I currently calculate it as 29629.
Max for a Litheor Explorer using only repeatable items is 24691
Max for a Litheor non-Explorer using only repeatable items is 19089.

Unlike the Wiki, this does NOT include the Autonomous Processor buff, as it is currently NOT active. If this changes, I'll update.
To fully max out scan, you must be a Litheor, to get the full bonus from The Litheoria. Otherwise you'll lose 150 scan.
If you are an Explorer, the bonus from the Datastream Compilers will double - this has been factored in.
These numbers include all known modules with complete upgrades, which is probably is not currently possible.

Here's the individual items that comprise max unbuffed scan

AI Supercomputer 5
Bainar, Systems Hacker 179
Base Scan Power 1
Carjean Data Node 150
Co-Align Signal Processor 80
Co-Align Signal Processor 80
Co-Align Signal Processor 80
Co-Align Signal Processor 80
Composite Ray - Type S 40
Composite Ray - Type S 40
Composite Ray - Type S 40
Composite Ray - Type S 40
Continuum Analyzer 960
Continuum Analyzer 960
Continuum Analyzer 960
Continuum Analyzer 960
Continuum Analyzer 960
Continuum Parser 80
Continuum Parser 80
Continuum Parser 80
Continuum Parser 80
Cybernetic Remote Link 120
Datastream Compiler 30
Datastream Compiler 30
Datastream Compiler 30
Datastream Compiler 30
Decryption Senary-Frame 45
Decryption Senary-Frame 45
Decryption Senary-Frame 45
Decryption Senary-Frame 45
Exo-Temporal Translator 25
Exo-Temporal Translator 25
Exo-Temporal Translator 25
Exo-Temporal Translator 25
Flux Ringdisc 30
Genetarr Transmitter - Mark II 55
Genetarr Transmitter - Mark II 55
Genetarr Transmitter - Mark II 55
Genetarr Transmitter - Mark II 55
Gravidynamic Isolator 40
Gravidynamic Isolator 40
Gravidynamic Isolator 40
Gravidynamic Isolator 40
Gravimetric Flume 90
Gravimetric Flume 90
Gravimetric Flume 90
Lepus Revealer 60
Lepus Revealer 60
Litheor Data Interface 20
Litheor Data Interface 20
Litheor Data Interface 20
Litheor Tetractic Crystal 40
Litheor Tetractic Crystal 40
Litheor Tetractic Crystal 40
Litheor Tetractic Crystal 40
Merged Datanode 240
Mission Archives 140
Omni-Field Regulator 80
Omni-Field Regulator 80
Omni-Field Regulator 80
Q-Pedd Emotion Simulator 45
Q-Pedd Emotion Simulator 45
Prejor Beacon Sensor 40
Prejor Beacon Sensor 40
Scruuge Charged Hypernode 70
Scruuge Charged Hypernode 70
Sehrin, Bioship Ally 149
Sha'din Hypergrid Core 55
Sha'din Hypergrid Core 55
Sha'din Hypergrid Core 55
Sha'din Hypergrid Core 55
Strazi Oculix 180
Stryll Locator Eye 125
Stryll Locator Eye 125
Stryll Transponder 20
Stryll Transponder 20
T-Plasma Dynamo 60
T-Plasma Dynamo 60
T-Plasma Dynamo 60
T-Plasma Dynamo 60
Tachyon Router 25
Te'vul's Core 60
Te'vul's Core 60
Tel-Sheel Data Drone 180
Tetra-Seek Targeter 40
Tetra-Seek Targeter 40
Tetra-Seek Targeter 40
The Litheoria 225
TitanProxy 100 4%
TitanProxy 100 4%
TitanProxy 100 4%
Trovar Zane, Elite Tracer 179
Uldrinian Henxicant 200
Ulidrinian Onxicant 180
Voliir Modulator - Mark II 80
Voliir Modulator - Mark II 80
Voliir Modulator - Mark II 80
Zortah's Interface Jack v.2 113
Zortah's Interface Jack v.2 113
Zortah's Interface Jack v.2 113

What is the total deck space needed to install all of the above modules?

Great info, thanks!

Making this a Sticky.

With all possible percent buffs applied to the scan provided by the new Uldrinan module it adds roughly 475 more to the max.

Well, I purged some more planets, including some enemy planets and got my scan rating to "Fair": (Now 302 vacant and 107 enemy).

My scan has permanent titan proxy buff, and scan is now at 10088 without further buffs.
Scanning devices on my ship:
1 AI Supercomputer
5 Continuum Analyzers Mark III
4 Continuum Parsers
1 Cybernetic Link Interface
4 Datastream Complilers
3 Decryption Quad Frames
1 Decryption Senary Frame
4 Exo-Temporal Translators
1 Flux Ringdisc
3 Litheor Data Interface
4 Litheor Tetractic Crystals
1 Merged Datanode (500% upgrade)
3 Omni Field Regulators
2 Prejor Beacon Sensors
4 Sha'Din Hypergrid Cores
2 Stryll Prey Trackers
2 Stryll Transponders
1 Tachyon Router
2 Tevul's Core
3 Tetra Seek Targeters
3 Titan Proxys
1 Uldrinian Onxicant
3 Voilir Modulators Mark II
3 Zortah's Interface Jacks v.2

I've completed all the standard missions. It looks like all can do is upgrade the rest of my Decryption Quad frames to Senary. and install gravimetric flumes (if I ever get enough artis to build those) Is there any other way to increase scan? Some of those modules are in poor condition, would fixing them increase my scan?

No, repairing modules will not increase your scanning power at all. However, aside from the senary frame upgrades there are about 25-30 scan modules and 3 allies you are missing still that would increase your scan (and the allies to be rank 100). Also upgrading modules like the cybernetic link will also help and I think you may have missed some of the standard missions chains; genetarr, taltherian and the ctp required missions as you haven't listed all the scan modules they provide. You can also switch to litheor explorer to get the best race/prof scan boost.
Good luck!

Do you guys recommend cloaking planets to the max of 27500 and completely invisible or to the 22961 and hope that someone using a Protogrid doesn't get lucky and scan it?

I'd say the max repeatable scan is what you should be worried about. Someone who is capable of hitting max scan with protogrids has likely allready used them hitting a previous max scan. up to you however

You have the Prejor Decrypted Data calculated in for the Max for a Litheor Explorer using only repeatable items is 22916. Should only be 22781, just did a scan run yesterday that was where I was at.

Is your Bainar maxed?

Yes

Bumping this because the Scruuge Hypercharged Node isn't included yet.

[edit]

Just realized that is possible to have the Henxicant fully upgraded now providing it's 2% scan bonus.
The following number should be just about right for max repeatable scan.

23475

Should probably add in the "Q-Pedd Emotion Simulator" x2 as well..

Updated today with all new holiday and mission items - numbers should be current.

What % buffs did you include? I got a different number for Litheor Explorers (a bit lower).

Well if he included on that list what the specific % bonuses are it'd be easier to see the differences.

There is the newest Icy LM one with the 2% scan boost but that'll be an iffy one as it depends on how often you get the mission at an opportune time for a completion.

Max scan it but make sure you have something else (attack,defense,pop, invasion def) to back the cloak up.

Should add Lepus Widecaster and remove Lepus Revealer.