Celestial hemisphere:  Northern  ·  Constellation: Cygnus (Cyg)  ·  Contains:  Extremely wide field
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Cygnus, Des McMorrow
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Cygnus

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Cygnus, Des McMorrow
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Cygnus

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Description

Go fast or stay home.

This is perhaps the most challenging project I have undertaken.

Living at 54 degrees North means that around mid summer we get at best one hour of Nautical darkness per night and that's it.
In the winter, Yorkshire suffers pretty much from perma drizzle/ relentless rain.

For these reasons fast camera lenses  are appealing but obviously come at a cost of a lot, and I mean a lot, of fettling if one
wants to use an astro camera such as the asi2600 series.

I shoot Canon, and for me the best lenses in terms of price/ performance are the EF mount (mostly readily attachable to zwo cameras)
Sigma Art series, most especially the 28, 40, 85 and 105mm.

I've been messing around with the 40mm f1.4 lens from this series for over a year off and on. It works beautifully with DSLRs and can even be used wide open if one accepts slightly wonky stars in the corner. Trying to tame it with an astro cam, filter wheel/drawer, filter in place is another matter.

By way of a progress report, here is as far as I've got so far. This is with an ASI2600MC Pro attached to a ZWO EOS filter drawer adapter, IDAS NBZ filter, and an 0.8mm spacer to extend the back focus. With this configuration the lens achieves best focus close to the nominal infinity mark - reducing the spacer width moves the focus to progressively shorter distance marks and produces more aberrations. The image was shot at f2, ie closed by one stop. The stars towards the edges are indeed still wonky so further work is required. The central part of the image is pretty sharp. It is worth noting that focus is very tricky to achieve and I am waiting delivery of a sharpstars bahtinov mask which should help. Next stop, wait for Cygnus to move into prime position next month and try shooting at f2.8.





IMG_1268.jpeg

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Cygnus, Des McMorrow