IC1805 heart nebula. Long total exposure

[timh]

Here tried to get a 'definitive' good image of this object (the running dog part) by combining my 2021 data with further S2, OIII and HA data from this year. So finally a total of 21.5h (1.25h OSC RGB, 8h of S2, 6.5h of O3 and 6h of HA all at D = 200mm, F4.5). The additional exposure helped to better define the relatively weak S2 and OIII signals.

SW PDS200 F4.5 (0.9X reducer) and ASI294 MC and MM cameras at 4.63 uM pixel size (1.05 arc sec/ pixel) -using an Astronomik 6 nm filter for O3, Optolong 7 nm filter for HA and an Optolong 6.5 nm for S2. Mount was a CEM 70, guiding with PHD2 via a 80, 400mm guidescope plus ASI 120MM camera.

Capture was with Sharpcap 4.0 -- filtering on FWHM and brightness in livestacking with autofocus every hour or so. Processing in PixInsight. Starless NB and RGB images were prepared using StarExterminator 2.05, combined using Pixmath, stretched using EXP, LocalHistogram Equalisation and curves with RGB stars re-added at the end. The starless HA and S2 images were both bright enough to slightly improve by deconvolution before compiling into the NB images.

One trivial point you may notice is that the brighter stars exhibit 8 rather than 4 diffraction spikes. This reflects one hazard of combining images over years. In 2021 I must have rotated the Newtonian tube to achieve 3 D balance to a slightly different final position than in 2022!

Tried HSO, OOH and Hubble SHO palettes as below .. here I think that OOH looks nicest while SHO has the best information content?

link to full res data https://www.astrobin.com/2cers7/I/


Tim

[oopfan]

Hi Tim,

Well I think that all three are spectacular! I've grown very fond of HSO.

I read your paragraph regarding 8 spikes versus 4. I think I have a solution. A question first: Am I correct in assuming that you acquired an RGB stack (for the stars) for each session and then combined them? If yes, then how about choosing only one RGB stack to combine with the star-removed NB stacks? That way you are assured of only 4 spikes. That assumes that StarExterminator does an excellent job of removing stars and spikes from the NB stacks. If it doesn't then you are suffering from "bleed through" which means that my solution won't work.

Great work!
Brian

[Menno555]

VERY detailed captures Tim!
SHO indeed shows the most info IMO.

Menno

[timh]

Thanks Brian and Menno,

Yes I am pleased with these images- the satisfaction of exploring the limits of what can be done with the skies, the SW PDS200 and the ever improving processing software.

Brian, your comment forces me to fess up. All the RGB information is from a single session in Dec 2020. Back then I hadn't really mastered the telescope and while the colour information was fine the FWHM and star shape across the frame wasn't. So I transferred the luminance from the good O3 NB data to inform the star shape while retaining the RGB colour - and yes there were two O3 sessions combined (one from Jan 2022 and the other from Nov 22) that were combined and clearly I must have rotated the telescope inbetween resulting in the offset spikes. And of course you are also right that I could fix it by just using one of the two O3 sessions.

It is a bit of a cheat because the relative luminance/ size appearance of stars only reflects that at ~ 500 nm rather than across the entire visible range. Nevertheless - to my eyes anyway - any differences are so subtle as to be negligable.

Tim