Things are *starting* to come together...

[dlp]

After all the advice I've been given on the forum, I decided to go out and try and get some 'decent' length exposures of M33 last night. I spent a lot of time polar aligning properly, and then a ridiculous amount of time trying to align CdC (again). Despite having tested it in the afternoon it refused point blank (pun intended) to pass a sync point to EQASCOM. Hey ho, so I did a slew to M31 and I couldn't believe my luck - there it was in the viewfinder!

So with pulse guiding enabled slewed to M33 and started taking some test focus exposures, another 15mins gone. Brudy freezing by now, glad I put the LJs on! I had to erect a flag to try and cut down the orange street light, made up of an old photographic 'Bo pole' and a cardboard box.

I took 14 exposures varying between 2 & 4 mins at ISO 1600 (wanted particularly to see what the noise was like on my new Nikon), and after a couple of gratuitous shots at Jupiter gave it best. Didn't take darks, flats or bias for this camera yet.

Spent a lot of today star aligning/merging in 3 different progs - DSS, Maxim, and PI. DSS gave a desultory result, Maxim a lot better but couldn't get a lot out of it in CS5, and then blow me down, after all the trouble I've had with PI got a half decent result. I have to add that I'd resized the 16mb raw files down to 1200 pix wide 16 bit tif and then batch converted to FIT, otherwise I'd be all week trying to get a result. I used PI to do some stretches, and used DBE although I'm not all that enamoured with it. Then spent a couple of hours in CS5. Couldn't get rid of the blue cast without killing the image, but here's the result. If anyone fancies a hack at the PI integrated image (FIT, stretched, but no DBE), it's available here. Love to see what an expert could maybe do with it!

David

[Tim]

Hmm, a tricky one for sure

Any chance of a plain stacked tiff/fit with nothing done to it at all?

The data in the red channel is pretty weak, and it seems a little odd that the strongest response was in the blue channel, not the green???

[dlp]

Thanks for looking TJ. I've put a vanilla version here.

Settings I used for stacking:

Combination:Average

Normalization:Additive

Weights:don't care

Evaluate noise ticked

Rjection:Winsorized Sigma

Normalization:Scale & zero

Sigma high:5.0

Sigma low:5.0

These may not be exactly the same as version 1, but the image looks much the same.

[lukebl]

It's looking good. Taking flats and darks will make an ENORMOUS improvement!

[Tim]

You've probably looked at this but here's the R,G and B compared from the first image. Are the raw files straight from the camera individually biased in this same manner?

[dlp]

Thanks TJ. I just had a look at the .NEFs and they seem to be exactly as your illustration.

[Tim]

It's not going to be easy to get the right colour balance with that red channel. The stars have managed to hold on to some colour, but the faint areas of the galaxy are more or less non existant, even the Ha rich areas dont show up.

Anybody else got any suggestions or used this Nikon?

[dlp]

Does it look like this camera has an aggresive IR cut? I didn't buy it really for astro photography, so please speak honestly! Is there any way I can test its response without going to a lab, or taking hundreds of DSO pics? Thinking I may get my D90 converted...

David

[dlp]

Further to above, I am wondering if light pollution is the culprit? I ask because I was looking at another post on the forum comparing different types of LP filter (here) and I noticed the unfiltered image had a very similar R-G-B histogram spread as mine. Anyone please?

PS I should certainly buy a filter anyway...

[Tim]

given the state of the original, there's definitely a LP issue

I am unsure how much you could fix it with a LP filter. Good ones are pricey, but if they work well, then worth it.

Try taking a shot of something rich in reds & ha, like M42 and see what comes of it perhaps?

[dlp]

Good advice, thanks. You masochist! 3.30am to see best from my garden.

[Tim]

yeh, but if it was clear, you'd be out anyway imaging, right?

[adamsp123]

It is funny, but I get the same blue hue to M33 when I use my canon 1000D, I know this camera has good red response on other subjects (cocoon neb) but M33 seems to defy it! I also notice quite a number,but not all, of posts of this object also show much blueness and little red.

When I used my Atik in RGB though I got red coming through..... it justs seems odd.

[Tim]

I was surprised that the big blotch of Ha that shows so well in the blue channel is barely there in the red