Science Interviews


Mon, 18th Jul 2016

Photographing the gas giants

Roger Hutchinson, Astrophographer

Listen Now    Download as mp3 from the show Jupiter: King of the Planets

Roger Hutchinson takes Graihagh Jackson through how he photographs the night skyRoger Hutchinson in his observatory...

Roger - Well, when I was a kid -  I grew up in the 70ís and that was right at the tail end of the Apollo programme. So the moon landings and everything, as a young boy, really inspired me and an interest in space developed. And then as I got a little bit older, probably with the encouragement of my dad, I built a telescope and I can still remember the first time I saw Saturn through telescope and that kind of hooked me. I did a lot of astronomy as a kid growing up and then went away to University, kind of dropped out for a bit - just got on with life, and then probably about 5 or 6 years ago I got back into the hobby. Iíve been obsessively photographing the skies ever since really.

Graihagh - You mentioned Saturn. You said youíll always remember the first time you saw Saturn. I wonder whether you could describe that moment a bit more for me?

Roger - Well, when you see it with your own eyes for the first time, it kind of blows you away. People think it's something thatís been stuck onto the end of the telescope; they just think itís a little cardboard cutout or something because it just doesnít look real you know - itís mind-blowing really!

Graihagh - OK. I will add that to my checklist of things to do in life: catch a fish and eat it, see Saturn in the real flesh. I think thatís the next one to do.

So tell me about Jupiter then? Have you photographed Jupiter much and I want to know is it disappointing to see?

Roger - No, I would say Jupiter is not disappointing! I have done a lot of photography of Jupiter. For planetary photography itís probably the easiest target because itís not called the king of the planets for nothing. Itís big and itís an interesting sort of target as well because it rotates so quickly, the cloud patterns change. Itís quite a dynamic target so itís a good one to cut your teeth on.

Graihagh - I came all the way to your beautiful house in the hope that we might be able to photograph Jupiter, and classically itís cloud in the U.K. What more would you expect?

Roger - In astronomy in Britain youíve just got to develop a lot of patience and just realise that thereíll be another opportunity some other time and just make the most of what nature deals you,  but this summer has been particularly bad.

Graihagh - You say itís a write off, but Iím looking into your back garden as we sit in the conservatory now and I think the whole trip down from Cambridge has been worth it just to seeÖ I mean I donít even know how to describe it, itís like a mini observatory in some ways - itís quite impressive!

Roger - Well I guess itís what people would picture if they were talking about an observatory; itís got a dome. So like anything with aÖ

Graighah - Seriously - I think youíre underselling it here! Itís a good two metres high, white and almost like a hidey house at the back of the garden.

Roger - Itís been described as a minion, a rubbish bin, a portable toiletÖ all sorts of things. Thereís been a lot of comments about it

Graighah - Can you give me a tour?

Roger - AbsolutelyÖ So itís all plugged in in the hope that weíd see something butÖ Just watch yourself here as I have bashed my head on numerous times.

Graihagh - Itís a really impressive setup.

Roger - Itís currently pointing at Jupiter at the minute but you wouldnít know it

Graihagh - Does that mean youíre sitting out here for hours on end or do you just hit click and then go to bed?

Roger - Well for planetary, youíre actually shooting video, so you donít take individual images; you take a sequence of individual images. Basically what we call it is Ďlucky imagingí because the sky and the atmosphere is very turbulent and the more you magnify it the more turbulent it becomes so, basically, itís what we call Ďseeingí.  Seeing is basically with front distortions in the atmosphere, so itís just like if youíre looking at something under high magnification - it wobbles. What you want to do to counteract that is shoot something when itís really high in the sky so youíre looking through less atmosphere, or you can use different wavelengths of light that are less affected by seeing. Or you could wait to get a really good night because that is the best thing to let nature sort it out for you.

So there are lots of websites that have jetstream predictions. So what you want is the wind speed of the jetstream to be low over the U.K., over where youíre imaging. And then in general, it doesnít always hold true but, in general, if youíve got light winds at ground level, light winds in the jetstream, then seeing is normally reasonably good.

So the best thing is to take in when everything works well for you. But we can help that along by using a non-visible wavelengths pass filter and what that does is if you think about the electromagnetic spectrum and youíve got like red through toÖ

Graihagh - Like the rainbowÖ

Roger - Like the rainbow, basically. So red is a longer wavelength than green, which is a longer wavelength than blue. So what I do is image through a mono camera, so this is a black and white camera, and you image through a series of different filters. What we use is an infrared pass filter which filters out any wavelength shorter than 685 nanometers, so itís quite long wavelengths, and that is less affected by seeing - the shorter wavelengths are more affected by seeing.

So what you typically see when youíre taking your images, you take a series of images; one through an infrared filter, which is not necessary if you want a colour image, you can just use a red and then a green, and a blue filter. But what you generally see is that the red filter image is less affected than the blue filter image by atmospheric seeing because red light has a longer wavelength than blue light so it kind of demonstrates the theory quite well.

Graihagh - You must have to brush up on your physics quite a lot here t work out how well to photograph these things?

Roger - You donít necessarily need to know the physics; youíre just shooting through different filters but itís quite nice to know why your red image is much better than your blue image. But what we then tend to do is weíll combine the red, green, and blue images together to give you a colouridge and then weíll use the infrared image as whatís termed a luminance layer, which is where all your detail is.  So that sits on top and gives you all the detail, and all the colour comes from the red, green and blue images that youíve taken through the relevant filters.

Oh, that was the dome movingÖ

Graihagh - It moves automatically?

Roger - Yes, itís tracking the sky as well as the telescope. So what that does mean to answer your earlier question, you can, if youíre taking long exposure photographs of deep sky objects, you can set it going and go off and have a cup of tea in the warm.

Graihagh - And the roof will continue to move round?

Roger - And the roof will move around for you, yes. It does give you a little bit of shock sometimes if youíre not expecting it or if youíre leaning against it!

Graihagh - Rooky error!

Roger - Iíd forgotten it was on actually. Iíll turn it off because weíre not actually looking at anything at the minute.

Graihagh - Back inside, Roger took me through the complicated imaging process he does to make these beautiful pictures. He really does make it look easy but actually, thereís at least a good 45 minutes of tinkering around.

Roger - You take a lot of images over time and some are better than others and a lot of it, as Iíve said, is down to conditions that are basically beyond your control. Sometimes you just get a perfect night where everything just works well, works in your favour, all the equipment works well, and you get a really nice image at the end of it. Itís about being patient, and plugging away, and not being too disheartened. It just that nice surprise when you get a really good result.

Graihagh - What image are you most proud of?

Roger - The oneís Iím proudest of are probably some of the deep sky images because they do take a lot of time and dedication. But the ones I like the most and enjoyed taking the most are probably the transitory ones. The lunar eclipse that we had last September - it was just great for the weather to play ball because these things happen quite rarely, and so to be able to actually get them and image them is exciting and really pleasurable.

Graihagh - I can seeÖ I can see you take great joy - watching your process and talking about it - I can see it gives you great pleasure.

Roger - Mmm. Absolutely! I can recommend it to anyone. You donít need to go mad and have your own observatory in the back yard to do it either. You can create really nice results with minimal gear.



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