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OSC filter for 135 Rokinon at f2.8

Optolong L-Pro Light Pollution Filter Acquisition Gradient Removal Deep Sky
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Dan Kearl avatar
Dan Kearl avatar
I looked a bit here and I am sure its been discussed but which  filter is the consensus winner,
Dual NB or LP, I am using the L-Pro but am not happy at all with the gradients it leaves after calibration in my bortle 8 sky.
I use the 135 with a 294mc. I am well aware of the issues with that camera but I can calibrate the images very nicely with longer FL scopes
in the f5.6 range.
Not so much the 135 at f2.8 with the L-Pro.
Oscar avatar
Oscar avatar
One guy told me that a UV-IR cut filter will give you a more natural image, if you integrate long enough, in light polluted sky, then a filter that cuts out snippets of light, like an L-Pro. Note that I say more natural, and not free of gradients.

For the nebulae, dual NB is always the best.

This is my personal plan, which anyone else can follow:

UV-IR cut:
Stars
Galaxies
Star clusters
Lunar
Planetary
Reflection nebulae

Dual NB:
Emission nebulae
Planetary nebulae
Supernova remnants
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Luka Poropat avatar
Luka Poropat avatar
I would say broadband light pollution filters are basically pointless, I have never seen a good image taken with them with accurate colors and such. 
Given you are in bortle 8 something like 5nm or 3nm would be ideal. Depending on your budget I would look at the Antlia ALP-T or similar. 
Do also keep in mind at fast focal ratios there is bandpass shift so some filters like 3nm might not work ideally, thats why some preshifted filters exist (usually named also "highspeed").
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andrea tasselli avatar
andrea tasselli avatar
A wide angle lens such as this isn't the best choice for heavily polluted skies so no suprise you get a lot of gradients. A tight dual-band filter such as the L-eXtreme F2 would eliminate most of the LP effects but that would restrict you to image emission nebulae in the main. A tri-band filter will allow for a wider range of wavelengths to reach the sensor thus making imnaging bright boradband targets feasible but I'd imagine that galaxies aren't particularly useful targets with this lens (with the exception of M31 and M33, possibly).
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