IC 1805 – “Cluster + Nebula” In Cassiopeia – December 2019 – Observer’s Challenge Report #131

A change to previous months preliminary information:    

For all future “early report” notes, images or sketches.  They need to be your completed report, which are ready to use in the Observer’s Challenge report.

Otherwise, it can be difficult “at times” to insure that the correct designated information is used in the Observer’s Challenge report.    

At times it can be difficult to keep up with all of the entries, especially when there are more than one submitted report by a participant.    Roger Ivester



December 2019

Report #131  

NGC 1805 “Cluster + Nebula” 

Compiled by:

Roger Ivester, North Carolina  


Sue French, New York  

“Sharing Observations and Bringing Amateur Astronomers Together”


IC 1805 is a 6.5-magnitude cluster about 62 stars that spans about 20 arcminutes. It’s nearly centered on the group’s brightest member, HIP 11832 shining at magnitude 7.1. The cluster is young at only 2.5-million years and we see it at a distance of roughly 6,500 light-years. IC 1805 is enveloped in and associated with the emission nebula Sharpless 2-190, commonly called the Heart Nebula, which sprawls across 1.6 º of sky.

Edward Emerson Barnard discovered IC 1805 photographically and included on the first two plates of his wonderful Photographic Atlas of Selected Regions of the Milky Way. The atlas can be viewed online at:

https://exhibit-archive.library.gatech.edu/barnard/      Sue French  


At current we have only three entries: 

IC 1805, December 2019, Observing Report by Mario Motta:

B&W image of IC 1805:  An H alpha image taken through my 6-inch refactor in 2015 for wide field. And has 7,  20 min subs, so 2 hours 20 min of H alpha.  

Color Image:  This was combined with 1 hour each of Oxygen 2 filter and Sulfur filter:  See attached.

IC 1805 (the Heart Nebula), North is to the right on this image, rotated to show the “heart” shape more readily.

Of course…to a cardiologist the Right heart (on the left, person facing you), is very “enlarged” so this is a rather sick heart, with what I would call right heart failure.    Mario Motta 





Observation Report by Chris Elledge:

I spent Saturday night observing IC 1805 through a variety of telescopes with various filters at the ATMoB Clubhouse. The best view that I got was through a 102 mm f/7 refractor with a 35mm eyepiece providing a 20x mag and 3.4˚FoV. I recommend using a UHC to see the most nebulosity. While the edges of the nebula were still difficult to determine exactly where they stopped, it was clear that areas around the nebula were darker than the area inside.

I actually found a Hydrogen Beta filter to be useful on this object. In my refractor with the Explore Scientific H-beta filter (on the wide side for bandwidth) I was able to observe that the outer edge of the nebula was slightly brighter than parts of the middle. Some mottling was visible within the nebula outside of the brighter star clusters. This filter makes everything else really faint.

I was able to observe the nebulosity in both my 10″ f/5 Dob (36x, 1.9˚) and the ATMoB 25-inch f/3.5 Dob (63x, 1.1˚). In both cases it required extensive panning of the view to determine that the field was brighter within the nebula than outside. It was difficult in both cases to determine where exactly the edge of the nebula was. Sitting the view on the edges of the nebula, I could tell than one side of the view was brighter than the other. Filters helped, but the view through the 20x power of the 102 mm refractor was better.


Low magnification definitely is important to this one. Probably works best with the biggest aperture you can find that still gives 20x or lower magnification at a reasonable exit pupil. I don’t think anything over 5-inches  will improve visibility. Don’t bother with OIII unless you want to just see the nebulosity around the bright clusters. UHC is ideal. H-beta is fun if you happen to have one that fits your lowest power eyepieces already.   Chris Elledge 


Observing Report by Sameer Bharadwaj 

William Optics GT71 w/ 0.8x flattener

Optolong L-enhance filter, Canon EOS 77D modified

12 x 360 seconds, Ioptron zeq25 guided with QHY5L2M

Pursued the Heart Nebula all summer with an unmodified camera with limited success. This is the object that finally motivated me to get the camera modified.




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