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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12592
Loc: Cumberland, R I , USA42N71.4W
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M74 will not give itself up easily. It has a surface brightness of mag 14+. It is the most difficult object I have ever found. I found it at 2AM on a night with no moon and mag 5.5 skies.
I checked against a chart list to see how many of the Messier's I have found. There are 15 I am not sure I have ever seen in any type of instrument and would need to go back through all my field logs to verify. I have counted 45 that I could not be sure of that I have seen in binoculars. Only 5 to 10 of those are in question and will reqire checking the logs. So for right now I can say only for sure that I have seen 55 of the Messier Objects in binoculars.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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Quick note before I head back from lunch.
I live in Nova Scotia, Canada, I mostly observe from near the coast where the fog and rain prevail but forunatly that's where pretty much where the population lives. So if you drive 2 hours inland you can get very far away from any outdoor lights. Liscomb Game Reserve is my current dark sky site and we have a Clear Sky Clock set up for it, unfortunatly the scan for LP hasn't gotten there yet, but if you look at any other maps for Nova Scotia on CSC you'll see many area which are black, not grey or blue but jet black and this site I'm using is in a better location then some of those. The nearest city, and it's a small city, is 105km's by line of site/as the crow flies but it's all bog and marsh with a line of high hills. The person who showed this site to us is a GIS mapper with the city so we have good topo maps of the area to boot 
Basically the conditions there are near perfect so long as it's clear. Although we are familiar with LVM tests it's been difficult to get a good solid reading at this site. I can say that magnitude 6.5 stars are pretty easy with direct vision, and I've seen mag.6.8-7.1 with averted vision but both nights I was testing were not ideal though I did observe M74 on the 7.1 night and the other night which was better. The best night I had there was spent scanning the sky and I simply forget to estimate.
There are 2-3 great spots, both located well above the local geography so all the ground hugging fog is kept at bay and there is always a light breeze blowing up the 2 hills you can observe from so dew hasn't been a problem. I know it sounds almost too good to be true but I spent many long hours over several years driving twisty dirt roads and the others spent ten fold that to find this place.
Unfortunatly only about 1 day a month is worthwhile to make the trip up there due to weather/life but I usually do get up. I've had a heck of a time getting anyone else to come, since mag. 6 sky is common here they seem happy with "great" sky but don't want a 2hr drive for "excellent".
So if anyone ever gets up to Nova Scotia and it's clear I'm more then happy to offer a lift out
-Chris
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Chris
7X50 Vixen,22X100 Antares
80mm William Optics Megrez II ED
Santel MK6
Borg 125SD f6 (Pentax/Oasis version)
Tak-Lapides
Pentax XW's 40,20,14,10,3.5 3.8XP, Speers 5-8, 30mm Widescan III
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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The Bushnells 10X50's & about 12 years old. I'm still under 30 so take advantage of a 7mm pupil and dedicated observing glasses. The Bushnells are made for "eyeglasses on" observing, definitly a mediocre bino at best. The first time I observed M74 I only just barely saw it, and I sat still in my observing chair for about 10 minutes looking for it. The second time out I mounted the binos to a video tripod, and confirmed with another experienced observer that this indeed was the galaxy.
For Magnitude estimates I've been using the charts in the RASC Observers Hanbook as well as other stars in Sky Atlas 2000.
When I first observed all the Messiers a decade ago M74 gave me some trouble in my 8-inch dob. I tracked them all down back in 1995 from a Mag 6 sky outside of town. A couple years ago I joined the RASC and in 2002 decided to track them all down again with an 80mm f5 scope operating at 12.5X. It took longer, 14 months, but I was able to observe them all and my notes indicate that M76 gave me the most trouble and I finally observed it from the dark site. That's when I got the Idea to try and nab all the M's with 10X50's
Early this fall we had two excellent nights only a few days apart. I was able to observe from our club observatory under mag 6.3-6.4 sky using the 17.5 dob. A few nights later I was out at the dark site and with a 10-inch dob the view was almost identical to that of the 17.5 on M13, M92, M22, M17 and M8.
After observing under "very good" mag. 6.x sky and then 7.x I've come to the conclusion that dark sky is often better then larger equipment under worse sky. There are definite hues to a dark sky which lead to better observations. For example the destinction between M33 and the sky is very difficult under any light pollution while under an excellent sky you see how the grey color of the galaxy is simply a different hue then the dark blue/greyish night sky.
-Chris
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Chris
7X50 Vixen,22X100 Antares
80mm William Optics Megrez II ED
Santel MK6
Borg 125SD f6 (Pentax/Oasis version)
Tak-Lapides
Pentax XW's 40,20,14,10,3.5 3.8XP, Speers 5-8, 30mm Widescan III
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12592
Loc: Cumberland, R I , USA42N71.4W
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These are some nice observations. Your dark skies explain a lot!
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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mirage
professor emeritus
Reged: 09/23/04
Posts: 693
Loc: central texas
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Quote:
Liscomb Game Reserve is my current dark sky site and we have a Clear Sky Clock set up for it, unfortunatly the scan for LP hasn't gotten there yet, but if you look at any other maps for Nova Scotia on CSC you'll see many area which are black, not grey or blue but jet black and this site I'm using is in a better location then some of those.
Basically the conditions there are near perfect so long as it's clear. I can say that magnitude 6.5 stars are pretty easy with direct vision, and I've seen mag.6.8-7.1 with averted vision but both nights I was testing were not ideal though I did observe M74 on the 7.1 night and the other night which was better.
I composited a nice dark-sky map which, when coupled with detailed county road maps, does wonders for helping me find hidden sites. I'm about fifteen minutes from Bortle 4, fourty-five minutes from Bortle 3, an hour and a half from Bortle 2, and three hours from Bortle 1 skies. I hadn't considered it worth the drive out to Bortle 1, but reading your report makes me think otherwise! 
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imber stellarum 10x50 binoculars
architectural advisor
friends of the austin planetarium
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btschumy
Think Astronomy
Reged: 04/13/04
Posts: 1110
Loc: Austin, TX, USA
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Mirage,
How did you make your dark skies map? I'm in Austin, so your map is useful as it is. I'm just curious as to where you got your data?
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Bill Tschumy
Where is M13? Freeware -- Add a new dimension to your observing.
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mirage
professor emeritus
Reged: 09/23/04
Posts: 693
Loc: central texas
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Quote:
How did you make your dark skies map? I'm in Austin, so your map is useful as it is. I'm just curious as to where you got your data?
It's all from the World Atlas of Artificial Night Sky Brightness. ClearDarkSky.com has plotted exact longitude and latitude locations for every observatory clock it hosts - they're visible as tiny crosses on each of the small Light Pollution Maps it's clipped from the Light Pollution Science and Technology Institute's full-resolution North America map.
In this case, I took the Hill Country State Natural Area Light Pollution Map, which is fairly well centered on the area in question, and spent a long afternoon warping its horizontal and vertical scales until all the observatory locations matched up with the projection used in a Hill Country tourist road map I found online. Then it was a simple matter of tweaking brightness and combining the images into something legible.
The roads shown therein are far from comprehensive, but they give a solid frame of reference. I use the Texas Department of Transportation's County Highway maps, which chart every surveyed public right of way, paved or unpaved, to find hidden backroads under my target skies. Please feel free to share it with anyone else who might find it useful!
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imber stellarum 10x50 binoculars
architectural advisor
friends of the austin planetarium
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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Last night we observed M74 from Mag 6.6 sky outside of town and it wasn't overly difficult in my new 15X70's, you had to know where to look but it was a large oval smudge at 15X and was detected more easily then the Helix Nebula which I observe frequently, but this time I did note 3 faint stars within the nebula and a definite blue color both of which I havn't observed before.
In reference to my previous posts I obtained Stephen O'Meras' Messier objects and he has observed M74 in 7X35's from a dark site. That's a great book, it's nice to see that my observations concur with his.
-Chris
-Chris
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Chris
7X50 Vixen,22X100 Antares
80mm William Optics Megrez II ED
Santel MK6
Borg 125SD f6 (Pentax/Oasis version)
Tak-Lapides
Pentax XW's 40,20,14,10,3.5 3.8XP, Speers 5-8, 30mm Widescan III
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Anonymous
Unregistered
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I can only wish to have your dark sky conditions Chris. Since seeing M74 seems to have become a figure of merit for binocular optical quality, I look forward to the next chance I have this winter.
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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Well the Bushnell 10X50's are no prize They suffer from Astigmatism, Bak-7 prisms and serious CA. The new 15X70 Celestrons I bought seem like Apo's compared to them
It's cloudy and raining again here in Nova Scotia so don't get too jelouse. To make a go of this hobby here you have to plan for the clear breaks and be ready to drop everything at a moments notice when a clear evening arrives.
Boston isn't too far from here, it's only a days drive you should think about vacationing here sometime in the late summer/early fall usually one night in three is pretty good that time of year. Just throw your scope/binos in the car too and keep an eye on Clear Sky Clock.
-Chris
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Chris
7X50 Vixen,22X100 Antares
80mm William Optics Megrez II ED
Santel MK6
Borg 125SD f6 (Pentax/Oasis version)
Tak-Lapides
Pentax XW's 40,20,14,10,3.5 3.8XP, Speers 5-8, 30mm Widescan III
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Anonymous
Unregistered
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The storm that blew through here, literally, is heading your way I think. Anyway, thanks for the regional invitation. My wife and I have been wanting to pay Nova Scotia a visit sometime and now I have an additional reason.
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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Yeah we got the big rain storm here last night, but it's clearing now. Hopefully I can get out this evening if a break in the systems develope otherwise the foreseable forecast is pretty gloomy with rain/flurries for the next week.
The weather here is best between mid Aug and mid Oct
-Chris
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Chris
7X50 Vixen,22X100 Antares
80mm William Optics Megrez II ED
Santel MK6
Borg 125SD f6 (Pentax/Oasis version)
Tak-Lapides
Pentax XW's 40,20,14,10,3.5 3.8XP, Speers 5-8, 30mm Widescan III
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Blues
sage
Reged: 10/18/04
Posts: 288
Loc: NC
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I've got to say I'm impressed with the ability to see M74 with binoculars. (I haven't tried it with my 10x50's.)
I took a look at it last night with my XT8 and though I found it quickly, it was still fairly faint (though a very nice object) in an 8" scope. (The skies were clear and dark.)
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Elliott
Orion XT8 Classic
Orion Vista 10x50
Live Free Or Die
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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I think it has more to do with dark skies then anything else I wasn't able to see it under mag 5.9 sky with 10X50's. As Ed mentioned the surface brightness is ~14 but when they measure those numbers it's usually in the blue part of the spectrum so they tend to be fainter then what the eye sees. With the 15X70's M74 was easier for us to pick up initially then the Helix
-Chris
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Anonymous
Unregistered
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Are you sure about your claim that brightness is measured at blue wavelengths? I do not believe that brightness measurements typically performed have anything to do with any particular wavelength. Surface brightness is the total luminosity of all optical wavelengths divided by the area.
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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I agree that surface brightness should = total luminosity but in the first edition of the Backyard Astronomers Guide Dickinson mentions this, I'll look it up when I get back home, I'm on the road, but it is in the deep sky section.
Anyways, back to the topic at hand I was just out, 11pm AST 05,12,04, observing comet Machholz with the Celestron 15X70's and noticed that the M74 area was about as high as it gets and thought I'd try for it. The LVM from downtown, pop 30,000, is ~5.6-5.8. Clear Sky Clock's LP map rates it as orange. I blocked the streetlights and security lights from the 3 neighbors and I was able to just barely make out the faint glow of M74. Encouraged, I then hunted down M77 which despite the lower altitude was easier to see. M74 was definitely at the limit, I had to scan and wobble the binos to pick it up, but after that I could see it when the binos were at rest. I must admit that I've observed this M more in the past 3 months then in the past 10 years and that going from an extremely dark site and working my way into town probably has advantages as well
-Chris
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Chris
7X50 Vixen,22X100 Antares
80mm William Optics Megrez II ED
Santel MK6
Borg 125SD f6 (Pentax/Oasis version)
Tak-Lapides
Pentax XW's 40,20,14,10,3.5 3.8XP, Speers 5-8, 30mm Widescan III
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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Well I arrived back home and dug out The Backyard Astronomers Guide 1st edition.
P 183 “magnitudes are measured using a set of photometric filters whose bandpass do not coincide with the green part of the spectrum”
P 189 “Most galaxy magnitudes are photographic, which means they were measured in the blue part of the spectrum. These values are generally fainter then visual magnitudes (yellow-green).”
Second Edition P 257 “official magnitude figures may not be reliable indicators of the actual brightness”
Also see O’meras’ Messier Book I think it’s on M33 he discusses visibility of galaxies and the visual spectrum and the reader will see his mag estimates vs the accepted values in his book, and they often differ. I think Clyde Tombaugh mentioned blue photographic magnitudes in his book on the discovery of Pluto. If I recall correctly they thought the 9th planet might be blue like Neptune, but I've recently read Pluto and Charon so it may have been there as spectra has a whole chapter dedicated.
Even where all spectra are equally measured we are talking visual visibility of M74 under low light where the eye is most sensitive to green. Some deep sky objects emit more blue, others red, if an observer is sensitive to one of those they may very well pick up more detail or be able to see an object which remains invisible to another observer using the same equipment under the same conditions.
I don’t disagree that surface brightness is the total luminosity, but we have to be critical in how those total luminosities are measured and keep it in the context of the visual observations.
-Chris
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Anonymous
Unregistered
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When was this book written? "Photographic"?...ahem....CCDs are the standard now. Those photographic plates are most sensitive at 420 nm.
We can measure the brightness (and hense the magnitudes) in the infrared up to UV by using various filters and photoelectric photometers. This allows many different magnitudes to be measured at various wavelengths (or bandpass). A common one is a UBV system: an Ultraviolet, a Blue, and Visual magnitude measuring system. That's about 360 nm to 550 nm. The brightnesses in this wavelength region are then averaged when being published. Thanks to CCDs, the UBV has been extended into the infrared. These wavelengths are now included with the reported "average" magnitudes.
One could, I suppose, use filtering just to measure the brightness at the blue wavelengths which may be of specialized interest.
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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My point was simply that we can not always trust published magnitude estimates for visual observing because they may take into account spectra beyond what the visual observer is able to detect. Sometimes this means the object visually appears brighter then the estimate, sometimes fainter.
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