Photography deep sky object

[Jingguo]

I would like to find out if it is true that some deep sky object would look nicer through photo then through the telescope? 2) What is false color? thanks alot

[weixing]

Hi,
Yes. Most deep sky object look nicer in photograph. This is because human eye cannot detect colour in dim objects. The colour of dim objects can only be detected on film or by CCD equipment. Also, colour is only detectable by the human eye in bright objects like stars and planets. For example, when you look at Orion Nebulae (M42) through telescope, you will see the Nebulae is in grayish colour, but when you use a camera to take a picture of it, you will be able to see the colours of the Orion Nebulae.

False colour is what we called "Chromatic aberration". This is cause by the fact that light bends by a different amount on different wavelength when passing through glass. This will cause different wavelength to focus at a different point when light pass through a Lens. As a result, a bluish or purple ring (or halo) will appear around bright objects.

Hope the information above is useful. Have a nice day.

[Airconvent]

I would like to find out if it is true that some deep sky object would look nicer through photo then through the telescope? 2) What is false color? thanks alot

hi jingguo...so fast and you have forgotten Remus' recent interesting lesson at SP on mirrors and optics? looks like remus MUST compile his lessons into a book for quick reference!

Anyway, thanks to WeiXing (as always) for providing a refresher course on false colour...!

rich

[ChaosKnight]

DSOs look better in photographs because of the long time exposure, allowing colour and detail to build up.

False colour is the wonderful, beautiful purple halo around bright stars if you look through my scope.

[rcj]

Hi Jingguo,
The definition of false colour besides its relation to chromatic aberration, might also be seen in a different perspective - if you look at radio images of galaxies in astronomy literature, sometimes they would mention that it is a flase colour image of some galaxy, so this can also imply that false colour is just another namesake given to imaging in a different portion of the electromagnetic spectrum using different colour spaces.
My two cents,
rcj

[fizzy123]

Hmmmm...... just to add on, false color can be totally or nearly eliminated using apochromatic scopes, which uses a triplet. a three element objective. Some pseudo-apo aka semi-apo use extra low dispersion glass and special coating thus image come close to true apo images. 8) Points to note, apo cause a bomb, a small 4 inch apo could cause as much as a 8 inch SCT, example LX50. They are only suited for the Extremely RICH n SPOILT astronomers. :roll:

[zong]

Haha, well I don't dispute that small apos cost about as much as a big SCT. However, I do want to point out that by comparing the views through scope, even a 4 inch apo can easily take down a 8 inch SCT.. Anyway apos are gettin' cheaper now, so we don't wanna offend those who do own 4 inch apos, yea?

[rcj]

well, actually not all apochromats are triplets, some are doublets like the FS series refractors from Takahashi. Even the term apochromat is being defined or designed differently by different independent manufacturers. Are we taking Abbe's classical definition of apochromatism or more stringent definitions that encompasses edge distortions into account as well like Back's design criteria for his TMB line. Being a former 4-inch apo owner before and having owned and used a C8 before as well, the contrast and sharpness excels very much, but of course the image will be dimmer due to the physical law of aperture relation to light gathering power. And yes, they do cost a bomb but again, this is a rather subjective argument since it varies with the individual involved and how much you are into getting the most out of your telescope. I have seen well collimated SCTs that performs very close to smaller apertured apochromats too, but the point to make is basically a question of whether what the individual's expectations are, and certainly it does not mean that somebody with higher expectations or having more strict requirements mean that the person is necessarily rich and spoilt. :-)
rcj

[fizzy123]

Hmm.... did I sound offensive? If yes then I apologize to all apo users. :oops: :oops: