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NGC 4236, Spiral Galaxy in Draco, OSC (UHC-S), 2-3 Apr 2016

Contains: NGC 4236

Technical card

Resolution: 799x604

Dates: April 3, 2016

Frames: 33x600"

Integration: 5.5 hours

Avg. Moon age: 24.51 days

Avg. Moon phase: 25.91% job: 1025692

RA center: 184.075 degrees

DEC center: 69.482 degrees

Pixel scale: 2.124 arcsec/pixel

Orientation: -87.200 degrees

Field radius: 0.296 degrees

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


This was a first-time observation of NGC4236, which is quite dim but of good size for my optics. This galaxy is not so frequently imaged, perhaps because it is so dim and because it is hard to make out a lot of internal structure. This was also my first opportunity to try my fix for the Sequence Generator Pro plate solving problems I've had for the last month. (The problems don't really belong to SGP; they belong to me!) It turns out all I needed to do was correctly set the aspect ratio parameter for PlateSolve2 to account for the non-square pixels in my DSI IIc imaging camera. I did numerous successful plate solves during this session. Actually I did too many, because the other problem that has plagued me recently, image download failure, was quite evident during this session. It happened with the guider quite a few times as I set up and the session did eventually fail due to a main image download failure. I suspect the fix for that will be a more capable powered USB hub than the cheap ones I've been using. Anyway, plate solving now works great and I also did a successful unattended meridian flip.

Date: 2-3 Apr 2016
Subject: NGC 4236, spiral galaxy in Draco
Scope: AT8IN
Filter: Baader Planetarium UHC-S
Mount: EQ-6 (EQMOD)
Guiding: Orion ST-80 + Antares 0.5x focal reducer + DSI Ic + PHD (Win 7 ASCOM)
Camera: DSI IIc, no chiller CCD 10 °C
Acquisition: Sequence Generator Pro with Nebulosity 4.0.4 ASCOM camera driver
Exposure: 33x600 s
Stacking: Neb 4, bad pixel map, bias included, 33 flats, match histograms, trans+rot align, Deep Sky Stacker 1.5σ κ-σ stack without drizzle.
Processing: StarTools 1.4.305: Crop; Wipe; Develop: 85.00%; HDR:Optimize; Color:Scientific, 277% saturation, red bias reduce at 1.19; Deconvolute: 2.8 pix; Life:Moderate; Track: Smoothness 87%, 6.0 pix; Magic, shrink 2 pix. Photoshop CS6 + Astronomy Tools: Deep space noise reduction; Increase star color; curves; layer-masked levels to kill gradient; Astroframe.



David Dearden

Sky plot

Sky plot


NGC 4236, Spiral Galaxy in Draco, OSC (UHC-S), 2-3 Apr 2016, David Dearden