Moon - IR pass filters

[Astroscot2]

Hello all.

Ive found a renewed interest in imaging the planets and the moon since the Mars opposition,  I purchased a new camera for the purpose the QHY462C and im so far pleased with the results,  The camera came with an IR pass filter, 850nm which Ive tried on a few occasions to image the moon with variable results, the images seem to have a softness to them and I wonder whether the filter is at all effective or is it my lack of experience.

My understanding from what Ive read is that imaging in IR reduces the effect of atmospheric turbulence however it also at the same time reduces the image resolution?  I also find I need to increase the exposure which in turn results in a lower frame rate and makes me wonder if its the right filter for the job?

Ive not had a chance to make image comparisons with the IR filter insitu against the UV/IR blocking filter.  I also note that Antalia offer a 650nm filter which I assume would produce a brighter image and therefore allowing faster frames rates.

 

I just wondered what seasoned lunar imagers are using, I have a couple of example images on my Flikr account as examples of the softness I seem to have to my images, The scope is well collimated and optics clean.

 

Thanks

Mark

[knobby]

That's an interesting camera, had to google it ... It syas It's like a OSC and Mono all in one.

The bayer matrix is apparently transparent to light over 850nm so in theory, for your sensor anyway, it shouldn't effect resolution.

As you've realised, using the IR pass will cut down on the  amount of light hitting the sensor therefore needing longer exposure times.

How are you capturing ? your images look very nice on Flickr, maybe the Lunar pics could take more sharpening ?

[Astroscot2]

Hello, Im using Sharpcap for capturing,  Ive not been able to get the frame rate much over 55fps as im having to increase the exposure. I will try a few experiments

with and without filter and compare results.  I could possibly try more sharpening in post, the images do have a dreamy softness to them.

 

Mark

[symmetal]

Angular resolution is proportional to wavelength / aperture so imaging in near IR has around half the resolution of imaging in blue light, though as you say the effects of seeing is less, the longer the wavelength, so in normal seeing conditions the loss in resolution may not be too apparent.

It's likely the longer exposures are causing the softness as you're probably using 18mS at 55 fps. It's worth using very high gain settings to try and get the exposure to 5mS or less. It will look terribly noisy on the video but stacking several thousand frames will very effectively remove the noise. Also lower read noise at higher gain. There is no target rotation limit on video length with the Moon, so you can take 10 min or more videos and stack just the best 5 or 10%.

I assume you're recording in 8 bit and have the high speed setting enabled in the camera setup, (if it has that option). This reduces the A/D conversion depth to perhaps 9 or ten bits which will give a better fps, if you're not limited by exposure length.

Alan