Protecting a QHY5

[wasyoungonce (Brendan)]

Originally Posted by cybereye

I've just been thinking about the uv/ir filter to fix bloated stars when imaging using a ccd. Am I correct in the assumption that this is only an issue when using a refractor and not a reflector?

Cheers,
Mario

No not that I know of.

A reflector reflects all wavelengths to a common focus.

A refractor refracts (bends) wavelengths at differing rates according it's glass type (refraction index). APOs are supposed to bring most visible wavelengths to a common focus. Of course it would be neigh impossible to bring UV/IR to the same common focus as visible...they will be close but slightly different.

A refractor glass will attenuate some incident energy (thru reflection & dispersion) as well. A small amount ~3% or less. This is why they use coatings...to reduce reflections..and good glass to reduce dispersion of rays.

[cybereye (Mario)]

That's what I thought, only a refractor would have trouble with bloated stars as it can't bring all wavelengths to a common focus without the use of some nifty optics.

Cheers,
Mario

[wasyoungonce (Brendan)]

Originally Posted by cybereye

That's what I thought, only a refractor would have trouble with bloated stars as it can't bring all wavelengths to a common focus without the use of some nifty optics.

Cheers,
Mario

Ahh yes..I should have said ..yes..not no ...a double negative which was wrongly put buy me.

If you know what I mean.....I think I need a lie down!

[marki]

The aim of the UV/IR filter is to stop these wave lengths reaching the chip and prevent bloating due to the extra energy forcing electrons to flow. It would not matter what the scope type was IMO. If you have shallow wells best to make every photon count and block out what is not useful.

Mark