Robert Allerton Park is a botanical garden in Piatt County, Illinois. It sits roughly 7.3 km (4.5 mi) WSW of Monticello. It is listed on the National Register of Historic Places.
The Robert Allerton Park is a 1,517-acre (614 ha) park, nature center, and conference center located in the rural Piatt County township of Willow Branch, (T 18 N, R 5 E) near Monticello, Illinois, on the upper Sangamon River. The park and manor house, The Farms, are attributed to owner Robert Allerton, industrialist heir, artist, art collector and garden designer. Robert donated the complex to the University of Illinois in 1946. The National Park Service registered the Robert Allerton Estate as a National Historic Place on July 18, 2007. The Allerton Natural Area within the park was designated a National Natural Landmark in 1970. As of 2007, the park was used by approximately 100,000 visitors per year. It has been described as "a vast prairie turned into a personal fantasy land of neoclassical statues, Far Eastern art, and huge European-style gardens surrounding a Georgian-Revival mansion".From the Wikipedia article “Robert Allerton Park”, licensed under CC BY-SA 4.0.
Sunrise & sunset directions
At Robert Allerton Park the sunrise point swings a long way through the year: about 58° (ENE) at the June solstice and 121° (ESE) in late December. Sunset moves from 302° (WNW) in June to 240° (WSW) in December, and the midday sun climbs to 73° in summer but only 27° in winter.
| Date | Sunrise | Azimuth | Sunset | Azimuth | Noon sun | Daylight |
|---|---|---|---|---|---|---|
| March equinox (Mar 20) | 6:59 AM | 90° E | 7:07 PM | 271° W | 50° | 12h 08m |
| June solstice (Jun 21) | 5:27 AM | 58° ENE | 8:28 PM | 302° WNW | 73° | 15h 01m |
| September equinox (Sep 22) | 6:43 AM | 89° E | 6:53 PM | 271° W | 50° | 12h 11m |
| December solstice (Dec 21) | 7:14 AM | 121° ESE | 4:33 PM | 240° WSW | 27° | 9h 19m |
Azimuth is measured clockwise from true north (90° = east, 270° = west). Computed for 2026; values change by less than a degree from year to year.
Golden hour & blue hour by month
Gardens are best on bright overcast days or early mornings when dew is fresh and the wind is calm.
| Month (15th) | Blue hour starts | Sunrise | Golden hour ends | Golden hour starts | Sunset | Blue hour ends | Daylight |
|---|---|---|---|---|---|---|---|
| January | 6:46 AM | 7:15 AM | 7:57 AM | 4:12 PM | 4:54 PM | 5:24 PM | 9h 39m |
| February | 6:21 AM | 6:49 AM | 7:26 AM | 4:53 PM | 5:31 PM | 5:59 PM | 10h 42m |
| March | 6:40 AM | 7:07 AM | 7:43 AM | 6:26 PM | 7:02 PM | 7:29 PM | 11h 55m |
| April | 5:49 AM | 6:17 AM | 6:54 AM | 6:57 PM | 7:33 PM | 8:01 PM | 13h 16m |
| May | 5:10 AM | 5:40 AM | 6:19 AM | 7:25 PM | 8:03 PM | 8:34 PM | 14h 23m |
| June | 4:53 AM | 5:26 AM | 6:07 AM | 7:45 PM | 8:26 PM | 8:59 PM | 15h 00m |
| July | 5:07 AM | 5:39 AM | 6:19 AM | 7:44 PM | 8:23 PM | 8:55 PM | 14h 44m |
| August | 5:38 AM | 6:07 AM | 6:44 AM | 7:16 PM | 7:53 PM | 8:22 PM | 13h 46m |
| September | 6:09 AM | 6:36 AM | 7:12 AM | 6:29 PM | 7:05 PM | 7:32 PM | 12h 29m |
| October | 6:38 AM | 7:06 AM | 7:42 AM | 5:40 PM | 6:16 PM | 6:44 PM | 11h 11m |
| November | 6:12 AM | 6:41 AM | 7:21 AM | 4:00 PM | 4:40 PM | 5:09 PM | 9h 59m |
| December | 6:40 AM | 7:10 AM | 7:53 AM | 3:48 PM | 4:31 PM | 5:02 PM | 9h 21m |
Local time (America/Chicago), including daylight saving time. Golden hour runs from about −4° to +6° solar altitude, so the morning golden hour begins during blue hour, before sunrise.
Milky Way & night sky
From Robert Allerton Park, the Milky Way core is visible in a dark sky from March through September. June gives the longest window (about 4.8 hours on a moonless night), and the core peaks around 21° above the southern horizon. Our light-pollution model puts the sky at about Bortle 4 (rural / suburban transition), good enough for detailed Milky Way images.
| Month | Core visible (15th) | Hours | Max altitude | Direction |
|---|---|---|---|---|
| January | Below 10° in darkness | — | -3° | — |
| February | 5:02 AM – 5:12 AM | 0.2 | 11° | SE → SE |
| March | 4:12 AM – 5:32 AM | 1.3 | 18° | SE → SSE |
| April | 2:10 AM – 4:30 AM | 2.3 | 21° | SE → S |
| May | 12:14 AM – 3:44 AM | 3.5 | 21° | SE → S |
| June | 10:29 PM – 3:19 AM | 4.8 | 21° | SE → SSW |
| July | 10:21 PM – 1:51 AM | 3.5 | 21° | S → SW |
| August | 9:35 PM – 11:55 PM | 2.3 | 21° | S → SW |
| September | 8:38 PM – 9:48 PM | 1.2 | 18° | SSW → SW |
| October | 7:47 PM – 7:57 PM | 0.2 | 11° | SW → SW |
| November | Below 10° in darkness | — | 0° | — |
| December | Below 10° in darkness | — | -19° | — |
Window when the galactic core is at least 10° high during astronomical darkness on the 15th of each month. Pick nights within a few days of the new moon. Plan exact nights with the Milky Way planner.
Estimated sky darkness: 4 Bortle 4 — Rural / suburban transition. Light domes are visible in several directions; the Milky Way is clear but lacks detail near the horizon. Modeled zenith brightness ≈ 21.15 mag/arcsec². Aurora needs roughly Kp 7.0+ to show low on the northern horizon here.
Weather & best season
Long-term NASA satellite data for this area show September as the clearest month (about 43% average cloud cover) and December as the cloudiest (69%). July is the warmest month and January the coldest, which matters for gear, snow access and how long batteries last at night.
Average cloud cover (%)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| High °F | 67 | 70 | 79 | 84 | 91 | 105 | 108 | 104 | 100 | 91 | 79 | 70 |
| Low °F | -15 | -12 | 2 | 20 | 30 | 38 | 49 | 49 | 37 | 24 | 8 | -4 |
| Precip. (in) | 2.5 | 2.6 | 3.0 | 4.5 | 4.7 | 4.9 | 3.9 | 3.2 | 3.0 | 3.8 | 3.2 | 2.9 |
Monthly climatology for the surrounding 1° grid cell from NASA POWER (MERRA-2). Mountain sites can be colder and cloudier than the cell average.
Photography tips for this botanical garden
- Many gardens restrict tripods or charge for photography; check the rules before you go.
- Backlit petals glow; position yourself so the sun is behind the flower.
- Seasonal exhibits (orchids, tulips, cherry blossoms) draw crowds — arrive at opening.
- Kaleidoscopic and abstract images are great for flower close-ups — try the online kaleidoscope tool.
- Tell someone where you're going in remote areas and carry the ten essentials.
Season: Spring bulbs and blossoms, summer perennials and autumn color; glasshouses offer winter subjects.
Suggested gear: Macro lens, Diffuser, Small reflector. Work out exposures with the depth of field, ND filter and NPF rule calculators.
FAQ
When is the best time to photograph Robert Allerton Park?
What time is golden hour at Robert Allerton Park?
Where does the sun rise and set at Robert Allerton Park?
Can you see the Milky Way from Robert Allerton Park?
Do you need a permit to photograph at Robert Allerton Park?
How far is Robert Allerton Park from Monticello?
Sources
Location data: Wikidata, Wikipedia. Sun, moon and Milky Way times are computed by LWPhoto Atlas for 2026. Climate: NASA POWER. Sky darkness is a population-based estimate (Walker's law), not a measurement. See data sources & licenses.