Comparison of IDAS D2 vs Optolong L-eNhance Filters with DSLR

[PeterCPC]

I recently acquired an Optolong L-eNhance filter and wanted to compare it to my favoured IDAS D2.

I was able to spend some time on IC410 using a Skywatcher ED80 and my Canon 1200d (modded) DSLR.

The following images are taken from RAW images of 300 secs at 1600 iso. Generally I think that I prefer the results using the IDAS D2 in my area where there are LED streetlights. Might be useful to someone condidering the Optolong filter. The first is with the D2 and the second is the Optolong. No processing at all.

Peter

[happy-kat]

It's useful in that with the same exposure length it is visible the general light cutting of the second image though that might naturally be from differences in the light path bands between filters. Food for thought for me if at 300s at iso 1600 it's a direction that's not going to work for me. Trough I thought the idea of the second filter was more of a triband filter rather then a general light pollution filter so perhaps those results are as expected.

Edited December 3, 2019 by happy-kat

[FaDG]

1 hour ago, PeterCPC said:

Generally I think that I prefer the results using the IDAS D2

Hi Peter, thanks for sharing the result!

may I ask you why you prefer the D2 image?

In this narrow vs. Moderately wideband comparison, the signal seems comparable, but the Sky background is darker in the Optolong one, so you're not taking advantage of the NB ability ti increase the exposure time.

A comparison with similar background levels would also be interesting.

[alan potts]

I've been wrestling with this one and can't decide which to the extent I thought I may get both. I have a bit of an LED sky glow from the SE where a small town sits. The other nigh the lights went out here and around and it appears a bit worse than I thought though it was reflecting off patchy low cloud. I rather fancied the Optolong based on your two pictures.

Alan

[PeterCPC]

32 minutes ago, FaDG said:

Hi Peter, thanks for sharing the result!

may I ask you why you prefer the D2 image?

In this narrow vs. Moderately wideband comparison, the signal seems comparable, but the Sky background is darker in the Optolong one, so you're not taking advantage of the NB ability ti increase the exposure time.

A comparison with similar background levels would also be interesting.

The exposures are the same duration of course. To get a similar level of exposure I found that I had to use 400 secs with the Optolong. See photo taken at 400 secs ISO 1600.

Of course this all adds to the imaging time for each exposure and I'm not sure that it's worth it.

 

Peter

[happy-kat]

But it's a tri band so oii si and ha in one filter, so saves time. Isn't that the theory of these tri narrow band filters.

Edited December 3, 2019 by happy-kat

[PeterCPC]

Just now, happy-kat said:

But it's a tri band so oii si and ha in one filter, so saves time

Not for me because I don't do narrow band - I just do RGB with the DSLR but I see your point.

Peter

[happy-kat]

Might be fun to try one set of images as luminance then the other for the narrow band as a composite.

[happy-kat]

What bortle level are your skies please?

[PeterCPC]

6 minutes ago, happy-kat said:

What bortle level are your skies please?

Allegedly Bortle 4 but I think that is a bit optimistic.

Peter

[MartinB]

It's a bit difficult to compare because the D2 has the green colour cast.  I've tried to match the back ground bias and levels. Once this is done the D2 appears to be letting through more light, interestingly  including Ha signal, so, on this basis the D2 gets my vote.

[vineyard]

Thanks for sharing this.  I was actually going to post a Q asking folks for their recommendations on which light pollution filters are best (initially primarily for visual for me) - especially wrt the IDAS D2.  From a purely aesthetic purpose, I think the Optolong 400s (3rd image) is the nicest for my eyes.

Cheers.

[MartinB]

The  300 second bias corrected IDAS image is still showing more Ha nebulosity than the 400 sec Optolong.  The 300 sec Optolong shows fixed pattern noise because the exposure wasn't long enough for the background sky brightness get over the bias threshold.  This isn't an issue with the IDAS however.  On this basis you can use shorter subs with the IDAS whilst still gathering as much Ha signal.  The 400sec Optolong image might look a little better because it has had more reduction of the background brightness but the IDAS is delivering more data.

[PeterCPC]

1 hour ago, MartinB said:

The  300 second bias corrected IDAS image is still showing more Ha nebulosity than the 400 sec Optolong.

Martin - can I ask how you determined this?

Peter

 

[MartinB]

My monitor is fully calibrated using a Spyder 5 pro photometric device.  On my monitor only the IDAS version clearly shows the faint nebulosity extending above the main body of the nebula.  There is more nebulosity at the top right hand corner.  I have had a look now on my laptop and I can still see more background nebulosity with the IDAS image.  I know this is contrary to expected!  You can clearly see that the stars are fuller on the IDAS image which is exactly what you would expect from a broad band filter.

[PeterCPC]

Thank you for that.

Peter

[Star101]

I think the definitive answer is to process, to the best of ones ability, both images and see which comes out best.

The green cast, in the first image, does not help and is easily removed in processing.

Dave

[MartinB]

Sounds like a good plan!

[Amattice]

Did you have the same white balance for both captures?  Did you take separate flats with the filters in?

 

 

[PeterCPC]

Same white balance. No flats.

Peter