I managed to get an interesting result using a combination of a Samyang 16\2.0 ED wide-angle lens and an Optolong L-eNhance clip EOS filter. Despite the fact that the lens is announced only for crop cameras, it lacks the “tail” characteristic of EF-S lenses and prevents the installation of astronomical clip-filters (between the lens and the camera). Also, there are no problems with shifting the bandwidth at the edges of the frame. However, another problem appeared – elongated stars and lateral chromatic aberration. This may be due to the fact that when using the clip filter, the focus point is shifted and additional refocusing of the lens is required, while the lens provides minimal aberrations when set to infinity without a filter (a feature of lenses with internal focusing). I plan to add a thin ring between the bayonet ring on the photo lens and the body of the photo lens – this should compensate for the shift in focus and improve the view of the stars across the field.
I managed to shoot the Seagull nebula in the constellation Monoceros 5 times. Literally before the shooting, the weather deteriorated and the whole sky was overcast with clouds. Several trips out of town were wasted because of the clouds. On February 5, 2019, the weather still took pity on me and was able to fully capture this interesting area of ionized hydrogen. Below and to the left of it is the Thor’s Helmet nebula in the constellation Canis Major, which got its name for its resemblance to the winged helmet of the Scandinavian thunder god. The departure was very successful, there were only a few clouds at the very beginning, while I set up the autoguider and searched for the nebula. There was wind, but the rocks were well protected from the it.
-Samyang 135\2.0 ED Canon EF lens
-camera Canon 550Da
-filter Svbony CLS clip EOS-C
-mount Sky-Watcher Adventurer
-autoguider: finderscope Sky-Watcher 50 mm + camera ZWO 290 MC.
35 frames per 120 s, ISO 1600.
Calibration with PIPP, stacking with Fitswork.
Scale 25%. Link — at scale 100%.
Location: village Supsekh, Kuban, Russian Federation.
There were great difficulties due to red halos – the result of using a CLS filter with a modified Canon 550Da camera. When shooting without a CLS filter, they practically do not interfere, but due to the noticeable light pollution, I still had to use this accessory. The filter does not transmit light between the red and green ranges of the spectrum, which leads to a choice in focusing – either in the red channel or in the green. It is possible that using a more advanced L-Pro type filter will improve the situation. A compromise is possible – focusing between the red and green channels, but this will lead to a decrease in resolution. Perhaps next time I will try this kind of focus. The problem itself lies in the photo-lens – undematured chromatism and spherical aberration in the red channel.
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Finally completed the processing of one of the Orion shooting sessions. Perhaps, from the tenth approach we managed to get a more or less satisfactory result and pull out many faint nebulae. The filming took place in the city, and I used the Svbony CLS clip filter to suppress flare.
-Samyang 135\2.0 ED Canon EF
–Svbony CLS clip EOS-C
-mount Sky-Watcher Adventurer
38 frames per 120s, ISO 400.
Calibration and stacking at DeepSkyStacker.
Scale: 25%. At links – in scale 50% и 100%.
Place: Russia, Anapa, backyard.
Image without filter and with filter: Читать далее (Read more) > > >