OSC Camera, Two Scopes and Lots of Filters

[Buzzard75]

I've been doing a lot of reading lately on the subject of filters and OSC cameras. I'm familiar with mono imaging and filters as that is what I've done extensively up to this point. I've taken little bits and pieces from several discussions, what I know from experience, and some information specifically about single narrowband filters. My head is honestly swimming right now looking at so many different filters, different bandpass widths, f/ratios and (OMG!!) the math.

So to cut to it, I am delving into the realm of OSC cameras now as I recently acquired a QHY247C. I know I need/want a multiband filter for it, as well as a LPS filter of some sort, but I don't quite know which ones yet. I have two scopes the camera could be used with, one is an f/4.9 and the other is an f/8. My biggest concern is the multiband bandpass widths. Even though we're talking about multiband filters, you still have curve shifts to deal with. Knowing how the math works and that something with a 3nm width theoretically works well for systems up to f/5 (Thanks @vlaiv for the math), I don't think I could go wrong with any of the current filters on the market. What I don't quite understand is how manufacturers of these extremely narrow filters (3-4nm) can say they work for systems as fast as f/2 or f2.2 though. I guess it depends on where your on-axis transmission line for the filter is. If it shifts too much and doesn't fall directly on the transmission line you're interested in, you'd get some of that data, but not as much as you would with a wider band or a slower system, if I understood @vlaivcorrectly, and his analogy of the filter acting like an aperture stop in this regard.

Every filter I've looked at has a slightly different transmission curve and different bandpasses. I'm trying to figure out how well they would perform with each of my systems and what the best single option would be that would work well with both and not break the bank.

For multiband filters (2") my top contenders right now are: Optolong L-Extreme, IDAS NB2 (w/ additional IR cut filter) or the new IDAS NBX. The L-Extreme has one of the narrowest bandpasses, but is currently backordered by several weeks because everyone wants one. The IDAS NB2 requires an additional IR cut filter, but I have a filter that should work for that. The IDAS NBX is so new that there isn't a lot of information about it or pictures from it other than what's on the company website. I am certainly open to other suggestions. I would like to keep price down to around $300USD (230GBP). I live in Bortle 5/6.

For broadband filters, I currently own a Baader Moon and Skyglow filter. I am considering getting something different though as it is old and has a significantly large transmission curve in the blue/green part of the spectrum. We are all aware of the effects of new LED lights which primarily fall into this part of the spectrum. My top contenders for this type of filter right now are: Optolong L-Pro, IDAS LPS D2, or IDAS NGS1. I don't know how much of an improvement the L-Pro or IDAS NGS1 would be over my current filter. The IDAS LPS D2 was however specifically designed with LED's in mind, which I have street lamps all around my house and nearby shopping centers. I am of course open to other suggestions.

[Davey-T]

Video from one of your compatriots, not sure if it's relevant but interesting.

Dave

https://www.youtube.com/watch?v=fNpYbGUzodg

 

[Buzzard75]

@Davey-T, I did see that a few weeks ago. If I'm considering the IDAS NB2, then the L-enHance is definitely one to consider I suppose. It has a slightly narrower Ha pass than the NB2 (10nm vs 19nm) and already has an IR-cut which the NB2 does not. If I had to choose between the IDAS NBX and the L-enHance right now though, I would probably choose the IDAS NBX with its 11nm bandpasses (possibly narrower?) for both Ha and OIII where the L-enHance is 10nm and 21nm respectively.

The narrower bandpasses (7nm for both Ha and OIII) for the L-eXtreme definitely balance out the Ha and OIII though, which is what I'm used to shooting with my mono and narrowband filters. If I could get my hands on an L-eXtreme though, I would probably choose that over the NBX, especially considering I haven't seen a single image from the NBX yet.

EDIT: The IDAS Facebook page has a few charts and graphs for the NBX filter and quotes the bandpass widths as 11nm.

Edited October 5, 2020 by Buzzard75

[Davey-T]

I'm considering one of these for my fast OSC setup, bit on the expensive side but buy once as they say

https://optcorp.com/products/radian-telescopes-2-inch-triad-ultra-filter

Dave

[Nikolas74]

I am too on the same path....I am ready to invest to Zwo Asi2600MC Pro after doing Mono for a long time ,just for curiosity reasons to see if they are as good as it looks like, but it seems the most difficult decision is on what filter to invest....

There are so many out there dual band Tri band quad band etc and now this NBX is out.....

Specs of these filters is a bit difficult to find...

[Buzzard75]

46 minutes ago, Davey-T said:

I'm considering one of these for my fast OSC setup, bit on the expensive side but buy once as they say

https://optcorp.com/products/radian-telescopes-2-inch-triad-ultra-filter

Dave

The price is what's keeping me away from that one. I don't know that getting H-beta and SII are really worth the extra $700USD, especially when the peak transmission of H-alpha appears to be reduced compared to other dual-band filters.

 

11 minutes ago, Nikolas74 said:

I am too on the same path....I am ready to invest to Zwo Asi2600MC Pro after doing Mono for a long time ,just for curiosity reasons to see if they are as good as it looks like, but it seems the most difficult decision is on what filter to invest....

There are so many out there dual band Tri band quad band etc and now this NBX is out.....

Specs of these filters is a bit difficult to find...

Most of the specs are available on the manufacturer websites if they aren't on the resellers. I just takes a lot of time to research all of them. The NBX data in particular is lacking since it is so new. Again, I had to look at their Facebook page (which is all in Japanese) to find the bandwidths. Thankful for the translation feature. One of our fellow forum members @Space Oddities put together a nice spreadsheet for several filters that has their bandwidths. Further down that thread he links to his updated spreadsheet which has the NBX data. It doesn't quite match their Facebook data though (10nm vs their quoted 11nm).

 

Edited October 5, 2020 by Buzzard75

[Nikolas74]

I am leaning towards the L extreme too at least for starters 😄...hoping that I will not have to spend into other filters....I believe 7nm is not bad for a OSC...

[R26 oldtimer]

I have the optolong l-enhance and thinking whether should I upgrade to the L-eXtreme. I think that the name of the game is separating the narrowband signals. Since most osc cameras have Rgb arrays, then it comes down to isolate the signal from  Ha on the red channel and OIII from the blue/green, or perhaps SII and OIII or sii and Hb. Then as is the case with conventional nb filters, the tightest bandpass wins.

I think I'll wait for an L-supermaxHOO with 5nm OIII & Ha bandpass and an L-supermaxSIIHbHb with similar bandpass on SII and Hb. 😋

[Buzzard75]

1 hour ago, Nikolas74 said:

I am leaning towards the L extreme too at least for starters 😄...hoping that I will not have to spend into other filters....I believe 7nm is not bad for a OSC...

No, 7nm isn't bad at all, generally the narrower the better. Like I said, that's what I've been shooting with on my mono with good results. It's just hard to get an L-eXtreme at the moment. Most places are backordered by several weeks right now due to the popularity.

[Nikolas74]

So if i have a filter wheel and a set of narrowband filters of lets say Baader, i can do the same job? as if i have one filter? lets say L extreme? 

[Buzzard75]

1 minute ago, Nikolas74 said:

So if i have a filter wheel and a set of narrowband filters of lets say Baader, i can do the same job? as if i have one filter? lets say L extreme? 

Theoretically, yes, but the resolution will be reduced compared to a mono camera due to the Bayer matrix (color filter that assigns each pixel a specific color) in a OSC camera. For example, if you put an Ha filter in front of an OSC camera, only 1 in 4 pixels will receive any signal. The two green and 1 blue pixel in that matrix will see nothing. The same would be true for any other narrowband filter you put in front of an OSC camera. Whereas with a mono camera, every single pixel will receive a signal because there is no filter matrix. Some people will use an Ha filter and stack it with their data to boost the red/pink color for certain targets like emission nebulae in our own galaxy or those in other galaxies.

[Nikolas74]

👍

[ollypenrice]

What kind of pictures do you aim to take? I'm never entirely sure what the end product of these multi band filters is meant to be. I recently processed some L-enhance OSC data and found, as you'd expect, that it passed the Ha and OIII but subdued the broadband blue. So what's the picture aiming to be? A kind of one shot HOO? I'm not knocking the filters, not at all, but I'm genuinely unsure of the objective.

I could imagine using such a filter in conjunction with a stack of unfiltered OSC images rather in the way that I add Ha to enhance red and OIII to enhance green/blue but I don't know whether that would work.

As I've said elsewhere, I understand that the L-enhance passes blue in the H-Beta line but that is not the blue of reflection nebulae and, besides, it only traces the same gasses as the Ha.

Olly

Edited October 6, 2020 by ollypenrice
Typo

[Buzzard75]

5 hours ago, ollypenrice said:

What kind of pictures do you aim to take? I'm never entirely sure what the end product of these multi band filters is meant to be. I recently processed some L-enhance OSC data and found, as you'd expect, that it passed the Ha and OIII but subdued the broadband blue. So what's the picture aiming to be? A kind of one shot HOO? I'm not knocking the filters, not at all, but I'm genuinely unsure of the objective.

I could imagine using such a filter in conjunction with a stack of unfiltered OSC images rather in the way that I add Ha to enhance red and OIII to enhance green/blue but I don't know whether that would work.

As I've said elsewhere, I understand that the L-enhance passes blue in the H-Beta line but that is not the blue of reflection nebulae and, besides, it only traces the same gasses as the Ha.

Olly

I think that really is the objective, for people with OSC cameras to be able to produce HOO-like images. Doing the same with a mono camera requires the use of multiple filters and possibly other equipment like filter drawers or wheels that are added expense. For broadband targets, LPS filters already abound, but there was nothing for narrowband. It's a hole in the market that is now being filled.

Don't get me wrong, I love my mono camera and I know an OSC with these multiband filters will never hold a candle to it. However, I was in the market for a new camera for the f/8 scope, but chose an OSC because I also wanted to be able to do EAA and show people DSO's (galaxies, planetary nebula, clusters, etc) in color. Most useful in that regard will obviously be an LPS filter of some sort intended for broadband, but if I ever wanted to try my hand at emission targets, I would need something like a multiband filter to get any detail at all.

There are those that say OSC imaging is easier than mono. I would agree that the act of imaging is easier as there are less logistics involved with switching out filters, ensuring that exposures for each filter are correct, and having to set focuser positions for each filter. Much of that can be automated, but the act of automating can be difficult and daunting for some. The act of processing is a question though. Is it easier to process OSC data or filtered mono data? On one hand you have an image that is already integrated with all the colors so you don't have to deal with three or more sets of data, but on the other hand you can deal with the noise and other issues in each of your mono channels much easier and more precisely than you can with something that's already been integrated. Sure, you can break an OSC image down into its independent channels and process each channel individually, but I can guarantee the results will be different than someone who captured the independent channels with a mono camera.

In the end, I think both mono and OSC cameras have their place. It's down to the person to determine what they want to do with them and what compromises they're willing to make. As for the filters, people with OSC cameras need filters just like the people with mono cameras. As I said, it's a hole that the manufacturers are more than happy to fill as long as there are people willing to pay for them.

Edited October 6, 2020 by Buzzard75

[ollypenrice]

31 minutes ago, Buzzard75 said:

I think that really is the objective, for people with OSC cameras to be able to produce HOO-like images. Doing the same with a mono camera requires the use of multiple filters and possibly other equipment like filter drawers or wheels that are added expense. For broadband targets, LPS filters already abound, but there was nothing for narrowband. It's a hole in the market that is now being filled.

Don't get me wrong, I love my mono camera and I know an OSC with these multiband filters will never hold a candle to it. However, I was in the market for a new camera for the f/8 scope, but chose an OSC because I also wanted to be able to do EAA and show people DSO's (galaxies, planetary nebula, clusters, etc) in color. Most useful in that regard will obviously be an LPS filter of some sort intended for broadband, but if I ever wanted to try my hand at emission targets, I would need something like a multiband filter to get any detail at all.

There are those that say OSC imaging is easier than mono. I would agree that the act of imaging is easier as there are less logistics involved with switching out filters, ensuring that exposures for each filter are correct, and having to set focuser positions for each filter. Much of that can be automated, but the act of automating can be difficult and daunting for some. The act of processing is a question though. Is it easier to process OSC data or filtered mono data? On one hand you have an image that is already integrated with all the colors so you don't have to deal with three or more sets of data, but on the other hand you can deal with the noise and other issues in each of your mono channels much easier and more precisely than you can with something that's already been integrated. Sure, you can break an OSC image down into its independent channels and process each channel individually, but I can guarantee the results will be different than someone who captured the independent channels with a mono camera.

In the end, I think both mono and OSC cameras have their place. It's down to the person to determine what they want to do with them and what compromises they're willing to make. As for the filters, people with OSC cameras need filters just like the people with mono cameras. As I said, it's a hole that the manufacturers are more than happy to fill as long as there are people willing to pay for them.

Yes, don't get me wrong, I'm not trying to engage in a mono versus OSC debate. I think that recent CMOS cameras have changed the rules. In the CCD world I felt that mono was faster, easier (in the long run), more flexible and simply better. But having processed a 32 panel mosaic captured by Yves Van den Broek in a CMOS OSC I'm happy to say that this data bore no resemblance to the thin stuff I was used to in OSC CCD. It was sensational data. (From a dark site. Yves' gear is hosted at my dark site.)  https://www.astrobin.com/g82xf7/B/?nc=user

My question is really, 'What does the multi-band filter add to OSC and how is it best used?' When you say, 'I think that really is the objective, for people with OSC cameras to be able to produce HOO-like images,' that makes perfect sense. I don't know how effective the filter is in achieving this but I understand the objective.

Olly