You know when you've transitioned from Noob to Serious player when you ......

[Random Tank]

Simply, when you can most aspects of the game without struggling... You don't have to be a docking master, or do Eve returns with a 20 ton ship; just when you can dock, gain orbit, land on an average planet, do an interplanetary transfer, aerobrake, circularise or make a SSTO (not all, just most) without struggling, because you know the game, then you can call yourself a serious player.

[Caelib]

... when you have memorized the delta-V requirements and Kerbin-relative planetary intercept phase angles for all other planets.

[Pecan]

Remember guys, I meant serious not expert

When, given a mission one step beyond your comfort zone you can nevertheless decide on your mission-stage strategy intelligently, look-up the deltaV requirements for each of those, competently design and build suitable vehicles to meet them according to the design optimisation criteria you prefer (mass, cost, part-count, potential for mayhem) AND know the difference, find the appropriate transfer parameters, launch and fly the mission. With whatever mods you prefer; it's up to you. "Serious" is capable of doing the things you enjoy without 'just' doing the things you already know ;-0

[Taki117]

Simply, when you can most aspects of the game without struggling... You don't have to be a docking master, or do Eve returns with a 20 ton ship; just when you can dock, gain orbit, land on an average planet, do an interplanetary transfer, aerobrake, circularise or make a SSTO (not all, just most) without struggling, because you know the game, then you can call yourself a serious player.

I can't agree more! If you are proficient enough to do these things without too much trouble, and understand what's going on when you do them, you are a serious player.

[SkyRender]

Remember guys, I meant serious not expert

They're kind of related, really. It's hard to be serious about something you're not any good at doing, and it's hard not to be serious about something you've gotten really good at.

[Overfloater]

Transition? I was never a noob to begin with.

I bought this game right after I watched a video by Scott Manley, and thanks to him I never was a noob either. B-)

Before that I didn't realize what this game is really about, and rejected it so many times...

Then I was like "holy crap! there's orbital mechanics! docking ships! interplanetary travel!...

[sumrex]

When you can use your intuition in flight and design rather than guessing. As far as F5 F9 goes. I didn't know they were in in the game for several months so after a lot of maddening crashes I can almost fly a ship blindfolded now.

[Masetto]

I felt "pro" when I started to be able to make rather accurate Hohmann transfers to most celestial bodies without needing to use maneuver modes, because the angles of the transfer-windows have just become recognizable.

[moeggz]

Funnily enough, I felt like a "serious" KSP player when my knowledge or real world space exploration started to grow. Like, yeah, when you start successfully doing interplanetary manned missions you are a "serious" player. But when you start learning about all currently operating space missions, agencies, and companies just for fun then you are truly a "serious" player. Because now it is no longer just a game, now it is a tutor to your interest in space exploration, much more than just a game.

[Rus-Evo]

When a glitch prevents you from making a node to fine tune your planetary encounter, so you eyeball the Nav ball to do it!

[problemecium]

...when you no longer ever feel a need to use the Fine Controls.

...when you discover a problem with a plugin and fix it yourself.

[Benaiah]

I came in here expecting to laugh knowingly at the posts and feel good about how far I've come in 600 hours of play.

But then again I did just forget to put chutes on that one rocket and had to do a powered landing with all the extra fuel that I should not have brought.

You all make me feel like a noob again.

[Vanamonde]

... when you stop comparing yourself to the skill levels of other people and just enjoy playing the game.

[FacialJack]

when u cant no more make love wiz ure wife until she's green skined....

[User Unrelated]

Or rather when you don't need any help at all. You position the part perfectly with your eyes.

graphical reference points graphical reference points graphical reference points

I felt like I made the transition after I learned what all the nodes on the navball did (enhanced navball, I have 6 markers now) haha

before that, they were just random symbols to me.

[MockKnizzle]

I feel like you're a serious player when you start planning your missions out on paper instead of just relying on trial and error.

[Rithsom]

When you can build a 20-ton rocket that can make it to Duna and back

[SkyRex94]

when you need less than 800 m/s to return from Vall polar low Orbit to Kerbin. Just done that. Setting up the node for this really feels like Serious Player

[Kamuchi]

When you mess around and return from the Mun without paying attention, doing an aerobreaking around Kerbin and endup lined up with ksc both inclination and deorbit point!

Or simply have all the luck in the universe and that it got recorded for future generations...

[Gravaar]

When you are amazed that your rocket exploded instead of being amazed that it made orbit

Edited July 31, 2014 by Gravaar
Typo

[LABHOUSE]

When you can dock spacecraft and get to the same orbit as another ship/object.

[syfyguy64]

You can eye ball a trip to Eve and back.

[LethalDose]

I think you're good at the game when docking "ain't no thang" for you any more.

I think you're a "serious player" When you feel comfortable running simple interplanetary missions with a dV budget similar to what's shown

I think you're a "professional" when you pull off the fabled Eve surface return mission.

[Shisouka]

When one can wake you up in the middle of the night and ask how much dV is needed for a <insert interplanetary body here> mission ..

And you excel at KSP when you take a look at KSP date/time in the overview and start thinking: "Jool launch window in 3 KSP days, better start assembling that mothership in LKO!"

[Idrryl]

When 95% of your rockets can go to the Mun.

Or when you test your landers o the Mun that are meant for other planets and whatnot.