Filter Wheel
When I opted for the ATIK 460EX mono camera, I obviously needed to use filters to make colour images, whether it be RGB or Narrow Band. I did not have to think too much about it - the ATIK EFW2 was manufactured by the same company as the camera and was getting good reviews. I bought this with a 5 slot 2" carousel - thinking that if I bought the bigger filters (not the 1.25" that would have been OK for the camera), then I would not be too concerned if I ever upgraded to a bigger chip imager. (As ever, I think ahead and cover the options. Sometimes this pays off......sometimes it is just a waste of money!)
Re the EFW2 - I have been using this filter wheel for several years now and have never had any problems. It gets a 'thumbs up' from me. (In fact I now have a second one so that I do not have to handle the filters - one used for RGB and the other for NB filters. Changing out filters becomes very easy also.....otherwise an Allen key would have to be used to open up the EFW2).
In 2018 I have added an EFW3 Filter Wheel. I use the EFW3 on the permanent set up in the observatory with 50mm filters for the Takahashi FSQ 130 ED. I still have & use the EFW2 and use it with 1.25" filters for the FSQ 106 ED. (Note some changes from the original set-up but still very happy to continue using Atik filter wheels).
Re the EFW2 - I have been using this filter wheel for several years now and have never had any problems. It gets a 'thumbs up' from me. (In fact I now have a second one so that I do not have to handle the filters - one used for RGB and the other for NB filters. Changing out filters becomes very easy also.....otherwise an Allen key would have to be used to open up the EFW2).
In 2018 I have added an EFW3 Filter Wheel. I use the EFW3 on the permanent set up in the observatory with 50mm filters for the Takahashi FSQ 130 ED. I still have & use the EFW2 and use it with 1.25" filters for the FSQ 106 ED. (Note some changes from the original set-up but still very happy to continue using Atik filter wheels).
EFW2
EFW3
Filters
My filters initially were all by Astronomik of Germany. As stated above, I went for the 2" filters so that if I ever upgraded the camera to a larger chip, I would not have to think about changing out the filters also - they would be big enough. I honestly cannot remember when exactly I bought each set or whether I even bought the narrow band filters individually or not. I do know however, that I bought all of the filters new - the NB ones direct from the manufacturer. An external link to the Astronomik web site is HERE, with all information you might require - including prices. I purchased the 12nm type NB filters.
As stated elsewhere, Narrow Band photography became my main interest and for sure the most productive for this moderately light polluted location in a residential area. Over a long period, I gradually came around to the idea that I should spend the money on the best NB filters I could buy. The difference was evident in images I was looking at on the internet from other amateurs. the Astrodon 3nm filters (from U.S.A.) were now on my list....but they were really expensive. Link to Astrodon website HERE. These, I did buy in 2015 and have not regretted the expenditure. In order to continue using the Atik EFW2 filter wheel I needed a new carousel for the 50mm Astrodon filters - they don't make them in 2" format. More expense!
Now, (2016) I use the Astrodon (3nm) filters for most of my shots and use the Astronomik RGB filters just occasionally. (Since buying the 3nm Ha - I would advise a 'would be' purchaser not to discount the 5nm Ha which permits that little extra bit of signal through - which better enhances some nebulae).
In 2018 I have now sold my Astronomik filters and use solely Astrodon. I have 50mm LRGB Ha Sii OII in the EFW3 filter wheel and a similar array of 1.25" filters in the EFW2 filter wheel. The 50mm NB filters are 3nm whereas the 1.25" NB filters are 5nm.
As stated elsewhere, Narrow Band photography became my main interest and for sure the most productive for this moderately light polluted location in a residential area. Over a long period, I gradually came around to the idea that I should spend the money on the best NB filters I could buy. The difference was evident in images I was looking at on the internet from other amateurs. the Astrodon 3nm filters (from U.S.A.) were now on my list....but they were really expensive. Link to Astrodon website HERE. These, I did buy in 2015 and have not regretted the expenditure. In order to continue using the Atik EFW2 filter wheel I needed a new carousel for the 50mm Astrodon filters - they don't make them in 2" format. More expense!
Now, (2016) I use the Astrodon (3nm) filters for most of my shots and use the Astronomik RGB filters just occasionally. (Since buying the 3nm Ha - I would advise a 'would be' purchaser not to discount the 5nm Ha which permits that little extra bit of signal through - which better enhances some nebulae).
In 2018 I have now sold my Astronomik filters and use solely Astrodon. I have 50mm LRGB Ha Sii OII in the EFW3 filter wheel and a similar array of 1.25" filters in the EFW2 filter wheel. The 50mm NB filters are 3nm whereas the 1.25" NB filters are 5nm.
There is some good information on Astrodon NB filters in the following from Astrodon :
Astrodon Narrowband filters set a new bar of performance and durability for imaging and research. The narrow 5 and 3 nm bandwidths enhance contrast of emission targets by lowering your background signal. The guaranteed >90% transmittance at the emission wavelength provides you with the highest signal available. This guaranty is expensive to manufacture for such spectrally narrow filters, but it assures you in writing on each filter box that you will get what you paid for. These two factors combine to provide you with the highest contrast available. Our latest narrowband filters are typically achieving >95-98% transmittance. Astrodon Narrowband filters are renowned for minimizing halos around bright stars, even for long exposures of 30-45 minutes typical of narrowband imaging in astrophotography. Lastly, Astrodon Narrowband filters are coated to the edge of the part and are edge blackened. This is critical to minimize stray light for a filter that blocks most light except for the narrow bandpass.
Astrodon Narrowband filters for imaging are all about contrast. What do we mean by this? Contrast brings out faint features by reducing the background - the narrower the filter, the better. The problem is keeping the signal (%T at the emission line) constant as the filter becomes spectrally narrower. This is why our >90%T guarantee is so important, even though it becomes very costly to manufacture. But, this assures you that you can take advantage of the improved contrast with our narrower filters compared to the much less expensive 7- 8.5 nm filters on the market. You can see the increase in contrast in the sequence of equal-exposure images of the Crescent Nebula (NGC 6888) taken on the same system and on the same night. As the bandwidth becomes narrower, the nebula "pops" out of the background, as does the faint surrounding nebulosity. Actually, the >90%T is a legacy specification, since new production technologies employed over the past 3-4 years routinely produces 97-98%T at the emission wavelengths.
Random tests of a competitor's low-cost 7 nm H-a filter showed %T values ranging from 86% down to 71%. Random selection of 5 nm Astrodon filters measured %T values at the H-a emission wavelength of 93, 98, 97 and 98%. You will never know that you are using their 71% filter compared to a 97% Astrodon filter because they do not guarantee this important performance parameter. They recently came out with a 3.5 nm H-a narrowband filter and those results are even worse, ranging from 3-70% at the emission wavelength. Similarly, analysis of different 2016 lots of Astrodon 3 nm H-a filters measured 97, 97, 97 and 96%T. Yes, our filters are more expensive, but you always know what you are getting with Astrodon Narrowband filters - the best performance in the market - guaranteed. Our recent blueshift data show that Astrodon 3 and 5 nm filters can be used with nearly all systems as fast as f/3.5 with virtually no loss in emission signal, so you do not need to buy custom "upshifted" filters if you have both fast and slow systems.
Note: I believe (early 2018) that Astrodon filters are no longer going to be made/marketed under this brand name.
Astrodon Narrowband filters for imaging are all about contrast. What do we mean by this? Contrast brings out faint features by reducing the background - the narrower the filter, the better. The problem is keeping the signal (%T at the emission line) constant as the filter becomes spectrally narrower. This is why our >90%T guarantee is so important, even though it becomes very costly to manufacture. But, this assures you that you can take advantage of the improved contrast with our narrower filters compared to the much less expensive 7- 8.5 nm filters on the market. You can see the increase in contrast in the sequence of equal-exposure images of the Crescent Nebula (NGC 6888) taken on the same system and on the same night. As the bandwidth becomes narrower, the nebula "pops" out of the background, as does the faint surrounding nebulosity. Actually, the >90%T is a legacy specification, since new production technologies employed over the past 3-4 years routinely produces 97-98%T at the emission wavelengths.
Random tests of a competitor's low-cost 7 nm H-a filter showed %T values ranging from 86% down to 71%. Random selection of 5 nm Astrodon filters measured %T values at the H-a emission wavelength of 93, 98, 97 and 98%. You will never know that you are using their 71% filter compared to a 97% Astrodon filter because they do not guarantee this important performance parameter. They recently came out with a 3.5 nm H-a narrowband filter and those results are even worse, ranging from 3-70% at the emission wavelength. Similarly, analysis of different 2016 lots of Astrodon 3 nm H-a filters measured 97, 97, 97 and 96%T. Yes, our filters are more expensive, but you always know what you are getting with Astrodon Narrowband filters - the best performance in the market - guaranteed. Our recent blueshift data show that Astrodon 3 and 5 nm filters can be used with nearly all systems as fast as f/3.5 with virtually no loss in emission signal, so you do not need to buy custom "upshifted" filters if you have both fast and slow systems.
Note: I believe (early 2018) that Astrodon filters are no longer going to be made/marketed under this brand name.
