What would people say be an average speed in which to travel with ship in the Aegean sea.
Some people in my campaign wants to go from the Island of Samos to Constantinople by shi and it is about 333 miles.
City and Guild suggests dividing the direct distance with 60 to get the traveltime in days when sailing.
So about 6 days?
Travel speed by sailing ship is highly variable, depending mostly on weather.
City and Guild suggests about 60 land miles/day, or an average of roughly 2knots(nautical miles/hour), yielding 5 and a half days in your case (333/60). This is a reasonable estimate if you account for days of poor weather (no wind, storms etc.), the need to stop and reprovision, the fact that you may not want to travel in a straight line, or avoid dangerous waters at night etc. In practice, a small sailing ship determined to make good progress can easily travel at twice or thrice that speed with favourable winds; or even four or more times that speed if carried by very strong winds or a storm.
So, in your case, it's up to the Storyguide. Three days could easily suffice if weather is favourable (or if a little Auram/Aquam spontaneous magic is available). With really bad weather, it's reasonable that the trip could take a week or more.
In the aegean, really bad weather isn't nearly as likely as in the north sea or the atlantic though.
This is true, particularly in summer. In winter, however, (November-April) you can have some really bad storms.
Plus, "bad" weather could also mean no wind, or wind blowing against you. The Meltemi, blowing from the north, is a typical wind you'll have to tack against if sailing to Constantinople from the Aegean. So, again -- it's really up to the Storyguide, but the trip is highly unlikely to take less than two days or more than ten. 2 days + (stress die) half-days seems a reasonable guideline, with 1 to 5 botch dice depending on season, war/piracy, sailing crew abilities etc.
It's a 15th level spell/effect to create a wind in the desired direction. If there's enough time and someone with enough Auram knowledge the spell could be invented and then the ship always has favorable winds.
Base 2, R: Touch +1, D: Sun (+2), T:Ind, +2 Unnatural Effect (creating winds at ground level, this is kind of subjective as to whether it is a +1 or +2)
Also keep in mind that ships did not sail at night until the renaissance- at least not by choice. Now a magical ship which doesn't have questionable charts, navigational instruments, or range of vision might be another matter...
That might be true in some cases, certainly when close to land it is probably a good idea to wait until you can clearly see where you are going.
But the apparent use of star-based, naval navigation makes me think that night time sailing must have also been a thing (for at least some of the more organised nations/groups).
Indeed. Just think of the Norse discoveries in the North Atlantic of the late tenth century. The ships of the mediterranean maritime republics also regularly travelled at night latest from the tenth century on.
Cheers
The Norse also had less distance between land which they needed to sail, and stellar based navigation really came into it's own with the use of the compass and astrolabe in conjunction with wound clocks. 1295 is the earliest date of the first mariner's astrolabe, though land based astrolabes (difficult to use on a rocking ship, but maybe in really calm waters...) was dated to 150 BC, the compass was first invented in China in the first century AD, 1182 is the first recorded use of a compass in the western hemisphere. The earliest spring driven clock was in 1430. The combination of elements wasn't brought together until the 15th century. Certainly sailing by night wasn't impossible, but it was risky, rarely done, and done for comparatively short distances. Of course once you are out of sight of land (the horizon being roughly 5 miles away) you are in risky sailing situations anyways until you find land. Of course having lanterns lit on a ship is another hazard as it introduces the possibility of fire.
Now a properly prepared group with some intelligo terram and creo ignem spells could sail in safety comparable to the modern day...
The right combination of spells allows one to see straight to land, through the ocean, or even the earth, no matter the distance. They would be able to flat out see the New World from France. (Or whatever the Storyguide places to the West.) Along with any hazards the ocean may hold. Other spells can make the darkness a non-issue. Auram spells or Rego spells can make propulsion a non-issue as well. Safety probably exceeds that of modern sea travel with the right spells.
None of these devices are actually needed for travel out of sight of the coast. You can read it up e. g. with Jean de Joinville (an old, but free English translation is here: sagadb.org/eiriks_saga_rauda.en ), how ships and fleets traveled the open sea for several days until they reached another coast, when pilots tried to identify the location in sight as good as possible, for the leaders to make up their mind what to do.
Well, Norway to Iceland is some 800 km (or two times 400 km with the Faroer in the middle), a travel regularly undertaken back and forth from 930 AC on.
Cheers
Only if you don't count the islands in between. I can plot a course on google earth that never exceeds 250 miles land to land. A replica longship sailed by a non-Viking (and prsumedly less skilled at sailing longships) was able to cover 223 miles in one day. Additionaly there are many aspects of Viking navigation that have been lost to time including a "sun stone" which is postulated to have used polarizing effects to act as a form of astrolabe, which would make Viking navigational technology more advanced than Europe's.
Also at some times of year in that region "a day" in terms of sunlight could last for months.
And 250 miles are quite precisely 400 km - so there we agree. I already told you, that this worked out just with the Faroe. Of course, a captain couldn't rely on always finding them.
Under ideal conditions. For all we know, the Norse often enough were weeks at sea between Norway and Iceland: the sagas claiming months might exaggerate the normal duration, though.
This is not a specific problem about the Norse. Reading up the feats of navigation of the Italian seamen (e. g. as described by Jean de Joinville, interested in his king and not the skills of some troublesome navigators), we find what little detail we know about their means.
It is a general issue with medieval engineering and applied science: there is a nearly complete disconnect of those with specialized practical know how (far traders, pilots, bronze casters, architects and such) and chroniclers. Hence a lot of technical know-how and knowledge handed down in families we cannot trace. There are very few exceptions, like the Theophilus Presbyter (en.wikipedia.org/wiki/Tabula_Rogeriana). These rather show what we miss.
Cheers
And of course as anyone watching The Deadliest catch can realize, "dangerous" and "routinely done" are not necessarily mutually exclusive.
The dangers of long sea voyages - and indeed all long voyages - were very present to all medieval people.
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The danger profile also changes a bit when you take into account the galley use by the maritime republics. No lee shores.
There are also issues of wind reliability and ability to tack, which were highly variable between different ship designs. Also the height of the crows net, which could have a major impact on visibility (5 miles is a 6' man standing at surface level..). But in any case it wasn't something that would be done casually where an established route with experienced sailors had not been developed already.
Galleys were crammed high maintenance ships usually built for war, not sea voyages. But smaller and still more manoeuvrable fast rowed ships and boats were likely always an important component of medieval transport fleets in the mediterranean, very useful for landing (cf. Joinville disembarking at Damiette), screening and for scouting under coast. These make also good means for fast transport of very important persons and goods.
I reckon that 'it' shall denote travel on the open sea. At times that was done also out of necessity, when hugging the coast became just too dangerous because of the weather. But certainly never casually.
Cheers
Actually, the records from Southampton which discuss the arrival of the Venetian trade fleet say specifically that they were galleys. "Sensible" to us wasn't sensible to them.