Gee whiz.! A rich star field overlaying a complex web of nebulosity. I sense some challenging processing here in trying to contain the star field and bright stars whilst bringing out the fine details in the nebulosity. Thanks for sharing Bret.
Andy I have found for most targets that NII and HA are not much different. There are differences however as the NII seems to have more fine structure. Especially in the faint bits. I have seen differences in many but they are subtle.
There is a school of thought that there is overlap or leaking between even 3nm HA and NII filters.
The main advantage of 3nm filters is that the stars are about half the recorded flux of 5nm filters and the nebulosity is the same.
Even with 3nm filters the Moon can interfere when it is near full. It is far worse with OIII than NII.
My observatory is in Eltham with moderate light pollution so 3nm NB filters are a must. At a dark sky site 5nm are better for 'HA' as most targets are 50:50 HA and NII.
This is all about signal to noise. The fast F3 of my astrograph collects data about 2.7 times faster than F5. This means that thermal noise is down by a factor of 2.7.
A 32 minute exposure at F3 is roughly equivalent to 86 minutes at F5. The F5 image will have more noise.
If you consider the central obstruction, my optic is bit more than twice as fast as an unobstructed APO at F5 assuming it has 100% light transmission.
Very interesting and helpful as I too image under Melbourne's light polluted skies in Burwood and have been seriously considering going from 5nm filters to 3nm.
That's one fast 'scope you have at F3! Waaaay better than my F5.6 setup.
May I ask what it is that you are using?
Very interesting and helpful as I too image under Melbourne's light polluted skies in Burwood and have been seriously considering going from 5nm filters to 3nm.
That's one fast 'scope you have at F3! Waaaay better than my F5.6 setup.
May I ask what it is that you are using?
Cheers
Andy
Astrograph is an Officina Stellare RH200 which has a focal length of 600mm and is F3. Clear aperture is 200mm.
FLI Atlas Focuser.
FLI ten position filter wheel CFW-3-10 with 50mm square filters.
Astrodon E series LRGB and HA, NII, SII and OIII 3nm NB filters. Also a continuum filter 5nm.
Camera is a FLI PL16803 which has a sensor size 36.8 X 36.8 mm.
The FoV of this system is 3.5 X 3.5 degrees.
Mount is a Software Bisque PMX.
I have however, some constructive critics to share:
I think you should do a little more overlapping between the tiles, in order to minimize the optical distortion visible at the edges of each tile; some seams are visible because of this. May be you will need to crop each tile a little.
Also, I find some of the tiles with high background noise, so I recommend to add more frames to each tile...
I am currently working on the same area, but In RGB...may be I will add some OIII later to enhance the blue philaments.
I have however, some constructive critics to share:
I think you should do a little more overlapping between the tiles, in order to minimize the optical distortion visible at the edges of each tile; some seams are visible because of this. May be you will need to crop each tile a little.
Also, I find some of the tiles with high background noise, so I recommend to add more frames to each tile...
I am currently working on the same area, but In RGB...may be I will add some OIII later to enhance the blue philaments.
Geert
Geert I have only seriously reprocessed the centre four panels. here
That Looks a lot better Than the previous mosaic,
The seam is still slightly vissible at the top between the rightmost pannels, but less evident than in the prevous version and can not see the star distrotion anymore.
