Optimal Optical Setup for Planets

[JohnSadlerAstro]

Hi,

A quick question about planetary imaging for tonight: I have an OpticStar 90s Gold. (F=800mm) which I'm wanting to use on Saturn Jupiter and Mars.

http://www.opticstar.com/Run/Astronomy/Astro-Telescopes-Opticstar.asp?p=0_10_1_1_65

I am using an ASI120MC, I normally capture in the smallest res mode (I think 320x480, something like that). However, I also have a 2x Barlow. I'm a bit confused as to how magnification is calculated with a camera, I couldn't find any equations, etc. Should I use the Barlow or not? Does the 2xDiameter rule count with a camera?

I don't want to overload the magnification, yet I don't want to leave the image small if I don't have to. ? 

Thanks for looking!  

John

[catburglar]

Use the Barlow....the optimal f ratio for planetary imaging is around 5 times the pixel size. For the ZWO120 with 3.75micron pixels you want to be working at around f18. Your sncope at f8.8 x 2 is almost perfect (but only for planetary not for DSO).

[MarsG76]

Magnification with a camera is not really a accurate term... focal length is more imaging terminology.... BUT as a rought rule you could say that the magnification is 1X magnification per 50mm focal length... and yes the 2X barlow still applies.

As with most things tho it's not just that simple... to determine magnification than the size of the sensor will need to come into play and multiplied by a factor of what ration to a full frame sensor you imaging sensor is.... (full frame being accepted in the photographic world as 35mm (but not always since in the astro world the KAF8300 is being called "full frame".. see the confusion and magnification not being the best term?)

With the 2X barlow, depending on how far the sensor is from the barlow, if it's too far than the 2X barlow can work as a higher power lens.... for example when I image planets with my 2X celestron barlow and the sensor is about 17cm from the barlow due to the flip mirror, mathematically my barlow is than equivalent to a 3.33X.