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Saturn and Jupiter

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#1 hendric

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Posted 11 October 2019 - 10:59 AM

Even though wind and seeing was going to be laughably bad ahead of the cold front entering Austin (and boy did it deliver) I went ahead and setup for Jupiter and Saturn, just for the practice since the night was clear. One lesson learned - always check the telescope clock! When I asked it to slew to Jupiter it went the wrong way and banged the finderscope against the arms (twice because I'm a moron) - luckily the gears don't appear to be damaged.

 

Jupiter was barely above the treeline deep in the muck, about 13*. Trying to focus on one of the moons, I could see a clear RGB split of the colors - the moon was a rainbow streak instead of a spot. I think a ZWO Atmospheric Dispersion Corrector may be coming for Christmas LOL. I got lucky and happened to catch the start of a GRS transit. The picture is as bad as I expected, but there is some legit waviness in the belts.

 

Saturn was much higher, but still only ~28 degrees up and pretty mucky. Clear Cassini division this time, and I could see more than last time - definite bright equator and a faint belt in the temperate area. I did try a 2x Barlow, but it was hard to focus and the stack looked worse than at 1x.

 

Next time when the sky is steadier I want to try collimating since it's been years since I did so on this scope, and it's been stored in an uninsulated attic and hauled up and down stairs several times.

 

Equipment: Meade LX-200 Classic 8" f/10, ZWO ASI290MC, stacked with AutoStakkert and wavelets with Registax.

Raw video and capture settings:
https://hendric.smug...piter/20191010/
https://hendric.smug...aturn/20191010/

Attached Thumbnails

  • 2019-10-11-0221_9-CapObj_Jupiter_5_lapl4_ap54.jpg
  • 2019-10-11-0226_6-CapObj_Saturn_1_lapl4_ap35.jpg

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#2 kevinbreen

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Posted 11 October 2019 - 01:20 PM

Hi

 

An ADC is essential for the planets at low elevations, maybe Santa can come earlier? Good collimation is essential, you should try it more often! I keep my scopes outside in a custom-built shed which is secure and well-ventilated. That means they're in thermal equilibrium with the surroundings or very close. You might want to consider keeping it outside, maybe under a cover? How do you focus, manually? A hands-off focuser is really worth it - you can focus without the target bouncing around your FOV.

But regardless, it looks like the seeing was pretty rotten for you. Keep trying - one night the seeing will be great and you'll get some great shots.


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#3 hendric

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Posted 11 October 2019 - 02:32 PM

Thanks for the tips, much appreciated.  I will definitely try to collimate before the next set. I'm keeping the telescope in the garage right now, so it's quicker to setup. It takes me quite a bit of time to get all the gear outside and setup, so next time I'll open the telescope case to let it air while I bring the rest of the gear outside and get it set up. 

 

Yes, focus is a manual operation right now.  I added a jar lid to the focus knob to get finer control, but it still jiggles the telescope like crazy. I have been eyeing some of the electronic focusers, but I want to get the rest of the setup tuned enough to make it worthwhile. 

 

I noticed my exposures seems short compared to others. I used 14ms/325 gain on Saturn and 4ms/325 on Jupiter and it looks like a common setting is 50ms/50 gain.  Should I be using longer exposures? I thought getting fast exposures would be better for seeing, but maybe not.



#4 kevinbreen

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Posted 11 October 2019 - 03:07 PM

If the seeing is good then you actually don’t need really short exposures. Yes, in one sense the more frames you can capture the better the chance of catching a lot of good frames, but if the seeing is rubbish the best you’ll get is thousands of rubbish frames.

Jar lid: put a cabletie around the focuser and nudge the protruding end, it worked for me before I got a motorised focuser. It translates a big movement into a small. Try it.

Your gain settings seem fine.
Not sure what you mean by that 50/50 ratio
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#5 Tulloch

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Posted 11 October 2019 - 04:46 PM

Thanks for the tips, much appreciated.  I will definitely try to collimate before the next set. I'm keeping the telescope in the garage right now, so it's quicker to setup. It takes me quite a bit of time to get all the gear outside and setup, so next time I'll open the telescope case to let it air while I bring the rest of the gear outside and get it set up. 

 

Yes, focus is a manual operation right now.  I added a jar lid to the focus knob to get finer control, but it still jiggles the telescope like crazy. I have been eyeing some of the electronic focusers, but I want to get the rest of the setup tuned enough to make it worthwhile. 

 

I noticed my exposures seems short compared to others. I used 14ms/325 gain on Saturn and 4ms/325 on Jupiter and it looks like a common setting is 50ms/50 gain.  Should I be using longer exposures? I thought getting fast exposures would be better for seeing, but maybe not.

FYI, I've starting using foam rubber pipe insulation around my focus knob, it certainly reduces the amount of shake while focusing. It's really cheap, and the 3/4" inner diameter with 1/2" wall thickness is almost the right size for my C9.25, I just added some Velcro hooks on the inside for a bit more grip!

https://www.clarkrub...-wall-x-13mm-id

 

I'm waiting for the new version of the Celestron SCT electronic focuser to come to Australia, but it is a bit on the pricey side.

https://www.celestro...-sct-and-edgehd

 

For my setup with a C9.25 f10 with 2X Barlow and ASI224MC, I get best results with gain=350, shutter speed 4ms for Jupiter, gain 375, shutter speed 10ms for Saturn. This gives me about 250fps on Jupiter, 100fps for Saturn. YMMV of course...

 

Andrew


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#6 Kokatha man

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Posted 11 October 2019 - 06:47 PM

FYI, I've starting using foam rubber pipe insulation around my focus knob, it certainly reduces the amount of shake while focusing. It's really cheap, and the 3/4" inner diameter with 1/2" wall thickness is almost the right size for my C9.25, I just added some Velcro hooks on the inside for a bit more grip!

https://www.clarkrub...-wall-x-13mm-id

 

I'm waiting for the new version of the Celestron SCT electronic focuser to come to Australia, but it is a bit on the pricey side.

https://www.celestro...-sct-and-edgehd

 

For my setup with a C9.25 f10 with 2X Barlow and ASI224MC, I get best results with gain=350, shutter speed 4ms for Jupiter, gain 375, shutter speed 10ms for Saturn. This gives me about 250fps on Jupiter, 100fps for Saturn. YMMV of course...

 

Andrew

Andrew, my personal advice is to forget about any focuser that operates by actuating the primary mirror focusing knob..! To use an old phrase, they're not worth 2 bob imho & I say that with no idea of the price they're asking..! yba&cmv* lol.gif

 

Hendric, not bad at all in the conditions (the conditions looked pretty shocking btw!) but make sure you do collimate on a star. (there's plenty around Saturn)

 

I have no idea what capture program you used but watch the histogram when setting the gain/exposure. (exposure determining fps in conjunction with the height of any ROI you select) & on this score I strongly recommend you switch to FireCapture! smile.gif )

 

30 seconds is far too short a capture time for both planets (& before you say something about being worried about "rotational blurring" - don't!!! rofl2.gif  - this hooey is propagated by people who know absolutely zilch about planetary imaging!**) - at the image scale you used you could go close to 10 minutes on Jupiter & much more on Saturn! wink.gif

 

As long as you can get a histogram of about 50% - 55% without resorting to anymore than (roughly) 80% or so gain this will suffice.

 

* (your bank account & commonsense might vary) lol.gif

 

** Hendric, always check that the advice anyone gives you is backed up by a commensurate amount of knowledge/experience on the relevant subject matter! (see my website in the links in my signature fyi)


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#7 kevinbreen

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Posted 11 October 2019 - 07:00 PM

Andrew, my personal advice is to forget about any focuser that operates by actuating the primary mirror focusing knob..! To use an old phrase, they're not worth 2 bob imho & I say that with no idea of the price they're asking..! yba&cmv* lol.gif

Hendric, not bad at all in the conditions (the conditions looked pretty shocking btw!) but make sure you do collimate on a star. (there's plenty around Saturn)

I have no idea what capture program you used but watch the histogram when setting the gain/exposure. (exposure determining fps in conjunction with the height of any ROI you select) & on this score I strongly recommend you switch to FireCapture! smile.gif )

30 seconds is far too short a capture time for both planets (& before you say something about being worried about "rotational blurring" - don't!!! rofl2.gif - this hooey is propagated by people who know absolutely zilch about planetary imaging!**) - at the image scale you used you could go close to 10 minutes on Jupiter & much more on Saturn! wink.gif

As long as you can get a histogram of about 50% - 55% without resorting to anymore than (roughly) 80% or so gain this will suffice.

* (your bank account & commonsense might vary) lol.gif

** Hendric, always check that the advice anyone gives you is backed up by a commensurate amount of knowledge/experience on the relevant subject matter! (see my website in the links in my signature fyi)


Darryl, surely the tried and generally followed 3 mins on Jupiter is universal as a rule of thumb and is independent on image scale. How can you justify 10 mins on Jupiter?
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#8 Kokatha man

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Posted 11 October 2019 - 07:22 PM

Darryl, surely the tried and generally followed 3 mins on Jupiter is universal as a rule of thumb and is independent on image scale. How can you justify 10 mins on Jupiter?

...mild-mannered rofl2.gif heretic KM returns just in time to see the devout KB sprouting "scripture" at the savage heathen..! 

 

Ok-ok...let's make that 7 or 8 minutes, although I did say "close to 10 minutes" my chaste one..! lol.gif

 

Think about it - it is never <"independant on (sic) image scale"> Kevin...image scale determines apparent rotational speed & thus capture duration: I vary our capture timespans for Jove from anywhere between 150" (usually around opposition & maximum apparent diameter) & 210 seconds around the time Jove is much smaller therein at the end of the imaging season. (about now for instance)

 

When Mars is down to around 5" in diameter I've regularly captured for a total of 10 or more minutes - remembering that Mars doesn't rotate anywhere near as fast as (say) Jove in comparison - & these days we tend to stick at 5 minute captures for Saturn regardless of the apparent diameter...because although we used to employ 6 minute "standards" for Saturn, nowadays you can collect almost 100,000 frames in total over 5 minutes - so what's the point in going any longer..?

 

But perhaps I should lift my game & strive for better detail in my image outcomes by bowing to Mother Rumour..?


Edited by Kokatha man, 11 October 2019 - 07:23 PM.

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#9 Tulloch

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Posted 11 October 2019 - 07:24 PM

Andrew, my personal advice is to forget about any focuser that operates by actuating the primary mirror focusing knob..! To use an old phrase, they're not worth 2 bob imho & I say that with no idea of the price they're asking..! yba&cmv* lol.gif

 

* (your bank account & commonsense might vary) lol.gif

)

Thanks Darryl, the Celestron costs A$400, and looks tempting on paper thinking1.gif .

https://www.bintel.c...?v=6cc98ba2045f

 

The Crayfords are manual and quite long, which would be problem for me as the planets are so high shakecane.gif .

 

The Moonlight electronic focusers are too darn expensive ...


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#10 Kokatha man

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Posted 11 October 2019 - 07:36 PM

Shifting the primary of an SCT is poor practise imho Andrew...on IIS I see Moonlites reasonably frequently offered for fair prices secondhand...last year I purchased one which was of course the full hi-res unit with latest dual-control DRO (digital readout) box & all cabling (plus adapters) & basically brand spanking new for $500. It is a back-up for my original one which still runs perfectly - Ron Newman sent me gratis a set of control buttons for that a few years back should the DRO box ever need them from my constantly punching the heck out of them! ;)

 

I also put the oldest focuser on another scope & bought a new one for the C14 2 or 3 years back, so I have 3 hi-res stepper focusers & 2 DRO boxes..! :lol:

 

Even more frequently one sees hi-res Moonlite stepper focusers with the hand-held controller for significantly less, around $400 or so ...& for users who use colour cameras exclusively I think they represent good value, as does a Crayford-type with one of those SW stepper motors & hand-controllers which are about $120 by themselves...


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#11 hendric

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Posted 11 October 2019 - 10:51 PM

@kevinbreen
cabletie - will give that a try. Tie it around the knob with a cabletie, and leave the end sticking out the side like a propellor blade, right?

50ms/50gain, compared with the 4 or 14 ms/325 gain in my shots.

 

@tulloch
pipe insulation - Ha, that's a great innovation. I'll give that a shot too.
Glad to read your settings are similar to mine!  Next time I'm out I'll do some sets with ~14ms, and some with ~50ms, see which looks better.

 

@Kokatha_man
Well, ideally a separate motorized focuser would be perfect since it wouldn't give any mirror shift, but needs must until the money arrives. laugh.gif

 

I used ASICAP for the capture since it was simple enough to figure out in the time I had to mess around. I do have Firecapture and want to try getting familiar with that. One step at a time LOL.

 

I took 4 30s shots and one 180s one each before I gave up due to the winds. I wasn't too worried about planetary rotation. I had read that 180s was the limit for Alt-Az on the planets due to field rotation - I do have a wedge but it's one more annoying step in a long process (at least now, maybe when I get it to second nature I'll go back to Eq). I could tell between the start and finish (About 15 minutes) that Saturn's rings had rotated.

 

I was targeting a histogram closer to 240 out of 255. Should I aim for 128 out of 255? What do you mean by a gain of 80%?  Is that 80% of the max (600 I think on the ASI290MC in ASICAP)?

 

And yes, will definitely try collimating next time - hopefully with the skies (And telescope!) not vibrating so much.


Edited by hendric, 11 October 2019 - 10:52 PM.


#12 kevinbreen

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Posted 12 October 2019 - 04:17 AM

...mild-mannered rofl2.gif heretic KM returns just in time to see the devout KB sprouting "scripture" at the savage heathen..! 

 

Ok-ok...let's make that 7 or 8 minutes, although I did say "close to 10 minutes" my chaste one..! lol.gif

 

Think about it - it is never <"independant on (sic) image scale"> Kevin...image scale determines apparent rotational speed & thus capture duration: I vary our capture timespans for Jove from anywhere between 150" (usually around opposition & maximum apparent diameter) & 210 seconds around the time Jove is much smaller therein at the end of the imaging season. (about now for instance)

 

When Mars is down to around 5" in diameter I've regularly captured for a total of 10 or more minutes - remembering that Mars doesn't rotate anywhere near as fast as (say) Jove in comparison - & these days we tend to stick at 5 minute captures for Saturn regardless of the apparent diameter...because although we used to employ 6 minute "standards" for Saturn, nowadays you can collect almost 100,000 frames in total over 5 minutes - so what's the point in going any longer..?

 

But perhaps I should lift my game & strive for better detail in my image outcomes by bowing to Mother Rumour..?

 

 

Thanks for pointing out the typo. I wasn't blindly following a rule of thumb or a rumour, moreover I was simply observing that for a 3 min capture the planet rotates 1.8 degrees or so, whereas with a 10 minute capture it's in the region of 6 degrees. My point was and is that this is independent of whatever image scale it is viewed at. I can appreciate though that the resultant image blurring is less noticeable in smaller images (ie, smaller image scale) and thus for smaller image scale the capture duration can be longer with no apparent detrimental affect. So we are talking about the same thing, I believe.

 

 



#13 Kokatha man

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Posted 12 October 2019 - 06:45 PM

<"So we are talking about the same thing, I believe.">

 

As long as you're acknowledging that the apparent surface/linear motion appears greater for larger disks Kevin, even though the rotational angle remains constant. (regarding them as solid bodies also of course...& we are dealing with "apparent" diameters here, which varies with image scale) 

 

Hendric, you say <"I was targeting a histogram closer to 240 out of 255. Should I aim for 128 out of 255?"> in response to my <"As long as you can get a histogram of about 50% - 55% without resorting to anymore than (roughly) 80% or so gain this will suffice"> 

 

The "80%" was in relation to maximum gain values (seems both ASIcap & FireCapture both have a numerical limit of "600") so I'm suggesting that 128/255 coupled to whatever gain is required to get that 250fps/4ms (4000us) exposure as long as you don't have to increase gain much beyond (say) 450 or so. (I can't see any of the other parameters in your ASIcap figures...) 

 

I didn't realise you were using an Alt/Az mount so of course field rotation is something you have to be mindful of! ;)




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