Banding in Planetary Images

[chiltonstar]

I made one of my very occasional forays "over to the Dark Side" two nights ago to image Saturn (5" Mak, Phillips webcam, Registax + PS).

Although the image had plenty of sharpness (Cassini) and showed the banding on the disk clearly, the very high gain I was using (SharpCap) created visible horizontal lines across each frame; I assumed (wrongly!) that these would average out when the image was stacked - in fact they appeared to be emphasised if anything. Any way round this (experts?) apart from having more aperture so the image is brighter...?

Chris

[michael.h.f.wilkinson]

Can you show some images of the problem?

[dephelis]

I made one of my very occasional forays "over to the Dark Side" two nights ago to image Saturn (5" Mak, Phillips webcam, Registax + PS).

Although the image had plenty of sharpness (Cassini) and showed the banding on the disk clearly, the very high gain I was using (SharpCap) created visible horizontal lines across each frame; I assumed (wrongly!) that these would average out when the image was stacked - in fact they appeared to be emphasised if anything. Any way round this (experts?) apart from having more aperture so the image is brighter...?

Chris

Hi Chris,

Sounds like you're seeing the SPC900's noise pattern coming through because your gain is set too high.

Stacking isn't going to remove, and as you have seen is going to make it worse, because the noise pattern will be present in every frame and is not random . This results in stacking software treating it as detail instead of noise.

I would lower the gain and decrease the capture rate/increase exposure if you can. Also remember that your target should only be bright enough on screen for you to start to make out detail, in fact most of my recent shots with my 127 & DMK have been almost beyond that point. Taking a dark frame might also help, although it might have a negative effect on the planetary detail.

Damien

PS: Also try autostakkert!2, i find it gave much better stacking results with the SPC900 than RS.

[chiltonstar]

Hi Chris,

Sounds like you're seeing the SPC900's noise pattern coming through because your gain is set too high.

Stacking isn't going to remove, and as you have seen is going to make it worse, because the noise pattern will be present in every frame and is not random . This results in stacking software treating it as detail instead of noise.

I would lower the gain and decrease the capture rate/increase exposure if you can. Also remember that your target should only be bright enough on screen for you to start to make out detail, in fact most of my recent shots with my 127 & DMK have been almost beyond that point. Taking a dark frame might also help, although it might have a negative effect on the planetary detail.

Damien

PS: Also try autostakkert!2, i find it gave much better stacking results with the SPC900 than RS.

Damien - thanks very much for this advice - I'll have another try if the sky clears again before Saturn disappears from the evening sky!

Michael - maybe I'll post a "before and after" image if I can get any real improvement (I can see from other posts what I should be aiming for).

Chris

[dephelis]

Damien - thanks very much for this advice - I'll have another try if the sky clears again before Saturn disappears from the evening sky!

Michael - maybe I'll post a "before and after" image if I can get any real improvement (I can see from other posts what I should be aiming for).

Chris

On rereading my post, I just wanted to clarify that a dark frame won't help if the gain is too high!

Good luck