Bolton Astronomical Society

Imaging on stilts?
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Author:  rwilkinson [ Wed Feb 24, 2016 11:29 am ]
Post subject:  Imaging on stilts?

Last night I tried to catch comet 2013 X1 PanSTARRS low down in the West in the evening twilight. But the only way I can see in that direction is by setting up in the passageway outside the back door, looking over the side-gate:
File comment: Overhead imaging set-up, looking over the side-gate. Note the street-lamp just across the road!
imagingonstilts.jpg [ 217.62 KiB | Viewed 1672 times ]
I used the lightweight Celestron LCM mount on my speaker-stand tripod to raise my imaging system (the HX916 camera fitted with a Pentax 135mm lens) to eye-level, whilst keeping it screened from the street-lamp opposite.
But by the time I'd got everthing set up, the comet had sunk lower in the sky so I ended up extending the tripod column so high that I needed a step-stool to reach the camera (this over-head imaging reminded me of Carl's Cabin and the Sharples Space-deck!). And now it was in the full glare of the street-lamp too.
But then the comet "set" behind the houses opposite before I could catch it. :(

So I ended up pointing higher in the sky at Andromeda for a few minutes before packing it away:
File comment: M31, imaged from tracking alt-az mount. 10x 45-sec using HX916 with Pentax 135mm telephoto lens at f/4.
m31.png [ 215.78 KiB | Viewed 1672 times ]
I think that the strange artifacts on the right of the frame may be fronds from our neighbours' hanging-basket!
But I was surprised how much faint detail I'd managed to catch, even though I was pointing straight over a very bright street-lamp - the low-cost SkyWatcher LPR filter must have been quite effective.

Author:  rwilkinson [ Thu Feb 25, 2016 8:01 am ]
Post subject:  Re: Imaging on stilts?

Some clear sky to the West at dusk last night gave me a second chance to try this experiment.
I'd put my tripod up to its full height, so could see all the way down to my "horizon":
File comment: My view of the Western horizon. Single 25-sec with 135mm f/4 telephoto lens.
rooftops.png [ 188.93 KiB | Viewed 1794 times ]

Although I couldn't see any trace of the comet on my individual images, once I'd aligned and stacked a couple of dozen (and removed the background gradient), it was definitely there:
File comment: Comet C/2013 X1 on 24-Feb. 24x 25-sec using HX916 with Pentax 135mm lens at f/4.
c2013x1_24feb.png [ 383.19 KiB | Viewed 1794 times ]

This isn't the faintest comet I've imaged, but detecting it through the glare of the street-lamp has made it my most challenging to date. It's currently being reported at an integrated magnitude of around 9, but the two faint stars close to it on my image are magnitude 11.

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