Horsehead at UDSC

[MarkS]

Here's a preview of my latest attempt at the picture that refuses to be taken - it was taken just before dawn this morning:



Details: H-alpha modified Canon EOS 350D on Celestron C11 with F6.3 focal reducer and CLS filter to cut out the residual light pollution at Blacklands.

I did 12 ten minute exposures but only 7 were usable because of drift, flexure or mirror shift - I'm not sure which.  Ambient temperature was 2-3C which suits the DSLR well but the seeing was not very good.

Here is the full-frame image 3x3 binned but with no darks or flats applied yet:
http://gallery.orpington-astronomy.org.uk/albums/userpics/10046/horse18102009.jpg

Mark

[Tony G]

Mark,

Excellent image, and worth staying up for, in weather that would freeze the balls off a brass monkey.
When I made a brief appearance from the tent this morning at 6.03am (I can read the stars well, now), and saw the 2 laptops still running, thoughts of Scott's trip to the Antartic flashed through my mind, and I thought I could see a frozen astronomer lifeless in the chair, so I was surprised when I called out and got a reply, and a small shadowy figure approached and said he had been up all night. Well fair play to you, and it's been worth it, I think. Congratulations.
I still think personally that weird french s**t played a big part in it. 

They are not diffraction spikes on the LHS of the image, are they? 

Tony G

[Whitters]

Very nice image Mark

[Mac]

very nice image.

Mac

[Carole]

Excellent Mark, you have huge determination, not to mention stamina to stay up all night in freezing weather to do this.

Carole

[Mike]

Really nice Mark. All that effort has paid off.

[Fay]

Well done Mark, you can stay awake when you want to!

[Daniel]

Wonderfull image Mark, can't wait to see this once the flats have been applied, you've got so much detail in there!

Can't beat late sessions!

Daniel
:O)

[Rocket Pooch]

Not bad at all   Worth the hypathermia?

or however you spell it?

[JustCruzin]

Just so that I look intelligent....

It is actually hypOthermia!

I'm real jealous- great imaging!

[RobertM]

Whatever the spelling, that's a very good result.

But Mark what is it with you and Alnitak ? is that star forever destined to be your nemesis !

[MarkS]

Here is version 2:
http://www.markshelley.co.uk/webdisk/horse18102009v2.jpg

I've applied darks & flats. I've only 2x2 binned this (instead of 3x3) because the image can almost take it.  Still a bit of vignetting in the corners and still a amp glow splodge in the bottom right.  The amp glow is because I took the darks at a different temperature but I think I can adjust the flats to compensate for this (in version 3!).

The diffraction spikes from Alnitak are very annoying but I don't want to surgically remove them.

Mark

[Daniel]

Mark, that's looking excellent! I've been waiting for you to post a version of this with flats and darks applied and it hasn't dissapointed.

Every image you post makes me start to re-think my position on buying a CCD camera next year!

Shame about the diffractions spikes, Might be worth doing a mosaic with the flame and getting Alnitak in there to give the spikes context.

Daniel
:O)

[Rocket Pooch]

Hi,

Alnitak has a very special thing going on, it actually has lines comming across it in blue, John and I noticed it in Les Granges last year.  Don't confude these with diffraction spikes err Spagetti Hoops.

Chris

[MarkS]

Thanks everyone for your positive comments.  I'm certainly very pleased with what the DSLR achieved on this one.

I think there are 3 possible factors that gave improvements over my previous attempts at the Horsehead:
1) As an experiment, I used a CLS filter even though the sky was already relatively dark.  This reduced background noise still further.
2) The cold night reduced the thermal noise.
3) I used 10 minute subs instead of 5 minute. Long exposures make sense when the background+thermal noise combined is low.

I will analyse the data in more detail.

But next time I want really excellent seeing as well!

Mark