[Canada_Rockies]

Btw. the unit "ton" is actually a megagram, but that is also not used widely for traditional reason

I must be pedantic and disagree. A "ton" is 2,000 pounds. A "tonne" is 1,000 Kilograms.

For the metrically challenged, the metric tonne is 5 pounds and a bit more than a "Long ton", shipping weight of 2,200 pounds, or 20 "hundredweight", because for some odd English reason a hundredweight is 110 pounds. Don't let me get going on trying to figure out how many stone I weigh without a calculator. Hmmm, my calculator says I weigh 12 and a half stone - too many trips to the ice cream bucket again.

[Class A]

Here is a blend of Hydrogen Alpha (656 nm) and normal color.

Impressive!

I guess because it is so distant you don't need tracking device (as you probably would for moon or mars, etc.).

[MoiVous]

Nice diversion guys...but to get back to the OPs second question....

Think of your cameras sensor as a sheet of graph paper with 3008 points on the X axis and 2008 points on the Y axis.

Now overlay that graph grid onto the image you've just taken with your camera. When you shoot each of those grid squares is a sub part of the picture like a mosaic - thats a PIXEL.

The way the image is stored is determined by the sensor type - Pentax use the Bayer filter (you'll find lots of references to that around) but their is an alternative called the Foveon filter.

Regardless of the filter type, the raw, unmodified data can be stored in the RAW format and is effectively unaltered in the full grid size. But there is a downside to this - you have to process the RAW pixels in some way to display it. A bit like developing a film. So you have to convert the raw pixels into an image. If you store in JPEG on your camera your processing the raw data in the camera into a JPEG.

The processing of RAW files affects the quality of the final images (beyond the lens/camera effects), and some processing loses less information than other. The final storage form of the image after processing may be in a format that loses information or not. TIFF and Adobe PSD files for example have no loss, but many printing houses don't know what to do with them. You can also convert them to a JPEG.

JPEG takes that original image grid and mathematically alters it to reduce the amount of storage it occupies on your memory card (think of that as digital film). This compression algorithm still gives the same number of pixels as the RAW format, but it introduces losses that may introduce distortion between adjacent pixels.

Thats because to redisplay the image, the algorithm has to reconstruct the original image from what has been stored, and there is a loss of information in that reconstruction. Think of that as mixing or blurring of the original grid boxes so two or more boxes (pixels) will blend into one and distort the original. The amount of distortion is affected by the amount of compression. So a *** JPEG will have less distortion than a * JPEG on your camera.

Effectively your processing the raw data in the camera with a JPEG if you store in JPEG in the camera.

So to answer your followup question of how far can you blow it up (I think the megapixel debate is answered), shooting in RAW won't give you more pixels, but it will allow you to manipulate the image (develop it) on your computer with finer detail than a JPEG, and no loss of information.

However, you can't blow the image up infinitely and not see the pixels as they are of a finite size and will therefore appear as boxes (pixelation) the more you blow it up.

The two images below are from a TIFF at 400% zoom and 100% zoom (just to illustrate the pixelation) from about the same area of the image.

I hope that helps your understanding of the process.....

[procyon]

I must be pedantic and disagree. A "ton" is 2,000 pounds. A "tonne" is 1,000 Kilograms.

Interesting, I have never really thought about this particular clash of unit names in english. Is there a pronounciation difference also ? Or is "tonne" for writing and "metric ton(ne)" for speaking ?

[Livewireshock]

Interesting, I have never really thought about this particular clash of unit names in english. Is there a pronounciation difference also ? Or is "tonne" for writing and "metric ton(ne)" for speaking ?

Commonly speaking, they can be pronounced the same. Although it can sometimes referred to as 'tuns' and the others as 'tons' but that can go both ways depending on the speaker and how they were brought up.

I like the recent confusion in terms in the recent credit crisis and what exactly is a $1trillion. The fact that UK english billion is alot bigger number than the US english billion. The same for trillion etc....

US english billion = 1,000 million = 1,000,000,000

UK english billion = 1 million million = 1,000,000,000,000

US english trillion = 1,000 billion = 1,000,000,000,000

UK english trillion = 1 million million million = 1,000,000,000,000,000,000

All I know is that my bank balance shows just a single naught, oh wait should that be zero.

[LeoTaylor]

Impressive! I guess because it is so distant you don't need tracking device (as you probably would for moon or mars, etc.).

Thank you.

My two equatorial telescope mounts are motorized, they track the heavens. Within a few percent most all celestial objects move at the same speed: 15 degrees per hour at the equator or 1 revolution per day. For a given camera/lens combination it does not matter if one images the Moon or a galaxy several million light years away. One can "get away with" not tracking for wide angle frames of short duration.

[Class A]

Within a few percent most all celestial objects move at the same speed: 15 degrees per hour at the equator or 1 revolution per day.

Yes, of course, makes total sense.
Nice setup!

[Terje-L]

I think the simple answer to the OP's question is that RAW vs. JPG is about picture quality, while the size in Megapixels determines the maximum print size. The two are not related in any way.

In RAW you have no in-camera processing, but can do your own processing in Photoshop or other editor. Very similar to a negative in the film world.