Another Jupiter and Europa with Barlow

[Ringrocket]

My second try at processing my second jupiter.

I used a TV 2.5x Barlow. So that means f30 for my f12 scope. I'd rather use a lower f value, but I found that using the Antares Shorty 2x Barlow the result is also around f30 (instead of f24). Might have to look for a 1.5x Barlow, or is there another way to get at a f value below f30 with my 2.5 Barlow ? Would omitting the star diagonal help ?

Had to use a lot of wavelets which is vissible.....

[Space Cowboy]

Very nice image! Be careful with the wavelets as its just a tiny bit over done. f30 should be fine . I would recommend removing the diagonal. The less glass between camera and Planet the better. If seeing is reasonable I would stick with f30.

[Clayton]

Nice result Jeffrey

I calculated the f ratio to be more like f35 going by the size of Jupiter in your image using the formula

The solution is to work backwards from a captured image and calculate the focal length directly. All you need to know the pixel size of your camera (in microns) and then use the following formula:

F = 206.265 x P x U

---------------

O

P is the size of the object in pixels as captured

U is the pixel size of the camera in microns

O is the true size of the object in arc-seconds

F will be the focal length as calculated from this formula, in mm.

I'm guessing you haven't resized the image and then cropped it ?

So losing the diagonal will probably help you to lower the gain a bit

[Ringrocket]

Thanks for pointing this out Clayton, I learned something now:

I calculated and checked the real operational focal lenghts and f ratios of my 150mm SW-Maksutov. Useful Formulae

It turns out using the 2.5x Barlow gives me f36 as you said, and without Barlow its f15 (instead of the reported f12 as the specs described)

(and with the Antares 2x Barlow its even f39

So I did some reading on the internet and it turns out that what I did not know is that in SCT (or Maks) with movable mirrors the focal lenghts increase much more than the shift of the primary mirror. So I guess because I use an added Crayford focusser and 2" to 1.5" adapter and a diagonal I had to move the primary mirror closer to the secondary and thus increased the focal lenght (and f ratio) considerably. http://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EFLMAKCASS.pdf

I now plan to remove the diagonal and see what happens (or put it after the 2.5 Barlow which is a powermate so the distance after this barlow to the chip does not matter)

Yep, it's only theory this evening since despite good seeing predictions here the air is filled with fog which luckily prevents me from seeing the clouds that spoil my clear skies

[Ringrocket]

Very nice image! Be careful with the wavelets as its just a tiny bit over done. f30 should be fine . I would recommend removing the diagonal. The less glass between camera and Planet the better. If seeing is reasonable I would stick with f30.

Thanks Stuart

That's what I will do. It turned out the operational f ratio was 36

Removing the diagonal should remove 9 cm light path and if I understand everything correctly will bring the f ratio down to f30 again