[MrB (Simon)]

F
FIR.......Far Infra-Red
FITS......Flexible Image Transport System (Image data)
FL........Focal Length
FOV.......Field Of View
FR........Focal Reducer
FSQ.......? (Takahashi Brand)
FWIW......For What It's Worth

G
GEM.......German Equatorial Mount
GMT.......Greenwich Mean Time
GPS.......Global Positioning System
GRB.......Gamma Ray Burst
GRS.......Great Red Spot (Jupiter)
GSO.......Guan Sheng Optical (Brand)

H
Ha........Hydrogen-Alpha
HDR.......High Dynamic Range (Photography)
HPS.......High-Pressure Sodium(street lights)
HST.......Hubble Space Telescope

I
IAU.......International Astronomical Union
IC........Index Catalogue
ICNR..... In Camera Noise Reduction
IIS.......Ice In Space (You Are Here!)
IMO.......In My opinion
IR........Infra-Red
ISO.......International Standards Organisation (Camera sensitivity/Film speed)
ISS.......International Space Station

J
JMI.......Jim's Mobile Inc. (Brand)
JPEG......Joint Photographic Experts Group
JPL.......Jet Propulsion Laboratory (NASA)

L
L.........Luminance
LASER.....Light Amplification by Stimulated Emission of Radiation
LINEAR....LIncoln Near-Earth Asteroid Research (Satellite)
LM........Lunar Module
LMC.......Large Magellanic Cloud
LP........Light Pollution
LPI.......Lunar Planetary Imager (Meade brand)
LPR.......Light Polution Reduction (Filter)
LPS.......Low-Pressure Sodium(street lights)
LRGB......Luminance, Red, Green, Blue (Filters)
LRO.......Lunar Reconnaissance Orbiter (satellite)
LUM.......Luminance

M
MAPUG.....Meade Advanced Products Users Group
MN........Mak-Newt
MPCC......Multi-Purpose Coma Corrector
MRO.......Mars Reconnaissance Orbiter (satellite)

N
NASA......National Aeronautics and Space Administration
NB........Narrow Band
NEAF......NorthEast Astronomy Forum (Astro convention)
NEAT......Near-Earth Asteroid Tracking (Satellite)
NEB.......North Equatorial Belt
NEWT......NEWTonian (Telescope)
NG........North Group (Brand)
NGC.......New General Catalogue
NGT.......Next Generation Telescope (JMI brand)
NOAA......National Oceanic and Atmospheric Administration
NR........Noise Reduction

O
OAG.......Off-Axis Guider
OIII......Oxygen-3 (Filter)
OP........Original Poster (Forums)
OPT.......Ocean Photo & Telescope (US Retailer)
OS........Operating System .... or....
OS........OverSeas
OSC.......One-Shot Colour (Camera)
OSD.......On Screen Display
OTA.......Optical Tube Assembly

P
PC........Personal Computer
PE........Periodic Error
PEC.......Periodic Error Correction
PHD.......Push Here Dummy (Guiding Software)
PM........Private Message
PME.......Paramount ME (Brand)
PN........Planetary Nebula
POTN......Photography On The Net (Website)
PS........PhotoShop (software)
PS........Post Script (eg: PS: blah blah blah)
PST.......Personal Solar Telescope (Coronado brand)

Q
QHY.......? Camera (Brand)
QSI.......Quantum Scientific Imaging inc.(Brand)

R
RA........Right Ascension .. or ..
RA........Radio Astronomy
RC........Ritchey-Chrétien (Telescope)
RCOS......Ritchey-Chrétien Optical Systems (Brand)
RFT.......Rich(est) Field Telescope
RGB.......Red, Green, Blue (Filters)
RMS.......Root Mean Squared
ROR.......Roll-Off-Roof (Observatory)