At 10am yesterday at Utsayantha Mountain in New York (3200 feet), I saw a narrow pyramid-shaped feature coming off the Sun with the filter at 32C, which is the proper temperature for 5303. I then cut the power and let the filter drop to 10C, going off band by about 3.5A, and it disappeared. I went back to 32C and it came back. Down to 6C this time and gone. Back up to 32C and there, back down to 10C again and gone. Meanwhile I saw a known artifact (probably a scratch on the field lens) on the opposite side, with a different shape but similar brightness. It stayed constant with the temperature changes.
To make sure the pyramid was not an artifact, I rotated the scope in the rings about 5 degrees, and the feature moved by 5 degree against a tiny piece of dust on the cone (seen in the image below). Moved it back and restored. Rotated and moved, restored and back again. So it had to be a solar feature.
I looked then in H-alpha (10A triple cavity), and I got my bearings on the solar positioning. There was a very flat small prom below the pyramid.
I took a photo of SDO's 171A at the same time, but did not look at positioning of the regions until after the observation session. I aligned the photos using shots of H-alpha and GONG.
Below are the shots of it in the 5303A (green) and the SDO 171A (orange), one of each and superimposed. The 5303 shot has a white line under the relevant regions. What I was looking at was the one on the left. Not so obvious in this shot but obvious at the time (I suspect the camera was not well positioned to capture the one on the left well). It was only later, going over it with Klaus, that the bigger one to the right became more obvious in the photo. The one on the right shows the probable base of some loops. But in the eyepiece, the one on the left was easy and I did not notice the one on the right (remember that I had not tried to align 171A yet, so I did not know what to look for). It may be because further to the right was my biggest artifact, and that may have distracted me.
Based on the repeated temperatures, the repeated positioning, and the SDO alignment that was done only after the session, I am convinced that it is the corona. Too high for a prominence, plus the wrong frequency. And I have practice viewing proms at other frequencies now.
Now that Klaus has demonstrated that it is possible, even at moderate altitudes and with moderate assembly skills, you can get there, at least with a 5303 filter and a good atmospheric day. Klaus spent 20 years on it, and I spent the past year but benefitting from his knowledge. You have to be a bit neurotic to get rid of all the sources of scatter, but that's the fun. My two goals were to see prominences unfiltered outside of an eclipse and to see the corona outside of an eclipse, so I am pretty happy.
Next step is building a coronagraph without so many artifacts. Mainly needs a new field lens, but given that, might as well redo it. And I just took a class in solar imaging, so I hope to improve there.
But I need a new camera with a bigger sensor. My ASI290, which did not work out yesterday and thus the iPhone shot, would have gotten the left one but would have missed the right one from the field of view. Maybe a 174? Focal length is over 1000mm. The challenge is that the view is fleeting and low clouds were passing by, so I just could not get the ASI290 properly focused with the spacers I had in the time available. I will practice that with an ND filter and the Sun off center.
George
- 5303 at 32C 20211024 10amET.jpg (78.1 KiB) Viewed 495 times
- 171A 20211024 10amET.jpg (52.83 KiB) Viewed 495 times
- 5303 at 32C and 171A 20211024 10amET.jpg (55.65 KiB) Viewed 495 times
