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M-109

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#1 ladip63

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Posted 18 March 2010 - 10:45 AM

This was a hard one. I couldn't see it unless I used averted vision. Even then it kept popping in-n-out. I had to take a few seconds and rest my eye in between looking and sketching.

Lynn

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#2 blb

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Posted 18 March 2010 - 12:02 PM

This is a nice sketch and looks very similar to the way I see it in town. Good work!

Noticed that you put a ? for FOV. Using the formula True field-of-view = Apparent field-of-view/Magnification. Since most Plossel eyepieces have an apparent field of view of 50 degrees, that gives a true field-of-view of approximately 0.53 degrees or 00 degrees 31 minutes 55 seconds. Of course this is approximate and using the drift time to calculate the TFOV is more accurate.

Keep up the good work.

Buddy

#3 S1mas

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Posted 18 March 2010 - 12:11 PM

Very nice Lynn :)

#4 ladip63

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Posted 18 March 2010 - 12:18 PM

Thanks Buddy and S1mas,
Buddy I couldn't find the Apparent field of view for that eyepiece. So how can I find out. In my telescope manual it says that it comes from the EP manufacture and they don't make that EP any more. Would it be OK to use the one you said? 50 degrees.
Thanks
Lynn

#5 frank5817

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Posted 18 March 2010 - 01:08 PM

Lynn,

Very nice capture. :bow: That galaxy is a tough one for me at home because the skyglow is ofter brighter than the galaxy.
Anyway you did a great job with averted vision. :rainbow:

Frank :)

#6 ladip63

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Posted 18 March 2010 - 02:18 PM

Thanks Frank :D

Lynn

#7 blb

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Posted 18 March 2010 - 02:46 PM

Most Plossel eyepieces have an apparent field-of-view between 45 and 55 deg. My Sirius Plossel eyepieces have an apparent FOV of 52 deg. Using 50 deg. just gives you an approximate field size. If you like you can calculate it by using the drift time calculation. This is a rather simple measurement. Pick a star near the celestial equator, such as Delta Orionis or Zeta Verginis and place just outside the FOV where they will pass through the center of the FOV. Start timing when the star enters the eyepiece and stop timing when the star exits the eyepiece. The time obtained for transit will be in minutes and seconds. Convert the seconds to decimal part of a minute by dividing by 60. You now have the time in minutes and decimal parts of a minute.

It takes a star near the celestial equator approximately four minutes to drift west one arc-degree, or one quarter degree each minute. Now you can multiply your drift time buy 0.25 to get the true FOV in degrees. This can be multiplied by 60 to get your true FOV in arc-minutes.

For example, lets say that your drift time is 2min and 36 sec, that becomes 2.60 minutes (36/60=0.60min). Now lets multiply that out, 2.60x0.25x60=39 arc-minutes.

There is also a formula for using any star but I can't remember weather you use the sin or cosin for the stars declination. So lets skip that for now.

#8 ladip63

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Posted 18 March 2010 - 02:56 PM

thanks Buddy
I'll try that.
Gee that means more math learning for me. Math hates me. :( My brain shuts down when it comes to algebra. I'm willing to try math til it kills me.


Lynn

#9 proud uncle

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Posted 18 March 2010 - 05:05 PM

Thanks, Buddy. Your explanation makes sense. I'm OK with math, so it should work. I agree, dealing with a star on the celestial equator is easier.

#10 JayinUT

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Posted 18 March 2010 - 06:14 PM

Lynn,

Terrific capture of M109. It is not an easy sight in LP skies and you have captured its shape and location. Averted vision helps so much. Good job.

#11 CarlosEH

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Posted 18 March 2010 - 07:44 PM

Lynn,

An excellent observation of M109. This is not an easy galaxy to observe. Thank you for sharing it with us all.

Links;
http://www.hawastsoc...ps/uma/uma2.gif
http://faulkes-telescope.com/node/1716
http://www.noao.edu/...rvers/m109.html

Carlos

#12 ladip63

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Posted 19 March 2010 - 09:53 AM

Thanks Jay and Carlos.
thanks for the links Carlos. Pretty pictures. My first thoughts I drew that! :D
Lynn

#13 niteskystargazer

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Posted 19 March 2010 - 10:13 AM

Ladip63

:thanx:, for the sketch, I've look for it, bur never found it.

:thanx:,

Tom

#14 ladip63

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Posted 19 March 2010 - 10:24 AM

Thanks Tom, :D
It came right after M-40 on my list. It was hard to see and I was in dark skies. Just a glow from a small town 67 miles away.
Just keep trying. I know you will find it one day Tom.

Lynn






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