Rosliston Astronomy Group


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DSOs from the West Country

Roger Samwroth



It is not spectacularly dark here, but darker here than in the Midlands.

Last night was clear but a bit hazy. Good enough to have a go with the 80mm & PD though.

Not much time available, so I just imaged 3 old favourites, and the results are attached. I liked M33 in particular as because of its size is always awkward with the PD. The main problem with the PD and M33 is M33's size, hence having to use a focal reducer on a scope that already has a focal length of only 400mm.

Processing M33 wasn't that difficult, although it is probably like riding a bike - easy when you can do it! The bulk of it uses "curves" to stretch the contrast as in the document on M51 I did. The "gamma" function in Registax is a simpler version if GIMP's curves.

M33 has an angular extent of 70X42 min or so. A FL of 500mm gives a diagonal FOV of 42min with the PD, so it is pushing it a bit to get most of it in. A X0.5 reducer will give you a FOV of 84min, which is much better. More importantly it will also give you 2 stops speed improvement to f/3.1-ish which is quite fast. My 80mm is f/5, so I get f/2.5 with the reducer.

Home tomorrow!


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