[HeavyT]

Hi all

This summer I've dived into narrowband imaging with a mono astro cam (ASI1600MM pro). 100mm doublet at f7.6 (785mm fl or thereabouts). ZWO filters.

I've imaged the Pencil Nebula, have Thor's Helmet almost there, and have started on Eta Carina.

Last night I noticed my Carina Sii sub histogram in the same place as my Pencil Oiii histogram, both at 15 minute sub exposures.

*edit: I hasten to add: gain at 139/21 in all subs*

I believe Oiii let's more photons in than Sii, so that might explain it, also that the Sii signal in Carina might not be as bright as Ha or Oiii.

But given Carina is mag 3 and Pencil mag 14, I was expecting to achieve a healthy histogram with much shorter subs on Carina.

I'm using N.I.N.A. to run the sequence and I'm wondering if I've accidentally switched the filter naming or not entered correct settings to drive the histogram display...

Any thoughts welcome and appreciated!?

For the record: the stack of 25x900s looks basically noiseless and fairly well exposed in a pixinsight STF this morning. So it seems I got there, it just took longer than expected.

Clear skies all