[MossyRocks]

Next question would be, If I am using a 28mm on a 1.5 crop sensor, does the 0-gps-1 take that into account ?

Yes it wants the real actual focal length

or should I set the focal length to the 35mm equivalent, say 42mm ?

No you will end up with trails

I understand the unit was not meant for more than a 200mm lens.

that may be the case but I've gotten good results with a 300mm and 400mm lens on it and after about 600mm I would be hard pressed to make effective use of it.


As far as things affecting it's tracking I would look more to things that throw the compass off. Electric field from power lines either buried or over head, transformers, electric motors, being right next to a pile of iron like in a fence or your vehicle, soil that has an excessive amount of iron in in like up in the iron range of MN. Other than that getting it correctly calibrated takes practice, smoothness of the rotations and keeping each one limited to one axis at a time is key. Also it doesn't hurt to go past 180 total in each direction.

Yes it wants the real actual focal length


No you will end up with trails


that may be the case but I've gotten good results with a 300mm and 400mm lens on it and after about 600mm I would be hard pressed to make effective use of it.


As far as things affecting it's tracking I would look more to things that throw the compass off. Electric field from power lines either buried or over head, transformers, electric motors, being right next to a pile of iron like in a fence or your vehicle, soil that has an excessive amount of iron in in like up in the iron range of MN. Other than that getting it correctly calibrated takes practice, smoothness of the rotations and keeping each one limited to one axis at a time is key. Also it doesn't hurt to go past 180 total in each direction.

I do go over 180 each direction, but, the car is 15 ft away, so perhaps that. powerlines are about 100 ft away, no avoiding that here. Florida likely has little iron in the sane, I suspect more iron in the locals lol.
Finding a place where there are no powerlines around here means going somewhere unsafe, least in my neighbourhood.
What distance do you think I should be from a power line or car ?
I will drive the area and see if I can find an alternate location that is safer with no lines and little light..

[MossyRocks]

I do go over 180 each direction, but, the car is 15 ft away, so perhaps that. powerlines are about 100 ft away, no avoiding that here.

I would probably see about going farther from the car I usually set up at least 30 feet from it probably closer to 45. As far as power lines go I try to get as far as I can, especially high voltage one. One night I setup right on top of a buried one and couldn't get a good calibration, it wasn't until the morning when I found out why seeing the the 2 transformers on either side of me off in the weeds with my big tripod right on top of the line between them.

I will drive the area and see if I can find an alternate location that is safer with no lines and little light..

Parking lots for parks and sports fields are great locations. When I say I am out in my backyard shooting I really mean I am standing out in the baseball field in the park behind my house. I know most of my cities cops and they don't care as the person with thousands of dollars of camera gear isn't the one going to cause problems. The darkest spot in the entire metro area is one of the parking lots in a county park and I have permission to setup and use it all hours. The nice thing there is the park is well off the beaten path so it keeps others away and has some fairly dark skies (dark bortle 5)

I would probably see about going farther from the car I usually set up at least 30 feet from it probably closer to 45. As far as power lines go I try to get as far as I can, especially high voltage one. One night I setup right on top of a buried one and couldn't get a good calibration, it wasn't until the morning when I found out why seeing the the 2 transformers on either side of me off in the weeds with my big tripod right on top of the line between them.


Parking lots for parks and sports fields are great locations. When I say I am out in my backyard shooting I really mean I am standing out in the baseball field in the park behind my house. I know most of my cities cops and they don't care as the person with thousands of dollars of camera gear isn't the one going to cause problems. The darkest spot in the entire metro area is one of the parking lots in a county park and I have permission to setup and use it all hours. The nice thing there is the park is well off the beaten path so it keeps others away and has some fairly dark skies (dark bortle 5)

we hav a football field at the court house next to the Police Dept, but the lighting is blinding.

---------- Post added 03-09-20 at 07:09 PM ----------

The calibration is for determining local magnetic north so an offset can be applied to your magnetic variation based on what it should be for your lat and long determined from the GPS. For a given focal length, the relative velocity of the starfield will determine exposure limits for the O-GPS unit. The celestial equator cuts through Orion so it will have the least relative rotation across the frame but the fastest star speed. Likewise at the celestial poles, rotational speed will be highest and transverse speed the lowest. Since the O-GPS has limited ability to track rotational movement, high celestial elevations will be difficult for it to track. Thus, there is a sweet spot at about 45 degrees where transverse and rotational speed tradeoffs are at a minimum.

"For a given focal length, the relative velocity of the starfield will determine exposure limits for the O-GPS unit."

But then again the old lens does not report its focal length, well at least it didnt used to lol, now it seems to accept input.

---------- Post added 03-09-20 at 07:14 PM ----------

As far as I know, astrotracer doesn't do this...Exposure time works the same way as it does with or without it. It's controlled by the shutter release, which you handle manually in M or B mode. You are free to expose as long as you want no matter the focal length of your lens. Because of the limits in what astrotracer does, that is a shorter time for longer lenses, but that time is not something that is internally controlled. And whether or not you get trails for a given time length does vary based on the elevation and how good your calibration is. That's largely unrelated to the lens, and in fact will vary between sessions using the same lens.

But the time is repoted as being the longest time for exposure, so I would say that is a control. granted I can use a release cord and turn off timed exposure and go past the limit, or perhaps it will simply stop exposure when the time limit is reached. And that time limit changes with the focal length of the lens to a degree. 5 minutes for the 28mm and the 100mm, but 2 for the 300. How does it know.

---------- Post added 03-09-20 at 07:17 PM ----------

Yes it wants the real actual focal length


No you will end up with trails


that may be the case but I've gotten good results with a 300mm and 400mm lens on it and after about 600mm I would be hard pressed to make effective use of it.


As far as things affecting it's tracking I would look more to things that throw the compass off. Electric field from power lines either buried or over head, transformers, electric motors, being right next to a pile of iron like in a fence or your vehicle, soil that has an excessive amount of iron in in like up in the iron range of MN. Other than that getting it correctly calibrated takes practice, smoothness of the rotations and keeping each one limited to one axis at a time is key. Also it doesn't hurt to go past 180 total in each direction.

Oh BTW. I read an article today on calibrating this thing, and they suggested going 360 degrees. starting will roll, then pitch , and finally Yaw.
Getting a calibration OK used to take a minute or so facing north, Today I got the OK after 20 seconds or so by doing it 360 degrees.
But man is that a pain with a large strap attached lol.
IF we ever see the sky again I will test that out.

---------- Post added 03-09-20 at 07:23 PM ----------

The calibration is for determining local magnetic north so an offset can be applied to your magnetic variation based on what it should be for your lat and long determined from the GPS. For a given focal length, the relative velocity of the starfield will determine exposure limits for the O-GPS unit. The celestial equator cuts through Orion so it will have the least relative rotation across the frame but the fastest star speed. Likewise at the celestial poles, rotational speed will be highest and transverse speed the lowest. Since the O-GPS has limited ability to track rotational movement, high celestial elevations will be difficult for it to track. Thus, there is a sweet spot at about 45 degrees where transverse and rotational speed tradeoffs are at a minimum.

by sweet spot you are saying thats the area where I am likely to get trails because of its unique position in the sky ?

Obviously Orion is the go to shot for a close nebula, a shame it also has to be the fastest star movement. However if I were to shoot when it is say 20 degrees position I would have better luck ?

[MossyRocks]

However if I were to shoot when it is say 20 degrees position I would have better luck ?

Nope. Anything along the celestial equator will have the highest linear speed (angular speed is the same) and things closest to the celestial poles will have the slowest. Unfortunately orion is very close to the celestial equator and if you look at the star trail pictures in either of those articles you can see how much longer the trails are as you move away from the celestial pole eventhough the angular length of each star trail in the frame is the same. If you look at Ricoh's specifications for the O-GPS1 for how well astrotracer can perform the declination they are talking about is for stellar coordinates. So pointing at either celestial pole will give you the most time and is limited by how much the sensor can rotate and an acceptable amount of trailing (this is why you get the 5 minute upper limit) and focal length has very little affect here. If pointing it at something on the celestial equator the x/y movement ends up being your limiting factor but here focal length has a much greater effect since the movement appears to be almost entirely linear.

If you want to find out more you can read up on the equatorial celestial coordinate system which should help you understand things more.

we hav a football field at the court house next to the Police Dept, but the lighting is blinding.

See if you can get permission to go out late at night after the lights are off. The worst they can say is no and then you are stuck in the same position you currently are so it can only improve you situation.

But the time is repoted as being the longest time for exposure, so I would say that is a control. granted I can use a release cord and turn off timed exposure and go past the limit, or perhaps it will simply stop exposure when the time limit is reached. And that time limit changes with the focal length of the lens to a degree. 5 minutes for the 28mm and the 100mm, but 2 for the 300. How does it know.

I have no idea what happens if you do a manual bulb mode exposure for longer than astrotracer's optimistic guess. Since that guess is based on long it would take the sensor to move the maximum distance from the zero position I would assume it would stop tracking. Thus you would have some bright points followed by some dimmer trails. However I have never achieved maximum tracking time and more often find that their suggestion is usually 2 to 4 times to long. I will usually start off with 1/4 the time and see if I have nice point stars and if I do increase from there. For the lenses I use most I know what I should be getting when pointing at things so I just calibrate until I get the results I want. Only twice have I gotten what I wanted on the first try with most nights requiring 3 to 5 attempts.

Nope. Anything along the celestial equator will have the highest linear speed (angular speed is the same) and things closest to the celestial poles will have the slowest. Unfortunately orion is very close to the celestial equator and if you look at the star trail pictures in either of those articles you can see how much longer the trails are as you move away from the celestial pole eventhough the angular length of each star trail in the frame is the same. If you look at Ricoh's specifications for the O-GPS1 for how well astrotracer can perform the declination they are talking about is for stellar coordinates. So pointing at either celestial pole will give you the most time and is limited by how much the sensor can rotate and an acceptable amount of trailing (this is why you get the 5 minute upper limit) and focal length has very little affect here. If pointing it at something on the celestial equator the x/y movement ends up being your limiting factor but here focal length has a much greater effect since the movement appears to be almost entirely linear.

If you want to find out more you can read up on the equatorial celestial coordinate system which should help you understand things more.



See if you can get permission to go out late at night after the lights are off. The worst they can say is no and then you are stuck in the same position you currently are so it can only improve you situation.



I have no idea what happens if you do a manual bulb mode exposure for longer than astrotracer's optimistic guess. Since that guess is based on long it would take the sensor to move the maximum distance from the zero position I would assume it would stop tracking. Thus you would have some bright points followed by some dimmer trails. However I have never achieved maximum tracking time and more often find that their suggestion is usually 2 to 4 times to long. I will usually start off with 1/4 the time and see if I have nice point stars and if I do increase from there. For the lenses I use most I know what I should be getting when pointing at things so I just calibrate until I get the results I want. Only twice have I gotten what I wanted on the first try with most nights requiring 3 to 5 attempts.

I will definately read up at that link. I am sure most of it will go over my head, but I will read it over and over lol.
Before the clouds rolled in I had about 10 minutes to try the 360 degree calibration and take a few shots with the 28mm.
It actually did ok on orion, although to small to use, and straight up even better at 40 seconds. I calibrated facing North.,
Oddly enough I was never able to complete all the required movements for the calibration before I got a Complete notice.

Nope. Anything along the celestial equator will have the highest linear speed (angular speed is the same) and things closest to the celestial poles will have the slowest. Unfortunately orion is very close to the celestial equator and if you look at the star trail pictures in either of those articles you can see how much longer the trails are as you move away from the celestial pole eventhough the angular length of each star trail in the frame is the same. If you look at Ricoh's specifications for the O-GPS1 for how well astrotracer can perform the declination they are talking about is for stellar coordinates. So pointing at either celestial pole will give you the most time and is limited by how much the sensor can rotate and an acceptable amount of trailing (this is why you get the 5 minute upper limit) and focal length has very little affect here. If pointing it at something on the celestial equator the x/y movement ends up being your limiting factor but here focal length has a much greater effect since the movement appears to be almost entirely linear.

If you want to find out more you can read up on the equatorial celestial coordinate system which should help you understand things more.



See if you can get permission to go out late at night after the lights are off. The worst they can say is no and then you are stuck in the same position you currently are so it can only improve you situation.



I have no idea what happens if you do a manual bulb mode exposure for longer than astrotracer's optimistic guess. Since that guess is based on long it would take the sensor to move the maximum distance from the zero position I would assume it would stop tracking. Thus you would have some bright points followed by some dimmer trails. However I have never achieved maximum tracking time and more often find that their suggestion is usually 2 to 4 times to long. I will usually start off with 1/4 the time and see if I have nice point stars and if I do increase from there. For the lenses I use most I know what I should be getting when pointing at things so I just calibrate until I get the results I want. Only twice have I gotten what I wanted on the first try with most nights requiring 3 to 5 attempts.

OK read it, totally befuddled lol. kinda. It seems that as we rotate on an exis and that tilt changes that there would be a time when Orion is more able to be photographed.
So many others can get long exposures without trails so I have to wonder if it is my geographical location that is the issue, or the time of the evening I am taking the shots.
I get better shots near the horizon and straight up. but in between those 2 areas I have trailing issues.
We have an entire week forecast to be pretty much solid clouds after sunset and during the day, so it might be a while before I get to do more testing.
I will read that link again, and also check for other online examples that may be more understandable to me.

---------- Post added 03-10-20 at 07:07 AM ----------

Nope. Anything along the celestial equator will have the highest linear speed (angular speed is the same) and things closest to the celestial poles will have the slowest. Unfortunately orion is very close to the celestial equator and if you look at the star trail pictures in either of those articles you can see how much longer the trails are as you move away from the celestial pole eventhough the angular length of each star trail in the frame is the same. If you look at Ricoh's specifications for the O-GPS1 for how well astrotracer can perform the declination they are talking about is for stellar coordinates. So pointing at either celestial pole will give you the most time and is limited by how much the sensor can rotate and an acceptable amount of trailing (this is why you get the 5 minute upper limit) and focal length has very little affect here. If pointing it at something on the celestial equator the x/y movement ends up being your limiting factor but here focal length has a much greater effect since the movement appears to be almost entirely linear.

If you want to find out more you can read up on the equatorial celestial coordinate system which should help you understand things more.



See if you can get permission to go out late at night after the lights are off. The worst they can say is no and then you are stuck in the same position you currently are so it can only improve you situation.



I have no idea what happens if you do a manual bulb mode exposure for longer than astrotracer's optimistic guess. Since that guess is based on long it would take the sensor to move the maximum distance from the zero position I would assume it would stop tracking. Thus you would have some bright points followed by some dimmer trails. However I have never achieved maximum tracking time and more often find that their suggestion is usually 2 to 4 times to long. I will usually start off with 1/4 the time and see if I have nice point stars and if I do increase from there. For the lenses I use most I know what I should be getting when pointing at things so I just calibrate until I get the results I want. Only twice have I gotten what I wanted on the first try with most nights requiring 3 to 5 attempts.

ok I read this
Astronomy Without a Telescope

makes more sense top me for some reason. And from what you have said 90 degrees is straight up " zenith", CNP is the opposite from where I am in Latitude from zenith.
Celestial equator is horizon or 90 degrees from CNP and crosses terrestrial horizon. Sp traveling a longer arc at Celestial equator means those stars seem to have a faster speed than do those at CNP. So I am guessing some times of the year when Orion is at its highest point is the best time to photograph . I hope that's right. lol.
But the GPS specs seem to say the opposite in regards to exposure time.
I apologize if you feel you are talking to a rock.

---

Last edited by dewolf; 03-10-2020 at 04:27 AM. Reason: addendum

[MossyRocks]

Oddly enough I was never able to complete all the required movements for the calibration before I got a Complete notice.

I get that fairly frequently. I find it mostly happens when the movements aren't restricted to one axis but also when there are things that have a large effect on the electronic compass . If I have a calibration that finishes before I have gone through all 3 motionsI assume it is bad. I also make sure to do a regular calibration and a precise calibration each time.

And from what you have said 90 degrees is straight up " zenith", CNP is the opposite from where I am in Latitude from zenith.

Not really. Where I am CNP is about 45 degrees from the horizon when facing towards true north (which for me happens to be well within 1 degree of magnetic north at the moment). The only time the CNP would be at the zenith is if you were actually at the north pole. For the purposes of human time scales stars all have a fixed position using equatorial celestial coordinates. The declenation portion is a measure of how far they are from the celestial equator and the closer to the celestial equator something is the higher linear speed it has. This linear speed is the same all the time regardless of the time of year or one's position on earth. Polaris or the north star is basically at +90 for declination (it is actually about 1 degree from it) and being right at the celestial north pole it;'s right ascension is basically meaningless. However the great Orion nebula (M42) has a declination of about -5.5 degrees or being 5.5 degrees south of the celestial equator so it is basically on the celestial equator and as such has a huge linear speed across the sky. While it's declination is fixed it's height in the nigh sky varies over the course of a day and for me with my approximate 45N latitude it would get to about 40 degrees above my physical horizon but is will always be that 5.5 degrees below the celestial equator.

But the GPS specs seem to say the opposite in regards to exposure time.

Nope. The O-GPS1 talks about declination not latitude or zenith so a 90 degree declination means point it at the celestial north pole, a 0 degree declination means pointing it at the celestial equator, and -90 degree declination means pointing it at the celestial south pole.

If you really want to get a handle on where things are and get your bearings when looking at the night sky I suggest getting a cellphone planetarium app. For free ones I like Sky Safari as it has a more complete catalog of objects than others and if you want to pay you can go ad free. You can have it show the equatorial celestial coordinate grid and also make use of the compass and tilt features in your phone to show you what you are looking at. If you want a program to use on your computer a really good one is Stellarium which has tons of objects in various catalogs you can load.

I apologize if you feel you are talking to a rock.

Everyone has to start somewhere, I was a beginner at one point as was everyone else.

[photoptimist]

I know a lot of the star trailing issue is location and how many satellites you can receive. I usually get 10 satellites on precision calibration. But I still get considerable trailing with a 300mm at 10 seconds, while others are getting no trails at 20 seconds.

Actually, the quality of the GPS signal really doesn't affect astrotracer that much. GPS could be off by hundreds of meters and it wouldn't cause star trailing.

The weakest part of the astrotracer system is the quality of the magnetic compass reading. GPS provides the location but gives no clue on which way the camera is pointing. The camera's accelerometers can provide the up/down elevation angle for the pointing direction but provides no data on whether the camera is pointed East (the stars are rising), West (the stars are falling), North (the stars are rotating counterclockwise), or south (the stars are rotating clockwise). Roughly speaking, a magnetic compass error of only 1° would have the same effect as a GPS location error of 100 kilometers!

Some locations are a problem due to nearby iron (pipes, structures, or ore) or strong electric fields (power lines, industrial equipment) that distort the Earth's magnetic field or scramble the compass reading.

But the more likely issue might be your tripod or maybe a lens that has lots of steel or has something magnetized. You can check this with an ordinary compass -- seeing if the needle deflects when it's brought near the lens or tripod. If the lens or tripod aren't too strongly magnetic, then the calibration where you rotate the whole thing (the camera + lens you plan to use + tripod you plan to use) around three different axes might be able to correct for the distorted field and get less star trailing.

[MossyRocks]

But the more likely issue might be your tripod or maybe a lens that has lots of steel or has something magnetized.

The benefit of having a wooden or aluminum tripod. I guess I've never thought about that being an issue as it is one I've avoided entirely by accident.

Actually, the quality of the GPS signal really doesn't affect astrotracer that much. GPS could be off by hundreds of meters and it wouldn't cause star trailing.

I would think that being off by miles or even a few tens of miles wouldn't be an issue since you would be dealing with small fractions of a degree. Even then error only in the north/south direction would affect it. However one thing I had issues with was my recently acquired K-3ii and that one of the electronic level sensors was off so where the camera thought it was point wasn't even close to where it actually was. By dumb luck the test shot I took was correct enough to not shot error but when reorienting the camera to the portraits position the level sensor indicating up and down in that position was off by close to 20 degrees. I lucked out on that used gear in that it had a 6 month warranty from the shop so I was able to make it their problem and they sent it off to Precision for service. Got it back and things are better now.

I get that fairly frequently. I find it mostly happens when the movements aren't restricted to one axis but also when there are things that have a large effect on the electronic compass . If I have a calibration that finishes before I have gone through all 3 motionsI assume it is bad. I also make sure to do a regular calibration and a precise calibration each time.


Not really. Where I am CNP is about 45 degrees from the horizon when facing towards true north (which for me happens to be well within 1 degree of magnetic north at the moment). The only time the CNP would be at the zenith is if you were actually at the north pole. For the purposes of human time scales stars all have a fixed position using equatorial celestial coordinates. The declenation portion is a measure of how far they are from the celestial equator and the closer to the celestial equator something is the higher linear speed it has. This linear speed is the same all the time regardless of the time of year or one's position on earth. Polaris or the north star is basically at +90 for declination (it is actually about 1 degree from it) and being right at the celestial north pole it;'s right ascension is basically meaningless. However the great Orion nebula (M42) has a declination of about -5.5 degrees or being 5.5 degrees south of the celestial equator so it is basically on the celestial equator and as such has a huge linear speed across the sky. While it's declination is fixed it's height in the nigh sky varies over the course of a day and for me with my approximate 45N latitude it would get to about 40 degrees above my physical horizon but is will always be that 5.5 degrees below the celestial equator.



If you really want to get a handle on where things are and get your bearings when looking at the night sky I suggest getting a cellphone planetarium app. For free ones I like Sky Safari as it has a more complete catalog of objects than others and if you want to pay you can go ad free. You can have it show the equatorial celestial coordinate grid and also make use of the compass and tilt features in your phone to show you what you are looking at. If you want a program to use on your computer a really good one is Stellarium which has tons of objects in various catalogs you can load.


Everyone has to start somewhere, I was a beginner at one point as was everyone else.

OK so wherever CNP is at my location, it will move 1 degree away from its present location to the zenith for every degree I move the opposite direction.

I did 4 calibrations today, North, South East and West taking a picture after each calibration.
I do this because Exiftool will show the GPS data.

Number of satellites located after calibration to the north = 6, south = 7 east = 8, and west = 9.

Here is what the data looks like if this is of help.
Note, lines 16-17 seem inaccurate.

This is North

GPS Version ID : 2.3.0.0
GPS Latitude Ref : North
GPS Latitude : 27.086698°
GPS Longitude Ref : West
GPS Longitude : 82.212920°
GPS Altitude Ref : Above Sea Level
GPS Altitude : 13 m
GPS Time Stamp : 18:57:40
GPS Satellites : 06
GPS Status : Measurement Active
GPS Measure Mode : 3-Dimensional Measurement
GPS Speed Ref : km/h
GPS Speed : 0.35
GPS Track Ref : True North
GPS Track : 0
GPS Img Direction Ref : True North
GPS Img Direction : 0.15
GPS Map Datum : WGS-84
GPS Processing Method : GPS
GPS Date Stamp : 2020:03:10


and this is South

GPS Version ID : 2.3.0.0
GPS Latitude Ref : North
GPS Latitude : 27.086658°
GPS Longitude Ref : West
GPS Longitude : 82.212863°
GPS Altitude Ref : Above Sea Level
GPS Altitude : 12.7 m
GPS Time Stamp : 18:59:10
GPS Satellites : 07
GPS Status : Measurement Active
GPS Measure Mode : 3-Dimensional Measurement
GPS Speed Ref : km/h
GPS Speed : 0.81
GPS Track Ref : True North
GPS Track : 6.14
GPS Img Direction Ref : True North
GPS Img Direction : 183.5
GPS Map Datum : WGS-84
GPS Processing Method : GPS
GPS Date Stamp : 2020:03:10

---------- Post added 03-10-20 at 03:38 PM ----------

Actually, the quality of the GPS signal really doesn't affect astrotracer that much. GPS could be off by hundreds of meters and it wouldn't cause star trailing.

The weakest part of the astrotracer system is the quality of the magnetic compass reading. GPS provides the location but gives no clue on which way the camera is pointing. The camera's accelerometers can provide the up/down elevation angle for the pointing direction but provides no data on whether the camera is pointed East (the stars are rising), West (the stars are falling), North (the stars are rotating counterclockwise), or south (the stars are rotating clockwise). Roughly speaking, a magnetic compass error of only 1° would have the same effect as a GPS location error of 100 kilometers!

Some locations are a problem due to nearby iron (pipes, structures, or ore) or strong electric fields (power lines, industrial equipment) that distort the Earth's magnetic field or scramble the compass reading.

But the more likely issue might be your tripod or maybe a lens that has lots of steel or has something magnetized. You can check this with an ordinary compass -- seeing if the needle deflects when it's brought near the lens or tripod. If the lens or tripod aren't too strongly magnetic, then the calibration where you rotate the whole thing (the camera + lens you plan to use + tripod you plan to use) around three different axes might be able to correct for the distorted field and get less star trailing.

The smaller lens, 28mm is likely steel, everything else is aluminium as is the tripod .

[MossyRocks]

OK so wherever CNP is at my location, it will move 1 degree away from its present location to the zenith for every degree I move the opposite direction.

Now that I see your location (or a close enough approximation of it) the celestial north pole would be at about 27 degrees up from the horizon if you are facing due north (likely not magnetic north). If you have a clear night look here and you will find the Polaris/ the north star. If you have never found the north star the line that makes up the far edge of the big dipper points to it. For every degree that you head north Polaris will be 1 degree higher in the sky, until you reach the north pole when it will be directly over head.

Assuming you have correctly calibrated things and were properly pointed in the correct directions you say you were it looks like it would be fairly accurate. The magnetic declination where you are is almost 6 degrees W so if you were out with an old magnetic compass you would have to correct for that but don't know how you determined that you were pointing due north or due south but those numbers look to be within the expected margin of error.

Note, lines 16-17 seem inaccurate.

Assuming you were actually pointed those directions those seem perfectly valid. On a compass when one is pointed due north (ignoring magnetic declination) the compass would read 0 degrees and when pointing due south it would read 180 degrees. On line 17 in each case you have numbers that are close. Line 16 is actually telling you that your reference point is true north not magnetic north. If I pulled out my orienteering compass and used it without correcting for magnetic declination I would record my reference at magnetic north, but if I manually corrected for declination I would record it at true north. Since you have a calibrated electronic compass it has already done the correction from magnetic north to true north.

Now that I see your location (or a close enough approximation of it) the celestial north pole would be at about 27 degrees up from the horizon if you are facing due north (likely not magnetic north). If you have a clear night look here and you will find the Polaris/ the north star. If you have never found the north star the line that makes up the far edge of the big dipper points to it. For every degree that you head north Polaris will be 1 degree higher in the sky, until you reach the north pole when it will be directly over head.

Assuming you have correctly calibrated things and were properly pointed in the correct directions you say you were it looks like it would be fairly accurate. The magnetic declination where you are is almost 6 degrees W so if you were out with an old magnetic compass you would have to correct for that but don't know how you determined that you were pointing due north or due south but those numbers look to be within the expected margin of error.


Assuming you were actually pointed those directions those seem perfectly valid. On a compass when one is pointed due north (ignoring magnetic declination) the compass would read 0 degrees and when pointing due south it would read 180 degrees. On line 17 in each case you have numbers that are close. Line 16 is actually telling you that your reference point is true north not magnetic north. If I pulled out my orienteering compass and used it without correcting for magnetic declination I would record my reference at magnetic north, but if I manually corrected for declination I would record it at true north. Since you have a calibrated electronic compass it has already done the correction from magnetic north to true north.

I am familiar as to where the north star appears here, out the front door and to my right lol. the directions i pointed were only close, i didn't use a compas. just based on the north star, sunrise and set. but, north port florida is the actual location

[MossyRocks]

I am familiar as to where the north star appears here, out the front door and to my right lol.

That is good. I have run across lots of people who don't know where it is or how to find it. I would say that the magnetic compass would accurate given your attempt to get it pointed in the right direction.

That is good. I have run across lots of people who don't know where it is or how to find it. I would say that the magnetic compass would accurate given your attempt to get it pointed in the right direction.

i remembered when I was young how to find it using the pointer stars.

This time of year it rotates my way rather late, and we have a lot of trees that block my view. but I know where in the driveway I have to be facing which tree to know where it is.
a lot of 100ft pines here and a rather large oak. basically a small forest behind and to the north of my house.My street faces west and most the roads near me are aligned roads.