ParamountObservatory I have tried using a Bahtinov mask and capture, last night I simply tried using the visible image and set via app, see attached image.
The Bahtinov mask is a diffraction mask and is only good for point sources. So it will not work even with one of Jupiter's moons. Instead of thin diffraction spikes, the spikes will have the width of the moon!
What I usually do is this. First, go to a reasonably bright star nearby (I was using Markab just last week when capturing Jupiter) and use the Bahtinov mask to achieve focus on the star.
And remember, with an SCT (and even a Takahashi Mewlon) the last focus knob movement should be in the counterclockwise direction. The way, gravity will help keep the main mirror in position.
Then, move to Jupiter. Do not refocus when you get to Jupiter, since the focus change will be in the sub-sub micron range. I.e., Jupiter and stars are so far away that both are practically at infinity as far as your optics go.
There should not be any mirror flop when you hop from a nearby star.
BTW, why are you using a focal reducer followed by a Barlow? You can achieve almost the same plate scale by removing both of those and get a sharper image.
my colours look very washed out.
That is because you are using an IR pass filter. It will not give you natural colors. Use a UV-IR cut filter instead if you want more natural colors, and then change the color balance so that the red, green and blue histogram all peak at the same ADU. Keep from saturating 200/255 ADU or so should work, and that should then give you the color balance that you want.
As to the exposure time, I have found that Jupiter rotates so rapidly that the shadow of a planet and Jupiter's red spot is smeared even with a 5 minute exposures. The smearing is apparent even with my silly 6" SCT.
If the "seeing" is not great, you could also try reducing exposure time to 5 ms, as long as the frame rate goes up correspondingly, so you won't loose total integration time. Try something like keeping only 5% of the frames in something like AutoStakkert!. With poorer seeing, I have seen 2% to provide sharper images than 5%; but then noise tends to creep up -- you have a C11 so SNR should be less of a problem, so try to pick only the best "frozen" images. That is what "lucky imaging" is about -- keeping only the exposures that are not smeared by the atmosphere.
Use as small FOV as possible to achieve the highest frame rate as possible. With my toy SCT, I could go down to 320x240 pixels, but your plate scale is larger, so you may need to use 480p or greater. With a ASI678MC on the ASIAIR, I get the same frame rate when using 480p as I do when using 240p, so I just use 480p.
Anyway, others will chime in. I only play around nowadays with planetary using small refractors and a C6A with horrid optics. Even my 8" Meade is left unused for a few years now since the large heavy OTAs are more unmanageable when one gets old.
BTW, just in case your problem is cause by poor collimation, you might want to check that first. The best tool that I have found nowadays is the tri-Bahtinov masks. If the scope is out of collimation, not all three sets of spikes from that mask will be centered.
If you only have just a simple Bahtinov mask, you can actually check by focusing precisely first, and then rotate the mask's orientation. If you are out of collimation, the diffraction spikes will appear to fall in and out of focus as you rotate the mask -- the tri-Bahtinov simply has three submasks at 120º from one another, so you won't need to rotate the mask. The tri-Bahtinov makes collimating an SCT a breeze, by the way. But, be sure to first read and re-read the collimation instructions at the Celestron web site if you are not familiar with collimating an SCT. There are lots of reading material on the web too.
Chen
