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May 11, 2013: Mini H-alpha session, first light of B1200D blocking filter

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Today when I got home from buying stuff on the market, a little package was waiting for me: a second-hand Lunt B1200d diagonal type blocking filter. This was going comparatively cheaply, because it was a 2" version which had been (amateurishly) modded by shortening the 2" nose-piece. The optics where absolutely fine, so I unscrewed the 2" nose-piece from this filter, and replaced it with the 1.25" nose-piece from the B400 of the LS35 H-alpha scope. In principle, a B600 would be ample, but as this B1200 was going for the price of a B600, I snapped it up. It will also be an integral part of a modification I am planning for this LS35, which may have it ending up with a longer focal length.

As luck would have it, the clouds broke, so I quickly put the scope outside, and tested it. The view was much, much better, as this filter widens the sweet spot of the scope considerably, and I could get the full disk and proms evenly illuminated with ease. The B400 had a much smaller sweet spot, so to inspect all proms you did have to move the sun about a bit within the FOV. Not so in this filter. I had heard reports that choosing a larger blocking filter than the scope requires can cause ghost images, but none were to be seen. What I did see was three massive proms on the lower western limb, and two massive sunspots on the eastern, easily visible in H-alpha, indicating the arrival of some interesting new ARs. on the western half of the disk, north of the equator a large plum seemed to be erupting on the surface.

Unfortunately, I had to stop observing at that point because rain clouds were rushing in again, but I am very happy to have been able to test the new toy immediately.


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Interesting stuff Michael, especially the new prominences.

It's been very overcast here today, and there's rain forecast for tomorrow, which is a pity since I'm supposed to be doing outreach at a local fair with my astronomy society and the PST is usually a great success.

I bought a PST of my own this week, but it's got a fault and is going back next week. I'm hoping for a speedy fix or replacement. Add to this that the loan scope I've got at the moment has to be returned on Monday and it doesn't look like I'll be seeing much of the coming excitement :-(

I guess there's always white light, but after H alpha for a couple of weeks it's just not the same. Still I hope the skies clear up for your new toy, and you'll just have to enjoy it for me too ;-)

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