 5% 22%	1643
	11th to 20th	Day	8% 13% 5% 15% 8% 7% 6% 4 6% 6% 23%	1749
	21st to end	Day	12% 14% 6% 13% 7% 7% 5% 4 4 6% 22%	1570
March	1st to 10th	Day	11% 12% 3 13% 5% 4 4 3 4 5% 35%	3118
	11th to 20th	Day	8% 16% 5% 14% 9% 4 4 3 5% 6% 26%	3278
	21st to end	Day	18% 15% 6% 18% 6% 4 3 3 4 5% 18%	4165
April	1st to 10th	Day	16% 16% 5% 10% 6% 5% 5% 3 5% 5% 26%	2280
	11th to 20th	Day	19% 15% 5% 10% 4 4 3 3 4 4 28%	2254
	21st to end	Day	17% 13% 4 8% 5% 4 4 4 5% 6% 30%	2451
May	1st to 10th	Day	18% 11% 3 7% 5% 4 4 3 4 6% 36%	4382
	11th to 20th	Day	14% 9% 3 6% 4 5% 4 4 5% 7% 38%	4399
	21st to end	Day	14% 10% 3 9% 5% 5% 5% 4 5% 7% 34%	4837
June	1st to 10th	Day	14% 7% 3 7% 4 4 5% 4 7% 8% 37%	2660
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 5% 7% 7% 34%	2660
	21st to end	Day	14% 7% 2 7% 5% 5% 5% 5% 7% 8% 35%	2660
July	1st to 10th	Day	13% 5% 2 6% 4 5% 6% 5% 7% 9% 38%	4440
	11th to 20th	Day	8% 5% 2 6% 4 4 6% 4 6% 8% 47%	4440
	21st to end	Day	8% 6% 2 6% 4 4 4 4 6% 9% 46%	4814
August	1st to 10th	Day	10% 7% 3 8% 5% 5% 6% 4 7% 8% 37%	4423
	11th to 20th	Day	14% 7% 2 5% 4 4 4 3 5% 7% 45%	4089
	21st to end	Day	16% 8% 2 6% 4 4 4 3 5% 8% 40%	4180
September	1st to 10th	Day	14% 8% 2 6% 4 4 5% 4 5% 6% 41%	2280
	11th to 20th	Day	14% 8% 2 7% 6% 4 4 4 5% 8% 39%	2199
	21st to end	Day	18% 10% 3 7% 4 4 5% 3 4 7% 34%	2090
October	1st to 10th	Day	18% 11% 3 7% 4 4 4 3 6% 7% 33%	1957
	11th to 20th	Day	21% 19% 4 9% 5% 5% 4 3 4 6% 20%	1845
	21st to end	Day	21% 19% 5% 9% 5% 4 4 3 4 5% 21%	1881
November	1st to 10th	Day	16% 17% 4 9% 5% 4 5% 2 5% 5% 26%	1672
	11th to 20th	Day	16% 17% 7% 16% 7% 5% 4 2 4 5% 17%	1606
	21st to end	Day	14% 14% 9% 17% 8% 5% 3 3 5% 6% 16%	1520
December	1st to 10th	Day	9% 17% 7% 19% 9% 5% 5% 4 4 4 16%	1520
	11th to 20th	Day	14% 17% 6% 17% 10% 6% 5% 2 5% 5% 13%	1914
	21st to end	Day	19% 24% 8% 15% 5% 4 3 2 3 4 12%	2783
January	1st to 10th	Night	13% 16% 6% 20% 8% 4 4 3 4 5% 18%	4428
	11th to 20th	Night	9% 17% 6% 14% 10% 9% 6% 4 6% 6% 13%	4440
	21st to end	Night	10% 17% 7% 19% 8% 6% 4 4 5% 5% 16%	4884
February	1st to 10th	Night	8% 13% 6% 12% 7% 7% 7% 4 6% 7% 23%	2532
	11th to 20th	Night	9% 10% 4 12% 10% 8% 7% 4 6% 6% 24%	2317
	21st to end	Night	12% 17% 5% 10% 8% 4 5% 4 6% 6% 24%	1884
March	1st to 10th	Night	9% 8% 4 10% 6% 6% 5% 4 6% 10% 33%	3722
	11th to 20th	Night	8% 11% 7% 14% 6% 5% 5% 3 4 7% 31%	3712
	21st to end	Night	17% 12% 7% 12% 7% 5% 5% 3 5% 5% 22%	3466
April	1st to 10th	Night	16% 14% 4 10% 5% 5% 4 3 5% 6% 27%	1900
	11th to 20th	Night	20% 10% 4 9% 4 3 4 3 5% 6% 33%	1875
	21st to end	Night	17% 10% 3 9% 6% 5% 4 3 4 6% 34%	1729
May	1st to 10th	Night	16% 10% 3 6% 4 4 3 3 4 7% 39%	2564
	11th to 20th	Night	12% 8% 3 7% 5% 4 4 4 4 5% 43%	2506
	21st to end	Night	15% 8% 3 6% 5% 5% 5% 4 7% 7% 35%	2750
June	1st to 10th	Night	12% 7% 2 6% 4 4 5% 4 5% 7% 44%	1520
	11th to 20th	Night	13% 7% 2 6% 6% 5% 4 4 6% 7% 40%	1520
	21st to end	Night	14% 7% 2 6% 4 4 4 4 7% 8% 42%	1520
July	1st to 10th	Night	13% 6% 2 5% 5% 3 4 3 6% 9% 44%	2530
	11th to 20th	Night	7% 5% 2 5% 4 3 4 4 5% 8% 54%	2530
	21st to end	Night	8% 6% 2 5% 3 4 4 3 6% 7% 53%	2750
August	1st to 10th	Night	12% 8% 2 6% 5% 4 4 3 5% 6% 45%	2517
	11th to 20th	Night	13% 5% 2 5% 3 4 3 3 4 6% 51%	2741
	21st to end	Night	15% 8% 2 6% 3 3 3 2 4 6% 46%	3476
September	1st to 10th	Night	12% 7% 2 5% 4 3 3 3 6% 6% 49%	1900
	11th to 20th	Night	12% 7% 2 6% 4 5% 4 4 6% 7% 44%	1961
	21st to end	Night	16% 9% 2 6% 5% 4 4 4 4 8% 37%	2090
October	1st to 10th	Night	16% 10% 2 7% 3 4 4 4 5% 6% 39%	2221
	11th to 20th	Night	18% 13% 3 7% 4 5% 4 5% 6% 6% 28%	2334
	21st to end	Night	19% 18% 4 8% 5% 5% 4 4 4 6% 23%	2717
November	1st to 10th	Night	15% 14% 5% 7% 5% 5% 5% 4 5% 7% 28%	2413
	11th to 20th	Night	14% 18% 6% 15% 6% 5% 4 3 4 4 21%	2570
	21st to end	Night	14% 15% 7% 16% 7% 5% 4 4 5% 6% 19%	2660
December	1st to 10th	Night	11% 15% 8% 15% 7% 5% 4 4 5% 6% 19%	2660
	11th to 20th	Night	11% 15% 7% 15% 9% 6% 5% 3 5% 6% 19%	3283
	21st to end	Night	22% 22% 6% 13% 6% 4 4 2 3 3 13%	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	74% 1 8% 14% 3	2528
	11th to 20th	Day	76% 1 9% 11% 3	2530
	21st to end	Day	75% 1 10% 10% 4 1	2783
February	1st to 10th	Day	63% 2 9% 18% 7% 1	1643
	11th to 20th	Day	62% 1 9% 21% 7%	1758
	21st to end	Day	65% 1 8% 15% 9% 1	1570
March	1st to 10th	Day	54% 1 11% 19% 14% 1	3120
	11th to 20th	Day	61% 1 12% 17% 8% 1	3278
	21st to end	Day	70% 1 8% 14% 6% 1	4165
April	1st to 10th	Day	62% 1 8% 19% 9%	2280
	11th to 20th	Day	61% 2 6% 22% 9% 1	2254
	21st to end	Day	56% 2 7% 20% 13% 2	2451
May	1st to 10th	Day	52% 2 7% 22% 16% 2	4394
	11th to 20th	Day	47% 1 9% 30% 12% 1	4403
	21st to end	Day	51% 2 10% 20% 16% 2	4837
June	1st to 10th	Day	44% 2 12% 27% 14% 1	2660
	11th to 20th	Day	48% 3 11% 22% 15% 1	2660
	21st to end	Day	46% 4 13% 25% 11% 1	2660
July	1st to 10th	Day	41% 5% 14% 26% 12% 1	4371
	11th to 20th	Day	34% 4 14% 32% 15% 2	4365
	21st to end	Day	34% 4 11% 33% 17% 1	4662
August	1st to 10th	Day	44% 4 14% 26% 11% 1	4408
	11th to 20th	Day	38% 3 17% 31% 11%	4131
	21st to end	Day	44% 4 14% 24% 13% 1	4179
September	1st to 10th	Day	43% 3 11% 30% 13%	2280
	11th to 20th	Day	46% 2 19% 26% 7% 1	2199
	21st to end	Day	52% 1 12% 26% 8%	2090
October	1st to 10th	Day	51% 2 11% 26% 9%	1957
	11th to 20th	Day	67% 2 9% 15% 7% 1	1845
	21st to end	Day	68% 2 9% 16% 5%	1881
November	1st to 10th	Day	61% 1 10% 20% 7% 1	1672
	11th to 20th	Day	72% 1 9% 12% 5%	1606
	21st to end	Day	71% 3 11% 12% 3 1	1520
December	1st to 10th	Day	72% 1 9% 15% 3	1520
	11th to 20th	Day	75% 1 8% 12% 4	1915
	21st to end	Day	80% 4 13% 3	2783
January	1st to 10th	Night	71% 1 7% 17% 3	4428
	11th to 20th	Night	73% 1 9% 14% 3	4440
	21st to end	Night	71% 1 10% 15% 3	4884
February	1st to 10th	Night	60% 2 8% 19% 11% 1	2532
	11th to 20th	Night	61% 3 8% 20% 6% 1	2318
	21st to end	Night	61% 1 11% 19% 8%	1884
March	1st to 10th	Night	49% 2 17% 23% 10% 1	3733
	11th to 20th	Night	55% 1 9% 25% 9% 1	3713
	21st to end	Night	65% 1 8% 16% 8% 2	3466
April	1st to 10th	Night	58% 2 7% 18% 13% 1	1900
	11th to 20th	Night	53% 3 7% 23% 12% 2	1875
	21st to end	Night	54% 2 8% 19% 15% 1	1729
May	1st to 10th	Night	47% 2 11% 24% 15% 1	2571
	11th to 20th	Night	45% 2 10% 27% 16% 2	2507
	21st to end	Night	49% 3 14% 19% 13% 3	2751
June	1st to 10th	Night	40% 3 12% 31% 12% 1	1520
	11th to 20th	Night	44% 3 13% 24% 14% 1	1520
	21st to end	Night	39% 3 17% 28% 11% 1	1520
July	1st to 10th	Night	39% 4 18% 23% 13% 3	2490
	11th to 20th	Night	28% 4 16% 38% 14% 1	2482
	21st to end	Night	31% 3 14% 32% 19% 1	2662
August	1st to 10th	Night	40% 3 14% 24% 17% 2	2508
	11th to 20th	Night	36% 4 17% 28% 13% 2	2765
	21st to end	Night	41% 4 13% 26% 15% 1	3476
September	1st to 10th	Night	36% 2 15% 32% 14% 1	1900
	11th to 20th	Night	40% 3 16% 32% 9%	1961
	21st to end	Night	47% 3 14% 26% 9% 1	2090
October	1st to 10th	Night	46% 2 12% 30% 10% 1	2221
	11th to 20th	Night	57% 2 12% 21% 8% 1	2334
	21st to end	Night	63% 3 11% 18% 6%	2717
November	1st to 10th	Night	57% 2 12% 19% 10%	2413
	11th to 20th	Night	68% 1 11% 13% 7% 1	2570
	21st to end	Night	67% 2 13% 14% 3 1	2660
December	1st to 10th	Night	66% 1 12% 17% 3	2660
	11th to 20th	Night	68% 2 10% 16% 5%	3281
	21st to end	Night	78% 1 4 14% 3	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	22% 20% 34% 19% 4 1	270
	11th to 20th	Day	26% 14% 41% 14% 4 1	270
	21st to end	Day	23% 16% 43% 15% 3	297
February	1st to 10th	Day	25% 24% 36% 11% 2 1	270
	11th to 20th	Day	23% 30% 33% 12% 1	270
	21st to end	Day	26% 31% 36% 7% 1	225
March	1st to 10th	Day	22% 23% 40% 14% 1	270
	11th to 20th	Day	24% 21% 35% 16% 3 1	270
	21st to end	Day	31% 16% 30% 15% 7% 2	506
April	1st to 10th	Day	30% 13% 34% 17% 4 1	460
	11th to 20th	Day	33% 16% 28% 17% 5% 1	452
	21st to end	Day	31% 17% 26% 18% 6% 2	460
May	1st to 10th	Day	28% 17% 32% 15% 6% 2	620
	11th to 20th	Day	26% 16% 33% 17% 6% 2	675
	21st to end	Day	23% 13% 34% 19% 8% 3	734
June	1st to 10th	Day	20% 15% 33% 21% 8% 3	680
	11th to 20th	Day	21% 10% 39% 20% 8% 2	680
	21st to end	Day	20% 13% 30% 23% 10% 3	680
July	1st to 10th	Day	11% 10% 36% 26% 12% 5%	671
	11th to 20th	Day	15% 13% 32% 25% 11% 5%	668
	21st to end	Day	11% 10% 35% 25% 14% 5%	739
August	1st to 10th	Day	16% 10% 30% 24% 16% 3	676
	11th to 20th	Day	18% 7% 23% 29% 17% 6%	581
	21st to end	Day	22% 12% 25% 21% 16% 4	539
September	1st to 10th	Day	20% 12% 27% 24% 14% 4	490
	11th to 20th	Day	17% 9% 34% 27% 11% 3	490
	21st to end	Day	26% 10% 29% 22% 10% 3	490
October	1st to 10th	Day	28% 14% 30% 17% 9% 2	357
	11th to 20th	Day	32% 20% 33% 14% 2	300
	21st to end	Day	35% 23% 33% 8% 2	330
November	1st to 10th	Day	29% 20% 32% 14% 4 1	270
	11th to 20th	Day	29% 24% 32% 10% 5%	270
	21st to end	Day	27% 21% 39% 8% 4 1	270
December	1st to 10th	Day	21% 19% 42% 11% 5% 1	270
	11th to 20th	Day	32% 23% 32% 10% 3	270
	21st to end	Day	28% 26% 33% 12% 1	297
January	1st to 10th	Night	21% 17% 39% 18% 4	950
	11th to 20th	Night	21% 17% 40% 15% 6% 1	950
	21st to end	Night	20% 14% 39% 21% 5% 1	1045
February	1st to 10th	Night	18% 17% 39% 18% 6% 1	950
	11th to 20th	Night	20% 21% 32% 20% 6%	843
	21st to end	Night	24% 19% 36% 18% 3	628
March	1st to 10th	Night	20% 15% 36% 22% 8%	760
	11th to 20th	Night	20% 18% 35% 22% 5%	712
	21st to end	Night	22% 11% 30% 28% 8% 1	627
April	1st to 10th	Night	24% 12% 35% 22% 6% 1	570
	11th to 20th	Night	28% 13% 29% 24% 6% 1	563
	21st to end	Night	23% 11% 31% 26% 8% 1	570
May	1st to 10th	Night	25% 9% 33% 25% 7% 1	570
	11th to 20th	Night	21% 8% 34% 27% 8% 1	561
	21st to end	Night	16% 8% 31% 33% 11%	617
June	1st to 10th	Night	19% 8% 27% 34% 11%	570
	11th to 20th	Night	18% 9% 31% 32% 10%	570
	21st to end	Night	19% 7% 27% 33% 13% 1	570
July	1st to 10th	Night	10% 5% 29% 38% 17% 1	555
	11th to 20th	Night	12% 5% 30% 33% 18% 1	552
	21st to end	Night	9% 5% 28% 38% 18% 2	624
August	1st to 10th	Night	13% 4 26% 37% 17% 2	567
	11th to 20th	Night	14% 4 20% 35% 24% 3	564
	21st to end	Night	18% 5% 28% 30% 17% 2	627
September	1st to 10th	Night	17% 6% 24% 33% 16% 4	570
	11th to 20th	Night	17% 7% 29% 31% 15% 1	631
	21st to end	Night	22% 10% 27% 29% 11% 1	760
October	1st to 10th	Night	24% 11% 29% 25% 11%	760
	11th to 20th	Night	28% 13% 29% 24% 6%	760
	21st to end	Night	32% 11% 29% 21% 6%	836
November	1st to 10th	Night	26% 14% 35% 20% 6% 1	743
	11th to 20th	Night	26% 18% 32% 19% 5%	860
	21st to end	Night	26% 18% 32% 20% 4	950
December	1st to 10th	Night	22% 20% 34% 18% 5% 1	950
	11th to 20th	Night	22% 17% 32% 21% 6% 1	950
	21st to end	Night	32% 18% 31% 16% 4	1045

Page generated at 2024-10-29 10:20:48. Version ac07

Copyright © 2024 Attilla Danko.