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The Trapezium in M42


Roy Foreman

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A few nights ago I was imaging the Orion Nebula and also took some short exposures to try and record the trapezium stars. I was pleasantly surprised to discover that one image actually showed the E and F components as well !

Next time I try this I will use a longer focal length so that I don't have to crop the image so much.  The image of the whole nebula, which was taken at the same image scale,  shows the degree of cropping required !

Vital statistics :-

16" F/4.5 Reflector

Nikon D810a

Trapezium - 1 x 0.5 sec at ISO 1600

Nebula - 5 x 30 sec at ISO 1600

No filters

A welcome break in the clouds for an hour !

Half decent seeing !

trapezium-2 2021-02-10.jpg

M42 30s 2021-02-10.jpg

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I am fairly sure you have picked up G as well and there may be a hint of an unresolved H1+H2.

Conversion to greyscale followed by sky background removal and aggressive contrast stretching may make the situation clearer, though at the cost of aesthetic appeal.

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Wow - so I might just have done better than I thought. To be honest I'm not familiar with all the various components of the system, but I will look into it and see what I can identify. Thanks for the processing suggestion - I'll give it a go

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3 minutes ago, Roy Foreman said:

Wow - so I might just have done better than I thought. To be honest I'm not familiar with all the various components of the system, but I will look into it and see what I can identify. Thanks for the processing suggestion - I'll give it a go

https://web.archive.org/web/20140826115516/http://www.lvastronomy.com/observing-challenge/144-february-theta-1-orionis-the-trapezium

is what I used to identify the components.

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Tried messing around with this and the clearest I could come up with is below. The link you posted was really useful, thank you, however I was unable to match any of the semi resolved stars with those shown on the diagram.

Next clear night I will have another try - maybe a longer focal length to give more star separation enabling a longer exposure to be used. Now there's a challenge for me !

trapezium-2a.jpg

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56 minutes ago, CraigT82 said:

Fantastic!  Love both of those images. The wider field in particular has a really pleasing ethereal quality which I like. How is your reflector mounted?

Thank you - so glad you like the images !

I built the mount for the 16" myself. It is a fork mount - the fork itself is so heavy I can only just about lift it. The base and RA housing are built in the style of Astro Physics and Paramount, but obviously not to the same degree of precision !

Worm and wheel sets were supplied by Beacon Hill Telescopes - 14" diameter for RA, 12" for Dec.  Electrics were supplied by AWR Technology and the whole thing is fully GO TO and computer controlled.

Interestingly, the motors are so large and powerful that they are connected directly to the worm shafts - no gears, no belts, almost no backlash.

The OTA itself is from a Skywatcher Flextube Dobsonian - a cheap way of obtaining a decent optical set. 

One downside of building it myself - if anything goes wrong I'm on my own putting it right !

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12 minutes ago, Roy Foreman said:

Thank you - so glad you like the images !

I built the mount for the 16" myself. It is a fork mount - the fork itself is so heavy I can only just about lift it. The base and RA housing are built in the style of Astro Physics and Paramount, but obviously not to the same degree of precision !

Worm and wheel sets were supplied by Beacon Hill Telescopes - 14" diameter for RA, 12" for Dec.  Electrics were supplied by AWR Technology and the whole thing is fully GO TO and computer controlled.

Interestingly, the motors are so large and powerful that they are connected directly to the worm shafts - no gears, no belts, almost no backlash.

The OTA itself is from a Skywatcher Flextube Dobsonian - a cheap way of obtaining a decent optical set. 

One downside of building it myself - if anything goes wrong I'm on my own putting it right !

Wow what a set up! I'd be very interested do see some pics of it if you have any? I'd love to build a large fork mount but my skills are sadly lacking... in all the necessary areas!

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I've been meaning to take photos of it all for ages. The problem is in the confines of an observatory it is difficult to get far enough back to fit it all in ! Maybe I'll get down to doing some detail photos of  the various parts.

Incidentally, the entire thing was built using only hand tools - no machine shop, so it's amazing what you can do it you try - I have no training in metalwork. It took many years to build. Not a project for the faint hearted !

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