I was attempting to shoot star trails for the first time while on holiday in the mountainous Cederberg region last week. The moon was out, so the first evenings attempts were limited to about 10mins. The second night we got up in the wee hours after the moon had set to watch a meteor shower, and I left the camera running for about an hour.
Perhaps my own stupidity, but I turned long exposure noise reduction off to get to see the images immediately. I expected to see some noisy spots, but the purple patches surprised me, and I have no idea what causes them. With the moon out on the first night, I thought they might be light bending in from the moon or via the eyepeice. The second night the moon was down, and I covered the eyepeice with some white insulation tape (all I had, but very opaque).
Any ideas or tips for this purple hue problem, or what else to try to improve image quality? Thanks in advance.
Sigma 10-20 @ 11mm, f/8, ISO 280, time-3200s
Going back in Jan for another 6 days, so plenty time to experiment then.