Andromeda Core Dust Lane Detail

[Menno555]

Cool!!!
I am waiting here till Andromeda pops up behind the roofs in like a month or so and then have a go too

Menno

[RonAM]

Thanks Brian. Your annotated image inspired me to learn and take a deeper look. I see there was some interest about color differences among the clusters. I applied an analysis using software by Prof Doug Brown (Physics) at Cabrillo College in California, Tracker.jar, LRGB region analysis. Qualifier: Adjustments were made in SharpCap livestack to approximate the visual seen in most images. Color in this case is thus not calibrated. However, a ratio of R and B to L values for one image can indicate if one is redder or bluer than another. Attached are screenshots of the G146 vs G205 clusters where G205 has a slightly higher ratio of red vs G146.

[oopfan]

Ron, a very nice tool! Yesterday I did notice a slightly reddish tinge to G205 as I annotated it. That is a nice Dob you've got. I visited the manufacturer's website yesterday. How is the tracking over the course of 15 minutes? You certainly had little to no drift over each 11-second exposure.

Brian

[RonAM]

Thanks. The main issue is field rotation after about 2 minutes. The rocker box tracks very well for visual observation for hours, but since it is an Alt-Az Mount, the whole field rotates.

So, all my deep sky work is done with SharpCap live stack, which aligns and rotates the frames as they are stacked. 10 seconds per frame is acceptable. I can run this for an hour, hundreds of frames, where only a small percentage of the image at the edges is affected. Over time you can see the effect of field rotation as a dark zone that develops at the edges. All the stars are aligned well. Without SharpCap live stack I wouldn’t be able to do this.

For planetary I run SER video at fast rates for 30-60 second quick captures.

Cheers,

Ron

[timh]

Hi Ron,

That is impressive! I always think that Dobs are underestimated for deepsky photography but - if you can put up with a bit of cropping - the image scale makes them really powerful for seeing the sort of detail that you are -- and anyway really good in terms of their sheer easy usability and for more compact objects such as planetaries and distant galaxies. An equatorial mount is so cumbersome by comparison.

I also really like the annotation - it adds a lot to have a scooby doo of excactly what you are looking at

With respect to things like gain and exposure per subframe I have always just guessed with my 10" dob (and AS1294 Pro) - usually 10s and gain 285 - but I really have no idea whether it is optimal (in terms of rotational blurring per subframe for any given object) and image dynamic range (e.g for galaxies like M94 where it is difficult to see detail of the core and at the same time see the outer faint regions). I have asked Robin whether it is feasible to create a Dob-orientated version of Brain to help with these things but it may be a rather big ask.

best wishes
Tim

[RonAM]

Thanks Tim - give it a go- live stack makes it easy.
My ZWO has such low noise at 5-deg C set point temperature that I can run the gain up to 350 if needed.

I attached a screenshot of my laptop screen showing the histogram during live stack.

I have so much light pollution that I keep the left limit bar close to the edge of the main histogram peak. I’d love to be able to move it a bit to the left - when I’m next at a dark sky site.

The mid-level bar is the one I’m careful with to get the detail I need without burning out the galaxy core. Move it left towards the histogram peak and faint objects are enhanced but the bright core will overexpose. Where you see it here works well for me.

Cheers,

Ron