I hoped to get deeper images but cloud has plagued this effort until next new Moon. They were of the worst sort, thin and intermittent. They keep you up all night with little to show for it. This image is from four eight minute exposures taken between clouds so it is reasonably deep. The aim was to get twenty minute exposures. Even so the very dim background stars are there.
Details
Canon 5DH. 300mm F2.8L at F2.8, Hutech LPR filter, 4X8 min at ISO 200, corrected for flats with IP, stacked with RegiStar, digitally developed in IP, levels and curves in PS, RL enhancement in Ip.
By all means Andrew. I tried to 'calibrate' my monitors with Adobe Gamma. I dont know whether it helped. If you look carefully the green cast is very dim stars everywhere.
By all means Andrew. I tried to 'calibrate' my monitors with Adobe Gamma. I dont know whether it helped. If you look carefully the green cast is very dim stars everywhere.
Bert
Yes I use Adobe Gamma too but haven't done it for a while. It's suggested that we do it regularly to keep the correct gamma, but I forget sometimes.
This is what I've come up with just as a quick play in PS.
It's only using your 135kb lo res jpg not the full res 2MB.
I am amazed at the amount of detail you captured even under those conditions.
It seems those thin intermittent clouds have it in for us this season.
Why the images are so sharp is that I can now adjust focus as the temperature of the lens body changes without disturbing anything. The stepper motor focuser I built needs to be adjusted by one thousand steps for every degree change in temperature of the lens body. One thousand steps corresponds to 0.1 mm linear movement of the focus ring. So even over a long series of images (or night) I can change focus between each exposure to keep accurate perfect focus.
This also shows why these lenses cost an arm and a leg and a torso,they are so close to perfect that a 0.1mm movement in the focus ring is noticeable and only at the pixel level. The other thing is the lens wide open at F2.8 is almost as good at the corners as it is in the centre.
great work. What does the 5DH mods give you over a vanilla 5D?
Gav
It gives greater sensitivity to H Alpha (656.3 Nm) which is emitted by single Hydrogen atoms (not Hydrogen molecules H2). Human vision is not sensitive at this wavelength but it shows where the H gas is if stimulated into emission by nearby hot blue stars. Without this mod there would be very little red in the image. Hope this helps.
Sorry to bore you all but very accurate tracking also helps to get the signal to noise of even the dimmest of stars above the inherent background noise.
In the past these dim stars were so blurred by lack of accurate focus and inadequate tracking that they looked like noise. So I eliminated them by processing them as a black background.
If you did not notice I did take some images with the 100ED and the TAL200k just to see what was real and what was noise.
Oh and another thing the original JPG from the 73MB TIFF is a 15MB JPG.
great work. What does the 5DH mods give you over a vanilla 5D?
Gav
Just in case you're interested Gav, there's a 5DH for sale here on IIS.
Trevor has done some great images with it and is now going onto a dedicated CCD imager.
Congratulations on a great shot ! the only processing issue with this shot is that the red channel in shadows has a slight clip and the colour inbalance is coming from the colour bias in shadows being uneven.
To me this does not detract from this gorgeous shot so well done.
Tried processing levels and curves again and treated all colour channels about the same. It is most probably too red but thats the way the camera sees it.
The reality is if just a small part of the image is presented with excess red it looks fine. People are not used to seeing widefields with the H Alpha regions accentuated. See crop of small region of large image below.
Thanks Scott. The Canon lens rotates inside its mount so orientation for best framing is relatively easy. Mike (iceman) put me on to Autopano and it works well on starfields. Below is a quickie made with the demo version.
Just for interest here is a pic taken with the Tal at 1790mm and exactly the same area cropped from the widefield taken at 300mm. It gives an idea what is real and what is noise in the widefield.
