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Update
Trialled the UV-IR (Rosco) filter with the Wratten#25.
ED80 stopped down to 50mm ( didn't want to melt anything first time out!!)
Filters place infront of objective.
Ambient: 7.3deg ( It is winter in the UK!)
All readings after 30sec
Near prime focus, no filters: 36.4deg
Near prime focus, Wratten#25: 24.5deg
Near prime focus, UV-IR filter: 29.6deg
Near prime focus, UV-IR+Wratten #25: 20.4deg
Taking the temp rise with no filter as 100%, then:
Wratten #25: 59.1%
UV-IR : 76.6%
UV-IR+#25 : 45.0%
I had somehow expected the combination filter to significantly reduce the amount of heat getting through, certainly not just to 45%.
I'll do a comparison with the ERF filter on the PST objective, only 40mm, (without the etalon/BF filter), but will still be interesting.
Next thing to do is confirm the transmission curves of the filters with the spectroscope.
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