How to Collimate your SCT | EdgeHD 8 Collimation
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- Опубліковано 10 бер 2022
- In this video I go over the steps I take to collimate my EdgeHD 8 SCT. There is an easy system to follow so that you always know when you are making a correct adjustment or an incorrect adjustment to the secondary plate of your SCT. Hopefully it will assist in speeding up or making your collimation easier.
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#astrophotography - Розваги
Joe, good explanation but I've found much better results with two things: 1 - Using much smaller adjustments (I can see you tightening loosening by 1/4 or more turns at a time), and 2 - Always doing a three process adjustment, ie. when I tighten one I ALWAYs loosen the other two or vice versa.
Usually only takes about 2-3 minutes once a year or so.
just my 2cents
Ah, the joys of collimation! Very good explanation Joe. I'll be bringing out my C8 soon so the refresher is very welcome. Thanks!
Thanks so much dali! Just in time for galaxy season.
Awesome video Joe and perfect timing, thank you very much for this 👍
Thanks Russell! I’m excited for you to get yours operating, they are very nice scopes. Let me know how it goes.
Great video Joe, very well explained !
Thanks Siegfried, glad you liked it!
Excellent tutorial Joe. I wasn't aware of the part about the whole star moving as you change collimation as the clue whether it was correcting the right way. Will definitely keep that in mind next time I have to collimate my Meade SCT
Thanks Logan, I’m glad you found it useful! I’m going to try one of those masks as well others have mentioned.
5:36 that image is important, and something no one else discusses in their tutorials. I'm commenting for, if nothing else, so I can find it when I forget again, because the Celestron EdgeHD 8" holds collimation for a long time (even with Bob's Knobs.)
Thanks Joe, been learning how to use the Hotech Laser Collimator today on my new EDGE 8, I will need to do this though to check I’ve got it right. Your EDGE HD tutorials are so great for me at the moment and much appreciated… thank you so much for doing all this ⭐️⭐️⭐️⭐️⭐️
Thanks so much Olly, much appreciated!
@@JoesAstrophoto Hi Joe… Do you always collimate the EDGE HD with the image train you plan to use, ie with the Reducer on❓I’ve been told I should always collimate with the Reducer off but this seems like a time-consuming thing if planning to use the Reducer.
Hi Olly, I’ve always collimated in the configuration I’m going to use it in and have never had any issues. The only thing that I’ve noticed is that I have to collimate out of focus “out” and not out of focus “in” when doing the out of focus star method. Hope that helps.
Thanks for this Joe. The tip on going inwards to get a doughnut rather than out is something new so I’ll be giving it a try. I’m always struggling to get perfect collimation.
Thanks John, glad it was helpful!
Great as always Joe 😀
Thanks so much, I hope it helps people out!
Another great upload, Joe! That CEM120 is purring like a kitten now! Hope you're getting on well with it...I LOVE my CEM70! Have a great weekend and keep up the excellent work! :)
Thanks OJ! I’m really liking my CEM120 right now, guiding is almost always in the .3s and .4s with good seeing and .5s and .6s in bad. I really can’t ask for or need much else.
Your video is very helpful. A week ago I went through the same nightmare as you when collimating my Meade 10" SC. My OTA has an additional problem because it is very old (from 1999) and suffers from mirror flop and focus shift. To minimize the effect, I installed a mirror lock system that improves the problem a lot. Likewise, when I focus, I always make the last movement in the same direction. Even in modern SC with Mirror lock system, there is always a small oscillation of the mirror that generates some decollimation. Hugs😊
Thanks so much Jesus! It can be a pain sometimes, but then it goes much faster when I'm not making a video at the same time. It took me about 20 minutes total that time, but when I'm just doing it and not thinking about explaining it, it takes me 5 - 10 minutes. Still hate it every time though, not sure why but it's always the coldest it's been in weeks the night I have to collimate lol.
you can get rid of mirror flop by using a crayford. get close enough with the mirror, then lock it and use the crayford:)
Nice tips.
Thanks Joe!
Thanks for watching Cap!
hi nice video thanks. there are these two mirror flop knobs. it is loose now for me. i want to use with EAF.
when shd i tighten the mirror flop knobs? or do i always leave it loose? kindly advise.
Great informative video Joe! I don't have to worry about all that yet! but it will happen one day!!
I might go mono though, so seeing how to put filters in backwards might be usefull!!! Lol
Hahaha thanks Simon, you're gonna love mono!
Very well covered Joe. I think no matter how good your collimation tools are you cannot beat the final collimation tweaks on an actual star
Thanks Glenn, at the moment that’s the only collimating tool I have lol
Great tutorial Joe. You can certainly see why it is SOOO important to keep the target star in the center of the view. I am also discovering why collimation is important when using an OAG, along with the correct back-focus. (BTW, I just received the OCAL electronic collimator and am ready to start playing with it)
Thanks Pat! I’m looking forward to seeing your video on it if you make one.
Wow that’s a lot to learn how use your equipment
Hi Astro, there is so much to learn, but I think that’s one of the things that keeps the hobby interesting to me. plus I couldn’t afford to get 2032mm of focal length in a refractor scope.
@@JoesAstrophoto
Definitely is fun to be challenged with all that equipment.
I always wanted a good refractor as well and for the same reason I never got one was the money.
But to get closer to what refractor can do I had to get 15” Obsessions it really does good job on planet for viewing but Astrophotography is no way to much to move on .
I just used astrovid planet cam for video
Second option I have is 9.25 celestron that bothers me with not having sharp view than makes me be more in love with refractor telescope .
I’m not good with photo processing any way so I choose to stay simple .
Very nice video thanks
Thanks so much Rashmi, I appreciate it!
Good vlog. I have a C6, a C8 and a C9.25. All have Bob's knobs::))
Thanks astrodad!
Very nice. Looks like quite a process if you set up every time though.
Thanks Nick! You know it can be at first for sure, but I think after doing it a few times you get much faster at it. Normally I can collimate the scope in about 5 - 10 minutes, but I remember the first time I did it, it took me almost an hour. I'm super lucky to have it mounted in a permanent state for the most part and it seems to hold collimation very well.
Excellent and easy to follow guide on how to collimate. I've yet to have the skies cooperate long enough to actually get out there. I tried last night, but pretty much as soon as I got setup and defocused on a star the clouds rolled in.
I'm a bit confused regarding the screw to thick side relationship. If there's no screw on the thick side, you then choose the screw completely opposite the thick side of the donut? Also, to make sure I understood the "right" vs "wrong"... once I've made my adjustment, I want the star to have moved _towards_ the thick side of the donut, right?
Thanks Jonny, I hope it helps people have an easier time of it. Also, that’s exactly correct on both counts. I needed a much taller tripod for my camera so couldn’t get the screws on camera, but I hope people get the idea.
Nickel 👌 tes vidéos France 🇫🇷…!!
Thanks Chris!
Thanks for the video! Loved it! One question though, even though the star in the center looked like you had collimation, the star in the upper left definitely did not. That’s the kind of thing I see on my edgehd as well. Is that a sign of a back focus issue?
Thanks Mike! It could be, but honestly they always look like that to me and is more pronounced with the larger sensor of the 2600. From the last year of owning this particular SCT as long as I get the star in the center to very close, then the rest of the stars across the field look good after focusing.
I collimate with a fake star "flashlight", Works really well if Im about 30 to 40 feet distance. Always do it in the daytime.... so much easier
Interesting method, thanks for sharing!
Hey Joe,
Nice video.
Do you think the pinched stars at the edges are because the backfocus is off when the focus is so far off?
I use a Moonlite CHL2.5 focuser, and to get that far out of focus, it probably moves the camera sensor 4-5 mm from the focal plane. I'm guessing this is what you'd see if the backfocus was off by that much.
The stars in the corners look fine when in focus (from what I can tell on the video anyway).
It makes me think that this may be a good way to determine the proper backfocus distance (which can vary a bit from scope to scope). By moving the focuser position until the stars are round across the image (though out of focus), you could then see how much the camera sensor needs to move to be at the proper backfocus distance?
Not sure if I'm explaining clearly or not
I might give that a try next clear night.
Cheers,
Jason
I only think of this because so many people question about proper backfocus on these EdgeHD units. It would be nice to have a quick method for this rather than to setup the camera with spacers, take an image, see if the spacing is right, add another spacer, image again, and so on...
Add... I'll have to think on how this would work. Not as straight forward as I thought.
Thanks Jason, I'm not sure if it is back focus or because of the shape of the primary mirror. Going off of what Celestron recommends, you can only get a true collimation when collimating on a star in the center of the field. This makes me think that's it the shape of the mirror as it moves outwards that causes the stars to look that way, but I'm not 100% sure about this and it could be a back focus issue. The main thing I go by is that when at a very good focus, all the stars across the field are round. That's what I'm getting now, so I have to assume it based on the mirror shape. The 2600's larger sensor makes it appear even more dramatic than the 294 did. I'm assuming because it's able to capture that much further out along the outside of the mirror?
Aren't Bobs Knobs/Collimation screws just standard metric screws of a certain length? What specifically makes the worse? It must be different depending on the scope with the verity of thread son corrector plates on EdgeHDs alone.
Hi Randy, the Bob’s Knobs won’t tighten completely like the stock screws, so while it’s easier to get collimation with them, it’s also easier to get out of collimation as well. Since I rarely move my scopes around, it’s easier for me to keep the stock screws.
Great video Joe! I pretty much use the same procedure except I usually got for a bright star. Mine has held collimation really well.. Ive only had to redo it 3 times in the past couple of years. On cooling.. I find that mine usually needs about an hour before I can kick of the sequence.
Thanks James! That’s great to know about an hour for acclimation. Mine is normally mounted in the only and the temps in there are just slightly warmer than outside.
What do you do if you collimate inward focus first and then when you try outward focus the collimation is still off?
Hi SA, it’s been awhile since I made this video, but I believe I mentioned that you always collimate on outward focus. I’ve tested both ways and I can only get mine to work correctly and consistently when using outward focus. Hope that helps and apologies if I didn’t mention in the video.
You should look into the TriBahtinov Mask! If you have access to a 3D printer or laser cutter, it really makes it so much easier and faster, there’s zero guess work as well.
I have compared to Metaguide (which I believe was one of the best collimation tools) and it fully validated my results!
Thanks so much Noah! I've heard of those before, but have not tried it out. I will try and print one out now that you mention it here. Thanks for that.
The masks are inexpensive, got mine at Farpoint.
@@Dennis-tf2cs Thanks Dennis, will check it out! Anything inexpensive to make the process easier is a win in my book!
Good video tutorial Joe
For the Tri-Bahtinov mask, I uploaded the 3D printing stl files for the mask and the mask cover to fit the Edge HD 8 in the Tri Bahtinov thread on the Cloudy Nights forum a few weeks ago
Cloudy Nights forum thread topic :”A Tri-Bahtinov mask for SCT collimation and focusing”
Wishing you clear skies
@@acapulcoastro5967 Thanks so much! I'll try it out!
It’s too easy to keep chasing perfection and waste so much observing time, in my humble experience. Mind you, I use a vintage C5 and C8, so I collimate manually, without your technology, jumping back and forth between the corrector and the ocular-not too much much fun. Should that make it easier or harder?
There's something I don't understand here. At the end, the center star is concentric, but the stars near the edge of your view are not. Don't they all have to be? Thank you.
I understand that to minimize the effects of mirror shift, the "final" mirror movement should be up/out with a corresponding CCW focus shaft adjustment. Moving back through the focus to see the "other side" of the doughnut, the images should be pretty much the same. When you were centering the right star, I did notice that the star on the upper left did not present a good concentric doughnut shape which is NOT what one would expect for an Edge HD mirror. Celestron touts a flat field focus for this HD series and in my opinion the upper left star should also be displaying a lot better doughnut than what this video shows. If l were to have noticed such an out-of-round doughnut on the left star, with the right star having a perfectly centered doughnut, I would be contacting Celestron for an RMA to provide/REPLACE what they advertise; as in this example BOTH STARS should be damn near identically concentric.... Catch my drift???
Thanks Hank, I’d have to go back and rewatch the video as I don’t remember, but I love the images I’m getting from this scope. It may have also been an error on my part in the video or in the collimation process, I’m not sure. Thanks for pointing it out though.
Watching this vid is putting me off buying a sct lol. I can see myself getting very frustrated with this.
Hi Neil, I won't lie, it can get frustrating at times, but it's really not too hard after the first couple times you do it. The first time it took me almost 30 minutes to get it, but now I can collimate usually in less than 5 minutes. The nice thing is, it holds collimation pretty well and shouldn't have to be done too often. If you could afford a 2000mm fl refractor, I'd definitely go that route, but unfortunately, I couldn't justify that kind of money.
I watched this video a second time and its still not clear if you were tightening or loosening the screw on the large side of the doughnut.
This was challenging to get the camera high enough to see the secondary mirror and screws without shining light into the SCT. This is one of those times you really needed a second person operating the camera. The important part to take away though, is that you may need to tighten or loosen the screw, but whichever way you decide (tighten or loosen) the star should move on the screen towards the widest part of the donut. If it moves the opposite direction then that was the wrong way. Hope that helps.
You can collimate a lot more accurately than guessing visually how centered your secondary is.. there are tools to measure it
Thanks Derek, very good point. I’ll have to try some out.
@@JoesAstrophoto I also couldn't see why the star next to it was distorted and out of collimation... Was that with a reducer in place?
Sorry, but this collimation will not hold. You never collimate by loosening screw.
Proper collimated SCT will never need again adjustments, when it is in observatory.