Where to place filters with the ASI533MC Pro

[Steve143]

I've just bought the 533 to replace my DSLR and I'm wondering where should I place the filters in my optical train. I have a UV/IR cut filter and the Optolong L-Pro and L-Extreme. My scope is an 80ED refractor with a 0.8x reducer/flattener. I also have a filter drawer that I'll use to change between the L-Pro and L-Extreme. All filters are 2" and I'm shooting from a Bortle 7/8 site. 

I was planning to place the UV/IR cut filter on the telescope end of my reducer/flattener and have the filter drawer between the telescope and the reducer/flattener. The schematic below shows how I plan to arrange the optical train. 

Is this the best way to place the filters or would you suggest a better layout?

Thanks!  

[Daf1983]

I am by no means an expert, but I don't think you would need both the l-pro/l-extreme and the uv/ir cut filter at the same time, it would be one or other. I have a similar setup, and use the l-enhance for nebula, and uv/ir filter for broadband, but never both together.

[bottletopburly]

You  could have used an 1.25’ filter in front of the AR window you get an  m42 adapter that screws in the first spacer , but if you’ve got 2’ then that’s fine as above you only need one of the above filters in the train .

[SoftwareDeveloper]

Using more than one filter at a time is usually counter-productive. Since the ASI533MC is a COLOR camera it already has one filter above each pixel. So.. adding more filters is likely to just make frustrating imaging. Here is a more/less typical bayer filter for a COLOR camera:

https://micro.magnet.fsu.edu/primer/digitalimaging/images/cmos/cmoschipsfigure4.jpg

Because the pixels sensitive to each of the "human eye" perceived colors tend to reject light at other colors, a filter placed in front of the bayer filter will usually only allow 1/4 of the pixels see light (if the light passed through the new filter is predominantly red or blue Rg/gb or rg/gB ). So the result is to discard 3/4 of your sensor! Woops, not usually a good idea. If the filtered light is in the green bandpass 2/4 (rG/Gb) of the pixels will "see" the light. Better, but not a lot. The idea of discarding half of a sensors data is well..

That is why astronomy cameras are usually not color. Then ONE filter at a time makes sense. Where to put it? As close to the sensor as is practical.

I suggest that the color camera will get nice photos and should get nicer photos with no additional optical filters. After the images have arrived in the computer, feel free to manipulate those colors any way you like

Hope that makes sense. Save your filter budget for a monochrome camera, the results will be better as ALL the pixels can measure the light that gets through whatever filter you use, and now the meaning of the pixels is vastly easier to understand.

Hopefully that makes sense.

[adyj1]

Check out the ASI website, they have diagrams to show the layout of spacers and filters. You'll need the filters in front of the flattener and as a bonus that will help make up the the 55mm (or so) space needed between sensor and flattener. 

Edited July 29, 2022 by adyj1

[bottletopburly]

I use an L extreme on my zwo533mc and it works very well , also a Uv filter when not using the L extreme ,I  use those in a zwo  filter wheel so I don’t need  faff about 👍

Edited July 29, 2022 by bottletopburly

[Adam J]

3 hours ago, Steve143 said:

I've just bought the 533 to replace my DSLR and I'm wondering where should I place the filters in my optical train. I have a UV/IR cut filter and the Optolong L-Pro and L-Extreme. My scope is an 80ED refractor with a 0.8x reducer/flattener. I also have a filter drawer that I'll use to change between the L-Pro and L-Extreme. All filters are 2" and I'm shooting from a Bortle 7/8 site. 

I was planning to place the UV/IR cut filter on the telescope end of my reducer/flattener and have the filter drawer between the telescope and the reducer/flattener. The schematic below shows how I plan to arrange the optical train. 

Is this the best way to place the filters or would you suggest a better layout?

Thanks!  

there is a 1.25 inch filter adaptor included with the camera, dont need to spend your cash on 2 inch filters.

Adam

Edited July 29, 2022 by Adam J

[adyj1]

19 hours ago, adyj1 said:

Check out the ASI website, they have diagrams to show the layout of spacers and filters. You'll need the filters in front of the flattener and as a bonus that will help make up the the 55mm (or so) space needed between sensor and flattener. 

Here's the link to the ZWO page that explains the spacing (assuming your flattener requires 55mm)

https://astronomy-imaging-camera.com/tutorials/best-back-focus-length-solutions-55mm.html

[MonsterMagnet]

Sorry to bump this old topic but I am looking at purchasing the ASI553MC Pro and just want to clarify what filters I'll need.

I currently have an L'Extreme and an L'Pro (both 2 inch) that I can screw into the flattener to use with my DSLR.  I assume I can continue to do this and image with the 533 without an IR cut filter.  However if I am in a darker site (I usually image from central London which is Bortle 9) I probably won't want to use the L'Pro so I'll need an IR cut filter in these circumstances right?

Is there any benefit to getting a 2 inch IR cut filter as opposed to the 1.25 inch and using the adapter?

Thanks.

MM.

[adyj1]

On 30/07/2022 at 13:22, adyj1 said:

Here's the link to the ZWO page that explains the spacing (assuming your flattener requires 55mm)

https://astronomy-imaging-camera.com/tutorials/best-back-focus-length-solutions-55mm.html

Firstly, an update to the link: The best solution of 55mm back focal length – ZWO ASI (astronomy-imaging-camera.com)  (I can't edit the post)

 

24 minutes ago, MonsterMagnet said:

I assume I can continue to do this and image with the 533 without an IR cut filter

Yes, use the IR cut filter on it its own on suitable targets.

As for whether 2" or 1.25" - it would be your choice. I'd have thought that the 2" would be  more convenient for you as you will need a bigger filter if you upgrade your camera to a one with a larger sensor (esp. as the cost difference between the two sizes for UV/IR is much smaller than other filters).

HTH

Ady 

 

[MonsterMagnet]

21 minutes ago, adyj1 said:

Firstly, an update to the link: The best solution of 55mm back focal length – ZWO ASI (astronomy-imaging-camera.com)  (I can't edit the post)

 

Yes, use the IR cut filter on it its own on suitable targets.

As for whether 2" or 1.25" - it would be your choice. I'd have thought that the 2" would be  more convenient for you as you will need a bigger filter if you upgrade your camera to a one with a larger sensor (esp. as the cost difference between the two sizes for UV/IR is much smaller than other filters).

HTH

Ady 

 

 

Thanks!

That makes everything pretty clear.  I'll grab a 2 inch IR cut filter for when I'm outside of London and then just screw that into the flattener in place of the L'Pro or L'Extreme.  I'm sure I'll upgrade at some point in the future but taking it in steps.

MM 

[Elp]

If the targets high enough you should be able to image with the UV/IR cut (luminence filter, it reduces IR bloat mostly around stars) from home depending on how bad the local lighting is, certainly with galaxies. I'm in a similar situation, RGB is usually difficult, post processing software like Siril can remove any skyglow gradient (usually) via background extraction.

Edited July 6, 2023 by Elp