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Old 08-06-2016, 03:33 PM
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Atmos (Colin)
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Join Date: Aug 2011
Location: Melbourne
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Originally Posted by glend View Post
Richard, in regard to the spectrum response, Ha is down there are well and I have plenty of Ha, Sii is not much further along. However, when I look at the spectrum chart on the ZWO website I can see that it is less responsive in that part.

But since Ha is so good, unless the cover glass is a cut filter that is affecting Sii spectrum, then I am sure it is just something stupid I have done along the way. I have just been playing around stretching a single Sii sub and it has more signal than my stack of Sii appeared to have. Even on the SGP display I could see signal on individual Sii frames. I need to go back through what I did in DSS with that stack.

Uodate: looking back at my Trifud SII data it was pretty skinny as well when shot on equivalent integration times to Ha and Oiii. I will test tonight on M16 again running just Sii to build up more signal. Is there a 'standard ratio'?
Below is an example of signal strength of SII. The first shows them at their relative strengths to one another. The SII is a LOT dimmer than the Ha. The second shows SII under a normal stretch just to give a bit of an idea of how much it does get stretched.

The main thing to note that is of importance to you Glen is that more data does not change the relative signal strength. If you were to put another 10 hours into SII it would not make it brighter against the Ha, only make it smoother and less noisy.
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Click for full-size image (Normal Stretch.jpg)
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