cheap 70mm refractor telescope F5.1 testing again

Discuss your refractor type scopes here.
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realflow100 United States of America
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cheap 70mm refractor telescope F5.1 testing again

#1

Post by realflow100 »


still messing with this thing trying to get the sharpest image possible. and least amount of blurry edges as i can.
this seems to be the best result ive got so far.
I havent got a good clear night sky lately so havent been able to get any stars.


Image
Image
Image
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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Graeme1858 Great Britain
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Re: cheap 70mm refractor telescope F5.1 testing again

#2

Post by Graeme1858 »


Focus looks good. There's some nasty paint chip dints on the front of that Honda!

Regards

Graeme
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Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
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realflow100 United States of America
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Re: cheap 70mm refractor telescope F5.1 testing again

#3

Post by realflow100 »


I'm trying to get the edges as sharp as possible but i think ive reached diminishing returns at this point fiddling with the scope.
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: cheap 70mm refractor telescope F5.1 testing again

#4

Post by realflow100 »


After a ton of fiddling Ive spaced the lens one last time with the very thin spacing and did a star test at 120x magnification.
I see faint rings around a star now!
And the rings are centered too. no more coma!
I also got a brand new 90 degree star diagonal of respectable quality. and a decent 2x barlow as well!
based on what i'm reading i should only be able to see 1 or 2 rings in my small 70mm refractor telescope.
but i see at least 3 or 4 rings decreasing in brightness away from the star.
inside focus and outside focus look similar when in a larger amount. but slightly out of focus looks wrong. looks more one-sided
but I need to wait for a clearer night. there was only a short break in the clouds just after dark. then it was completely clouded over the rest of the night.
Tried looking at jupiter but it was just a light brown/tan/yellowish ball/sphere.
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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John Baars Netherlands
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Re: cheap 70mm refractor telescope F5.1 testing again

#5

Post by John Baars »


realflow100 wrote: Wed Aug 18, 2021 11:04 am After a ton of fiddling Ive spaced the lens one last time with the very thin spacing and did a star test at 120x magnification.
I see faint rings around a star now!
And the rings are centered too. no more coma!
I also got a brand new 90 degree star diagonal of respectable quality. and a decent 2x barlow as well!
based on what i'm reading i should only be able to see 1 or 2 rings in my small 70mm refractor telescope.
but i see at least 3 or 4 rings decreasing in brightness away from the star.
inside focus and outside focus look similar when in a larger amount. but slightly out of focus looks wrong. looks more one-sided
but I need to wait for a clearer night. there was only a short break in the clouds just after dark. then it was completely clouded over the rest of the night.
Tried looking at jupiter but it was just a light brown/tan/yellowish ball/sphere.
It is good you see faint rings around a star now. I suppose the better diagonal makes a lot of difference.
It is hard to make out which of the three changes you made is responsible for the whole new situation. To see the effect of a change you 'd better do one at the time. Which is still possible of course: look at the star-pattern if you remove the diagonal and the barlow. That will show you the effect of the fiddling with the lens only. In general multiple visible rings means more spherical aberration present.
Since you like experimenting with optics you should try Aberrator http://aberrator.astronomy.net/html/mdibeta.html A program in which you can vary with aberrations at will, without having to test it on your own equipment.
Refractors in frequency of use : *SW Evostar 120ED F/7.5 (all round ), * Vixen 102ED F/9 (vintage), both on Vixen GPDX.
GrabnGo on Alt/AZ : *SW Startravel 102 F/5 refractor( widefield, Sun, push-to), *OMC140 Maksutov F/14.3 ( planets).
Most used Eyepieces: *Panoptic 24, *Morpheus 14, *Leica ASPH zoom, *Zeiss barlow, *Pentax XO5.
Commonly used bino's : *Jena 10X50 , * Canon 10X30 IS, *Swarovski Habicht 7X42, * Celestron 15X70, *Kasai 2.3X40
Rijswijk Public Observatory: * Astro-Physics Starfire 130 f/8, * 6 inch Newton, * C9.25, * Meade 14 inch LX600 ACF, *Lunt.
Amateur astronomer since 1970.
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Re: cheap 70mm refractor telescope F5.1 testing again

#6

Post by realflow100 »


its just much harder to see without the diagonal and barlow. but it looks the same
I recorded a video of the moon with my cheap 70$ 70mm refractor telescope after getting the spacing just right with the star test so its as little under or over correction as i can get it.
used eyepiece and phone. Slightly over the maximu theoretical magnification too. but its not even that bad. 6mm eyepiece +2x barlow and an empty barlow tube to use as an extension for even more magnification. video resolution is 1280x720. phone quality is not the greatest. but you can still see very small crators!
https://vimeo.com/589204355
check it out if you want!
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: cheap 70mm refractor telescope F5.1 testing again

#7

Post by Graeme1858 »


That's a great video for a $70 refractor and a phone camera RF!

Regards

Graeme
______________________________________________
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.

https://www.averywayobservatory.co.uk/
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Re: cheap 70mm refractor telescope F5.1 testing again

#8

Post by realflow100 »


Does the resolution there and details appear to match the typical quality of a cheap 70$ 70mm refractor scope?

Or do you think with a better phone even more details could be seen at even higher magnifications?
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: cheap 70mm refractor telescope F5.1 testing again

#9

Post by notFritzArgelander »


realflow100 wrote: Thu Aug 19, 2021 10:14 pm Does the resolution there and details appear to match the typical quality of a cheap 70$ 70mm refractor scope?

Or do you think with a better phone even more details could be seen at even higher magnifications?
I think you're doing very well with what you've been working with. The images are mostly limited by atmospheric effects. I don't think you will get more out of this scope with higher magnification, that's not the issue. If anything you've maxed out. Stacking best still frames from a movie would help. Look into processing a movie of a single target (don't move the scope) with some processing software like Registax.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: cheap 70mm refractor telescope F5.1 testing again

#10

Post by realflow100 »


The moon moves too fast unless I used a lower magnification!
I think I'd need to track the moon somehow. if i wanted to try move stacking.
Also I only got this result by heavily modifying the scope and changing the lens element spacing on it to minimize under or over correction as much as possible (causes a significant difference in image sharpness at high magnifications)
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: cheap 70mm refractor telescope F5.1 testing again

#11

Post by realflow100 »


I could see the bands on jupiter quite easily Almost even some detail in the bands. I see 2-3 bands for sure. just looks like a lot of atmosphere turbulence. i know my scope has more resolution. so i'm limited by atmosphere even with my small 70mm refractor. more than the scopes resolution. for planets.
Is that a good thing in terms of the scopes ability??
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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