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Infra red telescope and CCD

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#1 delorehal

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Posted 07 July 2020 - 01:25 AM

I'm waiting a OTA that was designed to work in the 1500nm (infra red) light.

I would like to know the lowest spatial frequency that astro cameras or DSLR can capture (deep red is 750nm IIIRC).

thanks



#2 james7ca

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Posted 07 July 2020 - 02:54 AM

I think those kind of wavelengths require special sensors, expensive and not normally available from the typical camera vendors.

 

Interestingly, there is a recent CMOS color camera from ZWO (ASI462MC) that is producing some interest from folks wanting to do IR imaging. It apparently has an usually high sensitivity to IR and works almost like a mono camera with a deep enough IR filter. But, it isn't that sensitive beyond about 1100nm.

 

Here is a link to the product page of the ASI462MC:  https://astronomy-im...t/asi462mccolor


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#3 sg6

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Posted 07 July 2020 - 03:36 AM

Seems that most sensors do not perform beyond 1000nm.

Try this link EdmundOptics  About 3/4 way down is a response curve of the Sony ICX285. Seems typical.

 

So that would means a somewhat specialised camera sensor from somewhere and that usually means a good few $'s.

 

Even at say 800nm the response is poor, just around 30% of that at 500nm. Suppose the low energy of the wavelengths are responsible for this. One of Einsteins papers covers this. Basically the longer the wavelength, the frequency is less so photon energy is less.

 

Scope, ignoring the sensor wavelength concerns, the scope would need to be pure reflector - any glass will alter wavelength focus and as adding a flattener is then almost out of it I half expect that means something like an RC.

 

Principle being you focus on a star and swing over to the real target and start collecting. As no glass the focal planes for visible and IR should be the same. Will be more complicated, isn't it always?

 

You could "build" a reflector with a camera at the secondary position although the image would likely not be flat. Would need a few trial/calibration runs with a flattener to focus on a star, then image the IR target, then adjust flattener for optimum IR image - And keep a good record of the adjustment required as each time you focused on a star you would need to apply the adjustment for the IR. Bit of a work around but should be an option and possibly less cost.

 

Other references:

BritAstro

 

Back to sensors: Do exist, looks like ones related to spectroscophy. P30-Hamamatsu

Seem to be InGaAs type (the doping I assume) and are linear not square/rectangular. Catch I can see is that you may find a sensor but maybe not an electronics board and would need software for a sensor. Hamamatsu do refer to a Dedicated Driver Circuit so you might find one.

 

Going to need a fair bit of searching. Or go find somewhere that does IR imaging and see what they have. One might just do what you want. And someone will have done the ground work. Be aware not all IR gets to us, there are assorted water absorbtion windows in the atmosphere. No good you wanting to image at one of those as the atmosphere has absorbed it all and you get nothing.

 

Strange thought: Ever thought of IR 35mm film ?


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#4 delorehal

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Posted 07 July 2020 - 01:39 PM

Thanks a lot for the advices and link

 

I don't have the required money to buy expensive cameras, so it is not an option for me.

 

The scope is a Meade SC 8" with special coatings on the corrector and additional lenses which make the lights rays parallel, so unfortunately it is not possible to use eyepieces. The seller get a nice image on the moon just putting his eye

 

So my idea is just experimenting using standard astro cameras, hoping they are still sensitive in the near IR



#5 delorehal

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Posted 07 July 2020 - 01:56 PM

 

 

Here is a link to the product page of the ASI462MC:  https://astronomy-im...t/asi462mccolor

This one is in my price



#6 delorehal

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Posted 07 July 2020 - 01:56 PM

Seems that most sensors do not perform beyond 1000nm.

Try this link EdmundOptics  About 3/4 way down is a response curve of the Sony ICX285. Seems typical.

 

 

 

 

Very informative site, thanks



#7 Narrowbandpaul

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Posted 07 July 2020 - 04:01 PM

Silicon doesn’t respond past 1um, so if your telescope blocks light shorter than 1.5um then you won’t have much joy from Si. In this regime it’s things like Ge, InGaAs, HgCdTe. All of which are exotic and hence expensive

#8 jamesNewmanF125

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Posted 07 July 2020 - 06:09 PM

This one is in my price

It's also a minuscule sensor, which is fine for planetary, if that's what you want to do IR for (which is common).




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