31 January 2015

Wide-Field Observing

I recently posted an observing plan to the Deep-Sky Planner Plan Library  containing most of the objects that appear in the "Wide-Field Wonders" article in the 2013 RASC Observer's Handbook. (The article also appears in the 2015 edition.) While most of the objects are nebulae and clusters, a few are more esoteric objects that aren't found in typical catalogs - things like molecular clouds. This plan contains an excellent variety of imaging and viewing targets, so I encourage readers to check out the article to get background information.

Observer's Handbook from
Royal Astronomical Society Canada

Wide-field observing (both visual and imaging) generally requires a rich-field telescope, binoculars, or a fairly fast telescope with a long focal length eyepiece. These objects often have low surface brightness, so a dark location is definitely indicated.

Wide-field observing can be a nice change of pace if your usual deep-sky observing includes galaxies, planetary nebulae and such. For example, I've observed the Veil Nebula in Cygnus dozens of times with various telescopes. I always enjoy viewing it with a UHC filter and magnification around 100x. The telescope I use most often these days is a 14.5" f/4.5 reflector. My rather ancient 20mm Nagler eyepiece produces magnification of 96x with a field of view of about .86° with this telescope. I've used this combination of equipment for several years, so the end result is somewhat expected.

14.5" f/4.5 Reflector

I got a new lower power eyepiece a year or so ago that was a game-changer on things like the Veil. The new eyepiece is a 31mm Nagler which produces 61x with FoV of 1.3°. It turns out that the view with the 31mm eyepiece allows me to see most of the nebula at once. The view with the 20mm requires a lot of scanning around to view the entire nebula. While the detail is much greater with the 96x view, the ability to 'get it all' at 61x is a welcome new capability. I've also observed the Veil through a friend's Tele Vue-NP101 (101mm, f/5.4) with a 31mm Nagler. The view was stunning and quite different from my usual result. That view really inspired the purchase of the 31mm eyepiece.

TeleVue's 31mm Nagler

From this I think it is fair to suggest that we get into familiar patterns with our observing - both imaging and visual. A simple change like using a different eyepiece can produce a very different view, even with an object that is very familiar. Perhaps we should take the next step with this by pursuing an observing plan that includes objects well off of our beaten path. The "Wide-Field Wonders" plan may be such a refreshing change of fare.

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