[BAA Comets] C/2013 US10 Catalina - Apparent 3rd tail ?

Mon Jan 18 23:23:32 GMT 2016

Hi Peter,

I chose a blue filter, which as you say can increase the contrast of an ion tail, and that
is what I was after. I have not used it before for comets on it's own, I usually use NIR
which avoids even more light pollution. Or if I want colour I use RGB (Astrodon E-Series).
I mention the make because if you look at the spectra
(http://www.astrodon.com/uploads/3/6/0/7/3607549/astrodonespectra.jpg) you will see a gap
between the green and red. That works wonders to allow me to image in RGB in such light
polluted skies. The Lum filter for me is a complete waste of space in my filter wheel, so
it's not there!

Most street lighting in my area is now LED, but it does not seem to have made the
situation worse, largely I think because the lights are more directional and point down.
They also appear to be not as bright, but that may be an illusion.

One test to estimate how clear your sky is, is by counting the number of stars you can see
in the square of Pegasus. Well I can see the square, thats it! 

So my message here for those reading this who thought it not worth their time and effort
to image in poor skies, do think again. I am absolutely amazed at what I can image. Yes it
is more effort, you have to pick your equipment and use different techniques and generally
have far longer integration times than those who live in Norfolk!! Hi Andrew, I am only
jealous.

Mike

>Hello Mike,
>I'm interested that you use a blue filter for your comet images. Does that 
>significantly reduce the light pollution without adversely affecting the 
>comet ? I know some other comet observers image through a blue filter to 
>increase the contrast of an ion tail.
>I assume your light pollution is not from LED street lighting which emit 
>strongly in the blue. However I do photometry on my images so a blue filter 
>would spoil the raw data.
>
>Mike and Andrew,
>My skies, on a moonless good quality night, are usually around SQM 18.8 from 
>dusk to around 1am. They generally improve between 1am and 5am to around SQM 
>19.2 but can very occasionally reach SQM 19.65, particularly when there is a 
>northerly air flow across the country which there was at the time of my 
>images on the 16th.
>Andrew is just plain spoilt with 21+ skies.
>
>Your (and my) images do demonstrate that useful comet imaging can be done 
>from an urban light polluted location which, apart from Andrew, is where the 
>majority of people live.
>Regards
>Peter
>
>-----Original Message----- 
>From: Andrew Robertson
>Sent: Monday, January 18, 2016 4:32 PM
>To: 'BAA Comets discussion list'
>Subject: Re: [BAA Comets] C/2013 US10 Catalina - Apparent 3rd tail ?
>
>Blimey, I think SQM-L 21.0 is a poor night where I am in Norfolk.
>
>Andrew
>
>-----Original Message-----
>From: Comets-disc [mailto:comets-disc-bounces at britastro.org] On Behalf Of 
>Michael Oates
>Sent: 18 January 2016 15:47
>To: BAA Comets discussion list <comets-disc at britastro.org>
>Subject: Re: [BAA Comets] C/2013 US10 Catalina - Apparent 3rd tail ?
>
>Peter,
>
>Thanks for the update, yes your image shows it more clearly as a fork. I 
>note you included an SQM reading of 19.58 on your image. Mine was SQM-L 
>18.87 which is better than usual.
>The norm is about 18.5/6 here in Manchester and I have never seen it reach 
>19.00!
>
>That is why I always image with a filter, blue being a good one for comets.
>
>Mike
>
>>Hi Andrew,
>>Yes I agree the ion tail is forked, I don't think 2013US10 has grown
>>another separate tail.
>>Some of my previous images show the tenuous infilling you mention
>>between the two tails. My image from the 16th was taken under hazy sky
>>conditions so doesn't show it well and its too close in to the nucleus.
>>I had intended to use my 100mm refractor to get the image on that night
>>as this would have provided a field of view nearly 2 degrees wide and
>>better displayed the comet. The sky had been clear since sunset and I
>>had been out earlier in the evening, but decided to go to bed and get
>>up before dawn because I was feeling unwell with a cold. When I got up
>>at 04.45am the sky was deteriorating fast and I didn't have time to
>>swap the camera over. I should have persevered later into the night
>>before and just taken a bigger box of tissues out to the observatory with 
>>me to mop my nose up!!
>>
>>Peter
>>
>>-----Original Message-----
>>From: Andrew Robertson
>>Sent: Monday, January 18, 2016 11:26 AM
>>To: 'BAA Comets discussion list'
>>Subject: Re: [BAA Comets] C/2013 US10 Catalina - Apparent 3rd tail ?
>>
>>Your image shows it more as a fork in the ion tail rather than a 3rd
>>tail Peter. I did look at it last night about 1.30am after the moon had
>>largely got out of the way but I was only using my OMC 200 albeit a
>>very high contrast scope. In that there was a very large coma with a
>>much larger tenuous extension filled in over about 90 degrees.
>>
>>Andrew
>>
>>-----Original Message-----
>>From: Comets-disc [mailto:comets-disc-bounces at britastro.org] On Behalf
>>Of Peter Carson
>>Sent: 18 January 2016 11:21
>>To: BAA Comets discussion list <comets-disc at britastro.org>
>>Subject: Re: [BAA Comets] C/2013 US10 Catalina - Apparent 3rd tail ?
>>
>>Hi Mike,
>>I imaged C/2013US10 107 minutes after you on the 16th Jan. My image,
>>which is closer in to the coma, also shows a streamer heading off
>>slightly south of west.
>>Full details are on the image.
>>http://www.astromania.co.uk/2013US10_20160116_0535_PCarson.jpg
>>
>>All the best
>>Peter
>>
>>-----Original Message-----
>>From: Andrew Robertson
>>Sent: Monday, January 18, 2016 8:52 AM
>>To: 'BAA Comets discussion list'
>>Subject: Re: [BAA Comets] C/2013 US10 Catalina - Apparent 3rd tail ?
>>
>>More noticeable with the star trails removed. Interesting.
>>
>>Andrew
>>
>>-----Original Message-----
>>From: Comets-disc [mailto:comets-disc-bounces at britastro.org] On Behalf
>>Of Michael Oates
>>Sent: 17 January 2016 18:32
>>To: BAA Comets discussion list <comets-disc at britastro.org>
>>Subject: [BAA Comets] C/2013 US10 Catalina - Apparent 3rd tail ?
>>
>>Hi,
>>
>>There is what appears to be a faint third tail between the main dust
>>and gas tails.
>>
>>45 subs of 60s each, all registered on the comet. Full details on the
>>images.
>>
>>With trailed stars:
>>http://astrob.in/236516/B/
>>
>>Stars removed by using rejection during integration.
>>http://astrob.in/236516/0/
>>
>>Regards,
>>
>>Mike
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