This seems to a popular target at the moment, and so here is my take on NGC6729.
Tech Details:
Telescope: 130mm f5 newtonian
Mount: HEQ5 w EQMOD
Camera: DIY Peltier modded Canon 450D, with sensor at a nominal regulated 10 C
Guide scope: Rubinar 500/8 with QHY5L-II
Software: SGPro and Pixinsight 1.8
Capture: 155 x 8min subs @ ISO1600 captured over 5 nights
As per my recent Helix Nebula image, this one has also been pre-processed using Pixinsight's Bayer Drizzle feature, which results in a demosaiced RGB color image directly from calibrated raw data without interpolation.
Based on the feedback from the last image I've tried to go easy on the decon, whilst still aiming to pull out some detail in the dark neb and reflection neb areas.
Fantastic, one if my favourite spots in the sky and done very well. I'm guessing you had one scope aimed at the helix and this one at ngc 6729? Efficiency plus!
Fantastic, one if my favourite spots in the sky and done very well. I'm guessing you had one scope aimed at the helix and this one at ngc 6729? Efficiency plus!
Correct - two scopes means twice the productivity!
Minor critique on a very nice image - I think you've stretched the image a little too far, which as slightly blown out the fainter stars and so reduced contrast with the background.
I have to say it again, what a fantastic example of using the equipment you have to achieve a fantastic result. This is an example of pushingthe envelope to its maximum and should provide inspiration to others as to what is achievable.
Wow, that is really very nice. A superb image of this area. The stars seem more yellow than is normally shown. A DSLR is more likely to get the correct colours of things. Nice to know next time I image that area.
Yep, this is a beauty Richard and shows that there are many dimensions to every image and overall a lovely looking image can still be had without text book perfect stars across the frame, really well done
Thanks all. My goal is to push my gear and processing to its limits and I have been very pleased with the results I have been seeing recently, especially with the benefit of longer (dare I say "mega") integration. However I don't mean in any way to imply that my images are perfect (far from it) and completely agree that the star shapes are "unusual" here. In fact I am very much open to suggestions as to what the cause may be - all the subs have these odd shapes.
As a start I will check the collimation over the weekend with my cats eye gear, and also check the primary mirror clips in case it is pinching. I also have a tilt adapter I can use if need be. Pinching/distortion of the secondary is also a possibility I have considered. The secondary is a GSO 50mm from my dob, and is glued into a recessed secondary holder so it will be difficult to pry loose without damaging it. In any case I will report back on the progress for the benefit of others who may refer to this thread at a later date.
It can be a slow going to trouble shoot all these issues sometimes but I can see progress. I now have two permanent setups, I have two modded cameras with cold finger regulated peltier cooling, and most of the automation is now under control. Onwards and upwards I say!
Could you do us a favour and post a comparison shot of (say) 155 shots versus 75 shots stacked? I'm just wondering the visual difference and the effect of the law of diminishing returns on such efforts. Good on you for doing so many!
I love Pixinsight's batch processing, it's so easy once you get the hang of it.
As previously mentioned there's a lot of yellow dominant stars there. I have to put my glasses on to see anything wrong with the star shapes, maybe just a little at the frame edges but that's fine. Better than I could ever do.
That's a great image, I'm trying the benefits of MEGA exposure like you...not so far from the best indeed, getting this achievement with a dslr is stunning and pleasant ...congrats!
In fact I am very much open to suggestions as to what the cause may be - all the subs have these odd shapes.
Having owned that scope previously maybe I can pitch in a few things to check unless you have further modded it.
1_ Secondary is fine. No astigmatism there and the bond on the alu plate is very light. No stress.
2_ Primary is not clipped. Rubber just holds the mirror. No pinching.
3_ Focuser is as square as I could get it. Having said that this scope is very hard to collimated perfectly.
Good think is once it is it holds collimation very well. MPCC (type I) spacing is critical as well. From memory my spacing was around 58mm, not the recommended 55mm.
Regarding star shapes this is probably as good as it'll get. If you get astigmatism rotate the primary and try again until it's gone. That's how I found the sweet spot.
Having owned that scope previously maybe I can pitch in a few things to check unless you have further modded it.
1_ Secondary is fine. No astigmatism there and the bond on the alu plate is very light. No stress.
2_ Primary is not clipped. Rubber just holds the mirror. No pinching.
3_ Focuser is as square as I could get it. Having said that this scope is very hard to collimated perfectly.
Good think is once it is it holds collimation very well. MPCC (type I) spacing is critical as well. From memory my spacing was around 58mm, not the recommended 55mm.
Regarding star shapes this is probably as good as it'll get. If you get astigmatism rotate the primary and try again until it's gone. That's how I found the sweet spot.
Thanks for the feedback Marc. I am using a different (larger) secondary now, as I had to cut the tube short to achieve DSLR focus - the original secondary once it was moved closer to the primary proved too small. I am suspicious of the secondary i'm using now (its from my GSO dob), and am considering getting a new secondary mirror and fixing it to the secondary holder that you originally supplied.
I also want to check the primary rubbers as i wonder if they are too tight following the last time I cleaned the mirror. Rotating the primary to find the 'sweet spot' is a good idea - thanks
