0.Note：

1. Background is not totally black, pls see full size PNG file.
2. Three color space revisions for sRGB, AdobeRGB, DCI-P3 are provided,  see the one matches your screen color space is recommended.
3. The color of the galaxy in all three revisions,  especially for its arms, was adjusted to look like the of aquamarine blue or bright marin blue (you will sort it to blue, not cyan), not tiffany blue (which has more green). 

1.About the M101:
Located at the astonishing distance of about 21 million light-years from Earth, this beautiful grand-design spiral galaxy, M101, aka Pinwheel galaxy, spans across 170 kly and is an example of magnificent deep-sky stellar factories.

The Pinwheel galaxy was first observed in the spring of 1781 by the French astronomer Pierre Méchain who reported his discovery to the famous colleague Charles Messier, the author of an astronomical catalogue listing 110 nebulae, faint star clusters and other deep-sky objects which later became known as the Messier objects. The Pinwheel galaxy was the 101th entry in the catalogue and was therefore dubbed Messier 101 or M101.

Though strikingly large in comparison to the Milky Way, the Pinwheel galaxy is very faint due to its long distance. The spiral structure of the galaxy was not observed until the late 19th century as the technology of the optical telescopes developed and improved further. The Anglo-Irish astronomer Lord Rosse was the first to look at the Pinwheel galaxy using a 72-inch Newtonian reflector and report its spiral structure. (Write up by The Nine Planets)

2.the C.L.A.P.T.
The China Long-Focal-Length Astro Photography Team (abbr: C.L.A.P.T.) was established in 2024 and consists of 17 astro photography enthusiasts from China. Members of the team are either amateur or professional photographers who use long focal length telescopes at remote observatories within China for their shoots. The team usually plans to take 2 to 3 astro targets every month, and team members can freely sign up to participate in Co- Shoots. Before the shoot, members will unify the coordinates and shooting parameters, and each of them will compile and sharing  data and generate a Master file after shooting.

3. CLAPT M101, Members of the Squad:
1. Qu Chen from Taiyuge Obs.
2. Barry Lee from Daocheng Galacier Obs.
3. Yzuo Liu from Daocheng Galacier Obs.
4. John C.Yu from Daocheng Galacier Obs.

4. Integartion Info
The total integation is about 200 hrs,  consists of the following data taken by 4 team members of the squad. 

1. Lum = 68h 15m
2. Red = 24h 25m
3. Green = 21h 30m
4. Blue = 22h 45m
5. NB Ha = 63h 30m

Each of us contributed more than 25hrs raw data, with good balacne between each channel (Average is about 3:1:1:1:2).  About 50% of NB Ha data was collect under 60% or high moon phase, with relatively low SNR on each single frame. Tabel below shows how much data was taken by each of us. (Pls ingore all filters below are Antlia, that was not true.)

5.Equipment
Both John, Barry and Yanzo use RC telescope of either William Optics or GSO. The angle of stars spike are excatlly the same. Barry upgraded his telescope from 10'' to 12'' at the end of March, and he was pretty satisfied with the 12'' WORC, beautiful, and easy to use. Chen uses his 6'' APO made by Sky-Rover (same one as TS 155 APO or any similar APO available now).
     5-A: Barry's Set 

1. Telescope: William Optics 10'' & 12" f/8 Ritchey-Chretien Truss Tube
2. Camera: ZWO ASI2600MM-Pro
3. Mount: Sky-watcher EQ8r-Pro
4. Filters: Antlia Dark Series LRGB, 3nm Ha
5. Flattener: William Optics Dr. Flat Master 0.8x for GSO RC (12"-16") (Flat-RC)
6. Location: Daocheng Glacier Observatory, Sichuan,China.

     5-B: John's Set

1. Telescope: William Optics 12" f/8 Ritchey-Chretien Truss Tube
2. Camera: ZWO ASI6200MM-Pro
3. Mount: iOptron CEM120EC
4. Filters: Antlia V Pro LRGB, 4.5nm Ha
5. Flattener: William Optics Dr. Flat Master 0.8x for GSO RC (12"-16") (Flat-RC)
6. Location: Daocheng Glacier Observatory, Sichuan,China.

 5-C: Qu Chen's Set

1. Telescope: Sky-Rover 155 F/8 APO Pro
2. Camera: QHY268M
3. Mount: EQ8r-Pro
4. Filters: Antlia V Pro LRGB, 4.5nm Ha
5. Flattener: Sky-Rover 1X Field Flattener for 155 APO Pro
6. Location: Taiyuge Observatory, Hebei,China.

5-D: Yanzuo Liu's Set

1. Telescope: 10" f/8 Ritchey-Chretien Truss Tube
2. Camera: ZWO ASI2600MM-Pro
3. Mount: AZ-EQ6
4. Filters: Optolong LRGB, 3nm Ha
5. Location: Daocheng Glacier Observatory, Sichuan,China.

4. PreProcess and Integration of 4 different FOV
After gathering all the data the squad taken, preprocess and integation was performed by John Yu with WBPP on PI, and AstroPixelProcessor (abbr. APP), respectively.

To accommodate 4 sets of data with very different FOV and resolution without leaving obvious defect on Master files (such as dark or noisy region on the edge of overlapping area, or unblacnced background brightness) while maximizing the FOV taken by WORC12+6200MMP was really a hard one. John has tried his best repair those defects using any method he found, including NSG, DBE, MSGC, etc.,  while the result was not satisfying. After few attempts, John achieved to find a way integrating all these data without leaving any defects.

4-A The Mix-FOV Integation Method

1. Calibration, StarAlignment , NSG (Normalized Scale Gradient, optional) data and Integation per set of data sort by contributors. You can also use WBPP (cali, register, inte) with autocrop on.
2. DBE or Gradient Correction on each channel & each contributor. For this data, that means 4*4=16 times of GC.
3. Do StarAlignment Again with FOV of WORC12 & 6200 as reference, performes integations and crop. You can also use WBPP with AutoCrop confirmed. Then performe DBE or Gradient Correction for the MasterLight you get with maximized SNR and overlapped area.
4. Load all masters you get from step 2 and 3, to AstroPixelProcessor, set MasterLight of WORC12 & 6200 as reference, select SNR for weighting, adjust parameters and run Integation. Note: Enabling LocalNomorlization in APP are NOT suggested.
5. If you follows all instructions, then you shall have a decent result, with highest SNR on overlapped regions and smooth background.

Special thanks to:  Grapeot, who kindly shared his briliant method of adding stretched Ha data to LRGB using Photoshop. He has uploaded tutorial on YouTube and Bilibili. 

Hope that you guys like this image!

C.S.

Barry, John, Yanz and Qu
C.L.A.P.T.