How much nebulosity can I get?

[gost]

This image of the area around Deneb that shows the North American Nebula, is an 18 minute exposure at ISO 800. How much red nebulosity can I get with an unmodified DSLR like my Nikon D300? If I were to take a 60 minute shot, would I get more nebulosity or is the cameras IR-blocking filter making it impossible to get any of the reds?

[Psychobilly]

The sensitivity at the wavelenghts of interest is really low around 20%...

I have imaged the area using a D200 on a Skwatcher Equinoxe 66 and WO FF III (Fl=320mm) over several nights using 5 min subs at ISO800... and 5min subs at ISO640. I have managed to "drag" some nebulosity out of the stacks.

Billy...

[Beyond_Vision]

You will need 1 to 2 hours of data to bring out the nebulosity. As Billy has stated the camera sensitivity to Ha is down to 20% of what it could be if the camera was modded. If you dont modify it, you will have to image upto 5 times longer.

Regards

Kevin

[steppenwolf]

I agree with all the above comments although careful processing can reveal a lot more of that nebulosity without upsetting the overall balance (I hope!).

The following image was taken with my Canon 300d (unmodified) and a 200mm telephoto lens but it took many hours of post processing to reveal the nebulosity! This image comprises of 4 X 300 second exposures at ISO 800.

[gost]

Very nice image Steve! Love the colors and the sharpness of the stars. Could you tell some of your post processing, what have you done and what software you're using?

[glennbech]

I don't want to discourage you but I'd suggest that you get the camera modified Here is a *90* second shot (f/5.5) with my modified 10D from the same "neighborhood". (North America nebula) (It is stretched quite a bit in post-processing)...

[narrowbandpaul]

the absolute qe of the camera at 656nm is around 0.05, which is very low. Modding your camera takes this value to 0.2 approx. So its well worth doing. You also extend the spectral response to around 760nm, if you dont replace the filter...just remove it entirely

[Psychobilly]

It wouldn't mod the D300 better off picking up a cheap 2nd hand Canon D350 if your going to use scopes or perhaps a Nikon D40/D50 if your going to use Nikon lenses

The Canon will give better results though... (still choke when I say that)

Billy...

[gost]

I have an old Nikon D70 that I'm thinking of modding. Maybe I should try to remove the filter myselves, it doesn't look that hard.

[Psychobilly]

which modding guide are you looking at?

http://www.astrosurf.com/~buil/d70/ircut.htm

Billy...

[Trevor]

Hi Gost

I’m just learning this DSO stuff, but by producing a layer and working on that in PS3 and using noels

tools etc this is the best I could pull out of you image.

I left it quite bright so you can get an idea.

Trev.

[steppenwolf]

Could you tell some of your post processing, what have you done and what software you're using?

First of all, I should say that there is no substitute for collecting the red data in the first place and this means buying an astro CCD or modifying a DSLR to remove the harsh (and wide!) IR filter. However, time spent post processing can yield some pretty fair results.

The processing for my image was done in PhotoShop 4.0 but the series of techniques I used to get this detail can be found in most good photo-imaging software. I use a different workflow these days as I use a different camera but the key is to make a lot of small changes in an iterative manner - gentle 'levels' increase, gentle 'saturation' increase, gentle 'colour balance' adjustment to increase red and magenta followed by a very gentle 'curves' adjustment. Then repeat the process again starting from the saturation increase point and if necessary, reduce the levels to compensate for the saturation increase.

[Beyond_Vision]

Hi Gost,

Here's NGC7000 taken with a APM TMB 105 refractor fitted with a WO 0.8x focal reducer/field flattner (F4.96) and Neodymium Filter, Unmodified Canon 400D ISO 1600, 10 x 6 min subs.

(click to enlarge)

Regards

Kevin

[gost]

Billy, I've looked at this DIY-guide: http://www.lifepixel.com/ir-tutorials/nikon-d70-digital-infrared-conversion-instructions.htm

Steve, a CCD is something I wanted for a long time, I haven't looked at any cameras yet since I have a lot of Nikon professional houses and optics. But maybe I should save up for a astro CCD since this is my biggest hobby. I've always stuck with DSLR since they have much higher resolutions and that is what some of my photo agencies require of the images that I deliver.

[gost]

Trevor, really nice job with my image. Looks like I have a lot of post production practice to do

[Tim]

I have a modded 350D and an unmodded 400D.

The difference between them is huge. I have two pics of the same DSO (M57) somewhere, I'll see if I can find them.

You can pick up a 300D or 350D really cheap on ebay, and if you are patient and good at following tutorials, and most important, able to handle intricate and fiddly items then it isn't too hard to mod it yourself. I used the Baader replacement filter for mine, else you'll need an IR filter.

Seems a shame to 'waste' excessive time on an area when we get so little clear sky anyways.

TJ

[Tim]

Here's the two images, for a direct comparison. The 350d is straight from camera, the 400D one I have equalised the channels.

[steppenwolf]

I've always stuck with DSLR since they have much higher resolutions and that is what some of my photo agencies require of the images that I deliver.

The photo agencies do seem to have some rather heavy resolution requirements and they clearly have no understanding of 'our' problems! I have a pretty large sensor astro CCD but even so, it is 'only' 6Mb so the agencies wouldn't be interested even if I was interested in supplying them!

[Tim]

I noticed a Hasselblad the other day. 50 megapixels. Heaven knows what they are taking pics of, atoms I shouldnt wonder!

[gost]

I just looked at Lifepixel.com, the price for the clear glass filter is $179.00. Anyone know of any cheaper ones?

Correct me if I'm wrong, but if I just remove the IR-cut filter and no clear glass replacement is inserted, the focal plane of the camera will change, so then I'm not able to use my Stiletto focuser that I've just ordered?

[steppenwolf]

Not sure exactly what a 'Stiletto focuser' is but your are right that the focal plane distance will change slightly as the refractive index of the filter is no longer taken into account - this in effect means that the auto-focus will not work correctly although in a recent test Psychobilly found that this was not an issue in the real world with his own camera - hopefully he will comment on this!

Calling Mr. Psychobilly, Mr. Psychobilly to the boardroom please ....

[gost]

Here's more info on the Stiletto focuser

http://www.stellar-international.com/contents/en-us/d181.html

[steppenwolf]

Thanks for the link!

[Psychobilly]

Hmmm

If your using short focal length lenses at small apertures (f15+) then the inherent DOF seems to give you a passabale image. If your using med/long focal length lenses with large apertures then you need to correct.

If you want AF to work and you want what you see through the viewfinder to match what you record onthe CCD then you need either the right thickness glass window or a replacement filter...

I was supprised the weekend when i tried the 350D with the filter removed on the "66" with WO FF III how much difference there was between the focusser settings for a sharp image in the viewfinder and a sharp image recorded on the CCD.

Billy...

Here's the thread where the focusing issue post filter removal was discussed.

http://stargazerslounge.com/index.php/topic,30320.0.html

[gost]

Now I've redone the post processing of my image I posted first in this thread. I've learned that one shouldn't do any post processing in DSS, just stack the images and save the result.

Here's the new version, what do you think?