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Comment on a comet

Discussion in 'The Lounge' started by SqueamishOssifrage, Jul 14, 2020.

  1. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    I fancy getting a few shots of Comet C/2020 F3 (NEOWISE) over the next few nights, but have never attempted anything like this before.

    I probably should have posted this somewhere else, but I need maximum footfall to get something worked out by tonight, hence the lounge.

    I could use advice on lens focal length - I would like to use my 500mm catadioptric, possibly with a 1.4x or 1.7x TC. Also, what order of exposure should I anticipate? It will be low in the sky, but there will be no, of very little, light pollution.

    I would really appreciate some guidance on this, as I won't be able to photograph it again until the 89th century, if we haven't been hit by an asteroid before then. :eek:

    No, seriously, I would like some pointers from those more experienced in this genre than I.
  2. AndyTake2

    AndyTake2 Well-Known Member

    Found this on DCW (hope it is ok to post!)

    Their guidance is a bit rough, but then again it really depends on the time of day or night you will photograph it.
    They state 5-10 seconds exposure, wide open ISO 800-3200.
    I haven't photographed a comet since Hyakutake in 1996 (I didn't have a camera for Hale-Bopp in 97:() so I will have to search around myself in order to find details on exposure etc.
    The one thing I would mention with using a big lens is that as magnification increases, so does apparent motion. A medium telephoto may get away with a few seconds exposure, but high magnifications may struggle without an equatorial mount.

    Our resident astrophotography expert will hopefully be along to give us some pointers.


    On FStoppers there is an article where the photographer used F2.8, 1.3 second exposure at ISO 400.
    It just goes to show whatever you do, experiment. What you photograph, how much light is in the sky as well as the tech specs of your camera and lens are going to have a huge impact.

    If the weather is ok, I'm just going to take two cameras on tripods with different lenses and hope for the best.
    I may even try an infra-red shot with the camera Spinno was kind enough to gift to me.
    Last edited: Jul 14, 2020
    SqueamishOssifrage likes this.
  3. Derek W

    Derek W Well-Known Member

    @DaveS would be a good person to ask about the comet and how to photograph it
  4. AndyTake2

    AndyTake2 Well-Known Member

    That's the expert I was thinking of.
    Where is he?
    Come on, we've been here for more than 5 minutes!:D
    Derek W likes this.
  5. Malcolm_Stewart

    Malcolm_Stewart Well-Known Member

    Living in Milton Keynes, I used to be an active member of the OU Astro Club, and if you click on the "SkyNotes" link near the top of their website, link below, you'll get a several page pdf which may be of some help.
    Good luck - my attempts at Hale-Bopp weren't worth much.

  6. AndyTake2

    AndyTake2 Well-Known Member

    I think 97 was about when my OM10q fell to bits, so I didn't have the opportunity to photograph it.
    Or rather I didn't have the camera - I don't think I would have had a better opportunity if I were standing on it.
    I lived in Norfolk, and it was beautifully clear, but I also visited my brother in Ireland. It was gobsmacking. we went out to the west coast and were there at night. No lights, nothing but clear dark skies, and the comet's tail had just split in two. It has to be the most awe-inspiring sight I have ever seen in the sky.
  7. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    I thought of him, but didn't flag him, as it seemed a bit like getting a big game hunter to put down the family cat!
    AndyTake2, DaveS and Craig20264 like this.
  8. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    Thanks for all that good information. It reminded me of the five hundred rule, and as my cameras are not that good above ISO 1600, I am stuck at around 100mm. Looks like a job for my Sigma 105mm f:2.8 Macro (well, it's going to be a pretty small dot in the sky), which is sharper then a very sharp thing wide open - the AP comparative test lens in days gone by.
    AndyTake2 likes this.
  9. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    I have had a look at the link provided by @AndyTake2 and checked the exposures of the three examples presented. First I adjusted to ISO 1600, which I plan to use, and then further adjusted to f:2.8 and f:4.0.

    The first one gives an exposure of 4 seconds, the second 10 seconds, and the third 8 seconds. I am going to discard the first, as I am not sure that it is relevant, as it a very light shot compared to the other two, and I am not confident that it has not been worked on. The other two are sufficiently close to generate a level of confidence as a starting point.

    Tonight will be just a recce, with the 105mm mentioned above at f:2.8, and my Sigma 70mm f:2.8 Macro - the sharpest lens I have ever used - at f:4. On the hill behind my house there is a wind farm, spread over a large area. My plan is to find a spot where a couple of the turbines bracket the comet.

    Well, that's Plan A, anyway! :D
  10. SXH

    SXH Well-Known Member

    Ah, but "The best laid schemes o’ Mice an’ Men Gang aft agley".

    Do something funny to your command of English too... ;)
  11. DaveS

    DaveS Well-Known Member

    It's very low in the NNW from about 11 o/c, gradually getting lower as it passed north, then rising again from about 1o/c onwards. I got a good photo with my XT1, 3200 iso, 3 sec 90mm Summicron R at f/2.
    Will try and scale a photo for here.
    It should be naked eye, even from London.
    The further north you are the higher it will appear. Currently it's about 5-6 Deg from the south coast, but rising each day.
    My mistake, it was 1600 ISO
    AndyTake2 and SqueamishOssifrage like this.
  12. DaveS

    DaveS Well-Known Member

    Here you go. Straight off the card, through Affinity Photo for scaling and export as JPEG. This was from a grass triangle at the junction of Bull Lane and Swyre Road

    Comet Neowise.jpg
    I reckon Squeamish will have to wait until the small hours near dawn before it's high enough from Cyprus.
    Craig20264, Petrochemist, SXH and 3 others like this.
  13. Mark101

    Mark101 Well-Known Member

    Nicely done Dave. Oh how I miss my Astronomy as a hobby.
  14. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    Great stuff, thanks - although I'm in Cyprus. It should be visible to the NW after nautical twilight at 20:28. The exposure you used is close to the other two (12 seconds adjusted to f:4), so I am now a happy teddy that I can get it right with some bracketing.
  15. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    Yeah - I got my sums wrong - I need morning nautical twilight, not evening.
  16. DaveS

    DaveS Well-Known Member

    Thanks Mark.

    It was easy naked eye from here, but then I have fairly dark skies. Through my 10x50 bins it was spectacular.
  17. AndyTake2

    AndyTake2 Well-Known Member

    You realise we are all going to have to try using our biggest lens now?!

    If the skies are clear (weather report says that we should have clear night skies from Friday) then I will hopefully get out to one of a couple of spots I think would be suitable. I have a couple of F/2.8 lenses - a 70-200 and the beautiful 27-70 Nikon, and would like to see if I can get a couple of shots, especially if I can get it reflected in the lake at one of my chosen sites; but also give it a go with either the Nikon 70-300mm F5.6 (about 10x magnification) or the Sigma 150-500, but that is F6.3 (about 17 x magnification)
  18. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    Damned annoyed with myself! :mad:

    Years ago, when I was working for HP, I wrote an Astro-Nav program for marine navigation, first in Fortran, then in HP Basic, for certain HP devices, way before the advent of even Transit satnav, let alone GPS. As a hobby project, I am now rewriting it in Java for PC and Android, together with lots of bells and whistles arising from more powerful hardware. It has a few internal datasets containing raw data for the sun, moon, the four navigational planets, the 57 USNO navigational stars plus Polaris, and the full Harvard Bright Star catalogue. I got today's approximate Right Ascension and Declination for NEOWISE from the web, and stuffed it into the Harvard dataset as a bright star, and whoopee! It was observable during nautical twilight in Larnaca today. Unfortunately, I haven't built any kind of user interface to display output data yet, so I just looked in the logfile to see what bodies got thrown up as observable, together with altitude and azimuth, at the start and finish of nautical twilight today. At this stage, the output is in input-dataset order - so no way to tell whether it is morning or evening twilight. I didn't check! I just assumed it was still to come. :(

    On the plus side, this evening at 20:28 it will still be about 33°C, but at 04:38 tomorrow morning it will around 23°C. That's a win!

    Another win is that apart from the yet to built UI showing AM and PM twilight, which was obviously always part of the design, it will show the two next twilights from the time of checking.

    Note to self: Drink several beers tonight, so I have to go to the loo at 04:00 tomorrow. :D
    DaveS and AndyTake2 like this.
  19. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    Back to the drawing board!

    Just done a daylight recce. I haven't been up the mini-mountain behind the house this year, and this winter we had some torrential downpours. The track to the North east facing site I was planning t use has been washed away. Even with 4WD I wouldn't risk it in daylight, let only at night, mainly owing to the 600 foot drop at the edge of the track. Well, actually, it is the track now. I'm not afraid of heights, but am petrified by 600 foot drops, so I came home for a cup of tea and a scone. Best thong to do really.

    Still, one plus to the trip - I saw a polar bear up a tree on the way back.


    I will probably go to Stavrovouni Monastery for the attempt tomorrow, which is on the high peak behind the bear.
  20. GeoffR

    GeoffR Well-Known Member

    Did Robert Burns have a grasp of English as we know it?
    SXH likes this.

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