How To Fix Your 8 Inch F3.9 Newtonian's Ugly Diffraction Spikes | Orion Skywatcher ES

In this video I show you how to fix your Explore Scientific, Bresser, Orion or Skywatcher 8 inch F3.9 newtonian telescope.
If you are experiencing bad diffraction spikes in your images I will be showing you how to completely fix this, as well as some hurdles I had to overcome to get it into collimation.
Link to the aperture reducer files.
drive.google.com/open?id=1xI4...
Shorter focuser extension tube for the N208CF
www.highpointscientific.com/e...
Amazon affiliate links below that help my channel.
Shorter focuser extension tube - amzn.to/31KVLMW
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Thank you
Clear Skies

[@un1xg33k]

Your "upside down secondary adjuster plate" tip saved me from almost certain mental and emotional decline, thank you. I was about ready to bust out the drill and void the warranty until I saw this. No matter what I did, the secondary was always just a few mm too low.

[@wcoastsands]

I think I might have the same issue. I've adjusted the secondary collimation screws to the point where the springs are completely compressed, but still can't quite get the secondary centered under the focus tube. Did you have to completely remove the secondary assembly to service this issue? Thanks

[@emuhead]

@@wcoastsands You can instead flip the spider vanes. One side is slightly angled, the other side is flat. Flip them around and voila!

[@EloynAmmillio]

Oh my god, thank you so much! I have this telescope and didn't even realize that there was an extension tube on the focuser. I'll print out your ring files as well!

[@budgetastrophotography1506]

Going to check mine thanks, also one thing that help mine was this. I darken the edges on the primary mirror to keep any loose light out.

[@charliemarchand]

Thank you for posting this! I recently purchased one of these scopes! And thank you for sharing!!

[@diedericho]

Thanks! That sec mirror offset was driving me crazy!

[@davitc]

Thanks for the tips, they saved my f/4 telescope. I just discovered that my Chinese scope has a spherical mirror, and has lot of spherical aberrations. I reduced the aperture from 203mm to 164mm, and the images get better.

[@emuhead]

So many great tips in the one video. Thanks!

[@JackieO74]

Thanks for this Matt!!! You have helped me resolve my same issue with my new Quattro :)

[@irfanrashid2114]

Great video and thanks for sharing your learnings. I have a 8 inch f/6 skywatcher flextube dobsonian and I am having the same star flaring problem. Might be the focuser causing this.

[@daltonortega]

Super helpful, even 2 years later. I was all but resigned to the fact that I would have to accept these additional (not spider vein) diffractions with this scope. I really think they've been throwing off my Bhatinov focusing as well. I'm going to switch to the 1" extension tube and see if that helps. Although, my RCC I is quite long and I hope it doesn't still protrude into the optical path. Only one way to find out !

[@billducas]

I have the Orion XT8 Plus. After using it for a few months, I took off the secondary mirror just to see if I could get it back into place and lined up. My job before I retired was aligning lasers with mirrors to read white blood cells, so I figured this would be a super easy task. It was. When I reinstalled it, I actually aligned the secondary mirror better than what it was from the factory. It was the front to back adjustment that was off. It didn't have any offset before, but it does now and the views are much better. I also did this with my 130 mm Meade Lightbridge Mini. The views improved on that telescope too. My Meade 114 mm Lightbridge Mini had the secondary mirror aligned perfectly from the factory.

[@royzview6254]

Aah…I get it, the focuser tube interferes with the light passing to the main mirror on one side. Now you point it out it seems so obvious. Also the perfectly circular collar on the primary mirror is a brilliant solution to a perfect image. Some great ideas I will put them to good used. Thumbs up.

[@winman14may]

great advice! i am having same issue with my skywatcher 8inch F5

[@alexyu6928]

Many years ago I came across a discussion on Cloudy Night that people were using curved secondary mirror spider veins to eliminate diffraction spikes. In fact, there was a company selling customs made curved replacement spider.

[@TheHeldere]

good video, very helpful, many thanks for sharing the files

[@rockymountainastro1239]

I just ordered the 10” Quattro and can’t wait to use it. I’ll absolutely use ALL of these tips to get the performance spot on. The skywatcher coma corrector is the one I’m buying. I’m super curious about those mirror clips. Thanks!

[@MattsAstrophotography]

Im sure you will love it!

[@VictorRoblesPhotography]

Thanks you for mentioning the off set in the secondary for colimation. It been driving me crazy. I did not know this is normar in my Meade 8” f/4. I was trying to do what everyone else were showing and was alway off.

[@MrSnivelupagus]

Thanks for the video. Orion now has a different F4 version. I went through the same thing with the F3.9 version collimation using a laser collimator. Once I got the laser perfectly coming back through itself, same offset picture for weeks until I returned it. I was trying to upgrade from the F4.9 Skyview Pro 8". I ended up taking 32mm off the back to get the drawtube out, and flocking with the Protostar flock board stuff. However Ken at Orion responded to my email with pictures of the issue, right after I already returned it. It's an actual known issue and it was actually collimated. He sent me an image from Harold Suiter "Star Testing Astronomical Telescopes", where he describes the effect. Maybe the new version has this issue noted. I returned mine before I ever tried to use it, cuz If it isn't collimated, I isn't using it. A little ink in the manual can save a lot of returns.

[@mauri740]

Thank you, Matt.

[@Dennis-tf2cs]

Great video and I appreciate the information.

[@ruthlessadmin]

This is my first scope. As a complete newb, I wonder how long it would have taken me to even know there was a problem....It still doesn't offend me...the sample images looked equally epic to me and so I'll def. be happy if I can achieve your worst result from the samples lol Thanks for sharing tho...will keep this in the back of my mind, once I get some experience, in case I'm still not happy with my photos.

[@TheSpacePlaceYT]

Diffraction spikes in stars actually make the image more beautiful than it would normally in my opinion.

[@Mike321795]

I agree diffraction spike look cool, but the distraction spikes he is talking about are not even more towards one side

[@TheSpacePlaceYT]

@@Mike321795 Ahhhhh

[@Imotbro]

This was a timely video as I am struggling with all the same issues. The biggest complaint I had was the alignment. No matter what I did I couldn't get it dead on. It was always just off center. Just before I viewed your excellent video I pulled my mirror out. I figured it was off center and was contributing to my alignment issues. It was right on. While I had the mirror out I noticed it was locked in tight. I pulled the mirror out re-glued the center plastic piece with epoxy on one side and silicone on the other. I threw the holding tabs away. I glued the mirror in with three quarter sized drops of silicone. That should hold the mirror securely in place and relieve the mirror of stress. All your tips where excellent. Thanks for doing a great video.

[@MattsAstrophotography]

Awesome I'm glad I could help.

[@KHoff77]

Nice tip on the gluing on wax paper.

[@MattsAstrophotography]

Your welcome it makes it much easier, the glue won't stick to it.

[@knightclan4]

Excellent video

[@strelnikoff7]

Excellent! I have this telescope for nearly two years - and haven't used it yet. I need bigger mount :) but once I did tried - mounted on 10Micron, and collimation was off. And I've read on cloudynights something about this fixing the diffraction spikes - never understood well what it was all about. I'm a bit hesitant to mess with secondary mirror - it all looks well collimated now... but I'll try. So 1" extension tube...

[@wcoastsands]

Hey hey! It's been a while. I just recently started using mine again. Trying to figure out how to resolve the issue with the secondary now. I pulled the primary earlier today to inspect the mirror, but also checked out the collimation screws because two of them weren't easy to use. Turns out the threads had rusted. The one that was in good shape had been greased at some point. The others appeared to be dry. I cleaned them up and put some SuperLube Silicone grease on the threads. Better off now, but still a little difficult to turn under tension. Might add PTFE washers next time.

[@strelnikoff7]

@@wcoastsands Hey! Just yesterday I have logged into cloudynights first time after… well, before this virus thing started going on. In fact, it’s been a long long time since I went out - and I did so last week. It was funny, trying to remember all the settings on a hand controller 😄 And mosquitos were vicious… managed some part of Heart Nebula… Can you believe I haven’t used my “new” scope yet? Planned to buy that EQ6R Pro - and didn’t yet. Well, I got my enthusiasm back so - re-start!

[@frank4one]

Thanks for the video. I have been tortured with similar ugly and asymmetric diffraction spikes. I suspected my spider, focuser tube and mirror clips. I just replaced my spider and I will try your idear for the mirror clips. I think I can solve the focus tube issue as I have and adjustable 2in. extension tube. I just need to work our extensions to minimise the intrusion into the tube. Hopefully all these will work as in your scope.

[@MattsAstrophotography]

Your welcome I'm glad I could help I hope it fixes your issues.

[@woody5109]

Excellent

[@johntrueblue]

this is very interesting, been googling and reading up, looking at purchasing the Orion 8" and now come to this video, makes me think other wise about buying this telescope now. By the way how do you clean your mirror, see so much dust and hairs sitting on it..?

[@boaty1968]

I have this issue on my skywatcher 200pds , so far I trimmed the tube and fitted a stop so tube can’t slip off drawtube rollers , had a aperture mask cut by cnc 1mm thick aluminium painted black stuck on with blutack , now currently fine tuning the baader mk3 cc as I need 57mm back focus so that leaves you 3mm short of required distance a friend has kindly made me a 3mm delrin washer to bring me to 58mm which is within tolerance and the better measurement apparently, masking the clips does make collimating secondary harder not seeing any clips though , I’m sure I will get there eventually.

[@davebloomsness8019]

I have a 10" Skywatcher Quatro with the same spiking issue. I found that it wasn't caused by the mirror clips, but the mirror had a slightly turned down edge, It's currently being refigured.

[@julianparks8485]

Thanks. Great information. Did you bring this to Explore Scientific's attention?

[@abhijitjuvekar]

Thanks, Great help.

[@kekkoukedarake110]

Thank you, Matt. Great Help! I also own ES N208/812 Newtonian with Carbon Fiber and experiencing exactly the same issues. I just ordered 1" extender to replace 2", which, otherwise, I never imagine causing such issues. I appreciate if you let me know which coma corrector you are using. I am using SkyWatcher's but not totally happy with. Thanks in advance.

[@ChucksAstrophotography]

Good video. I heard about this problem with Skywatcher Newts a long time, I'm surprised it's still happening and that they haven't fix it yet.

[@ChucksAstrophotography]

Oh, did you say it was an Explore Scientific? It happened on my friends 'Skywatcher Quattro 200 CF".

[@MattsAstrophotography]

@@ChucksAstrophotography Thank's Chuck mine is the ES Carbon version. The person I met this past weekend had the Orion version and he also had these spikes. The best way they could permanently fix this is to some how mount the mirrior without the clips.

[@TheSpacePlaceYT]

This isn't really a "problem" per se. It's more of something that comes along the style of the telescope. This isn't something you can really fix with a Newtonian without multiple modifications so if it is really THAT bad, just use something else. Refractors and Shmiht Cassegrains are options.

[@franciscojordan5727]

Friend, congratulations, excellent video, a question, I really appreciate your help, in the two images that show at the end, the position of the secondary mirror. which is the one indicated for a fast telescope F 3.9? Image 1 or Image 2? My secondary mirror is very oval and I can't center it, I appreciate your response. ?

[@ToanNguyen-cf9vk]

Thank you !

[@franciscojordan5727]

Friend, congratulations, excellent video, a question, I really appreciate your help, in the two images that show at the end, the position of the secondary mirror. which is the one indicated for a fast telescope F 3.9? Image 1 or Image 2? My secondary mirror is very oval and I can't center it, I appreciate your response. ? 🙌🙌🙏

[@tomstrum6259]

At 09:14 yout Upper spider Vane looks Offset compared to the Lower vane.....Coulld be a video perspective illusion but you might check.....Out of line Vanes usually causes more Diffraction spikes.....

[@blakenorman4822]

Ive got a 16" skywatcher dob, my 32mm, 25 mm, 13 mm eyepieces all give crystal clear views of jupiter, my 5 mm is always blurry. When you show the secondary being distinctly offset , im seeing the little gold donut in middle with a black circle around it and another crescent shaped black circle below the round black circle, is this what you're referring to as being offset? Is that what im trying to get it to look like? thanks for video

[@cosmoscarl4332]

They say that these astrograph Newtonians have over sized secondary mirrors which causes some loss in contrast but gives you a larger image circle with the fast f/3.9 primary mirror. That's why I say that blocking the edge of the primary and the clips with these printed rings does not increase contrast. Most likely the mirror was pinched. Thats why the 10" versions of the same focal ratio don't have this problem. Its a quality control issue at the factory. They just happened to have over tightened all the 8" mirrors.

[@andreguimaraes96]

Awesome vídeo. Helps a lot. Do you know where I can find a mask for my primary mirror? I have a SLT130 Celestron and I couldn’t find. Tks🖖🏼

[@gusgusthegreat]

Did you find that the diffraction spike was caused by the focuser tube intrusion post hoc after replacing your focuser? Or did you know that that was the problem ahead of time, inspiring you to replace your focuser? I just want to understand how you might troubleshoot a problem like this from first principles.

[@12zaf1]

What you see on your brightest stars are called diffraction spikes and they have nothing to do with the focuser. They are caused by the spyder support of the secondary mirror in your newtonian. All telescopes with spyders supporting the secondary have such spikes, including classical cassegrains, ritchey-cretiens, dall-kirkhams, etc. But not schmidt cass, nor maksutovs. The fact is that what it is being reproduced on the focal plane by a star is the fourier transform of the entrance pupil, which in this case is affected by both the secondary and spyder, but it is only the latter which creates the spikes you see on your images. By the way, they are clearly visible on bright stars even in your "after" images.

[@NBubba]

I have more trouble with football shapedstars. I’ve had a scope shop do my collimating, I’m pretty sure my spacing for coma corrector is right. Plus I only get out and use it once or twice a year lol. My focuser is stock but I seem to have even spikes. Is the EF that much of a difference? I can send you a pic I took and see if you can identify possible problems. If that’s ok..

[@matadorbeagles1120]

I have an aperture reducer ready to be installed, but haven't yet. Also, did you loosen your mirror clips? I have read that they are too tight from the factory.. Was your center spot in the dead center? Finally, can you provide specs for replacement focuser? I was looking to replace stock with a feather touch focuser. I too am having collimation issues with this scope and cannot get it to hold collimation.

[@dankahraman354]

I have another problem: diffraction spikes split on one axis but single in another plus stars are not round...I suspect the secondary mirror isn't centred on the focuser.

[@donaldkasper8346]

Focuser went in a half inch but so does the mirror. The mirror is not against the tube walls. 10 in mirror in 12 in tube, for example, for Orion XT10. That is one inch in.

[@georgalbrecht8029]

Hi Matt, I was wondering if you are still using your ES N208CF OTA. I have the (probably) older brother of yours , an ES PN210CF f/3.8 version. I was particular interested to know what collimation tools you using on yours? I have a hard time with getting perfect collimation. My secondary mirror seems to always end up off centered (up) towards the tubes wall. I have turned the spider around in all possible positions :(. I am looking forward to hearing from you. Thank you.

[@Suhaib955]

Very informative video. I want to share the pic of very strange diffraction spikes that I've not been able understand or remove. Could you please let me know how I can send you the pic?

[@weasele1]

WOW I never thought to look at the focus tube being in the light path. i have a home made 16" f7 i am thinking of a 8 Inch f4. from orion i would probably remove the clips lol if you could modify the secondary can you get the normal view. its a good thing i saw this vifdeo i would have beat myself up trying to get the proper normal view.i usually use my zwo asi 290 or 224 mc woith the all sky cam to get a look at the view from the focuser. i want a low cost setup for sdso work i would like to eventually get an asi 294 i think its 2" not woried about coma yet i am using a 290 not getting the full field . i was thinking williams optics 60mm ed a 400

[@franciscojordan5727]

Friend, congratulations, excellent video, a question, I really appreciate your help, in the two images that show at the end, the position of the secondary mirror. which is the one indicated for a fast telescope F 3.9 ? Image 1 or Image 2? My secondary mirror is very oval and I can't center it, I appreciate your response. ?🙌🙏

[@charlesburks3988]

I liked the idea. But didn't want to loose any actual size. I cut the part of the mirror clips off that over hang the mirror did some tinkering so mirror wont fall out no gluing. The views are by far (MUCH) better. Now just all mirror loved your ldea I just went to the next level. 10in 4.7 dob

[@Mike-lh4wn]

Just to clarify...I don't think the clips are 'causing' the flares. They are just causing gaps between the flares. The flaring itself must be coming from the mirror edge. I wondering if recoating my mirror will help. Or perhaps the primary is too far down such that the edges are showing up in the image when they shouldn't be? Don't know.

[@mantownmedia78]

Which coma corrector did you use with this? I have a Bresser N20839 - similar specs.

[@thomasbardenwerper9365]

Great video Matt, extremely helpful!! Thank you for taking the time to make and share it! I'm going to take a closer look at my Celestron C8-N, it never occurred to me that the focus tube and mirror clips could be causing diffraction spikes. 3D printer to the rescue! (Gotta love today's technology!) FWIW: I've already 3D printed multiple parts for my scope including an absolutely crucial DSLR camera stock focuser adapter for both 2" and 1.25" camera nose pieces so I can reach focus. Without an adapter, there's not enough back focus. Do you have your segmented clip-blocking ring posted on Thingiverse?

[@MattsAstrophotography]

Awesome I'm glad I could help, I do not currently have my design up on Thingiverse I will look into putting it up there. Thanks!

[@Mike321795]

I have the c8-n as well so was itthe focuser or the clips causing the spikes on yours?

[@thomasbardenwerper9365]

@@Mike321795 It was the focuser. Because of this I replaced the telescope with an RC8 - something designed for AP. I'll probably end up selling my C8-N.

[@gary122]

Other easy ways to to stick round blackened disks or half disks over your clips, just big enough to cover clip. Same with the focuser protruding. You just have to remove sharp or straight edges with soft round ones.will spread out the scattered light evenly so not to make strange diffraction spikes

[@donaldkasper8346]

Instead of 3 protrusions cutting out light for the full mirror diameter, you just reduced the entire mirror diameter with the ring. I would think rubber caps or tape around the clips would stop stray reflections, but since they are black it sounds like something else on the mirror margin is causing the stray light. Chipped outer perimeter of the mirror?

[@Codebyakshay]

whats the offset of the secondry mirror

[@chrisstrobel3439]

I hope more people find this video, will save a lot of fast Newts from the junk pile. If you have a Synta Newtonian (Orion/GSO/Skywatcher/etc.) you can buy a precision laser cut stop down ring for your 8” mirror from a couple places in Europe that attach with the 2 screws on each mirror clip. Myself I have a 10” f/5 Parks Newtonian with a Van Slyke focuser, and have no such issues, but I do have an Orion 8” f/3.9 that I bought a stop down mirror ring for. BTW I’ve also seen Takahashi E-180 images before with what looked like mirror clip diffraction 😳

[@rogergroom5735]

Chris any tip on where to buy these stop down rings you mention are available? I have tried searching around without luck. I'm in Australia but happy to buy from EU if I could find them available.

[@digitalstudio9946]

Hi, is this telescope good for visual?

[@specter13ca]

I have been in the process of trying to find where those patterns are coming from right now on my Quattro 200p. ill try making one out of cardboard. Thank you i never thought of the primary clips but it does explane the tri shaped shadows it casts. i thought a bit might be coming from the secondary mirror casting a shadow. thanks again.

[@MattsAstrophotography]

You are very welcome. I struggled aswell and wanted to put this out there, I hope it fixes your issue.

[@specter13ca]

@@MattsAstrophotography made my mask finally. i used a piece of left over flock board. and it works awesome i used Velcro so i can take it off easy if needed.I was able to poke in between clouds last night and the pictures were shadow free. Thanks again.

[@MattsAstrophotography]

You are very welcome I'm glad I could help.

[@TheSpacePlaceYT]

By the way, they are coming from the 4 small bars that hold the secondary mirror.

[@specter13ca]

the star spikes come from the spider veins, the shadows between the spikes are from the primary mirror clips.

[@kosmos921]

czy możesz mi podać wymiary twojego lustra wtórnego

[@Merkmanizu]

Hey Matt, what the focuser drawtube length did you select on your Moonlite? another question, are you noticing any flex on your carbon tube with your imaging train?

[@MattsAstrophotography]

I believe I ordered a 2 inch draw tube and the carbon tube is very sturdy so I haven't noticed and flex.

[@ryanhogg6556]

Matt would it be ok to gule the mirror down and remove the clips ? Would it cause any problems if the mirror is gule down ?

[@MattsAstrophotography]

The only risk is the glue not holding and the mirror falling out other than that its fine for the mirrior.

[@Mike-lh4wn]

Yep, I came across the same problem with my 3.9 orion. After heavily searching the internet, I made a similar mask. It took care of the flaring but made my stars look kind of funny...with 'lobes' or something. I then tried some black masking tape to mask just the edge of the mirror (since I figure there must be mirror edge imperfections that are flaring out). I've also heard people say to try using a sharpie marker on the edges, but I'm not that brave. I haven't been out to test it yet. But I will also check my focuser and secondary position. Otherwise, it is a really great telescope. I just wish it would work right.

[@BrokenPik]

Matt, how much to print and ship, southwestern Ont? i have the exact same problem... huge flares ..i can provide exact internal radius measurements..

[@MattsAstrophotography]

Shoot me a message to [e-mail] we can figure out how to get one made up for you.

[@BrokenPik]

@@MattsAstrophotography kool... ok.

[@cosmoscarl4332]

You don't add contrast by further blocking the primary mirror with those rings. If you took the primary out to install those black printed rings you probably releaved the tension on the mirror caused by them being too tight so thats what cleaned up your image. Try removing the ring and see if the problem returns. Make sure not to over tighten the clips.

[@robertfrost3388]

What sometimes happens it that the edge of the mirror has a chamfer on which causes the image to go haywire, I have done this fix myself and whilst i understand the clips can cause pinching, this wasn't the case for me.

[@savtheastroguy]

Hello, what I wanted to ask is do I need a coma corrector for a 200/1000 f5 newtonian telescope?

[@luiscalle]

Any scope from f3 to f6 must use coma corrector. There are a lot of models into the market but the best and most affordable one is the ES HR coma corrector

[@savtheastroguy]

@@luiscalle ok thanks

[@darrenwarne9005]

What coma corrector are you using?

[@MattsAstrophotography]

I'm using the Explore Scientific CC.

[@cosmoscarl4332]

The same thing can happen on any mirror.

[@cosmoscarl4332]

I disagree with these black rings. Mirror obstructions decrease contrast not increase it. Your mirror clips may have caused the extra diffraction spikes but not because of their obstruction of the primary mirror. They were probably too tight which is called a pinched mirror.

[@anavarrocoquimbo]

Pinched stars look totally different.

[@NGC7000]

Hell no for a Newtonian telescope. I was in my way to buy one.., after watching this video, it’s no way.

[@Mike321795]

Dude i had that too i couldnt figure out why lol

[@bullshitvendor]

Have you noticed that your vanes are crooked clockwise?

[@whmitchellduke75]

That is all wrong

[@michaelwheeler334]

Ummmmmmm 🧐 I think you hacked together somthing to explain basically nonsense! You’ve stacked tons of images on top of one another haha…

[@Dak3]

What threw me for an embarrassing amount of time was the back focus for my coma corrector was actually 75mm 🤦‍♂️