Back to forums

Noob question about imaging Jupiter

Cor Berrevoets et al. Registax AstroSharp Ltd SharpCap Acquisition Solar System Jupiter
18 replies•425 views
Stuart Taylor avatar
Stuart Taylor avatar
Ok, so I have been trying to image Jupiter using the following technique

20cm (f/10) SCT sitting on a EQ6R Pro, 3x Barlow, ZWO ASI224MC and SharpCap cropped down to 480x360 ROI, 2 min videos at about 40 fps
I only have manual focussing (so the image wobbles around like crazy when I try to focus)
Autostakkert3, selecting the frames above 50% quality (so approx 30% of them)
then wavelet fiddling in Registax

The results are not so great.



Jupiter 17 August 2021


Is this because Jupiter is pretty low in the sky for me? (about 20-25 degrees)
Is my camera too small?
Is my scope too poor?
Michael Feigenbaum avatar
Michael Feigenbaum avatar
Perhaps trying at f/10 first might be good and work on some skills. I would think that a 3x Barlow is too much focal length unless you have tremendous seeing conditions.  It is tough to do good planetary at an altitude of less than 35° but it is possible.  Because Jupiter rotates so fast, a 2-minute run is too long.  One of the very best planetary guys recommends more like 50s runs to avoid the smearing of details caused by rotation.

I think your telescope is fine, your camera is fine too.  Planetary requires quite a different set of skills and procedures than deep sky.  I would recommend watching a couple of videos about planetary imaging that are available on The Astro Imaging Channel on YouTube.  The videos to watch are two featuring Agapios Elia and one featuring Niall McNeill.  

Those will give you a very good base from which to work.
Well Written Helpful Insightful Supportive
Lynn K avatar
Lynn K avatar
I agree with Michael, F30 may be too demanding unless you are near the equator with excellent  seeing.  Try F10 as Michael suggested and 2x at F20. The image will be a lot brighter and allow you to shoot at a faster fram rate.  I wouldn't go any lower than 60 fps and faster if you can.

I'm at lat 40.5 with terrible seeing. I haven't done planetary in a few years. I juat got a mono ZWO ASI 178. I'm going to give mono rgb a try.

It's all about the seeing. Sorry to say, but your image is not all that adnormal,  given low elevation  and maybe not so good seeing. In the North East clear nights can be the worst, and humid hazy nights can be the stadiest seeing.

Lynn K.
Helpful Supportive
JDJ avatar
JDJ avatar
A couple suggestions/comments:
(1) Check out the 'Major and Minor Planetary Imaging' forum on www.cloudynights.com. It's an amazing resource for planetary imaging.  I learned most of my planetary imaging techniques through that forum.  A couple more suggestions below based on information from that forum…
(2)  Seeing is king with planetary imaging.  So watch the forcasts for a night of predicted good seeing.  Even with the best equipment on a night of poor seeing the results will not be great.
(3) For the pixel size on the ASI224MC, the 'ideal' F/# is for planetary imaging is ~F/20.  This is a rule of thumb (ideal F/# = 5x pixel size in microns) I picked up on the CN planetary forum.  So, if you are shooting with an F/10 SCT and 3x barlow you are at F/30.  For the 224MC and and your SCT, try a 2x barlow.  By the way, the 224MC is an amazing planetary camera and my workhorse camera for planetary imaging. 
(4) Look into adding an atmospheric dispersion corrector (ADC) to your imaging train.  This will help with imaging planets at low altitude.

Good luck, honestly looks like you are on the right track to me!
Helpful Engaging Supportive
andrea tasselli avatar
andrea tasselli avatar
The first question is correct, Jupiter is too low for you (or for me, for the matter). Without even a wedge to correct atmospheric dispersion with a colour camera is a fool's errand so give up. Do not bother until the planet is above 30 deg.  Camera is ok-eish and a good C8 is still a very good instrument for its aperture. When the time will come get the correct image scale which for your C8 shouldn't be below .15"/px. Better above for all but the steadiest seeing. Frame rate is not really that important as long as you have a very low noise and enough frames to stack. As others have pointed out 2 min is far too much at 6 meter of focal length. 50s and even less depending on the resolution you aim at and the wavelength or colour band you are shooting with.
Helpful
Stuart Taylor avatar
Stuart Taylor avatar
Thanks SO much everyone. You guys are SO helpful! I really appreciate it
Michael Feigenbaum:
I would think that a 3x Barlow is too much focal length unless you have tremendous seeing conditions.

Yes, I was only using the 3x because it's a good quality one (Televue). My 2x is cheap and nasty unfortunately. So I have actually now taken down the SCT and mounted my Esprit 150. Besides having gorgeous optics it's only f/7 so should play better with my 3x Barlow.
Lynn K:
Sorry to say, but your image is not all that adnormal,  given low elevation  and maybe not so good seeing. In the North East clear nights can be the worst, and humid hazy nights can be the stadiest seeing.

Thanks Lynn. As well as being low, we did have some haze. And unfortunately, where I live the south is blocked. I only really get the NE to the SE. I need to move house!
Good luck, honestly looks like you are on the right track to me!

thanks so much. I really appreciate this.
andrea tasselli:
Without even a wedge to correct atmospheric dispersion with a colour camera is a fool's errand so give up


in fact, I just bought an ADC from ZWO, so maybe that will help
Lynn K avatar
Lynn K avatar
Hi Surart. I may have been confusing with my comment about the North East.  I was not referring to a direction but the North Eastern portion of the United States.  It is usually in the jet stream of weather turbulence and has normally very poor seeing.  During a hot humid night, the atmospheric temperature can be fairly consistent and can be the best for planetary.   Usually, visual is limited to 200x, but one can get 400x on a steady humid night.

My view of the planets is always to the south.

Lynn K.
Helpful
Stuart Taylor avatar
Stuart Taylor avatar
Lynn K:
Hi Surart. I may have been confusing with my comment about the North East.  I was not referring to a direction but the North Eastern portion of the United States.  It is usually in the jet stream of weather turbulence and has normally very poor seeing.  During a hot humid night, the atmospheric temperature can be fairly consistent and can be the best for planetary.   Usually, visual is limited to 200x, but one can get 400x on a steady humid night.

My view of the planets is always to the south.

Lynn K.

Hi there. No probs. I knew you were referring to your location on Earth (although I must admit, I assumed you meant NE UK, rather than NE USA).

My comment was perhaps a non sequitur in that I was bemoaning the fact that I can't really see south from my house. Which means I never get maximum elevation of targets. This makes for sub-optimal seeing obviously.

I need to move house ;-)
Robert Gillette avatar
Robert Gillette avatar
Agree with all the advice here. You also mentioned manual focusing. Fact is, you really need the fine precision of motor driven focusing to do any kind of astroimaging. ZWO, Robofocus, whatever.  Use a Bahtinov mask. Cheap and effective.

CS, Bob
Concise
Jesco avatar
Jesco avatar
Nobody mentioned it, but proper collimation is the first thing that you have to do. Without a well collimated scope, especially with an SCT, even the best result will be mediocre.

I recommend to collimate with your camera attached and work your from quite out of focus to almost in focus while you symmetrize  the diffraction rings.

This is a good ressource in the consecutive steps: http://www.astrophoto.fr/collim.html

The rest has been mentioned by the others here. You're probably overmagnifying (f/20 will be fine), an ADC will help a lot for us northeners, collect 3min videos, focus carefully and repeat it after each sequence. Learn to judge the seeing.
Helpful Concise
andrea tasselli avatar
andrea tasselli avatar
Agree with all the advice here. You also mentioned manual focusing. Fact is, you really need the fine precision of motor driven focusing to do any kind of astroimaging. ZWO, Robofocus, whatever.


Not at all! You can dispense with that particular kludge. If you can't focus and can't judge you're in focus...
Stuart Taylor avatar
Stuart Taylor avatar
Fact is, you really need the fine precision of motor driven focusing to do any kind of astroimaging. ZWO, Robofocus, whatever.  Use a Bahtinov mask. Cheap and effective


Yes, I am rapidly coming to this conclusion! Manual focussing is a real pain especially on a SCT with a mirror focusser. I am investigation adding a motorised crayford to the SCT.

Yes, I always use a Bhatonov mask on some stars first. Indispensible!
Jesco:
but proper collimation is the first thing that you have to do


Thanks. I do actually check that. Normally when I set up my various camera, spacer etc combos the focus is miles off, so I get the collimation sorted out then
andrea tasselli:
Not at all! You can dispense with that particular kludge


Are you disagreeing with the motor focusing advice? Why? I find that when trying to focus with the SCT the planet often moves totally out of the field when I adjust the mirror position! It's a real pain. Surely motor focusing will help with that?
andrea tasselli avatar
andrea tasselli avatar
Stuart Taylor:
Fact is, you really need the fine precision of motor driven focusing to do any kind of astroimaging. ZWO, Robofocus, whatever.  Use a Bahtinov mask. Cheap and effective


Yes, I am rapidly coming to this conclusion! Manual focussing is a real pain especially on a SCT with a mirror focusser. I am investigation adding a motorised crayford to the SCT.

Yes, I always use a Bhatonov mask on some stars first. Indispensible!
Jesco:
but proper collimation is the first thing that you have to do


Thanks. I do actually check that. Normally when I set up my various camera, spacer etc combos the focus is miles off, so I get the collimation sorted out then
andrea tasselli:
Not at all! You can dispense with that particular kludge


Are you disagreeing with the motor focusing advice? Why? I find that when trying to focus with the SCT the planet often moves totally out of the field when I adjust the mirror position! It's a real pain. Surely motor focusing will help with that?

I had few SCTs in my time so I experienced that kind of pain. The answer to your worries isn't a motorized focuser per se but an external focuser, whether motorized or not is immaterial to the art of reaching focus. This is even more so with planetary imaging.
Jesco avatar
Jesco avatar
Stuart Taylor:
andrea tasselli:
Not at all! You can dispense with that particular kludge


Are you disagreeing with the motor focusing advice? Why? I find that when trying to focus with the SCT the planet often moves totally out of the field when I adjust the mirror position! It's a real pain. Surely motor focusing will help with that?

A motorfocus won't help you with mirror shift in an SCT. The only solution to that is adding an external Crayford, R&P or similar focuser.

A motorfocus is definitely nice to have. It allows you to approach the search for a best focus much more systematically due to it's repeatibility. But it's by no means a necessity. FireCapture has an excellent image stabilization mode where it keeps the planet centered on the screen (no ROI changes, no mount connection needed). As long as the planet does not move off-screen, this gives you a rock-solid planet image with no jiggles during focusing. It's the second item from the top.

Jesco
Helpful Respectful Concise Supportive
Stuart Taylor avatar
Stuart Taylor avatar

 
andrea tasselli:
The answer to your worries isn't a motorized focuser per se but an external focuser


Right, I understand.
Jesco:
A motorfocus is definitely nice to have. It allows you to approach the search for a best focus much more systematically due to it's repeatibility. But it's by no means a necessity. FireCapture has an excellent image stabilization mode where it keeps the planet centered on the screen (no ROI changes, no mount connection needed). As long as the planet does not move off-screen, this gives you a rock-solid planet image with no jiggles during focusing. It's the second item from the top.


So which external focuser would you recommend? I was looking at the Moonlite ones. But they now only make them with a motor already attached apparently
andrea tasselli avatar
andrea tasselli avatar
Björn Arnold avatar
Björn Arnold avatar
Let me add my few cents to this. 

I don’t know which SCT you specifically have, so I can only add my experience with my Meade 8“ ACF. It is possible to achieve very good focus using the focus knob on the tube in combination with a Bahtinov mask (focused on a star of course). The flipping mirror from reversing the focus direction is common and therefore best practice is: defocus in clock wise direction and then focus turning the knob in counter-clockwise direction. This has the side effect that it holds the mirror in position (to some good extend). 

Another issue, probably not so much with planetary imaging if you keep the planet centered on the optical axis, is that with the additional focuser, you might add too much back focus. Although it’s a Common statement that SCTs have along back focus range, this only refers to the fact that the light on the optical axis can be brought to good focus. However, it may mean that the whole field of view is subject to amplified optical aberrations. EdgeHD scopes are much more sensitive to a departure from the design back focus.

Regarding the collimation: for best imaging, it does not suffice to assure that the donut is nicely symmetric. You have to collimate examining the diffraction rings when only slightly out of focus and the airy disk when focused. For the latter, very good seeing conditions are required.

Björn
Helpful Insightful Respectful Engaging
Stuart Taylor avatar
Stuart Taylor avatar
Stuart Taylor avatar
Stuart Taylor avatar
Björn Arnold:
Regarding the collimation: for best imaging, it does not suffice to assure that the donut is nicely symmetric. You have to collimate examining the diffraction rings when only slightly out of focus and the airy disk when focused. For the latter, very good seeing conditions are required.


Yes, I think I was too quick there. I have now read up about full collimation, so I think I am going to do that on my next clear sky. It may be why my planetary images are a bit disappointing (aside from the poor seeing and low elevation)
Well Written