Southern Pleiades IC 2602 in HDR with 100ED

[avandonk]

Managed to get some data after the Moon and cloud went away at 2AM.

Canon 5DH, 100ED at f/7.65 and FL 765mm with Hutech #7887 FR/FF. Hutech LPR filter. FOV approx 3x2 degrees.

Exposures 20X(15s, 30s, 1m, 2m ) at 1600ISO. Fridge at -7.5C. Usual HDR method. Transparency and seeing both good.

Large image 8MB

http://d1355990.i49.quadrahosting.com.au/2009_12/SPleiades100ed.jpg

The small cluster to the right or South of IC 2602 is Mel101.

Some people call this the Southern Double Cluster.


Bert

[TrevorW]

HI Bert

Nice image

Any reason you went varying exposures on this I find with such even illumination across the FOV that this is not necessary myself

Cheers

[rat156]

Hi Bert,

Nice FOV, might have to try some of this widefield stuff one day...

It looks a little blue though.

Cheers
Stuart

[AlexN]

Another beautiful image Bert...

I was intending to try a HDR image one of these days, however with a mono camera I fear the workload would be too high...

Maybe once I get used to it I'll give it a fly.

[AlexN]

Bert shoots almost everything in HDR Trevor, With the limited dynamic range of a DSLR, and the unbelievable dynamic range out there in space, HDR is the way to shoot the night sky... A DSLR will saturate a bright star in 1 minute, where as the DSLR will not capture faint dust, nebulae dim stars, in 1 minute. Its a trade off normally, you either preserve stellar profiles and colours, or you get ample exposure for the nebulae and or dust in a FOV, and blow out the stars...

With HDR using a variety of different exposure durations, you are able to capture a very wide dynamic range from the very dim areas right the way through to mag -1 stars without suffering either under or over exposure...

A good example would be to shoot something like Sirius or Rigel, whilst also trying to capture all the background stars around it. you could do it with a 2 minute exposure, but the bright star would be bloated, and colourless. where as in a 15 second exposure the bright stars colour would be well defined, but the background stars would not be present...

having many different exposure durations allows a very gradual blending between the different exposures, making it seamless...

Worth experimenting, especially with a DSLR, but also with CCD's - despite their dynamic range advantage, the CCD cameras still do not capture the full dynamic range of every scene..

[TrevorW]

Thanks Alex will note

[avandonk]

Alex is quite correct. Trevor here is an M42. Exposure stacks were 15s, 30s, 1m, 2m, 4m. Focus went off but you can see how the HDR process shows from dim dust to bright stars. Even thr trap is not blown out.

I will have another go next new Moon.

Bert

[avandonk]

Here is a far better version from the same data 12MB

http://d1355990.i49.quadrahosting.com.au/2009_12/SPL100edPS.jpg

I used PS to clip the faint stuff which was mostly noise as even the noise in the 15s exposure shows up in the HDR.

Below is the four exposure stacks and the final HDR. You can see that the brightest stars are smaller in the HDR than in the longest exposure. There is far more faint stuff also.

Here is an animated gif showing a 100% crop of the same sequence. 800k

http://d1355990.i49.quadrahosting.com.au/2009_12/spl3.gif



Bert

[TrevorW]

Bert I understand the need for varying exposures with M42 have done so myself due to it's high dynamic range but didn't consider necessary for an open cluster

Cheers

[AlexN]

Whilst its not 100% necessary for most targets, it will benefit any image... M42 is a very dramatic representation of the limited dynamic range of todays camera technology, but every target will breach the dynamic range of a DSLR in a 10 minute exposure in some way shape or form, especially with a focal ratio faster than F/6...

[avandonk]

Here are line profiles of the crops. You can see the bright star has already saturated after 15s!

Bert

[StarGazing]

Nice images Bert ...... Keep up the great work.

P.S. I am getting a bit jealous of all you Astrographers :sadeyes:

Best of luck with it. Alex. :thumbsup: