How many "South's" are there, and how do you properly find them?

[Lloyd-ss]

Hi everyone, total newbie here. I am a retired engineer and am learning all the new lingo. Some of it seems logical and makes perfectly good sense, but some of it is quite confusing and the explanations never really "click" in my brain.

Where I live (at Lat 38) my sky visibility to the north is very limited because of tall trees. But looking south, there is magnetic south, true south, solar south, polar south, and celestial south. And probably more, even though some of the ones I listed might be identical.

 

I think true south, polar south (the earths axis of rotation) and celestial south are all the same. Correct?

But what about solar south? I can find the exact time each day when solar south (the sun highest in the sky) is supposed to occur. This exact time varies across the 60 minute span of the time zone.  Is solar south always at AZ 180 degrees? Or does it vary throughout the year. I can stand a 4 foot carpenter's level vertical when the sun is at AZ180 and draw a line along it's shadow. Is this true south, or again, does it vary throughout the year. I seem to find conflict between various sites as to when solar south actually occurs. This does not help the confidence level at all. BTW, finding the North star in the forest where I live might not be possible, but I have not given it a 100% effort yet.

 

The carpenter's level method would be the easiest and most repeatable method for me right now. Can anyone help clear the fog in my head about this?

Thank you,

Lloyd

P.S. My first technical question!

[Nightspore]

Hello Lloyd, have a play with this. It might answer a lot of questions. There are freeware versions for Windows and Unix platforms. Also there is SkyPortal  for Android.

 

 

Edited January 3 by Nightspore
Universal translator malfunction

[Lloyd-ss]

Nightspore, I will check those out. A friend of mine might have had SkyPortal on their phone and it looked pretty cool. Although I am pretty comfortable around computers, I honestly was not prepared for how much software there is available for all aspects of this hobby. Just looking at the lists of features of the apps ans software, and the "new for this version" features, makes it look like, as you said, a lot of my questions will be answered. Thank You!

[Nightspore]

3 hours ago, Lloyd-ss said:

Nightspore, I will check those out. A friend of mine might have had SkyPortal on their phone and it looked pretty cool. Although I am pretty comfortable around computers, I honestly was not prepared for how much software there is available for all aspects of this hobby. Just looking at the lists of features of the apps ans software, and the "new for this version" features, makes it look like, as you said, a lot of my questions will be answered. Thank You!

 

Yeah, it's all a bit of  geekfest. I've run Stellarium since 2008, although sometimes on Windows it can be buggy. I usually run it on Ubuntu.

 

 

It runs really well on Linux and as it's a 'snap package' it automatically updates. I use SkySafari 7 on Chrome OS. I don't use a 'smartphone' so I have little experience with their software apps. I've used a fair few other astronomy apps for macOS and Ubuntu, but I always go back to Stellarium.

Edited January 4 by Nightspore
Universal translator malfunction

[TerryMcK]

17 hours ago, Lloyd-ss said:

I think true south, polar south (the earths axis of rotation) and celestial south are all the same. Correct?

Yes the south celestial pole is the point in the sky directly above Earth's southern axis. It's the point around which the entire southern sky appears to turn. The north and south celestial poles lie above Earth's north and south poles.

 

Magnetic south or magnetic north, of course, is where a compass needle points and is affected by the Earths internally generated magnetic field. it is not a fixed point. Here in the UK, the magnetic North Pole has been positioned slightly to the west of true north for hundreds of years. However, its position is constantly changing and magnetic north and true north will eventually align. Then it will go east of north. This cycle has been going on for millions of years and is shown in the magnetic fossil records. Have a search on the internet for Paleomagnetism.

This explains it more.

https://www.usgs.gov/educational-resources/magnetic-declination-varies-considerably-across-united-states#:~:text=The Geographic North Pole is,to as "True North."

 

Solar south is only really relevant if you are fitting solar panels to make sure you are maximizing light falling on them and isn't a term used in astronomy. A quick Google came up with this

"The sweet spot for solar panels in the continental U.S. is facing roughly south, tilted between 15 and 40 degrees, according to the Department of Energy. That keeps the panels in the sun longer than other setups—which means more electricity per panel per year, and bigger savings on your utility bills"

[GazAstro]

Nightspore (not sure of your name)and Terry have given great answers, just to point out that with your mount (manual dob) you don't really need to know where true North or South are, that's mainly for long exposure imaging.

Your carpenters level will give a good enough idea and combined with a sky map or app (I use SkySafari and love it on Android) will be enough to help you find things to look at.

[Lloyd-ss]

Gentlemen, thank you for helping to clarify some of the terminology. Some of my interest in the terminology is because I am working on a equatorial platform to place the Dob-based Orion XT6 on. I have a "need" to build things that help with a hobby. Otherwise it can get stale. Just part of my weirdness. At least my wife understands and tolerates it.

 

As I learn more, I see that I must adjust my questions, like the one about solar south. Because I have not learned the constellations yet, while looking at some books and websites, I see that the locations of celestial features/bodies are usually located by DEC-RA, and sometimes by ALT-AZ (along with the local time).

 

Please humor me as I write out my current understanding of the terms, and correct me as needed.

The ALT-AZ-Time method of location seems logical, I am familiar with  ALT-AZ already, and it is easy. It works for all celestial bodies, including the planets that circle the sun (which have their own nomenclature) so long as "TIME" is included.

So, ALT-AZ-Time, I think I have straight in my head. The ALT plane is a level plane at a specific location, and the AZ axis is a perpendicular line that passes thru the ALT zero plane. So the ALT zero plane, and the AZ axis (180 is due south) are unique to every location, but never vary at that location. Alt-Az seems more suited to artillery emplacements than to celestial viewing. (Comments are welcome)

 

But, DEC-RA is confusing, particularly the RA part. That has not yet clicked in my brain. Because the DEC-RA location (coordinates) of a celestial body are the same no matter where you are on the earth, then, apparently, The DEC zero plane, and the RA axis and also its "zero hour" direction must be different at each location. And also, the zero hour location of the RA axis must vary to counteract the rotation of the earth. 

So, the DEC zero plane and RA axis are fixed in relation to the celestial sphere, and the ALT-AZ reference plane and axis are fixed in relation to the earth (earth centric??) (Comments are welcome.)

 

Thank you for helping me understand these somewhat confusing terms.

 

As an aside, but totally relevant to the topic: Years ago, I was taking an after-hours course on the theory of the gyro compass (invented by Elmer Sperry around 1900). It was actually quite complicated with lots of 3 dimensional trig and compensation for movement around the globe. The first "wake-up", "light bulb", "hit me in the head with a 2x4", moment was the statement that a spinning mass gyro always points to the same place in the universe, and NOT to the same place on the globe. Therefore, as the gyro compass moves around the globe it must constantly compensate its spinning axis from a fixed point in the universe to a direction that is relative to the earth.

 

It was difficult to understand back then, and it still is, LOL. 🤔

Thanks,

Lloyd

 

 

 

 

[Nightspore]

I believe you may be overthinking this a bit Lloyd. If you really want to understand Right Ascension play around with Stellarium (or a similar program) for a while. Particularly speeding it up a little so you can see the stars (and planets) move in realtime, and then faster than realtime (it's really trippy lol). It will give you a graphic representation of how the Earth's rotation affects what we can see in the night sky. Mostly we don't immediately notice RA, but with only a slight magnification on the naked eye the Earth's axial rotation (1669 KPH @ equator) becomes evident. I tend to find with my EQ5 when planetary observing I occasionally have to adjust the mount declination slo mo cable (shown slightly to the left of the OTA below).

 

 

This is most probably attributed to the fact that I haven't centred Polaris precisely with the mount's internal sighting scope.

 

 

Viewing the Polaris area through the eyepiece of the mount sighting scope (above) 

 

 

Please ignore the red arrow pointing to the clutch lock. The circular aperture to the right of the lock should be pointing directly at Polaris. Although in reality, it probably isn't. This is possibly due to ground subsidence or shifting of the tripod. Mainly I suspect that I'm not really that accurate in setting-up the original graticule sighting. 

 

 

Which is why I invested in this right-angled polar eyepiece (with graticule). However, the declination isn't always perfect when actually physically tracking in RA, requiring occasional adjustment. I suspect that this is because this is a manual instrument set-up by an idiot who also has a physical disability lol. 

 

 

Above: OTA (GSO 150mm Newtonian) pointing around 45-50 degrees declination due south, note where the counter-balancing weight is respective to the OTA.

 

 

Above: same set-up pointing low into the west. Please ignore the black metal cat silhouettes, designed to deter certain annoying felines from using my observatory as a toilet. 

 

 

Above: My old 130mm Synta Newtonian pointing roughly to the east (EQ2 mount), note counterweight position.

 

 

Above: Right Ascension slo mo knob (GSO 150mm), which replaced the RA cable. The knob is more convenient for me than a cable. I can reach it quite easily with my left hand while seated for plane of the ecliptic (lunar/planetary) observing.  West and east are not too difficult for me either, although north is not particularly easy. Hence why the scope mount/tripod is situated at the extreme north of my garden. This was particularly useful in the past few years with the planets being low in the plane of the ecliptic. Fortunately they are now getting much higher. Australian and Kiwi astronomers tell me the planets are now gradually getting lower for them after almost being near the zenith for a while. 

 

 

Above: 'Bird's eye' view of 150mm mirror facing south. Red arrow again pointing to Polaris (hopefully lol).

 

 

You can see why I prefer alt-az mounts now ROTFL!

Edited January 5 by Nightspore
reasons

[Lloyd-ss]

4 hours ago, Nightspore said:

I believe you may be overthinking this a bit Lloyd. If you really want to understand Right Ascension play around with Stellarium (or a similar program) for a while. Particularly speeding it up a little so you can see the stars (and planets) move in realtime, and then faster than realtime (it's really trippy lol). It will give you a graphic representation of how the Earth's rotation affects what we can see in the night sky. Mostly we don't immediately notice RA, but with only a slight magnification on the naked eye the Earth's axial rotation (1669 KPH @ equator) becomes evident. I tend to find with my EQ5 when planetary observing I occasionally have to adjust the mount declination slo mo cable (shown slightly to the left of the OTA below).

 

 

This is most probably attributed to the fact that I haven't centred Polaris precisely with the mount's internal sighting scope.

 

 

Viewing the Polaris area through the eyepiece of the mount sighting scope (above) 

 

 

Please ignore the red arrow pointing to the clutch lock. The circular aperture to the right of the lock should be pointing directly at Polaris. Although in reality, it probably isn't. This is possibly due to ground subsidence or shifting of the tripod. Mainly I suspect that I'm not really that accurate in setting-up the original graticule sighting. 

 

 

Which is why I invested in this right-angled polar eyepiece (with graticule). However, the declination isn't always perfect when actually physically tracking in RA, requiring occasional adjustment. I suspect that this is because this is a manual instrument set-up by an idiot who also has a physical disability lol. 

 

 

Above: OTA (GSO 150mm Newtonian) pointing around 45-50 degrees declination due south, note where the counter-balancing weight is respective to the OTA.

 

 

Above: same set-up pointing low into the west. Please ignore the black metal cat silhouettes, designed to deter certain annoying felines from using my observatory as a toilet. 

 

 

Above: My old 130mm Synta Newtonian pointing roughly to the east (EQ2 mount), note counterweight position.

 

 

Above: Right Ascension slo mo knob (GSO 150mm), which replaced the RA cable. The knob is more convenient for me than a cable. I can reach it quite easily with my left hand while seated for plane of the ecliptic (lunar/planetary) observing.  West and east are not too difficult for me either, although north is not particularly easy. Hence why the scope mount/tripod is situated at the extreme north of my garden. This was particularly useful in the past few years with the planets being low in the plane of the ecliptic. Fortunately they are now getting much higher. Australian and Kiwi astronomers tell me the planets are now gradually getting lower for them after almost being near the zenith for a while. 

 

 

Above: 'Bird's eye' view of 150mm mirror facing south. Red arrow again pointing to Polaris (hopefully lol).

 

 

You can see why I prefer alt-az mounts now ROTFL!

 

"Maybe overthinking it a bit."  Yup, no argument there. That's my nature, but I will back off shortly. I often, unwisely, want to learn everything right away so that I don't do anything wrong.  But I realize that the only thing I can REALLY do wrong is spend a bunch of money right away on the wrong goodies. Trust me, I won't do that. I have some books and the info on the forum, and will get Stellarium going like you have suggested. I don't know if it is a saying in the UK, but from the US, I will be hoping that you folks, "will keep me out of the ditch."

Thanks,

Lloyd

[Nightspore]

1 hour ago, Lloyd-ss said:

 

"Maybe overthinking it a bit."  Yup, no argument there. That's my nature, but I will back off shortly. I often, unwisely, want to learn everything right away so that I don't do anything wrong.  But I realize that the only thing I can REALLY do wrong is spend a bunch of money right away on the wrong goodies. Trust me, I won't do that. I have some books and the info on the forum, and will get Stellarium going like you have suggested. I don't know if it is a saying in the UK, but from the US, I will be hoping that you folks, "will keep me out of the ditch."

Thanks,

Lloyd

 

That's a wise approach. Spending way too many spondoolies on gear you rarely or ever use is par for the course. It's basically the default mode for amateur astronomers. We've all been there. Wait until you start buying eyepieces. There's only so much that you can learn purely in theory though, and much of it is personal preference. I wish I'd had 'hindsight binoculars' years ago lol. I bought this comparatively well priced  72mm, f/5,8 Synta (Sky-Watcher Evostar 72ED DS PRO rev #1) semi-apo doublet around five years ago. The doublet itself is very well colour corrected compared to the ST80 it more or less replaced. Although it has a Schott 'crown' the 'flint' element is not quite as good as the SFPL-53 glass of my Altair and Evostar ED80 refractors. My guess is that it is some Chinese FPL-51 equivalent. Synta aren't admitting what it really is. It is very good though. As a consequence (and taking my disability into account) it is actually annually my most used scope.

 

 

Many amateur astronomers have more than one 'rig'. Usually a larger aperture main scope, and a smaller grab and go scope. I'd recommend a refractor for the latter.

 

 

You'll most probably learn the sky more with the smaller, more portable scope.

 

 

Don't let size fool you.

 

 

Incidentally; usually the J, K & L keyboard buttons change the speed of Stellarium, and the 8 key should bring it back to 'now' in your local time. EG, press the L key three or four times to vary speed into the future, K will stop it. 8 will bring it back to the present. It may take a bit of practice. Good luck and clear skies.

[Graeme]

We all had to scratch out heads with this one initially! The main difference between Alt-Az and RA-Dec is that RA-Dec is a fixed coordinate system that is fixed for each and every celestial object. The coordinates for Vega for instance are 18 hours 36 minutes RA and 38° 47' Dec, that's the figure that's always quoted for Vega's location in the sky. But the earth orbits the Sun and spins on its axis in constant motion which is why Alt-Az coordinates constantly change with respect to time. So in order to know where Vega actually is you need to convert RA-Dec to Alt-Az as a function of the date, time and your current location. So for me, here where I am, this morning, right now, Vega is 48° 20' up from the horizon and 17° 30' clockwise from due North. 

 

Graeme