Sh2 129 - Flying Bat nebula
SH2-129 is a large emission emission nebula in the constellation of Cepheus, has a very pronounced arc shape and sometimes is referred as the Flying Bat Nebula. Despite its size, it appears rather tenuous and the densest and most conspicuous part coincides with its eastern side. Its distance has been estimated at around 1300 light years, and thus falls a short distance from the edge of the Gouldian Belt. The surroundings of this nebula are particularly rich in molecular clouds, first of all the great dark nebulous system responsible for the concealment of a large part of the Milky Way in the direction of Cepheus.
Its Ha region is often overlooked due to its proximity of its much brighter neighbor often imaged IC 1396 - The Elephant's Trunk Nebula. Also close to the Sharples region is located the reflection nebula (vdB 140), seen in the lower portion of the field, just to the left of center.

OU4 - Squid Nebula.
The most remarkable about this region is the "Squid Nebula" due to its shape, officially called OU4. It was discovery by the freencgh  astro-imager Nicolas Outters in 2011.  Description discovery  http://outters.fr/wp/wp-content/uploads/2015/12/decouverte-OU4-eu.pdf   This region is characterized by a very faint [OIII] emission that has a bipolar shape reminiscent of a planetary nebula, more recent evidence suggests that OU4 is located within SH2-129 itself and is a bipolar outflow emitting in the OIII spectrum, moving at the same rate as SH2-129, and possibly emanating from a triple star system located in the center of OU4 (HR8119, visible above as the bright star in the center of the Squid).
More information "Gas physical conditions and kinematics of the giant outflow Ou4"  https://hal.archives-ouvertes.fr/hal-01022286/document
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Sh2 129-Flaying Bat Nebula and OU4-Squid Nebula have been a captivating target since we started this hobby. In fact, we started doing sessions with the L-Pro and Enhance filters from April to June 2020 with a Canon R not modified and when I started processing the sessions at the end of June, we had a first shock of frustration when we noticed that there was only a very poor signal from the 'squid' Not to mention that the data from the Enhance filter suffered from deep patterns due to the fact that in those days we did not apply dittering during the acquisition.

Basically, almost 13 hours made with the Enhance filter were discarded in this new processing, not the data made with the L-Pro filter. This is probably the project in which Maurizio and I have invested the most time both in data acquisition and processing.

In the sessions carried out in 2021 between March-May and December with the Extreme and Triad Utra filter applying dittering and Canon Ra, despite having been made in Bortle 6-7 like the 2020 sessions, the results revealed something very different.

It is necessary to make a small note, Maurizio did only one session of almost 3.2 hours integration in Bortle 4 with the Triad Ultra filter, and I took the trouble to compare a stack made only with the Extreme and another with the Triad and it is surprising the amount of information obtained by the Triad filter compared to the Extreme alone of almost 44 hours.

The situation of the Bortle counts a lot without a doubt.

I did about ten different stacks between DDS and Siril RGB bilinear and 2 drizzle and extraction of Ha and [OIII] to make a final blending not yet conclusive. I got different results: some contradictory, others almost satisfactory.

However, the extraction of Ha and [OIII] has been surprising.

The Ha information extracted from the stack made with the Extreme+Triad filter has provided an impressive and detailed image of the 'Bat Nebula'.

The extraction of [OIII] turned out to be difficult to visualize, in the sense that to obtain more details of the 'squid' (which existed in the data) a strong stretch had to be made. I had to apply one arcsinh curves of 30% and another four of 10% so that the figure was fully visible. This resulted in cloudiness of the Bat Nebula becoming present. Was this normal? I do not know. However, there is an obvious presence [OIII]  in the 'light' parts of the clouds cover nebulae as well as at the base of the 'squid' and in the 'rosette' above.

It was inevitable not to wonder if there is really a good amount of [OIII] scattered around the area? Since we don't have a monochrome camera to understand how the strict capture of [OIII] with a dedicated filter appears, we don't know. The only reference I know of is the image of [OIII] made by Nico Carver on his website  https://www.nebulaphotos.com/img/sh2-129O3.jpg and Lorenzo Comolli  http://www.astrosurf.com/comolli/d204mb1.jpg  which is impressive that it only reveals the figure of the squid and certainly a small area in the base and in the rosette with no other elements around it.

Here how Ha and [OIII] appear after strech, clarity, dehaze, denoise, contrast made in starless versions.



The base of stars used were extracted from the stack made with the L-Pro and Triad Ultra filters.

When I proceeded to do a SHO-type blending with the extractions, it was not surprising that I obtained an image with strong blue settlement in the dark areas in addition to those expected in the 'squid', base and 'rosette'. But not so in the normal RGB stacks of Extreme alone, but in Extreme+Triad there is a light 'extra' component of blue than usual.

As a result of the details that emerged in both extractions, it led us to develop a grayscale image as a first approach to the entire process and it is what we have done for the moment and that we consider a quite satisfactory result when 95% of the data It was made from our backyard at Bortle 6-7 depending on the seen/moonlight of the night it was taken.

We will take a break on this gorgeous nebula that was pretty tricky to process, the color version will be done later as soon as I can.

We hope you like it and thanks for visiting us.

Processed, Sept-Oct 2022