Filter for webcam

[Vox45]

I removed the lens from my Philips Toucam 750k and got the nose piece to fit it in the focuser. Any recommandation on the filter I should use ?

I still need to protect the sensor, so would clear glass be appropriate or should I go with something else ?

I understand that IR cut would help but I was told that an Astronomik ProPlanet 742 IR-pass filter would make object too dim. Would a simple IR cut like this be enough then ? Seems a bit expensive... I don't want to go overboard for a simple webcam.

Note that I would like to image the sun also, so this could be a game changer

[happy-kat]

Did you remove the infrared filter from in front of the sensor?

On my xBox webcam the filter is right against the sensor and separate to the lens I took off.

If not then you wont need a seperate filter as that would be double egging it.

The sun thing is different I don't have safe knowledge.

[JamesF]

I believe the Philips cameras have an IR rejection coating on the lens.  There is no separate IR filter as far as I'm aware.

However, the IR filter you suggest should be fine for planetary imaging.  I'd expect it to screw into the end of the nosepiece.  With an endcap on the nosepiece the filter will be protected when not in use and the sensor should not be exposed to the outside air.  This one would also work:

http://www.firstlightoptics.com/uv-ir-filters/baader-uvir-cut-filter.html

and this one too:

http://www.amazon.co.uk/Skywatcher-UV-CUTOFF-FILTER-1-25/dp/B00CA15RD2

I'm sure they'd be adequate for white light solar imaging too.

IR-pass and other narrow-band filters are probably best used with a mono camera.  I don't think I'd bother with them on a colour camera.

James

[Vox45]

I did not have to remove any filter on this camera, only the front lens, I thought that the filter was in the lens assembly actually.

Did not know about the coating you are talking about James. Good to know

These are way more expensive that I would have expected. I should have gotten this instead of just buying the nosepiece.

Ho well... live and learn

[happy-kat]

For solar does a filter/film go on the front of the telescope? At the start of the optical path?

[JamesF]

I did not have to remove any filter on this camera, only the front lens, I thought that the filter was in the lens assembly actually.

Did not know about the coating you are talking about James. Good to know

These are way more expensive that I would have expected. I should have gotten this instead of just buying the nosepiece.

Ho well... live and learn

There's always this one:

https://www.altairastro.com/product.php?productid=16440&cat=259&page=1

James

[JamesF]

For solar does a filter/film go on the front of the telescope? At the start of the optical path?

For white light solar the film filters go at the front of the OTA, yes.  As in the photo below.  I don't believe the solar film acts as an IR filter though, so having the IR filter in place at the same time is probably sensible.

James

[Vox45]

Found this info that might interest people

"The standard lens of a ToUcam has an IR-cut filterfoil on the backlens"

http://www.astro-imaging.de/astro/webcam_imaging_6.html

[Vox45]

Cool setup James

In my cast I have glass filter for solar. I hear that Baader film is better than glass. I'll look into this but then it's a DIY solution to attach it to the scope...

[happy-kat]

I will have a close look at my ToUcam later now

[JamesF]

I didn't find fixing the film holder to the OTA to be a problem to be honest.  It can be made a fairly snug fit -- certainly sufficiently so that if the wind were blowing hard enough to remove it then you'd be exceptionally unlikely to be imaging anyhow.

I have replaced that one now.  My second one I made from plastic rather than cardboard which makes it rather easier to attach a lanyard to stop the filter coming off (and also means I can replace the film at a later date without needing to make a new mount).

James

[Vox45]

I have a doubt now. I've seen a couple of times in the different description of the filter that

"Webcam / Video (Planets): Very good, if used with optics which contain refracting elements" (astronomik website)

Since I have an SCT is this filter needed or is it only on refractor that this filter is useful ?

[JamesF]

Well, you'll probably be using a barlow at some point.  They contain refracting elements.  Also, IR will be refracted by the atmosphere and will be picked up by the red photosites of the sensor potentially blurring the data from the visible red.  I suspect that's not a major issue, but even so it's complication you can do without.

And in fact if you have IR hitting the sensor at all, it will tend to overexpose the red compared with the blue and green.  For that reason alone you probably want it filtered out.

James

[Vox45]

Good point ! Did not think about the refracting elements of the barlow.

Very convincing arguments You know your stuff James.

Now I'm left with the matter of going overboard and buy a Baader at 43$£ or go with a inferior Altair one at 15£. Not sure that with a webcam I can get the full potential of the Baader.

Would it not be like puttingFerrari tyres on a Lada or would it worth it and get the most of my ccd sensor ?

[JamesF]

Now I'm left with the matter of going overboard and buy a Baader at 43$£ or go with a inferior Altair one at 15£. Not sure that with a webcam I can get the full potential of the Baader.

Would it not be like puttingFerrari tyres on a Lada or would it worth it and get the most of my ccd sensor ?

More like putting the Spirit of Ecstasy on a Trabant, perhaps.  You can always take it off and re-use it when you upgrade to a Skoda

James

[Vox45]

Yes because the opposite would be buying Lada tyres and put them on a ferrari when I get rich...

Unless someone speaks up and change my mind in the next hour, I'll go with the better one and futur proof myself It's not the 30£ difference on a 1500£ setup that should concern me