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Old 31-07-2022, 11:36 PM
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Stonius (Markus)
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Diffraction spikes, yay or nay?

I've heard a few people express a preference for images without diffraction spikes, and who therefore tend to lean towards refractors and SCT's for imaging tools.


It kind of surprises me because I personally really like them. I think, for want of a better word, it makes the stars look somewhat majestic. Not that I think images *without them look bad at all, just that I don't see diffraction spike as a bad thing.



But I also know that it's a technical aberration caused by spider vanes - it's not how stars really look in real life. The fact that I like them is probably caused by years of looking at David Malin's old photos from the AAT and other similar images. But then, any narrowband image is 'not how stars really look' either, so I guess I'm all about pretty pictures rather than accurate ones - I'm not conducting research here.



So is it just me that actually likes this optical aberration, these monstrous, image-ruining spikes? I'm aware plenty of people image with newts and RC's, but I'm trying to get an understanding of whether there is a general consensus that 'no diffraction spikes is better' or what the split is.


Markus
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Old 01-08-2022, 11:18 AM
RyanJones
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My humble opinion on the subject is as follows.
If they caused by part of the imaging system you are using then I think they very much have their place. They can be a great way to show how well aligned and focused and sharp your setup is. Because of that, artificial spikes wether added or edited are just adding lies to an image which I’m not into.

Cheers

Ryan
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Old 01-08-2022, 11:40 AM
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Stonius (Markus)
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Yes, true, adding diffraction spikes seems like a bridge too far for me too.
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Old 01-08-2022, 12:14 PM
AdamJL
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Agree with Ryan. I've no issues with them, I think they look great.
Unless the entire field is full of them, then they become distracting
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Old 01-08-2022, 12:48 PM
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The_bluester (Paul)
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I am largely in the "If it is an aspect of your image train" camp with diffraction spikes, though some can get a bit excessive when you see really bright diffraction spikes that extend across half the frame, or big noticeable spikes all over the frame. To use an image of my own, this one was pushing my personal limit of spikes getting to be excessive. https://www.astrobin.com/u6b7dg/

Artificially added spikes I am not really big on, it is rare to see ones that look "Natural". Let fracs be fracs and scopes with spider vanes be scopes with spider vanes. If you have a RASA, make your own choice on what the cabling does diffraction wise.
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Old 01-08-2022, 01:05 PM
Startrek (Martin)
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Yep from me, as I solely image and observe with Newts 6” , 8” , 10” and 12” and are a part of my Astro journey since I started
Capturing an image with no DF’s at all would feel a bit weird for me

Cheers
Martin
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Old 01-08-2022, 02:31 PM
AdamJL
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Quote:
Originally Posted by The_bluester View Post
I am largely in the "If it is an aspect of your image train" camp with diffraction spikes, though some can get a bit excessive when you see really bright diffraction spikes that extend across half the frame, or big noticeable spikes all over the frame. To use an image of my own, this one was pushing my personal limit of spikes getting to be excessive. https://www.astrobin.com/u6b7dg/

Artificially added spikes I am not really big on, it is rare to see ones that look "Natural". Let fracs be fracs and scopes with spider vanes be scopes with spider vanes. If you have a RASA, make your own choice on what the cabling does diffraction wise.
that's a stunning image!!
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Old 01-08-2022, 03:26 PM
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If they are good enough for JWST, then I'll stick with them on my newt !!

And +1 on the image! It looks like the alien out of'Alien'
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Old 01-08-2022, 07:17 PM
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Quote:
Originally Posted by ChrisV View Post
And +1 on the image! It looks like the alien out of'Alien'
Well I am never going to unsee that now! I always saw something vaguely undefined blasting out of the bottom left corner, trailing smoke.

And thanks, I have always been really happy with that image. I may return to the target next time around and try to mosaic it as there is stuff all around it.
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Old 03-08-2022, 11:05 AM
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Sorry. It's the first thing I saw. But I hadn't had my morning cup of tea yet ...
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Old 03-08-2022, 04:40 PM
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I think that the general populous are used to seeing images with the spikes, so come to expect them.

I have a filter that goes on the front of my refractor to fake the spikes. I've used it, but I am very undecided as to whether I like the look or not. Maybe I need to run 2 sets of images and see which one people go for...

Cheers,
V
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Old 04-08-2022, 06:28 AM
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Not having seen the effect that the filter produces it is hard to say, but perhaps I should amend what I said above. I don't mind the look of diffraction spikes in general, provided that they are there because of something in the optical train which actually causes diffraction to produce the spikes. Spikes added in post production by software usually look like spikes added in post production by software and I am not nearly so keen on that.

I have seen software that is pretty sophisticated about it, even adding the coloured "Stripes" in the spikes (Which I presume are slightly different diffraction effects depending on wavelength) that for a newt for instance indicate that it is pretty well collimated when you see them in an RGB image.
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Old 04-08-2022, 07:16 AM
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The filter is simply a 3D printed 'X' that slips over the objective lens. I got mine from ThingiVerse, and is very similar to this one: https://www.thingiverse.com/thing:4608036

The result of about 20 minutes of capturing the Southern Pleiades with the filter in place can be seen here: https://blog.teamrc17.net/Astro/saywhat/

The spikes are not overly large, and whilst I think they look OK, I don't think I'll be using that filter very much (if at all) in the future.

Cheers,
V
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Old 04-08-2022, 04:49 PM
GOTO (Geoff)
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To spike or not to spike?

So, I know I am on my own here but I always liked the spikes and after the JWST, I tried this
Geoff
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