H-alpha SHG on 16 Oct -- it could have been better

[thesmiths]

We went back to our trusty 106mm aperture 720mm triplet refractor and tuned up the optics some more. We replaced the 135mm f3.5 camera lens with a 150mm f4 lens. The collimator remained a 135mm f3.5 lens so the system now has a slight magnification of 10/9. The solar diameter is now 3028 pixels. This provides a little higher sampling (both spatially and spectrally).

Unfortunately, just as imaging became possible during our short viewing window, clouds started to appear. We only manged to get one scan done of reasonable quality so no stacking was possible (stacking even a few frames does make a big difference).

The image below is a single scan which has been rotated so that the solar equator is horizontal. Most of the interesting features are currently in the southern hemisphere. The diagonal stripes on the right side are from slow moving clouds (which only got worse in subsequent scans).

H-alpha SHG image. Single scan, 720mm focal length, 106mm aperture. 2400 l/mm grating. 183MM camera. 9 micron wide chrome on fused quartz slit. Inverted and rotated with solar equator horizontal.

161022_Ha_720mm_rotate_crop.jpg (573.47 KiB) Viewed 1083 times

[DeepSolar64]

The detail is incredible here for a single image. Superb! Your SHG does really well.

[thesmiths]

Your SHG does really well.

We've been making some gradual improvements as we get more experience. We've now made it a lot easier to swap around lenses to change the magnification and sampling. We're now using standard M42 Asahi Pentax Super-Takumar SLR lenses so it's basically just the same as changing a lens on a vintage film camera. The Pentax lenses seem to be very nicely corrected across all the visible range and of course they are designed to project onto a 35mm flat piece of film. We also now use the built-in Pentax helical focusers (rather than an external focuser); these are extremely nice and smooth (if you get a model in good condition), with a large range of motion. My two favourite models are the 135mm f3.5 and the 150mm f4. Both are fairly light and use almost all of the 49mm diameter filter ring that lenses of the generation seem to have standardised on. There were so many of the them made (especially of the 135mm) that they can typically be found in almost mint condition for around $50. Lenses of this generation all seem to use five lens elements so are presumably a little more sophisticated than simple doublet lenses in correcting various sorts of aberrations.

[Montana]

Even for a single frame this is fab

Alexandra

[DeepSolar64]

Even for a single frame this is fab

Alexandra

Agreed!!

[marktownley]

Super results!