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Old 10-04-2024, 12:12 AM
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Drac0 (Mark)
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Capturing Comets?

Hi all,

Have we got anyone here who chases comets on a regular basis? Developing an interest in this & hoping to catch 12P/Pons-Brooks around Anzac day as my first. But looking at getting many more over the coming months but have noticed most are fairly dim (MAG 10 or dimmer). Just after some good resources on imaging, tracking/guiding & processing.

Due to the limited time available for the brighter ones (near sunrise/sunset) my thinking is a series of longer exposures (120-180 sec) for the comet itself & some shorter ones for the stars, stacked separately then combined. Haven't even decided on what gear to use yet, but probably just a DSLR for my first attempts, rather than trying LRGB too soon.

This (and the next few months) will be my prep for the next very bright comet - C/2023 A3 (Tsuchinshan-ATLAS) - which will be visible just before sunrise late Sept/early Oct estimated to be around Mag 0.50!

Any help/guidance/pointers/resources will be greatly appreciated.

Cheers,
Mark
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Old 10-04-2024, 08:58 AM
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OzEclipse (Joe Cali)
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Hi Mark,

I wouldn't say I'm a regular comet chaser but I have done some. The full moon will make an Anzac capture difficult. It's just southwest of a 3.5% waxing crescent tonight. I'm running a nightscape photography workshop this month and the field trip is tonight near Boorowa. I'm going to have them have a go at it as one project. We're fighting twilight tonight. So we'll see. 12P has a steep orbital inclination (i=74 deg) so it follows the twilight band and doesn't climb high out of the twilight even into May. This means you will always be battling quite short observing windows. A short exposure time capture strategy might be best

The exposure sequencing and processing strategy depends entirely upon the motion of the comet relative to background stars, how long the observing window is, background light from LP or twilight.

Comet Leonard was a similar total magnitude but bigger angular area so I'd expect 12P to have a higher surface brightness. Here are some photos with exposures embedded on the images. Leonard also had a short window but each night after Christmas I had about 1 hr of dark sky capture time.

Joe
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Last edited by OzEclipse; 10-04-2024 at 09:10 AM.
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Old 10-04-2024, 10:30 AM
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Drac0 (Mark)
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Thanks Joe,

Nice captures, love the colour in the last one. Unmodified camera? Already got me thinking about what focal length to use - might need to go wider than I was thinking. I know the moon will be a bit of an issue around my planned dates but hoping shooting west with it being low in the east won't hurt too much. Will have to see how it goes & probably try over a few nights into May as it climbs a little higher (and dimmer).

Cheers,
Mark
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Old 11-04-2024, 02:04 AM
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OzEclipse (Joe Cali)
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Quote:
Originally Posted by Drac0 View Post
Thanks Joe,

Nice captures, love the colour in the last one. Unmodified camera? Already got me thinking about what focal length to use - might need to go wider than I was thinking. I know the moon will be a bit of an issue around my planned dates but hoping shooting west with it being low in the east won't hurt too much. Will have to see how it goes & probably try over a few nights into May as it climbs a little higher (and dimmer).

Cheers,
Mark
Hi Mark,

Unmodified camera? Yes it's an unmodded Pentax K1.

Joe
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Old 11-04-2024, 08:41 AM
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cafuego (Peter)
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Quote:
Originally Posted by Drac0 View Post
Already got me thinking about what focal length to use - might need to go wider than I was thinking.
I also managed to catch Leonard between xmas and new year a few years back; I went to friends bush block overnight for that, so the horizons were as dark as they could be.

The nice thing about a comet like that is you will get nice details no matter the focal length. I shot at 2000mm (10s), 200mm (30s) and 70mm (10s). The telescope shot is using an ASI294MC and the other two are an unmodified Nikon D750 on a simple (badly aligned) tracker.
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Old 11-04-2024, 12:13 PM
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Originally Posted by cafuego View Post
I also managed to catch Leonard between xmas and new year a few years back; I went to friends bush block overnight for that, so the horizons were as dark as they could be.

The nice thing about a comet like that is you will get nice details no matter the focal length. I shot at 2000mm (10s), 200mm (30s) and 70mm (10s). The telescope shot is using an ASI294MC and the other two are an unmodified Nikon D750 on a simple (badly aligned) tracker.
Thanks Peter,

I think I will probably just start with something like a 100mm lens & work to longer as I get a real idea of how it comes out & it gets a little dimmer. Luckily I do have some nice dark locations not too far away - comets early, DSO later.

Then I'll have time to hopefully chase some of the MAG 10+ ones in the coming months. These brighter ones are always near the horizon at sunrise/sunset so looking at probably only 40 mins to 60 mins imaging time at most on any particular night. Can get the dimmer ones much higher in the sky but will require more time as well.

Nice captures too, thanks for the input.

Cheers,
Mark
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Old 21-04-2024, 12:22 PM
Leo.G (Leo)
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Tonight is supposed to be the night for 12P. Cloudy as expected despite the weather thing on my phone insisting it's sunny all day. It's far from sunny but it's just past midday, the sky could clear (and I could win $150,000,000 on Powerball one day).
RIGHT!
I will set up my little Megrez 80mm (first model, semi APO whatever that means).
As for tracking I have absolutely no idea but I'll just set up and see if maybe I can get a few quick shots with the D810 through it.
I'd like to go up to a local lookout but whether it's worth the trouble carrying the gear to the place or not. I might drive up earlier and have a look if there's somewhere half decent to set my mount up. I don't have a spare charged battery for the mount, my old battery pack died and I haven't gotten a replacement yet. I'm wanting LifePo4 but they are far from cheap, light but expensive. I can plug something into my cars lighter socket or just play without power.
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Old 21-04-2024, 06:17 PM
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Good luck Leo. I'm leaving it for a few more days to let it get a little higher in the sky after sunset - it should still be good over the next couple of weeks (I hope).

Cheers,
Mark
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Old 21-04-2024, 08:00 PM
Leo.G (Leo)
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I found the line of 30+ foot high tress down my neighbours fence line made my observations impossible. I couldn't locate it with Stellarium (could locate it with Stellarium but not in my line of sight), binoculars or the Megrez.
I'll rely on Stellarium and Binoculars a little later I think, I've read it will be locatable with a telescope into May. Higher in the sky I might even be able to use the RC8 and the Player One 178 (ZWO ASI 178 equivalent sensor) camera. It will be a lot colder here just west of the Blue Mountains by then. I think I need to look into a dew band for the secondary mirror (it's fogged in the past while the primary has remained clear ( I'm assuming the secondary fogged, it could have been the camera sensor, likely using my Nikon D810 then)).
I'm particular about letting all equipment acclimatise before use, normally a good hour plus because that allows setting up in daylight.

Last edited by Leo.G; 22-04-2024 at 11:48 AM.
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