Just a quick test today March 8th, 2024. We are back in Germany and I left the Ha filter in our house. In sub-zero temperatures, a filter like this quickly breaks - the house is well insulated, but it hasn't been heated for 5 months. I took exactly one photo of the sunspot group AR3599 and AR3600 just to see that the filter was still OK.
(DIY) ED80 F7.5 / Baader Steeltrack (modified) with motor focus control / 78mm ERF. Baader 4x telecentric system, SolarSpectrum filter 32mm 0.3Å, ZWO ASI183MM Videos stacked with AutoStakkert and edited with imppg
2024-03-08t14_45_34_AR3599_AR3600.jpg (404.57 KiB) Viewed 181 times
Knowing how much efford and how long it takes to produce and get a premium etalon like this i have to admit it hurt a bit to read this.
But then again i dont think that there will be sub 0 temperatures in a house, even if not heated. I assume it still works.
I guess if you leave your filter in the cellar (keller) the temperature will for sure not go down below zero degrees. I do not know where you lieve in Germany but I think the frost limit is not more then 50cm? eg. the amount of the crust of the earth which freezes so your cellar should be ok for storing your astronomy equipment.
I would worry more for the water pipes in the upper floor. If these did not burst then your H-alpha filter should be OK
Like others have said, I would make every effort to ensure that filter is kept above ambient. They are rare beasts! I am glad it is still working though.
Have you tried 2x2 binning with the 183mm and this setup? It will give better sampling.
http://brierleyhillsolar.blogspot.co.uk/ Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
