Observation by Nick James: PV Cep and Gyulbudaghian's nebula

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Nick James


Nick James


2020 Aug 21 - 22:45


2020 Aug 22 - 10:20


Gyulbudaghian's variable nebula

  • Celestron HD11 + FLI6303



Chelmsford, UK

Target name

Gyulbudaghian's nebula


PV Cep and Gyulbudaghian's nebula

About this image

As Mike Harlow has pointed out on his page PV Cep is very faint at the moment (I get 17.8 unfiltered using UCAC4 R mags) and the nebula is all but invisible apart from a thin line on the eastern edge.

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Mike Harlow
Mike Harlow, 2020 Aug 22 - 16:16 UTC

Hi Nick,

I still haven't got my act together re. photometry so it's nice to see "very faint" quantified!!!  A quick look at the AAVSO chart for this object suggests their photometric sequence only goes down to ~mag 14.  Is there a better sequence that reaches 17 - 18 where it is now?  I see you refer to 'UCAC4' in you image details...not something I'm familiar with...maybe you could point me in the right direction?



Nick James
Nick James, 2020 Aug 22 - 17:09 UTC

Is the USNO CCD Astrograph catalog. It contains reference magnitudes for a lot of stars and Astrometrica uses these to determine the magnitude zero point for the frame. The frame is unfiltered but I have chosen R magnitudes as the reference to use since these most closely match the response of my camera. In this case the ZP is 25.75 which is about average for a 60s exposure with my camera and telescope. On very transparent nights I can get to 26.2 or so. The ZP is used to convert between counts and magnitudes so it is then possible to measure the magnitude of any object in the field by clicking on it in Astrometrica. 

Mike Harlow
Mike Harlow, 2020 Aug 22 - 18:08 UTC

Thanks Nick, that's really neat.  Something to look into on cloudy nights...


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