NGC2237 (Rosetta nebula) with modified 350D

[le_R]

Clic to enlarge

==== Equipment ====
Télescope : Skywatcher 80ED (600mm)
Monture : Skywatcher HEQ5-Pro Goto
DSLR: 350D (IR filter removed)
Barlow : non
Réducer : non
Filter : Aucun

==== Place/Weather ====
Place: Morlaix (France - 29) in town
Clouds : none
Wind : none
Temperature : -3°C
Humidity : 75%

==== Processing ====
Exposure number : 3 + 5 Darks + 11 Flats
Exposure duration: 360 sec (6 minutes)
ISO : 400
Total: 18 minutes
Software: Iris + The Gimp (niveaux)

Next time, the centring will be better


And this is a Raw :

[Nighthound]

You're off to an awesome start.

I find this one really starts to pop at around 2.5 hours total. Other than noise level reduction, I'm curious to why you don't push your ISO to 800? How does your 400D compare with the red response of the 350D mod?

[le_R]

Maybe is it better with more saturation ?


Of course there is a lack of exposure with only 3 * 6 minutes

ISO400 is a better setting than 800ISO and 1600ISO. there is lesser noise ! But it's also a better setting than 100 and 200 ISO. It's a compromise between thermal noise, signal level, readout noise, and histogram spread.

To resume, ISO1600 is only a shift of the ISO100 data, assuming you work with RAW frames. i think it's a too difficult challenge for me to explain that in english but you can find a lot of litterature : search for ISO and RAW on cloudynight for example.

The test comparison between my 400D and the 350D Mod is planned, but i am waiting for a clear sky

[troypiggo]

Great work. Very similar equipment to me, so you've shown what I should be able to do with it if I actually improve. My camera isn't modified, though. I only have the one SLR.

[Nighthound]

I wouldn't underestimate your DSLR capabilities at higher ISO settings. While it's true that 800 will produce a higher level of noise than 400, the compromise of light sensitivity in this application should be weighed out. The combination of a fast optical tube and higher ISO setting combine to help significantly with greater light gathered in less exposure time. For many (including myself), this is a great asset when shooting with a mount that is not of the highest quality in craftsmanship or technology. I find that shooting more exposure time per object and using capable software for stacking can easily deal with any objectionable noise that may occur. Add Noel Carboni's Astro Actions for Photoshop in the workflow and noise is so minimal that I place it far down my list of concerns when shooting deep sky. And this is coming from someone that has never taken or applied a dark frame in the stacking process. I know my images would benefit from dark frames but honestly I'm not out to produce images that can be printed wall size so I stick with what works for me and the level of quality that I feel is quite acceptable for DSLR work.

I shoot at ISO 800 with my 20D and 5D in the warm months and up it to 1600 in the cold months. My sub exposures range from 4 to 5 minutes and I keep total time targeted at 2.5 hours and have gone as long as 5 which is ideal for the very faint objects. My refractor is f/4.5 @ 407mm and my mount is a Losmandy G-11 w/Gemini. I also shoot with an f/4 newtonian. Below are some samples, some were taken at ISO 800 and 1600 (mixed subs) and some at 800 or 1600. They're not Greg Parker/Noel Carboni or NASA quality but they do demonstrate that higher ISO settings with today's DSLRs can aid in going deeper on deep sky objects without major image quality compromise.

None of my DSLRS are modified.

http://i3.photobucket.com/albums/y67...crctlatest.jpg
http://i3.photobucket.com/albums/y67...lifnebccx2.jpg
http://i3.photobucket.com/albums/y67...Thorshelmx.jpg
http://i3.photobucket.com/albums/y67...hdflm3bxxc.jpg
http://i3.photobucket.com/albums/y67...m78sky90-x.jpg
http://i3.photobucket.com/albums/y67...ord07s90cc.jpg