IR pass filters - advice on use

[Stub Mandrel]

I've got hold of  a 695nm IR pass filter.

It looks awfully dark!

I understand that with my mono camera this shoudl allow me to overcome bad seeing ... but what sort of exposures can I expect?

A quick trial with a mono cam with IR/UV filter removed suggests I need exposure about 3 times taht with no filter at all. Is that about right?

 

Can anyone with experience of these offer any advice.

[Louis D]

I have a Hoya R72 filter for infrared photography that only passes wavelengths above 720nm.  It's cool to take photos of people and foliage through it.  When used with a digital camera that has had its IR blocking filter removed, there really wasn't much of an increase in exposure times during bright sunlight thanks to the immense amount of IR present.  In live view mode, it's really cool to see the world in IR in real time.

For astronomy, that filter you describe would be blocking H-alpha emissions at 656nm, so I'm not sure what interesting emissions you'd be capturing with it.  Perhaps for solar imaging?

[Stub Mandrel]

12 minutes ago, Louis D said:

I have a Hoya R72 filter for infrared photography that only passes wavelengths above 720nm.  It's cool to take photos of people and foliage through it.  When used with a digital camera that has had its IR blocking filter removed, there really wasn't much of an increase in exposure times during bright sunlight thanks to the immense amount of IR present.  In live view mode, it's really cool to see the world in IR in real time.

For astronomy, that filter you describe would be blocking H-alpha emissions at 656nm, so I'm not sure what interesting emissions you'd be capturing with it.  Perhaps for solar imaging?

Sorry, should have mentioned - it's for planetary imaging.

[symmetal]

I have the Baader 685nm IR-Pass filter which I bought recently due to its recommendation for planetary imaging to reduce the effect of seeing and get sharper results, using it as the luminance channel with a normal RGB image added.  However with my 4 inch scope with 4x Powermate  which is f25 the image is far too dark at exposures faster than around 200mS so is not much use for my setup. For a larger aperture  scope it would be OK. I'll have to get my 10" LX200 set up and have a go with that when I've got it's shed built. The filter works well for videoing the moon though with my 4 inch and 2x Powermate.

[johninderby]

Just bought the Altair 685nm IR pass filter which seems to be the same as the Baader but a bit cheaper. Will be using it with my Skymax 180.

 

 

[Louis D]

1 hour ago, Stub Mandrel said:

Sorry, should have mentioned - it's for planetary imaging.

Ah, I understand now.  Did some quick reading up on the subject.  There doesn't seem to be a simple answer to the best usage of these.  To my eye, the red filters already seem to do a very good job of capturing fine details.

[Stub Mandrel]

28 minutes ago, Louis D said:

Ah, I understand now.  Did some quick reading up on the subject.  There doesn't seem to be a simple answer to the best usage of these.  To my eye, the red filters already seem to do a very good job of capturing fine details.

? As Darryl is imaging in the Australian desert with impeccable transparency and seeing, I'm not hugely surprised he sees no great benefit from using an IR-Pass!

[Louis D]

5 hours ago, Stub Mandrel said:

? As Darryl is imaging in the Australian desert with impeccable transparency and seeing, I'm not hugely surprised he sees no great benefit from using an IR-Pass!

I was thinking that since Jupiter emits so much IR, it might be useful on it to pick up details otherwise invisible in the visible wavelengths: