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New nebula at HY Aqr?

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New nebula at HY Aqr?

This morning I analyzed CCD observations of comet 137P obtained on 2018 Oct 16 18:40 UT. The comet was located just 9 arcmin from HY Aqr, a Mira variable with no observations in the AAVSO database.

At the location of HY Aqr I found a circular nebula with a darker center, 40" in diameter, mag 13.2. The shape is reminiscent of a planetary nebula with two 15-16 mag condensations on the S and SW edge. Please see attached image with details.

I was able now (Oct 25, 19:30 UT) to acquire confirmation images in a partly cloudy sky and the nebula is still there. Will process these images ASAP.

I have not been able to find any information on such an object at this location in the web, VSX, SIMBAD or Aladin Lite. Can someone else please confirm?

The center coordinates of the nebula as measured on my image is

21 31 06.44 -07 34 22.4 (J2000)

Best wishes,


Johan Warell


Lindby Observatory (K60)

Skurup, Sweden





HQA's picture
HY Aqr

Hi Johan,

This looks like an imaging artifact to me.  The stars in the blowup window have similar profiles (kind of horseshoe shape), and you are using a focal reducer, which may impact image quality for something this red anyway with a clear filter.  If you take another image of the field, be sure to move HY Aqr into the center so that you remove any image distortion.  I'd also suggest trying an image with some filter, such as Halpha or tricolor R.  Any nebula would likely have Halpha in emission and show up nicely in those passbands.  As you mention, none of the existing surveys show any nebula, so I always take the cautious approach and see if it might be instrumental in nature.


Hi Arne,

Hi Arne,

Thanks for your quick reply. I managed to get a couple of images tonight with the same setup also showing the nebula, but with the object in the center of the FOV, the shape was not exactly the same. I bet your explanation is correct, but will try obtaining BVRI data as well with better conditions. I’m using an Alan Gee 2 corrector and have not observed such extremely red stars previously with it, so perhaps the effect is simply due to unfocused red light. 

Best, Johan

I made a series of filtered

I made a series of filtered CBVRI images this weekend with the same setup under good conditions. My conclusion is that the ”nebula” is caused by unfocussed NIR light that the Alan Gee corrector can not correct. Something that owners of f/10 SCT:s might want to watch out for, if the object is very red. 



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