Galaxy contrast enhancement filter

[bomberbaz]

Well this caught my attention whilst browsing yet another online shop, this time Okularum. 

Never heard of one of these before Filter  I know DGM have a good name for thier nebula (UHC) filter, so doubt they would market something that isn't effective.

Looking at the filter light curve graph next to the price tag it strikes me that it cuts out just visible light pollution as do all other filters and then lets everything else through. 

I did think it was similar to a neodymium filter at first but on closer inspection there are some significant differences, notably around the 550/5500 mark and to a lesser extent around the 475/4750 mark. The GCE also drops off the 500/5000 mark later than the baader.

Anyway, back to the DGM GCE, interesting idea that by blocking out light pollution wavelengths you increase the contrast which does make sense, but some of the dimmer galaxies would surely end up disappearing altogether.

Of course I know the best thing for getting the best out of your galaxy hunting is a dark sky, goes without saying but this has pricked my interest.

Just wondered what anyone else's thoughts are on this filter!

EDIT: Found a few reports on CN forums. Seems they offer moderate results generally on brighter objects in darker places from the outset.

Steve

[John]

Interesting find Steve.

The DGM NBP is a very good UHC so I would take other filters from them seriously.

So far I have not found a filter that helps with galaxies but I have not tried that one !

 

[Ricochet]

Similar-ish looking bandpass to the Astronomik CLS, which I think does help a small amount on some (but not all) galaxies. However, LED lights will pollute the wavelengths both of these allow to pass as well as the range that is cut. In that scenario perhaps the Astronomik is preferable as it has a chance of cutting some of the blue spike at about 450mn that a cool white LED produces. I'll have to re-test now that the motorway near my house has been "upgraded" from sodium to LED.

[bomberbaz]

2 hours ago, Ricochet said:

Similar-ish looking bandpass to the Astronomik CLS, which I think does help a small amount on some (but not all) galaxies. However, LED lights will pollute the wavelengths both of these allow to pass as well as the range that is cut. In that scenario perhaps the Astronomik is preferable as it has a chance of cutting some of the blue spike at about 450mn that a cool white LED produces. I'll have to re-test now that the motorway near my house has been "upgraded" from sodium to LED.

I would be very interested to hear of any results Ricochet. I am not rushing out to buy either but if something really does work to enhance the visual experience, I am prepared to consider.

thanks

Steve

[bomberbaz]

2 hours ago, Ricochet said:

Similar-ish looking bandpass to the Astronomik CLS, which I think does help a small amount on some (but not all) galaxies. However, LED lights will pollute the wavelengths both of these allow to pass as well as the range that is cut. In that scenario perhaps the Astronomik is preferable as it has a chance of cutting some of the blue spike at about 450mn that a cool white LED produces. I'll have to re-test now that the motorway near my house has been "upgraded" from sodium to LED.

This report on cloudy nights forum has a lot of detail regarding this filter and compares lumican's deep sky with the GCE, the results are as expected really. report

Strangely enough the report is from 2007, I thought this GCE filter was a fairly new thing, obviously not.

Steve

[jetstream]

Sadly enough any filter cannot increase contrast on galaxies, the bright sky reduces one of the 2 main components of actual contrast. Observing from extremely light polluted skies are the realm of NV IMHO, their primary use- again IMHO.

[bomberbaz]

On 16/05/2020 at 17:06, jetstream said:

Sadly enough any filter cannot increase contrast on galaxies, the bright sky reduces one of the 2 main components of actual contrast. Observing from extremely light polluted skies are the realm of NV IMHO, their primary use- again IMHO.

There are a lot of reports that some types galaxies depending on brightness/orientation/light emission/other do benefit from certain lightpass filters but given nearly all of the said reports indicate such results are very subtle, limited too mainly brighter galaxies (The Leo triplet hamburger probably won't benefit that much)  then I don't think shelling out the best part of £200 for a 2" version is worth it. 

So I think that the generally accepted way of increasing contrast by using more magnification is a better, more consistent and lower costing option going forward.

Steve

[jetstream]

3 hours ago, bomberbaz said:

So I think that the generally accepted way of increasing contrast by using more magnification is a better, more consistent and lower costing option going forward.

Yes, for sure Steve. I tried the Baader Neo from my former town location, about mag 20- it didn't help...

[Don Pensack]

I've extensively used the GCE filter (and about 51 others) in the last few years.

I find the GCE is a very gentle filter and makes virtually no difference at all in light polluted skies.

In fact, I find the light scatter inside the filter to make the image yield lower contrast with the filter than without.

But in a very dark sky(mag.21.5mpsas), the slight improvement in contrast can be seen, though it's certainly not a great improvement.

It's interesting you mention the Astronomik CLS, as this was another filter I thought was very similar to the GCE.

However, I gave the nod to the GCE for a very subtle increase in contrast over the Astronomik.

In neither case did the filter do as much for the view of nebulae as the Baader UHC-S, which has a narrower bandwidth than the DGM or Astronomik (yet still qualifies as a broadband filter) or the Lumicon DeepSky.

I didn't really find that any filter helped the appearance of galaxies, though any nebula filter did help the visibility of H-II regions in M33.

Steve is generally right about galaxies--if you want to see them better, up the magnification, to at least 15x/inch in my recommendation.

[John]

48 minutes ago, Don Pensack said:

.... though any nebula filter did help the visibility of H-II regions in M33.

 

Yes, that is a point. Where nebulae can be seen in other galaxies a filter can help emphasize those regions.

 

[bomberbaz]

Thanks for the comment @Don Pensack, I had already decided after reading other reports that these were not worth following up on further but again you confirm that the decision is the right one.

15x per inch though, that's way higher than I had been using, I have only been in the 7-10x bracket. Seems as though I shall be using the powermate a little more going forwards.

Steve