M81 Bode's Galaxy with over 22 hours of data

[Menno555]

I had already chosen M81 last year to collect a lot of data and this is the result. And I'm happy with it
Couldn't do much last year because of the very bad nights, but that was more than made up for last week.

It's a total of 22 hours of data, 270 shots with various exposures (from 120sec to 600sec) and with almost all my filters (Baader IR/UV Cut, Baader Neodymium Skyglow, Optolong L-Pro and Optolong L-eNhance).
And then several hours to figure out the right ways to put it all together and edit it. In the end I first stacked all sessions separately and saved them as FITS. These all edited separately in SiriL and saved as FITS again. Stacked the resulting FITS again in SiriL and processed the final stack in Photoshop.
And this time I didn't have to resize: more than enough data to keep it in the original recording format and leave a nice, big M81

The full 3000px result of that can be seen here: https://i.ibb.co/869926X/M81.jpg

Bortle 6/7
Meade LX200 8" f/10 ACF OTA
Ioptron CEM25EC mount (no guiding)
Zwo ASI071MC Pro camera
Captured with SharpCap Pro
Stacked with SiriL
Edited in SiriL and Photoshop.

[timh]

Really good colour, smooth but finely detailed image with a real sense of depth in that Menno. An artistically attractive image. It's interesting - your strategy with galaxies is almost the exact opposite of what mine has been up to now. I go for moonless - darker skies if possible, no filters - to try and see the fainter outer galaxy extent but probably end up blowing out the centre and ending up with a more posterized look. What quality did you find that the extra time spent - 22h as opposed to say 8h - improved the most?

Tim

[Menno555]

Thanks Tim!

I have no means of transportation (or driver license for that matter), so I'm bound to my Bortle 6/7 sky. So with the narrower filters I can do longer exposures but with the LP filters and IR/UV Cut filter, I am limited. I did try your strategy but for the bigger galaxies that doesn't work. Have to stretch too much then and that look, I don't like That strategy only works for a FOV with a lot of faint galaxies for example.

So to counter that (a bit), I go for integration time. In this case the most improvement was the noise. I can create around the same look with less time but only when I stretch more, use more noise reduction and resize the end result to (a lot) smaller.
Now with the 22 hours I had to stretch way less, way less noise reduction and no resize. So more "true to life".
The 22 hours didn't do much for small(er)details though: I'm bound to the oversampling my equipment combination causes. I did look for camera's with a lot larger pixel size (9µm would be perfect) but those camera's are way out of my price rangen

Menno

[timh]

Thanks Menno for that answer. I am probably kidding myself that I will be a very mobile observer now with 'the VX12 leviathan' to drag around - in practice - 95% of my imaging is anyway from home. Certainly the SNR you have achieved from your home site looks great and something worked well.

On a philosophical note it is probably all too easy to be overly influenced by the astro "rules" that one reads online and in magazines rather than just trying things out to see what works. Some widely accepted wisdom does just seem to be prejudice. My particular examples at the moment are ..

1) "Don't image with a mount loaded at above half of the maximum load value for visual use". In fact - under clement conditions (not too windy) - the CEM70 appears to work and guide fine even at slightly over 2/3 of maximum loading.

2) "There is normally no point working at an image scale less than 1 arc sec per pixel because you will be oversampling - ~ 1.5 is normally adequate to sample the seeing ". In fact - having now dropped to a scale of < 0.8 arcsec/ pixel with the VX12 - on two observing occasions at least I seem to have got to a (linear debayered) image resolution at about FWHM 2.0 arcsec and, correspondingly, to be discerning sharper detail. So my past assumptions about normally being seeing limited at 2.5- 3 were probably just wrong - and therefore, more often than you might suppose, a scale of 0.8 isn't oversampling ?

Similarly with galaxy imaging and (as has been my habit) religiously avoiding moonlight. On Monday I imaged M106 using the VX12 when it was no more than 40 deg or so from a bright half moon. True the fainter parts were washed out but _ even after just 25 min - the view of the core was excellent and resolving detail that was new to me. So - since we are due a few clear but moonlit nights - I might take a leaf out of your book and go for a deeper SNR image of a couple of galaxy cores rather than await conditions that may never happen.
Tim

[zerolatitude]

That's a very nice image.

Good to see someone else is also trying different filters for OSC

Agree with Tim - there are far too many "rules" flying around which have not been empirically tested with todays equipment.

From a B9+ perspective (sky mag 17-17.5), it is near impossible to image galaxies without some filter and a long time (though I've only gotten to 12 hours so far - am now inspired to go for 22

Your approach is interesting. Never thought of processing the sub stacks before integrating them.

I've so far tried just stacking all the subs - UHC and 'Moon and Skyglow' - in one big lot. I'm currently trying out extracting the blue from the MSG and combining it with UHC red and green.

Will try out your approach as well and see where it gets me.

Thanks

[Menno555]

Thanks Tim and Zero

For me the "not following the rules" originates from a blissful lack of knowledge and also a kind if stubbornness.
It's all about just trying and see what happens, experimenting with the means I have.
And my mindset is simple: there are no rules. Just try and see what happens.
That's why I am able to do 600sec exposures at 2032mm focal length with no guiding. Experimenting, trail and error and despite the "rule" that it's impossible, succeeding in finding a way to do it

And all the theoretical things like the arcsec/pixel scale or SNR and so on ... I understand the basics of it (a bit) but I simply don't use it. I find an object that looks interesting in Stellarium, see if it's not to faint, guess what kind of filter can be useful or interesting, set exposure times, gain and offset by gut feeling (incorporated with things I learn here) and see what happens

Menno

Edit: I just remembered a topic I started on Cloudynights 2 years ago. Essentially it's about those "rules", being rigid I called it. It did stir up a lot, a lot of reactions and opinions. It is a nice read I think and gives a good insight on what people think when it comes to "rules"
https://www.cloudynights.com/topic/7178 ... d-advises/

[zerolatitude]

Still going strong. Apparently your image is impossible because filters cut out most data from galaxies

https://www.cloudynights.com/topic/8162 ... bortle-78/

[Menno555]

Payed a visit and reacted too.
But indeed it shows that there are some "strong" opinions on what almost must be done. It almost isn't advise anymore ...

Menno

[timh]

Hi Menno, I finally got round to reading that CN thread - really quite interesting and entertaining. Now I must admit that I am probably your polar opposite - the ' ' anti-Menno ' if your like because I just love numbers and calculating (to the level that I can understand it anyway). It's because my background and training is in physically-based science and pre-calculation just an essential part of experiment design.

But back on the CN thread - I think it's mainly just all about poor communication and defining questions and answers more precisely? Someone (me for example) might think that you won't see the IFN at Bortle 6-7 -- and be discouraged from trying at all - whereas someone like you (or possibly uniquely you ) proves that as a matter of practical fact you really can! So if someone states on a forum that you won't see the IFN in such a bright sky then they would be wrong - if, on the other hand they simply said that it would be difficult and you won't see it very well - then that would be true. I think that sometimes the nuances get lost in over simple answers?

Tim

[Menno555]

Hi Anti-Tim

True, I'm a hands-on guy who acts on gut feeling. At my work too. I did some start-ups for lines in the pharmaceutical field. Of course I did study for that, but there where others first do complex studies and calculations on for example a workflow with materials, operators, equipment placement, and so on, I do "see" it already while being in the empty space where is has to be build. My gut feeling tells me what the most logical material flow is, where reactors best can be placed, what and where possible safety hazards are, how many operators there are needed, and so on. But being it in the pharmaceutical field, calculations and documentation are mandatory, so I tell how it works best and my colleague translates that into writing

And yes, semantics are a part of it. And also "hear say". Someone heard/did read that you can't get faint(er) objects with a slow scope with shorter exposure times, they agree and repeat that statement as a kind of fact because they have a slow scope. And then indeed like you pointed out: instead of saying "It's difficult", they say "It's impossible".
Personally I don't care but I do care that other starters are missing out on things they can do and learn this way.

And it's not uniquely me There are more than enough others like me but they keep "silent" because they know that their views are not "popular", despite their results. I've been called a liar for example with my unguided 600sec exposures at 2032mm focal length with my relative simple equipment, I did make it up just to be interesting.
So when asked advise, I'll indeed will always point out that certain things have easier/better ways of working (starting with a Dobson for example, is easier then starting with a long focal length SCT like I did ) but I also point out that experimenting outside the "established ways of doing things", can deliver good and sometimes surprising results.
But most of all: do what you like. You for example like to play with numbers and calculations and I don't. Do we miss out of some things because of that? For sure. But as long we have fun with it and discover things for ourselves, that's what counts.