2017 Refocusing
Aims for 2017 were to use New Moon dark sky opportunities at Perth Observatory or elsewhere to try some wide-field milky way shots as well as more faint nebulous objects.
I continued to have hopes, not progressed in the last 3 years, to try some mosaics and some HDR images in order to challenge me to improve my Photoshop skills and possibly even have a look at PixInsight, that is now an an entrenched Astrophotography software toolkit item. I did managed to experiment with EQMOSAIC for mosaic navigation and Microsoft Image Composite Editor (ICE) early in the year. No HDR and a Pixinsight trial expired before I could trial it :(
I continued my involvement with Perth Observatory's Volunteer Group (POVG) for Perth Observatory's public outreach programmes including coordinating the 4-person private 'star adoption' tours and involved in the Training of new volunteers with reference material and hands on training for equipment.
Unless stated otherwise, images are from my home location in Willetton, 12 Km south of the centre of Perth, Western Australia, though I used this far less now as it is unsuitable for faint objects using one-shot colour DSLR.
My favourite shots can also be found on AstroBin http://www.astrobin.com/users/scottastrophe
Bahtinov Focusing 50mm f/1.8 vs f/3.5 - 25/4/2017
I have been using Bahtinov masks with Refractor and Newtonian telescopes since 2010 and recently purchased ones suitable for my DSLR camera lenses (52mm, 72mm and 77m filter size). I tested the 52mm with my Canon EF f/1.8 lens at f/1.8 and f/3.5 to see both how effective it was and also whether it helped find a sweet-spot between focal ratio and lens edge distortion.
Look at the image in maximum resolution to see my assessment:
At f/1.8 the off-axis stars have noticeably different focus positions and must contribute to the lens flare at the edges when using this lens at its unstopped position.
At f/3.5 the off-axis stars are much more stable across the frame and seems to be the sweet-spot for this lens with balance of reasonable focus and not too slow.
Canon 50mm f/1.8 EF Lens on Baader BCF modified Canon 70D DSLR field ~17 x 25 degrees, Ambient 15C. SkyWatcher Star Adenturer EQ mount, unguided on sidereal rate.
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Kim McAvoy
on January 27, 2017Great shots so far!