Jim Thompson started a very interesting comparison of LP filters for EAA in this forum. You may want to check it out!
I recently got two different LP filters: the ubiquitous Optolong L-Enhance (mentioned above), and the IDAS LPS-D2. Both came as 2" filters, which I can easily thread into my Hyperstar.
My current setup: C9, ASI183MC uncooled, Hyperstar v4, Sharpcap.
I ran some quick comparisons with and without the IDAS fiter, on the same night. My sky is probably between Bortle 6 and 7 (the Milky Way is not visible).
Here is a side-to-side comparison of M33 with either the IDAS, or no filter at all.
In both captures:
- No flats, as can be seen from the vignetting.
- Gain 118, 30s subexposures
- no Sharpcap enhancements applied
- Sharpcap livestack histogram autostretch for both captures.
- no general histogram stretch
The only difference is the resulting histogram: the IDAS cuts a lot of light, so at this gain and exposure, there's little signal. I had to balance whites manually to compensate for the filter's tendency to put everything off, but the IDAS image retains its greenish cast...
Total integration time: 18min30s with IDAS, 20min with no filter.
Interestingly, the IDAS brings lots of detail that are barely visible in the no-filter shot. It also cuts stars (which an IR/UV cut would do as well I gather). On the negative side of things, it also gives that unnatural colored look to nebulas.
Edited by Clouzot, 30 October 2019 - 08:26 AM.