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Any advice for connecting a QHY 183 to a canon lens for ultra widefield

Astrophotography CMOS DSLR Imaging
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#1 Mordred182

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Posted 26 November 2021 - 04:18 PM

I have a QHY 183 and a lot of canon lenses and i was hoping it would possible to connect the astrocam to the lenses to shoot more widefield DSO's because my only telescope right now is an edge hd 8in and I don't have enough cash to spend on a hyperstar right now but that's the plan in the future.



#2 SilverLitz

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Posted 26 November 2021 - 04:27 PM

Astromechanics EOS adapter can connect a Canon lens to an M42 or M48.  It has a very secure attachment, and allows computer control of the Canon lens, allowing both AF and aperture control.

 

https://www.astromec....org/ascom.html



#3 t-ara-fan

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Posted 26 November 2021 - 05:01 PM

The Astromechanics adapter is great.  Next: figure out how to attach the lens and camera to your mount. 

 

With my Canon 200mm prime I use a collar around the lens.  For shorter FL lenses, I have a ZWO ring that holds the cylindrical camera body. Look into the options for the QHY camera.



#4 Yilia Yu

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Posted 29 November 2021 - 01:38 AM

The combination of 183 with Canon EF Lens has been posted on QHYCCD website. Please check the link below to see if it can be felpful.

https://www.qhyccd.com/qhy183/



#5 1DegreeN

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Posted 30 November 2021 - 10:05 PM

The AstroMechanics adapter is very good. If you don't need electronic focus, Cyclops Optics have their Blade-C adapter. Both of these adapters can hold filters: the Blade-C holds a 2" filter whereas the Astromechanics adapter, for the 183C, holds a 1.25" adapter.



#6 nathanm

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Posted 01 December 2021 - 12:20 AM

I agree with the posts above - the Astromechanics adapter is good if you need to control the aperture, and/or if the lens is autofocus, and you want to use the lens motors to focus.

 

You didn't say which lens you are going to use. 

 

In my experience the lenses that can be used wide open are the 40mm f/1.4 Sigma ART lens, the 105mm f/1.4 Sigma ART lens, the 135mm f/2 Zeiss Sonnar, 200mm f/2 Canon.   All of these are pretty good out to the corners at their widest setting.

 

Purists may want to stop down a bit even with those lenses but I find that stacking and using them in a mosaic they work fine.

 

Of these only the Sigma and Canon are autofocus.

 

If the lens is not autofocus you don't really need the Astromechanics adapter.

 

Note that I use QHY410C or 128c.  The 183 is a much smaller sensor so maybe you can get away with wide open.

 

I have all of the Canon super fast wide angles - 24mm f/1.4 both models, 35mm f/1.4 both models, 85mm f/1.2 both models, 85mm f/1.4.  These all have poor quality stars in the corners and edges of frame due to Coma - it is the "flock of seagulls". 

 

I also have the Zeiss Otus lenses - the 55mm f/1.4, 85mm f/1.4  - they also have a lot of coma, although they are spectacular during the day.

 

Nathan



#7 nathanm

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Posted 02 December 2021 - 07:34 PM

As requested by a previous post in the thread, here are images from 200mm f/2 Canon, shot at f/2 with a QHY 128c  one shot color cooled camera.  The pictures below are all excerpts from a single 6 second exposure.  It has been calibrated, but nothing else.

 

Note that I use this lens to make mosaics, where the edges of one frame tend to overlap with the edges of the frames around it.  Typically that would 15 frames per position.  Which means in the edge regions, there are 30 frames stacked, and in the corners it is 60 frames stacked.   The overlap is chosen to be wide enough to pretty much cover the area with distorted stars.

 

Coma and other lens aberrations tend to make the stars distorted toward the edge of the frame, and especially the corners which are the furthest you can get from the center.  The Canon 200 f/2 is no exception - but the distortion that occurs is fairly small - the stars get elongated, and can have pointed tails, pointing outward from the center.  

Other lenses are far worse and they distort into seagull like shapes which are widest perpendicular to a line drawn from the center.

 

As a result of the small and directional distortion, when I stack them in a corner, the pointy parts tend to average out and I get a round star back - not perfect, but in a large mosaic they are completely usable.  

 

If I was taking a single position - i.e. not a mosaic, then I would stop the lens down to get better corner quality - say to f/2.8.

 

 

Top left corner

 

gallery_334946_14430_259053.jpg

 

Top right corner

 

gallery_334946_14430_50589.jpg

 

Center

 

gallery_334946_14430_828473.jpg

 

Bottom left corner

 

gallery_334946_14430_964698.jpg

 

Bottom right corner

 

gallery_334946_14430_677712.jpg

 

 

Nathan



#8 T~Stew

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Posted 03 December 2021 - 09:29 AM

The AstroMechanics adapter is very good. If you don't need electronic focus, Cyclops Optics have their Blade-C adapter. 

 

I agree with the posts above - the Astromechanics adapter is good if you need to control the aperture, and/or if the lens is autofocus, and you want to use the lens motors to focus.

 

 

 

With the exception of the fly-by-wire old canon lenses... their manual focus is electronic actuated so even to manual focus you still need power (the fancier electronic adapter not a simple mechanical lens mount adapter). For example my EF 300mm f2.8L is electronic manual focus, not sure how many others were. 



#9 nathanm

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Posted 03 December 2021 - 12:50 PM

If you have a fly-by-wire lens, then yes you need the astromechanics adapter.   But you will also need a focus motor in that case - otherwise it is an autofocus lens.

 

A lot of the wide field lenses used in astrophotography - like the Samyang/Rokinon series - are strictly manual.




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