I imaged this at the start of this month, have been trying to process it for a couple of weeks now, and don't know whether I am doing something wrong or if there is simply not enough data in it too stretch out enough details. It doesn't help that my 450D isn't modded but hey…
If anyone else wishes to have a go, i can post a .tif.
Details are:
20 x 240secs guided Canon 450D (unmodded)
15 darks, 10 bias & flats stacked in DSS and processed in CS5.
Skywatcher ED80 @ f7.5
Heq5Pro mount
logitech c270 webcam w/PHD for guiding on a orion 50mm
guidescope.
That's about what you can expect from that setup with that amount of data. The mid tones could be stretched a little more... focus could be sharper. You won't get a blazingly bright horse unless you collect mega data, or have a fast optical system or have an astro modified camera either with a filter mod and / or cooled.
Try and shoot it at the highest possible elevation to avoid atmospheric scattering, collect more data and stretch the midtones a bit more.
Some people make the horse look easy, but it isn't!
I don't know what you are expecting, but I threw your jpg in photoshop, stretched it out a little, ran a HLVG (green cast) and this is what I got. It seems about right for a slow system and unmodded camera. Your camera is probably most of the problem here, if you were using a CCD and HA filter it would be much easyer.
I would also think a flattener would be of some use, as there is noticeable field curvature.
That's about what you can expect from that setup with that amount of data. The mid tones could be stretched a little more... focus could be sharper. You won't get a blazingly bright horse unless you collect mega data, or have a fast optical system or have an astro modified camera either with a filter mod and / or cooled.
Try and shoot it at the highest possible elevation to avoid atmospheric scattering, collect more data and stretch the midtones a bit more.
Some people make the horse look easy, but it isn't!
Thanks Kevin for your opinion/advice. I definitely need to look at an astro CCD for these kind of targets. I can't do the camera right now but if the weather stays clear, the time i can do.
Quote:
Originally Posted by rmuhlack
what ISO setting are you using? I use ISO1600 with both my 400D and 1000D
I knew i left something out Richard
I use ISO800 most of the time, including this one. I do this because I feel that there is a little less noise to deal with later on. In your experience (I've only been doing this for a couple of months ) do you think that the higher sensitivity of ISO1600 is worth the extra noise or am I going about it the wrong way?
Quote:
Originally Posted by Peter.M
I don't know what you are expecting, but I threw your jpg in photoshop, stretched it out a little, ran a HLVG (green cast) and this is what I got. It seems about right for a slow system and unmodded camera. Your camera is probably most of the problem here, if you were using a CCD and HA filter it would be much easyer.
I would also think a flattener would be of some use, as there is noticeable field curvature.
Peter, I don't know what i'm expecting, that's why I'm asking for opinions from people with more knowledge and experience than I .
Just wanted to know whether I am on the right track, or if i could be getting noticably more from my setup, and improve my technique.
I noticed a little more detail in the horse head region with the extra stretch, but then the sky seems too light for my taste, so left it as it is.
You are right about the flattener though, i was hoping to use a focal reducer to speed the system up a bit, but there goes that i suppose
Peter, I don't know what i'm expecting, that's why I'm asking for opinions from people with more knowledge and experience than I .
Just wanted to know whether I am on the right track, or if i could be getting noticably more from my setup, and improve my technique.
I noticed a little more detail in the horse head region with the extra stretch, but then the sky seems too light for my taste, so left it as it is.
You are right about the flattener though, i was hoping to use a focal reducer to speed the system up a bit, but there goes that i suppose
I am no refractor expert, but I think most "focal reducers" are reducer/flattener combination, so using one should clear up the field curvature aswell.
I didn't make the sky darker because there is uneven illumination in the image in the bottom right so darkening it too much clips that section, I think your biggest improvements would be a flattener of some sort.
Bintel have reducers / flatteners. The Orion brand has either but not both in one. I have the Orion Field flattener for my ED80 and it works well. But if you want both a flattener and reducer there's the Tele-vue TRF-2008 which I have heard good things about.
As for ISO speed, every camera model is different. My old Nikon likes ISO 400 and in fact shows fainter stars at ISO 400 than 1600. But your Canon will be different. Take a couple of pics say at 3 minutes or whatever you think is suitable for your setup. One at ISO 400, one at ISO 800 and another at ISO 1600. Stretch the slower ISO pics until they match the higher ISO pics. Place them side by side on the screen and zoom in to some faint stars. Whichever ISO shows the faintest stars wins. At least that's how I do it.
looks like the tele-view TRF-2008 is a winner. Yup pretty sure i will need both as you guys have pointed out.
Anyone know if santa has e-mail? Still four hours to go…
There is a nice little experiment you can carry out, which will help you
discover the optimum ISO for your Nikon. Download Neatimage[free].
Take identical single subs at 400, 800, 1600, 3200, and 6400, and see
what success Neatimage has removing noise from each of them.
Choose the most successful ISO for your multiple images, and if it does
a pretty good job with higher ISOs such as 32 or 64, remember that there might be occasions when a single sub is all you can get, and still get an
acceptable image.
raymo
I knew i left something out Richard
I use ISO800 most of the time, including this one. I do this because I feel that there is a little less noise to deal with later on. In your experience (I've only been doing this for a couple of months ) do you think that the higher sensitivity of ISO1600 is worth the extra noise or am I going about it the wrong way?
From my own experiments (see here and here) I have found ISO1600 to give the optimal signal-to-noise ratio with both my 400D and 1000D at virtually all sub exposure times and at all temperatures. I take LOTS and LOTS of sub exposures and also dither my sub exposures to keep noise in check and provide a further boost to the SNR.
Kosh
It's there alright. Stretched with nebulosity and cleaned up in photoshop. A flattener of some sort would be the go.
cheers
and have a great Christmas
Stephen
Thanks a lot guys, those pictures are more like I was hoping for. So perhaps if I just add a lot more frames it will improve the SNR and becomes easier to stretch the details out without as much noise, is that how it works?
Richard, those are some great images. Thanks for the info too. Will definitely see how I go at iso1600.
Would anyone like to guess at the cause of the gradient I keep experiencing?
Is it also because I need a field flattener or something else? I seem to have a lot of dew forming on the lens, light pollution, can these cause it ?
.
