Two views of NGC1365

ChrisV (Chris) · #1 12-12-2018, 10:25 PM

My first image in the DeepSpace threads. NGC1365 in Sydney suburbs with ASI071

The first is with the 80mm refractor, 9 hrs of 2min subs. I originally posted in beginners, but have reprocessed.

The second with with the 8" F5 newt, 10 hrs of 2min subs. This blew me away, as I saw a pile of faint fuzzies with the wider field on the refractor. But then I saw nearly as many with the smaller FOV newt - although they might not come out well with the jpg squeezing.

Both captured with APT, processed with PI. Comments please - an I over/under-processing, etc etc? Just don't say more subs - it's taken me since the start of October to get this far with the bad weather and work trips which just managed to coincide with good AP nights

Edit: added astrobin links
https://www.astrobin.com/380803/0/
https://www.astrobin.com/380804/

multiweb (Marc) · #2 13-12-2018, 07:48 AM

Two very nice shots. Great colors and details.

That's one galaxy I still want to image. Haven't had any opportunity yet.

glend (Glen) · #3 13-12-2018, 09:00 AM

Well done Chris. I prefer the Newt image if I had to choose, nice and crisp, without any colour shift. Can you tell me what is causing the artifact in the refractor image....if you have a look at the bright orange star closest to the galaxy in the 7pm position (from ngc1365), it appears to have a small black box outline in the centre of the star. At full resolution on the Astrobin image the little square appears as a small red house with a blue door -I swear that is what I see when I zoom in on that star. Is this some sort of PI thing, or is there a dyson type sphere being constructed out there?

RickS (Rick) · #4 13-12-2018, 09:05 AM

Nice pics, Chris, and the level of processing looks good to me. Might be worth trying to register with distortion correction and see if that helps improve the colour of the stars in the corners.

Cheers,
Rick.

ChrisV (Chris) · #5 13-12-2018, 09:14 AM

Thanks Marc Glen and Rick.

The aberration is probably a PI thing from when I did some sharpening. Either the mask I used to protect all stars wasn't quite right or I was too aggressive with the sharpening. I'll go back and have a look. I spent ages processing the wide view image, but not long on the newt image.

I'll have to look into distortion correction. I like the sound of that. I just ordered a new motherboard and CPU - 8 core 8 thread - so hopefully preprocessing with local normalisation etc will now take less than forever and a day with 300-400 subs

Edit. Oops the artefact is in the refractor image. It's still due to the PI sharpening. Same reason.

furgle (Adam) · #6 13-12-2018, 09:17 AM

This is really nice. I like the wider view. I never think to see what's around an object before hitting it with an SCT.

Placidus (Mike and Trish) · #7 14-12-2018, 08:44 PM

The narrower field image is absolutely fine. Most enjoyable.

There are obvious processing artifacts in the wide-field shot, but the underlying data are excellent. Not over-processed, just some fixable glitches.

One thing (among many) that can produce the odd funny pixel like that is if 16 bit integer data have wrapped beyond 65535 counts. That is a bug in the software rather than a user error.

Atmos (Colin) · #8 14-12-2018, 11:33 PM

As much as I enjoy the plethora of galaxies in the wider field I do prefer the second one. Not the easiest of galaxies to image as it isn’t big but you’ve captured it well

ChrisV (Chris) · #9 15-12-2018, 10:36 AM

Thanks Colin Mike Trish and Adam.

That's interesting about the PI artefact when you get to the 64k ceiling. I tried several versions of the star mask to try and get rid of it. Long Christmas break coming up so will have time to have another go at it. Maybe a clone stamp hammer approach ! But that's really fudging data

I was really pleased with the newt images. It had a problem with some sort of distortion. I thought it was coma, but after reading Multiweb's thread about a similar thing - I realised it was tilt in the focuser. I rushed off and got a moonlite which made it really easy to adjust and fix. After that I found that I could've done the same by just sticking shims under the stock focuser - which I've now done. Looks like I have a moonlite sitting around - maybe use for the teleskop-express carbon fibre newt I want to get ...