Hoya red intensifier on full spectrum dslr

[mislav]

hello..i am wondering how succesfull would be Hoya red intensifier filter on full spectrum dslr (nex5). Lets say imaging of orion nebula from city Borle 7 scale? Do i have to put UV filter also (because of lens and UV and IR diferent wavelengts?). Would it be to red on full spectrum? btw lens isnt sometthing spectacular for now- old canon fd 100-300mm F5.6 telelens... Waiting for vivitar 135mm f2.8 lens.... But both lens should have some help in this light polution.... I also have svbony 2inch uhc filter, but its doing great vigneting on all lenses ( most of them are 58mm filter width).

[Thalestris24]

59 minutes ago, mislav said:

hello..i am wondering how succesfull would be Hoya red intensifier filter on full spectrum dslr (nex5). Lets say imaging of orion nebula from city Borle 7 scale? Do i have to put UV filter also (because of lens and UV and IR diferent wavelengts?). Would it be to red on full spectrum? btw lens isnt sometthing spectacular for now- old canon fd 100-300mm F5.6 telelens... Waiting for vivitar 135mm f2.8 lens.... But both lens should have some help in this light polution.... I also have svbony 2inch uhc filter, but its doing great vigneting on all lenses ( most of them are 58mm filter width).

Probably not much I think, but you're welcome to try. A full-spectrum modded camera will have an increased sensitivity at the red end of the spectrum but you will need a UV/IR cut filter, or lp filter (which also cuts uv/ir), or a uhc filtr plus ir cut, mainly to cut otherwise invisible IR. Really, an Ha narrowband filter is best for highlighting Ha emission nebulas but I suggest you try and see. You need to take flats to calibrate out vignetting.

Louise

[mislav]

i will try ofcourse.... did anybody tried all ready? i dibt know what to expect.... also, two filters in astrophoto-what do you think???

[Thalestris24]

Well, I doubt many people would use a photo filter for astro - they aren't designed for it so you might get reflections or other aberrations. I've used infra red photo filters with some success - they are excellent for cutting out light pollution but only give black and white and no nebulas or galaxies...  You can try doubling up filters - just check the transmission spectrum for each filter first.

Louise

[mislav]

i am looking at transmision curve of hoya intwnsifier and it says that it blocks (letting 20%) of red light with wavelenght above 700-750... do i have to use ir filter on full spectrum.camera? i will try with and without uv/ir....i am afraid of looaing image quality woth two filters....and loose some exposure time (make it longer)...

[Thalestris24]

Hi Mislav

Is it this filter? I think it does transmit in the near infra-red so ideally you'd need an IR filter with it to prevent star bloats with long exposures. But it might be ok for lots of shorter exposures. I would just try it and see. As far as I know, it's not a common filter used in AP so you may not find anyone else here that uses it. How does your nex5 perform? Would like to see some of your shots!

Regards

Louise

[mislav]

jes thats that filter....thnx...i dont have equipment for longer then 30sec.... IR are doing star bloats??? I tought UV so just wanted to ask would just UV filter be enough :)... obviously not enough...

[Thalestris24]

9 minutes ago, mislav said:

jes thats that filter....thnx...i dont have equipment for longer then 30sec.... IR are doing star bloats??? I tought UV so just wanted to ask would just UV filter be enough :)... obviously not enough...

Hi

I think dslr camera sensors are generally more sensitive to IR than UV. You're unlikely to get any problems from just UV generated by stars. However, most astrophotography filters ('ccd' type) are UV/IR cut and just let the visible spectrum through, including H-alpha and, usually but not always, SII. You can see that the RA54 transmission curve cuts off quite sharply at the start of the UV but extends up to nearly 750nm in the near IR. So IR is potentially your biggest problem. However, at only 300mm and 30s, IR effects might not show too much anyway, which is why I said to give it a try .

Do post some of your images!

Louise

[mislav]

ofcourse....when clouds go away... ill try it with 135 vivitar

[Thalestris24]

Just now, mislav said:

ofcourse....when clouds go away... ill try it with 135 vivitar

At 135mm you probably won't have any star bloat problems!

[mislav]

So bloating is here obviously..this is just HOYA red intensifier..but ok-UV/IR filter will do it, but i have another strange problem. This quadrangular shadow on edges. I did about 100 20sec lights, 20 darks and 20 flats...are flats wrongly done (blank white laptop screen 1/10 exposure), or filter problem, or is it possible that shadow is here because i cleaned sensor recently (but i get nice picures and when i put dehaze and clarity to max i dont get any of this problems)