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Focusing on Jupiter?

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#1 Aaron_tragle

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Posted 23 May 2018 - 04:47 PM

Any methods to make it easier to focus on a planet? I am planning on shooting jupiter tonight.



#2 Gary Z

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Posted 23 May 2018 - 04:53 PM

Instead of focusing on the planet, first focus on the moons....once you have the moon focuses as pin-points, you are in focus.  Note, that this is after you have your camera setup and in the scope and you are adjusting your focus on the moon.  Once you have pinpoints for the moons, you are in focus. 

 

Happy Shooting!!!

 

Gary


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#3 gazerjim

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Posted 23 May 2018 - 05:03 PM

Just a suggestion that optimum focus takes a little patience.   Get comfortable with watching the image change in real time on your screen.   Be sure you have gone past the point of best focus and back at least once.  Best focus should be obvious when seeing is good.  It's an exercise is frustration on those nights when none of the frames are really sharp.

 

Good luck !


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#4 moonwatching ferret

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Posted 23 May 2018 - 05:56 PM

can try lowering  gama to as welljust turn it off before imaging i usualy make 3 to 4 passes in and ouyt befor im happy, a motor focus is crutial


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#5 BQ Octantis

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Posted 08 June 2018 - 06:41 PM

Hey, mate,

 

Use a Bahtinov mask on a nearby star through the setup you're using to capture (you'll have to crank the gain or exposure time). Then slew back and capture. Everything else is just eyeballing it.

 

Cheers,

BQ


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#6 RedLionNJ

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Posted 08 June 2018 - 07:46 PM

I'm with Jim, Joe and (to some extent) Gary.

 

You need to be looking at the planet itself to take advantage of the moments of best seeing - those are the moments during which you need to fine-tune the focus. Lowered gamma helps, for sure. Any close-in satellite can be of help, but what you're really looking for is maximum density of detail on the cloudtops. When you think you have a reasonable focus, roll through focus a few times, in and out (using a hands-off, Crayford-style focuser). If you can't see a point of focus any better than you already had, you're either extremely lucky or the moment of better seeing has passed.

 

Experience is the key, here. And patience.



#7 Tom Glenn

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Posted 08 June 2018 - 10:55 PM

If you roll through focus several times, there should be an obvious point where the image is sharper and in focus, even if you have trouble stopping on this exact spot.  If you can't detect any point in which focus was obviously sharper, then the seeing isn't really good enough to be imaging.  But if you can detect a point that is sharper, it's just a matter of going back and forth as many times as it takes until you land on it.  It can be tedious if seeing is mediocre, but you will get better.  


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#8 Kokatha man

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Posted 09 June 2018 - 03:53 AM

...ditch the Bahtinov mask idea - you can always tell when someone is using these things to focus on a planet...hang on, that's incorrect- it looks just like poor collimation...or poor seeing...or poor focus.wink.gif (which is what it is! lol.gif )

 

Focus is a dynamic factor that is nearly always changing as the planets rise higher in the sky, quite considerably altering as time goes on during any single imaging session so that even if these masks did give you a good focus (which they do not!!!) they would be incredibly clumsy methods to say the least with constantly putting it on & off & going back & forth to some (hopefully!) nearby star!

 

Learning to focus accurately is a bit of an art & of course in poor seeing is very difficult at times...& really not worth imaging in such circumstance anyway...

 

With Jove it is the boundaries of the NEB & SEB that will give indications of near-focus...these will become somewhat convoluted & reveal little curves, twists & curls to said boundaries/edges...at the same time revealing lighter & darker patches within the belts themselves.

 

Festoons might start to appear in the bright EZ...like fine threads - these might also exhibit little "blotches" at their ends also, but often it is when you can just actually see a thread-like festoon at all that best focus is attained...meaning as you very carefully adjust your after-market focuser (an absolute essential btw) there will be a point where a festoon thread might suddenly appear - that is best focus...but of course if the seeing (& your collimation & the scope's thermal equilibrium) allows it you might suddnely see more than one festoon...or that festoon might reveal more traceries/threads emanating from it...or you can very carefully adjust focus until that festoon becomes a very sharp & well-defined thread...or a little "blotch" on the end becomes more defined...that's when you know your focus is razor-sharp & the seeing is great! smile.gif

 

Every planet has different indicators but those are some of the best for Jove...as are the little white circles or storm spot....

 

Practise - practise - practise...you will find it gets easier - & make sure you don't use a #&**^%! mask of any type....! rofl2.gif


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#9 ntph

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Posted 09 June 2018 - 08:49 AM

Sounds like a dust-up down under! K-man vs BQ in the ring. As an aspiring neophyte just getting into more serious imaging, I admire the quality of the images they each post and the advice they give so freely. Now to read they can have such divergent opinions and practices yet still create such great images confirms the advice each gives, in my mind: practice, practice and wait for the seeing to cooperate. Have at it, boys!

#10 ToxMan

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Posted 09 June 2018 - 01:06 PM

My observation lurking around here for last 10 years...deep sky imagers using one shot color cameras for planetary imaging will grab the b-mask to focus...it's what they know. But, if you practice without one, you won't grow dependent on one. But, you take a planetary imager, who's never done deep sky work, they think someone cut slots in a frisbee. And would toss it, see if it flies.lol.gif


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#11 gazerjim

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Posted 10 June 2018 - 12:42 AM


Focus is a dynamic factor that is nearly always changing as the planets rise higher in the sky, quite considerably altering as time goes on during any single imaging session so that even if these masks did give you a good focus (which they do not!!!) they would be incredibly clumsy methods to say the least with constantly putting it on & off & going back & forth to some (hopefully!) nearby star!

 

Learning to focus accurately is a bit of an art & of course in poor seeing is very difficult at times...& really not worth imaging in such circumstance anyway...

 

Had never quite thought of focusing as a dynamic process. But it really is.  There is no set-and-forget point of focus for high res work.  The atmosphere and your scope are constantly changing. Think of it as like tuning a stringed wooden  instrument during a long session.   It's ongoing.  A fraction of a millimeter can make the difference between a great image and one that is merely  "good".



#12 BQ Octantis

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Posted 10 June 2018 - 02:35 AM

Aaron,

 

Here's the mask I use on my 7" Cass-Mak—it's adjustable, and it also fits a friend's 8" Celestron SCT:

 

https://agenaastro.c...aphy-fp403.html

 

Here's what a focused star looks like through the Bahtinov on the sensor (Antares, 2 second exposure, ISO 12800, Auto WB):

 

IMG_4154.jpg

 

If the center line wanders a lot, just do a longer exposure (10-15 seconds) to find the average. This should suffice for a 10-20 minute imaging window. Here's the corresponding shot of Jupiter through the jet stream at 48 m/s and a seeing index of 2/5:

 

20180508_Jupiter.jpg

 

Going through my old focusing images, I found that I could have gotten a Bahtinov pattern on any of the moons, too, so you might consider using one of them as the reference.

 

How did your imaging go?

 

Cheers,

BQ



#13 Kokatha man

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Posted 10 June 2018 - 06:46 AM

Had never quite thought of focusing as a dynamic process. But it really is.  There is no set-and-forget point of focus for high res work.  The atmosphere and your scope are constantly changing. Think of it as like tuning a stringed wooden  instrument during a long session.   It's ongoing.  A fraction of a millimeter can make the difference between a great image and one that is merely  "good".

 

Jim, my partner & I have been carrying out hi-res imaging for years & work regularly with professionals supplying images, as just about any regular visitor to this forum would know...alternatively, their quality can be easily assessed simply by looking at our website...focusing is indeed very dynamic & the use of a digital readout focus control is the best way to appreciate this fact. (a vital element in our equipment btw)

 

As an example here is an image on our site that specifically addresses this dynamic focus situation: http://momilika.net/...-35_rgb_dpm.png

 

BQ - if you believe that Bahtinov masks provide accurate focus, your cause would be much better served by posting an image without any excuses about jet streams nor seeing conditions; with all due respect that image endorses nothing re your focusing approach - a sharp, focused image (taking into account your aperture of course!) would have relevance.

 

In fact my original comments about poor focus, collimation or seeing (&/or for all 3) would be quite apt for your example...that's not meant to trash it whatsoever btw - it simply doesn't make any point about accurate focusing.

 

This isn't any "dust up" or other argument, there's nothing whatsoever personal in this flowerred.gif ...the only reason I have been so forceful in my criticism about BMask's is the same for when I hear nonsense about "rotational blurring" & other similar misinformation: it does neither the beginner nor those who wish to improve their planetary imaging outcomes any real favours or assistance - no serious "hi-res" imager who I am aware of uses masks to focus...& for very good reasons. lol.gif

 

Here's another image on our website http://momilika.net/...&3-Channels.png ...certainly not one of our best Joves by any means...but in line with the first link I've given in this post, as well as to provide something very broadly "analogous" to BQ's image in that the seeing was not very good (nothing to do with focus, collimation or thermal equilibrium however! lol.gif ) & this is verified by the blue channel's appearance (lower right)...but there is still no way the detail shown could have been evinced using a mask for focusing lol.gif - I also linked to this one because I think it gives a reasonable range of the raft of indicators I articulated in my first post in this thread...festoons & tracery, blotches, white spots, edge corrugations to the NEB & SEB etc, etc...

 

Of course if you want some really sharply-focused images look at some of these in the 2016 Mars apparition section: scroll down to the bottom half of the page for those ones earlier in that apparition... http://momilika.net/...ars2016Pics.htm

 

That's all I'll say here & if people don't want to listen that is their own business...I spend a lot of time giving fellow CN'ers valid & verifiable information & specifically try to assist newcomers with our planetary imaging knowledge & experience built up over years of work where we have often been at the forefront of new camera technology useage.

 

Tutorials like this http://momilika.net/...3Processing.htm - which are a lot of hard work to create are freely provided & also intended to counter misconceptions about a raft of factors & practices including aspects such as seeing & collimation, processing per se etc, etc. (read the intro there)

 

Oh...& did I also mention "focusing..?!?" rofl2.gif


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#14 ToxMan

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Posted 11 June 2018 - 09:30 AM

So, how did focusing go, Aaron? We all might have assumed you were focusing using an electronic motorized focuser...foregoing the b-mask, one of these with some sort of read out to monitor your best focal point is the best method, if you are still "hands on" focusing. And, practice. As I have pointed out in the past, for monochrome camera users, b-masks are totally impractical. Hi res imaging has pretty much demonstrated to me that there really are no parfocal filters, and I check focus/re-focus with each filter change. 



#15 azure1961p

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Posted 12 June 2018 - 09:37 AM

I focus on the moons, period. Never jupiter.

 

Pete


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#16 RedLionNJ

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Posted 12 June 2018 - 12:17 PM

Another potential reason for Jupiter (or its moons) vs a nearby star - if you're using something like FireCapture's cut-out functionality, you're pretty much tuned-into the immediate vicinity of the planet and your mount is gliding smoothly along with a fairly small ROI around Jupiter.  If you're going to use a (nearby, even) star, you're still going to kill the cut-out and aim somewhere else for a few seconds. Then once focused, back to Jupiter again.

 

So while changing filters, or adapting to OTA thermal contraction, you could spend a lot of time disabling cut-out, moving away, focusing, moving back, re-enabling cut-out, etc.

 

As opposed to just focusing.



#17 kevinbreen

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Posted 13 June 2018 - 03:10 AM

I have a BM but never used it, never had a decent star to focus on tbh!
The Jovian moons are great, but they can be problematic if the seeing is flakey. If I do use the moons to get into good focus, I still try to then just focus on the planet. Try to get the edge of the planet as sharp as possible, then concentrate on some features, even if they’re vague and fleeting. If that fails, then the seeing isn’t great, try tomorrow

#18 sfugardi

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Posted 13 June 2018 - 05:15 AM

Aaron, for the bright planets like Jupiter, use the auto-align option in FireCapture which locks the planet in place between the 4 red dots, so you can more easily focus on the details. I even capture with it on and constantly check and tweak the focus

 

Regards,

Steve



#19 Gary Z

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Posted 13 June 2018 - 10:40 AM

Hey Aaron, hope we didn't scare you off....lol.  But we are very interested to know how your session went.

 

Take care and hope you enjoy many good nights of imaging this summer!

 

Gary



#20 BQ Octantis

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Posted 17 June 2018 - 08:00 AM

Wow…I had no idea that the Bahtinov was the boogeyman of planetary imagers! I can only imagine the amount of coffee to be coughed up and spattered on screens around the planet at the following.

 

If you're imaging through your XT8 via Live View capture with your D5100 DSLR, focusing is quite parfocal across RGB—that's the whole point of a reflector (and even the glass on my 5" SCT imparts no detectable chromatic dispersion on my Canon T3i). If you focus with the Bahtinov, you also don't have to wait for a momentary good seeing moment to sharpen. Indeed, living under the jet stream over central Australia, I never would have imaged Jupiter at opposition this year had I waited for good seeing! As per my post above, just do a longer focusing exposure to find the optimum focus for your seeing. That way you're imaging vice fiddling when those lucky seeing moments appear.

 

If you're using a lot of glass (like your refractors or DSLR lenses) and a/or monochrome camera with filters, then you're most certainly better off eyeballing it. For eyeballing, I use the method of multiple rolls through optimum focus that several have described above, but with a twist: I count steps from the first point of perceptible defocus through optimum focus and on to the opposite point of perceptible defocus. Peak focus is the number of steps between the two defocus points divided by two. With a practiced hand, you can even do it manually with your DSLR lenses (though the first point of detectable magenta chromatic aberration around a bright star is equally effective). Here are single frames of Jupiter and Saturn through a 70-300@300mm image-stabilized lens, hand-held, sharpened with that method last weekend:

 

IMG_4526.jpg

Jupiter, belts and polar zones visible, 2018-06-11 09:23 UTC

ISO800, 1/500s, f/5.6

Canon 70-300IS@300

Canon T3i, eyeball focus

5X rescale (no interpolation)

Tennant Creek, NT, Australia

 

IMG_4531.jpg

Jupiter, moons visible, 2018-06-11 09:26 UTC

ISO12800, 1/80s, f/5.6

Canon 70-300IS@300

Canon T3i, eyeball focus, 1x crop

Tennant Creek, NT, Australia

 

IMG_4538.jpg

Saturn, disk and rings apparent, 2018-06-11 12:01 UTC

ISO800, 1/160s, f/5.6

Canon 70-300IS@300

Canon T3i, eyeball focus

5x zoom (no interpolation)

Tennant Creek, NT, Australia

 

There are many means to the same end, but your preferred workflow will materialize with experience. Keep at it, mate!

 

Cheers,
BQ



#21 Foehammer

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Posted 17 June 2018 - 04:36 PM

If using Firecapture, the "Autoalign" feature will center the target in your live feed and this will greatly assist you whilst adjusting your focuser, stock or aftermarket, until you have achieved the sharpest possible appearance of said target. You will need to check and readjust focus several times over the course of your imaging run, as others have noted.

#22 CrazyPanda

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Posted 17 June 2018 - 08:30 PM

Wow…I had no idea that the Bahtinov was the boogeyman of planetary imagers! I can only imagine the amount of coffee to be coughed up and spattered on screens around the planet at the following.

 

I guess it depends on seeing conditions. 

 

For seeing in my area, I *must* use a b-mask, else it's just guess work.

 

When I use Jupiter directly, I have two options:

 

1. Use a long exposure to reduce the gain enough that the noise doesn't blur the fine details. But this means seeing blurs the fine details, so I lose.

2. Use a short exposure to catch milisecond moments of steady air, but then use higher gain and thus introduce detail-destroying noise. so I also lose.

 

In situations like this, a b-mask is the only thing that gives me good enough focus to ensure bad focus is not compounding the poor seeing. 

 

Some will say not to bother imaging during those nights, and indeed I don't both when the jet stream is above 30m/s, but it's either that or not do any imaging at all. So if those are what your skies are like, you need a b-mask. Period. It's the only reliable way to ensure focus.

 

If you're lucky enough to have steady skies and a lazy jet stream, then the planet surface itself will be sufficient.



#23 BQ Octantis

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Posted 18 June 2018 - 05:57 AM

Some will say not to bother imaging during those nights, and indeed I don't both when the jet stream is above 30m/s, but it's either that or not do any imaging at all. So if those are what your skies are like, you need a b-mask. Period. It's the only reliable way to ensure focus.

<snort>30 m/s! Now there's coffee on my screen! The jet stream at 48 m/s was the slowest and my best seeing the whole month of opposition. Its worst was at 72 m/s—that's 140 knots, mind you (for reference, the top speed of a Cessna 172 is 130 knots!)–and the ground wind was at 15 knots in the opposite direction. But the Bahtinov on Antares still served its purpose, and I captured enough detail to see how the atmosphere was progressing through the month:

 

IMG_4252.jpg

 

Frames2-3_500_cleaned.jpg

 

I pine for 30 m/s for Saturn and Mars opposition, but I'm at 38 heading back into the mid 50's…

 

BQ



#24 CrazyPanda

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Posted 18 June 2018 - 08:02 AM

<snort>30 m/s! Now there's coffee on my screen! The jet stream at 48 m/s was the slowest and my best seeing the whole month of opposition. Its worst was at 72 m/s—that's 140 knots, mind you (for reference, the top speed of a Cessna 172 is 130 knots!)–and the ground wind was at 15 knots in the opposite direction. But the Bahtinov on Antares still served its purpose, and I captured enough detail to see how the atmosphere was progressing through the month:

 

attachicon.gif IMG_4252.jpg

 

attachicon.gif Frames2-3_500_cleaned.jpg

 

I pine for 30 m/s for Saturn and Mars opposition, but I'm at 38 heading back into the mid 50's…

 

BQ

Ouch :(

 

Yeah typically the jet stream stays about 45-48m/s for me. 30 is what I would consider good and above average for this area. It dips down to 7... when there is 100% cloud cover :p



#25 WarmWeatherGuy

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Posted 18 June 2018 - 01:50 PM

It is easy to say don't use a Bahtinov mask when you can focus in both directions. I don't have a Moonlite focuser on my SCT so I can only focus in one direction.




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