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Is anyone using an unmodified full frame DSLR with Hyperstar and C9.25 Edge? An APS-C sensor would be perfect since the image circle is 28mm; but what if you also image at f/7 and f/10 and don't have the luxury of having more than one camera? A FF frame camera covers the 44mm image circle at those ratios, with good stars to the edge (with the Edge :-) ), even if it's wasted with the Hyperstar. How 'bout Hyperstar LRGB with a FF mono astro cam? |
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| Hi MattI have been using a Canon 6D full frame DLSR as well as a Canon t3i APC DSLR with a 9.25 and Hyperstar. Both my cameras are modified to get more Ha. My 9.25 is not an Edge, but that should not matter, the same Hyperstar works for both (for the 9.25 only), and the extra optics in the Edge are not in the Hyperstar light path. The imaging circle of my version of Hyperstar is about 25 mm, so covers APC, but vignettes the corners on the full frame. I would say that stars are quite good out to APC size plus a little more (on my 6D), as long as you collimate the Hyperstar well (same problem whatever camera you use). I do find the mirror box in the DSLR really intrudes into the light path at f/2, so it is extremely difficult to use the edges of the frame, very difficult to make flats that can compensate. Also, with a DSLR you will get odd diffraction effects off of every edge, so you need to make a smooth oval shade to hide the DSLR, which cuts into the light path a lot in front of the corrector. But absolute must do otherwise stars will have all sort of weird shaped spikes. This shade also causes problems with flats, but with some work it is possible to get decent flats, aside from the edges of the image.You can look at some of my examples on Astrobin @rveregin . I have m31 and the Cocoon Nebula with my full-frame 6D, as well as for example M45 with my T3i. All images were been cropped, in the area I show stars are generally quite good to the edge--if they are not it is my fault for not better collimation. The FOV is quite large with the Hyperstar, so that is not such a big limitation to have to crop.There is a must article on optimizing the Hyperstar, and the challenges with a DSLR, by John Hayes:Hyperstar optimization Bottom line is I would not recommend that a DSLR is by any means the best for a Hyperstar, if one was going to buy a DSLR just for that, as it creates many issues. But with care and patience it can work very well, with the limitations above, if that is the camera you have now. And even with the obstruction of my camera shade, the difference in capturing nebula and galaxies at f2.2 vs. f6.3 is amazing.Rick |
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| Thanks, Rick. I may hold off on the hyperstar, then, until I get my astrocam, and in the interim, get a 0.7x reducer. I appreciate the input. |
