Comet Jacques - another one

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rwilkinson
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Comet Jacques - another one

Post by rwilkinson » Fri Jul 31, 2015 8:17 am

Around this time last year we had good views of Comet C/2014 E2 Jacques:
viewtopic.php?f=1&t=699

Well, Mr. Jacques (a Brazilian astronomer) has evidently been busy, as C/2015 F4 is also named after him. This one is close to perihelion now, but only around 10th magnitude. However it is currently very well-placed for observation, high in the sky in the constellation of Cygnus.

Last night it was very close to the famous double-star Albireo, so I found it quickly with my Atik 16IC camera on the back of the StarWave 80 refractor. There was quite a bit of wispy cloud around, and a full Moon, but I could just about make out the comet on each of the 1-minute exposures.
c2015f4_30jul.png
Comet C/2015 F4 Jacques on 30-Jul. 56x 1-minute using 16IC and StarWave80.
c2015f4_30jul.png (268.68 KiB) Viewed 4969 times
This stack shows how far it moved in an hour.

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Re: Comet Jacques - another one

Post by rwilkinson » Fri Aug 07, 2015 7:52 am

There was neither cloud nor moonlight last night, so I got the comet a little clearer - it's still very faint though (magnitude 10.5):
c2015f4_6aug.png
Comet Jacques on 6-Aug. 67x 1-min using Atik 16IC on SW80ED at f/4.6
c2015f4_6aug.png (259.69 KiB) Viewed 4939 times

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Re: Comet Jacques - another one

Post by rwilkinson » Sun Aug 16, 2015 1:19 pm

Last night I managed to get a better view of this faint comet, using the newly-repaired Bradford Robotic Telescope Galaxy Camera:
C2015F4_15aug.png
Comet Jacques on 15-Aug. 3x 120-sec (using B, V, & R filters) from a 14" SCT operating at f/5.3, from a mountain-top in Tenerife.
C2015F4_15aug.png (328.58 KiB) Viewed 4904 times

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Re: Comet Jacques - another one

Post by ANuttall » Mon Aug 17, 2015 11:11 am

the top two looks like my astro photos with the star trails

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Re: Comet Jacques - another one

Post by rwilkinson » Wed Aug 26, 2015 10:41 am

Last night the BRT Galaxy Camera got two pictures of the comet, about three and a half hours apart:
c2015f4_25aug.gif
3-min and 2-min exposures taken 3hr26min apart
c2015f4_25aug.gif (288.99 KiB) Viewed 4841 times
The first exposure was 1.5x longer than the second, so it shows more of the comet's tail (and faint background stars).

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Re: Comet Jacques - another one

Post by rwilkinson » Mon Sep 14, 2015 7:58 am

It's faded down to 12th magnitude now, however I still managed to detect it using my 70ED refractor from Norfolk. With the darker skies down there, I was able to remove my usual light-pollution filter, so "no photons turned away".
The comet was so faint that I couldn't see any trace of it on my 90-sec images, but once I'd aligned and stacked one hundred of these, it can be seen as the one stationary object in a field of trailed stars. Unfortunately it's partly masked by the trails of two faint background stars (which were too faint to show up in the databases I had loaded in the Cartes du Ciel planetarium program):
c2015f4_11sep.png
Comet Jacques on 11-Sep. Stack of 100x 90-sec images from Atik 16IC on TS70ED operating af f/4.6
c2015f4_11sep.png (328.69 KiB) Viewed 4709 times
This is prpbably the faintest comet I've managed to detect - and with my smallest telescope too!

I was really lucky to get such a long integrated exposure (of 150 minutes) - there was patchy cloud around that night, yet as my target was nearly overhead (in Lyra) it remained cloud-free - until ten minutes after I packed away, when the sky filled in completely!

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Re: Comet Jacques - another one

Post by rwilkinson » Sat Sep 19, 2015 7:58 am

Here's another image of the comet, exactly one week later:
c2015f4_18sep.png
C/2015 F4 from Bolton on 18-Sep. 21x 2-min using MX516 on C8 at f/3.3
c2015f4_18sep.png (182.26 KiB) Viewed 4664 times
Even though the comet has faded slightly, the larger imaging system shows it much more clearly than last week's image with my little refractor: now I'm using a 'scope with more than 8x the light-grasp, at a faster focal-ratio (thanks to my 0.33x focal reducer), and with about twice the focal-length too.
But for Bolton's light-polluted skies I need to shoot through an Orion broadband light-pollution filter, however this monochrome CCD will probably be more sensitive than the colour one which I used last week.

Incidentally, these 2-min unguided exposures are the longest I've ever managed with this combination (C8 on CG5 mount): I actually took 29 images, of which seven suffered from trailing (and one other was marred by a passing cloud).

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Re: Comet Jacques - another one

Post by rwilkinson » Sat Oct 03, 2015 8:58 am

I managed to get another image of this comet last night, before it fades into obscurity. Although the sky was quite hazy, the target was nearly overhead (near Vega), where the haze was thinnest.
This time I was using my StarWave 80ED refractor, along with my "new" HX916 CCD (giving a wider field-of-view), but I'd not got my mount set up quite as well as a fortnight ago, so I could only manage 90-sec unguided exposures.
I couldn't see the comet on the individual 90-sec exposures, but after some careful stacking of a couple of hours' data, it's clear enough:
c2015f4_2oct.png
C/2015 F4 on 2-Oct. 72x 90-sec using HX916 on StarWave 80ED at f/4.6.
c2015f4_2oct.png (346.84 KiB) Viewed 4611 times

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