Hemisphere:  Southern  ·  Constellation: Eridanus (Eri)  ·  Contains:  19 bet Ori  ·  62 b Eri  ·  63 Eri  ·  65 psi Eri  ·  66 Eri  ·  67 bet Eri  ·  68 Eri  ·  69 lam Eri  ·  Cursa  ·  IC 2118  ·  IC2118  ·  IC398  ·  IC399  ·  NGC1694  ·  NGC1699  ·  NGC1700  ·  NGC1720  ·  NGC1726  ·  NGC1741  ·  NGC1752  ·  NGC1779  ·  NGC1797  ·  NGC1799  ·  Part of the constellation Eridanus (Eri)  ·  Rigel  ·  The star 62Eri  ·  The star 63Eri  ·  The star 66Eri  ·  The star 68Eri  ·  The star Cursa (βEri)  ·  And 4 more.
Getting plate-solving status, please wait...
IC 2118, Witch Head Nebula, LRGB, Dec 2017, 



    
        

            David Dearden
Powered byPixInsight

IC 2118, Witch Head Nebula, LRGB, Dec 2017

Getting plate-solving status, please wait...
IC 2118, Witch Head Nebula, LRGB, Dec 2017, 



    
        

            David Dearden
Powered byPixInsight

IC 2118, Witch Head Nebula, LRGB, Dec 2017

Imaging telescopes or lenses: Tamron Adaptall 135mm F2.8

Imaging cameras: ZWO ASI1600MM-Cool

Mounts: Skywatcher NEQ-6 Pro Synscan

Guiding telescopes or lenses: Orion 9x50 finder

Guiding cameras: Meade DSI II C

Software: Enterprise Astronomy Annie's Astro Actions  ·  photoshop  ·  RC Astro GradientXTerminator  ·  Silicon Fields StarTools 1.3  ·  Noel Carboni's Astro Tools for PhotoShop  ·  AstroPlanner  ·  PHD2 Guiding  ·  Sequence Generator Pro  ·  Nebulosity  ·  EQASCOM

Filters: ZWO Red 31 mm  ·  ZWO Luminance 31 mm  ·  ZWO Green 31 mm  ·  ZWO Blue 31 mm

Accessory: Robert Brown's Arduino ASCOM Focuser Pro DIY  ·  ZWO EFW filter wheel


Dates:Dec. 12, 2017Dec. 14, 2017Dec. 15, 2017Dec. 22, 2017

Frames:
ZWO Blue 31 mm: 31x180" (1h 33') (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 24x180" (1h 12') (gain: 139.00) -20C bin 1x1
ZWO Luminance 31 mm: 98x180" (4h 54') (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 41x180" (2h 3') (gain: 139.00) -20C bin 1x1

Integration: 9h 42'

Avg. Moon age: 20.30 days

Avg. Moon phase: 15.73%


Astrometry.net job: 1868701

RA center: 5h 5' 19"

DEC center: -6° 59' 51"

Pixel scale: 5.942 arcsec/pixel

Orientation: -88.028 degrees

Field radius: 4.385 degrees


Resolution: 4252x3186

Locations: Mapleton Lateral Observatory, Mapleton, Utah, United States

Description

This has been a very difficult object for me. Probably I need darker skies than I have here in Mapleton (I tried 300 s luminance subs, had way too much sky glow, cut it back to 180 s, and still had quite a bit), and I just seem to have a more difficult time with LRGB these days than with narrowband (Narrowband is truly magic!). This kind of faint reflection nebula also seems to be the most difficult type of target for me. Then to make this even more difficult, leaving a star as bright as Rigel in the field of view presented all kinds of challenges, but I wanted it there because I understand Rigel is thought to light up the nebula. Finally, the Tamron lens does seem to perform less well with the blue filter for some reason, requiring a lot of star shrinking in the blue channel to avoid nasty rings around the stars. I’m still struggling a little to get good flats, though my L and R flats weren’t too bad this time (I think I’m probably exposing them too much so they overcorrect). Gradient Xterminator was a huge help, along with Carboni’s Soft Color Gradient Removal action. Of interest to me were the satellite trails that appeared in nearly every subframe; two parallel trails that appear and disappear as if the satellite is slowly tumbling. I’m guessing these must be geosynchronous or at very least in high, nearly equatorial orbits. They appeared frequently enough in the same places that sigma-clip stacking did not eliminate them, and I left them in (running vertically through the Witch’s chin) because they really were in that part of the sky.

Date: 12-15, 22 Dec 2017

Subject: IC 2118, Witch Head Nebula

Scope: Tamron 135 mm f/2.8 lens stopped to f/4

Filters: ZWO 31 mm diameter unmounted L, R, G, B

Mount: EQ-6 (EQMOD 2.000j)+PEC

Guiding: Orion 9x50 Finder/Guider + DSI IIc +PHD 2.6.4.5 (Win 10 ASCOM) using predictive PEC algorithm

Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21

Acquisition: Sequence Generator Pro 3.0.0.4

Exposure: 98x180 L, 41x180 R, 24x180 G, 31x180 B

Stacking: Neb 4.1.6, darks + flats, trans+rot align, Nebulosity 1.5σ stack and align.

Processing: StarTools 1.4.328: Used StarTools’ “Wipe” module to correct for gradients the flats didn’t get, then stretched each channel separately in StarTools. Deconvoluted the L channel. Aligned the processed layers in Nebulosity then combined in Photoshop using Annie’s Astro Actions’ LRGB module. Stretched some more in Photoshop using Curves and Levels. Gradient Xterminator + Carboni’s Soft Color Gradient Removal, combined with several rounds of Carboni’s Make Stars Smaller, then Deep Space and Space Noise Reduction. AstroFrame.

Comments

Revisions

  • IC 2118, Witch Head Nebula, LRGB, Dec 2017, 



    
        

            David Dearden
    Original
  • Final
    IC 2118, Witch Head Nebula, LRGB, Dec 2017, 



    
        

            David Dearden
    B

B

Description: Boosted the saturation a little.

Uploaded: ...

Sky plot

Sky plot

Histogram

IC 2118, Witch Head Nebula, LRGB, Dec 2017, 



    
        

            David Dearden