The following is a single 300 second sub taken from last nights imaging session.
The only processing done was a little noise reduction and sharpening the rest is untouched.
The single sub is the one on the left and the right one is a total of 15 @ 300 sec stacked in dss.
The camera used was a canon 1100d modded by hap griffin in the usa .
I feel the single 300 second image is better than the stacked one that totals over an hour of data.
Would like to hear other peoples opinions on this as well cheers Paul.
There does seem to be more colour range on the left pic where the right one is almost monotone. The right one though seems to show fainter parts of the nebula. Which program was used for stacking? If DSS how was the file saved? DSS can make for desaturated looking images with some options.
Hi kevin yes dss was used for stacking and the file was saved as a TIFF image then moved to another program for processing.
Is this the correct way to go about it ?.
1) long exposure time with Canon DSLRs cause saturation of colors range. Therefore you will loose color information when stacked in DSS. The bits R, G and B wil reache the maximum value or near it. It is normal the stars become all white after stacking. These loose depend from ISO value. Low value, less loose.
You didn't tell nothing about the ISO.
2) If you want better file to work with graphic processor you must use the original Autosave.tif-32 bits without any adjust action from DSS. The DSS team says: we do something but we are not graphic processor.
You can convert the 32 bits to 16 bit in the graphic processor. If you use the Photoshop you must use local adaptation when you can manipulate with HDR curve.
3) Because of loose of color information, the second photo has sepia appearance.
4) if you read the documentation of DSS, you will see that there are a maximum number of files to get the best performance of stacking task. More than it will not enhance the result.
Actually, you loose color information (my observation).
It worth experiment stack less number of photos and compare the result: stack only 5 photos (or less) and compare it with the result of 15 photos stacked. The color should be better but the noise will be worse.
Because this, DSS has the ressource to use more than one group on the stacking task. For example: the main group with many photos with low ISO and/or low time exposure. The group2 with few photos and higher ISO and/or higher time exposure.
You can use many groups as you want with many combination of ISO and time exposure as you want.
M 8 is a good target to test the use of H alfa filter. I am waiting a good weather to try it. I am thinking to use:
light:
a) 30 photos with 2 minutes and ISO 400
b) 5 photos with 2 minutes and ISO 800
c) 1 or 2 photos with 2 minutes and ISO 3200
It is not absolutely correct, but to the histogram I can say:
30 x 2 min ISO 400 = 15 x 2 min ISO 800 = 7 x 2 min ISO 1600 = 3 x 2 min ISO 3200.
The dference is with the periphery information. I got more with 3 x 2 min ISO 3200 than with 30 x 2 min ISO 400.
They will be processed at the same time with the group ressource.
H alfa:
30 or 60 (the maximum number that I got without bad position of M 8 in the sky) with 2 minuttes and ISO 3200
note: I don't use H alfa as a group together the others because my H alfa comes with much noises. It needs a separated process.
Another question, did you pre-process the image in DSS or save the tiff without alterations? Ray likes to process the image in DSS, but I like to process later in Photoshop. If you are processing later, make sure you tick the correct box for embed but do not apply changes, or some wording like that.
Paul there also appears to be some trailing in the stacked image. This will blur and desaturate star colour quite badly. I would look at removing the worst offending images from your stack. Register the images in DSS and then check each one individually (generally the ones which have a larger "FWHM" score are the worst). Just nuke those and things will improve.
-Cam
Hi Paul, I don't know if Kevin was referring to me regarding processing in
DSS, but he was right, I only use PS for downsizing, and maybe a little sharpening. I hesitate to offer any advise, being a newbie myself, but a
couple of observations might help. Many people complain that DSS leaves
you with a washed out image; this is true, but it is then up to you to
restore the colour, and get the luminance right, in order to retain
nebulosity etc, by adjusting the histogram using the RGB sliders
individually, and/or together. The three luminance sliders should be experimented with in order to tone down highlights if necessary, and bring out nebulosity. I generally find that the saturation ends up between 18 and 21. It is impossible for your stacked images to contain less data than your single sub, so I think that you have to be doing something wrong in DSS. My images are only of fair to middling quality, but there is no shortage of colour in them. Incidentally, I don't personally like
modded DSLRs much, as Kevin said in an earlier thread, the blue gets
overwhelmed.
raymo
Thank you everybody for your comments
And valuable information .
I will put it to good use next imaging session
And will see if I can improve my results thanks again.
