Something to post at last: NGC891, PGC9031, The Silver Sliver Galaxy in RGB

[windjammer]

Hi everyone

Here is an RGB broadband image of NGC891.  I started it in November but the clouds rolled in for the next two months.  A couple of clear nights this January and it is finished (sort of), not without a struggle.  A few weeks under covers and the 'scope gets cranky with the damp:  every plug and socket has to be reseated to chase off the gremlins.  And the forgetful operator retrained...

For the Blue filter I used a narrowband Hb 486nm filter, 8.5nm FWHM.  The doublet objective in the refractor never does a brilliant job on broadband blue exposures, but on this subject were unusually bad for some reason: enormous star haloes beyond fixing.  So I tried an Hb filter I have had for ages but never really used in anger, and it worked so well I think it will be standard procedure now.  So strictly speaking the pic is an RGHb.

I have kept the stars quite prominent and pulled up the background so you can see there are loads of galaxies lurking in the murk, beyond those catalogued in the annotated pic.  All those small, faint and hazy blobs that look a bit elliptical or spirally are probably galaxies in the distance.  The most distant galaxy catalogued that I could find listed in the NED database is PGC9101 (right and slightly below centre) that clocks in at a heroic 189Mpc or 600 Mlyrs.  The other 4-digit galaxies are around 90Mpc.  The 7-digit galaxies turned up nothing on Google unfortunately. Next time I might have the wit to include the galaxy cluster Abell 347 in the same frame.

Thanks to a posting on SGL it turns out there is a quasar! QSO J0222+4221 (NGC 891 X4 or CX0 J02224+4221) captured as well - red shift z =1.81, equating to a Hubble look back distance of 8.5 billion lyrs. Mind boggling. A personal distance record!  Location pic for the QSO is layered onto the snip attached.  

Exposure and gory processing info at the end.

QSO info:
https://www.deepskycorner.ch/obj/ngc891.en.php
 
https://stargazerslounge.com/topic/285853-another-quasar/

 

 

Annotated:

 

QSO finder:

 

 

 

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Data taken in Astronomik broadband and narrowband filters:R, G, Hb (486nm). RGHb total exposure time 12.3 hrs.  Also data taken B and Ha (656nm), though unused.

R 1x1 bin - 98x 120s= 3.3hrs, 6-7 November 2023, seeing 1.2", scope West side, prime focus
G 1x1 bin - 97x 120s = 3.2hrs, 7-8 November 2023, seeing 1.1", scope West side, prime focus
B 1x1 bin - 31x 120s = 1.0hrs, 11-12 November 2023, seeing 1.5", scope West side, prime focus
Ha 1x1 bin - 9x 600s = 1.5hrs, 14-15 November 2023, seeing 1.0", scope West side, prime focus

B 1x1 bin - 125x 120s = 4.2hrs, 15-16 January 2024, seeing 2.5", scope East side, prime focus
Ha 1x1 bin - 14x 600s = 2.3hrs, 16-17 January 2024, seeing 1.75", scope East side, prime focus
Hb 1x1 bin - 24x 600 = 4hrs, 18-19 January 2024, seeing 1.1", scope East side, prime focus
Hb 1x1 bin - 11x 600s = 1.8hrs, 19-20 January 2024, seeing  1.6", scope East side, prime focus

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Master Lights:
FWHM (pxl)    pre BXT        post BXT
R        3.284        1.918
G        3.282        2.032
Hb        4.239        2.959

B        3.089        -
Ha        3.239        2.034

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Plate solver:
Resolution ............... 0.624 arcsec/px
Focal distance ........... 760.38 mm
Pixel size ............... 2.30 um
Field of view ............ 53' 10.7" x 40' 22.0"
Image center ............. RA:  2 22 33.736  Dec: +42 21 03.50 
Image bounds:
   top-left .............. RA:  2 20 09.853  Dec: +42 41 17.75  
   top-right ............. RA:  2 24 59.116  Dec: +42 40 57.89  
   bottom-left ........... RA:  2 20 09.974  Dec: +42 00 56.89  
   bottom-right .......... RA:  2 24 56.196  Dec: +42 00 36.45  

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Rig:
Imaging scope: SW Startravel 150mm F5 Refractor, Baader Diamond Track, (2.5x Celestron Luminos 2inch imaging barlow), Atik 460EX mono

Guide scope: SW Evostar 90mm F10, with guiding XY stage, ZWO 120MM camera

Guiding: 2 stage PHD: high frequency guide scope (mount tracking) and low frequency OAG image train guiding (guidescope flex)

Mount: Home made German Equatorial pillow block mount, permanently rooftop mounted.  Spring loaded DEC axis gearing.

Other gadgets: ST4 based anti vibration shutter, ST4 based PEC

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Processing Lights:
PixInsight: Lights, Darks, Flats, Biases: master dark/dark library-> masterbias-> superbias-> calibrated flats-> master flat-> calibrated lights-> cosmetic correction-> aligned lights-> master light-> BXT

PixInsight: Master BXT lights-> crop-> linfit-> final master lights

PixInsight: final master lights->StarNet2 starless-> RGB Channel Combination (RGHb)-> export xisf starless master.

GradXpert Gradient removal: import starless xisf-> GXPT(20pc,3sg)-> export xisf, fits32 

Affinity Photo 32 bit image processing: import GXPT starless fits32-> accept default stretch-> curves-> lvl(B)-> curves-> paint (cosmetic star haloes)->Topaz Denoise(SN, 14, 0)-> Tpzdn(ST,22,18)-> export tiff16

GradXpert Gradient removal: import tiff16-> GXPT(20pc,3sg)-> export tiff16

Affinity Photo: import tiff16-> curves-> export tiff16

Gigapixel: import tiff16-> 2x upscale high fidelity-> export tiff16

Affinity Photo: import tiff16-> Tpzdn(LL, 0, 38)-> selective colour-> white balance-> brightness /contrast

Affinity Photo final tart ups: paste in star mask layer, blend mode 'screen'

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Processing Star Mask:
PixInsight: final master lights-> RGB Channel Combination (RGHb)-> StarNet2 star mask-> export xisf starmask

GradXpert Gradient removal: import starmask xisf-> GXPT(20pc,3sg)-> export tiff16

Affinity Photo: import tiff16-> curves-> levels(RGB)-> vibrance-> manual white balance-> Gaussian Blur(0.1)> levels-> curves-> brightness /contrast-> manual white balance-> brightness /contrast-> paste Star Mask layer on top of starless final (blend mode 'screen')

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