First attempts at astrophotography with a D700

[RickS]

I have been playing around with a Nikon D700 on a Takahashi P2Z mount taking pics from inner suburban Brisbane. Here are my first (IMHO) halfway reasonable attempts at Crux and Omega Centauri.

For the Crux pic I used an 85mm prime at f/4 and for Omega I used a 300mm prime also at f/4. Camera ISO was 400. Exposures were all quite short because of light pollution and a very slack polar alignment procedure (just point it roughly south...) I did some darks and stacked everything using ImagesPlus.

I thought I'd set the bar fairly low to start with and give myself lots of room to improve ;) I have certainly learned a lot in my first couple of nights...

Cheers,
Rick.

[DavidTrap]

A great start Rick, The Crux pic is very good - the coal sack and a couple of clusters are evident.

How are you focusing the camera? Most modern lenses can go past infinity. I have seen people use a focus mask and tape the focus ring. Also, how long were the exposures. I presume you're unguided with these?

Cheers
DT

[Dennis]

An excellent set of images Rick, especially given the light polluted location and your lack of polar alignment.

I had a quick play in CS4 with your Crux shot and managed to squeeze some colour out of it.

Cheers

Dennis

[RickS]

Thanks, David. I focused manually on a bright star just looking for the tightest pinpoint. It looked best when the focus mark was right in the middle of the infinity symbol (as you said, it was possible to turn the ring past this spot). Yes, all unguided. The Crux exposures were 15 secs and the Omega ones were 5 secs. At 300mm the lack of polar alignment was obvious in longer exposures. That's my next challenge!



Thanks, Dennis. That's very cool. What did you do? I'm not really au fait with PS yet.

Cheers,
Rick.

[Dennis]

Hi Rick

In CS4 (and some earlier Photoshop versions) there are “things” called “Actions” (similar in concept to MS Office Macros) which can automate certain processing steps.

A guy called Noel Carboni has written a set of these Actions and sells them as “add ons” to Photoshop and I used a couple of these to bring out the colour.

Think of them as pre-recorded sequences of operations that can be played back with a single mouse click.

Have a look at the website for examples (http://www.prodigitalsoftware.com/Astronomy_Tools_For_Full_Version.ht ml).

Cheers

Dennis

[DavidTrap]

Try a focusing mask. Take a 10 sec exposure at high ISO and zoom in to evaluate. It's amazing how far off you can be by just going for the "smallest" star.

Just my 2c worth

DT

[RickS]

Thanks, Dennis. They look interesting and not too expensive. I'll give them a go!



David, I'll give that a go too. There's a fuzzy area where I can't tell if a small turn of the focus ring is making things better or not. A more objective measure would be a big help.

I also have an IDAS LPS filter that arrived in the mail a couple of days ago. I'm hoping that will help with longer exposures once I get polar alignment sorted out.

Cheers,
Rick.

[bmitchell82]

Nice work there mate. its good when you start getting things sorted out. Keep up the good work and you will be amazed at how far you come in a small amount of time.

[leon]

Wow, first attempt,great stuff mate, keep at it.


Leon

[j.w.white]

Rick - those are very nice images! I'm sure you'll come to appreciate the wide field and nice color the D700 provides. To add to what DT has said, I'd use some other, more reliable, way to focus. It's real easy to make yourself a Bahtinov mask (http://astrojargon.net/MaskGen.aspx) that, when using live view zoomed in, will take all of the guess work out of it. Actually, the live view is one of the things that makes the D700 such a good astrocam. That and the low noise (you can bump your ISO up to 800 will little to no impact at those short exposures - easily cleaned up with darks or in-camera Long Exposure Noise Reduction {which doubles your exposure time just so you know}). As for polar alignment - again, with live view that's pretty easy to achieve. There are many methods, two of which involve different approaches. The first involves a long exposure with tracking turned off (http://www.astrophotoinsight.com/node/568). There are a lot of folks out there who like that method (I never quite got the hang of it though). The second (and probably most popular) is the drift alignment method. Lots of different flavors of this one, but using live view through ImagesPlus it's easy enough to do (http://www.petesastrophotography.com/index.html?mainframe=http://www.petesastrophotography.com/polaralignment.html). Both the improved focusing and getting polar alignment will allow you to really put your new IDAS filter to it's best use! Good luck!

[RickS]

Thanks very much for the information and encouragement, folks. It's nice to have so many avenues for improvement to explore!

Cheers,
Rick.