Whirlpool galaxy

Posted by: Kijja

This picture may not meet a standard level yet. However, it is the best of my attempt on Whirlpool galaxy with a great help from APP. I took 40x60s light frames with unmodified Canon 70d mounted with Canon lens 100-400 mm LII @ 4oomm  F 5.6  ISO 6400 in 2 mornings.   

Excellent Kijja, nice colors and framing 😉

Were you able to guide the exposures? Or are they unguided? If not, have you tried star shape weights in integration? (could help with getting a sharper integration..)

Is there a specific reason for you to use ISO6400? Maybe if you reduce it to ISO1600, the stars will be less burnt-out in following exposures?

Kind regards,

Mabula

Hey that's a great picture. Like Mabula said, ISO1600 is kind of a sweet spot for signal-to-noise ratio on a Canon. Sometimes on mine I'll even use ISO 800 to get better Star color. I imagine ISO6400 you must have had a lot of red background to massage out. Also to back up what Mabula said, when integrated unguided Subs there was a big difference between quality and star shape and treating them the same. Star Quality so it's best for unguided. Also before you integrate, right click on one of your subs and select sort by star shape. Then double-click the lowest graded sub and examine it in the viewer. If the stars are ridiculously streak throw it out, move up to the list until you get to the first sub that's acceptable and you're done sorting through your subs for star shape

You did a really good job!

Thank you Manuba and Red Giant

This picture was taken on Skywatcher Staradventurer mount without autoguiding. It is my experiment on high ISO for the shortest possible for unguided astrophotography. The idea came to me when I was taking this galaxy bacause I had only an hour before sunrise for taking it. And of course, the result from APP was so nice that I want to try more.  

Hi Kijja,

Just to follow-up, it does depend on the camera model and specific sensor off course, but with ISO6400 you run the risk of saturating the brightes stars very fast and decreased dynamic range in your exposure without other benefits like decreased read noise when compares to for instance ISO 1600 on a Canon camera. So even with short exposure I would advise to not set the ISO that high unless the camera has a specific sensor characteristique that turns on on high iso values that further reduce the read noise, that you can exploit then. Some newer camera models have this, but I am not sure if the 70D has that, do you know?

Nice image still 😉

Mabula

Sorry for leaving this post for a while. I did some new images with ISO 1600, stacked with my previous version. The colours are better I am pleased with the result.