I went to The Briars (thanks, Dave) and took some short exposure shots and stacked them.
Target: nothing in particular, just pointed up.
Camera: D80
Tripod: Velbon 250R
Lens: 18-200, set to 18mm (28mm equivalent in 35mm)
ISO: 800
Nikon in-camera Noise reduction (High setting)- no darks taken.
10 x 13s exposures untracked at f3.5
DeepSkyStacker used for registration and stacking (first go at it, so...)
Processed in Photoshop CS3
I am not that adept at Photoshop but thought I would post anyway.
small amount of trailing in the bottom left corner and perhaps the stars are a little bit out of focus? or is that an artifact of the registration and stacking...
You should try stepping up the f-number of the lens. Of course this means less light and longer exposure times...
Is 3.5 the minimum for this lens at 18mm?
At the low(est) f-setting you usually get coma - trailing of the stars in the corners towards the centre. You can see it in the bottom left and top right corners.
You should try stepping up the f-number of the lens. Of course this means less light and longer exposure times...
Is 3.5 the minimum for this lens at 18mm?
At the low(est) f-setting you usually get coma - trailing of the stars in the corners towards the centre. You can see it in the bottom left and top right corners.
I believe f/3.5 is the lowest for that lens. I am thinking of buying the Nikon 50mm f/1.8D, which I see you have. For terrestrial photography the Nikon VR 18-200mm f/3.5-5.6G lens is a great all rounder.
I based the exposure time on the formula:
t = 1000/FL (near the pole) and t = 700/FL ( near the celestial equator),
so roughly 700/28 = 25
but did not want to go as long as that just in case. Now that I see the results I could probably try again but at the smaller aperture and longer exposure.
Thanks for the tip on coma. I have read about it but until I experience something for myself I just don't get it. otherwise the image looks reasonably sharp.
I did have a go a few nights back from my (very light-polluted) backyard at f5.6 and perhaps saw a tiny bit of coma (now I know what to look for) so I could probably go back to that setting and crop.
I am not sure how to get colour into the shot- is it just a matter of longer exposure times, hence an EQ tracking mount or barn door mount? Decent polar alignment should give you unguided exposures of 30 secs on a basic RA driven mount. Using a f1.8 50mm lens should record heaps of detail and colour. these wide field milky way shots are my favourite.
I am not sure if I should shoot in RAW (or RAW+JPG, at least). Will DeepSkyStacker handle RAW images from a Nikon D80? Up to you, RAWs for best quality, JPEG for getting used to photo stacking and processing. Start off with JPEG to get the hang of DSS and PS then move on to RAWs (unless your computer has lots of grunt!? DSS will handle RAWs as I remember. A better/more advanced upgrade is ImagesPlus, it's not free though but it's a goody! They do have a free demo to try out - you have to convert RAWs to TIFF or JPEG format to work in it. Registax , although primarily for planetary AVI stacking can work with deep sky pics - once again have to convert RAWs for use in it and it's free!
Plus, my photoshop skills are a bit weak at the moment so stuff like colour correction, etc. needs to be studied and worked on a bit. Many brains to pick on IIS, but there are lots of Astrophotography tutorials for various aspects of imaging dotted around all over the web - google it!
Here's a good one for starters... http://www.astropix.com/HTML/J_DIGIT/TOC_DIG.HTM
The Levels and Curves tools are now your best friends!!
I have a ways to go but getting an image...it's quite addictive.
Lots of us know that one DJDD, too damn addictive
Hi DJDD, I find Deepskystacker actually does much better with the RAW files than anything else..well with the canon anyway.
After you let deepskystacker do its stuff and you are previewing the image, you have some settings for levels, luminance and saturation , you can bump up the saturation to 15-20%. That should give you a close to natural color saturation. remember to tick apply changes to image when you are at the save dialog box.
Hope that helps..
cheers
Probably longer exposure may help to get the colour.
Have a look at my 1st (and only good) photo of the Sagittarius star cloud made with a tripod: http://www.iceinspace.com.au/forum/s...ad.php?t=21306
50 x 10s exposures at ISO 800, 50mm f1.8 @ f3.8, the same camera as yours.
Regarding stacking RAWS, what I have noticed with Deepsky Stacker is that (Nikon) RAW files are "much darker" than JPGs, i.e. it will detect less stars in the RAW file (hence stacking goes quicker) and the resulting image will be darker. Set your camera to make RAW+JPG when taking photos and try stacking the same images in two formats and then compare the results. However, I am not sure adjusting the levels/curves afterwards will give a better image in the end with RAW.
Hi DJDD, I find Deepskystacker actually does much better with the RAW files than anything else..well with the canon anyway.
After you let deepskystacker do its stuff and you are previewing the image, you have some settings for levels, luminance and saturation , you can bump up the saturation to 15-20%. That should give you a close to natural color saturation. remember to tick apply changes to image when you are at the save dialog box.
Hope that helps..
cheers
Hi Garyh,
I plan on using RAW+JPG next time and testing both out, although without tracking I will not see much or any colour in the shots (such short exposures).
thanks for the tip on the saturation levels. It is always ahrd to decide what is realistic.
Probably longer exposure may help to get the colour.
Have a look at my 1st (and only good) photo of the Sagittarius star cloud made with a tripod: http://www.iceinspace.com.au/forum/s...ad.php?t=21306
50 x 10s exposures at ISO 800, 50mm f1.8 @ f3.8, the same camera as yours.
50 shots!
Well, I could do that if I turned off the in-camera noise reduction and used darks instead. I quite like your photo and will give more exposures a go.
I will try taking RAW+JPG next time and compare stacking of both.
Thanks for the link, as well. I read the page on curves and that will help a lot. i think I need to also get a better understanding of the theory rather than just using Photoshop as a magic box of tricks.
otherwise the image looks reasonably sharp.
,excepting the coma already mentioned.
