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| Beginners Corner Just starting out and need some help? |
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#1
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| Finally after three winters...... Last night for the first time ever, I clapped eyes on the Crab Nebula. Here's how I found it. Lookine at the Sky & Telescope Pocket Star Atlas, I notices that there was a little three star asterism just to the north of Zeta Tauri shaped like a (right isoceles) triangular hat for Zeta Tauri, The chart showed M1 just to the west of the star at the tip of the "hat." Centered the fov on this star at 26X, then moved up to 110X and was just able to see a very ghostly patch where M1 was supposed to be. My edition of Telescope Handbook and Star Atlas has this to say about M1: "Perhaps less spectacular [than M42] but of great historical interest because it was the first object in the Messier list, the Crab Nebula in Taurus will help liven your chilly observing session." All I know is that I've spent a good part of many chilly sessions over the last two years looking for it and finding it was a picker upper. One question I have is this. The magnitude listing for this in my chart is 8 vs 9 for M57, 8 for M56, 10 & 9 for M65 and M66, 8 & 9 for M81 & M82, 9 for M104, and 10 for NGC1907. All of these were easier to spot and yielded more to prolonged observation than the Crab Nebula. I wonder why... OBTW, the scope was a souped up and tuned Burgess 102mm achromatic refractor. Take care, Mark Costello Matthews, NC Last edited by markvcostello3; 01-20-2007 at 10:12 PM. Reason: Correct typos... |
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#2
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| Mark, You have discovered a very common problem for deep sky observers. It is one that frustrates many folks, not just the newcomers. The magnitudes you listed for the other objects, which were easier to find, illustrate that very problem. I'll try to explain: Magnitudes for deep space objects such as galaxies, Nebulae, Star Clusters etc. are listed as if all the light from these objects were coming from a point source such as a star. So, if you squeezed M1's light into a single point, it would indeed be very easy to find. But it is NOT a point source. It's light is spread out over a good sized area, thus making each part of the area much dimmer than it appears. When trying to find deep space objects, look at the size of the Object vs. the brightness listed. For an easy comparison, remember that the Moon is about 30' in size ( 1/2 degree). There are free planetarium programs on the web that will list the size and magnitudes of these objects to help with this. " Hello Northern Sky" is one of the popular ones. Just enter your location and it will show you what the sky looks like from your House any time, any date. You can even print out the charts to take with you to your scope. The proper measure for extended Deep Space objects is "Surface Magnitude" which is almost never listed in the most common catalogs and charts. But it explains why M51 is easy to spot while M33 is a bear to find. So, when you go looking for the faint fuzzies, look at both the size and the magnitude. It will give you an idea what it should look like in a Telescope. The most blatant example is M31. Easy to find right ? Yes, and no.! All most folks ever see is the central core of the galaxy which is nothing more than a fuzzy blob and disappointing to most folks because it is too far away to resolve into individual stars. The rest of the galaxy is way too big to fit in the field of view of most Telescopes. ( it is over 4 degrees across, hold your fist at arms length against the sky to get an idea how big it really is) The spiral arms are so spread out that, even though the galaxy's magnitude is listed as a little over 3, the arms are almost invisible to most telescopes. I hope this helps. Adolph
__________________ The most Uncommon thing in the Universe is common sense ! |
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