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EDIT: I THINK I'VE GOT IT NOW. If your images look like the ones at the bottom of this post, you may need more than simple Collimation (You've probably got the secondary mirror so far out that Collimation won't work. This can happen from too much over-Collimation, or from replacing screws.) I will have to wait for a clear night to confirm, but.... See my photo below of the secondary mirror, photo added after the other ones. I finally took the secondary mirror off. The gap on one side was so far wider than the other side that no amount of knob twiddling would help. I took the Bob's Knobs fully out, put each one back in just enough to hold. Then turned each one a half turn, went to the next, did a half turn, etc, until all 3 were finger tight. Was MUCH more even. Here's a video on how to do that: https://www.youtube.com/watch?v=EcKQFutDEAw&t= Before I did this in the morning I looked at a mountain 4 miles away with the scope and it could not get in focus. After I did this, I could get it in pretty good focus, could see individual trees on that mountain 4 miles away. Not perfect, but was windy and cold but the sun was warming the fields up between me and the mountain. (Also the eyepiece I was using was a cheap one.) I was able to ID a woodpecker on a tree about 700 feet away. So I think I've gotten it close enough that I can now do normal columniation process on a clear night on a bright star I should be able to get it in. It's going to be cloudy next few nights, so when it's clear I'll try and report back. Thanks to everyone who helped, especially to the person who suggested this.  =-=--=-=-=original post posted before the above edit: Something's wrong with my Edge HD 8. I figured out tonight that the problem I'm having with my Edge HD 8, stars are kind of bird shaped and not tiny when in focus (see photos of M45 I've included), exists even without the OAG, reducer, camera, etc. I removed all that tonight, even the EAF, and went back to basics. Took everything off the scope. Then put on the Visual Back, Star Diagonal, and the 1.25 inch eyepiece, and manually focused on M45.With my eye I was STILL seeing exactly what's in these photos. If I focus as small as the image will do, I see the bird shapes, which are at least 10x bigger than a star should be. If I get out of focus, I see the other two photos, and see the same thing if I go back to bird-focus and go the other direction out of focus. SOMETHING has changed since I got my scope (used). The night I got it I put on the visual gear and looked at the full moon. It was perfect, even stunning, all the way to the edge. All I've done since then is add Bob's Knobs, correctly, one at a time. Haven't dropped the scope, bumped it, nothing like that. I'm assuming it's something with the secondary mirror that can't be fixed with columniation, I've tried that. I understand columniation, used to have a Dobsonian. But no amount turning knobs in any direction fixes this. Anyone recognize this issue? Thank you    |
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| I suppose it's the Bob's Knobs installations that did it in, I'm afraid. I never used 'em when I had ny SCTs for precisely the same reasons you see here. The images show you are waaaaaay off axis. I mean really really waaaaaaay off and that is why the adjustments don't seem to have any effect. Best thing for you is revert back to the orginal bolts and use a laser collimator taylored for SCTs to bring everyhting back in co-aligment again and then do the fine tuning only with the vsual back and high power EP in focus. Needless to say, no reducer here. |
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| (Just a little service note: @Michael W. Dean, it's not advisable to create 3 different topics for the same problem, because that's more notifications for people and scattering of information for future reference when people Google stuff and end up here. Thanks for understanding!) |
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Salvatore Iovene: Understood. I didn't know what else to do. If I post this as a comment on the first post it will not be seen, and people will keep replying on that to a problem I don't have. I didn't have all the info on the first two, until I tried all the things people suggested there. I did edit the first two to add a link at the top to this one, so anyone going there will be directed here. If you want to delete the first two, they really are chasing down a wormhole that probably won't help anyone. Didn't have all the info until this post. I'm having an issue that as far as my googling can find, not many people have had, so chance of someone finding it as a comment on the bottom of the others are slim to zilch. Thank you. |
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No need to delete the other two, I think this is just a general forum etiquette rule of thumb and not specific to AstroBin. When you post to the forum of an equipment item, the users of that item get notified. Interested people will reply. When you add a new reply, people who have previously written a post in that topic get notified. So the best approach would be: - Post an initial topic - Reply to what people are telling you in the same topic - In addition to the reply, if necessary, consider editing the top post to add the new information, for the benefit of people who will only read the top post and not every single reply Hope this helps! |
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andrea tasselli: I really had a lot of trouble using the Philips head stock screws. I'm short and don't see well in the dark. Are there Hex-head bolts that work better than Bob's that would work? thank you. |
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Michael W. Dean: Funny, I thought all SCTs had hex-head bolts but they must have changed things since I last had one of 'em. Since you cannot undo what you did might as well go down this rabbit hole anyway. Get from whereever you are a set of 3 with exactky the same thread length (measured from the head) as the original ones had. Make sure they are either coated or stainless-steel. |
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andrea tasselli:Michael W. Dean: Thank you. Needs to be the same thread ratio though and I don't know the correct one. Otherwise might cause worse problems including stripping the internal threads. |
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| Apparently, but I can't be sure since I don't have them, they are M3x11.5mm with 0.5mm thread. They may list the specs on Bob's Knobs but I didn't check. |
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It has been a while since I owned my Edge HD 8, but I used Bob's knobs on mine. They worked just fine. They are just a screw with a more convenient head than the Philips head that comes with the scope, so there should be no problem. They are designed for the EHD8. It seems like your collimation is just way off... Silly question, but are you sure it's not simply a case of needing to pull it back in line? It's easy to knock it out when installing the knobs. I had to re-do my collimation and move thing A LOT when I installed mine... I purchased an artificial star and collimated it in a dark, long hallway-room in my house. That got it close and I finished up outside on a real star. I hope that is helpful. Good luck! Tim |
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Tim Hutchison: I HOPE it just IS way out of collimation. How long was your hallway? I heard you need 150 feet to use an artificial star with this scope. I have enough room outside at my place for that but would have to take the mount out of the observatory and move everything. Someone suggested turning the scope upside down, removing the secondary, putting it back on as a sort of "reset". What do you think? |
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Here's a link to Dylan O'Donnell's video on collimation that I found helpful. it sounds like something wonky happened when you installed Bob's Knobs (which I like by the way) and you may need to follow these steps to get it back to where the adjustment screws will be effective. Hope this helps. Good luck! https://www.google.com/search?q=Collimnation+Dylan&rlz=1C5CHFA_enUS752US753&oq=Collimnation+Dylan+&aqs=chrome..69i57j33i299.28641j0j7&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:cfc946bc,vid:EcKQFutDEAw,st:0 |
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Michael W. Dean:andrea tasselli: I did put Titanium hex socket screws on mine which for fine tuning are great. Found the right ones in a motorbike shop |
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Michael W. Dean:Tim Hutchison: If you have a fastar scope you can always indeed remove it carefully, check if the mirror seems to be more or less straight instead of completely canted. shouold be abel to do that in 2min tops. if not you may djust your knopbs to get it roughly level before fine tuning it. |
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Michael W. Dean:Tim Hutchison: "resetting" won´t do much, it will get back in the samne position though, but it could allow you to see if ot looks way off, visually |
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Gary Indra: Thank you. I may remove the mirror and check it as he does to get it in rough. If that doesn't help, something is very wrong. |
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"resetting" won´t do much, it will get back in the same position though, but it could allow you to see if ot looks way off, visually OT? Optical tube? |
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I think these would work: Amazon.com: Prime-Line 9180446 Socket Head Cap Screws, Class 12.9 Metric, Hex (Allen) Drive, M3-0.5 (10 Pack) : Industrial & Scientific |
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One thing to check is the mirror alignment. Look down the central axis of the scope from the front. The reflections of the secondary mirror and baffle tube should be concentric with each other (similar to the attached image). Note that in the attached image, there is a slight offset. The idea is that, if something is misaligned, one or more of the black rings (reflections of baffle tube/secondary mirror) will be offset. Try to get the outer reflection (upside-down me) so that it is even all the way around. Then, if one of the inner reflections are offset it is out of collimation. If it's offset by a large amount, or you can't get the outer reflection of me even all the way around, either collimation is very far off or the primary mirror is tilted to the axial plane. NOTE - this is not a great way to collimate the scope since it is very difficult to get your head/camera precisely on the optical axis. Not bad for checking gross misalignment though. Tri-bahtinov mask works great BTW. Also, if you take the secondary out and the secondary mirror is tilted significantly, this is an issue. Adjust the screws so that the secondary mirror is parallel to its holder and try collimation again. Be carful not to loosen the screws and release the secondary mirror from the holder. Jason  |
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Jason Schella: I'm on it.  |
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| Well seems like the issue is clear now! |
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| Therefore it is a problem of the main optics and not of the optical train. It was enough to check with the camera directly rather than also inserting the reducer. I didn't follow the post entirely, I might have missed that step. |
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Salvatore Iovene: Salvatore, I did what you suggested here and on my CloudyNights thread on the same topic. Instead of starting a new thread after I think I solved it, I edited first post here and there, adding new info at the top, keeping in the original first post, and clearly marking the edit as EDIT. Someone on CN got mad that I did that. He said "I've removed my posts from this thread because you've now edited the OP in a manner that makes nonsense of many of our comments." But I didn't make nonsense of his comments. They still work. Maybe it isn't "general forum etiquette" (or that guy has non-standard opinions on forum use, I think that's more likely). I guess I'll keep doing what Salvatore suggests, on any site if I start a post but then get new info, it makes sense. I just wanted to point out that my vibe of "make a new thread" was based on thinking it made more sense at the time and having run into people like him in the past. |
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Jason Schella: FYI my scope looked correct like that from the front. I forgot to add that when I got all excited about finding the problem with the secondary's tilt that I guess I introduced while adding Bob's Knobs with what I thought was the correct manner (one at a time). If I ever replace the screws again (I will if I can find ones that fit and are hex key head and don't rust), I'll take the whole mirror assembly out again to to it. To be clear, and I've said this before but want to say it again, Bob's Knobs weren't the problem. It's that replacing the screws with any screws (even if they were copies of the stock screws) can introduce a problem. |
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Yeah it's easy to mess your collimation complètent as you did. That's why they recommend changing them one by one to stay close |
