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So, I want to adapt the above mentioned lens to a qhy268 with cfw3. It is an autofocus lens. My question is, can you focus this lens without a camera for power source? Could i set the aperature with my camera and the connect to the lens bayonet adapter? Could i then focus manually without a powered connection? I want to adapt this lens to a focus motor bracket and use it for astrophotography, long exposures, etc. |
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| At least in the Nikon incarnation yes it can, since it can be switch to full Manual control. You might have a problem with the diaphragm since is the E-type, purely electro-mechanical. Not sure about the Canon model. |
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I can adjust the f-stop as i have a canon ef to sony adapter/controller. I am also looking at a usb power camera adapter that connects to m54, but i am getting no reply from that company. so if i bought the canon ef model of this lens, could i control just the focus without connecting any power/communication to the lens? thins would allow me to use my filter wheel and 268m |
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I have just check that in practice on my art 24-70 and inner lens moves without any external power. |
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so if i bought the canon ef model of this lens, could i control just the focus without connecting any power/communication to the lens? If it is the same as the Nikon model yes. |
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andrea tasselli:so if i bought the canon ef model of this lens, could i control just the focus without connecting any power/communication to the lens? Although in fairness I only ever used it with a Nikon body, so it's not proof positive that it can work with a T-thread adapter. Not that it matters to me as it would still need the electronics to set the diaphragm. |
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You can manually control the focus. You cannot manually control the aperture. The only way to control the aperture without a power source would be to take an exposure at the desired aperture with your DSLR/mirrorless camera, remove the lens mid-exposure, and then place it on your bayonet adapter. This is part of why the Astromechanics adapters were so revolutionary; they allowed unfettered aperture control on lenses that require a power source. Unfortunately, they are practically unobtainable now. External aperture rings/masks do not work, either. |
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You can manually control the focus. You cannot manually control the aperture. The only way to control the aperture without a power source would be to take an exposure at the desired aperture with your DSLR/mirrorless camera, remove the lens mid-exposure, and then place it on your bayonet adapter. This is part of why the Astromechanics adapters were so revolutionary; they allowed unfettered aperture control on lenses that require a power source. Unfortunately, they are practically unobtainable now. |
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| I just take a 30 seconds shot at f/2.8 and I take off the lens while is turned on. Well, it is not the best way, but once a month I have no problems.... |
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| I have used my Sigma Art 135mm f1.8 lens for several images. The focus works perfectly when connected to the ASSI2600MC via the adapter they have. It also includes a filter holder. The only drawer back to this lens is you cannot adjust the aperture from f1.8. the star images improve dramatically at f2.8 when i shoot with my DSRL instead. |
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ricardo leite: *** and with this the lens stays at f2.8? *** |
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You can manually control the focus. You cannot manually control the aperture. The only way to control the aperture without a power source would be to take an exposure at the desired aperture with your DSLR/mirrorless camera, remove the lens mid-exposure, and then place it on your bayonet adapter. This is part of why the Astromechanics adapters were so revolutionary; they allowed unfettered aperture control on lenses that require a power source. Unfortunately, they are practically unobtainable now. Could you provide a link to the powered adapter you’re referring to? |
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Andrew Murrell: So one could use a belt drive focuser on this lens and an astronomical camera? |
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You can manually control the focus. You cannot manually control the aperture. The only way to control the aperture without a power source would be to take an exposure at the desired aperture with your DSLR/mirrorless camera, remove the lens mid-exposure, and then place it on your bayonet adapter. This is part of why the Astromechanics adapters were so revolutionary; they allowed unfettered aperture control on lenses that require a power source. Unfortunately, they are practically unobtainable now. https://astromechanics.org they make one for the 6200 and efw, was hoping i could get one for the 268m and cfw3 |
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You can manually control the focus. You cannot manually control the aperture. The only way to control the aperture without a power source would be to take an exposure at the desired aperture with your DSLR/mirrorless camera, remove the lens mid-exposure, and then place it on your bayonet adapter. This is part of why the Astromechanics adapters were so revolutionary; they allowed unfettered aperture control on lenses that require a power source. Unfortunately, they are practically unobtainable now. I meant the “Sigma powered lens adapter” you referred to, not the Astromechanics adapter. |
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You can manually control the focus. You cannot manually control the aperture. The only way to control the aperture without a power source would be to take an exposure at the desired aperture with your DSLR/mirrorless camera, remove the lens mid-exposure, and then place it on your bayonet adapter. This is part of why the Astromechanics adapters were so revolutionary; they allowed unfettered aperture control on lenses that require a power source. Unfortunately, they are practically unobtainable now. |
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I see. So, all that will allow you to do is to set the aperture per-exposure when the lens is attached to your Sony camera. Getting good corners with the 268M will be tough. You’ll want to use a thin filter, ideally Astronomik MaxFR (which is 1mm optical thickness). Anything thicker will significantly distort the edges. Even the 1mm filter might not be good enough. Since the camera also has a glass window and a piece of glass over the sensor, it’s hard, if not impossible to get good correction. |
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I see. So, all that will allow you to do is to set the aperture per-exposure when the lens is attached to your Sony camera. Interesting, i do have a set of maxfr 12nm filters, astronomik deep sky rgb, and astronomik l3 filters anll in 2”. so you figure that out ven adjusting the backspacing with sub 1mm shims, the correction would be awful? Didnt think of that |
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| I suspect you'll be better off getting the Samyang 135mm f/2 with a lot less troubles if the main point of the lens is AP. |
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andrea tasselli: |
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I have found it is impossible to get acceptable field correction even with a 1" sensor when using a 2.5mm thick filter at anything faster than about f/3. With the 1mm thick Astronomik filters it was better, but still required adjustment. I've mostly stopped trying to get perfect spacing and have elected to just shoot star data separately with the lens stepped-down, but shooting the nebula data wide open. In my opinion, it's pointless to shoot nebula data with the lens stepped down. I agree with Andrea that the Samyang 135mm f/2 is the way to go if you want a fast lens setup for AP. There are tons of 3d-printed mounting kits for it too. |
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Be careful that there are numerous reports by astrophotographers about the inconsistent quality of Samyang lenses. Many of them say that they had to return for exchange, multiple times, until they get a good copy. If you buy from a retailer that can allow such return and exchange, and if you can conduct star test within the return period to verify the quality, then a Samyang lens could be a very good option. Otherwise be extremely careful. That being said, Sigma is not without problems either. I saw a small number of astrophotographers complaining about focal plane tilt under Sigma 135/1.8, this very exact lens, not other lenses from Sigma. However, overall, I would say that Sigma is still a much safer choice, if your can't buy from a retailer with very flexible return policies. |
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Ramma, I had the same problem unsing the Sigma Art 135mm lens on my QHY600 (which has the same dovetail connector than pre-2023 QHY268's). I solved this by making a custom adapter based on the QHY D3-adapter combo (I have the Nikon version of the Sigma lens, since I also own a Nikon D750). However, making this custom adapter was very cumbersome, since, as you noted, the aperture settings are purely electronic and you can't set them manually. And yes, the lens fully open (without aperture control) is not suitable for AP - at least not with full frame and/or a small pixel sensor. What I did was purchasing a broken Nikon camera and gluing the lens contacts of that camera into the QHY D3 adapter. I welded some wires to these contacts that I led outside the adapter and to a casing of a Nikon lens (again, a cheap broken lens purchased online). This way I can electronically connect my Nikon D750 DSLR to the Sigma lens and adjust the aperture as I whish. The DSLR stays on there for the entire imaging session. However, this is only where problems start: - In order to prevent the DSLR from switching into idle after some time (losing the set aperture) you have to depress the DOF preview button all the time. I solved this with a metal clamp. - The short back focus of the standard QHY600 does not allow the use of a filter drawer or filter wheel, excluding the use of a mono camera. - However, using a OSC camera you will still need an UV/IR-cut filter. My experience when trying to establish the correct backfocus for my setup (aside from any tilt issues) was, that, when inserting an M48 UV/IR-filter into the D3 adapter it will be impossibel to get nice round stars accross the frame. The filter glass between lens and sensor apparently causes some distortions that cannot be eliminated. The optics of that lens apparently are not designed to accept any additional optical elements in the image train (at least between lens and sensor). Which is exacly what @Eteocles describes above. So I purchased an UV/IR filter to thread onto the front end of my Sigma lens (a Hoya 82mm thread filter) and that did the trick. Using the Sigma lens and QHY600 without an UV/IR-cut filter will result in bloated stars. -With being limited to a 82mm front-end filter you lose the possibility of shooting narrowband or mono. - As for focusing I used this DSLR lens micro focuser, which workes pretty well: https://www.teleskop-express.de/shop/product_info.php/info/p3284_TS-Optics-Mikro-Fokussierung-fuer-Ihr-Kameraobjektiv-bis-105-mm-Durchmesser.html I attached some photos of my custom-made adapter to this thread (pictures tell more than a thousand words). The Vixen dovetail-rail everything is mounted to can also accept a standard guiding scope to accomplish autoguiding. Since I switched from an OSC-camera to a mono-camera (both QHY600's) this adapter is lying around unused since a year - which is a shame, after all this effort. The only project I did with this camera/lens combination is a 6-panel mosaic of the Taurus-Auriga dark clouds: https://www.astrobin.com/tkoag2/B/ Since this mosaic turned out pretty well I am thinking of getting an OSC-camera with larger pixels than the QHY600, probably the QHY410. However, the price of that camera is still pretty steep, which prevented my from grabing it yet. Hope this was helpfull & CS! Chris   |
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| For anyone who does manage to get their hands on an Astromechanics adapter, check out Dale Ghent's custom ASCOM driver and Astromechanics plugin for NINA. It's a game changer. |
