Jupiter with repurposed geaar

[pmrid (Peter)]

I'm very new to planetary imaging. And I am not ideally equipped for it - either by aptitude or equipment. But I have decided to put my toe in the water and have a paddle with what I have.

This image is with an ED127 (a North Group APO of a native F/7.5) but with the addition of a TeleVue PowerMate x2. So I am at 1900mm FL and F/15 ratio.

The camera is a ASI290MC with 2.9 micron pixels imaged using the ROI routine in StellarMate set to 640x480. That allowed me to get just under 80 fps at RAW8. RAW16 knocked the frame rate back to about 30.

Then when Jupiter was quite high (about 60 degrees altitude) and the Red Spot was coming 'round the corner, a few sequences of 5000 frames processed with PiPP, Autostakkert3 and Registax6 with a final bit of sharpening in PS5.

That's it. I'm not unhappy with the result.

But detail is still lacking. So I have begun to refurbish an old 8" Newt (A F/5 GSO job) with a resurfaced mirror and a new focuser. The extra aperture ought to put me a bit further up the Dawes limits I hope. Of course the weather has turned cloudy and wet for the moment so heaven only knows when I'll get another run at it.

Ah well.

[Camelopardalis (Dunk)]

That’s a good start Peter

You’ve got the f-ratio in the sweet spot for the camera, you just need to up the ante with a bigger scope

A few tips… stick to 8-bit mode to keep the frame rate up. You will claw back the lost precision when stacking 1000s of frames.

Reduce the ROI to as small as you can tolerate - it can be a bit like a video game trying to keep the planet in the ROI, but if you keep the ROI fairly tight it not only helps maximise the frame rate but also keeps your capture data files more manageable.

When stacking in AS!3, check the sharpening box. It usually does a fairly reasonable rendition, albeit sometimes a touch over sharpened.

Oh and one final thing about the Dawes limit…it kinda goes out the window with planetary imaging since are not dealing with point sources. Many planetary amateurs image at less than 0.1” resolution, which with a 10-14” scope is a fraction of the Dawes limit, yet we see fine details discerned in their images (seeing permitting of course!)

[pmrid (Peter)]

Thanks Dunk. I’m going to switch up a little tonight to a x3 Barlow. I know that F/22 or thereabouts is probably stretching it a bit with the ASI290 but nothing ventured etc.

[Saturnine (Jeff)]

Hi Peter

I have and use the same equipment as you, NG 127mm, ZWO290MC and a 2.5X Powermate, using SharpCap for avi capture. In the software I set an ROI of 400 X 300 and for Jupiter , a Gain of 250 and with the planet near opposition and bright, can get a frame rate of 200/sec. in Raw8. With Saturn atm I increase the Gain to about 300/350 and get a frame rate of approx 100/sec.
The smaller the ROI you can set the less black sky and therefore less unneeded data to download for each frame, helping to increase the frame rate and freeze the seeing.

[pmrid (Peter)]

Thanks Jeff. As a matter of interest, what percentage of frames do you stack? I’ve been taking 10,000 frames and stacking only about 5%. Depends on the seeing I suppose.

[Camelopardalis (Dunk)]

Yeah depends on the seeing. The quality graph in AS!3 is relative, so you can have a plot that looks like there are only a few good frames and the rest are trash, but it can also be that most are decent and a few are great.

FWIW, if you look at my shots, Jupiter was a result of 25% of ~8000 and Saturn 33% of ~8000 frames. There is a tipping point where the number of frames stacked to reduce the noise (and thus improve SNR) also starts “reducing” the fine features too but it depends on the data, so experiment with multiple stacks to find the sweet spot - if you enable the Sharpening checkbox with 0% Raw blend then you’ll be able to see what I mean.

Just to echo what Jeff said, don’t be shy with the gain. My rig runs at about f/15 and I was using gain 350 on Saturn with my ASI462, which is the limit of analogue gain. Stay away from the digital gain that comes after that (higher values). The gain range on the 290 and 462 is the same btw.

[Saturnine (Jeff)]

Originally Posted by pmrid

Thanks Jeff. As a matter of interest, what percentage of frames do you stack? I’ve been taking 10,000 frames and stacking only about 5%. Depends on the seeing I suppose.

Depends on the seeing of course, if it is less than Pickering 5 I hardly bother anymore but in good conditions , Pickering 6 or above, usually take 8000 / 10,000 frames and after debayering and centering in PIPP will stack about 25%/30% in Registax.
In less than good seeing, will usually stack about 15%/20% and hope there are some usable frames for reference . Just for interest, I uploaded some images in the Beginners section , of Jupiter and Saturn taken on the morning of the 8th with the 127mm and 290MC, Powermate.
As Dunk said, too many frames means you are adding less than desired quality to the stack and compromising the fine detail and also, be gentle with Sharpening in Registax, 25 / 33% seems to work for me without adding noise.