Sky Planner – FOV Astro

Sky Planner

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This planner is built around a practical question: what deep-sky targets can I image from my real sky opening at this specific time? Enter your location, define one or more visible azimuth windows, and the planner filters the catalog to show only targets that fit those limits.

Location & Date: Latitude and longitude define the sky for your observing site. The selected date and time define the current observing moment, and the slider advances in 15-minute steps. Min altitude is a hard “usable now” floor. Use My Location can fill latitude and longitude from the browser when permission is granted.

Visible Sky Windows: Each window is an allowed azimuth sector. The default 0°–360° behaves as an all-sky window. Example: 270°–360° means west through north only. Add more than one window if your usable sky is split by trees, roofs, or buildings.

Target Types & Filters: Use the object type checkboxes to keep only the classes you want. Max mag removes faint targets and reduces clutter. Max targets on chart limits how many currently visible objects are drawn. Min best altitude rejects objects whose best height during the selected date is still too low to be worthwhile. Show object names controls whether planner labels are drawn on the charts.

Time controls: Now jumps to the current local time. In Sky Map mode, changing time recenters the all-sky view on the current local meridian so the map moves in a useful way with time, although Aladin Lite is still a celestial sky atlas rather than a full local-horizon planetarium. The time slider works within the currently selected day. Astro Darkness is time-dependent: when enabled, the planner only keeps targets that meet the filters during astronomical darkness, and if the selected time is not dark it jumps to a dark slot on that date. Night Mode changes planner text and controls to red for darker-adaptation-friendly viewing.

Views: Alt-Az shows the local sky in altitude/azimuth coordinates for the selected time and location. Sky Map uses Aladin Lite for the live sky background. You can zoom with the mouse wheel, with the planner + and − buttons, or with Aladin’s own zoom controls, and pan by dragging. The planner overlays its own filtered target markers and altitude guide lines on top of the survey background.

FOV Calculator: The FOV Calculator button opens a dedicated equipment panel where you can pick telescope, camera and reducer / barlow / flattener, adjust the FOV Rotator, set seeing, and view a compact metrics table plus sampling indicator. The resulting FOV frame is drawn on the Sky Map. The HUD toggle shows or hides the information label above the FOV frame.

Target List: The list shows the filtered objects for the selected time with columns such as Mag, Alt / Az, Best Time, Best Alt, Size and Framing / Fit. Click any sortable column heading to sort the list; clicking the same heading again reverses the order. The default list order is by Mag.

Object Search: Use the search box above the target list to find catalog objects by common name or catalog designation, such as M 42, NGC 2024 or Horsehead. Matching an object behaves like selecting it from the target list.

Satellite Overlay: Turn on Satellite Overlay to check whether currently selected targets may be crossed by satellites. Select a target first from the target list, the chart, or object search. Max satellites limits how many candidate satellites are refined at once; the default is aligned with the Top 20 transit table for a quicker first pass. Update interval controls how often predictions refresh from already loaded satellite data. Look-ahead searches ahead from the selected time for possible crossings, and Track span controls how much of each path is drawn. Use the satellite type checkboxes to include Stations, Bright / Visual, or Starlink. In Sky Map, the overlay is useful for seeing where a path may cross your framing; for more detailed timing, switch to Alt-Az. Hover over a satellite marker or track in Sky Map to see the possible in-frame transit time range, duration, closest approach time, and object type.

Satellite categories: Stations focuses on the brightest crewed or large orbital platforms such as the ISS and similar station-class objects. This is the easiest group to test because there are only a few objects and their tracks are usually obvious. Bright / Visual adds other satellites that are more likely to be bright enough to matter visually or in wide-field imaging. It gives a broader but still practical view of likely satellite interference without loading the heaviest dataset. Starlink adds the Starlink constellation. This is the largest and most demanding group, useful when you want to check for modern constellation traffic, especially for longer imaging sessions. Starlink can take longer to load than the other categories and may produce many more possible paths than Stations or Bright / Visual. Satellite tooltips also show a simple object type label such as satellite, debris, rocket body, or unknown when it can be inferred.

Satellite matching precision: With an active camera setup, the planner now checks satellite crossings against the current FOV frame rather than only using a simple target-centre distance. The search uses a coarse pass and then refines around the nearest approach with smaller time steps, which improves narrow-field and long focal length results. The planner also estimates when a matched satellite enters and leaves the current frame so the hover tooltip can show a possible transit time range. Even so, very small fields can still miss some fast passes if the satellite only clips the frame briefly, so use longer Look-ahead values when testing.

Saved settings: The planner saves your latitude, longitude, and selected telescope, camera and optic in the local browser. When you open the page again on the same browser/device, those values are restored automatically.

Catalog: Deep-sky target data are based on the OpenNGC NGC / IC catalog and companion addendum used by the planner. The combined planner catalog contains more than 13,900 objects. In Sky Map mode, this planner catalog is the filtered target overlay; the survey background can still show many more stars and image details from the selected Aladin survey.

Location & Date

Date Latitude Min altitude (°) Longitude

Visible Sky Windows

Target Types

Filters

Max mag: 11.0 Max targets on chart: 10 Min best altitude: 20° Show object names

Time

Selected time: 00:00

Satellite Overlay

Select a target first, then enable the overlay to check possible satellite crossings near the selected time. Alt-Az is the best place to review the timing in more detail, while Sky Map lets you hover on a satellite marker or track to see the possible in-frame transit time range.

Max satellites: 20 Update interval: 15s Look-ahead: 180 min Track span: 5 min

Stations Bright / Visual Starlink

Satellite Names

Satellite overlay is off.

Top 20 transits

Satellite ID	Duration	Time range
Enable Satellite Overlay to list matching transits.

Target List At Selected Time

Target	Type	Mag	Alt / Az	Best Time	Best Alt	Size	Framing / Fit	Observation Time	Az Range