M106 Ha

[Rodd]

I am not sure if my Ha data is "normal".  5 sec subs reveal no stars to use for framing and alignment.  Nor do 10 sec subs.  I have to take 30 sec subs to achieve this.  This seems odd to me.  Does anyone else have this issue (I am shooting at 1960 mm.  I do not notice this when using refractors and a smaller focal length).  This leads to trouble registering the subs.  I had to adjust PIs star alignment parameters very aggressively to register the subs--even when at least 20-30 stars are visible in each sub.  This is a 72 300 sec subs stack.  6 hours.  I plan on collecting a bunch more to bring out the faint Ha knots along the outer rim of the galactic disc, which are just faintly visible on my processing computer, which tends to be a bit lighter than most screens.  So the other question is, can you see the faint outer band of Ha regions?  Much of the Ha haze between definite Ha structures in the core will be removed when I clean the stack of unwanted red signal.  But that can't be done until I have an RGB image from which to extract a red channel (not sure if it can be done using a red stack alone.  That is a question I have been pondering for some time)--so the third question.

C11Edge with .7x reducer and ASI 1600: 72 300 sec - Bin 1

Bin-2

 

Edited March 30, 2023 by Rodd

[Elp]

I get the issue at F6.3 reduced at 1000mm FL, my plate solve settings usually need to be set at 20s centre time for the camera to get enough saturation to the sensor (yes I COULD plate solve with a luminence filter or without but that would mean more manual effort).

I also get the registration issue because the star FWHM isn't as good in my C6 as it is in my refractor.

[Rodd]

1 minute ago, Elp said:

I get the issue at F6.3 reduced at 1000mm FL, my plate solve settings usually need to be set at 20s centre time for the camera to get enough saturation to the sensor (yes I COULD plate solve with a luminence filter or without but that would mean more manual effort).

I also get the registration issue because the star FWHM isn't as good in my C6 as it is in my refractor.

Interesting. I guess the aperture difference between my refractors and the 11” Edge overcomes the optical design differences because my fwhm in the C11 is always smaller than the refractors. Thank you for the info!

[Elp]

I think camera pixel size also makes a difference. My last narrowband sessions I compared my 360mm refractor to my reduced SCT, the SCT data though more detailed, seemed much less bright, even though the aperture is much larger and f ratios are similar between the two.

[Rodd]

6 minutes ago, Elp said:

I think camera pixel size also makes a difference. My last narrowband sessions I compared my 360mm refractor to my reduced SCT, the SCT data though more detailed, seemed much less bright, even though the aperture is much larger and f ratios are similar between the two.

That is interesting. At similar focal ratios the larger aperture should provide faster  signal  building for sure.  Smaller pixels are less sensitive. I don’t realize they impacted signal that much

[Elp]

My 183 has one of the smallest pixel pitches you can get I think. The hyperstar manages to saturate it better, but not as quick as the 294.

[Rodd]

30 minutes ago, Elp said:

My 183 has one of the smallest pixel pitches you can get I think. The hyperstar manages to saturate it better, but not as quick as the 294.

I would very much like to get a large pixel sensor for the C11Edge....12 um.  A pixel size that would put the pixel scale around 1.6 or so.  With my sky, I can't really see a difference between .4"/px and 1.5"/pix , hence the reason I can bin 3 and not see a resolution reduction.  I guess there is an argument to be made that there is no difference between a large pixel and a bin 3 smaller pixel.  Others would no doubt be much better able to disect this question

[ollypenrice]

I don't know about the framing or alignment (which I would just do using another filter) but this Ha result is sensational. Love the two jets.

Olly

[Rodd]

16 minutes ago, ollypenrice said:

I don't know about the framing or alignment (which I would just do using another filter) but this Ha result is sensational. Love the two jets.

Olly

Thanks Olly.  Regarding the alignment, the software says it can’t find enough putative star matches. So even if I use a broadband filter as a master to align all subs, the Ha subs fail because PI can’t “see” enough stars.  I managed to get them to align, but I had to use settings that may compromise the accuracy.  It didn’t seem to.  But the PI alignment  tool doesn’t seem to be designed for data that is less than optimal.  I have had this trouble before with Ha. 

[Rodd]

19 hours ago, ollypenrice said:

I don't know about the framing or alignment (which I would just do using another filter) but this Ha result is sensational. Love the two jets.

Olly

 

23 hours ago, Elp said:

My 183 has one of the smallest pixel pitches you can get I think. The hyperstar manages to saturate it better, but not as quick as the 294.

The final Ha stack--as a stand alone image.  12 hours, recalibrated using light panel instead of sky flats (wreaking havoc with the C11 Edge data for some reason).  Background is much better, and faint rim emissions are more prominent,  as is the "third jet"-which is really just a segment of the primary jet that has detached.  I don't remember seeing this feature before.