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Edmund 6" f/6 Newtonian: "First Look"

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#1 Clive Gibbons

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Posted 28 September 2005 - 10:03 AM

Last night was "first light" thru the ol' Edmund 6" f/6.
Taking the scope outside reminded me why I haven't bothered using larger, fork mounted instruments in recent years... they're heavy and cumbersome! This was no grab 'n' go system. Ow!, my aching back!!
I left the system outside to cool down for a while and returned just as it was getting dark.
First target was Delta Cygni. This star is a fairly challenging double for scopes in the 3 to 4" range.
2.9 and 6.3 magnitude components, with a 2.5" separation.
To punch up the powers a bit, a Goodwin Barlow was used at the 3x setting. This extended the scope's 910mm focal length to approx 2730mm. A quick look at Delta using a 16mm Plossl (171x) showed the faint companion without any difficulty. Collimation seemed spot-on. Pushing back and forth through focus revealed no zones or figure defects. In fact, the view of Delta was virtually "refractor like". Clean, round Airy disks and a couple of evenly illuminated diffraction rings. The four razor-thin arms of the secondary support hardly appeared to affect the diffraction image.
Out came the 16mm ocular and in went a 12.5mm Ortho. At 218x, the double looked even more distinct and still extremely crisp. It was obvious that the ol' Edmund's optics left little to be desired.
Next, I swung the scope down to Altair and tried a 35mm ocular with no Barlow. The star was a dazzling point at 26x, with four long, faint, diffraction spikes. Classic Newtonian view, if there ever was one.
Not far from Altair, was another double star: Pi Aquilae. It's 6th magnitude components are 1.4 arc sec apart.
Back to 171x and the double was easily split. Two cleanly resolved disks, one a bit fainter than the other. No spikes and just a faintly visible diffraction ring. The image was so clean, it was hard to believe this was a Newt with a 33% obstruction and traditional secondary support.
By now, the sky was very dark and it was time to peek at a deep sky object. M13 in Hercules was still visible in the north-west. With the 16mm ocular at 171x, the cluster was well resolved. The view looked comparable to what I'd seen with my ED100 refractor at a similar magnification. The Edmund's image was perhaps a bit brighter, but not greatly so. Nice!
Finally, a tougher double star was targetted for a test of the scope's optics. 16 Vulpeculae was swung into view. This star has components of 5.9 and 6.3 magnitude, separated by only 0.8 arc sec. The seeing was quite steady (approx 7 out of 10), so it seemed like a good enough night to try it. No problem. At 171x, the star was distinctly figure-8 shaped. Bumping the power to 218x revealed the two stars almost distinctly resolved, but not quite. They were slightly overlapping. At 268x (10.2mm Ortho), the view was good but no better than what 218x showed. Seeing was degrading a bit and the scope's old focuser made fine tuning the image a bit of a chore.
The observing session was brief, but sufficient to tally up the Edmund 6" f/6's strengths and weaknesses:
Pluses:
1) Amazingly good optics.
2) Rock-solid fork mount and tripod.
3) Smooth and accurate A/C motor drive. Dec. slo-motion also worked well.
4) Viewing positions easy to access, thanks to fork mount.

Minuses:
1) Rather cumbersome to set-up and break down.
2) Right-angle rinder could be better. Thin x-hair almost invisible at night.
3) Rack and pinion focuser a bit "clunky". Regreasing might help.

All-in-all, a neat "blast from the past" scope! :cool:


Clive.

Attached Thumbnails

  • 619255-Edmund6.JPG


#2 Clive Gibbons

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Posted 28 September 2005 - 10:15 AM

Down the front end...

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  • 619273-EdmundTube.jpg


#3 trainsktg

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Posted 28 September 2005 - 05:25 PM

Nice. Where did you aquire this gem? It 'oozes' quality. I haven't seen similar since looking at old Edmund Catalogs as a kid. Is that mount cast iron?

Keith

#4 Clive Gibbons

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Posted 28 September 2005 - 07:13 PM

Nice. Where did you aquire this gem? It 'oozes' quality. I haven't seen similar since looking at old Edmund Catalogs as a kid. Is that mount cast iron?

Keith


Thanks, Keith!
I bought it from a dealer for $250 (Canadian).
The scope is well designed. The OTA consists of 2 main modules with the phenolic tube in between. The primary mirror and cell "module" is affixed by three screws to the bottom of the tube. The secondary mirror, holder and support "module" is affixed by two screws at the top of the tube. After cleaning the optics and reinstalling everything, the secondary mirror required no recollimation and the primary needed just a few tweaks. Everything was aligned in less than a minute.
The fork mount and tripod are made of cast aluminum.
If anyone comes across one of these for a reasonable price,
GRAB IT! :jump:

#5 Kenny

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Posted 29 September 2005 - 07:37 AM

Nice. Where did you aquire this gem? It 'oozes' quality. I haven't seen similar since looking at old Edmund Catalogs as a kid. Is that mount cast iron?

Keith


Thanks, Keith!
I bought it from a dealer for $250 (Canadian).


Wow, that's alot less than I remember it being listed for. Did they drop the price first and then you got it, or are you that good of a haggler?

BTW, the very partial image of you in the primary mirror is in conflict with the image of you in your current avatar - which leads me to believe that you are not quite as "square-headed" and that your avatar is fraudulant! This can greatly affect your credibility - soon people will doubt that you really live in the Oort Cloud! :grin:

Ken.

#6 Clive Gibbons

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Posted 29 September 2005 - 08:13 AM

Nice. Where did you aquire this gem? It 'oozes' quality. I haven't seen similar since looking at old Edmund Catalogs as a kid. Is that mount cast iron?

Keith


Thanks, Keith!
I bought it from a dealer for $250 (Canadian).


Wow, that's alot less than I remember it being listed for. Did they drop the price first and then you got it, or are you that good of a haggler?

BTW, the very partial image of you in the primary mirror is in conflict with the image of you in your current avatar - which leads me to believe that you are not quite as "square-headed" and that your avatar is fraudulant! This can greatly affect your credibility - soon people will doubt that you really live in the Oort Cloud! :grin:

Ken.


Hey, Ken.
The dealer was originally selling the scope for $350, but dropped the price since nobody was biting. No haggling involved on my part! It even came with a couple of decent eyepieces (unfortunately, not RKEs).

BTW, that partial head you see reflected in the primary mirror isn't me. I'm hopeless at manipulating the teensy buttons on a digital camera, so the kind-hearted human next door volunteered to take the pictures. :grin:

#7 Ken

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Posted 29 September 2005 - 12:54 PM

Excellent Clive,

I've had my Red Tubed Edmund since it was first introduced. Bought one of the very first ones off the Barrington NJ floor. The performance is exactly as I would have expected. The neat thing is, wait until you set it up in public at a Star Party. The bright red tube and Aluminum mount just grabs attention. It was truly a premium telescope then and still is. To protect the rather fragile phenolic, I built this case back when I was still a teenager. Even that has lasted all this time, through two hurricanes and a tornado and half a dozen or more moves. Concerning collimation, you should be set for life short of an explosion, once collimated and locked that mirror cell is so over engineeered it will out last all of us.

Attached Thumbnails

  • 620950-Minolta X50 Edmund in case 002 (Small).jpg


#8 Ken

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Posted 29 September 2005 - 01:05 PM

By the way, just a suggestion, when you slide the OTA into the Rings Assembly the Tube lock knobs generally go topside. The mount should have flats machined on the tube "rings, on the side where the knobs are so that you can tap it to install other equipment. Also never let the tension on the Declination circle lock knob get too low, if the tube is off balance the tube will rotate down and the phenolic will crack on the bottom of the yoke. I had only had her a few months when I did this back over the winter of '78. Fortunately Edmund replaced my tube and I've been paranoid about that ever since.

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  • 620969-Edmunt Fork Mount005 (Small).jpg


#9 Clive Gibbons

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Posted 29 September 2005 - 01:07 PM

Excellent Clive,

I've had my Red Tubed Edmund since it was first introduced. Bought one of the very first ones off the Barrington NJ floor. The performance is exactly as I would have expected. The neat thing is, wait until you set it up in public at a Star Party. The bright red tube and Aluminum mount just grabs attention. It was truly a premium telescope then and still is. To protect the rather fragile phenolic, I built this case back when I was still a teenager. Even that has lasted all this time, through two hurricanes and a tornado and half a dozen or more moves. Concerning collimation, you should be set for life short of an explosion, once collimated and locked that mirror cell is so over engineeered it will out last all of us.


Cheers Ken #2!
I agree about the mirror cells and collimation. No worries, there!

Nice case you built, too!!

Take care,

Clive.

#10 Clive Gibbons

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Posted 29 September 2005 - 01:12 PM

By the way, just a suggestion, when you slide the OTA into the Rings Assembly the Tube lock knobs generally go topside. The mount should have flats machined on the tube "rings, on the side where the knobs are so that you can tap it to install other equipment. Also never let the tension on the Declination circle lock knob get too low, if the tube is off balance the tube will rotate down and the phenolic will crack on the bottom of the yoke. I had only had her a few months when I did this back over the winter of '78. Fortunately Edmund replaced my tube and I've been paranoid about that ever since.


Thank you Sir, for all the great advice!
Will follow your suggestions...

Clear skies,


Clive.

#11 Kenny

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Posted 30 September 2005 - 05:31 AM

Nice. Where did you aquire this gem? It 'oozes' quality. I haven't seen similar since looking at old Edmund Catalogs as a kid. Is that mount cast iron?

Keith


Thanks, Keith!
I bought it from a dealer for $250 (Canadian).


Wow, that's alot less than I remember it being listed for. Did they drop the price first and then you got it, or are you that good of a haggler?

BTW, the very partial image of you in the primary mirror is in conflict with the image of you in your current avatar - which leads me to believe that you are not quite as "square-headed" and that your avatar is fraudulant! This can greatly affect your credibility - soon people will doubt that you really live in the Oort Cloud! :grin:

Ken.


Hey, Ken.
The dealer was originally selling the scope for $350, but dropped the price since nobody was biting. No haggling involved on my part! It even came with a couple of decent eyepieces (unfortunately, not RKEs).


You got a great deal. I saw that scope in the store and it is nice. BTW, the same store is selling a used 15mm RKE. I'm not sure if I like the asking price though.

Ken.

#12 Guest_**DONOTDELETE**_*

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Posted 30 September 2005 - 09:49 AM

Where is this store?

#13 Kenny

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Posted 01 October 2005 - 03:48 AM

Where is this store?


Kendrick's - in Toronto, Canada. They do ship internationally though so you should check out their website.

Ken.


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