Observing Report 12th July 2012 (Sunspots)

Posted by @ 1:39 pm on Saturday 14th July, 2012.
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Thursday morning was surprisingly clear and sunny - an odd period sandwiched between countless hours of incessant rain. I managed about half an hour of solar observing before it all went claggy. The seeing wasn't that good but I managed to get fair views of Active Region 1520 and its satellites. Apologies now for the poor-quality images, I might have another bash at the stacking to see if I can get the noise levels down a bit without losing any detail:

Active Regions 1519 - 1521 (12/07/2012).
50/6000 stacked frames.
DMK mono CCD camera with 2x Powermate on the C80ED-R.
Baader Planetarium AstroSolar™ Safety Film (ND 5.0) with #58 Green and IR-cut filters.

The largest spots in AR1520 are even bigger than those in AR1504 which I imaged last month!

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4 Responses to “Observing Report 12th July 2012 (Sunspots)”

  1. How big is the area shown in your pics, like how many miles across?

  2. BG! says:

    Originally Posted By Conrad R. (Sir Hugh)
    How big is the area shown in your pics, like how many miles across?

    That's a tricky question that could have a long answer - we're looking at the intersection of the telescope's conic field of view with the Sun's spherical surface, this situation is made more complex by the following: a) the axis of the conic field of view is offset from the centre of the sphere (and so the foreshortening-due-to-curvature effect is uneven around the image); b) the camera only "sees" a small central part of the conic field of view (like a rectangular-based pyramid); and c) the resulting image has been cropped a bit.

    My best estimate at this time of the morning (when the old grey matter isn't up to full speed) is approximately 125,000 x 100,000 miles.

    Have a look here if you want to get an idea of the scale and positions of these sunspots.

  3. That is fascinating. It means the darker bits in the middle are perhaps 5/8000 miles in diameter. Do we keep seeing larger sunspots, I mean are they increasing or in decline. I realise that the time span involved for answering that question is immense.

    Do you have a huge investment in equipment to get these kinds of images?

  4. BG! says:

    Originally Posted By Conrad R. (Sir Hugh)
    It means the darker bits in the middle are perhaps 5/8000 miles in diameter. Do we keep seeing larger sunspots, I mean are they increasing or in decline.

    The largest sunspot ever recorded was visible in March and April 1947 and covered an area of over 7,000 million square miles; about a hundred Earths could be fitted into this area. There's a picture and more info here.

    Sunspot populations quickly rise and more slowly fall on an irregular cycle of 11 years, more info here.

    The Spaceweather website has daily updates on solar activity and is worth a browse.

    Originally Posted By Conrad R. (Sir Hugh)
    Do you have a huge investment in equipment to get these kinds of images?

    I won't disclose what I've spent on my kit but here's a list of what I use for close-up solar imaging, I've included reasonable sale or second-hand prices (I usually buy sale or second-hand kit these days):

    80mm refractor telescope (~£100);
    Motorised mount (~£200 - ~£400 depending on spec);
    Solar Filter (~£20);
    Powermate lens - x2 magnification (~£150), but a perfectly adequate x2 Barlow lens for ~£30 would suffice;
    Mono CCD Camera (£250), but a suitable CCD webcam (~£30 with telescope adapter) works well instead;
    Colour and IR-cut filters (~£10 apiece)
    Software for stacking movie-frames to make a single image (free)

    With the exception of the solar filter all of this kit had been acquired already for nocturnal astronomy, so you could say that it's cost me about a score to get into solar imaging 🙂

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