Mono or OSC for stars?

Use the one that has the greater full well depth to get the best color and minimize saturated stars.

Carastro:
Either would do, whichever is most convenient.  

Carole

Nice to hear that, OSC is cheaper though, so in this case i should go with cheaper if both can do the job just fine, thank you Carol.

I am currently going through the paces of OSC vs Mono debates.    I've always had mono, but I picked up a color cam recently for my second scope, and for science really.       I can say stars get kindy wonky in OSC without enough dithering and integration time.  I'm not a fan, so far.      I haven't been able to get enough imaging time to really compare alot, but you end up seeing bits of the bayer matrix in the star core until you build up enough time.

I have mono cameras already and i know your point, but because of my limited time and bad situations i decided that i shouldn't use one or two mono only, and i decided that RGB stars are the best i can get with any target, so i thought that it is better to have that alone as dedicated and not shared with another camera for example mono for LSHO then RGB, no time, but then i have to decide if i also should do that RGB colors from one camera as whole or one camera with filters, and with unexpected weather and my life situations i can't trust i will always finish RGB filters on time or having all of them perfect.

It doesn't seem to make much sense to give up mono for OSC if all you want are better stars.  I would prioritize getting good narrowband data and worry about the stars later.  You can just get a good set of RGB filters and wait for a full moon to capture the stars separately.  There are ways to make mock RGB stars out of Ha+OIII data in PixInsight, too.

Theoretically, mono should give you higher resolution stars and more accurate colour but a well dithered and processed OSC image could be close enough to never know. In order for an OSC camera to begin to process a small star, it has to hit at least 3 pixels. Then in processing you should use a bayer drizzle instead of debayer for the most accurate stars possible. But that is theory. In practice I haven’t yet run into a situation where this mattered to that fine of a detail point. Maybe I eventually will. Use what you got and what is easiest. You can always re-shoot it. It’s not like re-shooting hours and hours of data.

Joe Linington:
Theoretically, mono should give you higher resolution stars and more accurate colour but a well dithered and processed OSC image could be close enough to never know. In order for an OSC camera to begin to process a small star, it has to hit at least 3 pixels. Then in processing you should use a bayer drizzle instead of debayer for the most accurate stars possible. But that is theory. In practice I haven’t yet run into a situation where this mattered to that fine of a detail point. Maybe I eventually will. Use what you got and what is easiest. You can always re-shoot it. It’s not like re-shooting hours and hours of data.

Processing is another story, i hope i can learn it good enough, but before i reach that stage i need to at least complete the setup and data stage first, with bad data or not enough data i will never have good results even if i spend weeks in processing, and when i saw or played with nice data it was really easy to process less headache, through 5 years or say since 2017 when i started i never get good colors or shapes of stars, i was able to have nebulosity nice enough, but only starless version will be amazing and nice, while stars are all bad shapes and bad colors, even with RGB filters, so i felt like i am not doing anything good even with mono and filters, and i see many images with OSC better than my mono with RGB, so it is all about my setup and data time that making things worse even before i start processing.

Again, i asked because some told me that for stars it is not necessary to have mono with RGB filters, even not necessary to have exact scope of main imaging one for LHOS as long i can dither and drizzle, so i can't afford third great scope and mono camera and RGB filters that size, my main wide field or average setup i will use for nebulae is my two 90mm triplet with 0.8x reducers, both are expensive enough even with discounts or offers i found before they are higher now, also both IMX571 i bought one is OSC and one is mono are great prices and they even getting lower, i still can buy that IMX571 mono at good price, but then i have to pay for 36"/2" RGB filters too, and that will force me to go with cheaper scope then rather than third 90mm + 0.9x, one mono is for L/SII and OSC is for Ha/OIII with dual band filter, then i am left with RGB either for stars or targets colors, if OSC it means i need filter wheel or drawer or simply only image RGB without HO, if mono then LSRGB which is 5 filters or 4 f no NB, i try hard that i use maximum 2 filters with any camera per night and finish a target in one night or two if possible, i once tried using my lens 135mm f/2 at F2 itself for 3 nights on Orion M42 capturing LHaRGB and data wasn't enough yet and wasn't good.

I have compared 533MM and 533MC on the same target with the same scope under similar sky conditions. Not only does the mono camera capture data faster, but the colour data is much easier to neutralize in processing and the colours themselves are more natural without an ugly green bias that requires destructive operations like SCNR.

The OSC green bias due to 2x green photosites in a Bayer array is a myth:
https://pixinsight.com/forum/index.php?threads/something-strange-happening-with-wbpp.20556/post-125367

If you are relying on SCNR for color calibration then something is not correct in your color calibration workflow. As an OSC user I have never had to rely on SCNR for color balance and in the rare cases I use SCNR it happens very late at my workflow for correcting small green tints which are probably due to wrong background modelling/neutralization from my side.

If getting RGB data for stars mean that you have to remove your mono imaging train from your scope, then I would immediately disqualify the entire idea. This will be a hassle for no benefit.

I have compared 533MM and 533MC on the same target with the same scope under similar sky conditions. Not only does the mono camera capture data faster, but the colour data is much easier to neutralize in processing and the colours themselves are more natural without an ugly green bias that requires destructive operations like SCNR.

The old idea that an OSC camera is "faster" at capturing a full data set is simply a myth. The Bayer filter results in tangible reduction in efficiency. I presume this thinking mostly originates from the old methods of imaging where you would image one filter at a time and refocus in between. Certainly those methods slow down aquisistion.

Those days are gone. When I image RGB data on my mono system I use a sequence which cycles through each colour one after the other. The focus is perfect acrossed all of them because of pre calculated filter offsets which the autofocuser adjusts repeatably during each filter change. So if clouds come in early I will still end up with less data, but it will be a perfect balance acrossed all channels.

No, i am not planning to remove the mono imaging from my scope, i will get a separate independent setup imaging train only for RGB, so i shoot all at same time rather than wait one sequence after another.

I already asked here about mono with filters against OSC, i still didn't decide anything, i can get a mono if that is the majority votes, i just need to be sure, as i read some told me they get nice data of RGB with OSC, even they use it for narrowbanding, which means that OSC reached a point where it can be used for not bad results, and many said that for stars it is not a big deal really, so if that worked for them then why not wit me.

I don't want to leave things for weather conditions, and doing cycle needs me to understand and set my equipment properly so i can use filters effectively correct way rather than facing issues and regret, i still don't know how to use the autofocuser and adjust offsets and such, i will get there sooner or later i hope, but i also try to see if i can shortcut few things so i don't end up with so many things to deal with, i have three mono cameras at 4/3" with two of them are exactly same sensor and one is a newer model, and also two APS-C sensor with one as a mono and one as OSC, i am thinking about third APS-C of same sensor model but not sure which will be, a second mono or a second OSC.

Joe:
I am no imager  like you guys here on Astrobin, I try to be but I am not. 

That said, in my opinion, both OSC and mono cameras produce outstanding images. Look here on Astrobin and you will see.  

The bigger question to you is, how much do you want to dedicate to the image?? 
Meaning, mono should be better based on all your pixels are the same color, you get more good data with mono.  So, how much money, how much time, how much effort do you want to throw at the image?? 

It is basically double the money for mono, time and effort - I use NINA to capture and Pixinsight to process.  My computer disk space limits me to 140 images of an OSc camera because Pixinsight WBPP takes about 100GB to process and up to 8 hours.

Consider file sizes, IMX 571 is 50MB per image, IMX 533 is 17MB per image on an OSC camera.  My laptop is an I5 Dell with 8GB memory.

My opinion, with a mono camera it will take 4 hours to take an hours worth of shots in four filters, I call this a one hour shot, again my opinion, it will look better than a one hour shot with an OSC.  Better color and detail.   How much better, you have to decide.

Me, I have two OSC cameras, a QHY533C and a Moravian C1X26000C.   OSC is good enough for me.

That is my take on this,    Joe

Hi Joe,

Let's put it in a simple way or as much i can

I was asking this because i only focus on stars, the colors, i also focus on the shape of the stars so i might think about a quad or Petzval which is corrected field scopes, so i don't worry much about back focus and coma or field curvature and whatever shapes, i will check about tilting too, but that is one story, another story is the colors of stars, and the only way is using true RGB colors and not narrowbanding and correct it later, for RGB there are two ways, either OSC with its Bayer matrix already for RGB, or mono and RGB filters, so simple as that.

I will make setup that will take only Ha/OIII/SII and maybe L by own setup, then i will plan to have a separate setup only collecting RGB, and for that i don't ignore OSC, if i will use OSC i will expose it for the entire time of what i expose Ha/OIII/SII/L, if i have 4 hours i will expose OSC for 4 hours too, rather than exposing 3 filters for 4 hours total so each will have less than 2 hours each for sure, so let's say how much better it will be for 1 hour each RGB filters vs. 3 hours full OSC? i will not compare 1 hour of OSC to 2-3 hours of RGB filters, but what about 6 hours of OSC for example vs. 3 hours of RGB?

Again, i didn't decide anything yet, this will be only about RGB, nothing to do about narrowbanding or even Lum as i have a mono for that already, and might also use OSC for dual band, many did it already nice enough, but let's say if i decided to go with second mono IMX571, then i will have two IMX571 mono and one IMX571 OSC, then tell me, what i can use that IMX571 color for? And how to use those two IMX571 monos, 3 filters here and 3 filters there??!!!

Joe Linington:
So let me see if I understand. You have 1x571 OSC and 1x571 mono and want to build a 3rd rig. That’s easy. Mono. Set your OSC to collect stars and use the other 2 for SHO or LRGB. Full set of filters in each. And then when you can afford the upgrade, sell the OSC and go 3x mono with full filters. The flexibility would be awesome. Heck, you could have only 1 set of filters and 5 position wheels with that setup. Red and Ha in one scope, Green and Sii in the second scope and Blue and Oiii in the third. Add a lum (UV/IR) to each one because they are cheap and off to the races. You would change filters so seldom that you could save even more with manual filter wheels.

You may have just planted a plan in my head that will give my wife nightmares. I already have 2 mounts and 2 imaging computers and certain scopes are pretty cheap. Now to find a really good deal on another used 294m.

Ok, as cameras, those are the following i have as cooled only from oldest to newest i got [i won't mention non cooled]:

QHY163M
ASI1600MM-C Pro
QHY294M-Pro
IMX571 OSC
IMX571 Mono

I can buy two more IMX571 mono in future, i mean i can buy one later within 2 months if i get the budget and the third one i can buy maybe by end of this year if everything is ok, without selling that OSC, but as long i have OSC i was thinking about why not use it then, either for stars RGB or Ha/OIII from a dual band filter, but sounds your idea about three mono is nice, i can do that with my already 4/3" three cameras making QHY294M as the main one, in fact i wanted to have OSC from many results i see around so i did, and wasn't sure if i should add another OSC or not.

I also have many DSLRs and one Sony Mirrorless camera, non modified for astro, i use them for photography, was thinking about using one for RGB stars, but sensitivity and cooling will affect maybe under my LP sky and heat, it is an idea, but i like to go fully dedicated as much i can.

The scopes i have that i will use for DSO are the following [try from oldest to newest]:

ST80 [i was using it, but not anymore, i will use it for solar or for guiding
Meade 8" F/5
GSO 6" F/4
Askar FRA400
TS Optics 90mm F/6 APO triplet CF [Two]
Apertura 60mm F/6 ED doublet
Sky Rover 60mm F/6 ED doublet
TS Optics RC 10" F/8

So i am thinking either third 90mm with third IMX571, or 102mm doublet with third IMX571 [but i will use 0.6x reducer here], or smaller such as 70mm F/5 Petzval and 294 OSC, and in later future maybe 2024 who knows i will add something to 10" RC, maybe 10" Newt or 12" Newt, but whatever i decide on the scope i need to use i should also decide first on what camera to be used with, and since i saw some with say 3-5 scopes all at once i couldn't sleep or stop until i try to finish my multi imaging setup as well, for narrwobanding 3 scopes or more, for broadbanding 2 scopes could be enough.

Joe Linington:
That is one heck of a collection. I’m not sure I’m remotely qualified to offer an opinion but I’ll take a look later tonight at my computer. What reducers and correctors do you have?

I tried to collect them at best i can within 5 years, i started in 2017 with one mount which i still only have and 1 cooled camera and several filters and only ST80, by 2018 i bought both the Mak 180mm Skywatcher and Meade 8" F/5 at same time with good money brand new, then i waited until 2020 when i started to add many items as extra cooled cameras and scopes also, so it wasn't done in 1 year, i saw some who bought more than me or say less but much much more expensive than what i have in less than 2-3 years, so it doesn't matter about the collection, i was lucky to buy most of those at discounted lower prices brand new.

The following reducers and correctors i have:

Hotech 1.0x field flattener
Skywatcher coma corrector F4 Aplanatic
Stellamira 0.8x reducer, two of them for my two 90mm, the reducer is designed for it
Stellamira generic 0.8x reducer [i don't know which scope i should use it with]
Askar FRA 0.7x reducer for FRA400
Two Sky Rover 0.8x reducers for both 60mm ED doublets.

* My plan is to get 0.75x for my Newt, so 6" F/4 can turn into F3 if the scope is a true F4 one [in a forum some said it isn't], and also a reducer for my RC 10", but i am not sure which flattener for RC if i have to, and my new plan if i buy a third rig is either 0.8x if i buy 90mm or 0.6x if i buy 102mm.