This is currently where I'm at. Suggestions for improvement?

[Stonius (Markus)]

Here are the results of a session I did last night with an 8" f/6 dob.

http://markusstone.com/hosted_files/...t%20Mosaic.jpg

I know I've seen so much more detailed shots around here, so I'm wondering what I need to change, as seeing was pretty good for me last night, and I'm confident that my collimation was as good as it gets on this scope.

I shot video using a Canon 5D at ISO 800 projected via a bintel 2" barlow coupled with a 9mm TV Nagler (yes, I know, polar opposites in optics, but it's what I have) held in place by a rig that is not ideal in that it is very adaptable, which means it's squared by eye.

You'll notice an artifact on Jupiter in the form of a line that goes roughly from pole to pole. I literally have no idea what this is, though I've seen it before on my pics. Seems to be a processing artifact.

Saturn was grainy on account of having to up the ISO from 800 to 6400 to get an exposure. Strange I didn't have to do this with Mars or Jupiter.

Mars I think has a false lightening of the left limb caused by my post processing I think, though it has brought up more of the surface features than I could actually make out on the night.

Also, I don't have a motorised mount, a field flattener, or a fancy focuser. I did notice that the chromatic aberration got worse as the planet drifted towards the field edges, and the planet became more ovoid in the process. Maybe one of the above would help? Maybe I need to get better at post? My workflow so far is PIPP to Registax, finish in Photoshop.

Thanks for any suggestions...

[raymo]

O.K. Markus, firstly, for the method you are using, the results are pretty
good.
Secondly, eyepiece projection, which is what you were using, is the least
preferred method, as it produces the lowest quality images generally, and
will exhibit any aberrations inherent in the particular eyepiece type. To get high power it would be much better to use just a 5x barlow without an eyepiece. If you don't want to fork out for a 5x barlow use a $15 webcam from Kmart with a 2x barlow. There are too many points to address here. Jupiter is large and bright, and Mars
is small but bright, whereas Saturn whilst fairly large is nothing like as bright as Jupiter or Mars, whose light is concentrated in a small area.
The light edge on Mars is the polar ice cap.
raymo

[Stonius (Markus)]

Originally Posted by raymo

...it would be much better to use just a 5x barlow without an eyepiece...

Ahh, thanks!

The light edge on Mars is the polar ice cap.
raymo

Really? I thought the one on the right was the polar cap, but the one on the left, being far more extensive and a warmer color than the other would have to be a post-processing artifact?

Cheers and thanks for your advice!

Markus

[raymo]

Sorry, wrong edge. I don't do much planetary processing, so can't help much with that possibility. As it is a bit under exposed I suppose
it could be showing some oblique sunlight. I don't know where the sun would have been in relation to Mars.
raymo

[Stonius (Markus)]

So Raymo, hope you don't mind if I ask you one more question;

Are there really then, 2 kinds of barlows? Those designed for visual and those designed for photography? I mean I can't imagine a 5x would have much use visually. But even with a 2x, are some more designed for visual in terms of, say field flattening, or the number of elements or just general tolerances?

Cheers

Markus

[janoskiss (Steve H)]

That's already very impressive for a Dob mounted scope!!

Is it a Dob with tracking?

You should not need a field flattener for planetary work, but some rudimentary tracking at least would be good. Also, probably more magnification would help. A 5x tele-extender perhaps. I'm telling you what I know from watching others do it and having some understanding of the process but at the same time having no experience at doing it myself (just to be clear about the high level of my ignorance).

[Stonius (Markus)]

No, no tracking. It's just a 15 year-old $600 Saxon. Thanks for the encouragement - I was thinking I was doing something wrong, considering how much better everyone else's planetary images are. At least now I know that I'm pretty close to what a Dob can do in terms of planetary. Though, I might look into a 5x barlow in the classifieds at some point, as suggested by Raymo. :-)

Markus

[raymo]

Hi Markus, A basic barlow is suitable for both visual and imaging, coming
in usual sizes of 2 to 5x. Many people with short focal length scopes use a 5x
to give them a decent focal length when viewing or imaging small targets. A 2x doubles the focal length of the scope, but at a cost; you need exposures four times as long to get the same effective exposure. The increase in magnification is linear, but the increase in exposure time is a square function, so a 3x barlow requires 9 times the exposure time.
Some more expensive barlows do have more than one function, such as
correcting various aberrations. Some have ED glass, which serves little purpose, as a barlow is a divergent lens, not a convergent one.
You won't do much better with the dob, because at the high powers needed for planetary work, and without tracking, your videos will be very short,
giving not a lot of frames to work with.
raymo

[janoskiss (Steve H)]

Have a read of this from our very own Mike the IceMan:
http://www.iceinspace.com.au/63-201-0-0-1-0.html

[Atmos (Colin)]

As has been mentioned, doing planetary work does not require a field flattener, the newt/dob version of this is a coma corrector. I imagine that the chromatic aberration that you're experiencing is being caused by the Bintel Barlow.
Although it is probably as expensive as your scope, the TeleVue Powermates are fantastic and you can get an adapter so attach your SLR onto the back of it.

[Camelopardalis (Dunk)]

As all of the above, tracking is almost essential as you increase the focal length, but you've done well there

Camera sensitivity also makes a big difference - the small sensors in good planetary cameras are worlds apart from DSLRs in this respect, but the small sensor and increasing focal length makes it doubly hard to keep the subject on the screen without good tracking.

As you found out, Saturn is noticeably dimmer than Jupiter or Mars - about 2 magnitudes!

[leon]

I reckon that is pretty impressive, wish i could have acheived something even close to that some years ago, well done

Leon