The Coathanger and the Little Cocoon

[mftoet]

Last weekend we had an Indian Summer in the Netherlands. There was an announcement on the Dutch astroforum that people would gather on the 'Afsluitdijk' for an observing session on Sunday evening. That triggered me to enjoy them with my Tak Epsilon-180ED.

I 'discovered' the Coathanger (Collinder 399 a.k.a. Brocchi's Cluster) with a pair of binoculars when I got involved in astronomy about 20 years ago. It's such a nice asterism. For this image I decided to frame the Coathanger with the Little Cocoon Nebula (Sh2-82). NGC 6802 can also been seen.

Exposed for 3 hours and 30 minutes (42x 5 min. subs at ISO 1600) with a Canon EOS 5D Mark II. Data reduction with AstroPixelProcessor, using 131 dark frames and 30 (bias corrected) flat frames. Post-processing in Photoshop (mainly) and PixInsight (Canon banding reduction script and SCNR to remove a green cast).

http://www.mauricetoet.nl/Deep-sky/i-HsxpNdp/A

   

[toxic]

very nice indeed Maurice  

[Paul1]

Very nice Maurice.

Regards  Paul 

 

 

[Ouroboros]

That's lovely. The coat hanger is one of my favourites, and nicely positioned at the moment. I nearly always look for it when out with the binoculars at this time of year.  Interesting to see the vast sea of stars in the background that your image reveals. Good to see this is a DSLR image. When I first looked at it I thought it would turn out to be an image acquired with something like a ZWO1600. 

[Ruud]

Wonderful! It's so beautiful!

[ollypenrice]

A great idea for an image (not for the first time from Maurice!)

Already at this distance from the centre of the Milky Way the golden colours are starting to appear and will lighten and brighten as we head towards Sagittarius.

A super new context for the Coathanger. 

Olly

[mftoet]

Thank you, guys.

@Ouroboros: my evolution for 20 years in astrophotography has been a bit peculiar. I once started with analogue photography (first 35mm, later medium format), switched to CCD in 2008, but have settled for a DSLR since 2015. The main reason for 'ditching' the CCD camera was it's unreliability - due to USB and software/Windows issues - for mobile use. Nowadays I work with a Lacerta MGEN standalone autoguider that also triggers the DSLR and dithers (see animation below) between subs. It's relatively easy to setup and breakdown. The less cables the merrier.

 

 

[wimvb]

Great image, Maurice. I guess that the Afsluitdijk is one of the better locations in the Netherlands, as far as free horizon and light pollution is concerned. But it must have been windy.

What's causing the vertical diffraction spike just making its way into the image from below? There's only one other star in your image that has such a spike.

[mftoet]

Thank you, Wim. The Afsluitdijk is indeed one of the better locations in the Netherlands. Some Frisian Islands have better conditions, but are difficult (if not impossible) and impractical to reach by car. The Afsluitdijk can be windy, but if you choose your observing spot wisely, the large basalt boulders function as wind barriers.

The vertical diffraction spike is caused by the reflection of a bright star outside the field of view on the edge of the DSLR mirror. Painting the mirror edge black will probably solve (or reduce) the issue.  

[tooth_dr]

Fabulous image. Amazing how much star colour at a high iso! Using darks and dithering too!

[The Admiral]

That's a lovely image Maurice.

I'm becoming ever more impressed with what an Epsilon-180ED can achieve, especially in your clearly most capable hands. Some seem to struggle to collimate it, but how have you found it? I like your approach of using a DSLR and standalone autoguider .

Ian.

[mftoet]

I struggled with the collimation in the beginning. The Takahashi cheshire/sight tube and pinhole eyepiece deliver the best results in my case. The support construction of the mirrors is very rigid and therefore the collimation very stable. I never rotate the focuser as it can mess up the collimation depending on how 'square' you retighten the focuser. Instead, I just rotate the tube assemble in its rings (for this image at an angle of 45 degrees). The Mach1, with spring loaded gears, doesn't seem bothered by the slight imbalance caused by this.

Stars in (the corners of) my images aren't perfect. I came to the conclusion that this is caused by a slight tilt of the sensor in my Baader modified 5D MKII. In the top left corner stars look like streaks pointed in this direction \ meaning the sensor is too close to the field corrector. In the bottom right corner stars look like commas in this direction / meaning the sensor too far from the field corrector. I have to sort this out by shimming the wide T-ring.

[MartinFransson]

I had a look at your website and wow... the stuff you pull out with a DSLR! Truly inspiring!

[mftoet]

Thank you, Martin!