Captured the Helix this week over 2 clear nights using my new Antlia ALPT Dual band ( Golden ) filter for the first time.
Bortle 7/8 Sydney skies
6” f6 Bintel GSO newt
EQ6-R pro mount
ZWO 2600MC cooled to -10C , Gain 100
TS Optics GPU coma corrector
ZWO filter drawer
115 x 3 minute dithered guided subs
40 x Flats
60 x Bias
PHD2 Multistar guiding ( 0.50 to 0.60 arc sec total )
Stacked in DSS
Processed in Startools V1.8 Compose Linear OSC Bi Colour
In hindsight I should have gone with shorter subs ( 90 to 120sec ) and more of them to reduce the LP noise floor but Startools did a good job in processing
The real test for the filter will be an emission nebula with a dense Star field , but so far it looks promising
I’ve just bought the same filter. It certainly does look promising. It will be good to see what you can achieve on an emission neb with it. As for the star field I think such tight band passes are going to force our hands even more into separate RGB stars to achieve a nice composition.
Very nice work. It's a tough target, especially as it's so faint and that means you can blow stars out a bit easier. I can't remember if it's possible in StarTools to merge an RGB star layer with your nebulosity image.
The filter looks promising. Looking forward to seeing your tests with it on bright stars to see if there are any halos. The L-Extreme certainly could give that problem.
Hi Martin - congrats on first light with the Antlia!
That's a very fine image with great colours & star profiles.
Unfortunately it's just so faint that 20+ hours of exposure under dark skies seems to be required to really capture the faint, outer shells.
Hope you're happy with the results of the filter so far - I'm pleased with mine.
Nice job Martin- glad to see the new filters going well for you. You’re right, I think it will really shine with emission nebula targets. Can’t wait to see what you can do with it!!
I thought you would need to extend your sub lengths to account for the narrower band pass, but if I understand correctly, once you exceed the Lp noise floor with longer sub lengths you don’t get a noisier image, it’s just that you don’t get greater snr. But I could be wrong…
I’ve just bought the same filter. It certainly does look promising. It will be good to see what you can achieve on an emission neb with it. As for the star field I think such tight band passes are going to force our hands even more into separate RGB stars to achieve a nice composition.
Cheers
Ryan
Thanks Ryan
Yes appropriate colour for Star fields is ever so difficult with OSC narrowband filters , however I’ve been reading up on the NB Accent module in Startools and it looks like it has a solution
Very nice work. It's a tough target, especially as it's so faint and that means you can blow stars out a bit easier. I can't remember if it's possible in StarTools to merge an RGB star layer with your nebulosity image.
The filter looks promising. Looking forward to seeing your tests with it on bright stars to see if there are any halos. The L-Extreme certainly could give that problem.
Thanks Adam
Yes Startools has the NB Accent module which allows you to either add Ha to galaxies and on the reverse side add RGB stars to Emission nebula
Bit more work in the capture but the module does all the hard work behind the scenes
Hi Martin, I like it mate. Just wondering why no diffraction spikes . Is this to do with the filter or the processing?
Cheers, Richard
Thanks Richard
Lack of spikes is not entirely caused by the filter, although it would have some affect
Also my scope is at f6 so not entirely fast to resolve those little stars
Helix is located in no man’s land , not too many larger stars around so my 6” newt at 900mm fl can’t resolve those tiny stars to show the spikes ( their probably buried in the background pixels some where. On the original frame version you can see a larger star at the top with spikes ( probably the only one )
Hi Martin - congrats on first light with the Antlia!
That's a very fine image with great colours & star profiles.
Unfortunately it's just so faint that 20+ hours of exposure under dark skies seems to be required to really capture the faint, outer shells.
Hope you're happy with the results of the filter so far - I'm pleased with mine.
Thanks Pete,
Yeh not fussed on capturing 20 to 30 hours on one object , I would have to wait 2 months or more to score some clear nights and by then the object is to low in the west
Still happy what can be achieved with 5 or 6 hours under heavy LP and a little old $200 newt
Nice job Martin- glad to see the new filters going well for you. You’re right, I think it will really shine with emission nebula targets. Can’t wait to see what you can do with it!!
I thought you would need to extend your sub lengths to account for the narrower band pass, but if I understand correctly, once you exceed the Lp noise floor with longer sub lengths you don’t get a noisier image, it’s just that you don’t get greater snr. But I could be wrong…
Thanks Dave
Yeh I’m sure the Antlia will do a better job than the L Extreme on emission nebula
Under darker skies the longer exposures with the OSC NB filter work better with SNR compared to shorter subs with same integration time , but under Bortle 7/8 my experience is shorter and more of them. I was going to run 2 min but changed my mind last minute. We always get the urge to push longer subs don’t we
Great job and the Antlia filter looks the goods. I've just preordered the optolong L-ultimate and at 3nm it supposedly has no halos and we will see what the final images will give out.
Great job and the Antlia filter looks the goods. I've just preordered the optolong L-ultimate and at 3nm it supposedly has no halos and we will see what the final images will give out.
Thanks Nik,
One thing I did notice , the heavy LP gradient was evenly spread across the image after a quick Autostretch which made dealing with it much more successful.No matter the tight bandpass on Ha and Oiii , you still get hammered by gradient under Bortle 8.
Yeh I decided to buy the Antlia and not wait for the L Ultimate as it’s been tried and tested for at least 6 months or more
Both are suppose to greatly reduce halo around stars , however I don’t mind a little bit of halo , makes the image more realistic I suppose
Great capture Martin...one of the best on here so far!! Just love this filter, bought it myself and has pulled out some really good images so far!!
Many thanks Paul,
Don’t know about being one of the best but it’s certainly a struggle using a OSC under heavy LP and yes the new Antlia filter performs just as advertised
The real test will be imaging a brighter nebula with a variable Star field
Thanks All
Decided to re process the Helix as most times you often find a little bit more detail using different parameters
Startools V1.8 again
Used Bin 40% to slightly improve SNR ( originally Bin 60% ) but at the expense of some loss in resolution
Allowed me to stretch the image a bit more and expose more of the eye brow without introducing too much noise across the image
Bumped up HDR reveal from 30 to 40
SV Decon only 6x iterations
Similar colour
De Noise from 5 pixels to 6 pixels
