hi,
I recently purchased the reducer for my Esprit 120.
After some researches i found out that a backfocus of 60mm instead of 55mm gives a flatter image. Trying out both with the Asiair, i figured out that the focuser stays in the region of 1000 with 55mm backfocus whereas using 60mm it travels towards 7000 which is somewhere about half the travel of the focuser.
Can anyone share his experience with that combo?
thx
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Is this a matched SW reducer?
I only have the matched 120ED flattener which works at 55mm on the nose
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The backfocus of the total 0.77x reducer is 95mm. (55mm from the top of the start of the M-48 male thread). If you put a filter, which can be placed inside the reducer itself, you already know that 1/3 of the thickness must be added, in the optolong 0.6. Therefore the total with filter would be 55.6 mm.
I have never used 60mm |
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If you're using the flattener/reducer that comes with the Esprit 120ED, you'll need a back focus of 95mm. For the flattener only, 75mm. This is measured from the bottom of the threads of the flattener/reducer to the sensor of the camera. See pages 8 thru 12 of the user's manual for your scope.
Patrick
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I have both the flattener and the esprit .77 reducer for my Esprit 120. The additional back focus needed from the dedicated spacer that is suppled with the reducer and flattener is 55mm on both systems. Yes the focus position changes. In my case from 16000 steps to around 6000. This of course is dependent on the step size of your focus motor.
note: because I shoot mono and my chroma filters are 3mm thick I add 1mm to my back focus for a total of 56.
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I have both the supplied flattener and the additional matched 0.77x reducer/flattener. The images produced by the reducer are not that flat, especially around the edges. I used 55mm backfocus for both, but I will try it at 60 to see if there is any improved field flatness. Thanks!
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hi,
I recently purchased the reducer for my Esprit 120.
After some researches i found out that a backfocus of 60mm instead of 55mm gives a flatter image. Trying out both with the Asiair, i figured out that the focuser stays in the region of 1000 with 55mm backfocus whereas using 60mm it travels towards 7000 which is somewhere about half the travel of the focuser.
Can anyone share his experience with that combo?
thx
I couldn't get a reasonably flat image with 55mm-62.5mm. And before anyone chimes in  the 40mm M78-M48 adapter is installed.
Even at a total of 102.5 (40+62.5) the stars are horrendous. Must have gotten one from the its 5 o'clock somewhere batch.
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Matthew Proulx:
hi,
I recently purchased the reducer for my Esprit 120.
After some researches i found out that a backfocus of 60mm instead of 55mm gives a flatter image. Trying out both with the Asiair, i figured out that the focuser stays in the region of 1000 with 55mm backfocus whereas using 60mm it travels towards 7000 which is somewhere about half the travel of the focuser.
Can anyone share his experience with that combo?
thx
I couldn't get a reasonably flat image with 55mm-62.5mm. And before anyone chimes in the 40mm M78-M48 adapter is installed.
Even at a total of 102.5 (40+62.5) the stars are horrendous. Must have gotten one from the its 5 o'clock somewhere batch.
Looks good to me.
i bought one myself but don’t have any finished photos yet.
From the few frames i have taken with it it looks like i have a bit of comet like stars in one corner but even taks don’t produce perfect stars when reduced and pictures taken with newtons have spikes while also having (even the expensive ones) problems with star shapes if you don’t collimate them regularly.
the esprit 120 with its flattener and the flattener reducer is pretty hard to beat if you consider the price, mobility and versatility of the scope.
btw i am using mine at 55.5 mm, same as the 1.0 flattener.
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Andi:
Matthew Proulx:
hi,
I recently purchased the reducer for my Esprit 120.
After some researches i found out that a backfocus of 60mm instead of 55mm gives a flatter image. Trying out both with the Asiair, i figured out that the focuser stays in the region of 1000 with 55mm backfocus whereas using 60mm it travels towards 7000 which is somewhere about half the travel of the focuser.
Can anyone share his experience with that combo?
thx
I couldn't get a reasonably flat image with 55mm-62.5mm. And before anyone chimes in the 40mm M78-M48 adapter is installed.
Even at a total of 102.5 (40+62.5) the stars are horrendous. Must have gotten one from the its 5 o'clock somewhere batch.
Looks good to me.
i bought one myself but don’t have any finished photos yet.
From the few frames i have taken with it it looks like i have a bit of comet like stars in one corner but even taks don’t produce perfect stars when reduced and pictures taken with newtons have spikes while also having (even the expensive ones) problems with star shapes if you don’t collimate them regularly.
the esprit 120 with its flattener and the flattener reducer is pretty hard to beat if you consider the price, mobility and versatility of the scope.
btw i am using mine at 55.5 mm, same as the 1.0 flattener.
Unacceptable to me. The only reason to use a reducer/"flattener" is to increase the FOV. At .77x you don't get enough FOV for the abberation it introduces here, when you crop it you're basically at 1.0x again or worse. I had a TAK120 with the TOA35 reducer 2 years ago and there was absolutely no curvature. You should be able to cover a full frame at least with no curvature whatsoever.
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Hi guys,
seems like, im not the only one having funky stars, using the reducer.
tomorrow i will get some spacers (1mm and 0,5mm) and i will do some trial and error from 55mm all the way up to 60mm.
i watched locamaticos YT video about the reducer and in the comments, he wrote that 59,5mm gave him good shaped stars.
Lets see, will give an update eventually
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I think you have the same problem I had which is a dud reducer. I got all the way out to 62mm of back focus and couldn't get round stars. The focuser would stop around 1000 steps. I finally decided to just purchase a new reducer and I now get perfect (to my eyes) stars across the field with 55.6mm of back focus with filters. Now it's in focus around 7200.
If you have the ability to return or RMA your reducer and get a replacement, I'd say give that a try!
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Thank you for your advice.
Since i bought it recently, i will definitely change it, if the spacers won’t help.
what bothers me is, that the stars are egg shaped not only in the corners but everywhere in the frame. So, its not that typical backfocus issue (too far/too close) rather „vertical-egg-stars“ even in the middle, not changing the orientation or shape.
will give an update with the final solition.
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hi,
I recently purchased the reducer for my Esprit 120.
After some researches i found out that a backfocus of 60mm instead of 55mm gives a flatter image. Trying out both with the Asiair, i figured out that the focuser stays in the region of 1000 with 55mm backfocus whereas using 60mm it travels towards 7000 which is somewhere about half the travel of the focuser.
Can anyone share his experience with that combo?
thx
I experimented with this a lot, I bought one as soon as they were available and went through three of them while figuring it out. - 60mm is honestly tons better than the 55mm suggested by the manufacturer!
Stick to your guns mate, 55 is a waste of time with the 0.77x reducer/flattener imo, keep that 60 and enjoy!
CS
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Hi Luke!
thank you so much, your video really helps alot! huge fan of your channel!
Tried 60mm yesterday, still no round stars 
at native focal lenght though i get perfectly round stars.
Will talk with my dealer, maybe he can it or even give a replacement.
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Not the first time I hear complaints of the SW reducer.
I have a 0,75 reducer from TS Optics that predates the existence of the SW one.
It's this one although it since was updated and is now 0,74x.
About the back focus, I also would suggest not to pin down on the 55mm, look at the image and let it dictate what to do.
Good luck.
CS
Miguel
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hi,
I recently purchased the reducer for my Esprit 120.
After some researches i found out that a backfocus of 60mm instead of 55mm gives a flatter image. Trying out both with the Asiair, i figured out that the focuser stays in the region of 1000 with 55mm backfocus whereas using 60mm it travels towards 7000 which is somewhere about half the travel of the focuser.
Can anyone share his experience with that combo?
thx
I had to increase my back focus for my Esprit 120 when using the .77x reducer/flattener, at 55.6mm (.6 added for filters) I had elongated stars in the corners going outwards (APS-C format, ASI2600MC) . I changed out a ZWO spacer, adding 4.5mm back focus for a total of 60.1mm and that resolved it - so yes, I had a similar experience. When just using the included flatter, corners were fine at 55.6mm back focus.
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At 860mm fl I've never installed the reducer. Can't seem to give up the FL I bought. Pretty wide as it is. Not sure what the objective is.
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0.00
1.51
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5.70
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0.00
6.06
3.81
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0.00
0.00
2.10
