How Narrowband do you need for Astrophotography? Analyzing Astronomik MaxFR filters
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- Опубліковано 7 лип 2024
- I have been trying to figure out if it is worth investing in the really narrowband filters, and haven't seen an in depth explanation of exactly what you get for 12 nm, 6 nm, or 3 nm FWHM filters. I have a hyperstar (f/2) and selecting narrow band filters that work on fast optics requires some extra considerations. Here is my attempt at analyzing the Astronomik MaxFR narrowband filters designed for fast optics, like the Celestron RASA or Starizona HyperStar. I am doing this for both my HyperStar (f/2) and Edge HD (f/7) SCT scope configuration. This is the first part looking at just the Celestron Edge HD with 0.7 Reducer and the Ha Filter.
Turns out, I like to talk, my first pass at this was more than 30 min long, sorry if the edit is a little choppy.
Links:
My Astrobin page: www.astrobin.com/users/bmanto...
Cuiv and fast optic filters: • RASA and Hyperstar vs ...
Bokeh topics: • BOKEH explained in int...
ImageJ (free image analysis): imagej.nih.gov/
Astro Image J: www.astro.louisville.edu/soft...
Deep Space Dad looks at MaxFR filters: • Astronomik 6nm MaxFR (...
Chapters:
0:00 - Intro
0:30 - Filters for Fast Optics
3:00 - Scope Setup
4:00 - Filters with Halos
5:44 - MaxFR Ha Filter - Halos?
6:50 - Pixel Math
9:51 - ImageJ and cross sections
11:51 - Effect on star size
15:11 - Nebulosity and background
19:09 - Conclusions - Навчання та стиль
![Bandwidth choices for narrowband imaging with fast optics [4k]](http://i.ytimg.com/vi/rtFX92dZE_w/mqdefault.jpg)
![Bandwidth choices for narrowband imaging with fast optics [4k]](/img/tr.png)
Good job !!
Thank you very much for your effort in comparing the filters. I am interested because I am considering an upgrade from my 7nm filter set to a 3nm set. I am not an expert so please correct me if my concept is wrong.
For the contrast issue, assuming you can measure the background correctly at point C, then subtract it from A, what is left should be the pure signal. When I see that both filters have the same 'jump' at B, I think it is perfectly normal and it just shows that both filters pass through the same amount of signal.
But I think there should be real benefit for a lower background with a 6nm. The sky background is not a perfectly 'smooth value' added to the signal but with noise. Cutting the background more should mean this noise getting lower. Then during processing we can stretch the 6nm images more with the same visual level of noise. That's where the better contrast come from.
Thanks. I have thought a bit since I posted this.
1. I am in Bortle ~5.3 (according to some app), after talking with a few other people, the differences would be much more apparent if there was more light pollution.
2. The real definition of contrast does not use the background subtraction that I used, so yes, there is probably some benefit to using the 6 nm, especially if there is more light pollution. However, if you are using fast optics (< f/2.5) you may be losing more signal than just reducing background. To go to 3 nm filter, you probably need to be > f/4 ish? to not have so much band shift that you are cutting a lot of signal (guessing, not running a calculation) I did a few other videos with some corrections to this video.
Excellent review. I learned a lot - thank you. I'm getting significant halos with Astronomik Type 2c Blue and Green 36mm filters on an f7 APO refractor. Astronomik referred me to your video to understand more about halos. Since your video doesn't go into the why too much, I'm still left not knowing what to do to correct them. I'm getting a new set up at f7.5 but with Chroma filters and I'll see if they help. I understand shorter exposures with faster optics is the direction of good for halos - so I'm not very hopeful.
On your question of the background difference - I live in Bortle 5 skies according to the Clear Outside App but am on the edge of a city of about 100,000 people. So to the East my sky backgound is higher than to the West. It is easily visible with the naked eye. If the 6nm images were taken to the East and the 12nm to the West from my location, I expect it would confound the result. Something to add to your possible explanations.
Look for another video on my channel called "Bandwidth choices for narrowband imaging with fast optics"
at the 6:53 marker I talk a lot more about how to figure out where the halo is originating from.
The size of the halo tells you this distance from the sensor that is generating your reflection. In my case it was optics in the camera, not the filters. And the strength of some reflections may be very wavelength dependent.
youtube tends to filter out links, see if this works ua-cam.com/video/rtFX92dZE_w/v-deo.html
I can hardly wait for the Oiii filter review. My 6.5 nm Oiii filter and Alnitak produces awful reflections in some of the strangest places. I now have Antlia 3 nm NB filters but it has been awful weather so I haven't had the chance to use it.
soon, switching the scope over to hyperstar tonight so I can image tomorrow. [spoiler alert] At least at f/7 the OIII MaxFR was showing halos for both 6 and 12 nm. Talked with @deepspacedad and he didn't see reflections, at least with HyperStar.
@@BrentMantooth I have a QHY 268M (and other cameras, way too many cameras) and I am interested in a Hyperstar for my EdgeHD 9.25. Unfortunately, Starizona hasn't responded to my emails about whether I can use it with the Hyperstar. None of the QHY cameras on the website list the 268M or the 600M but they list the ZWO 6200.
I know they can support full frame 35 mm sensors (probably with vignetting) - I have the adapters for my Canon R5 but haven't tried that yet. You should just need the right back spacing.
It would be hard to get say 15 x 500 sec subs for both filters over one night. So many things are going to change especially with the elevation of the scope towards zenith. So much to consider when going the Hyperstar way. I just realised that my Antlia 3 nm Pro NB filters "might not be" working all that well at F2 as they suggest F3 as the best solution.
these testing nights are educational. I may do some more comparisons but it is twice the work... and not as ideal for image workup.
for your current filters - you have them and they actually get f3 that isn't bad, and it is a big investment in more filters for what is less than a full stop difference. Are the antlia filters blue shifted for fast optics? It would seem they would need a specific shift for that narrow of a bandwidth and a particular f stop.
@@BrentMantooth The Antlia website says? "Blue-shift data show that Antlia 3nm Pro filters can be used with nearly all systems as fast as f/3 with minimal loss in emission signal and meets the requirements of fast optics like Hyperstar and RASA.". I have the filters for normal imaging F5.6 on my refractor. I haven't used them on the SCT yet as I am waiting for my Celestron OAG to arrive (tomorrow) and then I will see what they look like at F7. There is a significant difference between the Antlia Ha 3 nm and the Optolong Ha 7 nm filter. I really want to try my Antlia 3 nm on Alnitak but the weather has been against me for months. I am mulling over getting the Hyperstar, but as it is 90 mm in diameter, I am a bit concerned that it will impact the amount of data going into it. So much to consider with AP!!
@@stephen2615 haven't analyzed signal yet, but reflections are very different from f/7 to f/2. I mean there is one less mirror in f/2, and we are talking about reflections...
I am in the process of analyzing the HyperStar data. Like you suggest, I think I am going to need that 15 sub data to make sense of what I am currently seeing. I was hoping to wrap up an analysis, but, like many science projects, I keep finding more questions. I will post part 2 soon.
Hey! Brent Paul here from HS group. Thanks Brent for that thorough analysis for f7. Regarding the contrast and background ADU and that 60% signal you’re getting. Both 6 and 12nm are almost identical on those background signals. All except for tighter and smaller stars which you have a clear results here. I’m guessing here but maybe the nebulosity may have some influence to its proximity to the horsehead designated as background? Would you think an Ha target that has a clear edge side in contrast with darker open space would yield a more isolated Ha signal and accurate ADU background?
Great question, I have a few other images from a different target, will take a look.
@@BrentMantooth Did a test on 12nm 1X300” and Ha and Sii showed halos on them imaging Alnitak Star at f1.9