Beginner needs help imaging Jupiter

[Lee_P]

Hi everyone,

I'm taking my first steps into telescope astrophotography, but have stumbled at the first hurdle... I'm trying to image Jupiter, but am sure I'm getting something fundamentally wrong.

I've got my 102mm refractor pointing at the planet, and have my Nikon D700 attached via T mount directly onto the eyepiece. I can't see any detail on photos taken; they just look like featureless blobs. (Cropped image attached). At first I thought it was the focus, but I can't get it any sharper through the viewfinder. I know that stacking will help, but surely some bands should be visible even with a single image? The view with my eye up to the eyepiece is a lot better; two bands are clearly visible.

Any thoughts on what I'm doing wrong? I bet it's something obvious...

Thanks,

  - Lee

[Kropster]

You don't need the eyepiece.

The camera body should mount to the tube that the eyepiece goes in.

The image is then focussed on the camera chip by adjusting the focus rack in or out.

If you leave the eyepiece in, then you won't be able to focus the image.

[m37]

A DSLR in a StarTravel 102 is going to give you a pretty small image of a planet but if you have a SW barlow with the T-thread you could chuck that in the mix!

Alternatively a cheap webcam would help loads. Lifecam cinema HD or something should do the trick to start with. Heck, stick that in the barlow too!!!

cheers

Chris

[Pete Presland]

looks like focus to me as well, i would also echo the points re - the cheap webcam.

[PeterCPC]

I'm not clear how the camera was attached - can you attach a thumbnail showing the camera attached to the scope.

Peter

[datman]

"I've got my 102mm refractor pointing at the planet, and have my Nikon D700 attached via T mount directly onto the eyepiece."

Definitely out of focus!

Hopefully you mean the camera is attached to the focuser tube via an eyepiece adaptor, or some sort of T mount to MCT adaptor.

If not, you need a T mount with 1.25" EP adaptor, and an extension tube.

You normally use a diagonal when viewing, so you need an extension tube of about the same light path as the diagonal. Measure to

the angled part of the diagonal from where it comes out of the EP holder and from the angle to where the EP fits. Mine is about 75mm.

You can test it by putting the EP adaptor of the camera into the diagonal,(assuming you have an EP adaptor on your T mount,

you should then be able to focus. You could try this during the daytime on a suitably distant object.

This is not the ideal way to image though, you need the extension tube. If you have any Barlows, you can turn them into extension tubes

by removing the lenses.

At f1300 you should see a small but very sharp Jupiter plus all of its moons. Once you've achieved this you can think about Barlows.

[Lee_P]

Thanks for all your comments! To clarify the set-up I was using, I had a 45 degree diagonal, into a 2x barlow, into an 8-24mm zoom eyepiece (set to around 10mm), attached to the D700 camera with T mount. It was my understanding that this was an afocal set-up, i.e. the camera sensor was where the eye would normally be. Is this wrong?

The reason I thought it was in focus was because through the viewfinder Jupiter looked like a big blob, so I turned to focus, made it small, then too far and it became big again, and I settled on it being smallest. 

I'll try again tonight (weather permitting!) minus the diagonal and eyepiece. Is this what you recommend? If so, one question: if the eyepiece shouldn't be used, why is it threaded for a T mount? I've taken (filtered!) photos of the Sun like this.

Thanks again, all your help is hugely appreciated.

 - Lee

[Kropster]

It would work if you attached a camera with its lens still fitted to the eyepiece.

The camera lens acts much the same as the eye.

When you remove the camera lens and project directly onto the sensor chip, you then need to remove the eyepiece to get focused.

Not sure why your eyepiece would have a T-thread.... maybe for a camera mount?

[Cornelius Varley]

Some eyepieces do have a t thread or threaded to accept a suitable adapter - the Baader Hyperions and some zoom eyepieces. The t adapter attaches to a camera t-ring and then to the body of the DSLR, this type of imaging is called eyepiece projection. Afocal imaging is usually done with a compact camera or fixed lens camera shooting through an eyepiece.

[Lee_P]

A-ha, that's what I was trying! Eyepiece projection. Any ideas why I can focus on the Sun easily enough, but apparently not Jupiter?

[Lee_P]

This video describes the technique I was trying well: 

The only problem is that my image of Jupiter is awful and I'm still not sure where I'm going wrong. Do you experts still think it's out of focus, as was previously suggested? I'm not so sure, as explained previously ("The reason I thought it was in focus was because through the viewfinder Jupiter looked like a big blob, so I turned to focus, made it small, then too far and it became big again, and I settled on it being smallest.")

[Cornelius Varley]

Atmospheric distortions will make focusing on Jupiter tricky. 

[Lee_P]

That could explain it, although the view through the eyepiece with my eye was pretty good. If the atmospheric distortions were enough to make the eyepiece projection photo bad, would that be evident with a visual observation?

[Cornelius Varley]

In the video the presenter didn't use a barlow lens in the image train, instead he used a variable eyepiece projection adapter. The distance between the eyepiece and the camera's sensor can be varied, the greater the distance between the eyepiece and the sensor the greater the image scale.

[Lee_P]

That is a big difference. Unfortunately I don't have a variable eyepiece projector. Do you think I'll get a better result if I remove the lens from the barlow and simply use it as an extender? 

[Cornelius Varley]

That could explain it, although the view through the eyepiece with my eye was pretty good. If the atmospheric distortions were enough to make the eyepiece projection photo bad, would that be evident with a visual observation?

Not necessarily. If you observe Jupiter over a period of minutes you might see that sometimes the banding is visible and then disappear a few seconds later, one reason why imagers take video clips to catch the seeing. I also suspect that the combination of barlow and eyepiece would contribute to the blurred image, probably too much magnification for imaging.

[Cornelius Varley]

That is a big difference. Unfortunately I don't have a variable eyepiece projector. Do you think I'll get a better result if I remove the lens from the barlow and simply use it as an extender? 

The distance between the eyepiece and the sensor governs the image scale. If you remove the lens from the barlow all you are doing is adding unwanted distance between the sensor and the focal point of the telescope, you would then have to wind the focuser in to compensate for the length of the barlow tube.

[Lee_P]

Ok, so on the next clear night I'll try a similar set-up but minus the barlow and using my D90 to take a video instead. No doubt I'll end up getting a webcam or somesuch, but I'd like to get the basics sorted as much as possible with the equipment I already have. Thanks very much for your help!

[Lonestar70]

Hi Lee_P,

You may get better results if you remove the diagonal and replace it with a 2" straight extension... the diagonal will create a certain amount of loss for imaging purposes.

The type of extension to use would be similar to this: -

http://www.harrisontelescopes.co.uk/cgi-bin/sh000001.pl?WD=tubes%20extension%20focuser&PN=Revelation_50mm_Extension_Tube_2_%2ehtml#aFF114

You may also increase the image size by adding an extension between the eyepiece and the camera body as shown in the attached Baader data sheet... see setup second from left at the bottom.

Focus is very critical with this type of arrangement.

Hope this helps.

Best regards.

Sandy.

hyperion_overview.pdf

[Cornelius Varley]

Look on Astroboot for t threaded extension tubes and variable extension tubes.

[Owmuchonomy]

Good advice from Cornelius. There is no problem attaching your DSLR body directly to you eyepiece. I do it all the time, either directly as in my 8mm Baader Hyperion or via a Revelation 65 mm extension tube into which you can drop a plossl. I think your main objective next time is to take a video and then process it. I use PIPP and then Autostakkert. Here are 2 shots done using each of the above methods.

[PeterCPC]

To ensure that you get good focus I would use a Bahtinov mask. You focus on a nearby star then swing to your required target without touching the focuser again.

Peter

[datman]

Ok, so on the next clear night I'll try a similar set-up but minus the barlow and using my D90 to take a video instead. No doubt I'll end up getting a webcam or somesuch, but I'd like to get the basics sorted as much as possible with the equipment I already have. Thanks very much for your help!

The ccd of the average video camera is only 1/4" compared to your current camera that is tiny. It will be much harder to get your object onto the chip.

Pixel sizes are similar so the image would be the same size, you'd just have lots of background with the DSLR.

I would suggest you stick with the DSLR until you are it's master, especially as it can do video. The DSLRs frame rate will be slower because of the image size.

As I said earlier, you could use the diagonal with the camera to test that it works as expected. There would be some distortion and light loss but it will work.

Once you have that sorted buy an extension tube.

[Lee_P]

Thanks very much for the advice everyone; it's immensely useful having you all chip in. Just three quick (!) questions this time:

* How much of a difference do you think replacing the diagonal with an extension tube will really make? I'll stick with the diagonal for now as datman suggests, but I am curious.

* I don't quite understand the Bahtinov mask that PeterCPC suggested. Can't focus be achieved just by turning the knob until the star / planet / whatever is as sharp as can be? In what way does the mask make it easier?

* I found an old Meade Lunar Planetary Imager camera at the back of a cupboard at work. http://www.meade.com/autostar/lpi.html Any thoughts on this? Would it make more sense to stick with the D90?

Thanks again to you all for your patient replies!

  - Lee

[riklaunim]

* I don't quite understand the Bahtinov mask that PeterCPC suggested. Can't focus be achieved just by turning the knob until the star / planet / whatever is as sharp as can be? In what way does the mask make it easier?

Bahtinov mask can be handy for setting perfect focus, but it's most useful for DS imaging. With planetary it's better to set focus by looking at the camera preview. Usually a motofocuser is used so that focusing is slow and precise and no shakes are added.

 

* I found an old Meade Lunar Planetary Imager camera at the back of a cupboard at work. http://www.meade.com/autostar/lpi.html Any thoughts on this? Would it make more sense to stick with the D90?

Usually it's very poor with image quality. Very old.