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Sh2-101, Tulip Nebula, HαRHαRGB, 26 May & 12 Jun 2018, 


            David Dearden
Sh2-101, Tulip Nebula, HαRHαRGB, 26 May & 12 Jun 2018

Sh2-101, Tulip Nebula, HαRHαRGB, 26 May & 12 Jun 2018

Technical card

Resolution: 2258x1707

Dates:May 26, 2018June 12, 2018

ZWO Blue 31 mm: 20x180" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 20x180" (gain: 139.00) -20C bin 1x1
ZWO H-alpha 7nm: 58x300" (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 20x180" (gain: 139.00) -20C bin 1x1

Integration: 7.8 hours

Avg. Moon age: 19.91 days

Avg. Moon phase: 46.51% job: 2099144

RA center: 300.097 degrees

DEC center: 35.316 degrees

Pixel scale: 1.719 arcsec/pixel

Orientation: 86.111 degrees

Field radius: 0.676 degrees

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

Data source: Backyard


Starting on a night with a lot of moonlight and after finishing with another target, I began acquiring Hα for the Tulip Nebula. I finally got an absolutely beautiful, dark night to get the RGB and more Hα, with this result. I combined starless Hα with the R channel to produce an enhanced R channel, and used Hα combined with a greyscale version of the RGB as luminance. I thought I might have captured the companion star of Cygnus X-1, the famous black hole, but it turns out that is just off the top of this frame. I opted for a lot of saturation in this image, because the star field here is very pretty.

Date: 26 May, 12 Jun 2018
Subject: Sh2-101, Tulip Nebula
Scope: AT8IN+High Point Scientific Coma Corrector
Filters: ZWO 31 mm diameter unmounted Hα, R, G, B
Mount: EQ-6 (EQMOD 2.000j)+PEC
Guiding: Orion Thin Off-axis Guider + DSI Ic +PHD 2.6.5 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro
Exposure: 58x300 Hα, 20x300 R, G, & B
Stacking: Deep Sky Stacker 4.1.1 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.
Processing: StarTools 1.4.332: Combined R, G, and B in StarTools. Binned 2x2, cropped, wiped, developed, HDR. No deconvolution. Turned off tracking to smooth fairly agressively. Binned Hα 2x2, cropped, wiped, and used Autodev followed by HDR. Masked out the “fat” stars and used light deconvolution followed by untrack smoothing. Healed out the stars to produce a starless version. Combined this (after some smoothing and levels to darken the background) with the R channel from the RGB and used the result as the new R channel. Combined the full Hα (after some smoothing) 50% with a greyscale version of the RGB to form a luminance layer. Used curves to back off the resulting L a little, and enhanced the RGB a little. Some layer masked Unsharp Mask to bring out a bit more detail in the nebula. Played with Vibrance, Saturation, and Levels to get the colors where I liked them. AstroFrame.



David Dearden
License: None (All rights reserved)

Sky plot

Sky plot


Sh2-101, Tulip Nebula, HαRHαRGB, 26 May & 12 Jun 2018, 


            David Dearden