Vela SNR in 3nm NII and OIII

[avandonk]

The Vela SNR is very faint and difficult to get good data because of the dense starfield.

NII data 10x32 minutes. OIII data 9x32 minutes.

NII to red channel, OIII to green and blue.

Large full resolution image 3.5x3.5 degrees. 9MB

http://d1355990.i49.quadrahosting.com.au/2013_01/VSNR_NOO_L.jpg

Will soon add RGB.

Bert

Astrograph is an Officina Stellare RH200 which has a focal length of 600mm and is F3, yes 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.

[ourkind]

WOW!! Stunning imaging!! Looking forward to the RGB addition.

[cybereye]

Yep, that's good. Very, very good! As an aside, why 32 minute exposures - it seems an unusual number?

Cheers,
Mario

[scopemankit]

Stunning image!

[dvj]

I can't help but think that a 3nm bandpass is not optimal for an f/3 system. Are you not seeing significant narrow-bandwidth shift at f/3? Although 3nm does isolate NII which I guess is your mission.

j

[avandonk]

John my mission is to get the highest signal to noise in a light polluted sky. I am only 16km from Melbourne. So 3nm bandwidth is the way to go.

It is a myth that 3nm NB is not optimal with fast optics of F3 say. It is based on a simplistic formula of frequency shift with angle. See Astrodons FAQ's on NB filters.

Here

http://www.astrodon.com/Orphan/astrodonfaqnarrowband/#h13


I only see about a 18% attenuation at the edges of the PL16803 with RGB and with NB. Nearly all of this is due to vignetting not frequency shift. In fact I use my NII flats for all filters LRGB and OIII, SII and Continuum. I can get away with this because I have no dust in the system. It is a pain to make flats with LRGB as the system is so fast that stars are visible in even a few seconds of twilight flats when the flat is at the linear part of the sensor.


Light pollution gradients give me far more trouble than any variation that is introduced by using a NII flat with LRGB.


Another consideration with NII is that it is only emitted by monatomic N near hot blue UV emitting stars. The vast ancient Gum nebula behind the Vela SNR seems to only emit HA. I hope to use this fact to separate the two.

I will get a 5nm HA filter as it gives twice the signal for most NII/HA emitting objects as most HA images are really 50:50 NII:HA.

My real aim with this system was to attempt to image very dim stuff out of reach of slower systems at relatively wide fields and to make large mosaics. To start making images en masse of many bright objects in a record time would be like shooting fish in a barrel. Bright objects should only be used to test the system.




Bert

[avandonk]

I still get amazed what pops out I have never seen before.



I use a program called EasyHDR and it is far easier to assign EV values if your exposures are in multiples of two in minutes.



You should see the full quality 6000x6000 215MB tiff!

Bert

[TheAstroChannel]

Wow, just amazing photography. so much detail!

[dvj]

I need AstroDon to loan me a 3nm filter to test from my urban location. Not quite ready to spend the $$$.$$ on it to be disappointed. I am smack in the middle of streetlight central from my home, and very limited to 600s exposures with the RH200 and 6nm filter. I have an old 3nm Custome Scientific filter with 50% transmission that I can run some tests. That transmission is far below Don's filter.

j

[avandonk]

You will not be disapointed. Astrodon Filters are 3mm of Striae free fused Silica. The quality in my humble opinion makes them a bargain!

I have not had gradients due to a full moon with 3nm NII and SII and HA with 480s exposures. It is noticeable with 3nm OIII.

Bert

[Ross G]

Amazing detail Bert.

Ross.