Some people love LP filters, others despise them. I’m sure there is a long history of filters that may have made things worse rather than better, but if you ask us, it’s time to change some opinions of LP filters and learn to enjoy them when they’re useful.

Our backyard skies are rated from bortle six to bortle eight… leaning more towards Bortle 8 with some recent expansion and developments in our area. Shooting OSC or RGB color is proving to be extremely difficult – even on a new moon. Short of just admitting defeat and shooting broadband only, we decided to buy an Optolong L-PRO and give it a run through.

This guide will be a living document as we image and share our experiences with this light Pollution filter. As always, we love hearing feedback from readers. Let us know your experiences!

Optolong L-Pro

The Optolong L-Pro filter is a light pollution filter optimized around reducing sky glow and common city light pollution bandpass ranges. The filter is designed to enhance contrast and we must say, it does an amazingly well.

We’ve only been able to test it in our backyard in the “worst of skies” and the weather hasn’t fully cooperated, however, we do agree it does an excellent job with contrast. We’re working on some dark nebula imaging that would have otherwise been impossible in our backyard and it does make the dark nebula pop.

Emission Lines

Best Uses:

Galaxies, Reflection Nebula, Star Clusters, Globular Clusters and Dark Nebula imaging.

Test Rig

• Esprit 120
• Apex L .65x Reducer F 4.55/545FL
• ASI2600MC Pro
• Optolong L-Pro 2″ inside ZWO EFW

Telescope sits on an EQ6R Mount in our backyard observatory currently. Images we’re all acquired through NINA 1.11 Nightly Build.

Andromeda M31 imaged with L-Pro

Imaged October 24th, 2020 – near 50% moon.

Bortle ~8 skies – North Austin

140 subs at 90 seconds each at 0 gain on an ASI 2600MC pro – I’d like to try and do another shoot at Unity gain with 140 subs and see how/what kind of differences come up. (will update this post If I can get it done!)

PixInsight Workflow

WBPP Integration with Lights, Flats and Flatdarks. Dynamic Crop -> DBE with points nowhere near galaxy -> Background Neutralization -> Color Calibration -> EZ Deconvolution -> EZ Denoise -> EZ Softstretch -> Curves

Gradient removal was super easy compared to unfiltered M31.

Overall – the processing of this data is straight forward. A simple DBE worked well to get rid of the green gradient from RGGB bayer and from there it was simply basic editing skills. Can’t wait to try and get some more data on M31 as well as start imaging M33

Single Sub Analysis

Seeing wasn’t that great – 80-90% humidity with bright moon.

 Andromeda_Nebula_00_08_27_temp_4_50_exp90_00_0028_g0_o50_c
 Calculating SNR
 Channel #0
 SNR = 2.080e+01, 13.18 db  


 Andromeda_Nebula_00_08_27_temp_4_50_exp90_00_0028_g0_o50_c
 Scaled Noise Evaluation Script v2.1 - Bayer CFA Version
 Calculating scaled noise standard deviation…
 Ch |   noise   |  count(%) | layers |
 ---+-----------+-----------+--------+
  0 | 1.094e+00 |   80.38   |    4   |
  1 | 1.114e+00 |   80.86   |    4   |
  2 | 1.113e+00 |   80.78   |    4   |
  3 | 1.135e+00 |   83.34   |    4   |
 ---+-----------+-----------+--------+

Download M31 Data

Download the M31 Andromeda Galaxy with L-PRO stack and experiment with our data.

These are APS-C sized images – 26.1 megapixels captured on an “OSC” cooled astrocam. (One Shot Color) – Fits image coming soon.

This work is licensed under a Creative Commons Attribution 4.0 International License.

Buy Online

Wrap-up

Overall, I’d recommend the L-PRO if you live in bortle 6 or higher skies. I consider it a sound investment for a decent LP filter that can extend your broadband imaging through moon and city light pollution. Obviously, nothing beats dark skies and new moon – but I I do think there is great value in extending your broadband imaging times beyond those new moons that usually have clouds anyway.

Light pollution filters have really come a long way and I’ll update this review/guide as we collect more data. Testing this filter out sure seemed to bring in the curse of the cloud. We’ve been trying to image M31 and M33 for weeks now!