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Old 04-11-2017, 12:34 PM
chuckywiz (Ben)
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Tarantula Nebula

Hi Guys,

been a while since posting on here due to work, life and what not. Heres my lil rendition of the Tarantula Nebula. Not sure if im finished yet with data aquisition but thought id have a play anyways.

Tarantula Nebula
85 x 10 minute Exposures Totalling a whopping 14 hours
20 x 10 minute Darks
Canon Eos 650D modded
Skywaytcher Ed80
Neq6pro mount
Guided subs.
Extreme light polluted back yard in Perth.

Happy for any constructive criticism as im still learning photoshop. May move to Pixinsight when then budget allows.

Ben
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Old 04-11-2017, 12:45 PM
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that_guy (Tony)
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looks like you overexposed in the core and some stars. You have excellent faint details but the core is just a white patch and the stars are colourless white circles. Tarantula is a tricky one to get the right balance between getting finer details while keeping details in the core. What iso settings did you use? If you're still adding data to this image, you could take shorter exposure/lower iso for the core only and do layer masking in photoshop to bring back some of the detail
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Old 04-11-2017, 12:50 PM
chuckywiz (Ben)
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Hi Tony

they were 800 iso. Yeh the cores pretty blownout. i dont know if this was silly or not but also saved them as fits files.. and Deep Sky stackers seem to have trouble debayering them. The colours are a bit lifeless on the stars.

Ben
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Old 04-11-2017, 04:00 PM
raymo
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Ben, I truly don't want to seem unkind, discouraging, or disparaging, but
why have you dived into the deep end with large numbers of very long subs, and using PS, when you don't have the basics of image acquisition and stacking off pat?
I suggest that you start with JPEGs, easier for beginners to work with.
Don't bother with post processing at all until you have mastered Deep
Sky Stacker, or whatever software you use for stacking.
For an object with a bright core such as M42 or 2070 you need some very
short subs as well as longer ones so you can quieten down the core in PS
or other software.
I have attached an early 2070 of mine from years ago for comparison. 5 x 90 secs ISO 1600, noise reduction enabled, so no separate darks. No post
processing, all done in Deep Sky Stacker. Your modded camera will of course show more red.This image shows the correct colours with the RGB cones synchronised in DSS with an unmodded camera. Bear in mind that this imageis 7.5 minutes, not 14 hrs. A larger scope, true, but still well under an hour on your 80mm scope. The exposures you are using are mostly utilised by advanced imagers on faint objects.
raymo
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Old 04-11-2017, 05:49 PM
chuckywiz (Ben)
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Raymo,

all advice is takin on its merit.. i dont get all sulky and run home to mumma. Im here to learn and by getting this great advice is where its at.

i did kind of get carried away with the exposures for sure. Ive started using Sequence Generator Pro and its easy to get carried away once its working.

i may re- attack this with much shorter subs and see how i go.

so softwares im using primarily are:
Sequence Generator Pro
Deep Sky Stacker
Latest Photoshop


Ben
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Old 04-11-2017, 06:49 PM
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Atmos (Colin)
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It looks like what you really need is some flats to help with the vignetting and to practice with stretching.
If you upload a raw stack we could have a look at it and see what you’re dealing with.
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Old 04-11-2017, 08:39 PM
chuckywiz (Ben)
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Hi Atmos,

Below are a couple of dropbox links. one is the raw files stacked the other is just a few of the straight of the camera shots.

https://www.dropbox.com/sh/376oqz2ax...gcE0PCpva?dl=0

https://www.dropbox.com/sh/dyf5kov65...vKGo8-Fla?dl=0

Ben
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Old 04-11-2017, 11:32 PM
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Atmos (Colin)
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Having looked at both the stacked and one of the raw subs, I’d say that their biggest problem is that they’re about 10x too long! You have a background ADU count of around 35,000 which is half of full well capacity. Doing 10 minutes exposures is really just a waste as it isn’t gaining anything over much shorter 60s exposures.
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Old 07-11-2017, 11:07 PM
chuckywiz (Ben)
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So i took some advice and bear in mind this is no darks flats or anything else.. just thought id have another crack at shorter exposures.


so this one is 74 x 60 seconds
Iso 1600
same gear as above.
i did also blow it up just to see what it loses or gains.. and focus is a smidge off.

im thinking its a nice improvement i do appreciate any advice as always but perhaps on the right track.

Ben
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Old 07-11-2017, 11:45 PM
raymo
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Ben, when learning, and experimenting, large numbers of subs are a total waste of time, when four or five subs will easily show any changes for better or worse. With bright objects such as M42, and NGC253 a single frame will suffice. When you have reached a reasonable level, and the changes become
more subtle, you will need lots of subs.
What's with the colour cast your image has? have you mastered your
stacking software? The predominant colour should be similar to the pic
I posted for your convenience, just a bit more red in it.
raymo

P.S. If the images are not bright enough with just a few subs, up the ISO to 3200 or 6400,
noise is unimportant until you get everything else right.

Last edited by raymo; 07-11-2017 at 11:59 PM. Reason: more text
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