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Is there still a benefit of mono?


assouptro
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11 minutes ago, ONIKKINEN said:

I meant this one: https://www.aliexpress.com/item/4001359313736.html?spm=a2g0o.productlist.0.0.6f047164JGhOx6&algo_pvid=88c7fc7f-59b2-4b58-9bdc-a75b08237944&algo_exp_id=88c7fc7f-59b2-4b58-9bdc-a75b08237944-0

Comes from China directly so VAT for everyone. When i bought mine i was not charged VAT at the checkout but i think the rules changed just after that and now you pay VAT to aliexpress. You never have to pay VAT twice, if you can prove the value of the item and the already paid VAT with an invoice which you obviously can.

No VAT charged at checkout, it’s charged when it come to the destination country now, along with import duties and other fees…which would be at least £300, so still not a bad price…

 

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2D698CF7-6C99-4726-BE80-C64F6D02F932.jpeg

Edited by Stuart1971
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15 minutes ago, assouptro said:

Are there any of that size that don’t suffer from amp glow? 
I rarely use flats, even with my new (to me) Atik383l as bias and dark flats seem to do the job just as well 

Not that I know of, but I am certainly no expert on CMOS cameras….

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25 minutes ago, assouptro said:

Are there any of that size that don’t suffer from amp glow? 
I rarely use flats, even with my new (to me) Atik383l as bias and dark flats seem to do the job just as well 

Amp glow is easily calibrated out but your next sentence is confusing me. Bias and dark flats are (sort of) similar things and a flat would correct optical train issues. You would need darks to calibrate out the amp glow.

Unless I'm completely misunderstanding what you mean.....

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On a pure fundamental level , there is difference between OSC and mono, that makes mono superior. That is spatial resolution. In the case of OSC, there is Bayer matrix of 2x2 pixels , out of which 2 are measuring for example G, one measures R and other B . Debayering process assigns other two colors to the pixel (so the pixel that was measuring G has to get R and B estimated for this pixel) . In the case of mono each pixel measures each color, no estimations there. Of course , the final image will get the same number of pixels , but the real color fidelity for mono will be on a single pixel level, where in OSC case the real fidelity will be on 2x2 pixels level. No filters or anything as a such would bridge that gap.  How much would that affect the images we do is of course relative . Good very simplified  comparison would be like watching 4K movie on standard HD tv and on 4K tv. 

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4 minutes ago, Stefek said:

On a pure fundamental level , there is difference between OSC and mono, that makes mono superior. That is spatial resolution. In the case of OSC, there is Bayer matrix of 2x2 pixels , out of which 2 are measuring for example G, one measures R and other B . Debayering process assigns other two colors to the pixel (so the pixel that was measuring G has to get R and B estimated for this pixel) . In the case of mono each pixel measures each color, no estimations there. Of course , the final image will get the same number of pixels , but the real color fidelity for mono will be on a single pixel level, where in OSC case the real fidelity will be on 2x2 pixels level. No filters or anything as a such would bridge that gap.  How much would that affect the images we do is of course relative . Good very simplified  comparison would be like watching 4K movie on standard HD tv and on 4K tv. 

Yes but an OSC ASI2600 at 26 megapixel would still be better by far in resolution per colour than older mono CCD cameras, even at 1/4 of the resolution…

But what you say is correct if the cameras were the same…👍🏼

Edited by Stuart1971
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If you want to do true triband NB imaging then you need a mono camera since H-alpha, [NII] (If you can afford 3nm filters), and [SII] all fall close together in the red. A OSC camera can't separate the three wavelengths.

Yes, I've seen pseudo-HST images, but they're just that, Pseudo with no extra information.

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1 minute ago, Stuart1971 said:

Yes but an OSC ASI2600 at 26 megapixel would still be better by far in resolution per colour than older mono CCD cameras, even at 1/4 of the resolution…

But what you say is correct if the cameras were the same…👍🏼

Of course I was referring to the same chip. Otherwise comparing OSC vs. mono is difficult to make 

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1 hour ago, ONIKKINEN said:

I meant this one: https://www.aliexpress.com/item/4001359313736.html?spm=a2g0o.productlist.0.0.6f047164JGhOx6&algo_pvid=88c7fc7f-59b2-4b58-9bdc-a75b08237944&algo_exp_id=88c7fc7f-59b2-4b58-9bdc-a75b08237944-0

Comes from China directly so VAT for everyone. When i bought mine i was not charged VAT at the checkout but i think the rules changed just after that and now you pay VAT to aliexpress. You never have to pay VAT twice, if you can prove the value of the item and the already paid VAT with an invoice which you obviously can.

I’ve been looking at these 

have you got one? 
are there any issues with drivers or software? 
cheers

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Just now, assouptro said:

I’ve been looking at these 

have you got one? 
are there any issues with drivers or software? 
cheers

This is in fact Touptek camera, also sold under Omegon, Altair, Lacerta ,.....label. 

All of them using Touptek drivers (both native and ASCOM )

I have Omegon version, works perfectly with NINA, Sharpcap, but also with Stellarmate 

(INDI) .

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22 minutes ago, assouptro said:

I’ve been looking at these 

have you got one? 
are there any issues with drivers or software? 
cheers

3 months owned one. No critical issues yet. Only slight nuisance with drivers is that sharpcap runs at very low framerates = 0.2fps even. Irrelevant for deep sky and other software like nina are as youd expect from any imx571.

Other than that no issues with sofrware.

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2 hours ago, oymd said:

New Mono CMOS cameras are CONSIDERABLY more expensive than their OSC counterparts.

On top of that you need a filter wheel and SEVEN filters. 

I would say that a mono setup can easily amount to DOUBLE the price of a similar OSC setup, if not more.

I've made an example price breakdown in this article about Mono vs OSC. Ballpark figure is that mono plus required filters is likely to be about 1.5x the cost of an equivalent OSC. But of course it varies hugely based on what kit you go for.

To answer the OP's question, mono has the edge over OSC in many ways, so there are certainly still benefits. But OSC with a dual-band filter is capable of producing excellent results while being cheaper and (depending on what you want from the hobby) potentially more fun to use. Lots of OSC image examples are here in my gallery. and all from light polluted city centre skies.

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11 hours ago, Lee_P said:

 

To answer the OP's question, mono has the edge over OSC in many ways, so there are certainly still benefits. But OSC with a dual-band filter is capable of producing excellent results while being cheaper and (depending on what you want from the hobby) potentially more fun to use. Lots of OSC image examples are here in my gallery. and all from light polluted city centre skies.

I think you have hit the nail on the head. If you want the absolute best quality data to process (and you have plenty of access to the quality of sky needed for the kit to perform at it's best), and you have the budget, go mono and filters. If, like me,  you are battling the clouds constantly, and you actually want to finish some half decent images to share and enjoy, go OSC.

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49 minutes ago, tomato said:

 If, like me,  you are battling the clouds constantly, and you actually want to finish some half decent images to share and enjoy, go OSC.

This is interesting because actually given that mono collects data faster, battling clouds is a point in favour of mono rather than OSC. What I find in practice though is that data acquisition is sufficiently simpler with OSC that I personally find it easier to rack up integration times -- typically 20+ hours per image, even from cloudy Bristol.

I think that discussions about mono vs OSC tend to focus on quite technical aspects, but really the most important factor should be what a person would find more fun to use. The answer will be very dependent on the person, and may well change over time as their personal circumstances change as well. Mono has the potential to give a better end result, but what if someone has a torrid time actually reaching that point? And on the flipside, what if someone has an easier time with OSC and produces a stunning image, but feels that they've sold out by fudging together a Sulphur-II channel in order to recreate the Hubble Palette, for example?

 

 

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14 hours ago, assouptro said:

Is that a clean cmos? 
does it suffer from amp glow?

Amp glow really does not matter. It is completely calibrated out with darks. 

The 294mm is somewhat of a fussy camera when it comes to calibration though, so if it's an easy life you want, I'd look elsewhere.

There's been some talk of the possibility of mono version of the 533, if that comes to fruition it might be the one for you. 

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There are some wonderful images appearing using  RASA scopes.  In this situation an OSC camera is definitely preferable since a mono camera with filter wheel would create a larger and an irregular obstruction to the light path.  

Even my chroma filters aren't parfocal across the board.  This is OK if you can automate focusing but otherwise adds an additional layer of complexity.

With older ccds there was a hit to resolution using OSC.  With the smaller pixels of modern chips this is not the issue that it was even for serious pixel peepers.  However, when it comes to time to achieve a given snr mono still has the edge in most circumstances.  

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Battling clouds for me usually means you get some imaging time but not what I planned. So for example a planned 3 hour session on a dual rig would give me 3 hours L on the one scope and an hour each of RGB. But if the clouds roll in after 2 hrs, you have 2 hrs L, 1 hr each R & G but no B. A dual OSC rig would have collected 4 hrs of RGB and you can do something with this data the next day.

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4 minutes ago, tomato said:

Battling clouds for me usually means you get some imaging time but not what I planned. So for example a planned 3 hour session on a dual rig would give me 3 hours L on the one scope and an hour each of RGB. But if the clouds roll in after 2 hrs, you have 2 hrs L, 1 hr each R & G but no B. A dual OSC rig would have collected 4 hrs of RGB and you can do something with this data the next day.

Could you cycle your R G B filters regularly throughout an imaging session so you have an even number of them regardless of when the cloud runs in? 

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1 hour ago, MartinB said:

Even my chroma filters aren't parfocal across the board.  This is OK if you can automate focusing but otherwise adds an additional layer of complexity.

My Chroma filters in the ODK are as closely parfocal as I can measure. Checked with the autofocus routine, and the variation between filters was less than the variation between runs. Checked with a Bahtinov mask, and the central spike was dead centre in all filters without refocusing.

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  • 4 weeks later...
On 27/11/2021 at 16:57, Lee_P said:

Could you cycle your R G B filters regularly throughout an imaging session so you have an even number of them regardless of when the cloud runs in? 

You certainly could if your filters are parfocal, so you don’t need to refocus each filter change, but I wonder how many folks have tried this approach?
 

Your EFW would earn it’s keep!

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4 minutes ago, tomato said:

You certainly could if your filters are parfocal, so you don’t need to refocus each filter change, but I wonder how many folks have tried this approach?
 

Your EFW would earn it’s keep!

Hi

This is what I do every time :) - make sure you focus with the Lum as thats the critical item - if the rgb is slightley off focus it will not matter

but I use baader filters and they keep good focus between filters - make sure you refocus when the temp changes this has more of a affect

Cheers

Harry

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4 minutes ago, tomato said:

You certainly could if your filters are parfocal, so you don’t need to refocus each filter change, but I wonder how many folks have tried this approach?
 

Your EFW would earn it’s keep!

Even if the filters are not parfocal, this can be done without the need of a full refocus. Packages like SGP and NINA have the option of filter offsets. Those offsets need to be determined once and then entered, after which the software applies them for the filter changes. Although I image in traditional sequences (i.e. colour by colour) I use the offsets to shorten the focus-runs by always focusing in luminance and applying the offset for the filter that is used for the current set of subs.

Above package do allow repeating LRGB-NB sequences.

I do not bother too much about non-finished sequences due to clouds as most of my sequences do not fit a single night anyway (they tend to be 20-45 hours). So I check in the morning what was properly recorded and adjust the sequence for next night to get the balance right again.

Nicolàs

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I really enjoy OSC with a good dual narrow band filter but (and this can be a huge but) you don't get exactly pure Ha and OIII data, when you split the channels.

That's because the camera's RGB filter array doesn't have steep frequency cut-off, resulting to green wavelengths (OIII) leaking in the red channel and red (Ha) leaking in the green. Also that leak percentage is not standard, but is sensor related, as different sensors have different RGB bandpass graphs.

So by splitting channels, your Ha channel (red) is essentially a 90-10% mix of Ha-OIII and your OIII (green) is a 80-20% mix of OIII-Ha.

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7 minutes ago, R26 oldtimer said:

I really enjoy OSC with a good dual narrow band filter but (and this can be a huge but) you don't get exactly pure Ha and OIII data, when you split the channels.

That's because the camera's RGB filter array doesn't have steep frequency cut-off, resulting to green wavelengths (OIII) leaking in the red channel and red (Ha) leaking in the green. Also that leak percentage is not standard, but is sensor related, as different sensors have different RGB bandpass graphs.

So by splitting channels, your Ha channel (red) is essentially a 90-10% mix of Ha-OIII and your OIII (green) is a 80-20% mix of OIII-Ha.

How about some math to fix that?

Say you have A and B that are some quantities (Ha and OIII for example) and you get

X = 0.9*A + 0.1*B

Y = 0.8*B + 0.2*A

Y - 8*X = 0.8*B + 0.2*A - 7.2*A -0.8*B = -7*A

A = (8*X - Y)/7

And similarly you can get B as well

In another words - even if you have mixed Ha and OIII in your red and green (and blue) channels - you can extract pure Ha and OIII components with some math performed on your channels.

If you don't have exact QE efficiency of your duo band filter and camera (or you doubt published graphs) - then you can establish those by shooting stars of known temperature (with known spectrum) and calculating what is QE based on your per channel results.

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