Comet Observations 27/8 July

[brianb]

Here are a couple of images I made of comets last night. These were made with a Canon 5D & 300mm lens working at f/4, piggyback mounted on my 8" LX90 SCT. B+W 491 filter was used to combat light pollution. Sub-exposures registered & stacked using Deep Sky Stacker. The centre of the image has been cropped, making the effective focal length about 800mm. The colour saturation was greatly increased to make the green light characteristic of cometary comas stand out, this means that there is a lot of chroma noise in the sky background!

6P/d'Arrest, 10 x 30 sec exposures between 01:20 and 01:31 UTC 28 July: The comet is only just visible, but the greenish spot indicated is at the exact position according to the ephemeris. I'm fairly sure I've got a capture. Unfortunately thin high cloud was spreading in and I was unable to take more images of this region.


2008J1/Boattini, 20 x 20 sec exposures between 01:35 and 01:59 UTC 28 July. The green glow of the extended cometary coma is clearly visible.

[John9929]

Great captures Brian, I had intended trying last night but by 1am the whole sky was shrouded in thick fog, I couldn't even see stars overhead!

[Paul]

Brian, that's superb work, well caught on both counts!

[brianb]

Thanks guys.

The interesting thing is that I thought I could see 6P/d'Arrest through the eyepiece, but I was sure I couldn't see 2008J1 Boattini.

I think Boattini's comets have a curse on me - I seem to be able to image both of them but see neither

2008J1 is clearly well above mag. 10 and ought to be visible.... really well placed just about ten degrees above Polaris, no excuses for bad horizons or twilight please!!!!

[martinastro]

Brian, fantastic work catching both of those elusive comets!!. Your camera confirms that they are both of the gas variety!. Very impressive imaging indeed. Any chance you could provide us with a post perihelion image of W1?.

From looking at your images I was thinking Y1 looked to be a better candidate for visual observation. Your latest post confirms that so tonight I'm going to have a bash at it with the 8.5" despite the street lights. It's very well placed as you say...in fact, it couldn't be better!.

[brianb]

Any chance you could provide us with a post perihelion image of W1?.

OK, here's the excuses - last night the Moon was in the wrong place - yes, I know it was only a fat crescent, but it would have been a nuisance. And it just so happens that I have a poor East horizon, and it's also in the wrong place so far as local light pollution is concerned, so I would have to go to an alternate site. Which I didn't feel like doing on the first really decent night for a couple of months.

Anyway, 2007W1 is getting higher & will clear my obstructed horizon in a couple of weeks.

I'll get it before it goes away.

[dogstar]

Brian they are excellent images your hard work has rewarded you well done looking foward to more

[Roman White]

Excellent work on catching those faint comets, Brian.  What magnitude were the comets and what was the limiting magnitude on those photos?

[brianb]

What magnitude were the comets and what was the limiting magnitude on those photos?

The photographic magnitudes are not always the same as the visual ones, it depends a lot on how condensed the coma is. Very diffuse comets will sometimes be very hard to record even though they're bright in magnitude terms - for instance in April I was having difficulty imaging Comet Holmes even though it was still mag. 5 - because it was spread out over a couple of square degrees of sky.

2008J1 was around mag. 9.5 and 6P was around 12. The limiting magnitude in these images is around 14. This camera and lens can get to mag. 15 with 10 x 2 min subexposures in good sky conditions.

[Roman White]

The limiting magnitude in these images is around 14. This camera and lens can get to mag. 15 with 10 x 2 min subexposures in good sky conditions.

It's great to have such high limiting magnitude!