CHAT LOG FOR CALIBRATING YOUR STAR FINDER

[Paula Noeller joined the session] [Connor Hibbs joined the session] Paula Noeller: HI Paula Noeller:This is probably the most difficult lab in the course Paula Noeller: Have you looked at it at all?Connor Hibbs:oh great the first two were not the easiest for mePaula Noeller:Well this one builds on the last onePaula Noeller:but adds a twistPaula Noeller: Have you done anything in this lab? the tutorial?Connor Hibbs: not a thing I know we are suppose to already attempt the lab before getting in here. but I didn’t quite get around to it yetPaula Noeller: I have taken some pictures I was going to take of the tutorial... to make it more clear,.. hope to have time to post themPaula Noeller: okayConnor Hibbs: okPaula Noeller: well let's do thisConnor Hibbs: alright haPaula Noeller: do you have your star finder and a blank piece of paperPaula Noeller: piece of paper Connor Hibbs: uh give me a secPaula Noeller: And if you have a flexible ruler that would be greatPaula Noeller:you also need a string and some tapeConnor Hibbs: don’t think I have a flexible ruler Paula Noeller: didn't figure you wouldPaula Noeller: how about some dental floss and tapeConnor Hibbs: I do have dental flossPaula Noeller: let me know when you have everythingConnor Hibbs: ok I think I'm readyPaula Noeller: okay Paula Noeller: now put the paper between the cover and the back Paula Noeller: and then with a pencil trace the horizon part on the paper Paula Noeller: so you have an oval that represents the horizon

Connor Hibbs: ok Paula Noeller: ok Paula Noeller: now take your dental floss and place it so that it represents a north south line Connor Hibbs: ok Paula Noeller: tape it to the star finder at the top and bottom part Paula Noeller: the dental floss will divide the sky into and eastern and western half Paula Noeller: it represents the meridian Paula Noeller: and the eastern part of the sky is the AM part ante meridian (before the meridian) Connor Hibbs: alright give me a sec Paula Noeller: and the western part is the PM part (post meridian) Paula Noeller: the floss should be running north south Paula Noeller: the top part should intersect due north and the bottom part due south Connor Hibbs: alright

Paula Noeller: you can mark on the white paper due north and due south that coincides with the N and S on the horizon Paula Noeller: and then on the paper mark due E and due W Paula Noeller: Due E is between the A and S of EAST Paula Noeller: and due W is between the E and S of WEST Paula Noeller: what we are doing is calibrating your star finder Paula Noeller: into degrees Connor Hibbs: ok Paula Noeller: if you go outside you can turn 360 deg to see the entire horizon Paula Noeller: and due N is 0 deg Paula Noeller: and due E is 90 deg Paula Noeller: due S is deg and due W is 270 deg Paula Noeller: so you can label those deg on the cover of the star finder opposite N, E, S and W

Connor Hibbs: ok Paula Noeller: and now we have four quadrants between those cardinal directions Paula Noeller: a NE, SE, NW and SW quadrant Paula Noeller: and each of those represent 90 deg Connor Hibbs: ok Paula Noeller: so now we are going to take each quadrant and divide it into thirds Paula Noeller: with a flexible ruler you can measure the distance between N and W Connor Hibbs: so I'm imagining pieces Paula Noeller: I think I got approximately 9.2 cm between the N and E part of the horizon and the N and W part of the horizon. Paula Noeller: be sure you make your own measurements Paula Noeller: so then I would take the ruler and bend it along that NE horizon and mark it into equal thirds Paula Noeller: and each third would be approximately 9.2 / 3 = 3.06 cm in length. Paula Noeller: so if I were standing in the middle of the star finder Paula Noeller: which is the midpoint of the dental floss Paula Noeller: and looked north Paula Noeller: that is 0 deg on the horizon Connor Hibbs: ok Paula Noeller: and then if I turned and looked at the first mark 1/3 of the way between N and E Paula Noeller: that would be how many deg Connor Hibbs: 30 deg Paula Noeller: yes Paula Noeller: and the next third? Connor Hibbs: 60 deg Paula Noeller: and then the next third which is due east Connor Hibbs: 90 deg Paula Noeller: yes Paula Noeller: and you would do the same for the NW quadrant Connor Hibbs: ok Paula Noeller: the measurements should be the same Connor Hibbs: yes Paula Noeller: so if you look due west what deg is that? Connor Hibbs: 270 deg Paula Noeller: and the first third headed north from due west? Connor Hibbs: 300 deg

Paula Noeller: yes Paula Noeller: and the next third 1/3 of the way from due north Paula Noeller: would be 330 deg Connor Hibbs: ok Paula Noeller: and then we would do the same thing for the SE and SW quadrants Connor Hibbs: ok Paula Noeller: let me check my measurement for that Paula Noeller: I think the distance between E and S is about 15.5 cm Paula Noeller: and you would divide the SE and SW quadrants into thirds with each third measuring along the trace, 15.5/3 = 5.16 cm. Connor Hibbs: ok Paula Noeller: so starting East Paula Noeller: the first third past East heading south would be? Connor Hibbs: 120 deg. Paula Noeller: yes Paula Noeller: and the next third would be 150 deg. Paula Noeller: and then in the SW quadrant? Connor Hibbs: 210 deg Connor Hibbs: 240 deg. Paula Noeller: okay Paula Noeller: these angular directions on the horizon are called azimuth

Paula Noeller: Now mark the midpoint of your dental floss Paula Noeller: that will be the zenith Paula Noeller: the point over head Connor Hibbs: can it be a guess Paula Noeller: nope Paula Noeller: for now I guess Paula Noeller: so you can understand the principle Connor Hibbs: that was my point Connor Hibbs: ok Paula Noeller: but you want to get the exact mid point

Paula Noeller: as much as possible Paula Noeller: obviously there will be a range of acceptable answers Connor Hibbs: ok does it have to be the mid point or higher up like it is on the star finder Paula Noeller: you want it the midpoint... NOT the gold grommet Paula Noeller: the gold grommet is where polaris is which is not the point overhead Connor Hibbs: ok Connor Hibbs: stumped me with the gold grommet Paula Noeller: the gold grommet would only be overhead if you were at the north pole Connor Hibbs: oh ok

Paula Noeller: Now mark on the cover of the star finder along the horizon the same marks that correspond to the marks on the tracing you made... In other words, use the tracing on the white paper as a template to calibrate the cover the the star finder.

Paula Noeller: Now remove the white paper with the tracing so that you can see the stars in the star field... (I highlighted my markings for clarity)

Paula Noeller: Now to give you a example of how you will be using the calibrated star finder. Set the star finder for midnight on July 12 Connor Hibbs: k Paula Noeller: now find Arcturus in the Constellation Bootes Connor Hibbs: ok Paula Noeller: if you were standing outside at midnight on July 12Paula Noeller: what would be the azimuth of Arcturus Paula Noeller: if you were looking at arcturus what part of the horizon would you be looking at Paula Noeller: I got 270 deg azmimuth

Paula Noeller: due west Paula Noeller: if you take a piece of paper and line up the edge of the paper with the zenith where you are standing and Arcturus, you see where the edge of the paper intersects the horizon Paula Noeller: I am pretty close 270 deg or due WestConnor Hibbs: ok Paula Noeller: Now if I told you I was looking at a star that had an azimuth of 270 deg Paula Noeller: would you necessarily know it was Arcturus? Connor Hibbs: no Paula Noeller: couldn’t it be any star on that line between the zenith and 270 deg on the horizon?Connor Hibbs: yeah Paula Noeller: so the next thing you would have to know is how high above the horizon Paula Noeller: that is the altitude of the star Connor Hibbs: ok Paula Noeller: doesn't it look like Arcturus is almost half of the distance above the horizon toward the zenith Connor Hibbs: about yeah Paula Noeller: from the horizon to the zenith is 90 deg Connor Hibbs: I thought so Paula Noeller: if you go outside and look straight ahead you are looking at the horizon Paula Noeller: that is an altitude of 0 deg Paula Noeller: and if you tilt your head to look straight up Paula Noeller: you tilt your head 90 deg Paula Noeller: so the an object at the zenith has an altitude of 90 deg Connor Hibbs: I see Paula Noeller: to me Arcturus is just slightly less than 1/3 of the distance above the horizon Paula Noeller: yes... to your observation Paula Noeller: so you could say that the altitude of Arcturus at this time of night is maybe 28 deg Paula Noeller: there is a range of acceptable answers Connor Hibbs: ok so if that star was at the same point on the east would it also be ? Paula Noeller: the altitude will be less precise than azimuth Paula Noeller: if the star was the same distance between the horizon and the zenith Paula Noeller: the same fractional distance Paula Noeller: do you see Vega? Paula Noeller: let's estimate its altitude at the same time ...midnight on the 12 of July Connor Hibbs: 87 deg? Paula Noeller: probably not that high Paula Noeller: maybe 80 deg Connor Hibbs: ok Paula Noeller: divide the distance between horizon and zenith into thirds Paula Noeller: and the third closest to the zenith into thirds Paula Noeller: just estimate Connor Hibbs: ok Paula Noeller: so Vega is about 2/3 of the way in that last thirrd... which is 60 deg. So 60 deg + 20 deg = 80 deg.Paula Noeller: make sense? Connor Hibbs: yeah it makes sense Connor Hibbs: so pretty much you want me to make the star finder on grid paper Paula Noeller: and the azimuth of Vega would be ? Connor Hibbs: like 210 degPaula Noeller: that might be close Paula Noeller: you have to calibrate your horizon to be sure Paula Noeller: I don't want to say yeah or nay right now Connor Hibbs: like 200 deg? Paula Noeller: Actually closer to 230 deg.Paula Noeller: What I will do is post some sample star and their altitude and azimuth so you can check that you are doing it fairly accurately Connor Hibbs: ok Connor Hibbs: appreciate you staying past the chat time Paula Noeller: no problem Connor Hibbs: I understand how to do it

Connor Hibbs: its just creating the lines accurately Connor Hibbs: I was just kinda eyeing it since I don’t have a ruler Paula Noeller: but do you get the idea Connor Hibbs: yes Paula Noeller: great Paula Noeller: then have a good evening Connor Hibbs: you too Paula Noeller: :) Paula Noeller: night [Paula Noeller left the session] [Connor Hibbs left the session]