Trying for a transit of a fainter sort . . .

March 23. So I photographed the transit of Mercury across the Sun. And a much rarer transit of Venus. While messing with Guide 8, I noticed that on the night of March 22-23, the very faint comet Siding Spring HR30 would transit the very faint supernova remnant IC 443. Since the latter has been one of my standard candles while debugging my astrophotography outfit, this seemed like a good time to try to shoot a different sort of transit.

To show IC 443 well requires an H-a filter. But the comet would likely be shining primarily in the continuum with some emissions in the blue-green, far, far away from the H-a wavelength. The comet was down around 15th magnitude (less than half as bright as Pluto, a cool twenty thousand times fainter than the faintest stars visible to the naked eye in my pale sky).

I knew that Tom Nicolaides, an amateur astronomer in southern Mississippi, had been shooting IC 443 with some success -- in color yet -- with a modified Canon DSLR. I thought there was a pretty fair chance that he could record the comet in color better than I could catch it in H-a. On the other hand, I knew my H-a data would be more dramatic. We might then sweeten his image with dedicated H-a data from my ST2K (or mine with color data from his Canon, however you want to look at that) and score an APOD of a much fainter transit.

I put the ST2K behind the 5-inch A-P at its shortest EFL. He put his Canon behind an 8-inch F4 SN. The fields of view were similar.

We both had clear weather. We both shot our respective images. And there's not a hint of the comet in either dataset. At least not where we expected to find it. This is something of a mystery, since I am pretty sure it was within reach.

It shouldn't take a rocket scientist to figure this out. But just in case it does, Tom is one. Stay tuned.

 

 

Somewhere in this picture of a very faint
supernova remnant is a very faint comet.

14x600s, ST2K, 10nm H-a filter, -25C
5-inch F6 A-P @ F4.3

Click here for a bigger image.
It's a mite noisy since
I've stretched the hell out of it..

 

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Text & Photos by David Cortner
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