IDAS LPS Filters

Many users should start enjoying astro imaging with a new LPS filter – LPS-D2 these days. LPS family comprises 4 members which now widely cover various sky conditions.

Meanwhile, I’m having some common questions from several people too. I expected following plots clarified all. These shows how each filter works with each light pollution emission individually.

0408a

Click to go the page

In short, a bit too rough though

D2 : for white LED and HP/LP sodium

D1 : for mercury and LP sodium

P2 : for mercury and LP sodium

V4 : generally for all, nebula filter

Keep in mind, there is no perfect and no one-piece solution. Also the latest LPS-D2 is not always the best. As shown on a plot, if D2 filter is used under mercury-dominant sky, the image turns greenish or bluish cast. All depend on your sky condition. The point is how to figure out the best possible way while minimizing the compromise under your sky.

What is mercury vapor? or sodium? For the references, I link the pages described on them.

Mercury

Sodium

And what type/size of filter? that is next step and depends on your scope/lens and camera.

d2d1p2v4

As shown above, IDAS publishes the actual measured data (not designed value) up to 1100nm. Silicon-based sensor is still sensitive enough up to 1000nm or so. So for us, actually seeing how blocking 700 – 1100nm range is very important at “actual measured value”. So these data show what you get as commercial products.

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~ by tedishikawa on April 8, 2018.

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