Bits of the LMC

avandonk · #1 31-12-2011, 08:51 AM

I have been trying since September to do a deep mosaic of the LMC. The weather has been cloudy when the Moon was out of the way.

Last Thursday I managed to get one frame with the LMC at the zenith so light pollution is is minimised.

Details.
Camera Canon 5DH, Canon 300mm F2.8L at f/3.6, ISO 1600, fridge at -12C.
Exposures 20X(15s, 30s, 60s, 120s and 240s). Usual HDR method.

This may be the last image with the Canon setup.

The dust in the LMC is the clearest I have ever managed to image. It is usually hidden in the light pollution and or haze. With all the rain we have had the air is very clear for late December.

Cropped full frame 6 x 4 degrees FoV. 6MB

http://d1355990.i49.quadrahosting.co...11_12/LMC1.jpg

A crop to the field of view of the new setup ie 3.5 x 3.5 degrees. 7 MB.

http://d1355990.i49.quadrahosting.co...11_12/LMC2.jpg

I am sure the continual cloudy weather in Melbourne is due to La Nina not due to very expensive astro gear purchases.

Looking forward to see what the new system is capable of. Going from 300mm to 600mm FL will give far better resolution.

Bert

multiweb (Marc) · #2 31-12-2011, 09:33 AM

Some very nice widefields of the tarantula there. Well done.

atalas · #3 31-12-2011, 11:55 AM

Very nice Bert....long time coming !

midnight (Darrin) · #4 31-12-2011, 05:31 PM

That's a mighty fine image there Bert.

I hope you don't mind me asking how do you find using ISO1600 as opposed to say ISO800? Would your cooler fridge help in this or is it more so optimising ISO to the particular camera model?

Darrin...

richardo (Rich) · #5 31-12-2011, 05:47 PM

Nice going Bert if this is the swan song for your ol' scope.

Look forward to images from your new scope.

Rich

avandonk · #6 01-01-2012, 08:30 AM

Thanks for the comments Mark, Louie and Rich. Producing images is pointless if they are not seen by others.

Bert

avandonk · #7 01-01-2012, 08:56 AM

Quote:

Originally Posted by midnight

That's a mighty fine image there Bert.

I hope you don't mind me asking how do you find using ISO1600 as opposed to say ISO800? Would your cooler fridge help in this or is it more so optimising ISO to the particular camera model?

Darrin...

Darrin I use 1600 ISO as it records the very dim stuff over more bits in the final raw image. This makes the faint data easier to realistically separate from the noise.
This ISO is camera dependant.

Cooling the camera to -12C really helps to keep thermal noise down. Without cooling the faint stuff is actually at or less than the thermal noise.
The read noise is the same at 1600 ISO as at 200 ISO. At 1600 ISO the dynamic range is about three stops less than at 200 ISO but my HDR method overcomes this.

There are a lot of rather technical reasons for my methods. This is only a guide as trial and error will sort out the real world performance. Dithering and stacking is the best way to minimise any noise.

Two very useful sources of information about sensors from two very smart and knowledgeable blokes.

http://www.clarkvision.com/articles/...html#low_light

http://www.brayebrookobservatory.org...CD_SENSOR.html

Note the Canon 5D is one of the best performing low light DSLRs. It can only be beaten by the Canon 5D MII IMHO.

Some camera manufacturers cheat to improve signal to noise by simply cutting out the data in the lowest four bits where all the dim stuff is. This has the effect of having very clean backgrounds devoid of faint stars and faint nebulousity!

Bert

midnight (Darrin) · #8 02-01-2012, 03:44 PM

Thanks very much Bert for your words.

That second link I found quite interesting and puts some perspective into the CCD vs CMOS argument and I am now re-assessing the equipment I own at the moment. I don't want to blow $$ on a new CCD only to find out that there is little improvement and most of my issues could be with how I am taking the original subs in the 1st place.

Thanks again Bert.

Darrin...