Saturday, April 11, 2015

Leo I First Attempt; LBN 1089?

Last night was clear and I tried imaging LBN 1089 and 1090 from the club's dark sky site Cherry Grove. It did not go well.

LBN 1089 rises to an elevation of only about 16 degrees; LBN 1090 maxes out at 13 degrees. There's simply too much extinction and horizon glow for it to show up. A total luminance exposure of 21 x 5 m at f/4 produced not a hint of nebulosity.

This shouldn't be surprising, I suppose. Dan Crowson created this image of 1089 and had this to say about it:

Lynds Bright Nebula 1089 is a very faint cloud of dust located in southern constellation Antlia. This object at -29 declination only reaches about 20 degrees in altitude from my imaging location. Lynds’ gives this one a 5 out of 6 on the brightness scale (with 6 being the dimmest). This is by far the faintest object I’ve tried to image so far. I had to stretch the data more than normal to get this result. This is another one of the ‘bright nebula’ that are found on the Astronomy League’s Bright Nebula Program. I could not find any other images of this one.

I've added the emphasis. When Crowson says something is very dim, it's dim. In fact if you look at the image the nebula looks more like an integrated flux nebula than any sort of "bright" nebula. Yet it's on the ALBN and supposedly can be visually observed.

I think an open question is why this nebula is on the ALBN list. The same issue applies to many of the other nebulae with Lynds brightness 5 or 6.

The magnetic finder worked great. There could be a little more friction between the base of the magnet and the steel plate, or possible some sort of detent to keep the finder from moving when turning it on and off.

At the end of the evening I tried imaging dwarf galaxy Leo I. It's brighter than I thought-- it was distinct on individual 5m, f/4 light frames. Tonight I'll try it again with my C925. It should look a lot better at a focal length of 1480mm than it did at 135mm!

Leo I at 135mm FL (5x5m at f/4)

As above from SkyTools3

Also on tonight's agenda is dwarf planet Orcus. Currently at magnitude 19.1 it's quite faint but should be in reach if my experience with MakeMake is repeated. In  that image I could see down to 19.4.

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