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Contains:  NGC 4627, NGC 4631, NGC 4656, NGC 4657
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NGC4631 & 4656, 


NGC4631 & 4656
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NGC4631 & 4656

Technical card

Dates:April 29, 2019

AstroDon 5nm Ha filter: 4x600" (gain: 0.00) -18C bin 1x1
ZWO new B: 10x120" (gain: 0.00) -18C bin 1x1
ZWO new G: 10x120" (gain: 0.00) -18C bin 1x1
ZWO new L: 30x120" (gain: 0.00) -18C bin 1x1
ZWO new R: 10x120" (gain: 0.00) -18C bin 1x1

Integration: 2.7 hours

Avg. Moon age: 24.43 days

Avg. Moon phase: 26.64%

Mean SQM: 21.20

Mean FWHM: 3.10

Temperature: 10.00

Basic astrometry details job: 2719120

RA center: 12h 42' 47"

DEC center: +32° 20' 34"

Pixel scale: 0.912 arcsec/pixel

Orientation: 348.281 degrees

Field radius: 0.735 degrees

Resolution: 4651x3474

Locations: Duc, Prayssas, Lot et Garonne, France

Data source: Backyard


During this imaging session I did my first automated merian flip !!!!
It was an "attended" meridian flip, I was able to check that all was going very very well :
- At 0h11 (30 april) light frame n°24 ended and initiated the MF
- SGP performed a plate solve for "sync" current coordinates
- Mount move from W to E side of pier (PHD2 idsconneted at the same time)
- SGP performed Centering routine (in the Target Offset mode) and after 3 iterations obtained less than 5 pixels total error (5 arcsec).
- SGP relauch PHD2 in (my multi star) autoselect and stabilize guiding
- SGP performed auto focus routine (which pause guiding)
- At 0h17 : SGP initiate Light frame n°25
The total MF duration was 6 minutes.

Original image is LRGB without Ha.
I selected gain 0 (5e- / ADU) by mistake especially for the Ha frames which were RON dominated.

The processing was done in PI as follow (version original):
For each L, R ,G ,B and Ha channels :
- Flat Field Dark Substraction
- Flat Field Integration
- Images Calibration (Dark Substraction and FF correction)
- Cosmetic Correction
- Image Registration
- Image Integration
- DBE or ABE
- Deconvolution masked with 2.3 pixel psf
- TGV denoise for Light frame only
Then :
- Creating RGB image from RGB channels
- Color balance and Color saturation on stars of RGB
- Nonlinear Image Creation with L and RGB and Ha
- Extract R, g, b channels from RGB
- Created LRGB color image
- Add Ha to R in NL mode
- Created LRGBHa image
- Use clone stamp to clean some red artefacts coming from Ha channel adding

Final image adjustments performed in Iphoto on Imac (levels adjustments, +10% color sat, crop and deflip)



License: None (All rights reserved)


  • NGC4631 & 4656, 


  • NGC4631 & 4656, 


  • NGC4631 & 4656, 


  • Final
    NGC4631 & 4656, 




Description: RGB only


Description: L frames only


Description: L RGB Ha

Sky plot

Sky plot


NGC4631 & 4656,