Just finished the pc link up, heres a pic of 11 x 60 sec combined with deep sky stacker. PHD guider, web cam, heq5prom, sw80 for guide, 200mm f3.5 $38 ebay lens, olympus e-420 with pc control.
How do i reduce the blow out of the stars and still keep the sensitivity. I tried reducing aperture with good results on the stars, but the nebulosity disappeared.
It looks like it could do with a bit of an increase in saturation to start to bring out some more colour.
Can you supply some more details about the capture? Did you shoot in Jpeg or RAW. How have you processed the image? Did you use Photoshop or another image manipulation software?
Yes i shoot in raw, and just a basic stack and color adjust with DSS. I am trying to get the camera/lens working first before i get too carried away stacking and processing..
I guess Jason what Paul is saying that your hardware takes the image, its there, but the skill of processing is where your data comes back to life. For me capture is about 30% of a image and processing makes up the 70%.
Though with 60 second captures, the effect of dropping the F# you will lose the nebulosity because it is a lot fainter than the stars, and just like in visual, if you want to see more increase your aperture. This is why better cameras and better lenses produce better wide field shots.
So what im saying is:
Increase your capture time to say 120 -180 seconds, making sure its guided
Be sure your focus is good
Quality of the capture is dependant on the hardware. $38 ebay lenses will produce about the same quality.
Use photoshop or something like that to introduce non linear curve adjustments.
Yep its the age old dillema - exposure for nebulosity versus star colour blowout and white stars. I just had a play with your image and a lot of nedulosity is still there - it just needs some stretching to bring it out.
Obviously best star colour is obtained with short exposures to give small non bloated coloured stars - as you probably know most of the star colour is in the star fringe but a longer exposure will burn the fringe to white. But as you said the trade off is in nebulsoity. There are compromise solutions that you can use that range from easy to difficult (with a corresponding degree of success) in processing.
I know you dont want to get bogged down in processing yet (good idea - i've been bogged for years) but included this below for when you do start.
If you arent familiar with processing I would suggest exposing to get your nebulosity to a level you are happy with (but not too much) then select your stars in photoshop and just adjust the saturation to enhance the colour. Selecting the stars can be done with color selection in PS but the easiest way is with Carbonis PS actions (good but you pay for them ) or my actions from my website (not so good but still works and they're free). After seleting them with the action expand them by say 2 pixels on this image (Select->Modify->Expand) and then use Image -> Adjustemnts->Hue/Saturation and expeiment with the silder for saturation increase (start at say +20 and expeiment from there). This will colour up the stars without turing your nebula into a neon sign.
Once you get some images under your belt you can play with taking the bloated stars out of your image and replace them with shorter exposure stars - but that requires a bit of touch with PS.
Thanks guy's some good advice there for me to work on, On thursday night i got a good drift alignment done and was able to take 8 min sub's. just need to experiment now to find the best f-stop to use. One test at f5.6 produced very nice stars with pretty difraction spikes. Looks like good weather this weekend so i will give it another go.
Ok here is the same data with one 8 min exposure at f5.6 added. I stacked and color corrected in DSS and did a channel adjustment in photoshop6. I also shrunk the stars using the color selection method that was suggested. I am happy with the improvement and cannot wait to try a full set of different exposure times and dark subtraction. Fingers crossed i might learn this yet.
Thanks Rowland, i had read that befor but it's always rood to go over these things again. I went looking for some more information about processing and have found that there seems to be very little on the net? Can any one point me toward some reading?
Data from 19th june, i have taken 4 different brackets, 10 pics of each up to 60 sec iso 800. processing and color correction in DSS and channel adjustment with PS6. It seems like the olympus always tends toward a purple color ? or is it just my processing?
Hi Jason. The red is there, diffused throughout the regions around the nebula. It seems to be in the right places - I used a different process to bring out the colour, but it only shows that it's there - tending to over saturate the image otherwise.
You might try a higher ISO and/or a few longer exposures to combine with the shorter exposures. I think you may need more signal, to bring out the colour - some darks to eliminate the thermal signal. I'm not completely sure, but there seems to be some thermal noise faintly in the background, and WB may be out, which is creating the purple.
Thanks for the reply. You may be a beginner but your input is helping me learn. I have taken some 8 min subs, but field rotation is becoming a problem. I think its caused by coneing? Also the olympus can only do 60 sec or 8 min no in between. unless i do it manually with the IR remote. Brrrrrrrr, Need some new long johns for that.
Attached pic is an unprocessed 8min sub.
If you colour enhance the image and then adjust the white balance it shows a predominance of green. I think adjusting in-camera white balance is the first step. Or adjusting WB before stacking the images.
I notice that if you duplicate the image and average the two and then apply white balance, the nebula takes on a purple tinge with a muddy background (like a previous image). There are millions of stars in this region, as far as I know, so it's unlikely that the background will be all dark.
Otherwise WB correction of the image shows lots of pink and red, with surrounding star fields.
Stack with some 1 minute exposures as well, and use darks for thermal signal reduction.
I just released another one of my tools, StarBright, which could maybe of help.
It trades resolution for longer exposure times, but never over-exposes any part of the picture (it does automatic HDR compositing). It was specially designed for people like you and me, who have resolution to spare, but can't rely on longer exposure times.
Even if you don't have resolution to spare, it can still be of service.
Unlike StarWipe, I don't have a manual yet (it's a pre-release for now), but if you get stuck, drop me a mail or PM.
If curve manipulation starts giving you banding/noise or contrast starts to suffer, give StarBright a go.
hello, Your programs look promising and i am keen to have a go. however after downloading your software i realized this is a command line interface.
Where do i place the program and file so your software can find it? What are the values of the switches and what do they control?
hello, Your programs look promising and i am keen to have a go. however after downloading your software i realized this is a command line interface.
Where do i place the program and file so your software can find it? What are the values of the switches and what do they control?
Hi, I don't really want to hijack this thread , but a manual should be out soon. In the meantime, just running the app without any parameters should output a 'help' text, explaining the parameters and switches. Fortunately there's not that many (anymore), so it shouldn't be too hard to get StarBright to do something...
Thankyou Jager, I finallay got around to learning starwipe and starbright. It was easy in the end. here is an example useing it with default setting. This is with a 56mm objective 200mm fl camera lens. I don't think i can do much better with this setup, except maby getting the color levels better. this is NGC3532 befor and after shots.
![[1ponders]'s Avatar](../vbiis/customavatars/avatar45_9.gif){kind=avatar}
I will have a reprocess. I'm lucky with the olympus raw i can adjust the WB after.
, but a manual should be out soon. In the meantime, just running the app without any parameters should output a 'help' text, explaining the parameters and switches. Fortunately there's not that many (anymore), so it shouldn't be too hard to get StarBright to do something...
