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Cygnus Mosaic Project


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Some time ago, I comment in the Samyang 135 Mega-Thread that I had resolved most of my issues with this lens, specially those regarding backfocus. Not perfect but well enough to deserve some fun imaging. So... I planned a large mosaic of the Cygnus region:

As this is a large-term project, I've planned to open this thread to comment on my progress so I can ask for advice and critiques (and you can gossip if interested 😉). So... there we go!


This is a proof of concept shoot to test if the whole idea is feasible and make sure I can fix anything prior to the actual shooting. Some details:

  • Main equipment: EQ6-R Pro + ZWO ASI183MM Pro + Samyang 135mm f2 (@ f2.8) + Baader SHO 6.5nm Narrowband Filters
  • Other equipment: ZWO EFWmini filter wheel + ZWO EAF focuser + ZWO ASI120MM Mini + William Optics UniGuide 32mm + Astrodymium Ring System
  • Imaging: 4x3 mosaic with 1x300s Ha + NINA for planning and data acquisition.
  • Conditions: Bortle 4 backyard according to LightPollutionMap (probably Bortle 5 now) with some streetlights pointing towards my telescope placement.
  • Processing: data calibrated with darks using WBPP and merged with GradientMergeMosaic with Pixinsight. Simple STF applied, no further processing.

My OTA doesn't have a rotator so adjusting orientation is a bit of a pain due to the belt-system focuser I use. So I had to carefully select the orientation and panel disposition so I can get individual panels as 'interesting individual pictures' while adding more integration to the mosaic. My initial plan is to build a 'base' mosaic with 12x300s per filter (SHO) per panel: (4x3) x (3x1h)=36h total. Then, I can add more integration up to 3h/filter: 3x36h=108h.

I know this is quite ambitious for my sky conditions -clouds and rain most of the year- and my skill but, well, it will be fun and I won't have to rack my brain choosing targets for a while 😅

Feel free to ask, critique, correct or whatever, any comment will be welcome!

Edited by aleixandrus
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Weather was awful in the past month so I couldn't advance as much as I hoped. However, I get a unexpected row of three clear nights. Seeing was not wonderful but with my pixel scale (3.67"/px), even with poor seeing I think it worth shooting as I won't 'upresolve' the seeing never ever. So, I get some data. And I couldn't resist to stack everything and build a second test mosaic, this time in color:


I know, I know, there are many things wrong but... I like it a lot! At least, I think the project is going along the right way, which is peace of mind for me. Some details of the above pic:

This is a 3x3 mosaic instead the 4x3 I planed. I don't have enough data to add the 'Tulip Nebula' column and weather will be awful the next weeks so I stack what I have. This mosaics add 25-26h total (1h/filter/panel approximately) after removing bad frames, captured during 5 nights in 7 weeks (I also have a side project so I reserve some night time for it). I calibrated and stacked the data with WBPP, combined SHO with ChannelCombination (no normalization) and merged with GradientMergeMosaic (no DBE applied) just to make sure everything worked together. There are two large 'pinched stars' I need to fix and some noise differences from panel to panel, but nothing completely wrong, which is good news. I add some curve adjustments to stretch data, SCNR to remove and some saturation. Colors are very wrong, background is not neutralized, there are some gradients specially in the right side... but anything I think I couldn't fix.

I didn't any further processing as the SHO master file is around 3GB and, with my old computer, a simple SCNR takes up to 4 minutes to run. I couldn't imagine how long will take StarXTerminator! 🙈 I'm afraid I'll have to consider binning the image...

Any thoughts?

Edited by aleixandrus
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