My first M27 -DSLR

[Roy Batty]

Clear conditions last night in somerset (well at least my bit ) helped alot, plus M27 was always just ahead of the rising moon glow - So I got a good 100 mins of subs which after checking was wittled down to about 70 mins in total for the stack.

Here's the detail: Prime focus, DSLR, unguided, 69 X 1min subs, ISO800. Processed with PixInsight LE, PS CS3 & Noiseware.

cheers

RB

M27 - Dumbbell Nebula 22 July 2008

(click to enlarge)

[narrowbandpaul]

nice lookin pic, but there is an absence of Ha due to the low response of the IR block canon and other manufacturers install.

I would consider getting it modded by astronomiser, you increase QE around 5x in Ha, and extend the response curve to >760nm, which will work well on continuous spectrum objects like galaxies. Another advantage of longer wavelengths is that longer wavelengths are less affected by seeing, so images are sharper, assuming the resolution is less than the seeing

DSLR's make a good choice for planetary nebula because they are illuminated by a hot star, and so have quite a few emission lines in the blue, which the DSLR can pick up well.

Its a great thing to take loads of subs like you have done. It gives a lot of scope for processing.

A modded camera with the same exposure as the one just taken would look fantastic

A great result never the less

keep up the good work

Paul

[Sam]

Absolutely brilliant Roy. I did a similar shot not too long ago with a lot less subs and a correspondingly less impressive result that your shot - well done!!

[barkis]

I think it suffices to say you have a very nice clear result there Roy, The stars are very sharp, the whole field is full of clarity, and all in all a very attractive Image.

Ron.

[steppenwolf]

Its a very nice image indeed, Roy - well taken and processed

[Roy Batty]

Thanks for the comments guys.

Paul - I do use the camera for non-astro stuff as well, I know a modded DSLR's WB can be re-corrected with the addition of a filter - but TBH i'd probably go for a dedicated astro CCD instead.

I've added a cropped detail image below..

cheers

RB

(click to enlarge)

[MikeD]

Great job Roy.

Mike.

[narrowbandpaul]

yup a CCD makes lots more sense, but the mod is £100, not £1000 that you would pay for a CCD

I dont know why Im arguing, I dont like DSLR's much for astrophotography

Bring on the CCD

Paul

[ngc2403]

nice image Roy,

i am suprised how much data was there with just 1min subs, like paul said i think that you need a touch more red or Ha in the image, try splitting the image into red blue and green and increase the red a little more see how it works out.

ally

[Beyond_Vision]

Very nice image Roy :salute:

Regards

Kevin

I dont know why Im arguing, I dont like DSLR's much for astrophotography

Bring on the CCD

Paul

Hmmm thats a bit narrow minded

[lunator]

Roy

It's an excellent pic

The detail in the cropped is fantastic.

Cheers

Ian

[Roy Batty]

yup a CCD makes lots more sense, but the mod is £100, not £1000 that you would pay for a CCD

I dont know why Im arguing, I dont like DSLR's much for astrophotography

Bring on the CCD

Paul

Whooooa easy now ...i'd set my sights far more modestly on something like and Atik 16ic-s or QHY6Pro, but anyway enough pipedreaming.... I've yet to pay for an ED80 on order.

cheers

RB

[Ant]

I dont like DSLR's much for astrophotography

Paul

Unfortunately that's the only way many people can afford / justify the outlay. We're not all lucky enough to be able to spend a thousand pounds + on something that gets used a few times a year!

Ant

[ngc2403]

hello all,

lust thought i would let you know of a interesting idea that i can across today while imaging the solar spectrum.

DSLR's are ~ 24time less effective at picking up Hydrogen alpha than hydrogen beta!

so back to the topic at the start for unmodded DSLR's it would be better to image using a set of filters including a Hbeta filter but NO Hydrogen Alpha!!!! i know that this will shock you but it is true that the hbeta line is 30% less likely to emit than the Ha so even with this taken into account it is brighter to the camera.

please please please can someone set this to be a task of finding the ratio of the intensities of hydrogen lines in nebula and other objects :salute:

ally

[narrowbandpaul]

i was arguing with myself, by the way, not u guys!

as a DSLR and CCD user, i certainly prefer CCD's. The main reason for this is the QE curve of the DSLR. As u know the maunfacturers of the SLR's place an IR filter to help colour balance. This filters impinges heavily on the Ha response. The efficiency gets dropped to around 5%, ie 1 in 20 photons recorded. In S[iI] the efficiency is only 3 or 4%, ie 1 in 33 photons. This is very low. Especially considering how all emission nebula show strong emission in Ha. It is the most important transition in astronomy.

On SBIG's website they have compared a single shot color CCD versus unmodded DSLR. see the ST 4000XCM

It shows that the SSC CCD is much more efficient at Ha than the DSLR. Plus the peak red response for an SLR comes at the Sodium D lines at 589nm.

There is a better link to christian buil site here...

http://astrosurf.com/buil/d70v10d/spectro3.gif

I didnt mean to offend, just offer my opinion

Paul

[Jeff RV]

Congrats on your first M27 Roy, nice image.

Jeff.

[Sam]

i was arguing with myself, by the way, not u guys!

as a DSLR and CCD user, i certainly prefer CCD's. The main reason for this is the QE curve of the DSLR. As u know the maunfacturers of the SLR's place an IR filter to help colour balance. This filters impinges heavily on the Ha response. The efficiency gets dropped to around 5%, ie 1 in 20 photons recorded. In S[iI] the efficiency is only 3 or 4%, ie 1 in 33 photons. This is very low. Especially considering how all emission nebula show strong emission in Ha. It is the most important transition in astronomy.

On SBIG's website they have compared a single shot color CCD versus unmodded DSLR. see the ST 4000XCM

It shows that the SSC CCD is much more efficient at Ha than the DSLR. Plus the peak red response for an SLR comes at the Sodium D lines at 589nm.

There is a better link to christian buil site here...

http://astrosurf.com/buil/d70v10d/spectro3.gif

I didnt mean to offend, just offer my opinion

Paul

Paul,

What you are saying is correct but, and I'm only speaking (writing) from my own point of view, modding a DSLR is expensive, buying a ccd camera is expensive, buying filters for narrowband imaging is expensive. I cannot afford to mod my camera and I'm nor sure I want to as I use it for day time photography as well. I am happy imaging in "natural" colours at the moment as I'm learning about processing and guiding etc - your enthusiasm for narrowband imaging is commendable but remember it's not the only approach to imaging.

Sam

[Roy Batty]

Aaaaaaanyway.....back to the pics guys

I've upped the red channel levels here as suggested and just a hint more in the green - I think it has bightened the DSO just a tad as a result. I've also layered in a detail crop to the main image for ease of viewing.

cheers

RB

(click to enlarge)

[SteelRat]

That's a belter of a Dumbbell Roy 8) Good stuff as per.

[narrowbandpaul]

i didnt mention narrowband, I was simply putting a point of view forward that the image could do with more Ha, and I was explaining how do this.

Allys tip for upping the red channel worked great Roy.

Theres much more red now.

Perhaps I was wrong

Keep up the good work

Paul

[Paxo]

Excellent image Roy. M27 seems to be one of those objects which is at home in both widefield and close up, and this relatively widefield shot hits the mark.

Steve..

[RobH]

A very fine image Roy, very tight and with great depth due to the amount of subs you've used :wave:

I actually prefer your first image. True, the Ha is a little low but this doesn't detract from a very good image. To my eye, although you've brought out the red more in the later image, it looks a little less natural....splitting hairs here though!!!

Cheers

Rob

[Roy Batty]

Rob - yep, I know what you mean - my first image is probably closer to a "natural" visual look than the other ones. I think that by upping the red channel levels it may give an appearance of being artificially too bright .

As always it's balancing act

RB

[RichieJarvis]

Thats a beautiful M27, whichever way you cut it Roy - good job....

[ngc2403]

i know what you mean about the image looking unnatural now that you have upped the red channel but the Ha detail or should i say Hydrogen detail is not show in the first due to the poor responce of the DSLR's to red. i know i use one myself. i like to up the red before i do any processing to the image, levels,curves etc however the light pollution has to be removed first though.

i think the bottom line is that some people like the way thing come off the camera's and other like the idea off pushing for the maximum detail. case and point my favourite images are the one that show detail that you never know was there.

does the dumbell have a halo of Ha around it like the ring?

hmmm anyway nice image Roy i can only hope for the same when i get out with my scope for it's first imaging season since i got it due to the :D :D :clouds1: :clouds1: :clouds1:

clear skies

ally