The Trunk Nebula + Giacomo Pro + L-Synergy,L-eXtreme

The Trunk Nebula

Image Credit: Giacomo Pro

Filters: Optolong L-Synergy and L-eXtreme (L2 Dual Combo Set)

 

 

I chose the Trunk Nebula to perform astrophotography tests with the new Optolong L-Synergy filter. This is a 7nm dual-band SII-OIII narrowband light pollution filter. 
To compose the Hubble SHO palette on the chosen subject, I needed to capture ionised hydrogen with another filter, and I chose the historic L-Extreme filter, also from Optolong. 
I am sure that any type of dual-band Ha-OIII filter, such as the L-Para or L-Ultimate, or a single Ha filter would have been fine for this purpose, but the choice was dictated by the fact that the L-Extreme is also a 7nm filter, allowing me to maintain the same bandwidth values when shooting the subject.
The shots were taken over two nights with a six-hour integration for each filter, alternating every two hours to maintain, as far as possible, the same environmental conditions, under a Bortle 6 sky with the Moon at 96%, conditions that were certainly prohibitive but, in my humble opinion, ideal for a test.
I used a colour camera for the shoot, so the correct extraction of the channel bandwidths is always a bit problematic due to the Bayer matrix on the sensor. 
To create the palette, I used the red channel of the L-Extreme master for the Ha and the red channel of the L-Synergy master for the SII. For the third channel of the SHO palette, I did several combination tests with the remaining G and B channels of the two masters. In my opinion, the most balanced, pleasing result, without excessive boosts and easier to manage during development, was obtained with an average of the G and B channels of the two masters to be assigned to OIII.
I was satisfied with the final result, especially given the conditions in which the images were taken, and I am confident that under a less polluted sky, significantly better results could be achieved. I also found the classic magenta colour of the stars typical of the Hubble palette very pleasing, which I deliberately left unchanged in order to respect the palette itself.
Still on the subject of stars, it should be noted that the L-Synergy master was completely free of star halos. In fact, those that are slightly noticeable in the final photo, on the brightest stars, are due to the combination of channels with the L-Extreme, which, as is well known, suffers from this problem, and I did not apply any type of correction.

 

 

Light 73 x 300" Filter: Optolong L-Extreme
Light 73 x 300" Filter: Optolong L-Synergy
Camera: Asi 294 mc pro
Telescope: Sky-Watcher Newton 200/1000 PDS
Mount: Skywatcher Eq 6-r Pro
Acquisition: Asiair Plus
Software: DSS - Pixinsight – Photoshop
Shots: 05-06/09/2025
Location: Torricella (TA) ITALY
Average moon phase: 96%
Author: PRO’ GIACOMO.

Hope you like it.