Well, it was windy down herein melb! Have to admit I was a little nervous outside a few times. Luckily we have no major trees near our little backyard to threaten the scope. My little banana scope, E-130D Tak, is so stumpy that I doubt it was affected by the wind. One advantage of a relatively light setup.
This is all I have from a bothersome night, but as it's my first ever Eta Carinae, I'm still chuffed. What a magnificent object that is. Mysterious thru a scope, like an amazing flame in the live viewfinder after a 10 sec shot.
I've read somewhere recently that most of today's SLR's don't really start increasing in noise until beyond ISO 1600, so tonight I tried 1250. Very pleased with the noise levels. Anyone else experiment with higher ISOs? I need to do more, to see if it really makes a difference.
Due to my alignment woes (a poorly levelled mount), I couldn't use the 1 min subs, shameful. Weird, also the EQ-6 mount seems to go haywire, I do a 2 star alignment and it doesn't seem to keep it, eg. tonight I had to manually find Eta.
But these, wait for it.....20 second subs, I was amazed at what I could see with just 30 by 20 sec subs.
Nice one Simon! Lots of detail there. I've also been really surprised by relatively short exposures, and a little disappointed with what comes out of DSS
I've not done any qualitative analysis, but use ISO1600 in the suburbs and it's not too horrible. ISO3200 on my 1100D is pretty ugly though. Maybe from a dark site sometime I'll try lower gain and see what happens
Thanks Dunk. Do you use a LP filter? They make quite a difference to my shots.
Yes I use DSS too, pics from that are always bland. But once you stretch them and remove background noise, the image pops again. I do use Pixinsight though...
Thanks Dunk. Do you use a LP filter? They make quite a difference to my shots.
Yes I use DSS too, pics from that are always bland. But once you stretch them and remove background noise, the image pops again. I do use Pixinsight though...
Doh! No, I didn't think to try a filter especially as Eta is over Sydney for me
Hi Simon, You mentioned experimenting with higher ISOs. I have only once come below 1600, [800]. I normally mix up my subs, some 1600, some 3200, and sometimes I add some 6400s. I always use in camera
noise reduction, although I understand most people don't, because of the
imaging time that is wasted.
raymo
I'm using this filter, in-camera, highly recommended! :
LPS-D1-EOS : $209.00, email Ted at Hutech, it's excellent. It's not on their price list, a new addition. Before I could only take 30 sec images, now I can take ones of many minutes.
Raymo, thanks, i'll definitely try 1600 in future. I just had a response from Phil Hart re this topic of sensor ISO and sub lengths. He rightly says that quality of image doesn't vary that much from low to high ISOs when using noise reduction (darks or in-camera). And at pretty short exposures, eg 30 sec to 1 min, you can use huge no's of short exposures to very effectively match longer exposures of multi-minutes (eg 4-6 mins). See this:
Just a note on the ISOs, ultimately, once you go beyond the point where you are getting one signal level (ADU - analog to digital unit) for per set of electrons/noise, then you are simply making the image appear brighter at the expense of dynamic range (total pixel electron capacity / total pixel noise). Older cameras have more noise than newer ones so older cameras managed only ISO 100 - 400 before images really started to suffer. Modern cameras, particularly the Nikon D5100 and later, the Canon 5D mk2 and later full frames can take really high ISOs 800-3200 and not suffer too badly. Canon 600D/60D and later seem pretty capable around ISO 400-800 in my experience.
Yes it does cam, I'll try 400 next time. The peak dynamic range for my camera is around that figure. I've been using 800 for a little while, so time for a change.
Dropping the ISO becomes problematic when using an LP filter as these filters chew quite a bit of light, anything from one to two F stops. If you drop the ISO too far without an increase in exposure time, detail becomes lost in the black. Kind of like black clipping and the SNR gets worse again.
I can sympathise with the difficulties of shooting nebula with an OSC camera in LP skies. It's a delicate balancing act.
especially as Eta is over Sydney for me 
