Saturday, March 14, 2015

Imaging a Dwarf Planet

Did you know that many of the dwarf planets are bright enough to image? Here are some current magnitudes (and distances from the Sun in AU):
  • Pluto: 14.2 (33.2)
  • Makemake: 16.9 (51.5)
  • Haumea: 17.2 (49.9)
  • Eris: 18.7 (97.2)
  • Quaoar: 18.9 (43.0)
  • Orcus: 19.1 (47.1)
  • (120178) 2003 OP32: 20.0 (42.9)
  • (84922) 2003 VS2: 20.0 (36.7)
There are more, but they grow progressively dimmer. 

From my red zone skies I can get down to about 20th magnitude with an hour's total luminance exposure through my C 925 and ST-8300M. Doubtless you can do better if your skies are darker or your scope is larger.

I became interested in these thanks to the AL Bright Nebula list. The list has seasonal dead spots when combined with my tree-infested back yard.Right now I can catch a few of the lingering winter objects but there's a wait for summer's objects; after 11 here there's almost nothing to image until dawn. I noticed that Makemake fits nicely into that gap so I went after it. I captured it on the 10th and again on the 13th:

At magnitude 16.9 it shows up easily in the stacked frames (each of the images represent about an hour's worth of 2-minute luminance exposures.) The lighter background on the second image comes from clouds that night. It was a good thing I got that image when I did--clouds have been the rule since then.

Imaging objects like this tests your skill. You may need to shoot test frames to reveal very dim field stars in order to confirm that you have the right area. Even if you have great confidence in your go-to I suggest that you shoot some test frames and compare what you get with computer charts to be sure you're on target. In the test frames i relied on 12th magnitude stars that showed up in 10-second exposures.

Remember that if you want to confirm that you're looking at a Solar System body you'll have to image it twice. Consecutive nights are best, but we all know about the weather. I was lucky to get two clear nights in close proximity.

Haumea is next for me--it's a spring object. Then Quaoar during the summer and Eris in the late fall.

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