Jupiter Help

[groberts]

I have been struggling for a while to get a good, sharp image of Jupiter using either my SW 150PL or now mostly the William Optics GT81, with a x2 Barlow the image remains quite small either with ZWO 120MC webcam and noisy.  

I'm wondering what is the best set-up - would the SW or preferably the WO take a larger Barlow and retain focus, say x3 or even more, or would a Powermate be better / what power? + Any other thoughts most welcome, especially on image capture settings and getting a good focus - I'm thinking Bahtinov on a star + move to and refine whilst looking at Jupiter? Thanks.

[kalasinman]

I am just studying the same issue. I read elsewhere that a target FL is indicated by FR of scope x pixel size= target FR. May not be perfect but gives an idea of where to go.

[ronin]

I suspect you overall focal length is too small.

There is a good image of Jupiter in another thread, the person used a C9.25 and a 2x power mate. So a 4700mm focal length, the 150P anmd the GT81 are goiung to get no where near that.

Scope was C9.25 - suspect the same bassic OTA as the originally said CPC but for accuracy updated.

This is/was the post referred to:

http://stargazerslounge.com/topic/234009-behold-a-break-in-the-clouds/?hl=%2Bpowermate#entry2532030

[leelee970]

Try this to calculate what you'd see.

I suspect you'd need a X3 barlow 

http://www.12dstring.me.uk/fov.htm

Lee

[groberts]

Thanks, that's what I thought + like the FOV calculator link.

I am now left with these questions:

1. According to my online search, the angular dimension of Jupiter varies from 29.8" to 50.115", so what FOV will work? My GT81 with a x2 Barlow = 11.26' x 12.95' and the SW 6.81' x 5.16', compared to the C9.25 of about 3.51' x 2.67'.  Put another way, is there an empirical relationship (equation?) between the FOV or FL and the camera sensor size and the dimension of the object being viewed to get a good image?

2. Will I get focus using a x3 Barlow or better still Powermate? I had a lot of problems with the SW 150PL in the past ( I believe reflectors are notorious for such problems) not sure about the WO GT81, which is newer.     

[kalasinman]

Take a look at this series. Very clear and helpful...