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Size of DSOs


dawson
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Is there a list somewhere of the various DSOs (Messier objects etc) listed against their size in terms of degrees/arc minutes they appear in the sky?


 


I ask as I'm thinking about the next OTA and while I love the slower scopes for their planetary and lunar (and solar) stuff, ir would be nice to pick something which could also be used for lots of the smaller DSOs.


 


Thanks for any replies.


 


James


 


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All the info on the Messier objects is here: http://www.amazon.com/Observing-Messier-Objects-Small-Telescope/dp/0387853561/ref=la_B0034NTCJK_1_3?ie=UTF8&qid=1367395384&sr=1-3


 


I saw all of them in a 127mm Mak but it was hard going and only about a quarter of them were memorable. The larger ones are best in binoculars.


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All the info on the Messier objects is here: http://www.amazon.com/Observing-Messier-Objects-Small-Telescope/dp/0387853561/ref=la_B0034NTCJK_1_3?ie=UTF8&qid=1367395384&sr=1-3

I saw all of them in a 127mm Mak but it was hard going and only about a quarter of them were memorable. The larger ones are best in binoculars.

Ha ha! Shameless plug there phil! Is that not your book in the link? ;)

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I've made my own rough and ready list in Excel using the links above (thank you).


 


Of the Messier objects:


 


49 of them are < 10 arcminutes,


69 are < 15 arcminutes,


79 are < 20 arcminutes,


93 are < 30 arcminutes,


102 are < 40 arcminutes,


108 are < 100 arcminutes;


M45 is 110 arcminutes;


M31 is 179 arcminutes.


 


I'd always assumed (and we all know what 'assumed' did) the majority were MASSIVE; and I know the Messier list in't the whole DSO list but it's a rough guide for me to be getting on with.


 


FOV for my current 127mm Mak-Cassegrain with various Meade 4000 Super Plossl EPs (in mm), and for the 180mm Mak-Cassegrain are:


 


56mm EP, 116 arcminutes for 127mm Mak; 64 arcminutes for the 180mm Mak


40mm EP, 70'; 39'


32mm EP, 66'; 36'


26mm EP, 54'; 30'


20mm EP, 41'; 23'


12.4mm EP, 26'; 14'


9.7mm EP, 20'; 11'


 


So a 20mm EP in the 127mm Mak would allow one to "see" 102 of the Messier objects, the same could be "seen" using a 40mm EP in the 180mm Mak.


 


Not that any of this is useful to you lot, but it's just my workings out / thought processes.


 


Thanks again.


 


James


 


(excuse any errors in calulations)


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James - just do what everyone else does - buy two scopes - you've got a dual capacity alt/az & eq in one mount there - you need to do it justice lol :)


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It's a good idea you've calculated the FOV for the various eye pieces.  I used to use Norton's star atlas for size but I still found difficulty in knowing how big or small the object was I was looking for - was the object the size of a star or two, or a lot more massive, how many of the objects would fill the field diameter etc.


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