Using Your Ship-Observatory at Sea

  • Gregory I. Redfern
Part of the The Patrick Moore Practical Astronomy Series book series (PATRICKMOORE)


The moment has finally arrived. You have gone through the check in process on the pier and you are now about to get your first glimpse of the place you will be calling home and using as an observatory for the duration of your cruise. Once you go up the gangway, the stairs from the pier to the ship’s entryway, you will actually set foot on the ship herself. Ship security personnel will scan your keycard, and you will officially become part of the ship’s roster. From here on out you have to learn your way around the ship, and her deck plan is your guide.

Getting Familiar with Your Ship

The moment has finally arrived. You have gone through the check in process on the pier and you are now about to get your first glimpse of the place you will be calling home and using as an observatory for the duration of your cruise. Once you go up the gangway, the stairs from the pier to the ship’s entryway, you will actually set foot on the ship herself. Ship security personnel will scan your keycard, and you will officially become part of the ship’s roster. From here on out you have to learn your way around the ship, and her deck plan is your guide.

Ship Tip

Prior to leaving for the ship you should spend some time familiarizing yourself with the ship’s deck plan, which is available on the cruise line’s website. You might even consider downloading a copy of the deck plan to take with you, although most ships provide a pocket-size deck plan that fits in the (if) issued keycard holder. Every ship, even of the same class, is different. Please note that even if you were previously on a ship she may have undergone a modernization or an upgrade that changed her deck plan. Bottom line – learn the deck plan. You’ll be glad you did.

Your first shipboard task will be to find your stateroom using the deck plan. But first you have to determine if the staterooms are available for occupying. You have to realize that another whole set of guests left the ship the day you came aboard, and the stateroom attendants have to get the staterooms ready for the arrival of new guests, not a minor task. You can inquire with the ship’s security as you check in or at the reception desk. If the staterooms are not ready you can start familiarizing yourself with the ship – or maybe you will want to get something to eat and drink. When asking about your stateroom, you can inquire if the ship is serving food and where.

The deck plan will provide the layout of the ship for each deck that passengers have access to. You will learn the location of your stateroom, the dining room(s), spa, fitness center, pool(s), medical bay, library, reception, shore excursions office, theater, casino – all of the facilities and locations that make cruising great. The ship’s deck plan on the website or your printed out copy gives you an overhead view of each deck, with a side view of the vertical layout of the decks.

On board ship, usually by the elevators, each deck of your ship will have a side view deck layout with an outline of the ship that shows your location and all of the decks. The facilities located on each deck will be listed as well as stateroom numbers . The deck plan will also provide a listing of the various facilities and what deck they are on. Your location where you are viewing the deck plan will be indicated by a red dot “You Are Here” – sort of an X marks the spot. To get to where you want to go you find out what deck it is on and take the elevator or stairs to the required deck. Once on the specific deck you can consult the deck plan and find out if you need to go forward (towards the bow or front of the ship) or aft (towards the stern or back of the ship) to get to your destination.

Your issued key card may or may not have your stateroom number on it for security reasons, but your ship’s boarding pass will. All staterooms are numbered. The first number is the deck it is located on. Depending on the size of your ship there may be one or two numbers. The next number(s) will be part of the stateroom sequencing for the deck while the very last number of your stateroom will be even or odd. Even indicates your stateroom is on the port or left side of the ship as you face forward. Odd means that your stateroom is on the starboard or right side of the ship as you face forward. Once you get to your stateroom you can unpack and relax.

When you are ready to explore your ship-observatory you should do so in daylight, as it is easier and safer.

Safety Tips

When you are walking around the ship there are a couple of safety tips you must always remember.

First and foremost you never want to have both of your hands holding something, as you want to be able to always grab a hand rail, open a door or steady yourself. Your ship at sea is always in motion and subject to sudden movements. If your hands are full and you need to grab something you have a choice to drop what you are carrying or drop yourself by possibly falling.

Second, the deck can become very slippery because of rain, snow, ice or a wash down, which is usually done in the early morning. It is very easy to slip and slide, which makes the above tip come in very handy.

Third, when going up and down ladders on the weather decks (decks exposed to the elements) they can act as a wind funnel that accelerates the wind that is present, and this literally pushes you up or down them. This is especially true in the upper decks. Be careful and hold the handrails when using the ladder ways .

Four, some ships have raised steps at passageways/doors which require you to step up and through; this also probably applies to your stateroom bathroom. If you forget to step up at these areas, you will gain a very painful reminder to do so next time.

Fifth, there can be low overheads and angled structures for you to bump your head on. Take it slow and when need be low, as you get to know your ship, and be mindful of these tips as you explore the ship.

The Main Deck

Generally there is a main deck that may or may not go completely around the ship. Some ship classes do not allow guest access to the bow, while others do. On bigger ships they usually have a helipad and lots of room. You will need to inquire with the front desk if the bow area is open at night. If it is you are in luck, because this will be the darkest place on the ship. The reason? The bridge, where the ship is controlled and manned 24 hours a day at sea, will be above and behind the bow, and there will be no lights in the bow area. It has to be completely dark at night so the watch officers can see anything in front of and to the forward sides of the ship. The bow area will also have no structural obstructions overhead, again to insure that the bridge watch officers have an unimpeded view for safe navigation of the ship both day and night.

Ship Tip

Windstar Cruises’ fleet of luxury yachts , including two tall mast sail equipped vessels, have the most open deck plan of any ship the author has sailed on to date. Their vessels allow access to the forward part of the ship, including the bridge deck, at night. The stern is also accessible at night. Their vessels are in the 10,000-ton range and are close to the water. You can really get in touch with the sea and sky standing at the very bow of their ships as they are underway. It is exhilarating and makes for great observing and astrophotography.

While you are on the bow, or if you cannot access it and are on the main deck, check out whether this deck goes all the way around the ship. Most ships, especially the mid- to larger-sized ships, will have the main deck go completely around the ship. This can be used as a walking track so it can have a number of people on it. The ship’s lifeboats may be on this deck as well or stowed above it. This deck is probably the closest deck you will have to the sea itself and will offer views on the port, starboard and stern of the ship. There will be a deck overhead, so this is not where you want to be to take astrophotographs with large sweeping views looking up. It is however the best place to take pictures of the waves and overall sea surface with the horizon in your picture.

The next place you want to check out is the highest deck on the ship. The top deck usually will be accessible via ladderways on the port and starboard sides of the ship and is where the ship’s mast, some superstructure and a lounge area is located. Some ships have shuffleboard, sunbathing lounges and a variety of recreational activities in this area. The ship may have angled glass panels or open deck railing. There is deck lighting that is usually mounted low, next to the railing, so as to not to interfere with the wide view that is almost 360 degrees. This can be a very good area to take astrophotographs, as there will be limited if any overhead obstructions, and the ship’s lighted mast with her radar devices rotating can make for some interesting compositional photographs with the background sky.

While you are on the top deck, check the next deck below it to see if it goes around most of the ship. This is sometimes known as the fitness track and often has another lounge area. This deck can afford a very good view of the sky and horizon on the starboard and port sides of the ship. You can work your way back aft or all the way forward to get sky and horizon views. Some of the ships have this deck go all the way to the stern, which gives you a higher view of the sea, the horizon and the sky than if you are on the main deck back aft at the stern.

Astrophoto Tip*

The main deck is an excellent location to take sunrise and sunset pictures that will give the closest possible view of the waves and horizon . The higher up you are on a ship, the farther the horizon is away from you; this is called height of eye. You can see this for yourself by taking a daytime picture of the horizon on the main deck and then from the top deck. I recommend doing this so you can compare the two views and use them as a reference when you are planning an observing/astrophotography session.

While you are on the main deck take photographs of the bow and stern if you have access to them to round out your field of view references. If you want a picture where the sea surface, waves and horizon are a major component in your composition this is where you want to take your picture. When stars, a planet or the Moon are close to the horizon in either a rising or setting situation this can be part of your picture as well.

Now that you have checked topside during the day it is time to do so at night. You need to do this when the ship has turned on her topside lights, which occurs at sunset. There will be multiple sources of light that come from the ship’s lighted mast, deck lights that can be high or low, bright LEDs that illuminate bars and social gathering areas and perhaps “Full Dress Ship” lights that are strung overhead from the bow to the stern. Yes, a cruise ship can be a very brightly lit place to do astronomy and astrophotography. This is why you have to do a second deck plan check at night, where you repeat your steps from the day.

The good news is that there are shadow zones or even dark zones that you can usually find. The only problem is that these zones may not line up with what you want to photograph or observe at a particular time – more on that when you learn how to plan your observing/photography session a little later in this chapter. By walking around the ship at night you can find out where there are these shadow/dark zones just by noting areas where there is less or no light present.

Another proven light avoidance or mitigation tactic is that when you are on the starboard or port side on each of the weather decks you can point your camera out towards the sea and sky by being right up against the deck railing with your tripod. You can also shield the lens of your camera from light with its lens hood if it has one, and using your hand, body or a coat to block light that might be coming in to the field of view of your camera. Taking an exposure with your camera and seeing the results will tell you if you are successful in eliminating light or not. If necessary make adjustments and take another exposure. Keep making adjustments until you have achieved the best results you can.

If you are doing visual astronomy , instead of blocking light to a camera lens, you are doing so for your eyes. Here are two nifty tricks to try. It may be as simple as holding up your arm horizontally to your eyes so that light is blocked. The second is to use a jacket or sweatshirt with a hood. You pull the hood forward on your head until the hood is past your eyes and acts like an eye shade – this REALLY works! The reason it works is because the sea and sky themselves are not light polluted – unless you are in close proximity to a large city. Even then it will be some distance away unless you are pulling into or out of port.

Sometimes late at night some areas of the ship will actually turn lights off, usually in the stern, where many ships have an outdoor restaurant that shuts down. You make your way through the restaurant towards the stern and presto – the area has no lights out by the stern. Some of your best at-sea astropics can be gotten this way.

Remember that bow or stern access if you have it and it is open at night? You have hit astronomy/astrophotography pay dirt if you have it due to no lights and a great field of view.

You have now mapped out your ship’s deck plan as to what is accessible, the view different locations afford and determined your dark and shadow zones. It is now time to learn how to integrate this knowledge with what you want to observe/photograph in the sky.

Your Stateroom’s TV Information Channel

You are on a ship at sea that must navigate her way from port to port while avoiding bad weather and other possible instances that require a course change. Most ships will provide a chart, either paper and/or electronic, that shows the projected voyage of the ship for your cruise. This chart will have a line drawn from your port of departure to each of the ports you are scheduled to visit. The ship’s voyage chart is usually located in the main reception area. If you don’t notice one, inquire as to if the ship has one. If it doesn’t you still have 24-hour access to the “ship’s navigation channel,” which is on your stateroom’s TV.

Your stateroom will have a TV channel guide, and there is almost always a “ship’s navigation” or “bridge information channel.” It usually provides a camera view of what the bridge is seeing and possibly a stern view also, which can be useful to get an idea as to actual weather topside if you do not have a window in your stateroom. Even if you have a stateroom window the bridge camera gives you a view of what is ahead. Sometimes the picture is not that great due to a dirty lens or poor quality video. The night time view isn’t very good, but usually the light of the Moon can be seen on the sea.

This channel should give you:

  • The ship’s current latitude and longitude, which defines her position

  • Sunrise and sunset times for current position

  • Her course and speed

  • A map projection as to where the ship is, showing her track (a line that indicates where the ship has traveled and is headed)

  • The ship’s current date and time (maybe even time expressed as Coordinated Universal Time or Universal Time Coordinated (UTC)

  • Current weather, which includes:

  • Sea state

  • Wind speed – true speed and direction, relative speed and direction

  • Cloud cover

  • Precipitation

  • Humidity

  • UV index

  • Day’s temperature high and low with several days’ forecast

  • Nautical miles traveled since last port and overall distance covered with distance to next port with estimated date and time of arrival

We’ll now discuss how these pieces of information are vital to planning your observing and astrophotography sessions onboard ship.

To correctly use the astronomical software, star charts or planisphere you brought along you need to know how to use them. Make sure you have the instruction manual for your particular system that you are going to use. Hopefully you have become familiar ashore with the operation of the system you will use at sea in order to maximize your precious time at sea. If not use the daytime hours to get familiar with your particular system, as you do not want to be wasting time under the stars figuring everything out.

To use any system you have to know your location. In Chap.  4, “Location, Location, Location,” you’ll learn about how where you are literally in the world will affect what you see in the sky. But first we need to put the ship’s position information to work.

Depending on your ship’s IT capabilities and what you sign up for – it all comes with a cost (unless you have a special offer as part of your booking such as reduced price for or free Internet) – you may be able to use the “Current Location” feature on your software. This feature uses Global Positioning Satellites (GPS) to update your location. Quite frankly this has never worked for this author at sea on my smartphone or computer . Even with Wi-Fi enabled and connected to the Internet I get an error message when I try. It may work for you. Also note that most ships provide their Internet on a “one device only” basis, so you have to manage which device you are using when you try this feature if you have your software on all of your devices. If you can’t get a location update automatically you’ll just have to do it the old-fashioned way, by entering your longitude and latitude manually. Make sure you input the proper hemisphere – E/W or N/S when doing so.

This should be a simple process of accessing the ship’s information channel and inputting the ship’s position into your software in the “Latitude and Longitude” input boxes. You do not have to input beyond degrees and minutes of latitude and longitude (which may be all the ship’s information channel provides), as your requirements for accuracy at sea are not that stringent. You are not operating a telescope or looking for split second timing of an astronomical event. Even satellite timings will be accurate enough for naked-eye observation.

The real issue becomes time and what time zone you are in. When you input ‘location” into your astronomical software, besides using “Current Location,” “Latitude-Longitude,” you can also pick a country and then a city chosen from a list that is part of the software or maybe you will click on a map. The cities and the map should automatically input the time zone for you. But when you input the latitude and longitude manually you will probably have to input the time zone. Some ship information channels will have the UTC available, some will not.

If your ship does not provide UTC you will have to determine it yourself by looking up on the Internet a conversion website and input ship’s time to UTC, which will result in a “–” or “+” or 0 value. It is really important to input the right value, as if the wrong time is inputted even though you have the right location it will result in an error-filled sky on your software. If you do not have Internet you can ask at the Reception desk if they can find out for you what the UTC is. In the ship’s library there may be a world atlas that gives you the time zones of the world so you can try to work it out by knowing the ship’s location and seeing where the resulting time zone is.

One other complication is that the ship may play fast and loose with time zones. One ship changes time zones at 2 p.m. instead of 2 a.m. for guest convenience, and there are times when time zones get a bit stretched. This can make it difficult to exactly know what time zone you are really operating in. The only times when this becomes crucial is when you are preparing for solar and lunar eclipse events and satellite viewing opportunities. These events need an accurate time in order to be viewed at the proper time. Being off on your time zone will make you off in these events, so much so that you may miss portions of the eclipse or the viewing of a satellite. Again, if you want to confirm your true time zone for accuracy try the reception desk for help.

Planispheres are a bit easier to use as they generally have clear star field overlays that go by latitude N or S in some value of degrees, e.g., 20 degrees N, 40 degrees N, etc. Inputting the date and time gives you an approximation of the sky. Planispheres are very limited in the number of stars they present, mainly just the major constellation outlines with some stars identified and no information on planets. You have to know what constellation these are in, which means another source of information you need to refer to. They also are small by necessity, which can make them hard to read at night under red light. They do not provide any data on the stars. They are not a good choice for taking to sea.

Star chart books can be bought that detail the sky usually by the month and for a certain latitude range. Information about the stars, constellations, planets and eclipses are usually included. They are somewhat useful but are more bulk to carry and may not be the best thing to use when you are at sea, especially if you are going through multiple hemispheres.

Once you have checked out the ship to see where the observing/astrophotography shadow/dark zones are, and inputted your position and time into your software or your planisphere or star charts, you will have a view of what is in the sky overhead for your ship-observatory. You need a few more pieces of information from the ship’s information channel, though, before you head out to observe or photograph the sky.

Sunrise and sunset times are on the ship’s information channel and are listed in the ship’s daily bulletin, which contains the day’s events aboard ship. This information is necessary for observing morning and evening phenomena such as sunrises, sunsets, Earth’s shadow, zodiacal light, Mercury and Venus; all of these are covered in later chapters.

Knowing the Weather

You will need to know the weather. What is the sea state? The wind? Cloud and precipitation forecasts? The sea state will tell you how high the waves are and possibly the distance between the waves, which affects the motion of the ship. Generally the higher the waves and the larger the swells (waves that travel large distances after forming) the more the ship will move up and down and roll from side to side. This won’t affect your unaided visual observation of the sky but could negate the use of binoculars if the motion is too pronounced. It can have a HUGE effect on photographing the night sky, as invariably you will need to take a time exposure which will capture the ship’s motion and make the stars and planets look like an electrocardiogram (EKG) or modern art piece. Tips on how to assess and minimize this motion are covered in Chap.  16.

If the weather is too extreme the captain will order that the weather decks be closed, resulting in the access points to the main deck or some of the top decks being closed. DO NOT ignore these and go topside when such barriers are in place. You can place yourself in real danger. This situation can arise from either rain, thunderstorms, ice, wind , sea state or a combination thereof. If you break the safety protocols and are caught it might not be a pleasant situation to be in.

Another very important weather factor is the wind, which is measured in knots, meters per second and/or miles per hour. The higher the wind speed the more you have to be careful and mindful of places on the ship where you might need to block the wind. The wind is affected by the ship’s course and speed. True wind is the true direction of the wind in degrees of azimuth with its inherent true speed, while relative wind adds the effect of the ship’s course and speed.

When you go up on deck, look at the top of the ship’s mast. There will be a “wind vane” (the ship’s anemometer) that shows the direction of the wind and a “propeller” that measures wind speed. This is a visual clue for you to use in planning your observing or astrophotography session. Even at night the ship’s anemometer should be visible, as cruise ship masts are illuminated unless the ship is in “pirate condition” (this is real along the coast of Somalia and surrounding areas), which may necessitate a darkened or altered light profile of the ship.

Your Ship’s Course

Your final factor in planning your astronomy/astrophotography session is the ship’s course. She will be headed on a course that will be measured in degrees, 0 to 359, with 0 degrees being North, 090 degrees East, 180 degrees South, and 270 degrees West. These are the four cardinal directions and also coincide with the same cardinal directions in your software, planisphere or star charts.

Astro Tip

You should have N, E, S, and W highlighted on your software settings so they appear on the virtual horizon that is in your sky view. Your settings will also allow you to mark the point directly overhead in the sky at 90 degrees above the horizon known as the zenith. You should also turn on the meridian setting, which will have a line from N to S highlighted in your sky view. This helps in orienting you as to N and S. When astronomical objects transit the meridian they have reached their highest point in the sky for the day or night.

Your software should have the ability to click on the object you want to observe to highlight it and then click on a tab marked “Data/Description.” The data section will give you all kinds of physical data on your object of interest to include its azimuth (0 to 359 degrees) and altitude (0 to 90 degrees) above the horizon. If you have inputted the date and time you want to observe this object you will have its position to look for it in real time. The description will give you useful background information on the object as to its history, folklore and contributions to astronomy. There might even be a picture of it.

If you are looking to view the constellations it is a big help to have their outlines active on your settings menu, as this will help orient you. To get the position of a constellation (some are quite large in the sky) in altitude and azimuth just click on a star located within the boundary of the constellation, preferably a bright one (your software will show stars of varying levels of brightness and different colors so the constellation will be an accurate representation of what you will see in the sky). Use this information, along with the bright star, to go topside to find the constellation.

Another huge benefit for your sky sessions using your software (if it is loaded onto your smartphone or tablet) is the “Gyroscope” or “Compass” feature. This allows the real time sky view in your smartphone/tablet to “follow” your movements as you move your smartphone/tablet. If there is an object you want to find you can use the sky view in your smartphone/tablet to locate it, select the COMPASS or GYROSCOPE view, and then move the smartphone/tablet to align with your object. Note, you should have your software in “NIGHT VISION” mode, which shows the view in red light to preserve your night vision.

The ship will probably remain on one course for the duration of your session, even if you are up all night. Only when the ship is in proximity to entering or leaving port or having to maneuver to avoid ship traffic or weather will she change course. Otherwise she transits on a steady course that changes over days – especially in ocean crossings. The ship’s course will determine where on the ship you will have to go to see your astronomical object of interest.

This is where your previous exploration of your ship’s deck plan comes into play. You know the layout of the ship, so once you know the ship’s course the bow , stern, port and starboard sides will all be aligned with a certain section of the sky. You will need to align the direction of the object(s) you want to view/photograph with the location of the ship, which gives you access to that section of the sky. You will have multiple options for viewing/photographing the sky, and this is where your determination of dark and shadow zones proves its worth. Odds are that one of your options will have less light than the others; failing that, remember to bring your hooded jacket to block out light.

If what you want to see is located in the eastern part of the sky and the ship is heading in an easterly direction you could use these options:

  • Go to the bow

  • On the highest accessible deck move to the forward part of the port or starboard side, and look forward.

Each of these locations would give you a wide view of the sky.

If your object is in the southern part of the sky and the ship is heading in an easterly direction:

  • Go to the bow and face to starboard (south)

  • On the highest accessible deck face the starboard side (south)

  • On the main deck, starboard side, face directly south.

  • Go to the stern and face to starboard (south).

If what you want to see is located in the western part of the sky and the ship is heading in an easterly direction you could use these options:

  • On the highest accessible deck move to the aft part of the port or starboard side, and look aft.

  • Go to the stern.

Each of these locations would give you a wide view of the sky.

If your object is in the northern part of the sky and the ship is heading in an easterly direction:

  • Go to the bow and face to port (north).

  • On the highest accessible deck face the port side (north).

  • On the main deck, port side, face directly north.

  • Go to the stern and face to port (north).

Now that you have seen some examples here are the recommended steps to go through to align your astronomical object with the course of the ship for your upcoming session.

  1. 1.

    Use your software, planisphere or star chart to select what you want to observe/photograph.

  2. 2.

    Note the azimuth and altitude of your object. Some software will allow you to make an observing list for a session, which is very convenient.

  3. 3.

    Turn on the ship’s information channel and note the ship’s course. It is very helpful to see the ship’s course depicted on the map projection view, because the orientation of the ship’s direction shows it relative to the cardinal directions on the map view. N is top, S is bottom, E is right and W is left. This visual orientation helps in aligning to the sky.

  4. 4.

    For the first few times you do this get a piece of paper and label the cardinal directions on it. Next draw the figure of a ship (large enough so you can read it) in the same orientation of the ship’s course shown on the TV and label the bow, stern, port and starboard. Now you have a reference you can use to help orient you as to where to go on the ship to see your object.


After you have plotted out a few observing sessions you will be able to look at the ship’s position on the TV and align it with your planned observing/astrophotography session. If not, no big deal, as you can just continue to plot it out. In our next chapter we will build upon this skill you have developed, as your cruise(s) may take you to the other hemispheres of the planet, introducing new opportunities for observing and astrophotography.

Copyright information

© Springer Nature Switzerland AG 2018

Authors and Affiliations

  • Gregory I. Redfern
    • 1
  1. 1.NASA JPL Solar System AmbassadorRuckersvilleUSA

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