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Rosette Nebula Unmodded DSLR help


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Which camera are you intending to use?

Different cameras have different IR vut filters in them so it will depend on camera and then likely a bit of a guess at the filter.

"Most" seem to pass about 20-30% of the incident Ha wavelangth, but one or two have cut off to zero before the Ha wavelength.

To collect sufficent will therefore take more or longer exposures and that will means collecting more light pollution and on a DSLR more thermal noise.

I really should learn to read - DS:R's look like Nikon's. D90 looks terrible for Ha transmission, sort of about 3%, the D5200 is not given specifically but I half think it may be a part of the D50 family in which case it may pass about 20%.

https://kolarivision.com/articles/internal-cut-filter-transmission/

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The object is most dominant in Ha, to which older DSLRs are almost blind. Later ones less so. I don't know how yours respond to Ha but one thing I do know: if you have Photoshop take the stacked and calibrated image and go to Image, Adjustments, Selective Colour, Reds, and move the top slider to the left to lower the cyans in red. That will be a big help, I think.

Olly

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Definatley possible. The Rosette is relatively 'bright' compared to many Ha emission nebulae and well within the realms of un-modified cameras.

Not sure what the Ha transmission of my 10 year old, unmodified Fuji S5 Pro is, but this is the result of a couple of 600 second subs @ ISO3200, Skywatcher ED120 scope.

37115937842_0cebff7305_o.jpg

 

Give it a try!

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2 hours ago, Gerry Casa Christiana said:

Mine is a unmodded Canon 550d one of the worst for lacking H Alpha

 

 

IMG_4229.JPG

This is a really nice image but lots of that you captured here is actually OIII as opposed to H-a hence the blue cast. I always thought of this target being quite bright in OIII but perhaps I am wrong its all relative after all. If this was a modified camera the blue parts of the image would also appear red. Either way I think that the point it that you can take an image of rosetta with an unmodified DSLR. 

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On 17/09/2017 at 19:59, ollypenrice said:

The object is most dominant in Ha, to which older DSLRs are almost blind. Later ones less so. I don't know how yours respond to Ha but one thing I do know: if you have Photoshop take the stacked and calibrated image and go to Image, Adjustments, Selective Colour, Reds, and move the top slider to the left to lower the cyans in red. That will be a big help, I think.

Olly

That's an interesting Top Tip, Olly.  I will have to give it a try.  As the owner of an unmodded Sony A6000, I am often left wondering where my nebula is.  (even after startools processing)

In the spirit of joining the party, here is my image of that area...  I was only aiming at the star cluster, so seeing the red regions magically appear was a real treat.  (36m total exposure)

33047977323_5dafceaede_b.jpg

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12 hours ago, mikey2000 said:

That's an interesting Top Tip, Olly.  I will have to give it a try.  As the owner of an unmodded Sony A6000, I am often left wondering where my nebula is.  (even after startools processing)

In the spirit of joining the party, here is my image of that area...  I was only aiming at the star cluster, so seeing the red regions magically appear was a real treat.  (36m total exposure)

33047977323_5dafceaede_b.jpg

Nothing wrong with that that more data won't sort out.

Olly

Edit. PS, if you're not using a large scale dither between subs I'd give that a go.

Edited by ollypenrice
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Olly, my camera isn't supported by any of the astro imaging apps, so I think I can't dither very easly.    I'm not sure what dither is for either.  Something to do with removing fixed pattern noise and hard-to-budge hot pixels, I think.    My pic above has quite a lot of small red pixels but I think I stretched the data to pieces on this one :-)

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On 9/21/2017 at 21:06, mikey2000 said:

Olly, my camera isn't supported by any of the astro imaging apps, so I think I can't dither very easly.    I'm not sure what dither is for either.  Something to do with removing fixed pattern noise and hard-to-budge hot pixels, I think.    My pic above has quite a lot of small red pixels but I think I stretched the data to pieces on this one :-)

At a really basic level of description dithering is done by the capture software and moves the mount a pixel or two (depending what it's been set to) in a random direction so that the image doesn't sit on things like hot pixels in the same place every frame.  It makes it easier for the stacking software to identify noise as noise and hence remove it.

Dave...

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On 9/20/2017 at 18:44, Adam J said:

If this was a modified camera the blue parts of the image would also appear red.

Are you sure of this ? I would expect to catch IR mostly in red pixels, and UV mostly in blue pixels, once the UV/IR cut filter is removed.

Also, why would the existing/visible blue signal ("blue parts of the image") suddenly leak to red pixels ? The bayer matrix is supposed to stay in place in a modded DSLR, right ?

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2 hours ago, rotatux said:

Are you sure of this ? I would expect to catch IR mostly in red pixels, and UV mostly in blue pixels, once the UV/IR cut filter is removed.

Also, why would the existing/visible blue signal ("blue parts of the image") suddenly leak to red pixels ? The bayer matrix is supposed to stay in place in a modded DSLR, right ?

I dont think you followed. What I was saying is that with the H-a sensitivity increased by modding the DSLR there colour balance of the image will shift towards the red and the blue areas (which are OIII) will be swamped by the red signal...so at best it will look a little purple in the centre. I the blue will still be there in the image just swamped by red, I did not literally mean that the blue would swap to the red pixels that is not possible. 

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Yes Sorry I didn't catch you were speaking of colour balance, as dumb as I may be I thought I was following posts about sensors' capture of H-a :)

Of course, with that precision it makes sense, especially if you use automatic / manual balance based on image levels;  Still unsure it would have that shift effect when using a star-based color (B-V) calibration tool (no experience with that, though I'm currently fighting with a lens which seems to let too much red in...)

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On 9/21/2017 at 05:37, mikey2000 said:

That's an interesting Top Tip, Olly.  I will have to give it a try.  As the owner of an unmodded Sony A6000, I am often left wondering where my nebula is.  (even after startools processing)

In the spirit of joining the party, here is my image of that area...  I was only aiming at the star cluster, so seeing the red regions magically appear was a real treat.  (36m total exposure)

33047977323_5dafceaede_b.jpg

This is great! May I know what camera you were using and how long was your exposures? 

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On 9/20/2017 at 21:44, Gerry Casa Christiana said:

Mine is a unmodded Canon 550d one of the worst for lacking H Alpha

 

 

IMG_4229.JPG

This is actually nice! May I know how long were your exposures? 

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20 hours ago, lalou said:

This is great! May I know what camera you were using and how long was your exposures? 

Thanks :-)  I'm still learning and hope to better when this DSO comes around again....  On the occasion above, the moon was about 50degrees away and 10% full.  

 

I use a sony A6000 (mirrorless APS-C consumer camera).  This pic was 10 pics all at 3minutes guided using my 150PDS on EQ3 Pro mount.  I'm sure I can improve on this with more exposures

 

While I love my A6000, it isn't great at picking up the red stuff in space.   I keep thinking I need a modified camera....

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On 20/09/2017 at 23:37,  mikey2000said: 

That's an interesting Top Tip, Olly.  I will have to give it a try.  As the owner of an unmodded Sony A6000, I am often left wondering where my nebula is.  (even after startools processing)

In the spirit of joining the party, here is my image of that area...  I was only aiming at the star cluster, so seeing the red regions magically appear was a real treat.  (36m total exposure)

My first picture of the Rosette is almost identical to this but I added another 2 hours of exposures to get my better result. 

Great picture. 

Edited by Gerry Casa Christiana
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