Comparing Baader to Chroma filters.....

[scitmon]

I too will watch with interest.  I would like to get into the world of mono + filters, but wouldn't have a clue what filters to go for.  

Would I be right in saying that comparisons between brands such as ZWO, Baader, Astronomik, etc are largely untested?  Would I be wrong to assume cost correlates to quality?

[RayD]

1 hour ago, scitmon said:

I too will watch with interest.  I would like to get into the world of mono + filters, but wouldn't have a clue what filters to go for.  

Would I be right in saying that comparisons between brands such as ZWO, Baader, Astronomik, etc are largely untested?  Would I be wrong to assume cost correlates to quality?

I don't think price is necessarily a direct or guaranteed recipe for quality.  However, as far as filters go, it does seem that the ones which appear to perform more consitently across a specified bandwidth do attract a higher premium.  This no doubt is due to the time that goes in to the development and production, but also the materials used and the quality testing (and rejection rates) etc.

Ultimatley the right filters for you will depend on your other equipment, environmet (sky quality and light pollution), expectations and realistic capabilities and, of course, budget.

All of the above mentioned filters have been shown to produce some superb images on here.  The ability of someone with exceptional processing skills and techniques would no doubt eek out far more detail and structure within a given data set from any filter than I can with even 'premium' ones.

It is perfectly acceptable, and standard practice, to start with a more cost effective set and then upgrade as your equipment and skill sets provide for you to utilise the potentially better data these higher grade filters can provide you with.  However, certainly at the beginning, it is highly unlikely that your choice of filter is going to be your limiting factor, or even amongst them.

Best of luck with the venture in to mono, it's a great and very flexible way of imaging.

Edited April 30, 2020 by RayD

[gorann]

Interesting thread, but I expect, as someone said, that the differece between expensive and very very expensive filters may be more apparent for NB filters. I wonder if anyone has any experience with the Baader Ultra-Narrowband 4.5nm OIII Filter? It is 40% of the price of the Chroma 5nm Oiii filter. Same question could of course be asked about the Baader 3.5 nm Ha filter (I have it but have no Astrodon or Chroma to compare it to).

[RayD]

22 hours ago, gorann said:

Interesting thread, but I expect, as someone said, that the differece between expensive and very very expensive filters may be more apparent for NB filters. I wonder if anyone has any experience with the Baader Ultra-Narrowband 4.5nm OIII Filter? It is 40% of the price of the Chroma 5nm Oiii filter. Same question could of course be asked about the Baader 3.5 nm Ha filter (I have it but have no Astrodon or Chroma to compare it to).

I had the 2" Baader 3.5nm Ha filter and sold it as I now have the 2" Chroma set.  The difference was very noticeable, with much more fine detail for the same integration on the Chroma.  They both do a very good job on filtering moon glow etc. as would be expected with such a narrow bandwidth, but the Chroma data is just so much more detailed and defined, but the stars are tiny specs.

Is it worth £700+ , almost 3 x the cost of the Baader?  I'm not sure I can provide emperical evidence that it is but the difference to my eye in the data, as would be expected at this price, is very noticeable.

Edited May 1, 2020 by RayD

[Davey-T]

Don't want to side track this thread but wondered if you have any thoughts on this filter Ray, I've got this Sharpstar HNT f/2.8 and supposedly fast scopes need filters that don't lose bandwidth especially when the light is turned through and angle, I don't pretend to understand the maths involved.

Planning on getting CMOS colour camera for it as focuser doesn't seem up to the task of supporting full frame and filters.

Dave

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

[RayD]

38 minutes ago, Davey-T said:

Don't want to side track this thread but wondered if you have any thoughts on this filter Ray, I've got this Sharpstar HNT f/2.8 and supposedly fast scopes need filters that don't lose bandwidth especially when the light is turned through and angle, I don't pretend to understand the maths involved.

Planning on getting CMOS colour camera for it as focuser doesn't seem up to the task of supporting full frame and filters.

Dave

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

I have looked at this exact filter a number of times for DLSR imaging, Dave, and it has some really good reviews.  I've been a little skeptical of multi-band filters myself, especially on colour cameras, but this really does seem to do what it says it does, and is almost the holy grail of filters for NB imaging!

I can't see why it wouldn't work at f/2.8 as they seem confident it has been designed to work up to f/2, although that doesn't say if that is the f/2 range, or exactly f/2.0.  Like you I don't pretend to understand the maths, but maybe someone like @vlaiv who does, can chip in with reasons why this one may work well where others have failed.

If you do get one I'd be interested to see your results as it is high on my list to get.

 

Edited May 1, 2020 by RayD

[Davey-T]

29 minutes ago, RayD said:

If you do get one I'd be interested to see your results as it is high on my list to get.

Will do, still trying to collimate the thing ATM and having read through the CN thread on it have now got a few mod's to perform 😁

Dave

[RayD]

19 minutes ago, Davey-T said:

Will do, still trying to collimate the thing ATM and having read through the CN thread on it have now got a few mod's to perform 😁

Dave

Well if mods are what are needed it has come to the right person! 😂

[vlaiv]

Issue with speed and narrowband filters is that speed of telescope is effectively negated by filters.

Focal length remains the same, but aperture decreases. It is the filter that decrease aperture of telescope.

Maybe a graph/image will explain this best:

Here we have one dielectric layer on the filter - made specifically for a certain wavelength of light. If light comes at an angle, then wavelength with respect to filter layers becomes smaller and interference won't work as expected. We get the same thing as if light had different wavelength.

Narrower the filter band pass - less angle it will tolerate. Solar Ha filters being extremely narrow band - like 0.5-0.7A and even smaller (that is 1/20 of single nm - or about x100 narrower then regular Ha for night time imaging) need almost collimated beam of light or something like F/30.

With fast lens some of the light is coming at shallow angle and some at steep. Filter will effectively block out all the light where angle is larger then some angle determined by filter band pass. Another image might help here:

If filter is very narrow and optics are fast - resulting stopping down of aperture can have more drastic impact on result then using wider band filter.