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M81 Naked EYE?????

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#1 miniventures

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Posted 19 April 2007 - 07:47 PM

Hey all, I am writing some newletter articles and one on M81.
In the course of my research, I came across a comment by Stephen J O'Meara (Mr. Eyes :) ) claiming that he saw M81 naked eye from Hawaii (I assume on Mauna Kea). Upon more digging, I find that Brian Skiff of Lowell Observatory has seen it naked eye as well as several folks at the Oregon Star Party last summer.

Can this be really true?? Heck, M81 is 12 million light years away?? What do you think??

#2 Phillip Creed

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Posted 19 April 2007 - 08:20 PM

Larry,

Yes, it CAN be done. I've done it before, but it's obviously not too easy. Here's what I find is typically the requirements:

1. Overcorrected eyeglasses to correct nighttime myopia (See the Sept. 2005 S&T article by Joshua Roth). I found that my "O'Meara Glasses" net an extra 0.3-mag naked-eye under a dark sky.

2. Very good transparency, with a sapphire-blue daytime sky.

3. A very dark sky, "blue" (Bortle Class 3) or better on the Clear Sky Clock Light Pollution Map.

4. Wait until M81 is at upper culmination.

If I make the attempt, I look halfway between the 5.7-mag star HIP 47594 and 7.1-mag star HIP 49765. NOTE: M81 is a non-stellar object, so don't let the 6.8-mag listed value fool you. I need the right host of conditions to come together to see the 7.1-mag star. If I can't detect the 7.1-mag star, I don't bother making the attempt for M81.

Even in the Eastern U.S., it is possible if you're in a really dark spot and a cold front has cleaned out the air. I've done this from Allegheny National Forest and Cherry Springs in PA, plus Spruce Knob and Calhoun County Park in WV.

I've tried it from Bortle Class 4 skies in SE and SW Ohio on nights where I could get down to 7.0-mag with the naked-eye looking overhead, but without success in detecting M81 with the naked-eye.

Another interesting M81 challenge is to see how little aperture is required to see the spiral arms. I can juuuuuust start to glean spiral structure in a set of 25x100s under dark, transparent skies. Of course, O'Meara in his Messier Objects book was able to sketch out the spiral arms to a great extent and detail.

Steve O'Meara's eyes (and skies) will EASILY best mine, too. He can see M83 (!) with the naked-eye!

Clear Skies,
Phil

#3 miniventures

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Posted 19 April 2007 - 08:28 PM

Phillip, thank you for that! I have never tried to look for it without at least binoculars and I live in dark sky country!

I need to find an eye doctor who believes in night time myopia--mine told me the theory was full of hogwash even though I have trouble reading some road signs in the dark with "well-corrected" lenses in my eyeglasses.

I will certainly give this a try this summer!

#4 Phillip Creed

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Posted 19 April 2007 - 08:38 PM

Larry,

Look here:

http://www.optego.co...gnostic set.htm

This company makes diopter flippers. By putting these in front of your regular eyeglasses, you can find the amount of overcorrection required to get pinpoint-sharp images.

Clear Skies,
Phil

Cle

#5 Silicon Owl

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Posted 19 April 2007 - 09:31 PM

Hmmm, I will be up on Mauna Kea Saturday night while babysitting a documenary film crew for Keck. Will need a few things to keep me occupied while they film and several of the shots on the schedule will be outside (filming the laser guide system).

Have to try and see if I can see it, may need oxygen! I will have my camera and binoculars with me. Thanks for the idea!

Andrew

#6 Tony Flanders

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Posted 20 April 2007 - 07:18 AM

Look here:

http://www.optego.co...gnostic set.htm

This company makes diopter flippers. By putting these in front of your regular eyeglasses, you can find the amount of overcorrection required to get pinpoint-sharp images.


Strongly recommended! Extra correction is helpful for many folks, useless for others, and counterproductive for a few.
So guessing the optimal nighttime correction "blind" is a really bad idea.

Moreover, having purchased the flippers, you may find that you don't really need another pair of glasses after all. Most of the time I'm looking at the sky, I'm fairly casual about it, and I'm willing to hold a flipper in front of my face on the occasions when I'm really pushing the limits of "naked-eye" observing. Hey, it's a whole lot easier than binoculars, which are easy enough to start with!

#7 Starman1

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Posted 20 April 2007 - 10:01 AM

Counter-intuitively, far-sighted or presbyopic viewers may need more positive correction for dark adapted naked eye viewing--the opposite of myopic viewers.

I recently (a year ago) got fully-corrected distance vision glasses that corrected my vision to nearly perfect (about 20/10 to 20/15), concentrating on "whole-eye" astigmatism correction (in my case 3 cylinders of astigmatism of only 0.1 to 0.2 diopters of astigmatism, usually beneath the resolution of corrective techniques).

For a while (my correction changed, unfortunately), naked eye stars were tiny little round pinpoints with no flares. This was better correction than I had had in my life. I started observing at age 11-12, and never saw the stars without flares until these glasses. It extended my naked eye limiting magnitude from 6.2-6.4 (my usual for years) to 6.7-6.9 just because of the correction. The faintest stars were (are) no longer smeared out and remain visible to both direct and averted visions.

These glasses do not help at the eyepiece, where the exit pupil is always smaller than my dark-adapted pupil, but they make a huge difference in naked-eye viewing. When looking at the Milky Way in Cygnus, for example, the star cloud becomes grainy, implying incipient resolution of the (largely) magnitude 9 stars.

The point is, even if, like me, you've had 20/20 vision your whole life, have your optometrist or opthamologist do a complete distance vision evaluation on you--especially if you have the type who can do a "whole-eye" tomographic evaluation of the cornea.
You CAN have better vision than you've had all your life. It may not be worth the expense (my lenses were $290 each!) for normal life, but it is worth the expense for astronomy.

M81 seems to be regularly visible to a lot of people if the light pollution grade is Bortle Class 3 or better. The AmAstro group has quite a few members who have detected it.
I've tried around 10 times on nights where my SQM read 21.70 to 21.85, and never spotted it. I'm afraid my retinas aren't sensitive enough to see to magnitude 8 under any conditions.
I can see about 30 of the Messier objects naked eye; just not M81.

But YOU may IF you have the correction, good seeing, and great transparency. Plot a chart with all the nearby stars to mag.9 and check which you can and can't see. You may discover you CAN see it.

Good luck.

#8 i_sairanen

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Posted 21 April 2007 - 02:46 AM

http://www.kolumbus..../Messier81.html

#9 miniventures

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Posted 21 April 2007 - 09:16 AM

This is fascinating, folks. I had no idea this was possible. Phillip, I ordered a set of those flippers yesterday---it is sure worth a try. Thanks everyone and keep any reports coming, I will be using them in my article if that's okay with y'all.

#10 Silicon Owl

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Posted 23 April 2007 - 04:25 PM

Tried and failed to see it this Sat from the summit as well as from 9000ft on Mauna Kea. The moon was just too bright and once the moon had set M81 was slipping away and too low in the sky. M81 and M82 was an easy binocular object, just no chance to see it naked eye. Had a good night despite this!

Andrew

#11 Downward Bound

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Posted 07 May 2007 - 10:49 PM

Last Friday night I was at my place in the Cascade Mountains enjoying a night of very dark skies (SQM range 21.83 to 22.0). I could detect a faint, unresolvable patch of light just where I would expect to see M81 - just a dim dusting of light. I confirmed my perception through my binoculars that the location was in fact M81. To be honest I still don't believe I saw M81 but I can't think of any thing else in that broad FOV that it could be mistaken for? :shrug:

#12 Phillip Creed

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Posted 08 May 2007 - 09:23 AM

Bill,

Welcome to Club 81!

M81 is a difficult naked-eye test. The one saving grace is the lack of local "interference" within a degree of the galaxy. There are some objects that, to the naked-eye, could not be seen individually with the naked-eye, but are close enough to have their light "combined" to the point where they're detectable.

For instance, an individual 8.0-mag star would be invisible to an observer in a super-dark sky if his/her personal NLM is 7.5. However, if two 8.0-mag stars were within a few arc-minutes (and thus unresolvable to the naked-eye), their light would "combine" to the equivalent of a 7.25-mag "star", and they'd be visible.

M81 doesn't really have this problem. The closest stars that could contribute anything more than a 0.1-mag boost in summary brightness (two 9th-mag stars, to be exact) are about 20' away. IMO, that's simply too much separation for "boosting" the galaxy's brightness.

Clear Skies,
Phil

#13 SigurRosFan

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Posted 08 May 2007 - 01:53 PM

This is fascinating, folks. I had no idea this was possible.

Larry, other possible naked eye objects are Neptune and the moons of Jupiter.

#14 MikeRatcliff

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Posted 08 May 2007 - 04:07 PM

Patrick Moore, famed amateur astronomer from the UK (and currently on his way to the doghouse for his recent BBC comments), found several people who could see the crescent shape of Venus. Some others with him claimed to see it but had the orientation wrong. He purposely didn't tell anyone about the inverted refractor image. A few puzzled people said what they saw was backwards from what they saw in the scope. He knew these folks really saw it.

Personally, I'm still struggling with M33 naked eye. Haven't tried the special glasses yet. Was able to do the main split of the double-double in Lyra, but that is not a big deal for normal vision.

I had good 20/15 uncorrected vision as a youth, but not anymore!

Mike

#15 Starman1

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Posted 08 May 2007 - 04:43 PM

Mike,

After correcting my distance vision completely about a year or so ago, I caught the "horns of Venus" in a not-completely-dark sky near inferior conjunction.
I was never able to see it as a child. But the glasses enabled me to see it.
Unfortunately, the vision in one eye has deteriorated and is no longer correctable to the degree it was, but if you have an optometrist who will take the time, you'll be able to achieve 20/10 vision with your glasses.

More than the Horns of Venus, the most exciting thing was seeing all the stars in the sky as pinpoints without any flares and seeing almost a half magnitude fainter with the naked eye.

#16 David Knisely

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Posted 08 May 2007 - 04:53 PM

This is fascinating, folks. I had no idea this was possible.

Larry, other possible naked eye objects are Neptune and the moons of Jupiter.


The moons of Jupiter are definitely possible for people with unusually acute vision, as their magnitudes are bright enough to see with the unaided eye. I have a friend of mine who is able to see at least a few of them without optical aid. However, Neptune is very probably not routinely viewable. The brightest that planet gets is around 7.8 or so, and with the number of faint stars in that magnitude range, it is doubtful one could easily pick it out even if the skies permitted you to go that faint. I have been at locations where the limiting magnitude is about 7.8, but there were so many stars visible that it was difficult to identify a specific star. Most people don't get much fainter than 7th magnitude from their dark sky sites anyway, so Neptune will probably remain one of the nearly impossible challenges of naked-eye viewing. Clear skies to you.

#17 Downward Bound

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Posted 09 May 2007 - 05:50 PM

Bill,

Welcome to Club 81!


Thanks!! :bigshock:

I'll be going back there often so I hope to confirm the sighting!!

#18 Amar A. Sharma

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Posted 18 June 2007 - 04:55 PM

Well what would be the range of amount of dark adaptation required for this? How much time before would you need to get rid of even the dimmest source of interfering light?

#19 Phillip Creed

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Posted 19 June 2007 - 07:11 AM

Amar,

Everytime I've been successful, I was in a Bortle Class 3 sky or better with good transparency, and refrained from looking at ALL lights (even red ones to consult star charts) for at least 15 minutes.

It's not an easy feat, by any stretch. But if you're successful, you'll know that your eyes alone were able to detect something that's 12 million light years away!

Clear Skies,
Phil

#20 Downward Bound

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Posted 19 June 2007 - 02:24 PM

Well what would be the range of amount of dark adaptation required for this? How much time before would you need to get rid of even the dimmest source of interfering light?


I honestly don't know the answer to that question specifically. As noted above, this is a very dark site (at least SQM 21.8) and the skies were clear, no moon and the seeing was very good that night. I had been doing some general observing and didn't go out with the purpose of looking for M81 with the unaided eye. I would estimate that I had been out, fully light-adapted for an hour or more when I saw M81.

#21 JLava

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Posted 22 June 2007 - 12:44 AM

Larry, other possible naked eye objects are Neptune and the moons of Jupiter.


Really?? Jupiter's moons? And I thought my eyesight was good!


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