Light Pollution Filters – Baader Neodymium vs Optolong L-Pro vs Astronomik CLS

[PeterC65]

I live in a Bortle 4 area so light pollution isn’t too bad, but there is one street light, some house lights and the occasional car, plus some glow on the horizon, so I’ve been using a Baader Neodymium filter for visual astronomy. I’ve recently started comparing it with no filter, and to be honest, the difference is marginal verging on non-existent.

A recent post recommended the Optolong L-Pro filter and this got me looking at specs. I have a handy spreadsheet that allows the overlaying of filter specs …

The Baader filter has always struck me as raged in that the pass bands are far from flat, and while the main stop band removes some of the main light pollution peaks, many are still passed.

The Optolong filter is much flatter in the pass bands and passes more light, and its multiple stop bands notch out all of the main light pollution peaks.

The Astronomik filter is similar to the Optolong but doesn’t have the narrow pass bands between some of the light pollution peaks.

The Baader filter probably passes more light overall so the Optolong and Astronomik filters are likely to give a dimmer image, but with more of the light pollution removed.

I have the Baader filter, but would the Astronomik filter give me a dimmer higher contrast view, and would the notches in the Optolong filter provide a brighter view?

 

[Paz]

I will be interested to hear any responses. I have a 1.25" unbranded (or an inexpensive brand) LP filter that I very rarely use but I've recently being getting a 2" set up together for use with my refractors and this included a 2" Optolong LPro. I have not had much time with it on the field or tested it back to back with my 1.25" filter but I can say it does noticeably dim the view although I didn't note how much of a magnitude less I could see. Where I am it makes the background darker but it also makes the stars dimmer. I will need some time in the field before being clear on the pros/cons.

[Louis D]

I did a quick Google search and found the following imaging comparisons:

https://star-hunter.ru/en/optolong-l-pro-clip-eos-review/

I would say it's more applicable to general imaging than visual from light polluted skies where maintaining color balance and shorter exposures is important.  Visually, it would have a subtle effect, but would probably be a decent choice for galaxies.  For nebula, there are better choices.  It just depends on what you want from a filter.

[Ricochet]

3 hours ago, PeterC65 said:

I’ve recently started comparing it with no filter, and to be honest, the difference is marginal verging on non-existent.

In my experience neodymium filters are good moon filters but useless for DSOs. The Astronomik CLS used to be reasonably effective on certain galaxies and star clusters where you can't use a UHC/OIII filter but that was when street lighting was sodium and the majority of light pollution was in the band that it cuts out. However, now that almost everything is LED the light pollution is across the whole spectrum and the usefulness of the filter decreases every day. Depending on the type of light sources in your area perhaps a CLS might give some improvement for now but I wouldn't expect any advantage to last. I'll have to give mine another go to see if it is still useful on anything but I don't remember using it for a while now. With the additional transmission spike in the middle of the cut out section I would expect the L-pro to be even less effective than the CLS. 

[Ricochet]

As it is clear I've just had a quick session with my 8" dob to give the CLS a go. Targets were the open clusters M35 and M37, the galaxy M51 and the globular cluster M3.

• M35, M37: 21E and 14XW. In both eyepieces the addition of the CLS dimmed the view and made some of the fainter stars disappear.
• M51: 21E - Slight improvement in visibility of the cores with CLS. 14XW - Cores visible, no improvement in visibility by adding CLS. Prior to LED lighting I remember the CLS changing the visibility from cores to cores and spiral arms.
• M3: 21E, 14XW, 10XW. In all eyepieces the CLS did not improve the view and fainter stars disappeared. I also tried the Baader Neodymium on this target and although it gave a more pleasing view than the CLS because stars were white instead of green, the unfiltered view was better.

The one thing that did make a noticeable difference was my Rsky observing hood, but I assume that recent events mean that we can no longer buy these and so you would have to find another item to block out any light not coming from the eyepiece.

[PeterC65]

17 hours ago, Louis D said:

I did a quick Google search and found the following imaging comparisons:

I also found some of these images. On the face of it the Optolong L-Pro comes out well, but I don't think photographs are representative of what is experienced visually, and I'm wanting to compare the L-Pro and CLS with the Baader Neodymium that I currently have.

17 hours ago, Louis D said:

I would say it's more applicable to general imaging than visual from light polluted skies where maintaining color balance and shorter exposures is important.  Visually, it would have a subtle effect, but would probably be a decent choice for galaxies.  For nebula, there are better choices.

The L-Pro is certainly listed by FLO under astrophotography filters rather than visual, but I assume that's because the narrow pass bands help with colour balance rather than because of some issue in using it for visual.

17 hours ago, Louis D said:

It just depends on what you want from a filter.

I use the Baader Neodymium when observing galaxies, star clusters and stars, and these are the targets I'm thinking might be better with the L-Pro. For nebulae I use the Astronomik UHC filter which I find works really well on these targets, and for the Moon I use the Baader yellow filter which also works well for me. I have other colour filters for the planets when they eventually appear (Jupiter and Saturn disappeared shortly after I got my first telescope!).

[PeterC65]

13 hours ago, Ricochet said:

As it is clear I've just had a quick session with my 8" dob to give the CLS a go. Targets were the open clusters M35 and M37, the galaxy M51 and the globular cluster M3.

• M35, M37: 21E and 14XW. In both eyepieces the addition of the CLS dimmed the view and made some of the fainter stars disappear.
• M51: 21E - Slight improvement in visibility of the cores with CLS. 14XW - Cores visible, no improvement in visibility by adding CLS. Prior to LED lighting I remember the CLS changing the visibility from cores to cores and spiral arms.
• M3: 21E, 14XW, 10XW. In all eyepieces the CLS did not improve the view and fainter stars disappeared. I also tried the Baader Neodymium on this target and although it gave a more pleasing view than the CLS because stars were white instead of green, the unfiltered view was better.

The one thing that did make a noticeable difference was my Rsky observing hood, but I assume that recent events mean that we can no longer buy these and so you would have to find another item to block out any light not coming from the eyepiece.

Your findings that the Astronomik CLS filter causes some dimming stack up with its spec. It'd expect the Optolong L-Pro to dim objects slightly less. I've observed M3 and M35 with the Baader Neodymium filter and felt that it made little or no difference. In some respects I'd prefer a light pollution filter that does make a noticeable difference as then I have it as a (different) option from just no filter. I use filter wheels so can easily switch filters in and out to decide which gives the best view.

[PeterC65]

Last night I tested the Baader Neodymium filter in the Mak. There was some light pollution from next doors outside light and on double, at higher magnification, x260, the filter did noticeably dim the background  sky while not affecting the star. In fact with my ES 6.7mm eyepiece the filter made it hard to see the edge of the circle of sky. So I guess it is having an effect. I'm still not sure whether the L-Pro would be better, although I do think it would have a more noticeable effect.

[PeterC65]

After much Google searching I found this excellent side by side video review of the Baader Neodymium, Optolong L-Pro, Astronomik CLS and Svbony CLS light pollution filters.

My conclusion is that I should probably stick with my existing Baader Neodymium filter and that under my Bortle 4 sky I shouldn't expect the filter to make a massive difference (it doesn't!).

So that's saved me £106!

 

[Louis D]

I thought the SVBONY CLS looked pretty decent under Bortle 9 skies in that filter review.  In a 1.25" size, they're only $30+tax shipped here in the States.  At that price, you don't feel too bad if it doesn't get a lot of use.