I picked up a wee double stacked PST. It's a standard PST with newer components (the blue element, brand new ITF) and a Solarmax 40mm II module that threads on the front without any special adapter. As advised by others, I first tuned the PST etalon itself without the SM40II installed, for best contrast and to be on band. Then I put on the SM40II and I used it visually and with camera to use the tilt mechanism to move the reflection off the disc and then did the final tuning. Seems to line up and worked. Visually it's much improved. I can see surface contrast no problem, the current AR2738 looks fantastic in the eyepiece, high contrast, the plages are bright, the fibril bundles are obvious and I can see prominences on the limb at the same time. So visually it's lovely to look through, nice and bright, and that's with a 13mm plossl for a full disc FOV.
My main thing I'd like to learn to tweak is imaging with it. Imaging is a different animal from visual. Visually I don't see a sweet spot. But imaging, I seem to see a sweet spot with gradients that have it fall off band in some areas and it loses detail. Also, it always seems to be rather soft. And even when I image with no gain at all, and stack a lot, there seems to be apparent noise of some kind.
PST (standard with new ITF)
Solarmax 40mm II module
ASI178MM with low profile adapter (reaches focus fine), 2.4um pixels
Things I'm having trouble with:
- Being on band and knowing it (as in inspecting the limb, high contrast filaments, etc)?
- Focus being critical or not (imprecise focuser on the PST of course, even with upgraded knob)
- What histogram to target (70% fill?) with no gamma to get proms and surface together?
- Processing without destroying the limb and not resorting to two exposures for limb/proms/surface?
- When lifting proms from shadows, I cannot do it without also lifting a huge cloud ring around the disc that masks the proms?
RAW TIF's attached (both a flat calibrated and non-calibrated)
Some currents tests showing what I'm seeing:
Here's the result
Here's how the disc is with no flat calibration (to show the hot spot, sweet spot, etc):
Here's processing out the gradients without flat calibration:
Here's the flat calibrated disc, lifting proms (100 frames stacked) with the ring around the disc:
Trying to see if I can do a lot better than this (which I do NOT like the glow... ugh):
Trying to figure this out. Maybe my equipment is just too low of quality to continue with this. If I cannot get this to work with full discs with one shot and process from it, I may switch to something else. Was simply seeing how much could be done with a PST like this.
Two RAW files attached (right click and open in new window or save, they're around 6~7Mb) if you want to inspect them.