I know it might be a stupid dilemma but lately i was thinking about changing my camera, was torn between two possible choices, the ZWO2600 or 533, both mounted on an Askar 91F, as regards the 533 i would have taken the 0.75x focal reducer which brings it to f/5 with a focal length of about 455mm but the thing that interested me most was also the purchase of Pixinsight, so is it objectively better to first take the 2600 and then in the future wait to buy Pixinsight and the reducer, or directly take the 533 with Pixinsight and reducer?
Setup changes
If you don't mind the loss of scale with the reducer then the most rewarding path would be ASI533 + reducer + PixInsight. PI alone is worth the money and if you need the higher resolution you can always use the refractor without reducer.
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PixInsight and no reducer gets my vote.
In my case I had two choices. Naked as the telescope was, or a 0.8x FR/FF. Now there are other choices for my particular telescope. But I’m happy with the reduction from 915mm FL F7 to 728mm FL at F5.8, buying a telescope advertised at 915mm, but winding up at 728mm was a gip due to ad writers lying about reality.
FR is dependent on how your images show. In my telescope, with my ASI2600MC Pro camera, native had undesirable Vignetting at the corners. So the accepted answer from other users was to get the 0.8 FR/FF sold for my particular telescope. Then I went to great pains to make my imaging train rigidly screwed together. I got it at 54.9mm back spacing and tried it. It was not good out to the corners yet. I was disappointed after all my painstaking efforts.
I removed a 20mm spacer and replaced it with a 16.5mm and got my stars round over the entire FOV. Nirvana. And my imaging train is solid as a rock. The only flexure is in the focuser itself which cannot be tightened or it won’t move in and out to focus. So I rely on my software finding the best focus over the nights imaging. Works for me.
The goal is to attain images you are happy with. regardless of what the math sez. Because the math can only be as accurate as the variables allow. Seeing and clouds trumps all math.
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I’m with Andrea on this. Purchasing and taking the time to learn PI will be more rewarding than the bigger sensor of the 2600. The 533 is also a great sensor and with the reducer it still gives you a decent pixel scale and a decent field of view.
Also maybe have a play around with this field of view tool if you haven’t already to see how subjects that interest you might fit into the different combinations of scope/reducer/camera.
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