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Hi,

i have a new Daystar Quantum 0,5 and Explorer Scientific 127 APO.
My question: Do I need an ERF filter, or is it just a Baader UV / IR filter?

Thanks

Better to use a full size DERF. Do not take these risks at your own duty.

Not to contradict Valery, but I’ve used the Baader uv/ir cut filter as ERF for the Daystar QPE0.6A on a 100mm f12 (Istar objective) with no problems. Daystar has recommended the use of full sized ERF for objective diameters larger than 100mm. A front mounted ERF is the best solution, especially as it reduces internal tube heating which can degrade seeing.

p_zetner wrote: ↑Thu Jul 05, 2018 3:18 pm Not to contradict Valery, but I’ve used the Baader uv/ir cut filter as ERF for the Daystar QPE0.6A on a 100mm f12 (Istar objective) with no problems. Daystar has recommended the use of full sized ERF for objective diameters larger than 100mm. A front mounted ERF is the best solution, especially as it reduces internal tube heating which can degrade seeing.

Similar etalons manufacturer has suggested to use a full size ERF for such an expensive Ha- filters. Otherwise the longevity of a filter will shorten.


Valery

The Baader UV/IR on paper blocks more UV but in practice does not seem to be good for use as a basic internal ERF. Many years ago we suggested this filter and one day put a polariser behind it to tame the light level a little. The scope was a 100mm. The polariser did nothing. When checked its coating had burnt away! We also saw that Quarks 'went off band' after about 30min. You would think the blocking filter would kill any residual heat but maybe not. More tests showed that UV/IR cuts pass quite a lot of heat energy. Put you hand behind the filter. You will see what I mean. If you use a 35nm Ha filter the light is cool and this is much better for the Quantum.

Even so why buy an high end filter and then use a lower performance ERF. A dielectric ERF will not suffer from spherical aberration like an internal filter and overall will be sharper and higher contrast.