Need help with M4 in Scorpio

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mikemarotta
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Need help with M4 in Scorpio

#1

Post by mikemarotta »


With Scorpio near the mediian in the summer, it is an easy target area. I have been trying to find M4 for months, even over the winter being up at 5:00 AM for other projects. This week our very unusual "monsoon season" broke and the skies have been nominally cloudless at night. I got out before the Moon rose over my neighbrhood and now it is rising later and is less problematic.

Messier 4 (NGC 6121) is commonly given as "almost the diameter of a full Moon" and Burnham says 20 minutes of arc. Burnham also catalogues this as magnitude 7. Burnham has it at 1.2 degrees west of Antares (1.3 in Wikipedia). The cluster itself is 7 and the individual stars are magnitude 11. I have noted elsewhere on TSS how my skies have degraded with the relaxation of Covid restrictions. And also the other night, while I did split Epsilon Lyrae into four, one pair was more difficult, less well defined, than the other, which was not true last October and November. Just saying that conditions being what they are, nonetheless, I am perplexed by my inability to find what should be an easy object.

(On that same note, while Ptolemy's Cluster M7 (NGC 6475) should also be easy, last night was "no joy" though I did have it four days ago for a VROD after repeatedly going from naked eye to binoculars before finding it with the telescope.)

Anyway ... just asking.
Thanks!
Mike M.
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Re: Need help with M4 in Scorpio

#2

Post by helicon »


I've been able to see it in my 15x70 binos as a puffball near Antares. Through the ten inch, it shows rather well and has resolution. It is not as impressive through my 6" Achro and I have yet to see it through my 5.1" newt. So my light pollution is probably just as bad as yours is. I would keep trying to see it.

Here are some more bright globulars near Antares:

https://skyandtelescope.org/observing/c ... r-antares/

Of course, if you get out to some darker skies there is a globular even closer to Antares than M4...NGC 6144 shining at magnitude 9.3. I also have observed this one as a faint patch with no resolution.
scorp.png
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Re: Need help with M4 in Scorpio

#3

Post by pakarinen »


I was perplexed when I first started searching for it. It's not visible from my home skies (B7-8) with my 80mm and only occasionally is it visible with my 120mm. It seems sensitive to LP / being low in the muck (or my skies just really are garbage). It is a pretty easy target under a darker sky.

When I've succeeded in seeing it at home, I've centered on Antares and then scanned west to the triangle of Antares, M4, and Sigma Sco. It shows up as a faint smudge, which I confirm is really there by wiggling the OTA a bit. I don't think I've ever seen it when the moon was up.

Good luck!
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Re: Need help with M4 in Scorpio

#4

Post by Don Pensack »


This cluster is fully resolved in a 100mm scope and mostly resolved in an 80mm.
Here is what I suggest:
--when Antares (the brightest star in Scorpius (the name of the constellation--Scorpio is an astrological sign) is on or near the N-S meridian,
point at Antares and move due west (or clockwise in azimuth if an alt-az mount)
--when you think you may be detecting it, increase the magnification to at least 100x. That will darken the background sky in the eyepiece and make a lot of fainter stars visible.
At that point, even if it is low in the muck, it should be visible. At -26.5°, even at 51°N, it will be 12.5° above the horizon. Many southern objects are still nice, even when that low.
It obviously helps to see it when it is near or crossing the meridian to see it at its highest point. It is the nearest, and probably brightest, of all the globular clusters visible to northern sky viewers.
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Re: Need help with M4 in Scorpio

#5

Post by Bigzmey »


M4 does not stand well to LP. When I observed it in 90mm refractor from home, it was very dim, just a ted brighter than the background, easy to miss when you swing by. Try to identify the spot by surrounding stars and then sit on it for awhile. Employ averted within and try different powers.
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Re: Need help with M4 in Scorpio

#6

Post by MistrBadgr »


I had to get down to a pupil size of 2.5mm in my Polaris 114 before definitely detecting it. I used a 40mm to get reasonably oriented just using stars, then started down the line of eyepiece to see what it took to get an indication. My best view was at about 1.5mm. pupil. (Meade 12.4mm Plossel eyepiece in 900mm scope) With the 9.7mm eyepiece I seemed to start loosing it again. My back yard registers on the Bortle 6 side of a Bortle 5-6 Boundary, maybe a quarter to half mile away. M4 was about to enter my community's light dome.

Hope this helps!
Bill Steen
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Re: Need help with M4 in Scorpio

#7

Post by mikemarotta »


Thanks to all. It is clear again tonight and the Moon is rising even later, midnight to 1:00 AM. So, I'll give it a go. For myself, knowing that something is possible because others have done it makes it easier to work toward success even if it takes perserverence.
Bigzmey wrote: Tue Jul 27, 2021 8:28 pm M4 does not stand well to LP. When I observed it in 90mm refractor from home, it was very dim, just a ted brighter than the background, easy to miss when you swing by. Try to identify the spot by surrounding stars and then sit on it for awhile. Employ averted within and try different powers.
Thanks. That was my intuition, but it helps to hear that from someone who knows. I did a lot of sweeping because I know that the eyes often catch movement. I will work more slowly and put more effort into averted vision.
Don Pensack wrote: Tue Jul 27, 2021 6:40 pm This cluster is fully resolved in a 100mm scope and mostly resolved in an 80mm.
Well, I have a 102. So, we're in the ballpark.
Don Pensack wrote: Here is what I suggest:
... Scorpius (the name of the constellation--Scorpio is an astrological sign) is ...
Tomayto, tomahto. I was born in November. but... moving right along...
Don Pensack wrote: point at Antares and move due west (or clockwise in azimuth if an alt-az mount)
--when you think you may be detecting it, increase the magnification to at least 100x.
AZ mount of course and with a correcting prism so that right and left are right and left.
100X means 6mm ocular or 13mm with 2X Barlow or 32mm with 5X focal extender. The 6mm is my least favorite and more glass just makes it harder for the light to get to my eyes, but, OK...
Don Pensack wrote: That will darken the background sky in the eyepiece and make a lot of fainter stars visible.
At that point, even if it is low in the muck, it should be visible. At -26.5°, even at 51°N, it will be 12.5° above the horizon.
See the userbox: I am in Austin, Texas. 30 North. Scorpio-ius is higher than the rooftops. Pretty easy to spot. Back in May when I was not finding the head of Virgo, I turned my attention to Corvus. (On my blog at https://necessaryfacts.blogspot.com/202 ... corvi.html )
Don Pensack wrote: It is the nearest, and probably brightest, of all the globular clusters visible to northern sky viewers.
So I am told. Hence the frustration. But thanks for the pointers. Everything helps.
pakarinen wrote: Tue Jul 27, 2021 1:27 pm I was perplexed when I first started searching for it. It's not visible from my home skies (B7-8) with my 80mm and only occasionally is it visible with my 120mm. It seems sensitive to LP / being low in the muck (or my skies just really are garbage). It is a pretty easy target under a darker sky.

When I've succeeded in seeing it at home, I've centered on Antares and then scanned west to the triangle of Antares, M4, and Sigma Sco. It shows up as a faint smudge, which I confirm is really there by wiggling the OTA a bit. I don't think I've ever seen it when the moon was up. Good luck!
Thanks. My kind of town... that toddlin' town... I am farther south. Thanks also for the navigation tip. I know that it is between Antares and Sigma Sco but the "triangle" image fills in the picture. Darker skies.... Yes, don't we all wish for them. But I would trade them all for an industrial society because absent the pollution, we could not have the telescopes in the first place. You know, North Korea has dark skies. Actually, that's what star parties are for and I might actually get around to traveling to one next year or the year after or whenever. It's just me: wet blanket. But I appreciate your reply and your assistance.
helicon wrote: Tue Jul 27, 2021 1:27 pm I've been able to see it in my 15x70 binos as a puffball near Antares. Through the ten inch, it shows rather well and has resolution. It is not as impressive through my 6" Achro and I have yet to see it through my 5.1" newt. So my light pollution is probably just as bad as yours is. I would keep trying to see it.
Will do... try and try again. 8-inches is my largest reflector and it is still in the boxes for now. (The collimating tools arrived today. I put them and the Star Testing book in the crate, too. Now, it's a package.)
helicon wrote: Here are some more bright globulars near Antares...Of course, if you get out to some darker skies there is a globular even closer to Antares than M4...NGC 6144 shining at magnitude 9.3. I also have observed this one as a faint patch with no resolution.
Yeah, I know that there's a rich field available. I'm just trying to find it all, starting with what should be the easiest. I am signed up for our club's dark sky site in August. We are having an astrophotography tutorial. I am not up for that, but I am interested in seeing how the instructor works the problems and how my comrades fare. So, I plan to take all of my telescopes and spend the night overnight.
MistrBadgr wrote: Tue Jul 27, 2021 9:22 pm I had to get down to a pupil size of 2.5mm ... My best view was at about 1.5mm. pupil. ... "

I do not know what that means in practical terms. I know what a eyeball pupil is and where mine are and what I look like in someone else's (hence the name "pupil"). But I don't know how to figure my pupil size against my ocular focal lengths. Sorry.
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Re: Need help with M4 in Scorpio

#8

Post by MistrBadgr »


Hi Michael,

Pupil size is the size of the image when it enters your eye. Going by pupil size is a pretty good way to relate one scope to another. In my case, with my primary mirror being 114mm across the glass disk and then allow a little for the bevel around the edge, you get the actual diameter of the active surface. I actually measured mine and it is right at 112mm diameter of mirrored surface. This relates to the clear objective size of your refractors.

To get the pupil size, divide the active diameter of your mirror or the actual opening diameter of your refractor by the magnification you are using and you will get your pupil size in mm. A short cut version is to divide the focal length of your eyepiece by the focal ratio of your scope. In my case, I first detected M4 with a 20mm Plossel eyepiece. My reflector has an f-ratio of 8. 20 divided by 8 is 2.5. you can take that 2.5 and multiply it by the f-ratio of your scope and it will give you the equivalent eye piece focal length for your scope to get an image roughly equivalent to what I had with my scope.

For objects like M4 that are difficult in terms of contrast with light pollution, moving to smaller and smaller pupil size (same as going to higher magnification) diminishes the background light for a given small area. A star, however, has an infinitesimal surface area, so it does not diminish at the same rate as the general sky. A globular cluster is not a single star, but still gets some of that benefit. Another reason for doing this decrease in pupil size and, therefore an overall decrease in light level is that your eye works better at telling the difference between lighter and darker areas. Up to the point where the brighter area starts disappearing on you, the contrast you can see, with practice, goes up. The image can seem a bit surrealistic at first, so it does take some practice.

As a general rule of thumb, a pupil size of 1.25mm will give you the best chance of seeing a deep sky object like a nebula or globular cluster. For me personally, I find that a 1.5mm pupil is better. There are a lot of factors that go into what works best for a particular eye, with specific equipment, light pollution, etc. So I think a person needs to try out the options of magnification some to find out what works best for him/her. In my case, M4 and M8 loose visible material around the outside. On M8, the stars were OK with a 9.7mm eyepiece, but I lost some of the nebula compared to my 12.4mm eyepiece. On the ring nebula, the grey tone differentiation was enough better with the 12.4 eyepiece, compared to the 9.7 or 15mm that occasionally I would get flashes with the 12.4mm where my brain got enough information that the ring looked like a spherical shell, rather than a flat doughnut.

What I have learned to do, once I learn what eyepiece is going to work best for a particular scope, is to start with the widest view I can get to find the right spot, either 40, 32, or 26mm. I will then switch to the 20mm if I started with the 40 or 32mm, 15mm if I started with the 26mm eyepiece (f/5 or shorter scope), as an intermediate spot to recenter the target area. Then go to the eyepiece that gets me the "sweet spot." I then sit on it, letting my eye wander around the field, concentrating a little bit away from the center of my vision. Slowly, little things can start showing up in the view that I would not see if I did not take some time. Sometimes this is the actual object itself that takes time to show up and sometimes it is small details about the object or other dim things around or inside the object.

Hope this helps!
Bill Steen
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Many eyepieces, just not really expensive ones.
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Re: Need help with M4 in Scorpio

#9

Post by mikemarotta »


Well.. it was predicted partly cloudy though clear when I posted a few hours ago. I just brought everything in. The weekend looks good.
AUSTIN WEATHER 27-31 JULY.jpg
MstrBadgr wrote: To get the pupil size, divide the active diameter of your mirror or the actual opening diameter of your refractor by the magnification you are using and you will get your pupil size in mm. A short cut version is to divide the focal length of your eyepiece by the focal ratio of your scope.
Thanks. Arithmetic is easy. I will do the maths and make a chart for my notebook. Good to know.
Best Regards,
Mike M.
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Re: Need help with M4 in Scorpio

#10

Post by Don Pensack »


At 30°N, M4 culminates (crosses the meridian) at an altitude higher than Polaris, so there should be no diminishment of visibility due to it's southern declination.
If it's not immediately obvious in the finder on the scope, or even to the naked eye, it is because of light pollution, and that is a tough thing to overcome.
Higher magnification is the obvious answer, but only once it is in the field.
Worry more about the magnification than the amount of glass. You have to diminish the brightness by 10% or more before it's even noticeable in a lab environment (10% is only 0.1 magnitude), and a Barlow does not do that.
If the field is darker, it's because of magnification, not the number of glass elements in the focuser.
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Re: Need help with M4 in Scorpio

#11

Post by mikemarotta »


MistrBadgr wrote: Wed Jul 28, 2021 2:02 am Hi Michael, Pupil size is the size of the image when it enters your eye. Going by pupil size is a pretty good way to relate ...
Thanks, again. I turned to Harrington's Star Ware first and then went out online and now I have quite a bit of background in pupil size. It is pretty easy to calculate and I made a table for my notebook. I am not sure that the numbers tell me anything I care to know, versus say, Field of View.

I agree with your closing observation that a lot depends on personal parameters. On that basis, I also made an appointment with my optmetrist to get my own pupils measured for full dark dilation.

Best Regards,
Mike M.
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Re: Need help with M4 in Scorpio

#12

Post by mikemarotta »


Don Pensack wrote: Wed Jul 28, 2021 2:14 pm At 30°N, M4 culminates (crosses the meridian) at an altitude higher than Polaris ...
And it does not face downtown Austin, another plus! I already know well that although it is nominally on or near the meridian right now at 2100 hours local, the better view for me is a bit westward about 210 degrees because of my neighborhood. Last week, when I reported Ptolemy's M7, that's where I found it. I have a major shopping center to my east.
Don Pensack wrote: Wed Jul 28, 2021 2:14 pm
Worry more about the magnification than the amount of glass. ... If the field is darker, it's because of magnification, not the number of glass elements in the focuser.
Good advice. I can try several combinations. I can mate my 2X Barlow with my 5X focal extender with the 6mm ocular for 1100X. :telescopewink: If nothing else, I can check my viteous humor for proteins. :Astronomer1:

I will report any (serious) success here, of course.
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Re: Need help with M4 in Scorpio

#13

Post by turboscrew »


mikemarotta wrote: Wed Jul 28, 2021 11:08 pm
MistrBadgr wrote: Wed Jul 28, 2021 2:02 am Hi Michael, Pupil size is the size of the image when it enters your eye. Going by pupil size is a pretty good way to relate ...
Thanks, again. I turned to Harrington's Star Ware first and then went out online and now I have quite a bit of background in pupil size. It is pretty easy to calculate and I made a table for my notebook. I am not sure that the numbers tell me anything I care to know, versus say, Field of View.

I agree with your closing observation that a lot depends on personal parameters. On that basis, I also made an appointment with my optmetrist to get my own pupils measured for full dark dilation.

Best Regards,
Mike M.
There is this Allen key trick you can use to measure your pupil size - although, probably not fully dark-adapted.
https://www.oreilly.com/library/view/as ... 01s08.html

Note, that the fully dark-adapted pupil size only gives you the exit pupil of the longest usable eyepiece focal length.
For other eyepieces there is no such formula, but "concentration" of the image (exit pupil) can be used for educated guess about a good compromise between image brightness and image size (details).
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Re: Need help with M4 in Scorpio

#14

Post by mikemarotta »


turboscrew wrote: Thu Jul 29, 2021 7:24 am There is this Allen key trick you can use to measure your pupil size - although, probably not fully dark-adapted.
Thanks! I went to the O'Reilly site and read the out-take from the book. The book looks interesting on it own merits, also. I did have to follow a different link to get the picture of Barbara using the Allen wrench. The verbal description was not clear to me. The picture made it obvious.

My backyard is never going to be fully dark, but the process can be helpful. And according to the motto of Faber College (from Animal House), "Knowledge is good."

Best Regards,
Mike M.
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Re: Need help with M4 in Scorpio

#15

Post by turboscrew »


mikemarotta wrote: Thu Jul 29, 2021 2:45 pm
turboscrew wrote: Thu Jul 29, 2021 7:24 am There is this Allen key trick you can use to measure your pupil size - although, probably not fully dark-adapted.
Thanks! I went to the O'Reilly site and read the out-take from the book. The book looks interesting on it own merits, also. I did have to follow a different link to get the picture of Barbara using the Allen wrench. The verbal description was not clear to me. The picture made it obvious.

My backyard is never going to be fully dark, but the process can be helpful. And according to the motto of Faber College (from Animal House), "Knowledge is good."

Best Regards,
Mike M.
I guess the actual largest pupil size when observing is more important than a "hypotethical" maximal pupil size, that never happens in actual observing.
- Juha

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Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5

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Re: Need help with M4 in Scorpio

#16

Post by mikemarotta »


Don Pensack wrote: Wed Jul 28, 2021 2:14 pm If the field is darker, it's because of magnification, not the number of glass elements in the focuser.
Thanks, again. I never noticed that. I never perceived the differences. The other night when I was going for the highest powers but using lower powers (32mm = 20x; 40mm = 16X) for locating, I saw how much brighter the background was.

On a related note, I was chatting on the phone with a friend who is an engineer and has been an amateur astronomer. We were talking about problem solving. In order for me to draw what I am looking at, I have to use words to describe the picture: ".... two triangles above an open space in the middle... the left star is about two-thirds larger ... " and so on. When I tried to draw intuitively, I had objects reversed or transposed and the relative scaling was off by too much.

So, anyway, thanks for the tip.
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Michael E. Marotta
Astro-Tech 115 mm APO Refractor Explore Scientific 102 mm f/6.47 Refractor Explore Scientific 102 mm f/9.8 Refractor Bresser 8-inch Newtonian Reflector Plössls from 40 to 6 mm Nagler Series-1 7mm. nonMeade 14 mm. Mounts: Celestron AVX, Explore Twilight I Alt-Az, Explore EXOS German Equatorial
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Re: Need help with M4 in Scorpio

#17

Post by mikemarotta »


I was reviewing my first log book (2014-2020) yesterday and found an entry indicating that I viewed M4. I was using a Celestron EQ-130, so 5 inches plus.

"Nebula between Antares and head" with sketch.

Also, over all, the neighborhood skies were more transparent five or six years ago. I have notes about the Milky Way which now is just a rumor. Unfortunately, my note taking was not as well developed. That,too, was a learning process. But here it is:
14 July 2015 B.jpeg
The line "light yellow/ deep yellow" refers to the Celestron filters. I used them all aggressively until late 2019 early 2020 and still used them on occasion until about October 2020.
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Michael E. Marotta
Astro-Tech 115 mm APO Refractor Explore Scientific 102 mm f/6.47 Refractor Explore Scientific 102 mm f/9.8 Refractor Bresser 8-inch Newtonian Reflector Plössls from 40 to 6 mm Nagler Series-1 7mm. nonMeade 14 mm. Mounts: Celestron AVX, Explore Twilight I Alt-Az, Explore EXOS German Equatorial
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Bigzmey United States of America
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Re: Need help with M4 in Scorpio

#18

Post by Bigzmey »


mikemarotta wrote: Wed Aug 04, 2021 2:15 pm Also, over all, the neighborhood skies were more transparent five or six years ago. I have notes about the Milky Way which now is just a rumor.
Same here, I was able to see Milky Way from the patio - not any more.
Scopes: Stellarvue: SV102ED; Celestron: 9.25" EdgeHD, 8" SCT, 150ST, Onyx 80ED; iOptron: Hankmeister 6" Mak; SW: 7" Mak; Meade: 80ST.
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.

Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2382, Comets: 34, Asteroids: 255
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Re: Need help with M4 in Scorpio

#19

Post by GCoyote »


Bigzmey wrote: Wed Aug 04, 2021 4:59 pm
mikemarotta wrote: Wed Aug 04, 2021 2:15 pm Also, over all, the neighborhood skies were more transparent five or six years ago. I have notes about the Milky Way which now is just a rumor.
Same here, I was able to see Milky Way from the patio - not any more.

Saw the Milky Way from the farm for the first time in many years. Pointing it out to my niece's son felt good.
Any metaphor will tear if stretched over too much reality.
Gary C

Celestron Astro Master 130mm f5 Newtonian GEM
Meade 114-EQ-DH f7.9 Newtonian w/ manual GEM
Bushnell 90mm f13.9 Catadioptric
Gskyer 80mm f5 Alt/Az refractor
Jason 10x50 Binoculars
Celestron 7x50 Binoculars
Svbony 2.1x42 Binoculars
(And a bunch of stuff I'm still trying to fix or find parts for.)
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