WIP, my first M101, featuring Holmberg IV

[Mike in Rancho]

Can you believe in a few years of AP I've never shot M101?

I really don't find it super appealing, and perhaps even feel sorry for it, since it looks like it has a broken leg and all.

After a first framing and star-shape (still wonky) test on Thursday, I rotated the camera and picked up a good 4 hours LRGB in 3:1:1:1 ratio, 1 hour pre-flip and 3 after, tracking all the way down to 50 degrees. The LP was worse down there, but maybe not by a ton, at least if I can trust the SQM results from ASTAP.

The data is still a bit noisy and gradient-y, though (very) aggressive Wipe with galaxy mask handled all that. Still, it may be a bit harsh on the stretch. I'll try to get another 4 hours soon to double the time, which will hopefully provide more ways to work with this.

My reorientation was done to see if I could capture Holmberg IV, just down and in from the bright blue star 86 Ursae Majoris. This doesn't appear to be seen (or at least mentioned) very much, certainly not as much as Holmberg IX, which everyone photographs next to M81. This one is a little bit brighter and easier, but probably falls out of the FOV for most M101 images.

M101 4h LRGB ST9 2A.jpg (453.22 KiB) Viewed 5036 times

[admin]

Forget Holmberg IV; NGC 5474 looks amazing here!

[fmeireso]

Looks good , Mike, very good even, bit small perhaps, at was F was this taken?

Me on the contrary find it an attractive target. One reason, it is fairly big, one of the few i can take good with my 130 mm at F/7. Sofar i did not shoot it with it though, i allready have picture (not the greatest) in a 102 mm.
But it is still on my wanted list, i wanne take a long OSC shot and and Ha shot to make the Ha regions glow. Maybe something for next year, i think it needs quite some integration time so it really stands out well. Just my thoughts...

[Stefan B]

Good one, Mike! I've never seen the FOV that wide and didn't know Holmberg IV. Thanks for that.

Hope your weather is better than mine. Just aweful. Guess I just hope for the second half of the year

Regards
Stefan

[Mike in Rancho]

Thanks Ivo, Freddy and Stefan!

With the 0.95x corrector this puts me at f/3.8 and 585mm, across APS-C size sensor. But for this target yeah that's still looks pretty wide.

I picked up another 3 hours last night so have 7 now. PI spent an ungodly amount of time stacking it all, even though many masters and cached data had been generated stacking the first 4 hours. I will be test-driving 551 on it to see what I can make.

After the cold and wet winter, I just had a brief window of typical SoCal, not quite summer but leaning that way -- clear, good seeing, 65 degree nights with little temperature change (I didn't have to alter focus at all), and terrible light pollution. Humidity was high and transparency wasn't great, but it's still spring after all. Usually this time of year has cloudiest nights (i.e. "June gloom"). So, just waiting to see what summer brings - cross fingers the usual 15% humidity and no rain for 5+ months.

I'll have to take a look at what's going on for the continent, sounds like a bad prevailing weather pattern though.

[fmeireso]

Yeah, stacking time...

Only for that i upgraded my pc recently. I was running fine with a Ryzen 5 3600 but i changed it for a Ryzen 9 5900x. Needed an BIOS upgrade and
a cooler. The cooling solution was more euro then expected. I have a tiny case so it was a bit of a challenge to find one that was a bit up the job and still fitted in my case.
Anyhow my stacking times are cut in half. A big one (for me) of 267 subs taking the Ryzen 5 3600 2 hours and 20 minutes is now done in 1 hour and 4 minutes in PI.

For processing in ST it does not make that much of a difference. Some modules do work faster indeed but i would not have upgraded if it was only for that.

[Mike in Rancho]

Wow Freddy that's a big improvement in speed. Way to go!

Though your older AMD was still faster than my CPU is. Now your files probably do need more stuff done, like debayering, but for my 7h stacking here I had around 70 subs each of RGB, and 420 subs of L. So, I guess 630 subs overall.

I'm still feeling it out, but I did this one all in 551, and for this try I only binned to 71% too. I think the extra time helped nicely. OptiDev'd in a slightly different way, not blowing up the targets or the stars nearly as much. But even so, I think I started to pick up some of the really outer faint swirls about M101. Depending on if this is viewed against a bright or dark background still dictates how much can be seen versus looks like too much pesky noise though, as well as if the browser is globally upscaling.

Holmberg IV is still showing decently well though, and after further inspection based on Ivo's comment, I now really like having NGC 5474 in there. Checking against reference images, I really like that it picked up the details of those little blue dots, even at my paltry 585mm.

Now this has been since crunched down to 1600 pixels wide (CN max) and jpg at under 500kb, so the 4300 x 2900 tiff does shine a good bit better, albeit at 72Mb.

M101 7h LRGB ST9-551 71bin 5B.jpg (489.41 KiB) Viewed 4894 times

[fmeireso]

yep, still looks better this one, nice coloring. I like it.

[Mike in Rancho]

Reprocessed the original 7 hours, similar but slightly different and perhaps more stretch but a bit less saturation. I'm still not completely down with deringing, though much of that is likely just learning, but that'll take a while as things seem more intricate and based on prior actions. For example with bad ringing and shadows I've been able to improve by removing samples or just going to single-sample SVD, or doing a Restore to linear, wiped and just altering up the processing a bit leading into SVD. Still, I sometimes still get harsh ringing on the brighter (usually larger than the sampling sizes offered) stars, and further, the deringing sometimes works on some stars while others seem completely unaffected. But, overall the results are pretty good and I can usually get most artifacts cleaned up with more targeted deringing via a no-shrink Shrink - though some star colors seem to blend the deringing better than others.

I am torn on what to do with this data. Sadly I have only been able to get one hour on target with the SN on the night of the 22nd (up to maybe high mag 10 or low mag 11!). The marine layer rolled in at just past 11 pm that night, has been here ever since, and shows no signs of going away.

So I processed somewhat similarly (I can do better), but the 1 hour integration is so poor that any kind of blending creates a mess. Unless I just use a supernova mask for the layer module, as I did here. Now I did change the layer mode to lighten, so is perhaps less cheesy, but...still too cheesy?

M101 7h LRGB ST9-551 71bin 6A blend SN.jpg (470.88 KiB) Viewed 4763 times

I'm thinking of tossing my extra hour into WBPP to get a full 8 hours. It's extra data, so why not? Other than that stacking will likely take 6 hours with all the bells and whistles turned on. But, rejection and averaging will disappear the SN I'm sure.

Is there any other good way to have a nice M101 with the time I have, and yet also get the SN in there?

I am thinking of improving my 1-hour SN processing to be more identical to the main integration, albeit far noisier and less detailed, and then maybe try a blink. A gif will degrade the details anyway, so maybe things won't be so noticeable? Or maybe I can forego color and just try things in grayscale, which might hold up better.

[admin]

IMHO, as long as you disclose what you did, I think adding the supernova using a mask is absolutely acceptable (and, yes, lighten is probably the way to go ).

From a documentary point of view, you are not "inventing detail" in the object as it is today, though you are "inventing detail" in the object as it was when you recorded the other data. It's a nitpicky thing, but full disclosure circumvents any objections someone might have.

In general, de-ringing after deconvolution is a last resort operation (as explained in this post), so if you can avoid it entirely by choosing good samples and, pulling back on the number of iterations or - sometimes overlooked - improving your dataset or stacking settings, then that would have a strong preference.

With regards to ringing of very bright stars, are the star cores in your dataset "pure white" in the dataset, or are they "approaching" white?

Ringing with regards to "improving your dataset or stacking settings", can also be caused by aberrant data that breaks linearity (can be due to stacking settings, non-linear response of the camera, or stacking data from multiple nights with varying seeing, transparency or focus conditions).

Throughout deconvolution, the dataset is assumed to be linear; one more brightness step corresponding to one more measured packet of photons. For aforementioned reasons, this assumption can break down...