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Old 31-12-2012, 10:16 AM
mbaddah (Mohammed)
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Omega Optical RGB filters for planetary imaging?

Hi,

Was wondering are the following RGB filters from Omega Optical suitable for planetary imaging with mono camera or are they suitable only for visual use?

http://www.ebay.com.au/itm/310364932...9#ht_927wt_648
http://www.ebay.com.au/itm/150717549...9#ht_891wt_648
http://www.ebay.com.au/itm/150717527...9#ht_911wt_648

Would appreciate any help, thanks
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Old 31-12-2012, 08:39 PM
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Shiraz (Ray)
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they are probably OK, but they are not a brand that I have seen used by planetary imagers.
The majority seem to use Astronomik (although certainly not all) - which are about the same price as the Omega Optical filters.
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Old 02-01-2013, 10:13 AM
mbaddah (Mohammed)
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Quote:
Originally Posted by Shiraz View Post
they are probably OK, but they are not a brand that I have seen used by planetary imagers.
The majority seem to use Astronomik (although certainly not all) - which are about the same price as the Omega Optical filters.
Hi Ray,

The Omega Opticals are considerably cheaper than the Astronomik which is why I was thinking of buying them. The Astronomik/Astrodons are over $500 for a set of 2" filters! Definitely a lot more than I want to spend...
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Old 02-01-2013, 02:55 PM
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Shiraz (Ray)
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Quote:
Originally Posted by mbaddah View Post
Hi Ray,

The Omega Opticals are considerably cheaper than the Astronomik which is why I was thinking of buying them. The Astronomik/Astrodons are over $500 for a set of 2" filters! Definitely a lot more than I want to spend...
Sorry Mohammed, I didn't notice the filter size - assumed you would be looking at 1.25 for planetary. Your choice, but you really don't need 2inch filters for planetary imaging (where you will be using a tiny chip at f25).

From my limited experience, things that I would watch out for with any filters you buy are:
1. AR coating on the non-filter side to maximise transmission and remove any possibility of image-destroying reflections - the sharpening process can enhance even slight step anomalies in planetary images - big problem,
2. hardness of the coatings (you will need to be able to clean them when imaging at f25)
3. supression of IR leakage, which can muck up colour rendition. If you need to put in a separate UV/IR blocking filter, you will lose sensitivity and increase cost.
4. quality of the substrate - it is nice to have truly parfocal filters so that you do not need to refocus between colour runs - you will only get that if the maker has paid close attention to the substrate optical quality.

The relatively low in-band transmission of the Omega filters suggests that they possibly do not have AR coating on the back side. they also do not show transmission curves out to 1 micron, so there is incomplete data on IR blocking. If you do decide to buy them, would be worth checking with the makers to determine if they are AR and have full IR blocking.

Last edited by Shiraz; 03-01-2013 at 12:28 AM.
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Old 03-01-2013, 09:02 AM
mbaddah (Mohammed)
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Hi Ray,

I should have been more clear that I was after 2" filters so that they may fit in my filter slider (not using a wheel).

Thanks for the informative response. It looks like it isn't worth spending the money on the cheap filters and one is better off saving for the Astronomik/Astrodon/Baadar filters instead? The Orion LRGB set was looking tempting but i'm not so sure now

Thanks again.

Quote:
Originally Posted by Shiraz View Post
Sorry Mohammed, I didn't notice the filter size - assumed you would be looking at 1.25 for planetary. Your choice, but you really don't need 2inch filters for planetary imaging (where you will be using a tiny chip at f25).

From my limited experience, things that I would watch out for with any filters you buy are:
1. AR coating on the non-filter side to maximise transmission and remove any possibility of image-destroying reflections - the sharpening process can enhance even slight step anomalies in planetary images - big problem,
2. hardness of the coatings (you will need to be able to clean them when imaging at f25)
3. supression of IR leakage, which can muck up colour rendition. If you need to put in a separate UV/IR blocking filter, you will lose sensitivity and increase cost.
4. quality of the substrate - it is nice to have truly parfocal filters so that you do not need to refocus between colour runs - you will only get that if the maker has paid close attention to the substrate optical quality.

The relatively low in-band transmission of the Omega filters suggests that they possibly do not have AR coating on the back side. they also do not show transmission curves out to 1 micron, so there is incomplete data on IR blocking. If you do decide to buy them, would be worth checking with the makers to determine if they are AR and have full IR blocking.
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