Quote:
Originally Posted by yoda776
Hi everyone,
I actually took most photos through my LX200 8". A couple of questions.
1) How do you set up the DSLR so it has the best focus? I was trying to use the viewfinder and had nothing else. I was told some cameras show it on the back screen. Not sure if these do have an ability to show on screen. i know my photos seem a little out of focus.
2) What is the best ISO range for taking deep sky objects? I was sitting at ISO1600 (think I am recalling correctly!). I took 30 sec, 1 minute and 90 second exposures. Found that over 2 minutes had too much noise in brightness for Orion.
3) Is there a preferred exposure time for DSOs? I understand stacking is better but would like to know length of exposure.
4) Also when accumulating exposures of an object is there a good range or magic number to take for stacking (particularly in these examples)?
Thank you in advance for your help.   |
Hi Yoda,
I have a 450D and LX200GPS 10" which I use all the time when AP, so here are some tips from me with this rig:
In order of appearance I have in the train: Scope/Moonlite focuser/focal reducer/450D with nose piece into the focuser.
450D wins here because of live view, 350D does not have it which makes life harder.
Use a 6.3 focal reducer,(Celestron, Meade etc).
Watch out for the newer Meade's FR though, I've heard they are different somehow.
1) Definitely use some software on a laptop, I use BYEOS as it has great features to make focus easy. Electric focuser, (I use a moonlite which rocks as I can put the focal reducer inside it and it's at the right spot), the Meade Zeroxx is perfect as well.
The way the focusing works by using BYEOS is click a button in the software to go into a live view type mode, this has a large area which shows bullseye for centering and other good stuff and is a live view. It has next to it another area which is magnified so you can use that to make the star on screen as small as possible. There is even a readout in numbers that measure the size of the star and the lower the number, the better the focus.
I also use the bahtinov mask as well, as again, the software and live view makes it so easy to use. It takes seconds to focus and this is always a double check from the other method and vice-versa.
The first part of course is finding the star to focus on but you have that bit sorted.
2) I use ISO800 most times, 1600 is way too noisy on the 450D in my opinion. Actually 800 is still a bit noisy as compared to 400 and others have also recommended 400 to me. Reason being, 400, less noise twice as long exposure vs more noise and half the exposure time. They say better signal to noise ratio when using 400. Also depends on guiding times etc.
When using the software for framing the view etc, set a high ISO when lining up on the object you are viewing and don't forget to go back to 400/800 when taking your subs. Experiment a bit here as well, give ISO800 a go then give 400 a go. Compare results.
3) Depending on your mount/polar alignment/guiding system determines how long your subs can be. Again, the 6.3FR makes all the difference here as you get more field of view than F10 and it's faster. I keep my FR connected all the time on the Meade.
I am no expert here but for Orion Neb I use 2 minutes@800, same for Eta Carinae Neb. Try 3 minutes on Eta and compare. Galaxies for me are better at 5-7 minutes ISO800 with good guiding of course. That's about my limit with Meade tripod and a wedge.
Galaxies may be better at 400 ISO but need longer time and a good mount/guiding.
The camera sensor temperature can creep up too on long exposures and other factors like light pollution, summer vs winter temps etc.
All worth considering when determining exposure length.
With my rig, stacking is always necessary as you want more than 1 exposure as well as Darks, Flats and Bias shots.
4) As for stacking, the more subs the better. For my first Orion Neb, I took about 25 frames 2 mins @800ISO, Couple of years later took 52 frames and heaps better. I would like to have tried 200 subs as a test because I've seen some amazing pics here on IIS with heaps of subs/data and they look amazing.
I didn't do the short exposure trick to show the trapezoid like a lot of people do with Photoshop as I'm ordinary at processing.
Darks, Flats and Bias shots are also the way to go with the 450D.
I usually take a few more of these other shots than the lights, so 50 lights, 63 darks etc. No real reason why as there are so many views on this but for now, it's fine.
Here is a link to where I have uploaded the photos I have taken with my scope, they are ordinary compared to most you see here on IIS but it will show what what I have done as most have been taken on the 450D and LX200. Most pics don't have a lot of subs,(15 - 30), but you will see that with not much data the DSLR has made me happy with what I have so far.
http://redbeardpix.wordpress.com
Let me know if you need any clarifications.
Cheers,
Damien
) and have something worthy of printing out and putting on the wall to say 'i took that!' 
