Comet Lulin (C/2007 N3)

[markt]

First off, happy new year to all of you! Hope you all had a great festive season! ;D

Spotted on Spaceweather today Lulin is getting brighter www.spaceweather.com/archive.php?view=1&day=08&month=01&year=2009

Not seen it myself yet, but as it gets more favourably placed in the sky, given some clear skies, i'll sure be looking out for it. I bet a pint of beer it's Bill who gets first observation though, he always seems to manage it with these comets

C'mon the rest of you, quick, while he's not looking, lets see if we can beat him to it

[Bill W]

Better make mine a pint of ice cold Guiness...

This is the first imaging attack.

Conditions weren't particularly good (as usual) but here's C/2007 N3 (Lulin).



11 x 2 minutes with a 300mm f4, serious dewing right from the word go and high cirrus. The anti tail is just about visible.
Maybe mag 6(ish), difficult to tell but very easy to see in 10x50's.
It's also really moving. Whilst the camera was clicking away with that unique digital SLR shutter sound, I could detect movement in a couple of minutes with the binoculars.

Also in the sky is comet 144P/Kushida, around mag 9.



6 x 2 minutes with the 300mm lens. Just below the comet are two clusters, NGC 1817 and NGC 1807.

Ice on the camera, ice on the lens, ice on the car and ice on me, a good night all in!

Cheers,
Bill.

[markt]

Great shots Bill! Cloudy skies and me not waking up when it was clear has prevented me from seeing Lulin so far. Now it's visible at a more sociable hour, and it's at it's brightest means i'm going to make an extra effort to grab a view of it.

Looking at pics of it from elsewhere it really appears to be motoring through the sky. Just need the clear skies now...

[André]

The english weather was not very good for comets the last weeks, but finally I found a hole in the clouds to spot Lulin from Bath.
As I do not have a guidable mount yet, I had to make the images using only a normal tripod and very short exposure times.

Image 1 from 1.3.2009 23h
25 photos, 10s, 1600Iso, 50mm/1.4 at 2.0

(click for large version.)

Image 2 from 5.3.2009 22h
40 photos, 5s, 1600Iso, 135mm/2.8 at 2.8

(click for large version.)

Please note, both images were made without any guiding! Just a steady camera and a lot of adding!

Unfortunately the moon was already pretty bright and will be even worse the next nights. But after the moon is gone, Lulin will probably be very faint, so I guess we should use everey sight we can get!

Regards,
André

[markt]

Great shots Andre! Clear and non light polluted skies are a rarity these days. I managed to get a view - optically I preferred the view through my 80mm finder than my C8. I did take some pickies but haven't got them to a state i'm happy with at the moment. I will persevere though and will pop a pickie up as soon as I get one

[André]

Hi Mark

Unfortunately my sky here in Bath is pretty much light polluted. A lot work was necessary to get rid of the Sodium-orange sky in these images.
But I just read they want to make the Exmoor national park a dark sky park as well. That sounds pretty interesting, and the exmoor is kind of next door to me :-)

I'm looking forward to see your images!

André

[markt]

I've finally got round to processing the data I got for Lulin a week ago.

It's a composite of 34 x 30 sec images, iso800 with my 350D at prime focus of my C8 which was running at f10.



There are several things I would have done with hindsight:

Looking at the Lulin images alone from the forums it seems to me that 30 sec subs are just too short to pull any detail other than on the coma - ideally subs of a couple of minutes seem optimum.

I would have taken darks, flat and bias frames - my image is rather more noisy than I would like.

I would have used my focal reducer on the C8, f10 is a bit slow tbh, and the fov is smaller than I would like.

I would have imaged with my moon and sky glow filter on to remove some of the light polluting durge from the picky.

I want to get a guider for my EQ6 - I probably chucked 1/2 of the images out due to tracking issues. But, hey ho, I managed to see and image this comet which i'm pleased about, what I can take from this is the lessons learned and apply these to whatever the next comet is I see

*Edit*
Forgot to say, this image is from 01/02 March...

[André]

Hi Mark

not too bad!
Which software did you use? I have the feeling, that there is quite a lot of noise for that many images and the quite low ISO value.
Also I wonder, why you have sharp stars and a sharp coma. Shouldn't it have moved faster?

Cheers,
André

[Bill W]

Hi,
Not too bad indeed, but I had the very same thought. Why doesn't either the comet or the stars show some trailing.
It is really shifting. The weather here has been cr*p but I had a short spell on the 1st.



This is 10 x 30 secs. (you can see how poor the tracking is if you look at the hot pixel slug trails...) I've deliberately lowered the processing contrast and re stacked on the stars to show the comets motion.
Might you have posted a single frame?

Taken through 200mm dia, f4 reflector, mid exps 23.27ut.
I use ISO 800 also as it is the optimum (or near enough) for signal to noise.

I like the shot of Lulin with M44, that was view I'd have liked to catch.

[markt]

Hi Guys,

Thanks for the kind words. I use Deep Sky Stacker deepskystacker.free.fr/english/index.html for the bulk of the image processing - bit of Corel Draw at the end for the cosmetics. If you have a mooch through the 'Techincal Details' section it has a comet stacking feature. This allows 3 options - the software stacks the stars and you have a streaky comet, the software stacks the comet and leaves you with streaky stars, or the third memory intensive option is that it stacks both the stars and the comet - which is what I did.

It still is a bit noisy for my liking at the moment, but i'm still playing around with the settings on DSS, as I got much better results from similar stacks when Holmes was around.

Cheers! Mark

[Bill W]

Now, that IS clever digital jiggery pokery!

[Bill W]

Lulin is now fading but still sporting a tail.



8X2min with the 300mm f4 lens, 21.19 mid exp, 19/3/09 (and considerable mist, I couldn't even persuade myself that I could see it in the 10x50's!)
Stacked with Deep Sky Tracker.
Digital jiggery pokery indeed.... Quite brilliant!

[markt]

Top shot agin Mr Ward!

Unfortunately from the delightful English Midlands naked eye visibilty tonight is about 2nd / 3rd magnitude so unfortunately Lulin is relegated to the nether regions of the solar system for me. Not all doom and gloom though, i've been getting some nice views of Saturn

[Jay]

All those pics are excellent compared to my pathetic attempts! at first i was a bit baffled how such decent photos were taken with a unguided camera, which is what i used, then i read further to see that they are stacked, i have seen this mentioned before but never fully understood what stacking is, I have just downloaded that deepsky stacker, (thanks for the link) maybe someone can give a simple explantion how to use it, would it make this photo look similar to the ones posted here?



the comet is there! its the slightly blurrier object compared to the streaks of the stars! and the photo is awfully grainy, i think i need to use a lower iso, but from my old days of a film slr, i always thought a higher iso was better for astrophotos, i still have alot to learn about how to take really decent photos with my digital camera!

[markt]

Mar 10, 2009 16:55:39 GMT markt said:

It still is a bit noisy for my liking at the moment, but i'm still playing around with the settings on DSS, as I got much better results from similar stacks when Holmes was around.

Had a nose through my data - Holmes was shot on 'RAW' - Lulin was done in 'JPEG'.

*Makes note to do ALL astro shooting in RAW from this point forward*

Hey Jay, is that a single exposure you've posted or a composite of aa number of exposures?