Cela fait des décennies que ça existe ! Personnellement j'utilisais ce genre de truc il y a plus de 40 ans ! Les aigrettes (spikes) sont diffusées sur toute l'image, donc on ne les voit presque plus, par contre, il n'y a pas de magie : c'est une obstruction supplémentaire : cela ajoute de la diffusion et supprime le contraste (à ne pas utiliser en mode planétaire, lunaire, solaire)... Vous pouvez trouver quelqu'un pour imprimer en 3D sur Thingiverse... L'intérêt autre qu'esthétique (pour ceux qui n'aiment pas les aigrettes) et de pouvoir empiler des images avec des orientations différentes sans avoir des aigrettes dans tous les sens, ce qui est quand même très intéressant lorsqu'on photographie le même objet sur plusieurs nuits (voire plusieurs semaines ou années!).
In other words, diffraction is happening at the edge of an obstruction and directs light perpendicularly to that edge. A curved spider vane and curved shapes will hence redirect (diffract) light all across the FoV and increase the halo around the stars rather than create well defined spikes.
@@ortizma13 The JWST has both spiders and the long arms that hold the camera away from the mirror.... that is why it has two sets of diffraction spikes... larger from the long arms and the shorter ones for the spider.
The mirror of your telescope modifies the path of the light such that the image at the focal plane is (essentially) a Fourier transform of the "image" at the front aperture. So anything placed in that aperture, like the spider, modifies the Fourier transform of the image formed at the focal plane. Multiplying in the Fourier domain is convolution in the image domain, so your image gets convolved with the Fourier transform of whatever your support structure looks like. The shape of the diffraction modifiers is chosen so they spread the diffraction artifact into a shape that's less noticeable. They modify the shape of the diffraction artifact; they apodize it. Wikipedia has a decent article with some examples for different shapes: en.wikipedia.org/wiki/Diffraction_spike#:~:text=Support%20vanes,-Comparison%20of%20diffraction&text=No%20matter%20how%20fine%20these,used%20to%20image%20the%20star.
Now this makes a lot of sense, thank you!! I'm having trouble imagining how to apply a Fourier transform to a shape (and a cross would be like some sort of flat function with a Dirac in the middle, so infinite frequencies... That that's why we get infinitely long star spikes that just dissipate as they go? I need to research this!)
@@CuivTheLazyGeek Higher dimensional FTs follow a lot of the same patterns the 1D one does. Yeah, the FT of a cross is sort of another cross with a spike in the middle, the details depending on the thickness of the arms. The round central obstruction will spread that spike out a bit. Since stars are basically impluses, an isolated star is basically a picture of the FT of your spider. The papers other commenters have linked to seem to try to derive shape of the diffraction devices analytically. I don't think it would be too hard today to set up a problem with a Fourier optics model and optimize the device shape for whatever result you wanted. I might give that a try. Happy face stars? If you want some light reading, Joseph Goodman's Introduction to Fourier Optics is the bible. It's not light, but these lecture notes are pretty amazing too. They derive Fourier optics, but also ray optics as far field approximations of the angular spectrum representation: ethz.ch/content/dam/ethz/special-interest/itet/photonics-dam/documents/lectures/EandM/AngularSpectrumRepresentation.pdf
This cunning contraption was immensely popular among newt keepers a couple of years ago, but, in the end, the crowd abandoned it due to its degenerative influence on the image quality. I would recommend flocking spider spikes instead. I did it to my F2.8 newt, and those virtually light-years-long spikes became quite tolerable.
Hi Cuiv! Great video, again. -- The Fraunhofer (far field) diffraction pattern can be approximated with great accuracy by the magnitude squared of the spacial, Fourier transform of the obstruction (for a given wavelength of light). I think you're already familiar with Fourier transforms, which is why I bring that up. In other words, for all practical purposes, the obstruction geometry and it's diffraction pattern are essentially Fourier transform pairs (although there is a magnitude squared involved). Flat, horizontal obstructions will produce vertical spikes, and flat, vertical obstructions will produce horizontal spikes. The Batman shaped things work by (a) constantly being curved (i.e. removing the flat geometry) and also (b) having a varying rate of spacial curvature, which spreads the diffraction (hopefully somewhat evenly) across spacial frequency.
In other words, diffraction is happening at the edge of an obstruction and directs light perpendicularly to that edge. A curved spider vane and curved shapes will hence redirect (diffract) light all across the FoV and increase the halo around the stars rather than create well defined spikes.
In layman's terms: Imagine your spikey star image is a balloon with tentacle-like extensions. This gizmo simply squishes the 'air' (i.e. the light) from the tentacles back into the main body of the balloon so the balloon is rounder but also a little wider in diameter because the light that was filling the tentacles is now just expanding the rest of the balloon. You therefore loose resolving power. Others have explained it more technically in the comments if you are into Fourier transforms and such but that's essentially what it boils down to.
I believe nasa had a project named new worlds mission that uses a star shade that uses a similar concept to reduce difracction during star ocultations. It would be great to achieve something similar for the secondary of a Schmidt cassegrain.
Cool! This is very timely. My 10" reflector is arriving this week. I'll custom order these so I have the option of removing the diffraction spikes. Thank you!
As this is just a mechanical means of altering the optical characteristics I am a bit surprised that no one has thought of this idea before, particularly the telescope manufacturers, who could have incorporated it into their secondary mirror spider designs. I don't use my Newtonian very much, and I am in fact considering selling it so I doubt I'll be buying these devices. To be honest I don't mind the diffraction spikes, though if I was imaging with a Newt all the time I probably would like the option to remove them for targets where they may be a bit overpowering. Finally Cuiv, I think the Frankenscope looks really awesome.
Thanks for the details! I know Vixen has some of their small visual scopes with curved spiders to avoid star spikes... But would be fun to have manufacturers providing these as an option
You can also get rid of the star spikes by using curved spider struts. You want the strut tangents to uniformly span a full 360deg angle range. It will still diffract, but the diffraction will not be concentrated in specific directions.
So glad you decide to try these out. I got one for my Kasai Trading Ginji 200/4 Newt, and another for my VMC260L, but have yet to try out imaging with them.
Idk if you ask me the refraction spikes add very nice colors to blue and orange stars. If I started astrophotography from scratch I would take the reflector route because I love how those spikes look on bright stars as they also add very nice blue and orange colors.
I personally love the star spikes. And in my terrestrial photography, I love the sun-stars, and lightbulb-stars at night photography. My favorite is 10 spikes, but I only have one lens with ten aperture blades, fortunately not rounded blades. (I even like ten sided bokeh balls.) I’ve been doing some ultra-wide Astro-imaging lately with camera lenses, and the star spikes help differentiate the stars from the globular clusters and any small fuzzy nebulae.
Interesting video and product! I'm literally just getting my new CYCK spider out of the box to fit it and I see this 😭 To be honest I would prefer perfect (if enhanced) spikes than this effect, the stars will be more compact overall. I think!
The reason why the bat spider vanes work is because they create interference pattern waves that cancel out each other. Think of a pool and a wave generated on one end. If you create another wave that is opposite of it in the reverse direction, you can cancel the original wave out. The interference modeling to figure that out is even more interesting than the result.
Yeah I don't know if it's a sign of me being very early in my astrophotography or showing my age but I rather enjoy the diffraction spikes, like you said it reminds me of the hubble photos I grew up with.
A physicist's point of view: The idea of apodization is so old that it was mentioned in the original "Amateur Telescope Making, Vol. II" by Albert Ingalls in 1937. If you check out his figure, the things even look similar. Also, the famous optician André Couder wrote about this kind of thing at the beginning of the 20th century. All that these things do is introduce more diffraction. Because of their irregular shape, the diffraction pattern is no longer all that nice and regular, but the energy is distributed throughout the image. In other words: these little masks will take out more energy from the central maximum of each star, distribute them around its edges, and also contribute ever so slightly to a brighter background. As you can clearly see in your first light image at 8:58, you get frilly edges on your stars instead of the spider vane cross pattern, but the fourfold-symmetry of the spider is still there because you have introduced four identical little baffles.
BTW you missed one potential benefit. If you are imaging with a Newt/DK/RC/etc and you don't have a permanent set-up, it's virtually impossible to get the diffraction spikes to line up over more than one session. The apodizer should allow you to combine imaging runs over several nights with a Newt.
You make a very key point. And that is why I don't use a Newtonian for imaging since my image data often are taken over several nights... even years, locations, different scopes, and setups. I could never understand why people will add fishing line, etc. to a SCT to create diffraction spikes! I use either refractors or SCTs to AVOID those diffraction spikes. Perhaps people think that having those diffraction spikes makes their images like the professional big observatories that use giant reflectors and do have those spikes ;-) There are other ways to eliminate those spikes on reflectors.... curved vanes is one way. I also use Hyperstar setups and if you run the camera cables from the camera and an angle down to a point where they can exit near the corrector through the dew shield you can also mostly eliminate the spikes. If you run them horizontally on a Hyperstar setup out the side near the forward edge of the dew shield you will get the spikes.
what? I regularly shoot over multiple nights (while reassembling the whole rig), and never had this problem. Spikes will be aligned, just like everything else, during stacking.
"it's virtually impossible to get the diffraction spikes to line up over more than one session" Sure it's possible and done a million of times. Plate solve to find previous imaging angle and adjust camera current angle to match. Friggen MAGIC!
No, actually the diffraction spike angle doesn't change between nights, at least after star alignment - it will only change if you physically rotate the tube and thus the spider - only the orientation of the spider wrt the stars is important, the orientation of the camera won't be an issue!
My solution to the diffraction from the spider vanes has been to 3D print a curved vane spider. Like these apodizers, it's almost magical how well it works. In both cases, the overall diffraction increases, but it is distributed across the image and reduces the contrast just a little bit. Maybe not quite a refractor, but getting close.
I experimented with it on several Newtonian telescopes, but the biggest issue is that something like Batman appears in the ghost of the huge stars. While it is possible to try this with M42 or IC434, the correction is challenging. However, if there are no nearby stars like Alnitak, excellent results can be obtained using BXT.
I wonder if someone makes curved spider veins to completely remove all diffractions? Either way thats a cool effect! And I wouldn't worry about bats, I would be more worried about robins showing up 😛
I did some research on these things a while back. Basically that shape is a dissected circle and what it does is to scatter the light that would normally get concentrated into diffraction spikes. I thought about using them but I would have to print them myself since I use the smaller Skywatcher 130p-ds and nobody seems to make them to fit small scopes like that. Honestly though, if it makes my stars look weird, I would rather have the clean spikes
Hi Cuiv, Jaime from Chile again. If you going to 3d printing your own apodizing devices, make sure to scale acording to your telescope . The total length should be according to the following simple formula: Main mirror diameter minus secondary mirror diameter divided by 2. Then at the moment of placing on the spider, make sure you consider to fit the Device starting from the edge of the secondary mirror to eliminate the spikes because they are placed right on the light path of the telescope. Hope this information will help you. Greetings from BelloCielo - Chile 🇨🇱
They need to use 2 arcs to hold the secondary. We use one arch with our hyperstars to remove the single diffraction spike cause by cables. By routing the cables in an arch it removes the spike.
I thought they would help eliminate the spikes, but not work as well as they did. Remember that some spiders used curved veins to (or try to) eliminate the spikes, therefore they're due to the veins being straight and across the FOV. "Jingle bells, Batman smells, Robin laid an egg, The Batmobile lost a wheel, the Joker got away, hey" Geek On, Cuiv!
Ah Batman to the rescue lol, it kinda reminds me of being at a star party & a guy with a 20" Dob & the bat sign tried making the bat lamp on a cloudy night, it didn't work but it was funny all the same. I have seen curved spider vanes used to get rid of diffraction spikes maybe someone on Ali Express could make some he he. Clear skies
Decades ago, I saw a picture of a scope made in Russia that had spider veins that were shaped like half circles. Someone claimed that they still produced diffraction but the curved shape allowed the pattern to be essentially spread out and "cancelled". I don't know if the word "cancelled" is the right word, but they seemed to work. I suspect that regardless of patent issues, the curved veins may be mechanically problematic especially in larger scopes. I'm going to have to take a look at this Japanese company's web site.
I'm not really a telescope aficionado... but I do understand what's going on... (The comment from @ceoyoyo includes an excellent explanation.) (The little bats are effectively cancelling out some of the error created by the spider.) As for your closing question.... Assuming that those were designed specifically for that telescope and original spider... I would expect them to work best with those. The different spider will alter some of the optical properties that they are correcting. (But I have no idea how significant a particular change would be to the result.)
I did look a dual reflector setup but am currently setting up a refractor setup instead. The thing with fast reflectors is the collimation and posible mirror shift moving the alignment of both scopes fov. Im to Lazy to deal with that😂 With the refractors i will have fixed optics
In more mathematical terms, it redistributes the point spread function's intensity. I prefer to just use BlurXterminator post processing to do this mathematical function digitally, rather than physically increasing the obstruction and losing some information.
Thanks for the clarification about how this works! @boetschge: this video is just a test, unlike many other in depth videos about say, noise and astrophotography.
@@CuivTheLazyGeek You are doing a great job! The more your channel grows, the higher are expectations, of course :-) Just keep on doing your Thing, we love you!
Newtonian spikes can be very distracting on any target with bright stars around. Pleiades can be just too much, so is Alnitak with the Horsehead nebula.
@@CuivTheLazyGeek They Look Incredible,lol..But I Dont Use It All The Time,Just When Wanting The Brighter Stars Standing Out..Ive Got Clear Skies For The 1st Time In 4 Months😂🤣😂I Dont Know What To Do,lol..Besides Catch The Borealis,lol….
These bats should have been marked closer to the diagonal mirror, perhaps at Newton 200 mm they should be printed larger in linear size, and the effect is similar to a radius spider, when light waves are reflected and cancel each other out due to the interference effect, a local calm with small ripples is created, which the main mirror no longer sees
@@CuivTheLazyGeek In more detail and "scientifically" you can find out here about the calculation of the shape of the spider and its influence on the final shape of the stars www.telescope-optics.net/spider.htm
Has anyone replaced the open end of a Newt with an Optically neutral piece of glass with the Secondary Mirror suspended in the middle ? This would resemble an SCT of course but without the Optical “curve” . It would help to keep the Primary Mirror clean as well . Just a Newb question ./srk
Removing spikes is considered as crime to humanity. The best spikes that I ever got were with the "amazing" spider of my Skywatcher 150PDS and my DSLM having Alnitak on the exposures. The spikes in fact went through the full image. I love diffraction spikes!
@@CuivTheLazyGeek Star Spike Police is on it's way to Tokyo. 😄If you are nice and remove those evil things and they are able to confiscate then they are going to be pleased and won't arrest you. 😁
BTW it's "apodizer", not "apotizer". The original paper is "Apodization of the flat mirror support of a Newton telescope" by Temich et al. I think the StarWorks site is using automatic translation.
Also "apo" just means "far away". I presume apochromats are named so to emphasise they have even less colour than achromats. So, to me "apoodizer" just means they are removing the aberation, in this case the diffraction spikes. Doesn't really mean "it's like a refractor" to me.
@@CuivTheLazyGeek didn’t know that. I will seek the Aussies wit and wisdom on the subject. But I agree. The remind me of NASA photos and thus seem almost…. Important.
Great video again, brilliant actually. I must have missed it but where can I purchase a new one piece spider for my 200mm Meade? I just cannot collimated that thing, I’m desperate. Bought it from “All-Star Telescope” and it showed up damaged, their answer is to ghost me, lol.
I have tried this, but the artifacts become very visible (and in my opinion a bit ugly). If you take longer subs they look even more strange and after stacking it sometimes looks awful. Though, you might want to use two of the four to have thinner spikes (since they will not overlap anymore). Also, during my tests, those things totally confused starexterminator that probably never had seen such strange stars before...
I prefer my bat "appetizers" wrapped in bacon 🥓. Ha! But seriously, this sort-of solves your problem of needing to synchronize the spider vanes on your "double-barrel cuiv-scope".
Nah! It's a gimmick... On with the video. OK sorta... I think it mushes out the sharpness. There's no free lunch. And I'm biased anyway... I like spikes. Reminds me of Christmas! 😉👍
I use a refactor and I personally do not care for the star spikes from Newtonians, but it is the signature of a Newtonian scope. I do prefer the normal Newtonian spikes over the small stars with 4 stub spikes this device generated. Have you looked curved spiders?
I’m guessing this is like a curved spider, which removes the spikes but “moves” the diffraction into a “blob” on the star, making the star less sharp. I’d rather have the spikes
Hey Cuiv nice video as usual, I'm considering the apertura carbon star 150 but I'd like to know if it has major issues or after a quick collimation is ready to go. What are your thoughts on that scope? Thanks 😊
This kind of makes me wonder what kind of effect you would get if you had a spider that rotated slightly after every image, but you were able to keep the secondary mirror still.. I assume the diffraction spikes would cancel out in stacking?
@@CuivTheLazyGeek Yea, that's what I was thinking, kind of like satellite trails. But of course the problem would be trying to implement something like this without vibration, or the secondary mirror moving, but I'm sure there are probably some people a lot smarter than me could find a way to do it with some gears and a belt.
Have you seen a RASA? The camera is mounted on front. Power and data cables coming off it cause diffraction spikes. Some people orient them at 90 degrees.
The images are already manipulated in many ways. The regular spikes are not real and neither is the noise, the brightness, the apparant size of stars, or the 2D representation of a 3D object. Even our eyes manipulate images, as can be seen by optical ilusions. Scientific observations are done all the time with corrective optics where the mirror is physical bend into a differnt shape. I believe it is all up to the photographer how the image is captured, as long as it is not misleading.
i despise diffraction spikes. they are NOT naturally occurring, they are added artifacts to photos. yet people get so ANGRY about added artifacts to astro photos but gloss over these like they are 'cool'. well just go add some other lines dots and whatever you want then too since apparently it doesnt matter. the excuse that hubble had them is a bad one. i wont ever buy a newt for this very reason. because i dont have too. they HAD to with the hubble to get it feasible. it wasnt because they thought it was 'pretty'. its a negative aspect to the design. its called a flaw, not bonus material.
I don't understand all the love for diffraction spikes here. They are literally destroying data behind them. I would get rid of them in a heart beat if I can afford a 12" $500k commercial refractor. I just don't know if I like the weird stars you got with this addon.
That thing is rubbish, IMO. Everything in the optical path contributes with its Fourier Transform shape to the final image. So adding things cannot improve, just change the shape (ie where photons end up landing) . The only way to get rid of diffraction patterns is having bigger pixels (so the pattern is binned in a pixel) and lower F/ (smaller Airy disk). Newton telescopes' users should just enjoy their spikes and put the money in sth else
