Mono Vs OSC considerations and focus shift

[Jbro1985]

Whilst OSC can be used for narrowband, it isn't any where near as effective as mono.  

If you image from a location that provides light pollution challenges, you can cut through that challenge with narrowband.  This is the single biggest advantage of mono for me.

As an aside, it is also facinating to see the details you can sometimes tease out from a narrowband image that can be elusive in LRGB. Of course, this is somewhat slanted towards imaging nebulae.  If your prime targets are galaxies, and perhaps planets then the advantages of mono LRGB against OSC are less pronounced, in my view. 

Each have their own challenges in terms of processing.  

I found that after a few runs with a mono I got beyond what felt like real complexities at the start with regard to both acquisition and processing.  Thereafter, you end up with a more flexible system, that also has room to expand (for instance I started mono LRGB, moved to LRGBha and at the moment and concentrating on ha, OIII and SII).  Of course the OSC provides simplicity on acquisition (not necessarily processing due to the likes of LP gradients) and that's the trade off.  Flexibility and detail Vs simplicity.  

Believe me, some nights I do wish for the simplicity!

[Allinthehead]

This one is interesting and a filter I've ordered to try one shot bi colour imaging. Just to confuse you a little more Matt?

[gorann]

1 hour ago, Allinthehead said:

This one is interesting and a filter I've ordered to try one shot bi colour imaging. Just to confuse you a little more Matt?

Yes, that is an interestng filter Richard and it will be exciting to see what you can get out of it. I was about to order one when Wim pointed out to me that Oiii is often much weaker than Ha. So, in contrast to shooting with separate filters, with this combi filter you cannot compensate for that by exposure times since you may be overexposing Ha while underexposing Oiii. I imagine that it may work better on some objects than others depending on the Ha to Oiii signal ratio.

[mos]

3 hours ago, Allinthehead said:

This one is interesting and a filter I've ordered to try one shot bi colour imaging. Just to confuse you a little more Matt?

2 hours ago, gorann said:

Yes, that is an interestng filter Richard and it will be exciting to see what you can get out of it. I was about to order one when Wim pointed out to me that Oiii is often much weaker than Ha. So, in contrast to shooting with separate filters, with this combi filter you cannot compensate for that by exposure times since you may be overexposing Ha while underexposing Oiii. I imagine that it may work better on some objects than others depending on the Ha to Oiii signal ratio.

Yeah I have seen that filter and it does seem very interesting! There are some rather beautiful colours in that image.

Would Oiii be captured primarily by the green and/or blue pixels? I wonder if this would balance things out somewhat between Ha and Oiii? 

 

[Ouroboros]

Off topic but does anyone know whether there is any possibility that ZWO will launch a mono version of their ZWO ASI071MC Pro colour canera?

[ollypenrice]

2 hours ago, Ouroboros said:

Off topic but does anyone know whether there is any possibility that ZWO will launch a mono version of their ZWO ASI071MC Pro colour canera?

The million dollar question. There are several superb CMOS chips currently only available under a Bayer matrix.

Olly

[gorann]

22 hours ago, glowingturnip said:

was going to chime in and say what Olly said about focussing for lum and then not worrying too much about the focus on the R, G and B in the same session.

But also if you went OSC, you're going to find it very difficult/impossible to do any narrowband with it in the future.  I never thought I'd get into narrowband, but I was definitely wrong there...

Sorry fro this double post. It was caused by the SGL site apparently being down for a while yesterday and when my job computer got connected again it sent it off again......

I do not agree that NB imaging, at least Ha, is very difficult/impossible with a OSC. Below is an image I took with my ASI071 (a APS-C sized cooled OSC) on an Esprit 150 and a Baader 7nm Ha filter. That being said, I have now also invested in an ASI1600mono for collecting NB side by side in another scope.

[Laurin Dave]

5 hours ago, Ouroboros said:

Off topic but does anyone know whether there is any possibility that ZWO will launch a mono version of their ZWO ASI071MC Pro colour canera?

Apparently QHY have a QHY168M out for Beta testing (Terry Hancock has posted photos on Flickr)..  so lets hope . he has also posted narrowband images taken with the QHY367C (full frame)

Dave

[gorann]

20 minutes ago, Laurin Dave said:

Apparently QHY have a QHY168M out for Beta testing (Terry Hancock has posted photos on Flickr)..  so lets hope . he has also posted narrowband images taken with the QHY367C (full frame)

Dave

That is exciting news! I assume Olly @ollypenrice  will be one of the first to buy one if it comes past the beta version. I would have been one of the first if I had not recently bought an ASI1600MM since I gave up waiting for an APS-C sized mono CMOS camera. I wonder if they have manually removed the bayer mask or if they got Sony to produce a batch without them. In any case they will probably be a bit more costly than the color version.

[ollypenrice]

3 hours ago, gorann said:

That is exciting news! I assume Olly @ollypenrice  will be one of the first to buy one if it comes past the beta version. I would have been one of the first if I had not recently bought an ASI1600MM since I gave up waiting for an APS-C sized mono CMOS camera. I wonder if they have manually removed the bayer mask or if they got Sony to produce a batch without them. In any case they will probably be a bit more costly than the color version.

You over-estimate my income!  I'll also say that I am not yet 100% convinced by CMOS for imaging at the highest possible level but, bang for buck, it can't be beaten and it represents the only way to have both full frame and small pixels, the holy grail of the FSQ106.

Olly

[RayD]

6 minutes ago, ollypenrice said:

You over-estimate my income! 

Wish I had £1 for every time I've said that to my Mrs ?

[ollypenrice]

1 minute ago, RayD said:

Wish I had £1 for every time I've said that to my Mrs ?

I'm somewhat prone to over-estimating it myself, like most astronomers (or most men?)

Olly

[gorann]

4 hours ago, ollypenrice said:

I'm somewhat prone to over-estimating it myself, like most astronomers (or most men?)

Olly

I think I just fell into that trap by making the down payment for a Mesu mount, partly thanks to your continuous promotion of it Olly....

[ollypenrice]

23 hours ago, gorann said:

I think I just fell into that trap by making the down payment for a Mesu mount, partly thanks to your continuous promotion of it Olly....

I don't promote the mount, Goran, I just say that both of mine always work. And they do!

Olly

[gorann]

3 minutes ago, ollypenrice said:

I don't promote the mount, Goran, I just say that both of mine always work. And they do!

Olly

 

6 minutes ago, ollypenrice said:

I don't promote the mount, Goran, I just say that both of mine always work. And they do!

Olly

Good to know Olly. Now my only  (rather significant) worry is that of having a mount dependent upon a computer rather than  a simple handset......

[Adam J]

On 14/11/2018 at 01:25, mos said:

Hi everyone,

Soon enough I will make the leap from my DSLR to a cooled CMOS camera - either ZWO's  294MC or 1600MM mini kit. And to put it short I'm struggling. 

I've done a lot of research on here about the pros and cons of color vs mono with the underlying sentiment of wanting to have the potential for great images but these don't necessarily have to be the best I could achieve . So going mono over OSC because mono could produce great images and is much more versatile as opposed to OSC producing very good images and being less versatile (by way of a simple comparison) is not the biggest factor I'm struggling with here.  (For the record I'd really love to go mono for these reasons).

The biggest concern for me with this is in the 'overheads' of getting good mono images and specifically the need to potentially refocus between different filters. Simply put...between balancing family and other commitments I don't know if i'd be able to give mono imaging the attention it requires. I often remote connect from inside the house to be able to keep an eye on things but something like an auto-focuser to keep the current and relatively 'hands off' ability I have with my DSLR is a bit too far for my current budget. 

I use a 150PDS reflector (with an MKiii MPCC) which means filter focus shift may not even be an issue? But I haven't been able to find any info on whether it is as the majority of information around parfocal topics usually involve refactors. 

Apologies if this seems like I'm making a mountain out of a molehill for such a little detail but this is probably the last point at this stage of my life where i'll be able to sink some money into this amazing hobby and I'd love to make sure I'm doing the best I can to maximize my actual time capturing quality images, as this new camera will be in my setup for the foreseeable future.

Any help and guidance very much appreciated and if you just want to say "Go mono, you won't regret it" that helps too :')

Thanks,

Matt

 

I have a MPCC MKIII and I can tell you there is focus shift between the RGB filters (Baader) however its not enough to prevent you from imaging RGB in sequence. I would refocus for lum though.

I guess its because there is a small amount of CA introduced by the MPCCMKIII as it is only a doublet corrector as opposed to a three / four element ED glass corrector at the other end of the scale.

[Adam J]

On 14/11/2018 at 15:29, RayD said:

That's very interesting as you don't seem to make any focusing allowance for change in temperature.  

Just as a sanity check for me, are you saying you don't believe temperature change has any effect on focus, that it does but not enough to worry about, or that it does and you deal with it in processing?

I find with my FSQ106 that from the beginning of a night's imaging to the end, if the temperature has changed significantly (more than a few degrees), the difference in counts following auto-focus is considerable, and I would have thought more than enough to have a noticeable impact, albeit I haven't tried by not refocusing when the temperature changes.

I would guess it depends on the F ratio of the scope and the scope tube material.

How fast is that FSQ106?

However, I have also noted that since i got my obsy its not something that has been an issue for me...so I do wonder if allot of the need to refocus is more to do with the scope not having fully reached ambient at the start of a session.

Adam

[ollypenrice]

11 hours ago, gorann said:

 

Good to know Olly. Now my only  (rather significant) worry is that of having a mount dependent upon a computer rather than  a simple handset......

We're off topic so I'll PM you.

Olly

[mos]

Well hi again everyone - I finally made my purchase and thought it was only fair to let you know where I landed! In the end I decided to go for the 1600MM with the full set of filters.  

It was of course cloudy for a few weeks (sorry about that!) but last night I got the chance to really see what I had going. 

No introduction needed for the attached image! It's only 16 x 30s luminance exposures at unity gain and a bit of quick processing is APP and Startools. 

My MPCC III needs a bit of tuning - I've increased the spacing from the standard 55mm as it wasn't cutting it and might still need to go a little more.  But overall I am incredibly happy with this shot. Incredibly happy.

Thank you once again for all the advice. This is exactly what I was hoping to be able to achieve. 

Now to add some colour tonight....?

- Matt

 

[ollypenrice]

That really is a great result.

While shooting the colour I'd take a short set of RGB at significantly shorter exposure so as to fill in the Trapezium. You'll be at very high SN on this bright region so there is no point in shooting L or a lot of subs. You could then follow this excellent tutorial on how to blend the long and short. http://www.astropix.com/html/j_digit/laymask.html

Olly

[Wiu-Wiu]

I've been following this thread for a while since I am making the very same considerations. 

I thought I had my mind set on the 1600MM pro + filters + asiAir; and went ahead and bought the filters, and start saving up for the rest. But someone pointed out to me that I do not have a fixed setup, and like people in this topic said: it's considering mass versus convenience. 

I do not have a fixed setup because of the LP where I live. I thought adding filters would make at least NB accessible, so I could get some data on nights that are relatively decent. 

Of course, it turns out that the color camera is more expensive than the mono, and has a bigger sensor; which would mean a filter wheel with 1.25 filters will probably give me a bunch of vignetting. 

So I'm back to the drawing board. 

A quick question for those who are pro mono camera... Is any one of you "mobile" like me? Does my consideration make sense? My gear is in my subscript.

I like color, but I like GOOD data more. I love nice pics in B&W as well as the color ones. 

[geordie85]

1 hour ago, Wiu-Wiu said:

I've been following this thread for a while since I am making the very same considerations. 

I thought I had my mind set on the 1600MM pro + filters + asiAir; and went ahead and bought the filters, and start saving up for the rest. But someone pointed out to me that I do not have a fixed setup, and like people in this topic said: it's considering mass versus convenience. 

I do not have a fixed setup because of the LP where I live. I thought adding filters would make at least NB accessible, so I could get some data on nights that are relatively decent. 

Of course, it turns out that the color camera is more expensive than the mono, and has a bigger sensor; which would mean a filter wheel with 1.25 filters will probably give me a bunch of vignetting. 

So I'm back to the drawing board. 

A quick question for those who are pro mono camera... Is any one of you "mobile" like me? Does my consideration make sense? My gear is in my subscript.

I like color, but I like GOOD data more. I love nice pics in B&W as well as the color ones. 

My apologies but your post confuses me. 

You've only mentioned 1 camera (1600) but you're saying colour is more expensive than mono? The colour asi 1600 is £962 and the mono is £1170. Or are you comparing cooled against uncooled? 

You also say the colour has a bigger sensor.... But they are the same sensor so they will both be the same size. 

About the use of 1.25 filters, here are people who use 1.25 filters with the atik 383L (ever so slightly bigger sensor) with success. I think you'll just need a decent set of flats to correct the vignetting. 

As for setting up every night I do this and have never had a problem imaging the same target on several different nights. Although I do leave my camera and scope connected so I can reuse my flats. I've also "marked" where my mount was sitting on the previous imaging session so I can get as close as possible to having it in the same position. 

[Laurin Dave]

Guess Wiu-Wiu  is talking about the ASI1071 which is APS-C and has a 28mm diagonal vs the 22 mm of the ASI1600...   and needs 31mm or so clear aperture for filters... (according to Astronomy Tools) ie 36mm

[Wiu-Wiu]

I was referring to the 071 indeed. I'm just still in the blue for the need of filters with that camera. If I could shoot color most of the time, and use it to also gather some NB, it would not be entirely useless at home... 

[bottletopburly]

On 14/11/2018 at 01:25, mos said:

an auto-focuser to keep the current and relatively 'hands off' ability I have with my DSLR is a bit too far for my current budget

It doesn’t have to be Deepskydad does an autofocus unit from about £110 ish photo is focuser fitted to my scope note new version focuser I now more compact  is use APT to control or you can make your own cheaper plenty of info if you google diy auto focuser