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M51 is different apertures.

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#1 stargazer193857

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Posted 02 November 2019 - 11:03 PM

It depends a lot on transparency, how close to meridian, and whether it is in the sunset or in a light some.

It hangs off the end of the handle of the big Dipper and is visible in the summer.

Every time I've looked with 4-8" aperture, M51 has been a smudge.
In 10" aperture, it was a smudge in a dob and a defined colorless spiral in a 10" SCT.
12", the one view I saw was blown up too big and too dim.
18" dob, it looked ghostly blue and bigger than in the 10" SCT, and a clear spiral.
20" dob, near meridian, away from light domes, late at night, it was a nighter blue with purple knots and a clear spiral, and not small at all.

I've never seen it in a 30", but I'd love to. 72" would be better. I've not even seen it in a 25" that was pointed at other stuff. The volunteer operator did not know the NGC number for M51, and so could not look it up in the go-to.


What were your best views and what aperture?
(My best view of the double cluster was in a 5" newt, during exceptional transparency that showed me how bad most nights actually are. It was at least 4x as bright as seconds later when in dimmed back to how I normally see it.)

#2 stargazer193857

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Posted 02 November 2019 - 11:15 PM

I want to see M51 in the biggest aperture possible, and wonder how much more important timing and good transparency is. I wonder if 18" f3.3 would be good enough for life, or if 20" f3 to 24" f2.75 would be much better and leave the 18" impotent.

#3 Jeffmar

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Posted 03 November 2019 - 01:16 AM

I saw M51 in a 24 inch dob. It was fairly bright, the shape was obvious, it was vaguely blue, and not well focused. I think It needed some collimation. My C11 showed the shape, some dust lanes and no color. This was at a Bryce Canyon star party a few years ago in Utah. I really thought that 24 inch dob was going to give me one of those mind blowing views. shrug.gif


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#4 Astro-Master

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Posted 03 November 2019 - 02:58 AM

Sky conditions will make or break a good view of M51.  I've had my best view of M51 in my 18" Obsession F/4.5 from a dark high desert site, SQM 21:65, transparency was very good, and the seeing was very good allowing a power of 270x with my 17 Ethos and a Astro-Physics Barlow.

 

The galaxy filled the field of view, and was brighter with more detail than I'd ever seen it before.  There was so much detail in the spiral arms, it took your breath away.  It was a magical night for the next 3 hours, every object was the best I'd ever seen.  And then the seeing changed, along with the transparency, and the magic was gone.

 

Most nights from the same desert site with the 18" are fair to good, but I'll never forget how it looked on that magical night a few years ago.

 

I think using Ethos eyepieces from a dark site with high power to darken the sky background, and improve the contrast and still getting the whole galaxy in the 100* field is key to seeing the galaxy at its best.


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#5 David Knisely

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Posted 03 November 2019 - 04:01 AM

From my dark sky site (and when fully dark adapted), M51 has always shown some detail, although to get the most out of it, you have to study it at a variety of magnifications and use averted vision.  In my 100mm f/6 refractor, M51 shows an almost ring-like form around its somewhat brighter core region, with its companion NGC 5195 hugging its northern side.  In a six inch at around 70x, the ring seems slightly broken with hints of a more arc-like nature, although the true spiral form is still somewhat vague.  In my 8 inch f/7, I can get a bit of the overall spiral form at between 80x and 120x, and in my 10 inch under good conditions, the spiral form is dim but unmistakable at between 100x and 176x, with a little of the dust lane patches visible across some of the arms as well as the hints of the connection between M51 and the companion.  On a truly excellent night, I have even see the three faint tidal "prongs" that extend northward away from NGC 5195.  In my 14 inch, there is quite a bit of structure in the arm segments, with some definite brightness variations in the arms, and the galaxy can be easily studied at powers over 200x.  Clear skies to you.


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#6 Astrojensen

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Posted 03 November 2019 - 04:13 AM

I can faintly see the spiral arms and dust bands with my 4" f/11 ED on a really superb night. In my 6" achromat or newtonian, they're a bit more evident on the same night. Even my 63mm Zeiss shows some irregularity in the disk, plus some details in the companion galaxy, NGC 5195. 

 

4" view under superb conditions, 6" under good conditions. Drawing made March 12th, 2012, 6" f/8 achromat and binoviewer, 30x - 120x. SQM 21.4, NELM 6+.

 

gallery_55742_324_1407448826_25253.jpg

 

 

63mm Zeiss Telemator view under superb conditions. March 24th, 2011. Binoviewer, 26x - 58x, NELM 6.5. Notice that the bridge between the galaxies could be seen.

 

gallery_55742_324_1407446950_23133.jpg

 

 

Clear skies!
Thomas, Denmark


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#7 Asbytec

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Posted 03 November 2019 - 05:43 AM

Thomas, interesting how close our observations are in a 6". Nice. 

 

m51rev.png


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#8 Astrojensen

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Posted 03 November 2019 - 06:24 AM

Thomas, interesting how close our observations are in a 6". Nice. 

 

attachicon.gif m51rev.png

Well, it's not all that surprising, right? wink.gif  I mean, both scopes are 6" aperture and our skies are probably quite similar, even if the latitude isn't. We also both have many years of experience, so it doesn't surprise me. 

 

Your drawing is very nice, BTW. Much better than mine. 

 

 

Clear skies!
Thomas, Denmark


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#9 Asbytec

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Posted 03 November 2019 - 06:41 AM

Well, it's not all that surprising, right? wink.gif  I mean, both scopes are 6" aperture and our skies are probably quite similar, even if the latitude isn't. We also both have many years of experience, so it doesn't surprise me. 

 

Your drawing is very nice, BTW. Much better than mine. 

 

 

Clear skies!
Thomas, Denmark

Now, that you put it that way, no it's not surprising. It is the same object, as well, and after all. But, it is really nice to see others capturing very similar detail. It's adds something to our own solo observation done separately. Your's offers credibility to my own observation, that's important to me cuz observing is not always easy and sometimes fraught with uncertainty. :)

 

Thank you for complementing the sketch. It's done in GIMP that has some nice features and a HUGE learning curve I have not even begun to explore. And never will. I just stick with the basics and try to give it a soft touch. Try to be somewhat realistic, but at the same time not requiring others to do the same long observation of our sketch as we did observing the object. :lol: 



#10 stargazer193857

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Posted 03 November 2019 - 10:07 AM

Please keep the comparisons coming. If you've not looked at M51 much, substitute a different small galaxy, or the M31 dust lanes.

A clear night has a maximum view, so that you need at least a certain aperture for certain details, but the maximum may be high compared to what some people have seen. A hazy night has no limit to how hazy it can be, rendering the biggest apertures useless.
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#11 Astrojensen

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Posted 03 November 2019 - 11:10 AM

 

A hazy night has no limit to how hazy it can be, rendering the biggest apertures useless.

Haze will affect all apertures equally, but it actually feel like it is hitting smaller apertures *harder* than larger apertures, because large apertures have such a bright view in the first place and can step down a notch in magnification if the view gets dim, without sacrificing image scale too much. 

 

That is at least how it feels to me after comparing various apertures from naked eye to 30" under all kinds of conditions. If the sky is hazy enough to render a 30" useless, everything else will also be useless. 

 

 

Clear skies!
Thomas, Denmark


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#12 Diego

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Posted 03 November 2019 - 11:51 AM


In 10" aperture, it was a smudge in a dob and a defined colorless spiral in a 10" SCT.
12", the one view I saw was blown up too big and too dim.
18" dob, it looked ghostly blue and bigger than in the 10" SCT, and a clear spiral.


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.

#13 stargazer193857

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Posted 03 November 2019 - 02:33 PM

Different sites and different nights for the 10" scopes. The dob was at a yellow zone, and the SCT a grey zone. All these scopes were different nights. Also, I've seen transparency change profoundly in a matter of seconds.

The large CO of an SCT is bad mostly at highest power, were resolution may be proportional to clear aperture.

For low power views, the only contrast effect of a large secondary is light scatter off the edges, if you failed to flat black them.

SCT are expensive and often made to higher standards in other ways, compensating for the secondary.

#14 stargazer193857

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Posted 03 November 2019 - 02:39 PM

I recall a story of 3 dobs aimed at M51, a 16", a 20", and a 28". The 16" owner exclaimed how wonderful 16" is and that there is no need to go bigger. (Must have been a clear night). He then looked in the 20" and said, "Oh, aperture really does matter." The view I the 28" was even better.


But I have another true story. The day after California smoke had stopped blowing through Idaho, several scopes were pointed at clear sky. Many had murky views and dinner plate stars. My 50mm binoculars hard bright pristine views, as did a few 10" scopes. I guess no one wanted to bother cleaning the 25" mirror.

#15 Jeffmar

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Posted 03 November 2019 - 03:38 PM

This photo is as close as I could get to the actual view through my C14 in early October.

M51
 

 


Edited by Jeffmar, 03 November 2019 - 03:43 PM.

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#16 treadmarks

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Posted 03 November 2019 - 03:48 PM

My best view of M51, and one of my best views of anything period, was using my C8 during a vacation in Maine at a Bortle 4 site. I was able to see faint but long spiral arms and only with averted vision. I also saw the interacting galaxy. While faint, it is still the view of galaxies I aspire to, as someone who is not really a galaxy hunter. I hope to replicate this view of M51 in the future, and also see the same with M33 and M101 and similar galaxies.



#17 stargazer193857

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Posted 03 November 2019 - 04:49 PM

My best view of M51, and one of my best views of anything period, was using my C8 during a vacation in Maine at a Bortle 4 site. I was able to see faint but long spiral arms and only with averted vision. I also saw the interacting galaxy. While faint, it is still the view of galaxies I aspire to, as someone who is not really a galaxy hunter. I hope to replicate this view of M51 in the future, and also see the same with M33 and M101 and similar galaxies.


It is so sad that for many people living under light pollution, that is the best they can see any time soon.

We need to increase the number of star gazers before the sky is too bright to attract more.
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#18 jayrome

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Posted 04 November 2019 - 09:48 AM

I love observing M51. From the dark sky site I go to (Bortle  2 or 3ish) if seeing is good I can make out the spiral arms at 127x in the 10" dob. I've tried more recently with my new 5mm Hyperion ep, but seeing wasn't good and the view was no better than with the 10mm ep. Whenever I observe M51, I wonder, "are there people there maybe looking back?"

 

clear skies :)


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#19 Tony Flanders

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Posted 05 November 2019 - 06:08 AM

Different sites and different nights for the 10" scopes. The dob was at a yellow zone, and the SCT a grey zone.


You should have said that first!

The difference between a 10-inch Dob and a 10-inch SCT for viewing deep-sky objects is negligible. The difference between an 8-inch scope and a 10-inch scope is small. The difference between the yellow zone and the grey zone is VAST! So your initial summary put in lots of minor details and left out the important information.

An 8-inch scope under dark skies should show M51's spiral arms easily.


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#20 Diana N

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Posted 06 November 2019 - 02:23 PM

An 8-inch scope under dark skies should show M51's spiral arms easily.

I can confirm that from personal experience, having observed M51 with my 8" Teeter STS dob under a Bortle Class 1 sky.  Everyone should be lucky enough to observe galaxies under such a sky at least once!


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#21 Dave Mitsky

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Posted 07 November 2019 - 09:12 PM

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


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#22 Arcticpaddler

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Posted 07 November 2019 - 09:18 PM

From my backyard, Bortle 3 skies, M51 shows plenty of evidence of spiral structure.  Transparent and darkness make all the difference.  If the sky is at all hazy, why would anyone bother going after galaxies?  Makes ZERO sense.


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#23 Astrojensen

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Posted 08 November 2019 - 10:50 AM

From my backyard, Bortle 3 skies, M51 shows plenty of evidence of spiral structure.  Transparent and darkness make all the difference.  If the sky is at all hazy, why would anyone bother going after galaxies?  Makes ZERO sense.

Unfortunately, my skies are often a little hazy, sometimes quite a lot. This is obviously not ideal for galaxies, but I've got to work with what I've got. The upside is that occasionally the hazy skies can bring very good seeing and this is great for studying small, relatively bright details in galaxies at high magnifications, such as the core and nucleus or starbirth/HII regions, etc. 

 

 

Clear skies!
Thomas, Denmark


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#24 Arcticpaddler

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Posted 08 November 2019 - 04:26 PM

Unfortunately, my skies are often a little hazy, sometimes quite a lot. This is obviously not ideal for galaxies, but I've got to work with what I've got. The upside is that occasionally the hazy skies can bring very good seeing and this is great for studying small, relatively bright details in galaxies at high magnifications, such as the core and nucleus or starbirth/HII regions, etc. 

 

 

Clear skies!
Thomas, Denmark

Excellent points, Astrojensen.  I hadn't thought of that for galaxies, but it makes total sense.


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#25 Astrojedi

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Posted 08 November 2019 - 04:40 PM

In all my scopes 8" and bigger it shows quite a bit of detail. 10" and above start to show the "bridge". My 14" shows quite detailed structure and on clear dark desert evenings looks like an astrophoto.


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