mono (rgb filters) to colour ccd any thoughts

[iwols]

Just wondered if anyone had gone this way and what their thoughts were thanks

[iwols]

hi all presume from the views /replies no one has gone this way?😁

[Clarkey]

 

On 13/11/2021 at 14:30, iwols said:

what their thoughts were thanks

Why would you want to do this? I can understand narrowband filters, but limiting to RGB on a Bayer matrix does not really make sense. You loose all the advantages of OSC and mono. If you want to limit the data just process the RGB channels separately.

Or am I missing something?

[scotty38]

I assumed the OP meant a move to OSC full stop. The RGB filters just being more info to what they used on the mono camera rather than what they will use on OSC.

I also assume it's really a move to CMOS rather than CCD though.

Edited November 15, 2021 by scotty38

[CloudMagnet]

Moving from mono to OSC is quite a big decision if you have already invested into a filter set/filter wheel as they will mostly become redundant. You also then need to look at the expenditure of new filters, this could be a light pollution filter and a dual/tri narrowband filter to collect OIII and HA at the same time. These don't come cheap and likely won't match up to true narrowband imaging with mono.

On the other side of the argument, the ease of OSC camera does make life enjoyable. You can finish an image on one night, rather than doing 1 or 2 channels, then needing to wait a couple of weeks for the next clear night arrive to get the last one. You also don't need to worry about multichannel processing.

[Clarkey]

1 hour ago, CloudMagnet said:

a couple of weeks

This would be better than my current run of clear nights. Autumn tends to be once per month at best!

 

10 hours ago, scotty38 said:

I assumed the OP meant a move to OSC full stop. The RGB filters just being more info to what they used on the mono camera rather than what they will use on OSC.

OK I understand now.

I currently image in mono, but due to the poor weather I am seriously considering OSC. I currently have a 600D which is OK, but I am thinking of a new astro OSC. I have not done it yet - but it is certainly in the back of my mind.

[tomato]

I don’t think it would make any sense to go from a mono CCD with filters to a OSC CCD, but moving to a modern CMOS OSC is a different story. 
 

My own view is that the sensitivity and performance of the latest CMOS sensors, plus modern dual band NB filters and ‘fast’ optics, makes this a viable option in the cloud plagued UK. I am in the process of doing exactly this with my  setup.

If your goal is premium images with integration hours in double figures, CCD or CMOS mono will deliver but be prepared to produce only a handful of images per year if based in the UK. If you want to get something decent from a single session, then it’s worth giving CMOS OSC serious consideration.

One other point, CCDs don’t appear to be as popular on the used market as they were a few years ago, so you might need to be realistic about the resale value of the mono camera and ancillaries.

 

[Elp]

I've just gone mono, think i'm in a for a world of pain due to the weather...

[Jamgood]

When I upgraded from DSLR to Dedicated, I went for the OSC for the reason of UK weather. I'm deep in the Midlands in what is known as Cloudsville! As much as I really liked the idea of Mono imaging I just don't get the weather that allows for the kind of time needed for it. The OSC with the Optolong L-Enhance and L-Pro has served me well for the times I found I can use it. I've literally has 2 nights in the last 10 weeks though. 

I'm now thinking when I do eventually go for a mono set up, rather than upgrading, I'll keep the OSC gear as well, for the bad weather spells, and have the best of both worlds.

[Clarkey]

5 hours ago, Jamgood said:

Cloudsville!

Pahh! I live in 'sideways rain and floodsville'🤣

I think the worse thing about Penrith is that it is in the shadow of multiple hills (lakes, pennines and Scottish highlands) so the weather is so hard to predict.

[ollypenrice]

I've made this change recently and have also used both OSC and mono versions of the same camera in the past. The first thing to say is that I think CMOS OSC cameras are much more convincing than CCD OSCs.  (I've used both.) So I think the game has changed, recently.

In the CCD era I was a firm advocate of mono, which is faster and more versatile than OSC. (It quite simply is faster because it can shoot luminance, red green and blue, simultaneously on each pixel. An OSC camera cannot do this and so is, most assuredly, slower. Assertions to the contrary cannot be correct.) This remains true of CMOS cameras as well but the high sensitivity and low read noise of the CMOS camera changes the real-world balance of virtues, in my view, enough to make CMOS OSC worth thinking about.

I'm also using the CMOS OSC in a fast astrograph, a Celestron 8 inch RASA at F2. This makes the time constraint a lot less pressing because we are getting so much signal in so little time that we don't really care about a ten or twenty percent increase in exposure time. It's a percentage increase in 'not a lot.'

Yet another change has been introduced by the dual and tri-band filters now available for OSC. Several members on here have posted deep images of faint NB targets using this technology in fast instruments. We don't have such a filter yet but intend to try one. It is certainly frustrating to lose decent nights to the moonlight, though I have never imaged around full moon, even with a 3nm Astrodon filter in a mono camera.

I'm enjoying using the CMOS-OSC-RASA combination.

Olly

[Clarkey]

7 hours ago, ollypenrice said:

I'm enjoying using the CMOS-OSC-RASA combination

A RASA is on my (long) AP shopping list. The trouble is that the wife has nicked the list! 🤣

[rickwayne]

One technique I've been meaning to try is expediting color capture by interleaving R, G, and B more often.  I usually shoot something around  1:1 luminance and  total of  R, G, and B (i.e. if 90'  of luminance, 30' of each color). And like most people I do one at a time, refocusing for each filter.

I've avoided switching filters too often because when the focus motor is running, I ain't collecting photons. But maybe good enough is good enough; Ekos lets me define focus settings from some filters as offsets from others. So autofocus L to a nicety, shoot a bunch,  R, shoot a few, G, shoot a few, B, shoot a  few, back to L...refocus every 30 minutes or 60 minutes. When the clouds roll in, I'll have collected a bunch of L and roughly R=G=B.  If the luminance is tack-sharp it really doesn't matter if the chrominance is a little bit fuzzy. In fact I know some folks deliberately blur the color channels for noise reduction.

Your thoughts? Still not as simple as OSC, but gets rid of one potential mono pitfall.

[Clarkey]

I try to do similar, particularly if the forecast is a bit iffy. With the Baader Steeltrack focuser I am pretty confident of not needing to refocus on a filter change - just use the offsets and refocus on FWHM. Usually this is a set of about 3 sequences over a night.

[ollypenrice]

8 hours ago, rickwayne said:

One technique I've been meaning to try is expediting color capture by interleaving R, G, and B more often.  I usually shoot something around  1:1 luminance and  total of  R, G, and B (i.e. if 90'  of luminance, 30' of each color). And like most people I do one at a time, refocusing for each filter.

I've avoided switching filters too often because when the focus motor is running, I ain't collecting photons. But maybe good enough is good enough; Ekos lets me define focus settings from some filters as offsets from others. So autofocus L to a nicety, shoot a bunch,  R, shoot a few, G, shoot a few, B, shoot a  few, back to L...refocus every 30 minutes or 60 minutes. When the clouds roll in, I'll have collected a bunch of L and roughly R=G=B.  If the luminance is tack-sharp it really doesn't matter if the chrominance is a little bit fuzzy. In fact I know some folks deliberately blur the color channels for noise reduction.

Your thoughts? Still not as simple as OSC, but gets rid of one potential mono pitfall.

Shock horror: I focus in luminance and then scroll RGB,RGB,RGB without refocusing between the filters. (The exception would be in shooting low targets when I shoot red at the lowest altitudes and blue at the highest, but I can shoot down to the horizon here if I have to.)  I don't find anything wrong with the way this works. Absolutely perfect focus per filter would always be nice but, if we think about how LRGB imaging works, we can see that the penalty for slightly imperfect focus in the colours is trivial. We are not chasing resolution in the colour layer. Indeed most of us make it a low priority in our RGB processing. What we want is strong colour intensity and low noise, both of which are best served by abandoning the pursuit of detailed resolution.

I'm using well colour-corrected optics (Tak FSQ106N and TEC140) with Baader filters. I believe most decent filters are parfocal, any shift in focus coming from the telescope's optics. And think of this: a luminance filter passes R, G and B simultaneously ,with no way of focusing separately between wavelengths,  yet it gives us our most resolved layer all the same.

Olly

[Clarkey]

3 hours ago, ollypenrice said:

And think of this: a luminance filter passes R, G and B simultaneously ,with no way of focusing separately between wavelengths,  yet it gives us our most resolved layer all the same.

Very good point - I'd never thought of it like that.

3 hours ago, ollypenrice said:

I'm using well colour-corrected optics (Tak FSQ106N and TEC140)

Or you do what us poor people do and use mirrors😂. 

[DaveS]

I focus in L and apply any offsets, but when I checked my ODK and Chroma filters I found less difference between filters than between autofocus runs. Checking with a Bahtinov Mask showed that the focus was identical between R,G,B filters.

[Clarkey]

1 hour ago, DaveS said:

I focus in L and apply any offsets, but when I checked my ODK and Chroma filters I found less difference between filters than between autofocus runs. Checking with a Bahtinov Mask showed that the focus was identical between R,G,B filters

Agreed. I only use 'cheap' zwo filters, but the difference in focus is virtually zero. I guess the fact that they are within a few mm's of the sensor will help keep them parfocal. If further away the difference may be more pronounced.

[ollypenrice]

28 minutes ago, Clarkey said:

Agreed. I only use 'cheap' zwo filters, but the difference in focus is virtually zero. I guess the fact that they are within a few mm's of the sensor will help keep them parfocal. If further away the difference may be more pronounced.

Not sure about this. What's your reasoning? I'm afraid I haven't been able to come to a conclusion either way...

Olly

[Clarkey]

9 minutes ago, ollypenrice said:

What's your reasoning?

My assumption is that if the filter has any effect on the light path, then the deviation will be very small at the point of leaving the filter. As the distance increases the distance will increase between the different wavelengths. It is not a scientific reasoning - just my logic.