Ha for CCD, 13 or 6 nanometres?

[ollypenrice]

Anyone tried comparing the Astronomik 13 and 6 NM Ha filtres? I currently have the 13 but need another one now that I'm offering 2 cameras. Should I go for the costlier 6? I don't have any light pollution to worry about and am happy with the present one but don't know what the difference ammounts to.

Thanks,

Olly

[brianb]

The 6 lets through less light that isn't Ha emission, so less sky glow (or longer exposures), Ha nebulae enhanced with respect to stars etc.

If your site is as dark as you say you will probably find little difference when the Moon is out of the way.

[ollypenrice]

Ah but there's a point I hadn't thought of; if imaging in the moonlght - which we do here quite a lot - the more aggressive filtre might be significantly better. Many thanks,

Olly

[Eddie]

The 12nm is just as good when imaging at full moon. The 6nm will give you more contrast and you will see less stars (focusing can be a little harder!) Also you will need about 5-10% more exposure (in theory you don't need any, but in the real world you do!!)

HTH,

Eddie

[ollypenrice]

Thanks Eddie. I'll save the dosh then, eh?

Olly

[Eddie]

I would! Then get a 6nm later on, or one of the custom scientific (4.5nm) or astrodon (3nm) one.

Eddie