Upgrade path for solar equipments

The new offerings from Lunt's are very attractive for sure.

Right now the weakest link in my inventory is the bandwidth of my CaK filter, it's too wide that it's just better than plain white light view. No prominence in CaK is possible with that filter, and the constrast for CaK feature is also not high enough. Going for the new Lunt's 60mm CaK will definitely helps in terms of bandwidth. At the same time, I can sell my Baader CaK to pay part of the difference in price.

However, the Baader CaK is not without its advantage. Its resolution can be pushed by using a bigger refractor together with my APM Herschel Wedge. Right now the easiest accessible refractor is my Ranger which is 70mm in side, the Sky 90 could also be used but it's more in my friend's home. If I upgrade to the bigger refractor say a Borg 101ED or a William Optics 110ED, I can get higher resolution with it. And at the same time, the white light view will be improved at the same time. And of course, the bigger refractor will also be useful for some short exposure astrophotography (lower priority for me since my portable mount is a TG-SP II which is not enough for either refractor), and the bigger refractor will also help me to get better visual experience for planets and DSOs, a step above my C5. However, these refractors will not be easily useful for H-alpha since they're pretty fast.

In terms of H-alpha, I believe that I'll spend more effort in my C5/PST based setup first since it has the largest affordable aperture for me. In terms of bandwidth, maybe buying the 50mm model to double stack with my existing SM40 might be okay, however, it should not be way lower than my SM40/PST combination which is 0.6A already. Even two matched SM40 will give me 0.5A, so a 0.75A Lunt's 50mm and a non-specially matched SM40 will not give me 0.5A, so it makes no sense to do that. Going for a Lunt's 75mm might be good for aperture and bandwdith, but then it's not as narrow as my SM40/PST combination, and it's not as big aperture as my C5/PST. Therefore, it's not the best solution unless my C5/PST combination fails, however, the bottom line is, even if the internal reflection problem still persists, the resolution of the C5/PST is still high enough to win the Lunt's 75mm. I guess the 100mm Lunt's scope could be a good and sensible route, but then it's a bit too expensive.

So, the question is CaK only at this stage. Whether I want narrower bandwidth, or higher resolution.