adjusting field flattener spacing. 70mm F6 ED telescope

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realflow100 United States of America
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adjusting field flattener spacing. 70mm F6 ED telescope

#1

Post by realflow100 »


Ive got an orion field flattener and a 70mm F6 ED telescope
but my edges are still just a "little" blurry
I made sure its not tilt. and its not. they are pretty symetrical on both sides if I focus on one corner. its the same at the opposite. same with focusing in the center.
If I manually focus the edges I can get them about 90% sharp but they turn into "lines" then

if I focus in the center of the image the stars at the edges look like enlongated out of focus circles pointing away.


Ive tried adjusting the spacing (All I can do is increase it) but it makes no difference at all. even if I go as far as running out of focusing range to focus my telescope!! The edges dont really improve by increasing the spacing.
They dont get worse either. but they dont get much better. Maybe a couple percent?? Am I still "way off" then?

Do I need a telescope-specific flattener for it to work?
Is my flattener incompatible with my telescope. they are different brands. but the focal ranges are within each other between the flattener and telescope.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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realflow100 United States of America
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#2

Post by realflow100 »


Fixed it! I had to increase the spacing WAYY more than I thought I would! All the way to +25mm!
I think it could still benefit from a little better spacing still. my stars are 90% round at the far corners. but slightly "fuzzy" looking. Not super sharp. I'm not sure if I need slightly more or less spacing. its hard to tell.
i didnt think I needed to increase it SO much for my dslr wow
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#3

Post by realflow100 »


Anyone have any ideas??
I can't tell which way I would need to adjust the spacing to get it to 100%

Very slight tilt doesnt seem to affect the much. (1-2mm of tilt doesnt cause any issues from what i seen) so I dont have to worry about that at all.

but my stars on all 4 corners and edges still look a little on the "soft" side. They are round enough but have a little hint of fuzzyness to them. Not quite razor crisp like the middle.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#4

Post by JayTee »


With your setup being unique to you, your quickest answer will be to experiment and see which direction is the correct one. BTW achieving 100% effectiveness is probably asking too much. The most likely outcome will be you accepting a compromise that still gets you what you want.
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#5

Post by realflow100 »


So just keep fiddling with the spacing and find those last couple millimeters that gets me the closest then?

I think the stars are still enlongated the tiniest bit. so I would need a millimeter or a couple more. to get completely perfect stars out to the edges.

I ordered an adjustable 24-35mm spacer which should get me there. It should be the perfect range to get those last 2-10mm that I need. and precisely.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#6

Post by realflow100 »


I got the adjustable spacer thing but I still can't decide what the best spacing is.
Its always just a little "mushy" in the far edges and corners. even when I think I have it the best spacing I can get it to. (its not particularly sensitive to large adjustments. so I can be 5mm off and it will look almost the same. very hard to tell)

Usually has the appearance of not enough spacing. even when I go somewhat past the point where its sharpest.
my stars dont start "swirling" in a circle around the view. they just become more blobby and blurry looking.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#7

Post by chris_g »


realflow100 wrote: Sun Dec 04, 2022 6:45 am Fixed it! I had to increase the spacing WAYY more than I thought I would! All the way to +25mm!
I have the Orion .85 reducer/flattener. Bought it for my F/7.5 SW 80ED. Considering using it with my WO Z73 F5.9 with an APS-C sensor using a nose piece.

If I read this right, you increased the working distance from 55mm to 80mm. Good to know.

Thanks for info.

Clear Skies,
Chris
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#8

Post by JayTee »


Are you using a Bahtinov mask or some other focusing aid to bring the image into focus? If so, then at some point we have to believe that you have reached the operating limits of the objective lens.
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
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∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#9

Post by realflow100 »


Ive used a focusing mask on stars as well as a point source on an a random far away object like a cell tower or powerline insulator type object.

if I can focus on the corner or center and the middl;e still line up in the center is that as good as its going to get?
Like I can focus on a corner and it will still be in focus in the middle. and vice versa?
its like 95% sharp on the corners with a tiny bit of fuzzyness. maybe some residual curvature the flattener can't quite correct for? since its a generic one.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#10

Post by realflow100 »


My adapter arrived!!!!!
M48 to M54 male to male threaded adapter. I can now directly attach my field flattener to my telescopes focuser without the thumbscrew slot thing. now its far easier to adjust the spacing with the adjustable extension thing!
And no tilt caused by the thumbscrew things.
however Im still not quite sure what my spacing should really be.
Ive been fiddling with it and it and closest ive gotten is to the point where it looks 95% the same as the middle I can't quite get that last 5% of crispness to the corners.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#11

Post by chris_g »


realflow100 wrote: Thu Dec 15, 2022 2:52 pm Ive been fiddling with it and it and closest ive gotten is to the point where it looks 95% the same as the middle I can't quite get that last 5% of crispness to the corners.
95%, I'd call that good and be done with it. You'll end up cropping that much off any way to remove rough edges caused by the slight rotation in each image during the stacking process.
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
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Re: adjusting field flattener spacing. 70mm F6 ED telescope

#12

Post by AstroBee »


I agree with everyone else. Unless you have really high-end optics and a flattened that is dedicated to that exact scope, it's unlikely you will get better than 95% perfect. I'm happy with around 80% and just cropping that 15% of the edges out. But since you have that variable spacer on order, it should be easy to figure out if you've reached your optics limits.
Greg M.~ "Ad Astra per Aspera"
Scopes: Celestron EdgeHD14", Explore Scientific ED152CF & ED127 APO's, StellarVue SV70T, Classic Orange-Tube C-8, Lunt 80mm Ha double-stack solar scope.
Mounts: Astro-Physics Mach One, iOptron CEM70EC Mount, iOptron ZEQ25 Mount.
Cameras: ZWO ASI2600mm Pro, ZWO 2600MC Pro, ZWO ASI1600mm
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Eyepieces: 27mm TeleVue Panoptic, 4mm TeleVue Radian, Explore Scientific 82° 30mm, 6.7mm , Baader 13mm Hyperion, Explore Scientific 70° 10mm, 15mm, 20mm, Meade 8.8mm UWA
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