5.77
#...
·
·
13
likes
|
|---|
|
Hello! Yesterday I did some testing with the new Antlia ALP-T dual-narrowband filter - in fact I made a comparison with my Baader 6.5nm Ha and OIII CMOS filters. Equipment used: - Skywatcher Esprit 100 (f/5.5, 550mm focal length) with standard SW flattener - QHY600C-PH CMOS-camera (OSC) - Skywatcher EQ6-R mount and MGEN-3 autoguider - N.I.N.A. for acquisition For each filter a single 600 second exposure was made; the out-of-cam FITS-file was de-bayered in Astro Pixel Processor and stretched identically (black point at the beginning of the histogram mountain, white point at 20,000 and a Gamma of 5). I then extracted the color channels of the RGB-data and pasted them next to each other into a new greyscale file. I come to the following conclusion: - Baader Ha-filter is slightly better in contrast, but the stars of the Antlia Filter are smaller. - The amount of OIII-signal in the Antlia is considerably higher than in the Baader filter. This results in a much clearer and more contrasty impression of the Antlia RGB image compared to the Baader NB-filter images. However, this impression could be the result of choosing NGC 2244 as a test target, which has a fairly high amount of OIII emission. How the Antlia fares against the Baader filter on a true Ha-target (without OIII emission), still needs to be determined. - While I experienced very unpleasant halos with the Baader Ha-filter from mag. 5 and brighter stars, I did not see any halos when exposing 10 minutes with the Antlia on mag. 1-2 stars like Elnath or Pollux. I have posted my test shots on my Flickr page, feel free to have a look and commet your thoughts: Red channel comparison: https://www.flickr.com/photos/147135308@N08/51806200902 Green channel comparison: https://www.flickr.com/photos/147135308@N08/51807517264 Blue channel comparison: https://www.flickr.com/photos/147135308@N08/51807885130 Single 10-minute exposure of NGC2244: https://www.flickr.com/photos/147135308@N08/51805839623 CS Chris |
2.86
#...
·
·
2
likes
|
|---|
|
Thanks for the comparison and testing Chris. As someone who currently shoots with a OSC I'm excited by these new filters. I currently use a L-Enhance but I'm interested in something narrower for my emission nebula projects. I'm holding out for the moment just until we learn a bit more about Optolong's new dual 3nm L-Ultimate, although who knows how far away that is from retail. Hopefully we will start to see some comparisons and first impressions. The Antlia ALP-T is certainly looking quite promising. |
4.57
#...
·
·
1
like
|
|---|
| From the images that I have seen so far, this looks like an awesome filter! I currently use the L-eXtreme and suffer the well-known Oiii halos that it produces on the bright stars. I think I will wait to see how this dual 5nm compares with the new L-Ultimate 3nm dual filter before upgrading though. |
6.77
#...
·
|
|---|
|
Perhaps not best to compare a dual band filter vs individual HA and Oiii filters. But, either way. Glad to see that the Antlia is performing well. Quite impressed though how much more data there seems to be in the blue and green channels. It will be interesting to see it compared to the new optolong ultimate that they're planning to bring out (soon?). Either way, glad to hear the Antlia is a good quality filter. As I've just upgraded my narrowband filters from the Optolong 6.5nm set to the Antlia 3nm set. Unfortunately I haven't had my first light with them yet.. it's like the weather knows when you buy new gear. |
1.91
#...
·
·
1
like
|
|---|
| Thank you Chris for that! I am looking forward to test mine as soon as I get it, from my B8 sky. I think I’ve made a good choice 👍 |
1.91
#...
·
·
1
like
|
|---|
| Just got mine today - hope to try it this weekend on Alnitak. A bit tired of halos... |
|
1.91
#...
·
·
1
like
|
|---|
|
Here's a quick side by side comparison on the Jellyfish (integrated light frame with no processing, default STF stretch) - left side is the Altair Tri-Band, right side is the Antlia. No halo with the Antlia ... but unfortunately with my OSC (294mcp) the sensor artifact shows up. It's somewhat mitigated with flats but it's still there.   |
|
2.86
#...
·
·
1
like
|
|---|
|
Thanks Jay, hopefully my order will be with me shortly and I planned to shoot this for my first test. Just out of interest was there a moon up at all during the time you took the test shots above? |
|
1.91
#...
·
|
|---|
| Hi Danny -- thankfully no Moon around in these pics. Good luck - looking forward to your tests. |
0.90
#...
·
|
|---|
I own this Filter too but I have some terrible Halos. Any idea why ? The halo is visible in Ha and O3, see attached pictures.  |
2.15
#...
·
|
|---|
|
Hi Chris, I think you have to be careful with this type of comparison. You always get a signal of Ha in OIII using Dual Narrow Band filters and OSC. Look at the pass filters of the Bayer Matrix of the QHY. " The amount of OIII-signal in the Antlia is considerably higher than in the Baader filter" might be the result of this that you actually record some Ha in your OIII and not only OIII, hence stronger signal. |
|
5.77
#...
·
·
1
like
|
|---|
|
Rob, you are right! According to the QE/wavelength plots of the QHY268C camera (there are no such diagrams for the QHY600, but sensor specs should be identical) the sensitivity of the green pixels at the Ha-wavelength is approximately 8%. The sensitivity of the red pixels at Ha-wavelangth is 80% - so we should end up with 10% of the Ha-signal in the green pixels. To make a fair comparison, approximately 10% of the Ha-signal should be subtracted from the OIII-signal. The opposite effect (OIII-signal in the red pixels) is neglible in my opinion - the red pixels have a QE of only 2% at OIII-wavelength. Chris |
0.00
#...
·
|
|---|
Werner Stumpferl: What scope? I do have the Epsilon 160-ED (f3.3) and considering the ALP-T.... |
|
0.90
#...
·
|
|---|
| It's an 8" f/4 Newtonian with TSGPU Corrector. |
