The Journey

[gremlin750]

Thought I would record my appreciation to those folk on here who dish out the very sage advice and tips for imaging. Also, to encourage others who, like me, are just starting I thought I would post 'before and after' shots of M42, everyone's favourite first target for imaging. The first one was my initial attempt just after I had bought my scope, the second after having read up on here about the best techniques.

Both were taken using the exact same setup and equipment (Skywatcher 150P on an EQ3-2 using prime focus with a Nikon D7100), the only difference is the technique. The second one was actually under far worse light pollution than the first (front garden, under street lamps, rather than back garden, where it is darker). There is still plenty to do (I could see from the second that I needed to collimate the scope which I have now done and I still need to work on the flats) but it is, as the title suggests, a journey. I may trade up to better equipment in teh future but thought it would be better to push the existing setup to its limits (and learning along the way) before I spend £s on things that are expensive mistakes.

Anyway, thanks guys for all the hints and tips on here - it's been a great help.

(PS: for those who like the nerdy details - first one is a single 15 sec exposure at ISO1000, no processing; second is 20x30sec lights at ISO800, 20xdarks, 20xbias, 20xflats all stacked in DSS with final tweaking in Photoshop Elements)

 

[Dbswales]

That's a great effort and the difference is worlds apart. I'm only just starting myself so totally appreciate what you're talking about when you mention the help on here being absolutely invaluable.  

Dont stop mentioning the 'nerdy details' as I find them really handy trying to see how others get the image through. 

Great post, great image. I look forward to your next target.

Dan

[wimvb]

Great image!

It seems we have nearly the same equipment, so here's my question for nerdy detail: what is the maximum exposure time you can get out of your setup?

[gremlin750]

Thanks Dan and Wim

Wim - I tried 1 min exposures a couple of nights ago on M81/2 (pic below - 20 x lights @ISO 800, 10 x darks plus bias and flats). You can just start to see the stars tralining so I probably wouldn't want to push it much more than that (and I was fairly careful with the polar alignment). That is also where light pollution starts to make itsel felt as I'm in a fairly major town, even with a LP filter. I think I would have to look at guiding if I wanted significantly longer exposures and that probably means a new mount as well as the guide scope and camera. As I mentioned on the original post, I'm trying to squeeze as much out of the existing kit as a way of learning the basics before moving on.

What is the longest exposures you have tried?

[wimvb]

I have been able to do 2 minutes and on one occasion even more. Lately I have trouble getting decent images over 90 secs even after drift alignment. The 150 P with DSLR is just too heavy for this mount.

Here's my best single frame ever (oddly enough also M81/82 at ISO 800): 300 secs unguided, after masked stretch and resampling in PI (therefore less contrast than with histogram stretch).

The stacked image from that occasion is in my gallery on this forum.

BTW, as you can see: the scope has a serious coma issue, but stars are round in the middle and the stacked image shows a fair amount of detail.

Edited April 2, 2016 by wimvb
coma