Why Do Stars Have Spikes?

This video demonstrates where star spikes come from in the Hubble and Webb space telescopes. I show how to add them if you like them, or remove them if you don't.
#stars #Hubble #jwst #telescope #astronomy #diffraction
3D Printable Diffraction Spike Mask by fdoffin: www.thingiverse.com/thing:1260926
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Questions Answered:
1) What causes stars to have spikes?
2) What are diffraction spikes?
3) Can we eliminate diffraction spikes?
#dobsonian #aigrettes
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#reflector
#reflactor
@reflactor

[@hinesification]

Well explained. I’m a professional astronomer working on both Hubble and Webb. Great and simple to understand video. We also routinely use diffraction spikes to align dithered images for coaddition.

[@reflactor]

Holy cow! Thank you for commenting - I am honored that you watched this video! I had a lot of fun experimenting with these diffraction spikes.

[@factChecker01]

Very interesting! One thing I like about the diffraction spikes is that you can tell which are stars and which are galaxies.

[@reflactor]

Yes. They do come in handy in several circumstances like that.

[@dff19707]

I’ve never heard of these batwings, and, truthfully, I’ve never seen a discussion about diffraction spikes. So, this was a fascinating video on how to cause and diminish diffraction spikes. I don’t see me trying batwings, though, because I like diffraction spikes. That said, I still think of Pluto as a planet, so YMMV.

[@reflactor]

Thanks for watching - this was a fun experiment. There are 3D printable masks made for specific refractors whose sole purpose is to add diffraction spikes. I guess people just expect to see them! Personally, I prefer the diffraction spikes too!

[@JoeJaguar]

Thanks, John for the video. I never really minded. Spikes but I guess it’s very individual like anything else. Cheers.

[@FelipeCardimF]

Amazing content as always! Cheers from Brazil!

[@reflactor]

Wow, all the way from Brazil! Thank you for watching!

[@niteman555]

the direction of the spikes is counterintuitive at first thought, but a vertical support would only give a vertical spike if the spikes were negative space rather than "extra" light. Once you consider that the horizontal spike from a vertical support is the smeared light as it bends back towards the center, and that each star is effectively a point source, then it makes sense that spikes are orthogonal to the supports.

[@reflactor]

Thanks for watching and, yes, the whole diffraction issue seems to be at odds at first with intuition, but it makes sense in the long run.

[@BA-cn3rk]

All your videos are so helpful !! I did know about diffraction spikes, since I use both reflectors and refractors, but I didn't know that the curved holders prevented them. (I like learning something everyday) I like the spikes in my images, it adds beauty to the stars. I use a Bahtinov mask for focusing, but I've found that just using the diffraction spikes for focusing does just as well. Get them as thin as possible. Keep up the good work.

[@reflactor]

I'm glad you found it interesting. Thank you for watching!

[@curronhill2744]

Very interesting, i prefer to not have them in my astro photos, but like them on the star atop our Christmas tree!

[@reflactor]

Yes, they look good in some photos for sure. :)

[@hednik]

Something I never knew before! Thanks!

[@tommes9537]

great video. I learned a lot. Thanks

[@reflactor]

Thank YOU for watching. Clear skies!

[@BobGeogeo]

I believe diffraction spikes have been used in research as a way to find the center of the image of a bright star.

[@reflactor]

That's pretty fascinating. Thank you for sharing!

[@SonoranAstro]

hahaha i’m guilty of using guitar wire on my 70-200 lens to get diffraction spikes 😂 i love the look of them

[@reflactor]

Now that's an interesting way to generate them!

[@Acc-kb9mf]

I have always wondered what the visible contribution of the support obstructions is. Very cool to finally know

[@reflactor]

This was a really fun subject to dive into. Thank you for watching!

[@Slartyfartblarst]

Educational.

[@reflactor]

Thank you for watching. Clear skies!

[@k.h.1587]

Some people actually put a cross of string in front of their refractor lens or sct/mak corrector plate for spikes in their images

[@AmatureAstronomer]

I have diffraction spikes when using my reflectors, but not when using my refractors. Oh, like he said.

[@reflactor]

Same here. In the video, I show how you can add diffraction spikes back into your refractor images (using pizza box cardboard).

[@eparhas9162]

Ive always considered it best to go with whats natural for the scope. Adding them to refractors or removing them from reflectors seems equally silly to me

[@reflactor]

It was eye opening for me. On Thingiverse, there are special masks made for specific refractors just to add in diffraction spikes. Everybody has their preference. :) I personally like the spikes.

[@tubedude54]

Very interesting. I did learn something I didn't know, which is now so obvious once you mentioned it, and that was that the Webb has 8 spikes and not the 6 I figured it did. Also, how much light is blocked by the 'bat' wings?

[@reflactor]

It's kindof a neat bit of trivia because the horizontal diffraction spikes are on the short side. I didn't notice any reduction in light from the batwings.

[@tubedude54]

@@reflactor Well, we both know they have an impact just like the secondary does in blocking light... I'll leave it to you to calculate their area though as that's a 'few' years past my last calculus class! lol

[@robertsonsid]

That GSKYER star image isn't that great. I wonder if the collimation (hard to adjust in that unit) is off. I have a used Meade 90mm that gave awful images until I discovered the previous owner had the objective flipped over. Excellent video!

[@reflactor]

You are correct. Aside from the primary lens, the Gskyer is pretty nice. The tripod is good. Vixen mount. Fantastic rack & pinion (no slop!). And yet, the primary lens is not good. Just.... barely acceptable. Thanks for watching! (I'll have to see if the previous owner took it apart and flipped it!)

[@dumpydalekobservatory]

Ah diffraction spikes the Marmite of astronomy you either love them or hate them, I must be weird as I hate them whereas my other half loves them. I've seen Newtonians with curved & weird shaped spider vanes to try & stop them to.

[@reflactor]

You either love them or hate them. :) Thank you for watching.

[@leppad]

Why couldn’t you mount your secondary mirror without obstructions by integrating the secondary mirror with a thin glass transparent disc the same diameter as the telescope tube. You could still add pivot screws to the larger clear glass disc in order to adjust the secondary mirror. That way you wouldn’t have opaque mounting posts.

[@reflactor]

Your suggestion is a good one. It's been done on a few occasions for Newtonian reflectors. It has the added advantage of keeping dust out. Although that also eliminates the support strut issues, it has two primary downsides. The first is that it's another glass surface that has to be impeccably cleaned. The other downside is that it makes it very tricky to align (collimate) that secondary mirror because you often have to "grab it and twist it" just a bit. With the glass there, that becomes impossible. The use of a glass support is also part of Schmidt-Cassegrain and Maksutov Cassegrain telescopes, but their glass disks aren't simple see-through flat glass. They have a varied thickness and curvature that pre-corrects the light coming in so that when it bounces off of the spherical mirror, it will be aligned properly.

[@leppad]

@@reflactor Well it was just an idea I had. I know very little about telescope hardware. So, you explained why stars have spikes. But why don't galaxies and planets also have spikes? All they not all light sources so far away that their light rays are parallel?

[@reflactor]

I suspect it has to do with light intensity. Stars are bright singular points of light. Other objects are much dimmer and diffuse (spread out).

[@johngiromini5745]

Those batwings are pretty neat; hadn't seen them before. I worked on the SmartSense Explorer DX 130AZ this afternoon. And now a word from our sponsor: NoSweat Spritzer. It's a spray application and totally seals the skin pores to prevent the expulsion of sweat. Of course, the body swells up but hey, everyone needs a way to be funny. Now back to our regular program. I worked on getting the 130AZ "aligned" better by just using a cap hole. And while the image is in focusa, I'm not sure it improved. Fixed the red dot finder scope. Put the 25mm lens in and it looked great; nice sharp image. Packed it up and sent it back to the client. Will need to establish a time to actually view something at night preferably in December.

[@reflactor]

Congrats on getting it all fixed up. It's always a challenge when the bolts won't come loose, lol. Hopefully there were no broken bolts involved!

[@glhmedic]

Are still playing on a video dealing with power seeker 127 scope?

[@reflactor]

I am. I have a big pipeline of videos lined up. :)

[@AmatureAstronomer]

@@reflactor I have been thinking of buying a "power seeker 127", proportly the worst telescope in the world. Sounds lie a challenge to use for celestial photography.

[@glhmedic]

@@reflactor ok sorry to bother you.

[@k.h.1587]

The batwings add a bunch of sloppy diffraction close to the star making it more blobby. I would rather have the spikes

[@reflactor]

I do prefer seeing the diffraction spikes.

[@k.h.1587]

@reflactor I didnt have a review sample/prototype of a premium reflector offered by Anttlers optics for a while back around 2005,, a GSO 8"f5 with refigured primary, smaller Antares secondary, curved vanes and flocking above the mirror and opposite of the focuser, and it was really like looking through a big refractor. There is still diffraction but you can't see it. It was an amazing experience for the month or 2 I had it, and when I had to send it on to the next guy, it was missed. Me and Scott (anntler) had become friends online through yahoo astronomy groups/clubs and talked on the phone often, and I bought my 10" dob from antlers optics. Same thing a few years later after being at opt for a while, when the skywatcher 120ED first came out and they had me take it home for a while to put it through its paces. I hated the day they asked me to bring it back