Bug Nebula HA Widefield

[avandonk]

Waited till 4AM for cloud to clear since IR satellite map looked promising. Moon (70%) was a scorpions length away.

Used my new secret weapon an extension to the lens shade made out of a 500g coffee tin painted matte black. This limits the amount of sky the lens 'sees' to about nine degrees instead of about twenty. The sensor diagonal is 8.4 degrees.
This minimises light not contributing to the image getting into the lens. This unwanted light lowers contrast and raises recorded sky glow.

Details
Canon 5DH, Canon 300mm F2.8 at f/3.5. Astronomik 13nm HA filter.
Exposures 20 x 240s at 1600 ISO, fridge at -5.0C.

There are a couple of other nebs in the field of 7.0x4.6 degrees.

Medium image here 4MB

http://d1355990.i49.quadrahosting.com.au/2010_03/bugneb.jpg

Since the coffee tin worked so well I will go and have a beer now. Bert

[kinetic]

Lovely Bert. What a night owl! :)
Is a beer at 6:10am classed as a late night beverage?..Of course it is :)

The negative stuff you have posted lately looks brilliant.
Some of the luminosity stuff looks better as a negative if you firstly
over-do the positive histogram stretch...ie looks bad as a positve
but really good as the neg.

Steve

[multiweb]

:eyepop: Amazing contrast and the focus is spot on. So much details in that shot given the FL. Great stuff. :thumbsup:

[gregbradley]

Nothing like a bit of Aussie ingenuity.

Nicely done image. Great contrast.

Greg.

[Bassnut]

What you say about unwanted light is interesting Bert, and a neat way to avoid it. Excellent DS pic for a DSRL lens.

[avandonk]

Here are a couple of images of the coffee tin. It was very humid yesterday so I fired up the oven to 150C and cooked the tin after each coat of matte black for 30min and after the final coat for two hours. This way no paint solvents can get to your optic surfaces.

Bert

[avandonk]

Fred the Canon super telephoto lenses are not baffled to the extent of a high quality APO telescope. They were designed to take images with plenty of light compared to astrophotography.

Even though I have a degree in Physics it took me a long time to appreciate this. DOH! The first stage was an aperture in front of the lens to minimise unwanted light. Even though these lenses are blackened inside specular and diffuse reflection of off axis light inside the lens lowers contrast and raises recorded sky glow.

In the case of a narrow band filter data aquisition you think you are immune to this problem. Far from it especially when the Moon is around.

Really narrow band filters are not as prone to this problem. It is still good practice to eliminate any noise at their source if possible. I have to use 13nm due to the lens being set up at f/3.5.

All of science is about signal to noise ratio. If you can eliminate noise simply from a system before you collect signal it can only improve your final signal.

Bert

[jase]

Pumping them out Bert. Was surprised it cleared as well squeezing a few hours worth in. Nice work on the Ha wide field, plenty of nebulosity to get lost in. Keep them coming.

[tornado33]

Nice shot, the negative really shows it off. Im using a long black foam dewshield for "the lens", but I didnt think of it helping out as a light shield too, that, and the external aperature stop idia you put me onto are great, and as you say these lenses were intended for mainly daytime work with lots of light.
Scott

[marco]

Nice shot, I love these wide field view of the milky way! Interesting post about reflections too.

Clear Skies
Marco

[TrevorW]

Are you going to do colour Bert

Cheers