Reisterstown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Reisterstown clear sky chart from 2005-11-05 to 2017-09-16.

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
33%
15173
20%
46862
9%
15132
45%
15132
23%
29513

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
18%
718
21%
2449
7%
716
36%
716
15%
1547
January16th to endNight
13%
768
23%
2496
5%
768
35%
768
18%
1551
February1st to 15thNight
15%
704
18%
2287
3%
701
33%
701
17%
1422
February16th to endNight
13%
631
23%
1910
3%
631
36%
631
17%
1223
March1st to 15thNight
21%
720
20%
2022
7%
720
35%
720
21%
1326
March16th to endNight
18%
768
20%
2076
6%
768
31%
768
22%
1381
April1st to 15thNight
20%
718
18%
1796
4%
718
29%
718
24%
1210
April16th to endNight
32%
720
18%
1800
5%
720
38%
720
28%
1207
May1st to 15thNight
33%
533
17%
1613
9%
533
40%
533
21%
1095
May16th to endNight
46%
374
17%
1497
13%
374
54%
374
20%
902
June1st to 15thNight
47%
360
19%
1440
17%
360
58%
360
24%
824
June16th to endNight
56%
360
17%
1440
17%
360
64%
360
25%
818
July1st to 15thNight
53%
340
12%
1360
12%
340
56%
340
18%
866
July16th to endNight
66%
509
16%
1540
13%
476
71%
476
34%
872
August1st to 15thNight
62%
539
18%
1609
13%
536
64%
536
31%
994
August16th to endNight
60%
761
20%
1907
12%
761
62%
761
34%
1243
September1st to 15thNight
53%
720
25%
1800
13%
720
58%
720
34%
1155
September16th to endNight
51%
658
23%
1807
18%
658
55%
658
29%
1186
October1st to 15thNight
41%
660
23%
1980
18%
660
50%
660
25%
1269
October16th to endNight
31%
704
27%
2112
13%
704
50%
704
29%
1231
November1st to 15thNight
32%
700
24%
2247
12%
700
48%
700
24%
1361
November16th to endNight
24%
720
21%
2466
10%
720
40%
720
19%
1485
December1st to 15thNight
20%
720
17%
2520
5%
720
35%
720
15%
1637
December16th to endNight
16%
768
20%
2688
5%
768
34%
768
16%
1708

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%40%
47871
Night
14%5%2442445%7%43%
47044
Cloud CoverDay
14%5%25%5%345%5%7%40%
47881
Night
14%5%2442445%7%43%
47048
TransparencyDay
41%6%12%22%15%2
47571
Night
39%5%12%23%16%2
46862
SeeingDay
17%13%27%23%14%4
5669
Night
17%14%30%25%11%1
15176

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
15%7%245%35%5%47%38%
1486
16th to endDay
13%7%35%5%33446%40%
1728
February1st to 15thDay
14%6%35%6%4445%6%38%
1575
16th to endDay
14%8%25%5%34337%40%
1561
March1st to 15thDay
15%7%34424337%42%
1924
16th to endDay
16%7%35%5%33445%39%
2148
April1st to 15thDay
14%5%345%2435%7%41%
2152
16th to endDay
17%5%25%42335%6%43%
2160
May1st to 15thDay
18%4345%3445%8%36%
2345
16th to endDay
15%5%246%3445%8%38%
2618
June1st to 15thDay
12%5%24436%46%10%38%
2520
16th to endDay
11%4245%3446%8%43%
2520
July1st to 15thDay
9%5%25%6%45%6%7%9%38%
2520
16th to endDay
7%335%5%46%7%7%10%36%
2519
August1st to 15thDay
11%4246%36%6%6%8%37%
2331
16th to endDay
11%4245%345%6%8%41%
2292
September1st to 15thDay
14%424424447%44%
2160
16th to endDay
16%7%245%34447%40%
1825
October1st to 15thDay
18%5%14423347%44%
1650
16th to endDay
15%5%2442345%5%46%
1760
November1st to 15thDay
14%6%2332445%6%45%
1610
16th to endDay
17%6%24424445%43%
1491
December1st to 15thDay
16%5%25%5%25%45%7%38%
1440
16th to endDay
17%6%25%5%2435%8%38%
1536
January1st to 15thNight
17%5%26%42445%7%39%
2449
16th to endNight
16%6%245%2345%6%43%
2496
February1st to 15thNight
14%6%25%423446%43%
2285
16th to endNight
13%6%26%5%33446%42%
1910
March1st to 15thNight
15%5%2433445%5%43%
2010
16th to endNight
14%6%25%6%24436%43%
2076
April1st to 15thNight
13%5%345%345%5%7%42%
1796
16th to endNight
16%5%2433236%7%43%
1800
May1st to 15thNight
19%7%24324446%39%
1613
16th to endNight
12%7%245%3445%7%42%
1495
June1st to 15thNight
11%325%425%5%5%8%45%
1440
16th to endNight
9%324435%5%5%11%42%
1440
July1st to 15thNight
9%5%26%6%37%6%7%8%36%
1440
16th to endNight
5%323426%5%6%12%46%
1647
August1st to 15thNight
9%5%25%42447%8%45%
1620
16th to endNight
11%5%244245%5%9%45%
1907
September1st to 15thNight
12%5%25%413448%47%
1800
16th to endNight
14%6%25%5%24346%44%
1807
October1st to 15thNight
18%5%23434345%44%
1980
16th to endNight
14%41232335%6%51%
2112
November1st to 15thNight
13%6%35%32333450%
2247
16th to endNight
16%5%2442445%7%42%
2466
December1st to 15thNight
17%5%25%5%35%5%46%37%
2520
16th to endNight
16%6%25%42445%7%40%
2688

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
15%6%34435%447%39%
1486
16th to endDay
14%7%35%5%245%45%41%
1728
February1st to 15thDay
13%7%35%5%3446%6%38%
1575
16th to endDay
13%7%25%5%34346%40%
1561
March1st to 15thDay
14%7%345%23437%42%
1935
16th to endDay
16%6%36%6%33446%39%
2147
April1st to 15thDay
14%5%25%5%3336%8%41%
2152
16th to endDay
17%5%24424445%43%
2160
May1st to 15thDay
17%5%25%435%46%8%36%
2345
16th to endDay
15%4346%3446%8%37%
2618
June1st to 15thDay
11%5%25%5%35%5%6%10%38%
2520
16th to endDay
10%42444446%8%43%
2520
July1st to 15thDay
9%425%6%36%6%7%8%39%
2520
16th to endDay
7%415%5%5%7%8%8%10%37%
2519
August1st to 15thDay
11%426%6%35%7%6%7%37%
2331
16th to endDay
11%4245%346%6%8%41%
2292
September1st to 15thDay
13%425%5%2445%7%43%
2160
16th to endDay
17%5%25%5%23448%40%
1825
October1st to 15thDay
17%5%14323447%44%
1650
16th to endDay
15%5%244235%45%46%
1760
November1st to 15thDay
14%5%2332345%6%46%
1610
16th to endDay
16%6%24423346%43%
1491
December1st to 15thDay
16%426%4345%5%7%39%
1440
16th to endDay
16%7%25%424348%38%
1536
January1st to 15thNight
17%5%25%42446%7%40%
2449
16th to endNight
16%6%2342445%6%42%
2496
February1st to 15thNight
14%6%245%2445%6%43%
2278
16th to endNight
13%6%35%5%24446%43%
1910
March1st to 15thNight
15%6%2443445%6%43%
2022
16th to endNight
14%6%25%5%24436%42%
2076
April1st to 15thNight
12%6%345%3445%7%42%
1796
16th to endNight
16%5%2442435%7%43%
1800
May1st to 15thNight
19%7%24324446%39%
1612
16th to endNight
12%6%245%34447%42%
1495
June1st to 15thNight
10%414425%5%6%9%44%
1440
16th to endNight
9%324345%5%6%12%42%
1440
July1st to 15thNight
9%5%26%6%47%6%6%9%35%
1440
16th to endNight
6%223426%5%6%13%46%
1647
August1st to 15thNight
9%5%25%4335%6%8%44%
1620
16th to endNight
11%425%4245%5%9%45%
1907
September1st to 15thNight
12%5%25%323448%47%
1800
16th to endNight
13%6%25%5%2435%6%43%
1807
October1st to 15thNight
19%5%2332335%5%44%
1980
16th to endNight
14%313312446%51%
2112
November1st to 15thNight
12%6%35%423335%50%
2247
16th to endNight
16%424425%5%5%6%43%
2466
December1st to 15thNight
17%5%25%5%25%45%5%38%
2520
16th to endNight
16%6%2442345%7%40%
2688

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
44%6%12%21%12%3
1487
16th to endDay
43%412%24%11%3
1728
February1st to 15thDay
43%5%11%25%11%2
1577
16th to endDay
43%412%24%11%2
1561
March1st to 15thDay
42%5%11%23%15%2
1935
16th to endDay
46%5%9%18%17%2
2148
April1st to 15thDay
41%5%10%21%17%3
2152
16th to endDay
41%48%18%20%5%
2160
May1st to 15thDay
45%6%12%20%14%1
2345
16th to endDay
43%7%13%21%12%1
2622
June1st to 15thDay
39%8%13%24%13%
2520
16th to endDay
36%8%14%21%17%1
2520
July1st to 15thDay
38%8%14%21%14%2
2371
16th to endDay
36%10%14%23%12%1
2363
August1st to 15thDay
41%8%12%20%16%1
2318
16th to endDay
37%7%12%24%15%2
2292
September1st to 15thDay
38%5%11%20%21%2
2160
16th to endDay
42%48%20%20%2
1825
October1st to 15thDay
39%5%11%23%17%2
1650
16th to endDay
39%410%26%18%
1760
November1st to 15thDay
38%5%12%21%17%5%
1610
16th to endDay
42%410%25%14%2
1491
December1st to 15thDay
42%6%14%23%10%2
1440
16th to endDay
45%5%12%22%13%
1536
January1st to 15thNight
43%412%20%15%3
2449
16th to endNight
40%411%27%14%1
2496
February1st to 15thNight
40%413%23%14%2
2287
16th to endNight
41%410%24%17%2
1910
March1st to 15thNight
40%5%12%26%13%1
2022
16th to endNight
42%412%21%16%2
2076
April1st to 15thNight
40%412%20%18%3
1796
16th to endNight
39%5%10%19%18%6%
1800
May1st to 15thNight
44%6%10%21%14%2
1613
16th to endNight
38%8%15%19%14%3
1497
June1st to 15thNight
34%8%12%27%16%
1440
16th to endNight
33%7%14%25%16%2
1440
July1st to 15thNight
43%8%14%17%11%4
1360
16th to endNight
27%9%18%25%17%2
1540
August1st to 15thNight
34%7%14%23%17%2
1609
16th to endNight
35%7%11%24%19%3
1907
September1st to 15thNight
35%5%11%21%22%3
1800
16th to endNight
40%48%19%22%3
1807
October1st to 15thNight
41%410%23%17%2
1980
16th to endNight
33%410%29%20%1
2112
November1st to 15thNight
37%47%23%19%6%
2247
16th to endNight
39%411%24%17%3
2466
December1st to 15thNight
45%5%11%23%12%1
2520
16th to endNight
42%5%14%22%12%1
2688

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
24%39%23%11%1
69
16th to endDay
23%34%28%13%
96
February1st to 15thDay
23%34%37%4
90
16th to endDay
17%30%38%12%
220
March1st to 15thDay
19%23%32%20%4
270
16th to endDay
19%19%38%16%32
288
April1st to 15thDay
19%18%33%18%8%1
270
16th to endDay
18%11%34%15%15%2
270
May1st to 15thDay
29%18%23%17%9%2
288
16th to endDay
19%6%24%26%19%3
331
June1st to 15thDay
13%10%28%25%18%3
315
16th to endDay
14%8%31%28%12%3
315
July1st to 15thDay
12%5%26%32%19%4
305
16th to endDay
7%420%33%26%7%
326
August1st to 15thDay
13%5%19%30%21%9%
313
16th to endDay
12%16%32%23%14%
332
September1st to 15thDay
14%9%19%22%22%10%
315
16th to endDay
22%317%29%15%11%
254
October1st to 15thDay
22%9%19%27%16%5%
255
16th to endDay
15%16%31%25%9%1
272
November1st to 15thDay
17%14%29%20%17%1
240
16th to endDay
22%19%32%16%9%
111
December1st to 15thDay
23%28%26%11%8%1
60
16th to endDay
25%20%39%12%3
64
January1st to 15thNight
21%22%32%20%2
720
16th to endNight
20%23%39%14%1
768
February1st to 15thNight
20%21%37%19%1
704
16th to endNight
19%26%36%15%1
631
March1st to 15thNight
20%20%35%20%3
720
16th to endNight
18%18%41%16%4
768
April1st to 15thNight
16%22%38%18%3
718
16th to endNight
18%15%30%25%9%1
720
May1st to 15thNight
22%9%30%26%9%
533
16th to endNight
17%7%22%33%17%1
375
June1st to 15thNight
11%232%32%20%
360
16th to endNight
10%222%46%16%
360
July1st to 15thNight
10%220%42%23%
340
16th to endNight
7%118%40%28%4
509
August1st to 15thNight
12%215%44%23%2
539
16th to endNight
13%216%36%26%4
761
September1st to 15thNight
13%420%32%26%2
720
16th to endNight
16%420%31%23%3
658
October1st to 15thNight
21%10%21%26%16%3
660
16th to endNight
17%15%32%24%9%
704
November1st to 15thNight
15%17%30%25%10%1
700
16th to endNight
18%20%30%20%7%
720
December1st to 15thNight
22%17%35%16%7%
720
16th to endNight
20%20%38%18%2
768
Page generated at 2017-09-16 17:07:01. Version ac04

Copyright 2017 A. Danko


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