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M51 is different apertures.

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#26 Astrojedi

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Posted 08 November 2019 - 05:03 PM

I'm surprised about your comment on the the 10" SCT getting a better view than the 10" dob. Usually SCT get a bad rap because of the large CO. I would have thought the views between the same apertures would at least be similar. Were both scopes at the same/similar power?

I'm in the southern hemisphere and M51 is too low on the horizon, same with M31. I've tried to see both. M31 just a smudge and M51 was too hard to find. Way down in the murk.

CO should have little or no impact on deep-sky observing. There are many factors that go into delivering contrast at the EP. In my experience CO is not that significant. The biggest is optical quality followed by mechanicals like baffling, flocking etc.


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#27 Astrojensen

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Posted 09 November 2019 - 05:38 AM

 10" and above start to show the "bridge". 

The bridge is actually visible in a 60mm on a superb night, with careful observation and exit pupils around 2 - 3mm. Likewise, the arm that curve around the western side towards the south ends in a broad fan shape, which is also visible. 

 

 

Clear skies!
Thomas, Denmark



#28 Astrojedi

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Posted 09 November 2019 - 07:09 AM

The bridge is actually visible in a 60mm on a superb night, with careful observation and exit pupils around 2 - 3mm. Likewise, the arm that curve around the western side towards the south ends in a broad fan shape, which is also visible. 

 

 

Clear skies!
Thomas, Denmark

I have never seen it with a 60mm but yes there are hints in smaller apertures with averted vision. A 10” shows it with direct vision. Likely you have better skies than me or are just more skilled an observer (very likely).



#29 Starman1

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Posted Today, 05:20 PM

Sketches of M51 at various apertures can be seen at https://clarkvision....pert/index.html

That's the most accurate comparison I've ever seen.  Bookmarked.

I have seen the dark lane in the bridge and the "fingers" extending from the companion in the 12.5", but that was an exceptional night

and M51 was high in the sky near the meridian.


Edited by Starman1, Today, 05:22 PM.


#30 Lukes1040

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Posted Today, 07:20 PM

That's the most accurate comparison I've ever seen. Bookmarked.
I have seen the dark lane in the bridge and the "fingers" extending from the companion in the 12.5", but that was an exceptional night
and M51 was high in the sky near the meridian.


I had a great night at my bortle 3 site a little over a year ago where I saw a sight similar to the 12.5” sketch on that site. It was with my 12” and a 9mm eyepiece, if I remember correctly. It was high in the sky as well.


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