Filter size advice

[oymd]

Would be very helpful if someone can advice me on which filter size to get?

I'm pretty confused as to which will fit my setup?

I'm slowly assembling my setup, and have made up my mind on what to buy when ZWO have the camera back in stock:

SW ED80 Pro

ZWO ASI294MC Pro (trying to buy it used!! No luck so far)

ZWO ASI120MM as a guide camera attached to the 9x50 SW finder scope. 

I've settled on  the OPTOLONG L PRO filter to start with. 
At some point will buy a 5 slot EFW. I thought the EFWs have 2” slots, but when I checked it seems they are 1.5” or 36mm  

I was convinced that a 2” is necessary to avoid vignetting with the 294

So, will I be good to go with 1.25” filter size, or 2” will be a better fit for camera and my ED80?

thanks

 

Edited February 12, 2020 by oymd

[TerryMcK]

Most people go for 1.1/4” filters in filter wheels.

They are also a bit cheaper than the 2” versions especially for the very narrow bandwidth ones.

Edited February 12, 2020 by TerryMcK

[discardedastro]

If you're going to do narrowband at any point or think you might then go for a 7-slot EFW if you can: L, R, G, B, Ha, O, S.

1.25" filters are fine for a lot of sensors - once you go to larger sensors then you'll get vignetting. There is a handy calculator here: https://astronomy.tools/calculators/ccd_filter_size

[oymd]

34 minutes ago, discardedastro said:

If you're going to do narrowband at any point or think you might then go for a 7-slot EFW if you can: L, R, G, B, Ha, O, S.

1.25" filters are fine for a lot of sensors - once you go to larger sensors then you'll get vignetting. There is a handy calculator here: https://astronomy.tools/calculators/ccd_filter_size

Thanks

thats very helpful. 
 

would be great if you can advise the distance between sensor and filter?

i still do not have the system setup, so do not know the distance between filter and sensor?

is there a standard or common distance?

[discardedastro]

Generally your FW mounts direct onto the camera, so look at the diagrams for your desired FW and camera - they'll both have sensor-plane-to-edge/filter-mount-to-edge dimensions.

[oymd]

43 minutes ago, discardedastro said:

Generally your FW mounts direct onto the camera, so look at the diagrams for your desired FW and camera - they'll both have sensor-plane-to-edge/filter-mount-to-edge dimensions.

Thanks. I’ve just looked up the ZWO filter wheel, and it says distance between filter and sensor is 10mm. 
 

on the calculator that makes the 1.25” very ok. 
 

so there is the option of 8x1.25”

but then there is also a 7x36mm???

A 36mm filter? That is 1.4”

why is Astrophotography so so so confusing???

[discardedastro]

36mm tends to be unmounted - some filter manufacturers prefer it, and it does give you quite a bit more usable filter (the 1.25" filter will actually have less than 1.25" of usable filter diameter - check the spec sheet for the filter) because there isn't a mounting ring taking up some of the space.

[Gina]

If you can afford it, going for 32mm filters may future proof yourself in case you go for a larger sensor than 4/3in.  When I bought my Astrodon filters I was using relatively small sensors and went for 1.25" mounted.  Now I have the ASI1600MM-Cool with a 4/3" sensor which gives slight vignetting bit this is completely corrected with flats.

[oymd]

3 hours ago, Gina said:

If you can afford it, going for 32mm filters may future proof yourself in case you go for a larger sensor than 4/3in.  When I bought my Astrodon filters I was using relatively small sensors and went for 1.25" mounted.  Now I have the ASI1600MM-Cool with a 4/3" sensor which gives slight vignetting bit this is completely corrected with flats.

I mentioned in my first post above that the camera I am aiming for is a ASI294MC Pro. It also has a 4/3in sensor. 
Your advice is to go for 32mm filters. But aren’t those 1.25” as well?

many thanks

[david_taurus83]

Your buying a colour camera so why do you want a filterwheel? Get the 2" version as it's for colour imaging anyway so you can use it with a broad range of cameras should you choose.

[oymd]

Yes. Going for a OSC. 

I thought with OSC I could do narrowband? Ha, O3 & S2? And also plan on a L Pro for light pollution, so thought I would house them all in a filter-wheel. 
Obviously I could be planning all this completely wrong, hence the barrage of questions on my part.  

[Gina]

It doesn't work that way.  In fact LRGB filters and mono camera is better than an OSC.  An OSC will not only give you half the resolution for NB but have much lower sensitivity. 

[carastro]

Mono has much better sensitivity than colour, showing more detail.  Seems a shame purchase a filterwheel and filters and try to do narrowband on a colour camera.  I am not even sure it would work.

Get a mono camera and enjoy the better detail.

Carole