Thanks for your analysis. I have struggled with my Baader 3.5/4nm filters for fast optics on both RASA 8 and Samyang 135mm f/2.0. Different from the RASA 8, Samyang 135mm f/2.0 results were disappointing ( The target is Veil nebula, which is good for both Ha and Oiii). Now, I know the reason. Thanks again!
That's actually very accurate, I use this lens and you do notice that the signal does drop off in the corners as you describe. The lens really isn't setup to take a flat field like many of the telescopes out there so I always just thought that was the reason.
Thanks so much for your experimental approach regarding filter bandpass and f-ratio on a range of optics used for astro-imaging the results have enormous implications not just saving money. My own imaging set up uses a Samyang 135mm operating at f/2 but I have been using the vanilla 12nm Astronomik Ha filter both with a modified Canon 700D DSLR and more recently the smaller sensor ASI533MM-Pro. I haven't noticed vignetting with the dedicated 533 but often wonder if buying an Astronomik 12nm Ha MaxFR filter would realistically improve the collected Ha signal? Theory would suggest that a pre-shifted 12nm Ha filter should allow a higher passage of Ha photons at f/2 but perhaps the wide peak of the vanilla 12nm filter is broad enough to pass the light anyway? Lacking a spectrometer and realising the filter lottery out there with good, bad and indifferent samples being sold who knows or can even realise? Would you be able in the future to undertake similar testing comparing tbe performances of vanilla and MaxFR filters for users to make an informed decision over purchase? As you know the Max FR filters have a premium price and perhaps at f/2 for no practical advantage. Thank you again for all you have done on this topic. Regards, Steve
I don't have evidence of this, but I think part of the premium price of maxfr filters is the quality control astronomiks provides. Also, the qc matters way more for ultra narrowband where very slight error is catastrophic. At 12 nm bandwidth, the qc doesn't have to be as stringent to still work great.
I am not sure what you mean. if you are using the 6 nm filter, you could set the lens to f/2.6 as that is about what the filter will pass, and maybe it will give you a little extra depth of field for good focus? if you are using the 12 nm filter, you can set the lens to f/2 and get most of the light through the filter.
![Bandwidth choices for narrowband imaging with fast optics [4k]](http://i.ytimg.com/vi/rtFX92dZE_w/mqdefault.jpg)
Thanks for your analysis. I have struggled with my Baader 3.5/4nm filters for fast optics on both RASA 8 and Samyang 135mm f/2.0. Different from the RASA 8, Samyang 135mm f/2.0 results were disappointing ( The target is Veil nebula, which is good for both Ha and Oiii). Now, I know the reason. Thanks again!
That's actually very accurate, I use this lens and you do notice that the signal does drop off in the corners as you describe. The lens really isn't setup to take a flat field like many of the telescopes out there so I always just thought that was the reason.
Thanks so much for your experimental approach regarding filter bandpass and f-ratio on a range of optics used for astro-imaging the results have enormous implications not just saving money. My own imaging set up uses a Samyang 135mm operating at f/2 but I have been using the vanilla 12nm Astronomik Ha filter both with a modified Canon 700D DSLR and more recently the smaller sensor ASI533MM-Pro. I haven't noticed vignetting with the dedicated 533 but often wonder if buying an Astronomik 12nm Ha MaxFR filter would realistically improve the collected Ha signal? Theory would suggest that a pre-shifted 12nm Ha filter should allow a higher passage of Ha photons at f/2 but perhaps the wide peak of the vanilla 12nm filter is broad enough to pass the light anyway? Lacking a spectrometer and realising the filter lottery out there with good, bad and indifferent samples being sold who knows or can even realise? Would you be able in the future to undertake similar testing comparing tbe performances of vanilla and MaxFR filters for users to make an informed decision over purchase? As you know the Max FR filters have a premium price and perhaps at f/2 for no practical advantage. Thank you again for all you have done on this topic. Regards, Steve
I don't have evidence of this, but I think part of the premium price of maxfr filters is the quality control astronomiks provides.
Also, the qc matters way more for ultra narrowband where very slight error is catastrophic. At 12 nm bandwidth, the qc doesn't have to be as stringent to still work great.
If you don't have halos or issues, I don't think upgrading to maxfr will do anything for you.
Thanks very much for both replies, I really appreciate it. 👍
Thank you for this video! I have one question. Is there a way to measure where the break even point is in f stop between 6nm and 12nm?
I am not sure what you mean.
if you are using the 6 nm filter, you could set the lens to f/2.6 as that is about what the filter will pass, and maybe it will give you a little extra depth of field for good focus?
if you are using the 12 nm filter, you can set the lens to f/2 and get most of the light through the filter.