Jupiter rotation

[26Left]

Hi all,

Here's my first Jupiter of the year - the first of many. It was taken with my Meade 127 refractor and a DBK camera. Focal length about 3800mm. Considering the dreadful seeing, I'm quite pleased with this one. The moon top left is Ganymede, a short time after it reappeared from behind the planet.

I've have been trying to find out what length video runs I should record; the issue being that if I record for too long, the planet's rotation starts to blur the image. I settled for a 2 minute run at 30FPS. This have me 3600 frames per run, which was plenty.

I plan to try my C11 next at a focal length of a little over 6 metres.

Could any one advise me on then length of video runs on Jupiter please? I guess that the smaller image scale from the C11 configuration will mean it should be a little shorter.

Thanks,

Tom.

[Kokatha man]

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Hi all,

Here's my first Jupiter of the year - the first of many. It was taken with my Meade 127 refractor and a DBK camera. Focal length about 3800mm.

I plan to try my C11 next at a focal length of a little over 6 metres.

Could any one advise me on then length of video runs on Jupiter please? I guess that the smaller image scale from the C11 configuration will mean it should be a little shorter.

Thanks,

Tom.

Hi Tom - I think you mean in the above "that the larger image scale from the C11.......etc"

Reality is that 3 minutes total avi length is no problems with f/l's (and hence image scales) way beyond 8000mm.....this is the scale I used on my C11 and am currently running 10000mm f/l's on the C14 and will do so with the VX16 also.

Quite a bit of nonsense is propagated about capture lengths - on CN last year I posted 2 images and asked people which was the sharper/more resolved.....they invariably chose the image that consisted of 2 consecutive DBK21 captures overlaid on each other with a total capture time of 6 minutes....!

Of course doing said meant that the majority of the detail (apart from the limbs) was aligned in the composite.....but the 3 minute maxim for scales up to 10000mm f/l or thereabouts is very safe, regardless of what else you may hear..!

[26Left]

Thanks Kokatha Man,

Less arc seconds per pixel. Or more pixels per arc second

When I was imaging Saturn, I went to 6 minutes, but Jupiter's a bigger beast. Thanks for your reassuring suggestion. In fact, I am outside now with the DBK on my C11 - first light. I've just changed from 2 minutes to three.

I'm watching the GRS and I think it will cross the meridian in 20 minutes or so. Now, it looks to me as though the GRS is moving as I watch it. Can't be. Must be my imagination. HAHA.

I'm surpised how much detail I can see on screen considering the seeing tonight. Looks promising, and I'll post the result tomorrow.

[neil phillips]

is the meade a apo ? colour looks very natural for a achro ? nice tight shot, cant wait to see the c11

[26Left]

Hi Neil,

It's the Meade 5000 5" triplet, which is an apo. Visually and for DSO photography, it's superb. And, it's also served me well for planetary imaging. One of my early Saturn images was published on the SaN magazine cover disk this month (although the viewer they provide rescales the image, so it doesn't look great unless you dig out the file and view it directly).

But, I think the the limitation of a 5" scope for planetary imaging is the scale you can achieve. So, when I had the opportunity to buy a used C11 at a real bargain price, I jumped at it

I haven't looked at the images yet. Proper work has to come first - what a distraction from astronomy.

[barkis]

Sure is a fine image of Jupiter Tom. The Apo. has done a splendid job together with the DBK Imager. All looks set fair for some cracking stuff with the C11, especially with Opposition due in October, and the 50 arc second disc diameter.

A mouth watering prospect indeed.

Ron.

[neil phillips]

Hi ok that makes sense, pretty much agree with your assesment of using quality refractors for planets, i would love a 8" triplet. wouldnt we all. for those that want hi res and are not loaded, newts and scts are really the only choice i think, im talking 10" and above, i know theres been some odd ones pop up, here and there like Orions 10" 12" OMC maks. but unless you go to 8" 7" ( skywatcher maks ) there really isnt a lot of choice for high focal length work other than the SCTS and newts. I dont really think the market supports companys making specialist planetary scopes above 8" which is a shame. How about a 12" f20 1/10th pv SCT with smaller secondary to match. With fans on the rear. around 5000 mm native focal length. dream on 2x ultima and your at 10 meters. Will be watching to see your C11 shots. once again a nicely balanced and processed jupiter

[26Left]

Your dream spec sounds just right. An 8" triplet would also be nice, but I don't think I could lift it.

Well, Jupiter was harder than I thought it would be. Seeing was pretty bad until about 3am. This was one of the last runs I recorded. As the seeing improved, the focusing got easier and some detail started to appear. I've resisted the temptation to continue sharpening.

Given better conditions, I'm sure I can improve on this. But, not bad for first light.

[oldfruit]

Great results, i would be proud of that.

[KE400]

Both images are things to be proud of, well done, look forward to seeing more images from you.

[Kokatha man]

That's a nice image you've just posted also Tom....!

[neil phillips]

Very nice, you cant beat focal length and apeture for resolution, and this proves it

[26Left]

Thanks all.

More than anything, what this move from 5" to 11" has shown me is the importance of good seeing for planetary imaging. The image scale on the C11 image is 0.18 arc seconds per pixel and the seeing didn't support that sort of scale. In fact, the image looks better if it's reduced in size a little - smaller, but sharper.

So, I'll be waiting for nights of good seeing and then having another go.

[neil phillips]

Of course thats exactly right, but not just good seeing compared to a smaller refractor and air cells, good collimation and cooldown, more things to affect the larger setup all round. But when these things are working in your favour, i think the result speaks for itself.

[AztecastroMcJ]

Yep some great results there Tom

i was a bit dissapointed with my 1st results from C11 aswell,

but as has been said when seeing good the C11 should really shine,

James

[astroman001]

Nice processing on both images, can see you were seeing limited with the C11. Regarding total imaging time, I image for 1 min on R, 1 min on IR and 45 secs on G and B, I go for longer on R and IR because they are used to defime the detail in the final image. 3-4 mins is fine.

regards

Peter

[Clayton]

Very Nice Tom. Hope the seeing improves

[26Left]

I put this animation together from the three minute video I used to make my image of 1st September. It's the first few frames and the last few frames, so it shows the rotation of the planet over three minutes.

The animation is a little crude, but there's not much doubt that the rotation is quite noticeable. The apparent diameter of Jupiter was 44.9 arc seconds and, at my focal length of 6.6m, I calculate that a point on the meridian / equator would cross one pixel in 44 seconds. A point at 30 degrees latitude would take 51 seconds to cross a pixel. The animation seems to bear this out, with about four pixels movement over the three minutes.

The question is whether this actually matters. I realigned and stacked the first 90 seconds of the video to see if the image improved. I cannot say that there was any improvement in detail, although the resulting image was a little noisier. It also occurs to me that Registax would follow the alignment points as they rotate, although I'm not sure what that would do to the edges of the planet.

So, no real answer, and I cannot really reach any sensible conclusion until I image on a night of very good seeing. For now, I think I shall continue with three minute recordings. With Virtualdub, it's easy enough to pull out a shorter "sub-video" if I think it's worthwhile. For that matter, I suppose one could record a 30 minute video and just pull out shorter sections for aligning and stacking. But, the file size would be huge.

Tom.