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redo classic shootout edmund 4inch vs criterion RV6

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#1 highfnum

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Posted 04 February 2020 - 09:07 AM

I was going to post in "what did you see with your classic " but its large enough to be alone

 

1 both scopes are in great shape 

2) both scopes mounted on lxd55 mount for better track

3) seeing was very very good and moon was high up near zenith

rv6 had 2x barlow 

ed4 some shots with 2x barlow and some not

 

 

rv6 first 

Capture 2_3_2020 7_02_42 PMrv6.jpg

Capture 2_3_2020 7_03_16 PMrv6.jpg

Capture 2_3_2020 7_04_33 PMrv6.jpg

Capture 2_3_2020 7_05_03 PMrv6.jpg

Capture 2_3_2020 7_08_15 PMrv6.jpg

 


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#2 highfnum

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Posted 04 February 2020 - 09:09 AM

RV6 di pick up rille  

finally clavius 

INHO best shot of moon  with my RV6

Capture 2_3_2020 7_11_37 PMrv6.jpg


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#3 highfnum

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Posted 04 February 2020 - 09:14 AM

ok ed4 

Capture 2_3_2020 8_39_45 PMed4p.jpg

Capture 2_3_2020 8_41_06 PMed4p.jpg

Capture 2_3_2020 8_42_27 PMed4.jpg

Capture 2_3_2020 8_43_30 PMed4.jpg

Capture 2_3_2020 8_53_00 PMed4.jpg

 

 


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#4 highfnum

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Posted 04 February 2020 - 09:16 AM

second batch

Capture 2_3_2020 8_55_06 PMed4.jpg

Capture 2_3_2020 8_57_08 PMed4.jpg

Capture 2_3_2020 8_58_01 PMed4.jpg

Capture 2_3_2020 8_59_32 PMed4.jpg


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#5 highfnum

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Posted 04 February 2020 - 09:20 AM

so both scopes did a great job

 

however RV6 does show more detail

 

IMHO it looks like I picked up some of rille with ED4 - if correct that's a new record for me for scope size

ed4 had more trouble with smaller circular features

 

some folks in past have said that a 4 inch refractor has same capability as 6 inch reflector

 

if its a good 6 inch - I say no


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#6 astroneil

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Posted 04 February 2020 - 09:53 AM

Most interesting. Thanks for posting.

 

Neil.



#7 Garyth64

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Posted 04 February 2020 - 09:57 AM

I agree.  I have a 6" f/10 newt that I made back in 66.  It is excellent.   

 

Those are some nice sets of photos.


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#8 2696

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Posted 04 February 2020 - 11:14 AM

Very nice photos.

#9 Chuck Hards

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Posted 04 February 2020 - 11:29 AM

Many times I've been out with a 3-inch or 4-inch refractor of very high quality, and wished I had my 6-inch Newtonian handy.

 

I have never been out with the 6-inch Newt and wished that the 4-inch refractor was set up instead.

 

There is no substitute for aperture.


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#10 clamchip

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Posted 04 February 2020 - 12:21 PM

Two heavyweights the RV6 and the Edmund 4 inch f/15.

100% grade A classic!

 

Robert


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#11 Kasmos

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Posted 04 February 2020 - 02:41 PM

It's not clear to me which ones are which. Are the doubles in some of the post from the same scope?



#12 highfnum

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Posted 04 February 2020 - 03:06 PM

first batch rv6

second batch ed4

if you hover over pic it has date stamp and either  rv6 or ed4 at end

this series

rv6 ed4  pics only here

i did some pics with c925 and gso cc8 in other threads 


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#13 Bonco2

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Posted 04 February 2020 - 04:13 PM

Very interesting comparison. The craters in Plato were clearly defined in the RV6 not so in the 4 inch.

Good job!  Bill  



#14 Terra Nova

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Posted 04 February 2020 - 05:12 PM

Very interesting comparison. The craters in Plato were clearly defined in the RV6 not so in the 4 inch.

Good job!  Bill  

 

That’s for sure! I did a little cropping, scaling, rotation, and image enhancement and you can see a definite difference in resolution detail (RV6 image on the right).

Attached Thumbnails

  • 99CE532C-C0E1-4C1E-8A94-F799079D6611.jpeg

Edited by Terra Nova, 04 February 2020 - 05:16 PM.

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#15 DAVIDG

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Posted 04 February 2020 - 05:17 PM

That’s for sure! I did a little cropping, scaling, rotation, and image enhancement and you can see a definite difference in resolution detail (RV6 image on the right).

 Nice visual proof that the Law of Aperture vs Resolution is still working.

 

               - Dave 


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#16 rcwolpert

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Posted 04 February 2020 - 05:25 PM

Very nice comparison! The RV-6 was a truly exceptional scope for the money. Wish I still had mine.


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#17 DAVIDG

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Posted 04 February 2020 - 05:44 PM

It would be interesting to know the wavefront on the RV-6 and 4" Edmund. I must have tested at least 50 RV-6 mirrors over the years and they all have been consistently under corrected. So with the RV-6 having  a 50" focal length they are just over 1/4 wave. Knowing what this one is and also the 4" refractor would give a better idea of what the level of  aperture vs optical quality are contributing to the difference in resolution.

   We hear that a 6" reflector has about the same resolution as a 4" refractor. The Laws  of Optics states that should not be and this examples shows proof of that.  So is this coming from more the fact that many 6" reflectors just have poorly figured optics?

 

               - Dave 


Edited by DAVIDG, 04 February 2020 - 05:48 PM.

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#18 Augustus

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Posted 04 February 2020 - 07:22 PM

It would be interesting to know the wavefront on the RV-6 and 4" Edmund. I must have tested at least 50 RV-6 mirrors over the years and they all have been consistently under corrected. So with the RV-6 having  a 50" focal length they are just over 1/4 wave. Knowing what this one is and also the 4" refractor would give a better idea of what the level of  aperture vs optical quality are contributing to the difference in resolution.

   We hear that a 6" reflector has about the same resolution as a 4" refractor. The Laws  of Optics states that should not be and this examples shows proof of that.  So is this coming from more the fact that many 6" reflectors just have poorly figured optics?

 

               - Dave 

I think that if you gathered up optically "great" scopes you'd be really surprised that most of them are probably barely 1/4 wave. 


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#19 Terra Nova

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Posted 04 February 2020 - 08:39 PM

Note that you can ‘see’ the three smaller craters on the floor of Plato in the image made with the 4” refractor (you can just barely make them out), but they are certainly not plainly visible as they are in the RV6 image.

Attached Thumbnails

  • B1FC2CD6-CC8F-4F56-9EC3-B73B5F86AA27.jpeg

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#20 clamchip

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Posted 04 February 2020 - 08:55 PM

The RV6 gathers over twice the light of the Edmund.

RV6 resolves to .7 arc sec, the Edmund 1 arc sec.

 

Both scopes are really excellent and I own both, and

observe with them regularly but as good as the Edmund

is it's no match for a excellent 6 inch f/8.

 

Robert


Edited by clamchip, 04 February 2020 - 08:56 PM.

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#21 starman876

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Posted 04 February 2020 - 09:03 PM

awesome comparison of the two scopes.    Makes one want to get the rv6 out of mothballs.


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#22 photiost

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Posted 04 February 2020 - 10:05 PM

Yes there is no substitute for aperture, and the RV8 mirrors are just as good !! 



#23 ccwemyss

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Posted 04 February 2020 - 10:17 PM

If anyone is looking for one, there's that RV8 on the observatory pedestal mount, near NY, that has been for sale at $350 on CL for months. 

 

Chip W.


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#24 highfnum

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Posted 05 February 2020 - 07:48 AM

im surprised no commented on rille in alpine  valley 

 

 

the rille is .27arc sec and yet can be picked up in a small scope 

its a fact that the shape of what you are looking at determines if you can see it

i will refer you to pages 14-16 of following book

 

ill quote on page  14 "we also consider that we can see see a black line on a white background when its width is just 1/10

of the resolving power"

 

i beleive i showed this also with above photos

 

highphoto.jpg

 

 


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#25 steve t

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Posted 05 February 2020 - 08:12 AM

Thanks for the images. It's an interesting comparison between the two scopes and different apertures.

 

Steve T.




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