Filters on the Hyperstar 4

My usual filter on the Hyperstar 4, on a C11, with an ASI 2600MC Pro CMOS camera, is a simple UV/IR cut filter. And this does the job admirably. But in my Bortle 4.5 zone I would like to filter out some of the background rubbish and get even more performance out of the Hyperstar.

To this end, I have tried an Optolong L-Enhance filter which filters in the H-alpha and OIII and filters out the rest. Doesn’t seem to help the Hyperstar much as far as I can see, which just means the filter is not good at f#2. Not too surprising really, and pretty much as expected. However, I switched it over to the Canon 200mm prime lenses where it would provide an f#4.2 aperture – and the results are superb. Win some lose some.

Just seen that Starizona also sent me an Optolong L-Extreme filter as well. As I haven’t tried this out on the Hyperstar yet, I just fitted it this morning. I will do a test run on an object where I already have plenty of UV/IR cut filter data to compare it with (probably the Pelican nebula) and I will get back to you with the results. I am expecting that, once again, the results are inferior to a plain UV/IR cut filter, but you never know.

I used the Optolong L-Extreme filter to image the Gamma Cassiopei nebulosity with 15-minute subs! Now 15-minute subs with the Hyperstar are as you know, nothing to be sniffed at. And the result? Very disappointing unfortunately (for 15-minute subs).

So it is as expected, I don’t have any narrowband filters to hand that will help me reduce my local light pollution that work well at f#2. Any filtering will therefore be carried out on the 200mm lenses or the Sky90 array only.

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