SPSP Widefield Crux

[trent_julie]

Here is our latest attempt at a wide field of Crux, taken at the South Pacific Star Party near Mudgee, NSW.

We tried to bring out the star colours and the dark dust lanes in the Milky Way near the Coalsack.

Any comments or suggestions are most welcome. We have found it fairly difficult to find a good balance between nebulosity and star brightness, so any tips on how to get the best out of this region of the sky would be appreciated!

Cheers,
Trent and Julie.

Details as follows;
Canon 1000d
Autoguided on a HEQ5 Mount
Exposure 28 x 240sec @ ISO 800
Stacked in DSS
Processed in CS3

[[1ponders]]

Wow! I like that orientation and FOV. What lens did you use? Personally I like the colour contrast you guys have achieved. The reduced version certainly shows the detail. Are you shooting in jpeg or raw?

[trent_julie]

Cheers 1 ponders,
This was all done in RAW, it went from a 57Mb file to 200k for ice in space so I guess some resolution could be lost there, however,we expected a little bit more detail from the amount of data we collected, does the detail gets lost in the sheer size, if so why does the Galactic Centre shot look so detailed ???

[[1ponders]]

It looks like you have some great data in there but your compression appear really heavy in the jpeg. How do you resize your images once you've finished working with them?

When you finish DSS to you use the autosave.tif file to open into Photoshop? Do you adjust your image in PS as a tif file? or as a jpeg?

[trent_julie]

Paul,

I have been saving the final product off DSS and then working on it in CS3 as a TIFF, I use canvas/image resize to attempt to reduce the footprint size (so its a bit more presentable on iceinspace)
Hmmm, I shall keep on at it.

Trent

[RobF]

Nice going Trent and Julie.
Great to meet you both too.

(You must have reached the end of that dinner queue to have survived to post this one :lol:)

[[1ponders]]

Ok. If I use DSS I like to use the Autosave version as its unadjusted. But that's just my preference.

In PS, when saving for upload, rather than using the method you describe, I use the Save for web and devices option under the file menu. If you've not used it, it allows you to view your original against an optimized one. You can adjust size and jpeg quality and at the same time see the final file size. I adjust my image size to around 900 wide to fit on the IIS image page and then muck around with the quality slider until the file size under the optimized image is below 200 kb. All the while keeping an eye on what the optimizer is doing to the quality of the image in the display window. If it looks too chuncky and harsh, raise the optimizer slider and reduce the image size. Works a treat

[trent_julie]

Cheers Paul,

I will give the 900 wide size a go tomorrow afternoon, thanks for your advise tonight.

Trent

[[1ponders]]

:thumbsup:

[Lester]

Nice wide field, showing a lot of varied detail, pleasing to the eye. Just over come those Jpeg compression artifacts and it will be outstanding.

What lens did you use?

[TrevorW]

Good effot well done tracking etc maybe a tad longer of exposures. I think I read somewhere a preference for a lower ISO when doing widefield

[trent_julie]

Rob,
It was good to meet you to, thankfully we survived the line, but what a star party!

Lester,
The shot was with your standard Canon 18-35mm lens at F4.6

We have come to the obvious conclusion (with the help offered here) that we needed a tad more exposure time and less ISO in future, I guess there is some noob left in us yet....

Cheers

[Satchmo]

The density of stars in the Milky Way in this shot seems quite low for 2 hours of data. The 1000D doesn't seem to have not much sensitivity for astrophotography work. Or am I missing something ?

[multiweb]

Great coal sack. Can even make out the jewelbox. Gotta love dark skies hey? :thumbsup:

[trent_julie]

I think we both maybe missing something..... the 1000d is an entry level camera, it isn't by any means top of the range, however we did have some success with the offset galactic centre shot, so I guess I expected a bit more of that nice yellow nebulousity at that length of exposure .......

widefield galactic centrelink here:
http://www.iceinspace.com.au/forum/showthread.php?t=61266

One thing is for sure is that the subs of both shots closely resemble the final product. It's obvious I've done something wrong with this effort, so I will attempt this again soon, this time ensuring I have the yellow tinge in the subs........

Thanks for the feedback Mark

[Octane]

Trent and Julie,

Did you guys take dark frames, as well as flat frames?

There is a wealth of data hidden in that image that is vying to be seen.

H

[trent_julie]

H,

This is where the noob becomes evident, no darks and no flats, I was under the impression that with internal noise rejection would deal with this, I now know that this may not be the case at all... these things will change at my next attempt, consider it lesson learned.

Trent

[[1ponders]]

ICNR is great to kick start with. It does a great job, but eventually you may want to try taking your own darks.

In the menu of your camera, do you have the parameters setting on Adobe RGB or something else?

[Octane]

Trent and Julie,

Yep, it's those little things which make a huge difference.

Paul, when shooting RAW, colour profile space is irrelevant. : )

H

[[1ponders]]

Just following the instructions in the manual :)

[trent_julie]

1ponders,
I was on sRGB, that setting is now changed to adobe, I guess that will still be helpful with the jpg (I don't use these for stacking)

H,
If i was to find out the temperature when I took these shots and redo the darks would this help? or am I pushing the expletive up hill?

Cheers,

Trent

[Octane]

Trent and Julie,

Personal opinion is no, as DSLR sensor performance varies too much.

However, give it a go and see how it turns out. Whilst you're at it, take some flats and flat darks.

If your lens and sensor were fairly clean and you can get your focal length and focus back to where you had it at the time of image capture, you may able to sort out the vignetting.

Take your flats at ISO-100. Point your camera and lens to your notebook screen, load Photoshop up and create a new document with a white background. Hit 'F' a couple of times to go into full screen mode and hit Ctrl++ a couple of times so the document fills the screen. There's your flat field! Take 15, or, so (you want an odd number of frames for the median combine algorithm to work effectively). The same rules also applies to darks and flat darks. Take a few test flats and check the histogram. You want the curve to peak somewhere between 1/3rd to halfway across the X-axis.

Hope this helps.

H

[trent_julie]

Hey Guys,

This is our final SPSP Crux, Admittedly more could of been done initial stages, but We think that this is as good as our collected data will allow us.

Same images, different stacking method in DSS (used averaged stacking and allowed DSS to do the colour balancing)

We also calibrated our Laptop screen with a device named huey, what a huge difference it has made! We recommend them to anyone

Thank's for all the comments thus far, We found them constructive, and they will be all taken heed of on our next imaging run,
Cheers,

Trent and Julie

[[1ponders]]

Noice. :thumbsup:. much better size for viewing as well. It shows quite red overall, but that certainly doesn't detract from a very nice image