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Pickering’s Triangle (Seimis 3-188)

It is a little early in the season to be imaging this object as it didn’t appear above my local horizon until 00:50 when I started the project earlier this month but with nights getting shorter as we approach the summer solstice, it made sense to make an early start even though it took several nights to capture the data while ducking and diving between the clouds and early morning mist!


Pickering’s Triangle is part of the supernova remnant known as The Veil Nebula in Cygnus. The Veil Nebula itself was discovered by William Herschel in September, 1784 but this faint region was only later discovered photographically in 1904 by Williamina Fleming at the Harvard Observatory. The discovery was made post publication of the New General Catalogue (NGC) so it isn’t included in the catalogue. Although it wouldn’t happen today (I hope!), the custom of the time was to credit the discovery to the lead astronomer, in this case Edward Charles Pickering, the director of the observatory.


Image Stats

Mount: Mesu 200
Telescope: Sky-Watcher Esprit 150
Flattener: Sky-Watcher Esprit specific
Camera: QSI 683 WSG-8
Filter: Astrodon 3nm Ha and 3nm OIII
Subframes: 6 x 1800 sec Ha, 13 x 1800 sec OIII
Integration: 9.5 hours
Control: CCD Commander
Capture: MaxIm DL
Calibration, Stacking and Deconvolution: PixInsight
Post-Processing: PhotoShop PS3


The nebula can be found in the north-west quadrant of the Veil Nebula near NGC 6974 and 79 (see whole Veil Nebula image below). Lying around 1,400 light years away, the beautiful filamentary elements are the expanding shock-wave from the progenitor star that went supernova here somewhere between 5,000 and 10,000 years ago.


Position within the Veil Nebula


Visually, the nebula responds well to the use of an OIII filter as the region is rich in OIII emissions as can be seen in the blue/green filaments in the above images.

Photographically this is a wonderful object that responds well to both LRGB and narrowband imaging and the example shown here was captured using Ha and OIII filters. Although there are sulphur emissions (SII) in this region, this object responds well to my favourite imaging method of 'bi-colour’. This process uses just Ha and OIII filtration wherein the OIII data is mapped to both the ‘Green’ and ‘Blue’ channels and the Ha is mapped to the ‘Red’ channel. The greyscale  images below show the individual Ha (left) and OIII (right) images used to produce this image. As you can see from the 'Stats' above, I have a whole load more Ha to collect to complete the image!

The individual Ha and OIII images



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Once again Steve, a lovely image accompanied by an informative report, Terrible the way underlings were treated back in the day :(


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Great image and a wonderfully informative post. 

I have been trying to catch the tail end of the galaxy season with the recently set up Esprit 150, I only have a Ha narrow band filter but looking forward to trying it out on this target.

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14 hours ago, John said:

"Pickerings Harem" or the Harvard Computers as they were also known included some very skilled and talented women

Thanks for the link, @John

9 hours ago, tomato said:

I have been trying to catch the tail end of the galaxy season with the recently set up Esprit 150, I only have a Ha narrow band filter but looking forward to trying it out on this target.

You'll be in heaven with that combination - some of my favourite images have been mono using just an Ha filter. Galaxies have never really excited me as much as the dusty stuff which is another reason for diving in early with this nebula as soon as it started to rise!

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4 minutes ago, whatablanker said:

Love the image. I will be doing the veil when to gets dark again. Like you said it rises far too late at the mo. I like the wide angle image.

The wide field of view was captured with a 100mm Vixen VSD 100 (f3.8)

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1 minute ago, steppenwolf said:

The wide field of view was captured with a 100mm Vixen VSD 100 (f3.8)

I'll be using my sigma 70 - 300 lens set at about 100 - 150mm. I don't normally use the scope between August and October as I like to catch the area around Cygnus in the summer. There is just so much to see.

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Well done Steve on being the 'early bird' and not an easy task to guide at a low altitude.  Lovely bi-colour.

Now, just programme a masterful mosaic with your Esprit and we'll all delight in the end result ?!

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15 hours ago, Barry-Wilson said:

Now, just programme a masterful mosaic with your Esprit and we'll all delight in the end result ?!

With that lovely wispy tail to trace out it would be quite a few tiles!

11 hours ago, swag72 said:

A great image and a very insightful post with all the additional information... many thanks for that it's extremely useful for everyone :) 

Thanks, Sara

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