3 replies to this topic

[james7ca]

This asterism is just a little south of the star Arcturus and for observers in the mid-northern latitudes it is fairly close to the zenith shortly after the start of astronomical dusk at this time of the year. I captured this image over the last two night in an attempt to get something before the marine-layer clouds arrived as they do almost every night here in San Diego during the spring and summer.

 

You can click the preview/thumbnail to view the full-sized image as hosted here on CN (1600 x 1200 pixels). North is oriented up and there are additional capture details in the image captions. The 6th magnitude star CN Boötis is located toward the top center left of the image.

 

Image processing with PixInsight and Photoshop 2025.

 

Last week I posted an image of Arcturus that also included this asterism, but in that image these stars were right at the edge of the field. But, if you are interested to see how this asterism looks in relation to the bright star Arcturus here is a link to that post on CN:

 

  https://www.cloudyni.../#entry14139541

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Edited by james7ca, 23 May 2025 - 09:21 PM.

[james7ca]

Thanks for the likes.

 

I was wondering what some of the small and faint "fuzzies" were in my image (noise or something else) and thus I did an annotation in PixInsight to see if it could identify what was showing in the background of my image. Well, it looks like a very high percentage of these objects were galaxies. I found a few that were listed in SkySafari as magnitude 18 objects and even a smaller number that apparently had distances of up to 2 billion light years. In the below crop from the full APS-C frame there are at least 14 galaxies that are near to the Napoleon's Hat asterism.

 

After that I started to wonder whether my field covered what is known as the Boötes Void or the "Great Nothing" that is located in the constellation Boötes and although I couldn't find a good map of that object on the internet I'm pretty sure the void is further north. The Boötes Void is a large area of deep space that has practically no galaxies and that is hundreds of millions of light years in diameter. Since most of the galaxies that I recorded are anywhere from 250 million to 1 billion lights years away I thought this might be on the edge of the void, but since there are only a dozen or so known galaxies in the void I'm pretty sure this isn't within the void. The nearest and largest galaxy that I recorded was close to the edge of the APS-C frame and is IC 984, at magnitude 14.4 and at a distance of 250 million light years (see below crops).

 

I also did a comparison between my image and the PanSTARRS survey (also shown below). This reveals that there is at least one fairly bright galaxy (below the "0" and "9" in the label "PGC50934") that wasn't annotated by PixInsight and I found many similar omissions over the remainder of the full APS-C field. The galaxy PGC50934 is located just below center in the large image (below) that includes Napoleon's Hat.

 

[UPDATE]

I noticed that the captions on the images of Napoleon's Hat incorrectly indicate that these images were taken with a Nikon Z5. The camera was actually a Nikon Z50 II.

[/UPDATE]

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Edited by james7ca, 27 May 2025 - 02:58 AM.

[james7ca]

I was able to salvage some more subs from an earlier session and with improved processing I ended up with a deeper image. This one got down to just below magnitude 18. Same camera and lens, just more subs.

 

The full capture details are in the image captions.

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[james7ca]

Here is a wider crop based upon the same set of subs that were used for the immediately previous post. This includes the star Arcturus and makes for a more dramatic presentation. North is oriented up in all of these shots.

 

If you look closely in the previous shots you can still see some of the flare/glare from Arcturus, but it shows up more like a minor increase in the brightness of the background sky whereas here you can see the full extent of the halo. This area probably deserves a reframing to better balance the centering of both Napoleon's Hat and the star Arcturus. I had one night where I was centered on Arcturus and another set of sessions where I was centered on Napoleon's Hat and this is the best framing I could get when using all of the subs.

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Edited by james7ca, 27 May 2025 - 09:12 AM.