I was wondering if anyone who uses this piece of equipment and has a discerning eye where "good enough" just isn't right, has been able to get proper back focus with this reducer. 56mm from the m48 thread isn't enough. 58.5mm wasn't enoughbut was slightly better. I'm up to 62.5mm for the next night I'm out. I've searched a lot of places and most people's good enough just won't work for me.
Esprit 120 .77x reducer backfocus
I have tried that reducer but was disappointed and gave up. Much better is the Starizona Apex. CS.
I've heard that the Sky-Watcher FR messes up the star shapes, so I didn't bother getting it. I'm very happy with the flattener that comes with it, though, and very pleased with the scope overall.
Ron:
I've heard that the Sky-Watcher FR messes up the star shapes, so I didn't bother getting it. I'm very happy with the flattener that comes with it, though, and very pleased with the scope overall.
It doesn't mess up the star shapes, I have no problem with it besides the apparent curvature at the edges. The apex above that was mentioned has to be the worst device I've seen though and I would rather use a flattener and a full frame than go that route.
I have found the Starizona Apex 0.65x to be brilliant on the Esprit 120 when paired with the APS-C sensor of the ASI2600. I alternate between that, and the native flattener. I think you will see plenty of fine images on AB with both. CS.
Double check me, but doesn't skywatcher say backfocus on that reducer is 95mm?
According to their website, 95mm IS the correct backfocus for the reducer/corrector. And just for completeness, the correct backfocus from the included flattener is 75mm.
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Ron:
According to their website, 95mm IS the correct backfocus for the reducer/corrector. And just for completeness, the correct backfocus from the included flattener is 75mm.
95 including the 40mm adapter with the m48 thread.
Same as the flattener, 75 including the 20mm adapter with the 48mm thread. Which makes 55mm with each. 56 if you are using filters. I've poured over these specifications many times.
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Good luck, Matthew. Looks like you're calculating correctly. We were just reacting to your statement that your back focus was going to be 62.5mm next time, which wouldn't be near the 95mm the manufacturer stated as the back focus from the glass. It wasn't clear that you weren't measuring from the glass.
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From 55mm to 62.5 mm the four corners still showed elongated stars. Some people can live with this I suppose, not worth the extra glass and light diffraction to me if I have to crop. I am not disappointed as I have never liked reducers, they all come with their own set of problems. Native focal length and sampling at .9" is perfect in my sky where I am at 1.8-2.4" seeing.
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