Jump to content

Narrowband

Dobson 12” F5 upgrade


Recommended Posts

Hey guys, I’ver tried several different eyepieces (televue, Meade, etc) and I’m not too happy about the results I’m getting observing Jupiter and Saturn on my 12” F5 Dobsonian.

It’s not too easy to focus, I don’t really know if it’s coma or chr aberration. Could you give some advice as to how identify these problems and what solutions exist

 

thabk you all

Link to comment
Share on other sites

HI Jazzmatazz, I have a Skywatcher 12 inch Dob (f4.9) and have had some wonderful views of both Jupiter and Saturn, really sharp and contrasty with my Baader Morpheus 6.5mm, Baader Mk4 zoom and more recently a Skywatcher 4mm Planetary.

My first suggestion would be to do a star test with your highest power eyepiece to check you have really good collimation, I know from experience with my scope that it only has to be slightly out of collimation to give unsatisfactory views, not sharp at all.

(Edit: I should add that here in Australia these planets are very high in the sky and that obviously helps a lot with clarity of view).

Edited by Geoff Barnes
  • Like 1
Link to comment
Share on other sites

When the planets are very low down they do not look as crisp and clear as they do when they are higher in the sky. You can also sometimes notice what looks like chromatic aberration but this is actually caused by atmospheric dispersion due to the low altitude of the target.

Since the planets have been low in the sky over the past couple of years I have tended  to prefer the views of planets through my refractors rather than my 12 inch dobsonian. When they have been higher in the sky the dobsonian has produced stunning views though.

I doubt the eyepieces are to blame in this instance.

 

  • Like 2
Link to comment
Share on other sites

53 minutes ago, John said:

When the planets are very low down they do not look as crisp and clear as they do when they are higher in the sky. You can also sometimes notice what looks like chromatic aberration but this is actually caused by atmospheric dispersion due to the low altitude of the target.

Since the planets have been low in the sky over the past couple of years I have tended  to prefer the views of planets through my refractors rather than my 12 inch dobsonian. When they have been higher in the sky the dobsonian has produced stunning views though.

I doubt the eyepieces are to blame in this instance.

 

Just curious, are you tempted by bigger dosbonians? do you think a 20" dobson will give much more detail on planets? i've been thinking about a new lightbucket!

 

Link to comment
Share on other sites

2 minutes ago, Jazzmatazz said:

Just curious, are you tempted by bigger dosbonians? do you think a 20" dobson will give much more detail on planets? i've been thinking about a new lightbucket!

 

I have been tempted by larger dobsonians but that would be to see fainter deep sky objects rather than to get more detail on the planets.

I don't think a 20 inch dobsonian would show much more planetary detail than my 12 inch or my smaller refractors.

With the planets so low now it is much easier to get them in the view of a refractor and I feel a refractor handles the distortion that the atmosphere produces better than a larger aperture dobsonian.

I have a number of excellent refractors up to 130mm in aperture and those do an excellent job of showing me the planets.

 

  • Like 1
Link to comment
Share on other sites

With the planets as low as they are, your descriptions are about what I’d expect. Sorry. No magic bullet (except moving down under).

re. 20”. As long as you have space to store it set up & ready to go. 😁😁😁😁

Paul

  • Like 1
Link to comment
Share on other sites

10 hours ago, John said:

like chromatic aberration but this is actually caused by atmospheric dispersion due to the low altitude of the target.

That's exactly what I was experiencing last week when Jupiter was low. I went out again last night after checking my collimation but I suspect the improvement was down to Jupiter just being higher as John says. I hope you have better luck soon, I think it is all down to poor viewing at the moment. 

 

Link to comment
Share on other sites

On 01/06/2019 at 12:44, John said:

I feel a refractor handles the distortion that the atmosphere produces better than a larger aperture dobsonian

To back up that point I've seen Jupiter in three different scopes this year- a 14" dob, an 8" dob and a 4" mak. The mak gave much the best view, then the 8". I'm confident that at a higher altitude the order would be reversed, but at the moment planets are just not working well in the bigger dob. Still more than worth it for the DSO's though...

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.