Before imaging this object, I have seen many images of it made by other astrophotographers and observatories which brought to my attention the OIII nebulosity that surrounds this object. Most of those images, with clearly visible OIII, were made with filters and CCD cameras, so my expectations to catch it with just DSLR were very low and telling you the truth, I thought it was impossible.
When in the field, after all preparations, I like to take the test frame with the exposure that I plan to go for the rest of the night and stretch it very aggressively, to make notes of what have been captured by the sensor. To my very surprise, I noticed that I been able to catch some of the OIII and as a bonus, the very faint Ha nebulosity that is visible to the right of the Crescent nebula.
I have imaged for two nights and been able to gather 5 hours of clean and usable data. After stacking and processing, the OIII regions became more visible, but were still laying on the back of the noise, making it hard for me to pull them out during processing. Now, when I`m completely satisfied with Ha, I were after OIII.
I decided to go for another two nights and hopefully gather another 5 hours to improve SNR even more. Eventually, after 4 nights of imaging I did manage to pull out 10 hours (9 hours 45 minutes) of data and it was real pleasure to process it.
Link to the object's page:
http://www.myastroscience.com/#!crescent-nebula/c23p7 Thank you for looking!
