Looking for help with filters'

[Taff]

Hi' at the moment i have got a Light Pollution filter, CLS Nebula 1.25 and a CLS clip filter, OIII Filter, Hydrogen Beta Filter, on it's way.What i like to know do i need any other filters to help me to capture images because i am not sure because there are so many filters'.My Canon 500D camera is unmoded, Thanks for reading.Mark

[ronin]

Can I suggest you slow down a bit?

Filters are relatively "easy" you want a "Red" a "Green" and a "Blue". Usually Red is Ha 650nm (more or less), Blue and Green are the sort of problem. Many use OIII as Green and Hb as Blue. The reality is that one is 500nm and the other 490nm so almost the same. The reality is you collect in one band then you can allocate whatever colour you like. So Ha you could make Blue or Purple or whatever.

Next I cannot work out what a CLS Nebula filter is. CLS is City Light Suppression, so the CLS bit reads as nothing overly relevant to Nebula. A Nebula filter is often one that passes both OIII and Hb.

Without modification your DSLR will only receive about 22% of the Ha at the sensor.

Without the DSLR being debayered then I suspect that the OIII and Hb will in effect be the same, they are too close to each other in wavelength. The Bayer mask will be something like:

RGRGRGRGRGRG

GBGBGBGBGBGB

So light through the OIII will likely only be seen by the "G" pixels or only the "B" pixels, the "R" pixels will see nothing. You can work out the rest as in when Ha filter is in use the "G" and "B" pixels will see nothing. So with Ha only 1/4 of the pixels are being illuminated and collecting photons.

So there is a bit to think of.

[Uplooker]

As Ronin says - Stop!

Just use your Light Pollution filter and capture away.

You will get plenty of decent shots with just that and your DSLR

[Taff]

Thanks' for your help.Mark