The region of the Westerhout 50 radio source is very rarely photographed. It is associated with the supernova remnant SNR 039.7-02.0, whose shape and color are peculiar. I don't know of any other SHO images of this SNR. I have reviewed the nature of the object and its possibilities for astrophotographers, and I find it interesting to communicate this little review, based on iconic images.

1. OBJECTIVE.
When I started taking the first shots of W50, I didn't know what I was imaging. I don't know the object appeared on my list of possible targets in Aquila. I just studied  @Maciej 's photo on Astrobin  [1]  (2021) https://www.astrobin.com/full/a60apr/0/ , and I started. With the photo in progress, I found references in which W50 was identified with the “Manatee Nebula”, although this one did not look anything like Maciej's or my shots. I had to study a little more. I worked to partially clarify my ideas about the nature and topography of the object. The scientiphic material was numerous, but I found few amateur images. I was intrigued to see what I could achieve in a SHO narrowband composition, and I set out to continue shooting as long as the autumn allowed it.

2. WESTERHOUT 50, SNR 039.7-02.0,  SS 433 AND THE MANATEE NEBULA.
Three questions:
1) What are these objects? What relationship do they have?
2) What is its location and topography?
3) What emission in visible light can we try to capture.

To answer, I have limited myself to reviewing a few references that contained iconic images, showing them in historical order.

In 1956, the Dwingeloo Radio Observatory was completed in the northeast of the Netherlands (figure 1). It was equipped with a single 25-meter antenna, with a beam width of 0.57º and a frequency of 1390 Mc/s. At the time it was the largest radio observatory in the world [2]. His first task was carried out by Gart Westerhout, performing a scan of discrete radio sources along the ridge of our galaxy. His work was published in 1958 [3], and cataloged 82 sources. Of these, 32 are associated with Sharpless, Gum or RCW nebulae. At least 16 sources are associated with important star-forming and HII regions of the Milky Way that do not appear in the Sharpless, Gum, or RCW catalogues. Another 9 sources appear to be supernova remnants (SNR) not associated with nebulae in the Sharpless, Gum, or RCW3 catalogues. Westerhout 50 (W50) belongs to the latter group, and is associated with supernova remnant SNR 039.7-02.0. However, at the time of Westerhout's publication this association was not yet known, and the overlay with the Sky Palomar Survey images concluded "no trace of emission, some obscuration." SNR 039.7-02.0 exploded about 20,000 years ago. The remaining black hole feeds on a neighboring star, forming a microquasar. The trapped particles accumulate in an accretion disk around the residual black hole, spinning rapidly over an orbital period of almost 14 days. An enormous magnetic field is created whose lines channel the particles outward in two powerful jets that travel at a relativistic speed. This system shines brightly in both radio waves and X-rays, and is collectively known as microquasar SS 433 (Stephenson Sanduleak 433). SNR 039.7-02.0 is one of the largest known SNR, with a diameter greater than about 700 light years, and occupies about 2º in the sky.


Figure 1
Dwingeloo Radio Observatory antenna.
Source: Wikipedia [2].

We had to wait until a higher resolution was available for W50 to become an image. The Karl G. Jansky Very Large Array (VLA) belongs to the National Radio Astronomy Observatory (NRAO). It is a set of 28 25 meters radio antennas arranged in a Y, located in the New Mexico desert. Its resolution is 0.2 arcseconds to 0.04 arcseconds. In 1998 GM Dubner et al [4] composited images of W50 using VLA data (figure 2). The shape is clearly outlined, with a circle broken at the ends by opposing protuberances, and a helical appearance more visible in the eastern part.


Figure 2
Dubner et al. 1998  [4] VLA radio continuum image of W50 at 1465 MHz represented in gray scale. The gray scale varies from 1 to 25 mJy beam~1.
©1998. The American Astronomical Society. All rights reserved. Printed in U.S.A. Reproduced with permission of the first author

In 2007 Boumis et al. [5] studied the interaction between the jets of the microquasar SS 433 and Westerhout 50, obtaining images in HII, OIII and NII that they superimposed on the Dubner radio images (figure 3). Their images show the concentration of material visible at the ends of the W50. The spherical central body with little visible signal represents the undeformed sphere of the supernova expansion. In the HII image superimposed on the radio image, there is also a concentration of radio signal in the northwest corresponding to LBN 109, while in the east side, the image published on Astrobin by Maciej in 2021 and the mine are defined.


Figure 3
P. Boumis et al. 2007  [5]. The correlation between the ∼2.◦3×2.◦5 negative continuum-subtracted mosaic of W50 in the light of Hα +[N II] and the radio emission at 1465 MHz (solid lines). The 1465 MHz (Dubner et al. 1998) radio contours scale linearly from 1 × 10−2 to 0.1 Jy beam−1. The strong radio source to the north-west is LBN 109 (see the text). The image has been smoothed to suppress the residual from the imperfect continuum subtraction. The horizontal line segments seennear overexposed stars in this figure and the next figures are due to the blooming effect. © 2007 The Authors.  Journal compilation © 2007 RAS. © 2007 The Authors.  Journal compilation © 2007 RAS. Reproduced with permission of the main autor.

In 2011, B. Saxton and M. Goss obtained with the VLA the image of W50 that would give it the name “Manatee Nebula”  [6]  (figure 4). In the image, the radio emission appears in green on a background of infrared and dust, the head in the west and the tail in the east. Like Dubner's image, it shows how the microquasar jets have made their way through the expanding gases of the supernova bubble and have created protuberances on both sides. The spinning top movements of the jets form corkscrew-shaped patterns. Upon seeing this image, Heidi Winter, the director's executive assistant, noted its resemblance to a manatee. The NRAO, in collaboration with the U.S. Fish and Wildlife Service proposed the name “Manatee Nebula” for W50, and made its presentation during the annual Manatee Festival, in Crystal River, Florida.


Figure 4
The Manatee Nebula. Image Credits: NRAO/AUI/NSF, K. Golap, M. Goss; NASA’s Wide Field Survey Explorer (WISE)
Image Credits: NRAO/AUI/NSF, K. Golap, M. Goss; NASA’s Wide Field Survey Explorer (WISE)
Copyright © 2024 Associated Universities, Inc. / Credit: B. Saxton, (NRAO/AUI/NSF) from data provided by M. Goss, et al.

In 2022 S. Safi-Harb et al [7]  conducted a study on the X-ray emission on the eastern side of W50, and composed a multi-wavelength image. They superimposed other authors' x-ray, radio, and visible light data on their own. The image (figure 5) is very striking and demonstrative. The green areas are those of the visible light spectrum.


Figure 5
Safi-Harb S, et al. 2022. [7] Multi-wavelength image of the W50 nebula. Red: Radio (Dubner et al. 1998), Green: Optical (Boumis et al. 2007), Yellow: Soft X-rays (0.5–1 keV), Magenta: Medium energy X-rays (1–2 keV), Cyan: Hard X-ray emission (2–12 keV). The eastern lobe X-ray image highlights the XMM-Newton data presented in this work (with the brightening at the edge of the field of view cropped here to highlight the source emission). The western lobe X-ray image shows only partial Chandra coverage of part of the nebula (Moldowan et al. 2005).
ttps://iopscience.iop.org/article/10.3847/1538-4357/ac7c05. Licence: Creative Commons Attribution 4.0 licence (http://creativecommons.org/licenses/by/4.0/).

Thus, W50 is a radio source, the Manatee Nebula is the image of W50 in radio emission, SNR 039.7-02.0 is a supernova remnant accessible to visual spectrum astrophotography, and SS 433 is the associated microquasar responsible for the particularities of this SNR.

3. IMAGE CAPTURE AND PROCESSING.
I took my image between October 7th and December 16st, 2023. Afterwards the object was too low, and the light pollution on the horizon prevented me from continuing. I have a suburban environment 8 km from the city of Alcoy (Alicante, Spain). I used an Orion Optics UK tube with Orion UK Winne 0.95 corrector and a QHY 268M camera (pixel size 3.76 mcm), on a Sky-Watcher EQ8-R Pro mount, and autoguiding with a 60/120 refractor and a ZWO ASI 120 MM camera. Filters: Baader HII 7 nm 2", Baader OIII 8.5 nm 2", Omegon SII 12 nm 2". The shots were 5' in bin X2, with Gain 56 and Ofsset 80 for the nebula (SHO), and Gain 26 Offset 80 for the stars (RGB), Tª -10ºC. Dither every 3 shots. I added 30' RGB shots for the stars. The summary of the capture was:

HII: 310 x 300s = 1550m = 25h 50m (Gain 56 Ofsset 80 bin x2)
OIII: 10 x 600s + 196 x 300s = 1080m = 18h (Gain 56 Ofsset 80 binx2)
SII: 188 x 300s = 960m = 15h 40m (Gain 56 Ofsset 80 bin x2)
Total HSO: 59h 30m
B: 73 x 30s = 36.5m (Gain 26 Offset 80 bin x2)
G: 64 x 30s = 32m (Gain 26 Offset 80 bin x2)
R: 75 x 30s = 37.5m (Gain 26 Offset 80 bin x2)
Total RGB: 106m = 1h 46m
Total exposure: 61 h 16 m

The calibration was done without darks, with 100 bias shots and 100 flat shots for each filter. Preprocessing and processing were done with PixInsight Core Ripley v.1.8. To process,  I used the stacked images with drizzle x2.The images showed a very high density of stars obscuring the nebula. In the foreground, a well-defined cloud of stars was superimposed on the nebula crossing from northest to southweast (the oval marks the location of the nebula's  signal, and red arrows marks the cloud of stars). The background is occupied by a multitude of  stars, reddish due to radiation absorption phenomena. The blue star on the left is 22 Aqu, magnitude 5.64. The gradients were not intense, and a non-uniform background could be guessed, with weak nebulosities.


Figure 6
RGB image with short shots to capture stars. Processing: ABE of the R, G and B masters, LinearFit, RGB fusion, SPCC and stretching of the STF. The ellipse represents the location of W50. The arrows mark a delimited area of higher stellar density. Plate Solve with PixInsight: focal length 941.06 mm, pixel size 3.76 mcm, resolution 0.824 arcsec/pix, rotation -176.621, center: RA 19 14 18.065, Dec + 4 57 51.54, field of view 1º 21' 3.2” x 52' 6.8” .

 I removed the stars from the S, H and O masters as the first step after cropping, and processed the channels independently until they were stretched. Color was obtained with SHO palette without modification in PixelMath, combining the almost completely processed HSO images. The hue was modified after the combination for aesthetic reasons.In the masters the signal was poor despite the long exposure. The HII image showed a complex filamentous structure with faint nebulosities in the background. In the OIII image, a well-defined arc was marked on the edge of the structures visible in HII. The SII image recorded little signal despite not being a particularly restrictive filter (12 nm), in the form of scattered nuclei also coinciding with structures visible in HII with poor signal in the background. These are the narrowband masters, without stars,  stretched from the STF images (figures 7, 8, 9):


Figure 7
HII (mean 0.0026817, median 0.0026799, sd 0.0000388). Plate solve equal to RGB.


Figure 8
OIII (mean 0.0046268, median 0.0046263, sd 0.0000507). Plate solve equal to RGB.


Figure 9
SII (median 0.0037604, 0.0037628, sd 0.0000499). Plate solve equal to RGB.

 In the processing of each channel, the sequence was: 1) Retouching of the remaining halos after StarXTerminator with CloneStamp. 2) Background modeling with GraXpert v. 2.2.2. 3) Smooth deconvolution with BlurXTerminator. 4) Noise reduction with NoiseXTerminator. 5) Delinearization with GHS. 6) Luminance adjustment with Curves. 7) New deconvolution and noise adjustment on channel H for use as luminance. 9) New noise adjustment on H, S and O. 8) SHO fusion with PixelMath. With the SHO image: the sequence wa 1) Hue change with Curves-Hue and SNCR. 2) Use as chrominance on the H image. 3) Fusion with RGB stars. 4) Final crop. 5) New deconvolution  with BlurXTerminator. 6) Contrast with Curves.

After a new crop, the plate solve of the final image was:
Final image:  W50 / SNR 039.7-02.0  (Eastern region) in SHO.
Plate Solve (PixInsight, Image Plate Solver script version 5.6.6 ):
Rotation ................. 3.389 deg
Reference system ......... ICRS
Observation start time ... 2023-10-01 12:00:00 UTC
Focal distance ........... 951.04 mm
Pixel size ............... 3.80 um
Field of view ............ 1d 7' 39.8" x 46' 25.7"
Image center ............. RA: 19 14 42.592  Dec:  +4 54 39.02  ex: +0.029889 px  ey: +0.006393 px
Image bounds:
   top-left .............. RA: 19 17 03.670  Dec:  +5 15 47.82  ex: -0.065841 px  ey: -0.074108 px
   top-right ............. RA: 19 12 32.436  Dec:  +5 19 48.81  ex: +0.014836 px  ey: +0.002580 px
   bottom-left ........... RA: 19 16 52.484  Dec:  +4 29 28.25  ex: +0.074580 px  ey: -0.001326 px
   bottom-right .......... RA: 19 12 21.596  Dec:  +4 33 28.28  ex: +0.054936 px  ey: -0.003482 px

This area is a part of the eastern region of the SNR. Superimposing it on the Bourmis image, which includes visual and radio signal, the result is:


Figure 10
Luminance of the SHO photograph superimposed on that of P. Boumis, 2007  [5] ([HII+NII] + [radio emission –Dubner, 1998-   [url=https://iopscience.iop.org/article/10.1086/300537/pdf][4] ] )

5. CONCLUSION.
W50, a radio source, may be a suitable visual object for amateur astrophotographers. Obviously we will not see the manatee. We will capture the remains of the supernova SNR 039.7-02.0 with bright emission regions excited and distorted by the jets of the microquasar SS 433. It is large and weak, and in front of it are a multitude of stars and interstellar material that hide a good part of its structure .

I want to vindicate the value of the W50 photograph taken by Maciej. I think it is the first one made by an amateur. In the same year Maciej also captured the radio source  SNR G119.5+10.2 aka CTA 1

REFERENCES.
1-    Westerhout 50 by Maciej in Astrobin
2-     Dwingeloo_Radibservatory_Wikipedia
3-      Westerhout G., 1958, Bull. Astron. Inst. Netherlands, vol.14, p.215, "A Survey of the Continuous Radiation from the Galactic System at a Frequency of 1390 Mc/s."   https://articles.adsabs.harvard.edu//full/1958BAN....14..215W/0000215.000.html
4-      Dubner GM, et al. A high-resolution radio study of the W50-SS 433 system and the sorrounding mEdium. The Astronomical Journal, 116:1842-1855, 1998 October.   https://iopscience.iop.org/article/10.1086/300537/pdf
5-      P Boumis et al. Deep optical observations of the interaction of the SS 433 microquasar  jet with the W50 radio continuum Shell. Mon. Not. R. Astron. Soc. 381, 308–318 (2007)  Article
6-      https://public.nrao.edu/gallery/w50-the-manatee-nebula/
7-      Safi-Harb S, et al. Hard X-Ray Emission from the Eastern Jet of SS 433 Powering the W50 “Manatee” Nebula: Evidence for Particle Reacceleration. The Astrophysical Journal, 935:163 (14pp), 2022 August 20.  Article