Hopewell Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hopewell Observatory clear sky chart from 2005-11-05 to 2018-10-27.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
39%
16702
20%
51306
12%
16666
49%
16666
25%
32435

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
23%
776
22%
2586
8%
776
39%
776
21%
1610
January16th to endNight
21%
832
22%
2704
9%
832
38%
832
22%
1702
February1st to 15thNight
21%
761
18%
2482
5%
761
38%
761
21%
1546
February16th to endNight
17%
683
22%
2093
6%
683
37%
683
21%
1334
March1st to 15thNight
24%
780
23%
2145
9%
780
39%
780
26%
1381
March16th to endNight
23%
832
20%
2280
8%
832
33%
832
23%
1536
April1st to 15thNight
26%
778
19%
1946
5%
778
35%
778
28%
1296
April16th to endNight
41%
771
19%
1927
7%
771
46%
771
29%
1306
May1st to 15thNight
41%
601
16%
1771
10%
601
46%
601
24%
1191
May16th to endNight
51%
420
16%
1639
15%
420
56%
420
22%
1000
June1st to 15thNight
56%
390
19%
1560
19%
390
63%
390
24%
908
June16th to endNight
63%
390
17%
1560
20%
390
69%
390
26%
893
July1st to 15thNight
60%
395
14%
1505
16%
395
63%
395
22%
920
July16th to endNight
74%
612
16%
1739
13%
579
77%
579
35%
1037
August1st to 15thNight
66%
575
18%
1715
14%
572
68%
572
28%
1116
August16th to endNight
66%
801
18%
2043
12%
801
67%
801
33%
1363
September1st to 15thNight
56%
780
23%
1950
14%
780
59%
780
31%
1330
September16th to endNight
54%
777
21%
2152
18%
777
56%
777
27%
1450
October1st to 15thNight
48%
780
22%
2340
20%
780
55%
780
27%
1480
October16th to endNight
38%
816
29%
2447
18%
816
53%
816
32%
1441
November1st to 15thNight
38%
760
25%
2382
15%
760
51%
760
28%
1428
November16th to endNight
33%
780
23%
2698
13%
780
49%
780
25%
1564
December1st to 15thNight
28%
780
18%
2730
7%
780
42%
780
18%
1764
December16th to endNight
25%
832
20%
2912
9%
832
41%
832
20%
1839

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 ForecastData
Points
Cloud CoverDay
14%5%245%3445%7%41%
52230
Night
14%5%2442445%7%43%
51491
Cloud CoverDay
14%5%245%2445%7%41%
52240
Night
14%5%2442445%7%43%
51495
TransparencyDay
40%6%12%22%15%2
51933
Night
39%6%12%22%16%3
51306
SeeingDay
17%8%23%24%17%8%
7090
Night
17%8%28%30%14%1
16710

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
16%5%244245%5%6%41%
1679
16th to endDay
15%6%35%5%23437%42%
1872
February1st to 15thDay
16%6%25%5%245%6%5%38%
1710
16th to endDay
15%7%345%3434441%
1663
March1st to 15thDay
15%5%245%34335%45%
2134
16th to endDay
16%6%35%5%34446%39%
2294
April1st to 15thDay
13%5%35%5%24446%44%
2332
16th to endDay
18%42442444443%
2308
May1st to 15thDay
17%5%24435%45%7%38%
2519
16th to endDay
17%5%244345%6%8%38%
2827
June1st to 15thDay
12%324425%6%6%9%42%
2730
16th to endDay
8%425%5%35%6%7%10%42%
2730
July1st to 15thDay
10%425%6%35%5%6%9%40%
2700
16th to endDay
8%4146%36%6%9%11%36%
2673
August1st to 15thDay
11%425%6%46%5%7%9%34%
2487
16th to endDay
11%3245%35%6%7%8%41%
2496
September1st to 15thDay
15%4245%33447%43%
2340
16th to endDay
17%5%24423446%42%
2133
October1st to 15thDay
20%414423346%43%
1950
16th to endDay
14%41342335%5%50%
2034
November1st to 15thDay
14%5%235%23346%46%
1803
16th to endDay
16%4233235%46%46%
1592
December1st to 15thDay
16%5%15%5%25%446%42%
1560
16th to endDay
17%6%16%424447%38%
1664
January1st to 15thNight
16%5%25%424446%43%
2586
16th to endNight
16%6%2442345%5%43%
2704
February1st to 15thNight
13%6%245%245%46%43%
2480
16th to endNight
14%7%25%414346%43%
2093
March1st to 15thNight
15%5%133245%47%45%
2133
16th to endNight
16%6%245%24446%40%
2280
April1st to 15thNight
13%6%2442445%6%43%
1946
16th to endNight
15%5%243245%5%8%43%
1927
May1st to 15thNight
17%5%244245%5%8%38%
1771
16th to endNight
15%5%1443446%9%41%
1637
June1st to 15thNight
10%424425%6%6%7%45%
1560
16th to endNight
9%325%426%5%6%9%44%
1560
July1st to 15thNight
9%426%435%5%5%10%42%
1587
16th to endNight
6%3135%26%5%8%12%43%
1847
August1st to 15thNight
8%5%15%6%36%5%7%7%41%
1726
16th to endNight
9%4244346%7%9%41%
2043
September1st to 15thNight
14%5%245%35%45%5%44%
1950
16th to endNight
15%6%25%5%34345%43%
2152
October1st to 15thNight
19%5%14323435%45%
2340
16th to endNight
14%323323345%53%
2447
November1st to 15thNight
13%6%2432244450%
2382
16th to endNight
15%31332445%7%47%
2698
December1st to 15thNight
16%6%26%5%25%446%39%
2730
16th to endNight
16%5%2442445%7%40%
2912

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
16%425%325%45%6%41%
1679
16th to endDay
14%7%35%5%24337%42%
1872
February1st to 15thDay
15%7%25%5%35%46%6%38%
1710
16th to endDay
16%7%245%3445%5%40%
1663
March1st to 15thDay
14%5%25%5%24436%45%
2145
16th to endDay
16%6%26%5%34446%39%
2293
April1st to 15thDay
13%5%25%5%24445%44%
2332
16th to endDay
18%5%245%24445%43%
2308
May1st to 15thDay
17%5%24435%45%7%38%
2519
16th to endDay
17%5%244345%6%8%37%
2827
June1st to 15thDay
12%3244246%7%9%42%
2730
16th to endDay
8%325%5%25%5%7%10%41%
2730
July1st to 15thDay
9%425%6%35%6%6%9%40%
2700
16th to endDay
8%4245%46%6%8%12%36%
2673
August1st to 15thDay
10%6%25%6%46%5%7%9%34%
2487
16th to endDay
11%4145%25%6%7%8%42%
2496
September1st to 15thDay
15%4245%24447%44%
2340
16th to endDay
17%6%15%5%2345%5%42%
2133
October1st to 15thDay
20%414423336%44%
1950
16th to endDay
14%414423346%50%
2034
November1st to 15thDay
14%5%24414345%47%
1803
16th to endDay
16%423324446%47%
1592
December1st to 15thDay
16%5%25%42435%6%42%
1560
16th to endDay
18%6%25%424446%39%
1664
January1st to 15thNight
16%5%25%423447%43%
2586
16th to endNight
16%7%24324446%42%
2704
February1st to 15thNight
14%5%25%5%25%45%5%43%
2473
16th to endNight
14%7%26%424346%43%
2093
March1st to 15thNight
15%5%22324448%44%
2145
16th to endNight
15%6%25%5%24446%41%
2280
April1st to 15thNight
13%5%245%3445%7%43%
1946
16th to endNight
15%42442445%7%43%
1927
May1st to 15thNight
17%5%25%4245%5%8%38%
1770
16th to endNight
15%5%15%42445%9%40%
1637
June1st to 15thNight
10%324335%5%6%8%45%
1560
16th to endNight
8%235%335%5%6%9%44%
1560
July1st to 15thNight
9%5%26%435%6%410%42%
1587
16th to endNight
6%314436%5%8%12%43%
1847
August1st to 15thNight
8%5%25%5%45%6%6%8%41%
1726
16th to endNight
9%435%4345%6%10%40%
2043
September1st to 15thNight
13%6%245%3446%5%43%
1950
16th to endNight
15%5%25%5%34445%42%
2152
October1st to 15thNight
19%5%14323345%45%
2340
16th to endNight
14%313323345%52%
2447
November1st to 15thNight
13%5%34413335%50%
2382
16th to endNight
15%41332445%6%47%
2698
December1st to 15thNight
16%5%26%5%25%445%40%
2730
16th to endNight
16%5%245%2445%6%40%
2912

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
42%5%13%20%15%4
1680
16th to endDay
43%311%23%14%3
1872
February1st to 15thDay
44%5%11%22%13%3
1712
16th to endDay
44%412%23%14%1
1663
March1st to 15thDay
41%410%22%16%3
2145
16th to endDay
45%5%11%17%17%3
2294
April1st to 15thDay
39%411%21%18%3
2332
16th to endDay
41%5%9%18%18%6%
2308
May1st to 15thDay
43%7%14%18%14%1
2519
16th to endDay
41%8%13%23%10%1
2831
June1st to 15thDay
36%9%15%24%13%1
2730
16th to endDay
34%10%15%21%15%1
2730
July1st to 15thDay
37%10%13%20%16%2
2553
16th to endDay
34%10%15%23%13%1
2518
August1st to 15thDay
41%9%15%19%13%
2474
16th to endDay
35%9%14%24%13%2
2496
September1st to 15thDay
38%7%12%18%19%3
2340
16th to endDay
42%6%8%23%17%1
2133
October1st to 15thDay
41%411%24%14%3
1950
16th to endDay
34%49%27%22%2
2034
November1st to 15thDay
37%412%21%17%5%
1803
16th to endDay
37%5%10%26%17%2
1592
December1st to 15thDay
41%5%13%23%12%3
1560
16th to endDay
45%5%11%24%11%1
1664
January1st to 15thNight
41%411%19%17%5%
2586
16th to endNight
41%411%23%17%1
2704
February1st to 15thNight
40%5%13%22%15%2
2482
16th to endNight
41%410%24%16%2
2093
March1st to 15thNight
37%6%12%26%14%2
2145
16th to endNight
43%5%11%20%17%2
2280
April1st to 15thNight
39%5%10%21%19%2
1946
16th to endNight
39%7%10%20%15%7%
1927
May1st to 15thNight
42%7%12%20%13%3
1771
16th to endNight
39%7%16%20%14%2
1639
June1st to 15thNight
34%9%14%24%16%1
1560
16th to endNight
34%7%15%21%19%2
1560
July1st to 15thNight
37%10%15%18%14%4
1505
16th to endNight
29%9%19%23%16%1
1739
August1st to 15thNight
37%8%13%21%16%1
1715
16th to endNight
35%8%14%22%15%2
2043
September1st to 15thNight
39%7%11%20%18%3
1950
16th to endNight
42%5%8%21%18%3
2152
October1st to 15thNight
40%412%22%17%3
2340
16th to endNight
33%48%28%21%3
2447
November1st to 15thNight
37%38%22%19%7%
2382
16th to endNight
35%410%24%20%4
2698
December1st to 15thNight
45%5%10%21%14%2
2730
16th to endNight
42%6%14%22%12%1
2912

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
22%22%36%15%
119
16th to endDay
18%27%32%18%3
144
February1st to 15thDay
23%25%40%8%
135
16th to endDay
24%15%36%21%2
244
March1st to 15thDay
18%20%32%24%4
330
16th to endDay
18%15%34%23%5%2
352
April1st to 15thDay
16%18%27%24%10%1
330
16th to endDay
23%7%28%17%19%3
319
May1st to 15thDay
22%10%27%19%13%5%
348
16th to endDay
23%320%22%21%9%
395
June1st to 15thDay
13%423%24%22%10%
375
16th to endDay
9%123%33%22%8%
375
July1st to 15thDay
11%116%30%25%12%
365
16th to endDay
11%11%32%31%12%
390
August1st to 15thDay
16%13%24%30%14%
358
16th to endDay
10%18%30%27%20%
396
September1st to 15thDay
19%415%21%18%21%
375
16th to endDay
24%215%23%21%11%
374
October1st to 15thDay
22%416%24%22%8%
375
16th to endDay
14%10%31%23%15%4
382
November1st to 15thDay
16%9%25%28%16%3
301
16th to endDay
16%14%33%23%9%2
122
December1st to 15thDay
13%20%34%18%10%3
90
16th to endDay
26%16%35%18%3
96
January1st to 15thNight
20%15%36%22%4
780
16th to endNight
20%13%40%23%2
832
February1st to 15thNight
18%12%42%24%2
764
16th to endNight
20%18%38%19%2
683
March1st to 15thNight
20%13%38%24%2
780
16th to endNight
18%12%40%22%5%
832
April1st to 15thNight
16%14%39%24%4
778
16th to endNight
18%7%28%33%11%1
771
May1st to 15thNight
21%425%33%14%
601
16th to endNight
17%319%38%20%1
421
June1st to 15thNight
8%222%41%24%1
390
16th to endNight
8%217%50%19%1
390
July1st to 15thNight
11%118%36%29%3
395
16th to endNight
8%10%40%34%5%
612
August1st to 15thNight
11%12%43%29%3
575
16th to endNight
10%19%41%31%4
801
September1st to 15thNight
16%117%29%30%4
780
16th to endNight
17%117%31%28%2
777
October1st to 15thNight
21%319%29%21%3
780
16th to endNight
15%10%32%27%13%
816
November1st to 15thNight
16%8%31%29%12%1
760
16th to endNight
17%13%31%27%9%
780
December1st to 15thNight
19%9%36%25%8%
780
16th to endNight
20%10%38%28%1
832
Page generated at 2018-10-28 08:41:01. Version ac04

Copyright 2018 A. Danko


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