SingAstro

Hi,

would appreciate if someone could enlighten me on how to read a transmission curve. the Transmission[%] and the Wavelength. Does it mean the higher the curve/line, the clearer we can see?

Thanks.

Hi,eMinity
If you are talking about filter's transmission curve;it is--the height of the curve indicates how many % of that wavelength light it tranmit-- but transmission curve is not everything.If you are dealing with interference filter;then bands of rings may appear at unexpected places in your photo--even though it doesnt in your visual image--like the complaint of newtons ring in photo of the sun using narrow band Ha filter and with these you need to use special techniques to overcome it.Thanks.

Hi,
As what above had mention, the x-axis represent the wavelength of light and the y-axis will show how many percent of the light on that particular wavelength will pass through.

Have a nice day.

Thanks all for your replies. It helped me to understand much more now. But just need an example to be shown so that i could fully understand about this. Below is a link to a transmission chart of a UHC/LPR filter. The red line/curve belongs to the filter. And the grey line is said to be the sensitivty of the naked eye. is it true?

And, i saw this explaining at the website of the filter. it says "400nm is deep blue, at 520nm the human eye senses green and at 600nm red" does it mean that with the filter when the curve reaches high %% at maybe 520nm, i will be able to see green in a nebula??

http://www.singastro.org/album_showpage.php?pic_id=1149

Thanks guys. =)

Hi,

eMinity wrote:Thanks all for your replies. It helped me to understand much more now. But just need an example to be shown so that i could fully understand about this. Below is a link to a transmission chart of a UHC/LPR filter. The red line/curve belongs to the filter. And the grey line is said to be the sensitivty of the naked eye. is it true?

Yes, the gray region is the sensitivity curve of our eye.

eMinity wrote:And, i saw this explaining at the website of the filter. it says "400nm is deep blue, at 520nm the human eye senses green and at 600nm red" does it mean that with the filter when the curve reaches high %% at maybe 520nm, i will be able to see green in a nebula??

Yes... only if the surface brightness of the nebula is bright enough. That's why when you look through such filter, everything look greenish... including the stars.

Anyway, our eye are not sensitive to colours under very low light... everything look grayish. So most of the time, we can't see the colours of most nebula as their surface brightness is very low.

Have a nice day.

ohhh. so can i say that if the surface brightness of the Orion Nebula is really bright, and together with a filter which transmits high %% for blue,red,green, will it show me the colour of the Orion Nebula? Like those in pink and purplish.

Hi,

eMinity wrote:ohhh. so can i say that if the surface brightness of the Orion Nebula is really bright, and together with a filter which transmits high %% for blue,red,green, will it show me the colour of the Orion Nebula? Like those in pink and purplish.

Err... In that case, just don't use any filter lor...

Anyway, you can see a hint of colours in Orion Nebula especially the green, but largely depend on individual eyesight... some can see it, but some cannot. I think there is a thread on seeing colours in Orion Nebula in the past.

Have a nice day.

haha ok will go check it out. Anyway, thanks for the wonderful lesson

One last question i would like to clarify is that, if i use an average UHC/LPR filter, will i be able to see colours of M42? or will it still remain grey?

Thanks.

I tried a normal LPR filter on the orion nebula before but you can't really see the colours of it. But there is some green colour detected and the wings are much more stretched out.

oh. so i suppose UHC/LPR filters are able to show that minimal colour of some nebula right? im deciding to get an Orion Ultrablock UHC filter soon. anyone knows of it's performance?