So far I’ve had two nights of observing with the quadrant. The first was a test run and trying to determine an organization to the logistics of observing. The second was the Mars opposition which had a nearly full moon. In both cases, the amount of actual observing was somewhat limited as a result.
As such, we’ve been waiting for a nice moon-free night to really concentrate on observations. As last night was the new moon, it seemed like a good night, and I was able to tempt a few people into helping out as it’s also very near the peak of the annual Perseid meteor shower.
Ultimately, last night we observed 41 stars and got positions on Saturn and Mars. Two of those stellar observations ended up getting tossed since, after converting them to RA-Dec, they were more than a few degrees off. In one case, it was probably an incorrect identification. In the second one, the star was past 4th magnitude and the night was rather humid making it very hard to focus on as when sighting on the instrument, you can’t really use averted vision since you need your line of sight down the instrument. In addition, the meteor shower drew numerous other people out and many were heading out around that time, so headlights were frequently killing our night vision.
But it was still a good haul. The data is presented below:
| Object | Alt | Az | ST |
| Saturn | 28.8 | 180 | 18h18m |
| δ Sgr | 21.6 | 180 | 18h24m |
| ε Sgr | 17.25 | 180 | 18h26m |
| λ Sgr | 25.875 | 180 | 18h28m |
| α Sct | 43.25 | 180 | 18h35m |
| α Lyr | 89.8 | 180 | 18h38m |
| φ Sgr | 24.5 | 180 | 18h45m |
| β Sct | 46.8 | 180 | 18h48m |
| σ Sgr | 25.2 | 180 | 19h00m |
| ο Sgr | 29.55 | 180 | 19h04m |
| ζ Aql | 65.1 | 180 | 19h08m |
| π Sgr | 30.25 | 180 | 19h10m |
| δ Dra | 61.1 | 0 | 19h15m |
| δ Aql | 54.31 | 180 | 19h23m |
| ι Cyg | 76.5 | 0 | 19h30m |
| γ Aql | 61.95 | 180 | 19h43m |
| δ Sge | 69.0 | 180 | 19h47m |
| ε Dra | 58.15 | 0 | 19h49m |
| α Aql | 60.2 | 180 | 19h51m |
| η Aql | 52.35 | 180 | 19h52m |
| β Aql | 57.5 | 180 | 19h54m |
| γ Sge | 70.45 | 180 | 19h59m |
| θ Aql | 50.15 | 180 | 20h11m |
| Mars | 24.7 | 180 | 20h15m |
| α Cap | 38.3 | 180 | 20h19m |
| β Cap | 36.2 | 180 | 20h21m |
| θ Cep | 65.15 | 0 | 20h28m |
| ε Del | 62.05 | 180 | 20h34m |
| β Del | 65.1 | 180 | 20h39m |
| α Del | 67.2 | 180 | 20h42m |
| η Cep | 66.8 | 0 | 20h46m |
| γ Del | 67.0 | 180 | 20h50m |
| θ Cap | 34.9 | 180 | 21h05m |
| α Equ | 56.7 | 180 | 21h18m |
| α Cep | 66.0 | 0 | 21h20m |
| ζ Cap | 30 | 180 | 21h27m |
| β Cep | 57.6 | 0 | 21h29m |
| β Aqr | 46.8 | 180 | 21h33m |
| γ Cap | 35 | 180 | 21h37m |
| ε Peg | 61.1 | 180 | 21h44m |
| δ Cap | 35.25 | 180 | 21h45m |
To help manage and process all this data, I’ve written a program that takes in the observations, and converts it to RA/Dec for me. I can then compare it with published values to see how we’re doing.
For tonight’s observing session, the average error came out to 0.075º. And furthermore, this can be broken down by observer. Padrig and I did the observing, and whoever wasn’t observing was taking the observations in my log book. Thus, the handwriting clues me in to who the observer was. Padrig has an average error of -0.04º. Meanwhile, my average error is a whopping 0.33º.
I suspect can be explained by a few things. First, Padrig has been the primary observer each night. He’s more familiar with the instrument. In addition, he doesn’t wear glasses. I’ve frequently found that when sighting along the instrument, I’m looking over my glasses, which means I can barely see. Trying to manage my glasses in the middle of everything else isn’t helpful.
Taking the overall data from all three observing sessions so far, the average error in declination is 0.065º or just under 4 arcminutes.
In addition to my program taking in the data, it can also display the stars in graphical form. Based on what we’ve done so far, here’s how that’s looking:
It should be noted that this image is flipped (left-right) compared to how it would look in the sky, as the RA/Dec system is derived from the point of view of an observer outside the celestial sphere. Also the view is highly distorted as this is effectively a Mercator map so things away from the celestial equator (the 0 line) get stretched out.
It’s pretty easy to see that there seems to be a dearth of observations between the 20º and 60º lines in declination. This is because, for our latitude here in St. Louis, this is very near the zenith. To sight along the instrument arm for that altitude, would mean putting your head through the central column of the quadrant. Thus, finding an angle where this will work is extremely difficult.
Many will also probably note that some of the observations have error bars. This represents the standard deviation of the measurements for each star. Since most stars have only been observed once, the standard deviation is zero. But a few have now been observed a couple times.