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Astrophotography and Sketching >> Solar System Imaging & Processing

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Kokatha man
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Reged: 09/13/09

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Jupiter.....the "soft" approach! new
      #5553430 - 12/04/12 07:04 AM Attachment (44 downloads)

Ok-ok! Probably done this particular rgb set to death as far as some folks might think* but I decided to try the full 3X drizzle in AS!2 and I think with good data you achieve a very nice "soft-processed" Jupiter using large resampling!

So here's the 120% & 100% image scale of that image with said processing.....I think it's pretty nice although obviously not quite the sharpness of the others - personal "druthers" to many I suppose but I'm happy to create either versions...

Also (for Emil and others!) that ASI120MM adapter I had a mate make to tame the image scale of this small-pixelled camera with the C14.

* ...and I haven't finished - there's the WinJupos version still in the pipeline..!!!

First the 120% of cap scale image...


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Kokatha man
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Re: Jupiter.....the "soft" approach! new [Re: Kokatha man]
      #5553432 - 12/04/12 07:05 AM Attachment (31 downloads)

@ capture scale...

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Kokatha man
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Re: Jupiter.....the "soft" approach! new [Re: Kokatha man]
      #5553440 - 12/04/12 07:13 AM Attachment (27 downloads)

.....and the aluminium (or "aluminum" ) adaptor that has professionally-applied "state-of-the-art" anti-reflection felt-tip pen scribble on the inside...

Part #1 is the TeleVue 2X barlow lens element which gives about 1.25X at the short distance it is from the cmos sensor.

#2 is the adaptor itself with an M40 ("C" type) thread around its' periphery...

Lastly, there's the bit of masking tape to cover the hole in the plastic cap....!


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Space99
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Reged: 08/14/08

Re: Jupiter.....the "soft" approach! new [Re: Kokatha man]
      #5553491 - 12/04/12 07:56 AM

looks interesting
if it's give (only)1.25x wouldn't be a extension tube work on a sct optics for the same result? I forget the "true" F? for the given BFL of a C14 but perhaps a slider can be made to experiment for a small mods of the FL. It may alter the spherical correction of the system tho... so is the Barlow if it's not used with a designed distance me think.
Mick


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Kokatha man
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Re: Jupiter.....the "soft" approach! new [Re: Space99]
      #5553551 - 12/04/12 08:42 AM

Quote:

looks interesting
if it's give (only)1.25x wouldn't be a extension tube work on a sct optics for the same result? I forget the "true" F? for the given BFL of a C14 but perhaps a slider can be made to experiment for a small mods of the FL. It may alter the spherical correction of the system tho... so is the Barlow if it's not used with a designed distance me think.
Mick




Not sure I quite understand what you're saying Mick - an extension tube on the end of the scope itself as I understand your comment wouldn't achieve anything except make me have to throw the focal point back by bringing the primary closer to the secondary.....I understand about SA when shifting primary-secondary distance (as in extending the focus out from the barlow) but I've never thought about whether bringing the 2 mirrors closer actually effectively lengthens the native f/l..?

My inderstanding of optics most definitely isn't world-class but I suppose the secondary is actually a "barlow" of sorts...

***stopped typing at this point to do some research (thanks for that!) and "yes" changing their relative distance does change the effective f/l.....I seem to remember however that nearer together is worse in some respects for SA and other distortions.....and perhaps the barlow isn't creating as much distortion when the image plane is nearer as opposed to further out from it.....

At any rate in the end I'm a practical person and if I don't see any obvious effects (and I don't) then I'm happy to go the way I have...

But thanks for your comments Mick - food for thought...it'd be interesting to experiment as see what sort of scales can be achieved the way you suggest, and I'll probably do so when I find the time..!

ps: I use an i7 quad-core laptop in the field but I really don't know/think if that sort of "performer" is necessary for the ASI120MM.....but not having any specific knowledge/advice I refrained from responding to your thread question.


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Daniel Chang
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Reged: 07/05/06

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Re: Jupiter.....the "soft" approach! new [Re: Kokatha man]
      #5553632 - 12/04/12 09:38 AM

Wonderful image!

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RedLionNJ
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Reged: 12/29/09

Loc: Red Lion, NJ, USA
Re: Jupiter.....the "soft" approach! new [Re: Daniel Chang]
      #5553695 - 12/04/12 10:22 AM

Spectacular images, Kokatha-man!

Mick is right. Changing how far back the sensor is (even without any barlow-style contraptions) from the back of the SCT's rear cell most definitely changes the focal length. I've experimented quite a bit with my 12" and depending on what I have in there (filter wheel, Crayford focuser, etc.) I can vary my native focal length from around 270cm to 380cm. That's quite a range. I would 'assume' image correction is optimal at F10, but don't really have anything empirical to base that assumption on. The image-scale measurements were made with FireCapture, when Jupiter was aligned level with the horizontal axis.

Grant


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Space99
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Reged: 08/14/08

Re: Jupiter.....the "soft" approach! new [Re: RedLionNJ]
      #5554344 - 12/04/12 05:44 PM

hmmm.... did find the pdf re EFL vs BFL
http://tech.groups.yahoo.com/group/sct-user/files/SCT%20Ray%20Tracing/

download the vignetting analysis pdf... for the c14 any more than 200mm bfl and it start vignetting on axis, effectively reducing the sct diameter.... not good, my bad

Mick


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Kokatha man
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Re: Jupiter.....the "soft" approach! [Re: Space99]
      #5554524 - 12/04/12 07:44 PM

Thanks Daniel and Grant, your kind words are appreciated!

Sounds like I might've steered the better course Ed, I might fire off an email to TeleVue (as a purchaser of several of their barlows/powermates! ) and ask what their take is on abberation (if any) with sensors/viewing closer that their "stadard" distances as in my setup.....obviously they don't feel the need to give any warnings about SA etc with extensions up to 100mm with their charts for said useage.

On a slightly more thread-related issue I gave this response to someone over on the UK's SGL about these "softer" images when they said it looked "almost painted" - and I thought it good to express my own thoughts here on CN on various types of processings by quoting my reply there:

"yes, these sorts of processings do take on a "painterly" aspect PH-R: some folks prefer this and personally I'm ambivalent, but I like to leave a bit of grain/noise in these types especially.....not just to retain a bit of extra crispness in the detail but as a balance to that uber-smooth appearance.

Again, some try to smash any noise out of their images completely but I think you run the risk of a little too much artificiality with that mantra because nothing in the natural world has those appearances - there is allways a little "grit" in everything/everyone (perhaps that's the pro artist in me talking now! ) .....but in the end it gets down to personal "druthers" re final aesthetic interpretation/processing and we all have different expectations - the beauty of good data is that you can process it just about every which-way..!"


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