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OSC filter choices


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So I have a new shiny 533mc pro along with a zwo filter drawer and a optolong L extreme 2 inch.

what other filters if any should I consider I live in a bortle 6 area but its higher where I live due to some lights that are on permanently all night behind my garden,.(ongoing saga with local authorities to get them on a sensor ...)

initial use will be with a WO z73 and later an Edge hd 8 .

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You don't need anything together with the L-extreme, but if you plan on using the camera for broadband, then an IR/UV filter as a minimum is desirable as the camera itself has a plain window. It'll tighten up the stars. I can't offer advice on light pollution filters.

Ian

Edited by The Admiral
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7 hours ago, The Admiral said:

You don't need anything together with the L-extreme, but if you plan on using the camera for broadband, then an IR/UV filter as a minimum is desirable as the camera itself has a plain window. It'll tighten up the stars. I can't offer advice on light pollution filters.

Ian

This is correct, a UV/IR cut filter is required to reduce star bloat if you are using a refractor. The Baader UV/IR filter worked great with my 120mm refractor and ASI533MC. For some reason, the Astronomik L-2 didn't do much at all (perhaps the L-1 or L-3 was more suitable for my setup). 

Op, if your local lights are white LED's then there is no light pollution filter that will filter them out without also affecting broadband targets (like galaxies and reflection nebula). Light pollution filters can work great if your street lights are the orange sodium type because the filters will just block out that wavelength. 

Some people talk about the Optolong L-Pro filter but I don't have any personal experience with this. 

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19 minutes ago, Richard_ said:

the Astronomik L-2 didn't do much at all (perhaps the L-1 or L-3 was more suitable for my setup). 

Op, if your local lights are white LED's then there is no light pollution filter

Hmm, interesting. I use the L2 and I haven't come to that conclusion. Mind you, I've not done a comparison, nor much broad band imaging to be honest. (See https://stargazerslounge.com/uploads/monthly_2022_07/Light_M13_60.0s_Bin1_gain100_20220710-000225_-10.0C_0035.jpg.88e32ed0ffb2485f5b03680e154ecd51.jpg)

Ian

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Just regarding the idea of using the 535 MC Pro with an 8 inch Edge: even with a 0.7 reducer this would give you an image scale of 0.55"PP.  (Do check my sums.)  In all probability this means you would be oversampling by at least three times. This doesn't really add up, to my mind. You could have a shorter focal length, a wider field and no loss of real resolution.

Olly

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1 hour ago, The Admiral said:

Hmm, interesting. I use the L2 and I haven't come to that conclusion. Mind you, I've not done a comparison, nor much broad band imaging to be honest. (See https://stargazerslounge.com/uploads/monthly_2022_07/Light_M13_60.0s_Bin1_gain100_20220710-000225_-10.0C_0035.jpg.88e32ed0ffb2485f5b03680e154ecd51.jpg)

Ian

Yeah, Astronomik offer the L filters in three series (L-1, L-2 and L-3) and which one you use, depends on the amount of chromatic correction your telescope requires. You have to choose the right filter for your situation. In my case I chose L-2 as that is the middle ground.

Below are some test images on stars in the following order (captured with WO FLT120 with a Flat68III x1.0 flattener):

  • Left = Astronomik L-2
  • Centre = No filter
  • Right = Baader UV-IR filter

Each image was captured after running an autofocus routine with an exposure time of 60s. Each row of images have been autostretched and zoomed in to the same scale as their neighbours. As you can see, the stars from the Astronomik L-2 and no filter are very similar, whereas the Baader UV-IR filter produces sharper stars. This is obvious in the first image where the divide between both stars is more prominant (although atmospheric dispersion is now more visible with baader filter). In my imaging system, perhaps the L-1 would have been more suitable.

In short, the Baader UV-IR was the winner for me 👍

M81.thumb.PNG.b7f00ad055185c8627428e0563825953.PNG

 

M81_2.thumb.PNG.7109e0fdeb02aefe89dc2adc94a4d460.PNG

 

UGC7306.thumb.PNG.b4aa1d917a2bc584d54db7d7d5c16235.PNG

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