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deep sky stacker jpeg?


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hi all i have a sony dsc-p100 and have been messing round with the setting and taking some pics of the sky and of the moon through my little firstscope... my question is this!.. would i be able to stack my widefield pics of the sky i can take 30 sec pics at iso 400 and set to infinity with spot metering but the camera save's in jpeg format, most things i've read say dss process large raw files .TIFF can it do jpeg aswell or should i just get a dslr?

Thanks Tim:)

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A DSLR would probably allow you to do a better job because JPEG is not an ideal format for astro-imaging, especially before processing. You may find that you can get somewhere if you convert the JPEG files to TIFF before running DSS, but it's never going to be an ideal solution.

James

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Yes you can... DSS will stack jpg's in the same way that you can use raw and tif files. I used to do this for much the same reason when I started out, my bridge camera did not support any other option. You won't have the leeway that a camera that can shoot raw provides, but it'll work, and it's all good practice.

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Thanks thats ideal! dss is on download! i guess jpeg is not ideal but i guess i can upgrade to dslr at a later date! and i will be a bit fimilarized with the program?......Hopefully! lol Thank you for your advice:) Would be lost without SGL!

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I think you'll just have to see how it goes with the JPEGs. One of the problems with JPEG is that it's a lossy compression, so you won't have really good data to start with. Another is that it's only 8-bit colour. Even exposures of several minutes can be concentrated at the darker end of the palette and the subsequent stretching of the histogram to bring out the details can end up showing up the lack of dynamic range because you end up with adjacent colour blocks that the human eye can distinguish quite easily. The compression algorithm can also mean that they have blocky edges, making them even more obvious.

It is all good practice though, as has already been said, and you have to work with what you have.

James

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I think you'll just have to see how it goes with the JPEGs. One of the problems with JPEG is that it's a lossy compression, so you won't have really good data to start with. Another is that it's only 8-bit colour. Even exposures of several minutes can be concentrated at the darker end of the palette and the subsequent stretching of the histogram to bring out the details can end up showing up the lack of dynamic range because you end up with adjacent colour blocks that the human eye can distinguish quite easily. The compression algorithm can also mean that they have blocky edges, making them even more obvious.

It is all good practice though, as has already been said, and you have to work with what you have.

James

so if i were to convert the jpeg into.TIFF would that solve the problem?

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so if i were to convert the jpeg into.TIFF would that solve the problem?

You can't recreate the data that you've already lost, so converting to TIFF won't help if DSS is happy to work with the JPEG images. If it wouldn't work with JPEG (I've never tried it) then it ought to with TIFF.

I'd stay with TIFF for as long as possible during processing though, even if you start out with JPEG. At least then you shouldn't lose any more data.

James

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so if i were to convert the jpeg into.TIFF would that solve the problem?

No, you would still be left with the quality of the original exposure albeit in a different format. You can't up-scale the quality.

Don't worry about the jpeg format for stacking they won't turn out too badly and it's all excellent practise. Be sure to post what you achieve :)

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so is it not worth converting it to .TIFF? or should i convert as dss works better with .TIFF?sorry guys but i have no backround in astronomy or photography only what i have researced on here and the net! so your input is much appreciated:)

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If DSS reads the images as JPEG and allows you to save as TIFF then I'd work with TIFF from that point onwards until you want to stick it on a website, say, at which point I'd save a copy as PNG.

James

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Stick with the jpg's, don't start converting them from the camera. Load the jpg's into DSS, stack them, then save as a tif and work on the tif from there. Once you're done, then save as a again.

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Thanks james for the advice i will have to see how it goes.. i havn't installed dss yet but will get on in soon, as the clouds seem to be clearing away here in n.devon, so it's looking promising!

Spikey i will post the results in due course.... if they are not completely rubbish!! lol

Thanks again all:) Clear Skies. Tim

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WOW that pic is amazing! do you know what camera took the pic and how many exposure's stacked to get results like that?

Timbo 32, thanks for the compliment, I think from memory it was 40-50 X 20sec exposures @ iso800 with a canon 1100d with the supplied 18-55mm lens set to 18mm
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My experience is that the kit 18-55mm lens causes the stars to stretch just as they have done in your image, especially when you have it wide open. I have a number of images taken using my 450D and the same lens with a similar effect :)

James

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That's odd. The only image I had that effect with using the 18-55is kit lens was when I shot 40x 30s exposures from a camera tripod. I believed it was an effect of field rotation, and it only affected those two corners.

Here's one, from some time ago, it was 10x30s I think at f/3.5.

jupiterinmw.jpg

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Hi all notsure if i should post this here but as we were talking about it....Anyways... i have taken all the relevent darks, flats etc and 10 30sec exposure's and stacked them, how do i get the image "small" enough!! to post the pic on here!!! its nowhere near the standard of what you guys have posted before me but maybe you guys might spot if i gone wrong or some tips!!!

jgs001 very nice picture:)

Clear Skies Tim

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Tim, Once stacked, you'll almost certainly need to edit it more... although you can use the DSS adjustments, they are quite rough and ready, and rather course in what they do, not too worry though at the moment. Once you've saved the image as a TIF from DSS, you'll need to open it in an image editor to resize etc... If you don't have anything yet, have a look at www.gimp.org (Gnu Image Manipulation Package), it's free, and will allow you to resize the image to something manageable for the web (1024 or 800 pixels on the longest side, I use 800 as that's the limit for a lot of forii).

Once you have your image ready to post, then I'd recommend starting a new thread in imaging widefield and special events and we'll take a look.

As for our pics, bear in mind, most of us are using dSLR's, shooting raw, and have had a lot of practice ;)...

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  • 4 months later...

At risk of reviving an old thread I am very curious how you guys are getting such long exposures with 18-55 kit lenses on camera tripods.

I use a Nikon D3200 with a 18-55 kit lens and anything over about 5 seconds and I get horrible star trails

if I were to attempt the 30 second exposures you guys are doing the trails come out about a quarter of a cm in length.

I set my lens at it's widest field to try and reduce the effect and I shoot at ISO 800 with my f.stop 2 clicks back from wide open

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At risk of reviving an old thread I am very curious how you guys are getting such long exposures with 18-55 kit lenses on camera tripods.

I use a Nikon D3200 with a 18-55 kit lens and anything over about 5 seconds and I get horrible star trails

if I were to attempt the 30 second exposures you guys are doing the trails come out about a quarter of a cm in length.

I set my lens at it's widest field to try and reduce the effect and I shoot at ISO 800 with my f.stop 2 clicks back from wide open

Good question , something i would like to know. 

i had a 18-55 kit lens for my canon 350D, every shot would produce stretch stars.

i found the best for the canon kit was 3 second exposure at around f4.5. 

i got rid of the 18-55 and swapped for a 50mm f1.8 II 

seen amazing wide'ish angle photos but never been able to produce them myself.

its impossible to get infinity focus without any focus window meter, you spend all night trying to get something in focus

i also do not have a live view function on my old defunct 350D so makes astro photography a right pain in the rear

i would be happy with one very nice looking shot and not having to delete pictures

full of stretched rugby ball stars, or spend 8 hrs getting the focus set and 10 seconds taking shots

(batterys die quick when your in and out of menus and the likes all the time.

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One tip - if you can, set a fixed white balance, don't leave it an auto. Otherwise you might find the jpeg flats etc are scaled differently from the lights (as jpegs always have some non-linear scaling applied in the camera).

NigelM

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At risk of reviving an old thread I am very curious how you guys are getting such long exposures with 18-55 kit lenses on camera tripods.

I use a Nikon D3200 with a 18-55 kit lens and anything over about 5 seconds and I get horrible star trails

The rule of thumb for DSLRs is 400 divides by the focal length. So for am 18mm lens you can get about 20 second exposures (400/18=22 seconds). For 55mm you can get about 7 seconds (400/55=7.3).

It also depends on where in the sky you are looking. If you are looking high up towards Polaris the stars will not move as far in 20 seconds as they would if you took a photo of something at the meridian.

Sent from my GT-N7000 using Tapatalk

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Thanks for that,

I always shoot at the widest setting for my lens but even then above 5 seconds makes trails and I can't go anywhere near the 22 seconds that formula states.

It does not seem to matter where in the sky I point it's always the same.

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