Guest zidder Posted April 15, 2015 Share Posted April 15, 2015 During a session last night ( Tues 14th) I had various targets, my problem is some I got others not. M81 Mag 6.4 - Got M82 Mag 8.41 - Got M51 Mag 8.4 - Not With M51 I think I got it after a fashion, all I saw was two dim points of light Why when I can see M82 properly can I not see M51 other than the cores ? Your wisdom much appreciated Link to comment Share on other sites More sharing options...
Daz Type-R Posted April 15, 2015 Share Posted April 15, 2015 I would say it is 2 things. 1. M81 + M82 are higher, closer to zenith than M51 is, so you will be looking through less atmosphere, so the view should be better (depending on seeing, jet stream ETC). 2. M51 is face on to us, so its light is spread over a wider FOV, where M81 + M82 are more edge on than M51, so their light is not spread out as much. The trouble with mag (I believe) is that it is a scale of magnitude with every thing else being equal, so it does not take into account how the object is placed ETC. Link to comment Share on other sites More sharing options...
+Ibbo Posted April 15, 2015 Share Posted April 15, 2015 as Daz says its an integrated mag-ie what it would be if it was a single point Link to comment Share on other sites More sharing options...
Guest zidder Posted April 15, 2015 Share Posted April 15, 2015 Thanks guys , so if you cant use Mag as a reference what do you use to ascertain what will be visible ? Link to comment Share on other sites More sharing options...
+Ibbo Posted April 15, 2015 Share Posted April 15, 2015 use a book like turn left at orion and keep trying more you look the more you will get your eye in Link to comment Share on other sites More sharing options...
Daz Type-R Posted April 15, 2015 Share Posted April 15, 2015 Experience. I do use the mag as a guide but also try and factor in how close to zenith the object is and how good the seeing conditions are. Then just give it a go, if you cant see it, try later. Link to comment Share on other sites More sharing options...
Doc Posted April 15, 2015 Share Posted April 15, 2015 It's experience really. The more objects you look for and find or not find, you will learn what your limiting magnitude is. Link to comment Share on other sites More sharing options...
Werisit Posted April 15, 2015 Share Posted April 15, 2015 Yep, M51 is much harder to see but the fact that you say it was 2 points of light means you did see it. It's 2 interacting galaxies. If you're looking at M 31, look out for 32 and 110 also. 32 is bright and looks like a fuzzy star where as 110 is faint and difficult in light polluted skies. Their mag's are about the same but the light is spread over a much larger area in 110. Link to comment Share on other sites More sharing options...
BAZ Posted April 16, 2015 Share Posted April 16, 2015 (edited) Looking for anything straight up with a Dob is neigh on impossible. You will have more luck when it's not so close to 90 degrees straight up. As already mentioned, the stated magnitude is a bit misleading, it considers all the light being emitted from an object, but if this is spread out over a larger area, such as M33, it is quite difficult to find. Compare M101 and M82, M101 is Mag 7.8, while M82 is Mag 8.4. M101 is face on and fairly large, while M82 is more edge on and more compact, so the light coming from M101 is diffuse, and that from M82 is much more compact. Even though M82 is getting on a magnitude dimmer, it's a lot easier to find than M101. Edited April 16, 2015 by BAZ Rubbish spelling. Link to comment Share on other sites More sharing options...
Guest zidder Posted April 16, 2015 Share Posted April 16, 2015 use a book like turn left at orion and keep trying more you look the more you will get your eye in I am Steve Link to comment Share on other sites More sharing options...
Werisit Posted April 16, 2015 Share Posted April 16, 2015 How bad is your light pollution Gary? Link to comment Share on other sites More sharing options...
Guest zidder Posted April 17, 2015 Share Posted April 17, 2015 How bad is your light pollution Gary? I don't know how to answer that in terms of an index score, But it is not brilliant I live in the middle of an estate on the edge of Nottingham Link to comment Share on other sites More sharing options...
Tweedledee Posted April 17, 2015 Share Posted April 17, 2015 I don't know how to answer that in terms of an index score, But it is not brilliant I live in the middle of an estate on the edge of Nottingham In that case, I reckon you did pretty well. And you did actually see all three, even though M51 was not very inspiring Link to comment Share on other sites More sharing options...
Werisit Posted April 17, 2015 Share Posted April 17, 2015 Yep, you did well to see what you did. LP raises the brightness of the background sky so much that the faint galaxies get drowned out. Get your Dob out under a dark sky and it'd be a different story. I recon I can see more from Milton Keynes with my 130 frac than with my 10" Dob. Link to comment Share on other sites More sharing options...
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