Comet Garradd crosses the Milky Way

[661-pete]

I did this last week - 27th August, when Garradd was passing through just about the densest part of the MW in Sagitta: it's approaching the 5th mag. star Zeta Sge.

I took 18 x 2minute subs, and then spent ages tearing my hair out trying to figure out how to process the data. Received wisdom says, you should align on the comet nucleus and allow the stars to trail. Tried that, and even with severe sigma-clipping the result was horrible. The field is just too full of stars! So then I tried aligning on the stars, but the comet moved too much and turned into a sausage. No good. Then I tried aligning on stars and doing an animation of all 18 subs, but the result was too noisy.

Finally I settled on aligning on the stars, stacking three subs at a time, and then animating the six resulting stacks. The comet doesn't come out too blurred over the six minutes of each frame. Anyway, here's the result.

I know there are clever techniques for aligning the field stars and the comet separately and then combining the two, but I don't know how it's done...

[hayju01]

I like that ALOT!

[RikM]

I think that is a really nice little sequence. Well done. The colours are great and you really get a feel for just how fast the comet moves across a packed star-field like that.

[661-pete]

Thanks guys! Just for comparison, here is my attempt at aligning on the comet and savagely filtering out all that lovely star cloud. This was by stacking on median, not average, and sigma clipping at 0.1 x sigma. At least you can see the overall shape of the comet, although the image is rather messy!

[Tassydevil]

Very nice.

[stolenfeather]

Very nice capture Pete, wow!

Isabelle

[laser_jock99]

Wow- that's some movement.

[Beulah]

Stunning star field.

I have yet to see this comet. (need clear skies)

[QldLiz]

Lovely images Pete, so many stars in the first, it looks great.

[Tutankhpip]

There is a small white star at 4 o clock to the main star in the first frame but disappears in the rest. Any idea if this is a processing artifact or actual motion of the star (assuming it is a star of course)?

[fwm891]

I love these comet animations - great stuff

[peter shah]

nicely captured

[661-pete]

Thanks again.

There is a small white star at 4 o clock to the main star in the first frame but disappears in the rest. Any idea if this is a processing artifact or actual motion of the star (assuming it is a star of course)?

I've had a quick look at the unprocessed subs and it's not in them: it appears to be an artifact, no doubt due to my efforts to straighten out the trailing with FocusMagic (I don't have guiding). Not a fragment of the comet!

[saturn5]

Stunning star field.

I have yet to see this comet. (need clear skies)

Unfortunately,ditto.Lovely shot.

[Pingster]

Wow. Awesome work guys. Ive seen this comet visuslly, but seeing it animated is just great.

[Vali x]

...The field is just too full of stars!.....now you're complaining??? just teasing you man ! cool pics !!!