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Jupiter 16th August 4" Refractor.

neil phillips

By neil phillips
in Imaging - Planetary

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neil phillips

neil phillips

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Didnt really buy this for planets. Being Achro, and very small. I prefer a higher level of resolution. really got it for low power wide feild shots of the moon. But was out last night doing star testing. Saw Saturn had a look. and thought why not. Amazing how much detail a little scope can pull out on jupiter. 

Altair Starwave F11 Achromatic doublet. QHY462C Camera. SW EQ5 Mount. QHY UV IR Cut Filter. 

Both resampled. Not because it improves the data. But because i find it easier to see the details 

 

150 starwave 16th August 21.50 UT.png ir smooth.png 130 smooth.150 decon.png

 

 

 

colour.tif s.png

 Slightly later capture 22:04 UT

last de rot.tif 200.tif look.tif 75.png sg.png

Edited by neil phillips
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vlaiv

vlaiv

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Very nice, I find those images exact match -visually- to my F/10 4" achromat when seeing is good.

I wondered why there is such distinct pinkish/red cast that other scopes don't give and answer is surprisingly simple. It is due to chromatic aberration - although it is not seen as fringing in above image (it is there visually - but just a hint of purple halo in my scope). I managed to reproduce it easily - just take any "regular" Jupiter image and then leave green channel alone, do mean blur on red channel (maybe 2px) and just a tad larger mean blur on blue channel (maybe 3px) and resulting image will look like thru achromatic refractor. This simulates defocus in blue and red parts of spectrum - and is really interesting.

Edited by vlaiv
Forgor to say visually
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neil phillips

neil phillips

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5 minutes ago, vlaiv said:

Very nice, I find those images exact match -visually- to my F/10 4" achromat when seeing is good.

I wondered why there is such distinct pinkish/red cast that other scopes don't give and answer is surprisingly simple. It is due to chromatic aberration - although it is not seen as fringing in above image (it is there visually - but just a hint of purple halo in my scope). I managed to reproduce it easily - just take any "regular" Jupiter image and then leave green channel alone, do mean blur on red channel (maybe 2px) and just a tad larger mean blur on blue channel (maybe 3px) and resulting image will look like thru achromatic refractor. This simulates defocus in blue and red parts of spectrum - and is really interesting.

Couldnt agree more Vlaiv. its the one thing that puts me off about achromatic doublets. Colour work on planets. The out of focus blue light also can smear fine detail. The F11 Starwave has reasonable colour correction for a achro. But not enough by a long shot for faithfull colour work. But then i have my big Newtonian for that. Although at some point i may get a smaller instrument with faithfull colour. Either a mak. or long focus 6" newt. 

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Trevor N

Trevor N

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Plenty of detail there as usual Neil. I agree, its amazing what a smaller scope can do which must be encouraging to the vast majority of amateurs. I think we all agree this game is very much a law of diminishing returns. You don't necessarily need a huge scope to get some really good images these days. You can spend a fortune in upgrades and not really achieve much more. I was out as well last night but not processed anything as yet. Seeing was all over the place at times but we will see if I can gain anything from the good bits !! It always takes me far longer to process than to take images. It must be age !!!

 

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neil phillips

neil phillips

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5 minutes ago, Trevor N said:

Plenty of detail there as usual Neil. I agree, its amazing what a smaller scope can do which must be encouraging to the vast majority of amateurs. I think we all agree this game is very much a law of diminishing returns. You don't necessarily need a huge scope to get some really good images these days. You can spend a fortune in upgrades and not really achieve much more. I was out as well last night but not processed anything as yet. Seeing was all over the place at times but we will see if I can gain anything from the good bits !! It always takes me far longer to process than to take images. It must be age !!!

 

Hi Trevor. Seeing was better here early on. At some point cool air came over and caused havoc. i felt the cold. And saw the cloud. in another part of the sky. Then the seeing dived on screen when the cool air hit. 

Will look out for any posts from you

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neil phillips

neil phillips

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2 hours ago, CraigT82 said:

Wow Neil those are impressive. I had one of those f/11 across a couple of years ago and loved it, views were pin sharp but just a bit dim compared to my Fullerscope (not really a fair comparison being 8.75")

yes even a 14 degree moon couldnt stop sharp views. I wonder if these doublets have better quality glass, not just figure.  Star test looks pretty good not identical either side. Very very rare full stop. Let alone with a achro. But a good star test. 

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neil phillips

neil phillips

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1 hour ago, chiltonstar said:

Nice images Neil, but of course with planets, aperture does count. Unfortunately, we can't beat the laws of physics. I always look in envy at C14 images compared with the 'umble offerings from my 7" of aperture...

Chris

For sure Chris. i think there is a certain threshold were things start to get interesting. Around the 9" mark a little less, a little more. Depending on the situation.  But thats what i see. C14s can be very seeing dependent. thermally dependent too. 

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si@nite

si@nite

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A good result Neil, achros do seem to present that almost magenta look to the captures due to chromatic aberration, but like you say widefield lunar work will be unaffected especially using monochrome cams, a baader semi apo filter reduces CA on achros with good results ive found with mine!

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neil phillips

neil phillips

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1 hour ago, si@nite said:

A good result Neil, achros do seem to present that almost magenta look to the captures due to chromatic aberration, but like you say widefield lunar work will be unaffected especially using monochrome cams, a baader semi apo filter reduces CA on achros with good results ive found with mine!

Hi Simon yes agreed Colour work is not its forte. I use a Baarder 495 longpass. I didnt with this because i wanted to see the false colour as i was testing it. I got it for the moon primarily,  as you say colour not a problem with my zwo 178 mono camera

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