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Dec

Help modded DSLR image of Rosette Nebula? What's going wrong?

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Hi,

I would really appreciate some feedback/advice on the following.

A few nights ago I took 45 x 300s subs of the Rosette Nebula at ISO800 with a modded 700d Canon DSLR through a Altair Wave ED80. I've stacked the image with 30 darks, 30 bias, no flats (I have a plano which, apart from the extreme edges seems to handle any vignetting) and had a go at processing in photoshop.

I live between Leeds & Wakefield so skies are very light polluted but tried to reduce the effects by using a Hutech IDAS LP filter. I started image capture about 9pm so the Rosette Nebula was relatively low in the sky although some captures were taken much later when it has well above the horizon.

After stacking I had some data but a lot less than I was expecting and really struggled to bring out any detail on Photoshop.

The questions I have are:

1) Is the level of data I have (see screenshot of DSS) typical for this amount of subs? (I have spread the channels out so you can see the data for each. I've aligned each before processing. 

2) Should I have used a higher ISO say 1600?

3) Would changing DSS settings make any difference. I use standard mode, Average for Lights & Darks, median for Bias.

4) Is the fact that I'm in a high LP area significantly affecting the quality of the images.

 

There are some fantastic DSLR images of the Rosette nebula on this forum, so I think I should probably be getting better results.

I am relatively new to AP so apologies in advance for all the questions.DSS.Rosette.jpg

Thanks Dec.

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Looking at your helpful screengrab, try moving the green and red channels so that they align with the blue (using the middle triangle on the sliders), you should see something at that point. You will probably also need to adjust the saturation (try about 20% perhaps) to see any colour. After stacking with DSS it's normal to have to adjust the histogram to get something sensible looking.

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That looks fine to me.  Now save the file as a tiff and import this into Photoshop (or other image processing software that has a non-linear stretch function (aka 'curves').  Do a few iterations of curves and the Rosette should magically appear.

I would suggest you get hold of a copy of the book 'Making Every Photon Count' by our own Steve Richards, this will help. There are also some useful stickies in the imaging processing forum.

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Thanks guys.

Victor - I've tried uploading the tif file directly but not working. I'll try sharing via drop box or google drive shortly.

 

KoCS - thanks for advice re stacking. I'll give that a go. One question, when they are aligned, where on the histogram is the best place to move them. I've always put them to the bottom of curve on the LHS?

 

Michael - thanks for advice re curves. As it happens I have a copy of making every photon count, it's a fantastic book. I'll have another read through the processing section.

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5 minutes ago, Dec said:

One question, when they are aligned, where on the histogram is the best place to move them. I've always put them to the bottom of curve on the LHS?

I think that's about right - you can then move the mid-tone luminance sliders a small amount to get a decent looking image on the screen.

NigelM

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43 minutes ago, dph1nm said:

I think that's about right - you can then move the mid-tone luminance sliders a small amount to get a decent looking image on the screen.

NigelM

Thanks Nigel, I haven't tried adjusting the luminance sliders before so I'll have a go at that.

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3 hours ago, Victor Boesen said:

Can you attach the stacked file? then i could have a go at processing.

Hi Victor, here is the link to the stacked file. Hopefully you can access it. Very interested to see what you guys can do with it as I'm very much a novice when it comes  to processing.

https://drive.google.com/open?id=0ByowQ-bs_TbIMVI3MUxPQk5FamM

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just gave it a go, but somehow i can't export it, but here it is. I tried not to overprocess it to much.

rosette.png

I am NOT the best at processing and i know that a lot of other guys on this forum can do better. I tried to make a false luminance layer but because i couldn't export from lightroom, that didn't happen.
But here it is!

Victor Boesen

Edited by Victor Boesen

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Thanks Victor, you've managed to get more detail from the data than I have done.

I read a bit on here about false luminance layers but don't have the first idea on how to create one.

 

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Thanks all for the advice/tips. I've had another go at stacking and processing the data. 

Managed to get lots more detail. Probably a bit heavy handed with the colour saturation but an improvement on my previous attempt.

Dec 

2016.rosette.embed3.pss1.jpg

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Maybe a touch to over saturated but it looks like you're looking into a red rose in space.

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Cheers Ken, yeah definitely over-saturated. Going to try and tone it down a bit and get a better colour balance.

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I spent a few minutes on it, there's definitely data there. You could do with taking some flats as there are a few gradients as well as some dust bunnies. Removing the gradients was tricky and I have done a rubbish job of it!

I can't comment on DSS too much however since I no longer use it (haven't done for years) so I used PixInsight and PS6.

In answer to some of your questions, DSS generates a fairly dark image and it needs to be processed. The TIFF image you supplied is seems fine. If you align the colour channels as well as you can and apply a decent curve then that is as much as I would do in DSS, I wouldn't bother fiddling around too much as DSS it isn't very good in that respect. Regarding ISO, as long as the histogram on the back of the camera isn't scrunched up on the left-hand side or the stars aren't totally over exposed you should be in the ballpark. LP in Leeds definitely affects any imaging other than planetary and lunar so don't expect too much but the LP filter you are using is as good as you will get. It is still possible to get some decent images in a LP area, but it just takes longer.

There's definitely more data in the image you provided, some flats would really help I think (as well as more data).

_2016_rosette_embed_DBE.png

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1 hour ago, StuartJPP said:

I spent a few minutes on it, there's definitely data there. You could do with taking some flats as there are a few gradients as well as some dust bunnies. Removing the gradients was tricky and I have done a rubbish job of it!

I can't comment on DSS too much however since I no longer use it (haven't done for years) so I used PixInsight and PS6.

In answer to some of your questions, DSS generates a fairly dark image and it needs to be processed. The TIFF image you supplied is seems fine. If you align the colour channels as well as you can and apply a decent curve then that is as much as I would do in DSS, I wouldn't bother fiddling around too much as DSS it isn't very good in that respect. Regarding ISO, as long as the histogram on the back of the camera isn't scrunched up on the left-hand side or the stars aren't totally over exposed you should be in the ballpark. LP in Leeds definitely affects any imaging other than planetary and lunar so don't expect too much but the LP filter you are using is as good as you will get. It is still possible to get some decent images in a LP area, but it just takes longer.

There's definitely more data in the image you provided, some flats would really help I think (as well as more data).

_2016_rosette_embed_DBE.png

Thanks Stuart, you've done an amazing job with the data and thanks for the advice. Next opportunity I get I'll have another go this time with flats. 

I'm pushing my luck here but could you give me an idea of the processing stages you went through.

I never imagined that much detail was achievable.

Thanks

 

Dec

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Hi Dec,

Quite a few steps, not paid too much attention to them though, but luckily still open and in the history. First cropped in PI then in the image you can see the flow for DBE and initial stretching. Then off into PS where I split the image into RGB and Luminance using DSLR-LLRGB type processing.

http://www.astronomersdoitinthedark.com/dslr_llrgb_tutorial.php

Hope that helps...

_2016_rosette_embed_DBE_steps.png

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Thanks Stuart, that's a great help and much appreciated. I'll have a look at that over the weekend and have another go at processing.

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