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Contains:  M 92, NGC 6341
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Damned precession!  a city view of M92, 


            Edoardo Luca Radi...
Damned precession!  a city view of M92
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Damned precession! a city view of M92

Technical card

Imaging telescopes or lenses: C9.25

Imaging cameras: Moravian Instruments G3-16200 Mark II

Mounts: 10 Micron GM1000 HPS

Guiding cameras: 10Micron HPS System

Software: Main Sequence Software Seqence Generator Pro  ·  Pixinsight

Filters: Baader Planetarium G 2"  ·  Baader Planetarium R 2"  ·  Baader Planetarium B 2"  ·  Baader Planetarium Baader 1,25" L

Dates:April 15, 2020April 16, 2020

Baader Planetarium B 2": 7x300" bin 1x1
Baader Planetarium Baader 1,25" L: 14x300" bin 1x1
Baader Planetarium G 2": 7x300" bin 1x1
Baader Planetarium R 2": 6x300" -25C bin 1x1

Integration: 2.8 hours

Darks: ~30

Flats: ~20

Flat darks: ~20

Bias: ~50

Avg. Moon age: 23.12 days

Avg. Moon phase: 39.75%

Bortle Dark-Sky Scale: 7.00

Mean SQM: 18.70

Basic astrometry details job: 3425216

RA center: 17h 17' 43"

DEC center: +43° 7' 1"

Pixel scale: 0.514 arcsec/pixel

Orientation: 270.376 degrees

Field radius: 0.405 degrees

Resolution: 4422x3552

Locations: Castenedolo, Castenedolo, Italy

Data source: Backyard


Sometimes even simple errors may be instructive!

This picture of M92 is off center: it seems a simple pointing error, but nowadays pounts are very precise, and SGPRO checks the correct pointing before beginning the sequence so what's wrong?

So, the difference in position is caused by Earth lunisolar equinox precession.

I set in SGPRO the position of M92, got from SkySafary at 2020 equinox (already corrected for precession) but the mount expected Coordiantes at 2000 equinox so corrected (again) for precession.

Result: In this image the off center of M92 is exactly the amount of the precession in 20 years.



Edoardo Luca Radi...
License: Attribution-NonCommercial-NoDerivs Creative Commons

Sky plot

Sky plot


Damned precession!  a city view of M92, 


            Edoardo Luca Radi...