Messier 51 – Whirlpool Galaxy

Shot through massive light pollution over staggeringly huge The Village At Fairview outdoor mall complex.

This started as an add-on session to my first attempt at narrowband imaging and turned out much better than I hoped for.  Of course this would be much more grand out in the country but that’s not what this site is really about.  It’s more focused on what I can accomplish from my back yard.


Messier 51 – The Whirlpool Galaxy

Depending on who did the study and when, estimates for distance vary widely from 15 million light years to 35 million light years.  These two galaxies are gravitationally interacting which is a highly science nerdy way of saying “crashing into each other)”.  Galactic collisions aren’t collisions at all, really.   There’s so much empty space between stars in the systems that it is highly unlikely that any of the stars in either galaxy will actually collide.  The law of averages says that some will but the percentage is beyond miniscule.

52 images of 5 minutes each.

Telescope: Celestron EdgeHD 8″ + 0.7x Focal Reducer
Camera: QHY 8L Cooled CCD @ -15C
Mount: iOptron CEM60

Getting on the Narrowband wagon – Horsehead Nebula

Barnard 33 – The Horsehead Nebula in Orion

If you find Orion’s belt, the eastern most star is Alnitak.  Just a bit South and West from that star is this region, cataloged by Edward Emerson Barnard in 1919 in his book of dark nebulae.  This cloud of dust is #33 on his list so we refer to it as Barnard 33.  Colloquially we know this as the Horsehead Nebula thanks to its shape reminding most people of the western world of our equine companions.

Light pollution being what it is and with LED lighting becoming more commonplace, I’m now beginning to feel that only narrowband imaging will be practical from the back yard.  Narrowband images look at very specific frequencies of light.  Not just Red, Green or Blue.  Narrowband typically focuses on frequencies emitted by Hydrogen, Oxygen and Sulphur.  The first ionization of Hydrogen (H-alpha), the third ionization of Oxygen (O-III), and the second ionization of Sulphur (S-II).  Why the change in nomenclature?  No idea, ask the smart guys that came up with the “standard” some time after the discovery of ionization states by Dmitri Mendeleev in 1869.

This image was taken in worst possible case scenarios.  Not intentionally but I did know what I was getting into.   I’m filtering at least 99% of all light by looking at a very narrow band of frequencies around 656nm wavelength +/- 3.5nm.  My filter has a 7nm bandpass, thus the +/- 3.5nm metric.  This frequency of light is specific to Hydrogen-Alpha (H-a) and pretty much nothing else.  Exposure times for light that tightly filtered is ridiculously long.  Each of the 52 frames used to composite this image are 10 minutes long.  That’s 8.6 hours which had to be done over three nights.  I must wait for the sun to be well and fully down and not influencing the sky so I was trying to get started at 8:00pm.  That never happened, mechanical things being finicky always slows down the start up process.  Barnard 33 disappeared behind our roof at about 1:00am.  On the best nights I got started by 9:00pm so I could get no more than 3-4 hours per night if everything went to plan.  Plans being what they are, that was never followed.

Filter: Baader Planetarium 7nm Hydrogen-Alpha
Camera: QHY8L binned down 2×2
Telescope: Celestron EdgeHD 8″ + 0.7x Focal Reducer
Guide Scope: Orion Mini Guider Deluxe
Guide Camera: ZWO ASI120MM-S
Exposure: 52 x 10 minutes