Graeme Coates

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  • in reply to: ER Uma and RZ Lmi: Observations requested. #583664
    Graeme Coates
    Spectator

    2021-01-07 2154-2208UT  ER UMa Mag 13.6V 
    2021-01-07 2218-2234UT RZ LMi Mag 17.1V

    (350mm Newt, ST2000XM)

    in reply to: ER Uma and RZ Lmi: Observations requested. #583657
    Graeme Coates
    Spectator

    Yes – it needs much longer exposures than with my 350mm newt at home(!) and there’s greater uncertainty, but definitely can determine that it’s not in outburst

    Clear skies offer some definite advantage, and it’s much darker there as well than my garden here in the UK! 

    Unfortunately, not possible last night.

    in reply to: ER Uma and RZ Lmi: Observations requested. #583643
    Graeme Coates
    Spectator

    04-01-2021 0340-0421UT: ER UMa Mag. 14.8-15.0 (TG)

    in reply to: IX Dra: observations requested #583641
    Graeme Coates
    Spectator

    2021-01-03 1851UT – Better conditions than yesterday (better transparency).

    Mag 17.0 (CV)

    in reply to: IX Dra: observations requested #583635
    Graeme Coates
    Spectator

    I have this somewhere around Mag 17.5-17.9 (CV) at 18:45UT this evening (2nd Jan 2021) – not a very accurate measurement as running from Spain with a small widefield refractor, and it’s already getting low at dusk – 8 oktas at home…  

    (This a single 10min exposure (ED80 + STF8300M)

    in reply to: At 2020nlb – a possible Supernova in M85 #582700
    Graeme Coates
    Spectator

    Looks like this is brightening significantly – https://www.virtualtelescope.eu/2020/06/29/supernova-sn-2020nlb-in-messier-85-is-rising-an-image-28-june-2020/ put it at Mag 14.4 (June 28.8707).

    in reply to: CMOS v CCD for photometry? #582610
    Graeme Coates
    Spectator

    I’d actually say that (certainly for the blue curve) that the dark current is not linear in that plot – a proper analysis would show how close to a straight line it is. A few hundred ADU out may introduce a reasonable systematic error. 

    Anecdotally, using my QHY163M (same chip as the 1600) for deep sky imaging I’ve found that scaling (and even allowing Pixinsight to try “optimizing” darks) just doesn’t work properly. If you create a dark library for a few different exposures  (10/20/30/45/60/90/120/180/300) then they can be reused for quite a while before needing rebuilding – just make sure the offset and gain are the same as for the lights.

    A useful activity for a cloudy night or two…

    in reply to: PQ And in very rare outburst #582570
    Graeme Coates
    Spectator

    Someone (ahem…) years ago decided to build the observatory due south of my wife’s office – not sure she’d be happy with a demolition job to have half a chance of an observation of this one! (I think even then, there’s a large ash tree that might get in the way!)

    in reply to: Photometry on Supernovae with bright host galaxies? #582462
    Graeme Coates
    Spectator

    Great – thanks all for your thoughts. I played around a little with the varying radii of the annulus and it actually seemed to be reasonably stable in terms of calculated magnitudes. I’ll tabulate the results and pop them here in when I get chance to sit down and do it.

    Interestingly, the figures I see in running this initially are a good half magnitude lower than other estimates I’ve seen – clearly this will be due to subtraction of flux from M61 – and it will disagree with visual estimates that have no way of doing that! 

    in reply to: Photometry on Supernovae with bright host galaxies? #582452
    Graeme Coates
    Spectator

    Thanks Robin – yep – certainly don’t have the luxury of subtracting either image pre-SN like the surveys 😉 

    I wonder if anyone has a suggestion on software to allow background modelling to allow me to reduce the data I have? AIJ doesn’t look to have this feature (it allows aperture photometry with background subtraction via an annulus, and (I suppose by setting the inner and outer background radii to the same value) PSF photometry without any background correction – possibly more accurate than the former, but then still prone to inaccuracies… 

     

Viewing 10 posts - 21 through 30 (of 30 total)