NCC6520 & Barnard 86

[PRejto (Peter)]

The sky parted on Sunday, 11 September and I finally managed - after a very long absence - to grab 1 hour of data. Well, 2 hours since I used both scopes!

NGC6520 and Barnard 86 ("cosmic Gecko") lie about 5,200 light years away in Sagittarius. The cloud of dust most likely gave birth to the giant blue stars of NGC6520.

This is my first attempt at this type of object. More data would obviously have been better but living in Sydney we are all currently beggars. I was pleased to be able to get anything with only 20 min each of colour in RGB. I would have been lost in processing were it not for the generous help of Mark Adams.

details:

TEC180/Moravian G2-8300/Astronomik CLS filter: Luminance: 12 x 5 min (.88 arc-sec)

TEC140/SX Trius/Baader RGB: R G B 4 x 5 min each colour (.95 arc-sec)

Captured simultaneously running two versions of CCDSoft/Focusmax

Processed in CCDStack, Photoshop CS-5, and a bit in PixInSight. Final image resolution = .88 arc-sec


Full Size: http://www.pbase.com/prejto/image/157573957
Crop: http://www.pbase.com/image/157573964

The images look pretty decent on two of my monitors but are unsatisfactory on my ipad. The ipad seems to struggle with darker shades so the Gecko is most unsatisfactory.

Thanks for viewing!

Peter

[strongmanmike (Michael)]

Classic bi-camera action there Pete

Great stuff

Mike

[PRejto (Peter)]

Originally Posted by strongmanmike

Classic bi-camera action there Pete

Great stuff

Mike

Ha ha Mike. This is all thanks to your "innocent" suggestion that I not sell the TEC140. That was a good call but has taken a long time to get everything playing nice together!

PS Your observatory is sure looking nice!

Peter

[MrB (Simon)]

Originally Posted by PRejto

The images look pretty decent on two of my monitors but are unsatisfactory on my ipad. The ipad seems to struggle with darker shades so the Gecko is most unsatisfactory.

Yes, some of the iPads are known to have poor quality displays: http://www.displaymate.com/Tablet_ShootOut_4.htm

However, it is very nice on my v2 Nexus7!
Love the star colours.

[AstroJason (Jason)]

Nice shot Peter. I really like the inky blackness of B86. Its a real nice object visually too and one of my faves to look at. It appears as though someone has punched a hole in the milky way in the eye piece. BTW it looks good on my laptop screen. Nice colours mate.

[gregbradley]

Great to see an image from this high end setup. Congrats! Getting both scopes to see the same object at the same time must have been very hard.

Looks good except the blue halos on the bright stars. I wonder what caused that - needed a refocus on the blue subs? The Trius can bloat a bit on bright stars with some setups. Perhaps extra decon on blue and ensure focus is redone on blue.

Also TEC180 achieves thermal equilibrium in my experience after about 1 hour so a refocus after the first hour is essential then it tends to be stable all night.

Greg.

[multiweb (Marc)]

Nice close up. That thing looks like a dust bunny in my wide fields.

[PRejto (Peter)]

Originally Posted by gregbradley

Great to see an image from this high end setup. Congrats! Getting both scopes to see the same object at the same time must have been very hard.

Looks good except the blue halos on the bright stars. I wonder what caused that - needed a refocus on the blue subs? The Trius can bloat a bit on bright stars with some setups. Perhaps extra decon on blue and ensure focus is redone on blue.

Also TEC180 achieves thermal equilibrium in my experience after about 1 hour so a refocus after the first hour is essential then it tends to be stable all night.

Greg.

Hi Greg,

Your comments are on the money. The blue halos really bother me so I think I ought to try processing again trying decon on the blue before generating the RGB. Do you ever run into issues with decon before combining messing up colour balance? My understanding is that colour balance needs to be done before any non-linear processing. Does decon count as "non-linear?" The focus seemed pretty good and I have consistent FWHM between the two scopes/cameras. But, yes, even so the stars just look a bit fatter from the Trius on the TEC140.

Getting both cameras on the subject isn't all that hard as the TEC140 is mounted on an Optec Libra (http://www.pbase.com/prejto/image/155505015).

Thanks for the tip on the TEC180 thermal stability. Yuri published some info on this just yesterday and said that the TEC180 changes 9 microns/degree C and the TEC140 33 microns/degree. That's quite a difference! Nearly 4X worse. One might speculate that the fluorite lens is making the difference.

Peter

[PRejto (Peter)]

Originally Posted by AstroJason

Nice shot Peter. I really like the inky blackness of B86. Its a real nice object visually too and one of my faves to look at. It appears as though someone has punched a hole in the milky way in the eye piece. BTW it looks good on my laptop screen. Nice colours mate.

Thanks Jason (I think!!!). I worked really hard not to have the gecko inky black! Perhaps my image is too dark on your monitor??? I tried very hard to not clip any pixels in the dark area. This was the hardest task in processing for me but I think I got there in the end. More data would really have helped. I do appreciate your writing!

Peter

[gregbradley]

Originally Posted by PRejto

Hi Greg,

Your comments are on the money. The blue halos really bother me so I think I ought to try processing again trying decon on the blue before generating the RGB. Do you ever run into issues with decon before combining messing up colour balance? My understanding is that colour balance needs to be done before any non-linear processing. Does decon count as "non-linear?" The focus seemed pretty good and I have consistent FWHM between the two scopes/cameras. But, yes, even so the stars just look a bit fatter from the Trius on the TEC140.

Decon before combining = no issue. Its a trick of the trade I learnt from Marcus Davies. If you have red halos, then decon the red to match the star sizes of the other colours - works like a treat so long as they are not too far away in size from each other.

Getting both cameras on the subject isn't all that hard as the TEC140 is mounted on an Optec Libra (http://www.pbase.com/prejto/image/155505015).

Thanks for the tip on the TEC180 thermal stability. Yuri published some info on this just yesterday and said that the TEC180 changes 9 microns/degree C and the TEC140 33 microns/degree. That's quite a difference! Nearly 4X worse. One might speculate that the fluorite lens is making the difference.

Peter

Unfortunately Peter I think you'll find its the Trius. Don't know why it flares so much on the TEC180 but it does. I am assuming it is also doing this with the 140. In my case though it wasn't just the blue. Was there high cloud when you did the blue? If not then it may be the Trius. It doesn't seem to do it with Mike's 12 inch AG or Rays 10 inch Newt but my TEC180 it was hit and miss depending on whether there were bright stars in the FOV.

Richard Crisp made a remark on the FLI site about 5 weeks ago that may be an explanation that oversampling = fat stars and undersampling = pinpoint stars. Or was it the other way round?? For example FSQ 106 images are way undersampled and you get pinpoint stars.

I am using Astrodon Gen 2 which work fine on the same scopes with my FLI cameras.

Yes I saw that post. All the fluorite scopes has really small thermal expansions compared to the ED models. The 110 fluorite was only about 5 microns and the 110ED was 45 - wow what a difference.

Greg.

[Ross G]

Nice looking photo Peter.

I like the colours and contrasts.

Ross.

[Shiraz (Ray)]

That's a lovely looking image Peter. FWIW, I didn't notice the halos until I read the posts and then had another look.

[gregbradley]

You can also use Noel Carboni actions to reduce blue/violet large halos and it will look better but tend to leave a whitish halo. You can achieve similar by toning down blues in selective colour tool although you may need to select those brighter stars and enlarge them.

There are other techniques I developed myself for my own use but they tend to be time consuming and a bit unnatural. So its better to conquer them at the equipment level. I wonder if a minus violet filter would help.

Greg.