QHY8 - H-alpha Response ?

[jcm]

I have the option of obtaining a 2" H-alpha filter.

Is the H-alpha sensitivity of the QHY8 good enough to make decent H-alpha images? ( thinking of combining these with the full colour image)

John

[Merlin66]

According to the data I can find, it has the same sensor as the Canon 50D.

Buil has done a comparison.

http://astrosurf.com/buil/50d/test.htm

This shows about 10% efficiency at Ha..... Hmmm

[mcrossley]

No same sensor as the Nikon D70/50. Many people are taking great Ha shots with the QHY8. The QE at Ha line is about 50%.

Mark

[jcm]

I have managed to find a response curve for the QHY 8.

The H-alpha line is at 656 nm.

So the response at H-alpha looks more like 45 to 50% ??

John

[SteveL]

The QHY8 works great for Ha imaging... honest!

[MartinB]

Well worth having the Ha filter John as Steve's pics show. You do need to be prepared for longer exposures compared with a mono chip though.

[jcm]

Looks like its worth a bit of extra time to get an H-alpha image.

Will have a go - if only the clouds would clear

John

PS Thanks for the sample images , Steve.

[Merlin66]

I stand corrected:embarassed:

Further checking shows it's the Sony ICX 453AQ chip, the same as the ones in the Nikon D40-D70 series cameras.

( I believe the red sensitivity comes from the fact that there's no UV-IR filter built in like the std DSLR's - so it works like a modded DSLR)

They do have an IR filter; this blocks above 676nm.

[jcm]

Thanks Merlin66 for the extra info.

I think some people who have the QHY8 have removed the standard filter and replaced it.

John

[MartinB]

My QHY8 came with a clear glass filter and an ir block. You have to be very careful about substituting this filter unless you actually mount something else within the nosepiece since any the arrangement needs to be airtight to avoid icing. I know, I've tried!

[jcm]

My QHY8 came with a clear glass filter and an ir block. You have to be very careful about substituting this filter unless you actually mount something else within the nosepiece since any the arrangement needs to be airtight to avoid icing. I know, I've tried!

Yep , after careful thought I think I will leave this filter in place and see what is produced when I try the H-alpha fiter.

John

[Merlin66]

Shouldn't affect the Ha response; the cut-off, according to the graph is well beyond this wavelength.

[jcm]

Shouldn't affect the Ha response; the cut-off, according to the graph is well beyond this wavelength.

Thanks for the confirmation.

If its clear tomorrow ( IF ) I should be able to give it a go - 2" H-alpha filter arrives tomorrow.

John

[SteveL]

All my QHY8 Ha images were taken with the IR cut nose piece installed as well.

[jcm]

All my QHY8 Ha images were taken with the IR cut nose piece installed as well.

Thanks for the further confirmation , Steve.

John