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I am looking at filters to be able to improve detail and contrast in my images and have my eye on the Optolong L-eXtreme/L-eNhance. I am using a Canon EOS600D DSLR attached to my telescope. I have Bortle 4 skies if it is any help. Which would be the best to go for? 

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Not sure if it's of any worth. But I've bought a 7nm svbony Ha-filter from ebay for around 170AUD (!). contrast and detail improvements are significant and works well for long exposures in my Bortle 8 backyard. The coatings are decent and haven't seen any reflection on really bright objects

Edited by TheMan
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Do you need filters for Bortle 4? I am in B6 and I don't use filters. I would rather remove gradients in processing than lose the detail with unnecessary filtering.

My local 'dark' site is B4. 😁

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I'd only use these dual/tri-band filters if I desparately want to take images of some emission nebulae with a 50%+ waxing or wanning moon in the sky. Generally speaking I don't like these filters and usually take a break when the moonlight is washing out everything. BTW I'm in Bortle 5.

 

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I am in bortle 4 and I use an l-enhance. I have used it successfully on both a DSLR (1100d and 700d both astro modded) and recently on a cooled dedicated astro-cam. In my opinion the L-enhance is a fantastic tool. With it imaging nebulae during bright moon becomes possible and that has been really important for me this winter when clear night have been almost exclusively around the full moon. Alsoby separating out the channels it is possible to produce very pleasing false colour (HOO) images.

 

I have not used an l-extreme so cannot speak from direct experience, but I have seen references to it being difficult to use with a DSLR.

 

Good luck.

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Thanks very much for the advice! The filter would mainly be to deal with the moon rather than light pollution. Could you not also produced HaRGB images by separating out the Ha from the OIII?

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  • 1 month later...

I use a L extreme with a 600D. It’s a great filter and works very well. Sometimes I think the filter is a bit much for the camera though, not sure if it’s just down to me, sensor temperature being high and seeing conditions  I’m still well in the early stages of post processing so haven’t figured out how to separate the channels for a false HOO yet. 
 

Hopefully I’ll be getting a OSC camera soon so looking forward to using it with that. 

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Posted (edited)
On 02/04/2021 at 10:32, Celestron4 said:

Thanks very much for the advice! The filter would mainly be to deal with the moon rather than light pollution. Could you not also produced HaRGB images by separating out the Ha from the OIII?

No, because the filter is largely opaque to blue if I'm not mistaken. What it gives you is an approximation to the HOO palette.

The first thing to ask is, how much Ha does your camera pass at the moment? This depends on how recent it is and/or on whether its modded. If its Bayer Matrix is blocking Ha it won't see the Ha passed by the filter anyway.

Then it's important to understand what filters do and don't do. They do not let you capture more Ha or OIII (or whatever) in a given time. What they do is isolate those wavelengths and block the rest of the light, allowing you to expose for longer without letting other light sources (either from the object itself or from polluting sources) swamp the signal from gas emission. This means that we use them for three reasons:

- To block LP including lunar LP.

- To block non-emission signal from emission nebulae so as to obtain higher contrasts which reveal structure in the gasses.

- To exclude LP and non-emission object signal so as to allow us to expose for long enough to capture very faint emission signal which we then stretch above the level of the background sky. (In reality it is not above the level of the background sky even at a dark site but, in processing filtered data, we can stretch it to make it brighter.)

The second two of these reasons make the use of the dual band filter valid even from a dark site but, in order to replicate an HaLRGB or HaOIIILRGB image you would need to shoot both filtered and unfiltered OSC and blend the two in the way that we do with conventional filters.

Olly

Edited by ollypenrice
typo
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