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Is there a way to screw these two together? tightening the screws in the guide scope cause tilt/coma effect  |
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Do you use the extender that comes with the camera? Be sure to not over-tighten it. I've not seen any such issues with my 174minis. Not sure how this scope is built, but if the scope only has screws touching the camera you could perhaps add a helical focuser or a 1.25" holder of some sort:  |
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Jan Erik Vallestad: thanks for the fast reply. When you say over tighten, do you mean the extender onto the camera or the scope screws? Was hoping I could just screw cam onto scope like my main imaging stuff |
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TiffsAndAstro: I meant the screws on the scope, if they're unevenly tightened that may cause the sensor to be a bit skewed. At least that's what I imagine might be the cause. It's probably possible to get it screwed on somehow as the scope has external threads, but I'm not aware of any adapters that might fit the 120mini. It could perhaps create too much distance to the sensor as well. The good thing about those adapters I mentioned are that they put more evenly pressure around the camera than single screws probably could. If the scope has inner threads it might be a bit easier though. I used to have a finderscope attached to my old 120MC-S camera for guiding before I went with the OAG solution. Then I had this adapter which made the connection possible:  They also have a T adapter. EDIT: If this adapter fits the mini as well you could probably fit some spacers in order to get a screw on connection. As long as you can find a M51 F to M42 M adapter. |
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Yeah that's more like what I'm after. I think. I'll email retailer see what they say. THe tilt is definitely caused by screws decentering camera. If I don't tighten them the camera falls out. Trying to tighten both same amount is incredibly frustrating though. I wonder why YouTubers reviewing this combo all forgot to mention this issue.... |
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My Celestron 0.7X reducer has the same mechanics, the ZWO L has the "band" mechanism. I have two similar scopes as the one you have, from SvBony because they are half the price but still the same, but I haven't used them yet. It depends on how bad the tilt is in your system, but generally I wouldn't care about some elongation in the stars. The 120mini has a much smaller sensor than the 174mini though, so it might be more prominent for all I know. All I know is that I haven't seen any of it wit the setups I have used so far. As to youtubers not going into all the specifics, I'm not surprised  I generally don't watch them though I'm sure there are both good and bad reviewers there, but I know for a fact that there are some really bad ones.
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Jan Erik Vallestad: I appreciate what you're saying but as a beginner it's hard for me to compare it to anyone else's I would say it affects my snr which effects my guiding. |
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TiffsAndAstro: I understand. Some elongated stars or even slightly out of focus stars won't affect the guiding by much at all, some even used to say that slightly out of focus was better for guiding. I've always focused to my best ability despite that though. Is your camera/scope focused properly? I know the focus mechanism of these are quite rough. The best way to test this, imo, is to go past where you think you have focus to find out exactly where the stars become out of focus again and then you are absolutely sure where to put it. Also, small sidenote, put a dew shield on it. Just a small tube that fits, whatever it is. If your camera is hanging far out of the guide scope try to push it all the way in to avoid flex, then expand the tube in front in order to be able to reach focus:  If your guiding seems worse than you'd expect, despite all of this, then there could be several other factors at play here as well which are mostly settings based but also depends on what other equipment you use it with. I've seen people removing the glass elements in order to blacken the edges to increase contrast, a pretty known method with vintage lenses as well. But don't do that unless it's an issue for you or you are comfortable with disassembling something like this. BTW: Just found out that ordinary planetary cameras, or the non minis, actually can be screwed directly on to the scope. That's pretty neat. |
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It's good enough focus until I tighten the screws. the nosepeice is all the way in except maybe last 3mm Tried testing last night but pretty similar results I'll wait and see what retailer comes back with. Than you for the help and suggestions. |
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I'm a bit confused what you mean with "all the way in". I use the same combination. I had to screw on this extension ring (about 15mm I guess) that comes with the camera and inserted it so that the whole back part dissappears in the guide scope and only the red part of the camera is visible. I made sure, the camera goes in there wide enough to be longer than the brass ring between the screws that tighten the camera and the camera itself. This way, the ring could not cause tilt. Then I used the screw on the guide scope (helical focuser) to focus the combo. It came out about 2 or 3 centimaters I guess (can't check it at the moment). If you put in the camera all the way in, the focusers screw have to go way out of the telescope. Maybe it reaches the end of the thread and this way is prone to tilt as well. Reading through your posts, it is not exactly clear how it looks in your case. Maybe you could send us a photo. It should be looking similar like this (first photo): https://forum.astronomie.de/threads/zwo-asi-120mm-mini-mono-30f4-sv165-guide-scope.358442/ In my case, the scope is working without any issues and I can't imagine yours is very different. hope you can fix it. CS Christian |
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Christian Großmann: I have approximately 3mm of the black nose piece showing outside the scope. I'll take a pic. Really appreciate your help and I'm pretty hopeful it's something stupidly obvious I'm doing wrong. |
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| I think you should slide the camera in about 5mm more. The brass ring inside is placed in a groove. If the end of the camera should not be where the groove is. If you slide it in more, then the tube is pressed on the wall of the scopes tube at both sides. If the end of the camera is in the groove, then the ring might press it against one of these walls on one side and in that groove on the other side. This might cause the tilt you see. Sliding the camera in a bit further might fix the issue. |
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| OK. I just realized that my scope looks different. But have look inside the scope. You might find what I described anyway. It seems that the screws are pressing at the camera right at the front edge of the rings. I hope it can go in a bit further. |
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Christian Großmann: tY for this, it sounds exactly like something that could cause the tilt. I will try it and see. Hopefully I have enough room to wind the lens out too I didn't even realise the scope had a compression ring |
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| No harm me having a look |
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Small update... So I do indeed have a compression ring, lol. I've tried a few positions and locked camera with the screws. With almost all of the black portion of the camera inside the guidescope, I can barely move the camera. So I'm very hopeful Ty again  |
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well it seems to have much reduced the coma effect surrounding my stars. there's thin cloud so maybe not best conditions to test but seems like a definate improvement ty if you spot anything odd though please say |
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| It looks totally familiar to me. This should've solved the issue... |
