Hi Guys,well last night was certainly interesting, as for the first time I had decided to continue imaging from where I had left off the night before.
I had heard that others do this on a regular bases, so why not give this a go, I thought.
Previously I had taken 20 frames of the Rosette which I posted yesterday, the mount was shut down, and all stayed as it was until last night, mind you I had never tried this before.
Anyway I fired it up again, asked Gemini to do a warm restart, meaning that it would use the previous nights information, and continue from there.
After it had done its normal pre checks it asked, "well what do you want me to do", (well not really in those terms,) so I entered in NGC 2237, as I had done the previous night, and away it went.
I was absolutely gob smacked when it landed on the exact guide star from the previous night, so I just calibrated PHD again, on that star, and it imaged the exact same spot for the rest of the night.
So this is collection of two nights imaging combined into one, 20 from the earlier run, and 17 more from last night.
The image you now see consists of, 37 sub frames @ 7 mins @ 400 ISO, with the Tak, and Modded 5D, on the G11, auto guided, flats and ICNR, and processed in Image Plus, and CS2.
The first image is with the added 17 frames, (making 37 sub frames) and the second is the one i posted with 20 frames
Please feel free to comment either way, hope it is to your liking.
Hi Leon, For an extra 2hrs worth of effort I see very little overall gain in the image. Flicking between the two images reveals a little extra detail in the outer sheath and a small gain in signal but the question you have to ask yourself is, "is it worth the extra effort?" For me the answer would have been No. Some small changes in processing may well have made the differences, who knows.
Perhaps the answer lies in the duration of the subs. Longer subs may look deeper and resolve more but you would have to weigh that up against skyglow noise and camera capture noise.
The conumdrum we all face. When is enough, enough?
I had the jpg in CS4 and there is a lot more data in it.
But a jpg this size cant be processed properly
I think that with more processing you can get a lot more out of it Leon.
Doug I tend to agree, there was a lot of effort for little gain, but it was worth the experiment for the comparison side of things, anyway I am happy with either shot, and as you said Doug, maybe longer subs, but than there is the LP and extra capture noise to consider.
(renormalised,) you really crack me up, that is so funny, I can just see myself doing that too
Anyway i thought I would give this a go, it worked, and there will be many more objects to try this procedure on.
As suggested, by some, may be it is time to look at the SBIG site or make a fridge like Bert
The second image has a gradient in it where the right hand side has a gradient to it whereas the first image does not. (gradient - background is uneven in lightness).
This is costing you contrast in the second image and is probably suppressing the data.
There is a good free tutorial on handling gradients at Wade Observatory using channels and the gradient tool in Photoshop. Or even better Gradient Xterminator by Russell Croman (free trial) makes these gradients a thing of the past.
So don't assume it wasn't worth it. Longer exposures in my experience mean less noise and easier processing. Lack of exposure severely limits your ability to extract the signal without a lot of noise.
Just as a comment you can even get gradients imaging from a dark site. A bit of cloud, the moon, a bit of glow from your laptop, headlights, your torch etc etc.
Many thanks Greg, I admit I am not the worlds best processor, much to learn, but am slowly getting there, with much help from all you good people here.
I will certainly take your suggestions on board, thank you.
Oh by the way here is my technique for adding images later on;
1. I take a focus shot of the image.
2. I open an image from the night before and size it to match the focus shot (control 1, 2 , 3 ,4 etc one of them makes it the same size).
3. I now move the scope using the NSEW buttons to slew the scope slightly until the images match up (I drag one of the images around so I can line up a star etc so I get them the same).
Now you can select a guide star and start the autoguiding and you will have pretty much the same image. There will be slight rotation when you do the same object a few days later. I suppose you could rotate the camera slightly to compensate but I usually just crop the final image to get rid of this.
This is a great looking image Leon ... collating data always gives better results due to the fluctuations in the atmosphere ... you capture different data each frame. This second image is well worth the extra time and effort. Well done mate !
Hi Leon,
There are subtle improvements in the new image - more dynamic range and less noise - but it seems to be marginal for the amount of effort - struggling with the same problem. With less noise you could probaly stretch it a bit more but don't know if you'd achieve much improvement. Love to see a crop of both images.
Craig
I like the idea of you using the technology at your disposal to return to the same imaging point on consecutive nights leon.
Very nice Rosette pics - but difficult to ascertain any subtle differences in these <200kb images.
Cheers
Doug
Many thanks for your comments guys, I enjoyed every minute of the experiment, although it had me standing/sitting next to the scope for 10 hours all up, I feel it was worth it and by your comment you all must agree as well
so I just calibrated PHD again, on that star, and it imaged the exact same spot for the rest of the night.
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I can just see myself doing that too 
