Quote:
|
map for Saquarema, RJ , Brazil...Yellow, green and blue zones ,,,you are a long way away from Rio.
|
Yes, Kevin. Actually I don't know what colour zone I am. I have light pollution form Saquarema and Araruama city. They are 14 km far from me. And I have some street light very near my observatory. I needed to build a new one because the light incoming inside my OTA !
Look my old observatory here:
http://astronomia-e-astrofotos.10697...83/cf-9097.jpg
And my new observatory here:
http://astronomia-e-astrofotos.10697.../IMG_1062A.jpg
Best view of the new here:
http://astronomia-e-astrofotos.10697...ur-td1723.html
Now I haven't problem with incoming light.
As I always say my main problem with light pollution is my proximity to the beach and a lake that is source of salt. I have that salt fog atmosphere. I need wash my main mirror each 4-6 month !
I have much reflexion of street light on this salt fog creating a glowing dome around me.
Quote:
|
your camera has a "native" ISO usually around 100-150 ... subs and then stack for noise reduction etc which is the benefit of higher ISOs
|
yes, you are right. I don't know the native ISO of 350D, but as its maximum ISO is 1600, probably its native ISO should be around 400. Just the ISO I most like to use. With Canon 1100D maybe the best ISO, for me, should be 800.
The number of subs is my main strategy to get quality and amount of details.
Now I am perceiving an increase of noise, mainly in red channel. Only in red channel. I back to 350D to test if it has something with the IR filter. My 350D hasn't it.
Any Halfa photo with my 1100D presents very too much noise. A granulation white large spot noise. As little stars.
I saw much less noise, and normal noise, with 350D.
I don't know if this increasing in noise has source on this filter or if my atmosphere here, summer, was changing. I have an ozone hole over Atlantic near South America. Maybe I am having much intensity of IR and NIR radiation that is causing this amount of noise in red channel. Actually I don't know.
M 42 isn't a good object for test, but it was in good position after I installed and calibrate focus in Canon and guiding cameras. You can see the quality (despite of overexposition) of Halfa with 350D in
http://www.iceinspace.com.au/forum/s...d.php?t=130271
350D has problem because it needs more cable and USB port to remote control. Very old, it has bad contact in connectors. Less resolution than 1100D, its pixels are larger. But if the noise in red channel is less, I will return to use 350D.
I published this message because there are many ask about why I use low ISO and short sub exposure. I do it because of my site. Each case is a case. We can not think as LAW: you must use high ISO and long exposition subs.
The same about the focus issue, here in my site. The same salt fog atmosphere produce an intense refraction. My stars never stop to dance. They change continuouly its shape with much intensity. My set has high resolution and it perceive it. It is very hard to say: well, I am with good focus.
I don't know if it is the same for you, but for me the focus with strong stars is different than with faint stars. I can have appearance of good focus with brightness stars and bad appearance with faint stars. And focus faint stars that never stop to dance... it is problem.
My stars always present a more chubby shape because it was the sum of those distortions, causing an appearance of out focus. But if you see the line of spikes, you will see that they are single line. So the image is near the good focus. Perhaps, in good focus.
