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An odd idea for a one trick ponny wide field refractor

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#1 starcanoe

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Posted 02 March 2021 - 09:50 AM

After a few decade hiatus of not doing more than an occasional public star gaze...a few years ago I got back into it fairly heavy.

 

Most club members usually had the C8 type scopes or the larger dobs.

 

And one aspect of that was....besides binocs...non of those scopes were really the right tool for the job for the handful of larger clusters like M45....

 

So, I've been meaning to rig up a smaller refractor with true field of view sizes that are appropriate. But the other night I could not sleep....got to thinking about those refractor views...particularly how nice they can be on the cheap when you pair a relatively slow refractor with a 2 inch format long focal length lens...which got me to thinking of the advantages of such refractor views in particular...such as really nice contrast....pinpoint stars...no secondary obstruction....and no diffraction spikes...

 

Then a herectical thought hit me. Imagine a nice contrasty refractor view of M45 perfectly framed. Now imagine some serious diffraction spikes (like those caused by a 4 vane spider).

 

An optical perfectionist (and or a high $$$ refractor purist) would probably get the vapors at just the thought of purposely introducing diffraction spikes on the view. But random Joe Public observer certainly won't. He or she might even think the diffraction spikes make the image better.

 

Now, I've never been particularly bothered by diffraction spikes...besides on the planets...that just doesn't feel right.

 

But up to this point I've never entertained the notion of purposely ADDING them for "artistic reasons" so to speak with a visual view.

 

Another project to try once my life settles down a bit, the weather improves, and we get back into the summer swing of public star gazes around here.

 

Imagine a scope where you can easily add diffraction spikes...even have multiple masks so that you can choose the appropriate diffraction spike strength...rotate the spikes for optimum placement...heck even try other number spikes besides 4....5 would probably look pretty cool.


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#2 ccaissie

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Posted 02 March 2021 - 10:00 AM

Camera and photo buffs have screens that do that....introduce diffraction effects.  You could do that by finding a filter body that screws onto the eyepiece barrel and stick a couple pieces of wire to create the spikes?

 

Make a lens cap and stretch wires across the aperture?  Heck, just drag a greasy finger across the objective...that always works to create diffraction effects for me....8^)  



#3 starcanoe

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Posted 02 March 2021 - 10:05 AM

Yes...I've seen those filters and software that adds spikes (generally for no astro applications). I think I'd just go for a mask that goes in front of the objective. Would be nice to have an appropriate selection that by pulling on a rod or flipping a lever pops up the one you want in front of main lens.

 

And maybe we can get Tom Dey to use one of those "glamour shots" filters when he post picture of himself with his various optical toys? smile.gif


Edited by starcanoe, 02 March 2021 - 10:06 AM.


#4 TOMDEY

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Posted 02 March 2021 - 11:07 AM

Nice! Back around 1980 I also got that idea, and added crosses to my press camera that takes 4x5-inch glass plate emulsions. You can see my intentionally-introduced diffraction spikes dutifully manifesting on Jupiter there in the middle. The original prints are exquisitely resolved, with graceful spikes on all of the bright stars.    Tom

 

~click on~ >>>

Attached Thumbnails

  • 19 SAGITTARIUS JPG Jupiter in Sagittarius Tom press cam with cross at lens.jpg

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#5 starcanoe

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Posted 02 March 2021 - 11:22 AM

Yep...had the idea myself for PHOTOS back in the day...just never got round to it or bought the filters at yea ole camera store and haberdashery.....back when you had to do it with detectors based upon animal products.

 

But until the other night I had never made that last "logical" step of doing it "live" for visual use...obvious in hindsight I suppose.

 

Was also always a bit tickled that one could use diffraction spikes to help one more accurately determine a stars position on a plate....using an optical "defect" to ones advantage...



#6 ccaissie

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Posted 02 March 2021 - 12:22 PM

Akira Fuji used a slight diffusion in his constellation photos....the extra glow around bright stars increased their diameter and enhanced the distinction between star magnitudes.

 

https://www.davidmal...source/Ori.html


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#7 starcanoe

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Posted 03 March 2021 - 08:54 AM

Occurred to me last night....the double star Alberio might look pretty cool with some strong diffraction spikes oriented properly.




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