Contains: Sombrero galaxy, M 104, NGC 4594
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M104, Sombrero Galaxy, MyFocuser Pro 1st Light, OSC (UHC-S), 3-4 May 2016

Technical card

Resolution: 786x650

Dates: May 4, 2016

Frames: 18x600"

Integration: 3.0 hours

Avg. Moon age: 26.84 days

Avg. Moon phase: 7.95% job: 1063917

RA center: 189.977 degrees

DEC center: -11.632 degrees

Pixel scale: 1.865 arcsec/pixel

Orientation: -177.073 degrees

Field radius: 0.264 degrees

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


This was a first use of my new MyFocuserPro digital stepper motor-based focuser. It performed quite well and positioning looks to be very reproducible. Unfortunately, the focusing algorithm in Sequence Generator Pro wasn't up to the task for automatic focusing, but I understand this is a known issue (problems with scopes that have a central obstruction, like my Newtonian) that has been addressed in the 2.5.1 beta, so I downloaded that and will try it next time I'm on the sky. Otherwise, it was also a night of multiple mess-ups. I guess I was just too excited about using the new focuser, or maybe senility is creeping in. I started my session and the goto wasn't very good because I'd forgotten to lock the clutch on the Dec axis. So I fixed that and found Arcturus and dialed in the focuser. Then I did a goto to the Sombrero and again I was a little bit off, but close enough. After finding I couldn't make autofocus work very well, I went ahead and started my session and the guiding was pretty good. I got to the meridian flip and it failed! The mount simply failed to flip. I looked outside and saw the counterweight shaft sticking right up at the meridian. I had forgotten to install the counterweights! I'm amazed that I was able to do anything under those conditions; I guess I was just lucky about where the Sombrero Galaxy was in the sky relative to the balance point of my mount. So I installed the counterweights, re-parked and re-set the mount, and continued. Unfortunately, last night was one where focus did degrade as time went on, so I threw out some subs. The resulting image is perhaps not as good as my 2013 image (and maybe I should add in the 2013 data to improve it).

B revision: darkened the background!

Date: 3-4 May 2016
Subject: M104, Sombrero Galaxy
Scope: AT8IN+High Point Scientific Coma Corrector
Filter: Baader Planetarium UHC-S
Mount: EQ-6 (EQMOD)+AutoPEC
Guiding: Orion ST-80 + Antares 0.5x focal reducer + DSI Ic + PHD (Win 7 ASCOM)
Camera: DSI IIc, no chiller CCD 15 °C
Acquisition: Sequence Generator Pro with Nebulosity 4.1 ASCOM camera driver
Exposure: 18x600 s
Stacking: Neb 4, bad pixel map, bias included, 33 flats, nebula filter, match histograms, trans+rot align, Deep Sky Stacker 1.5σ κ-σ stack without drizzle.
Processing: StarTools 1.4.316: Crop; Wipe; Develop: 85.77%; HDR:Optimize; Contrast; Color:Scientific, 200% saturation, red bias reduce 1.70; Deconvolute: 2.5 pix; Track: Smoothness 87%, 4.5 pix; Magic, shrink 2 pix. Photoshop CS6 + Astronomy Tools: Deep space noise reduction; Increase star color; layer masked unsharp mask for dust lane; Astroframe.



David Dearden

Sky plot

Sky plot


M104, Sombrero Galaxy, MyFocuser Pro 1st Light, OSC (UHC-S), 3-4 May 2016, 


        David Dearden