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1988 AP 6-inch APO - returning to me...

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#1 Cotts

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Posted 18 May 2021 - 08:01 AM

About 8 or 9 years ago I acquired this scope, put a beauty Feathertouch focuser on it.  I used the scope for about 3 years then sold it to a guy in my club.  It's optics are superb, every inch an AP....there wasn't a thing wrong with it.

 

He hasn't even unpacked it!  It has been sitting for 6 years!

 

I knew this and, needing a complimentary scope to my new 20-inch Dob, asked him if he would sell it back to me...  He agreed, same price....

 

I'll have it in a few weeks....I've asked him to unpack it and check everything.... 6 years in a box.....

 

I'll put it on my new EQ6 mount which I am picking up today.....Primary use will be double star viewing as well as video lucky imaging and maybe some DSLR imaging.....public outreach when it returns to us....

 

Dave

 

 


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#2 CltFlyboy

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Posted 18 May 2021 - 08:11 AM

WOW Dave, that is AWESOME! Congratulations!!!



#3 Phillip Creed

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Posted 18 May 2021 - 08:17 AM

I'd be lucky to own one of these once, let alone twice.

Our club has one of these in our observatory.  It's only deficiency is in color correction since it's not made with ED glass, but even that's not really that bad.  What more than makes up for the minimal chromatic aberration is the lens figure--just crazy-high Strehl.  As perfect a star test as I've ever seen.  On steady nights, the scope just laughs at us when we hit 400X; as if to say, "...that's all you got?"

And it is a superb deep-sky instrument, too.  I can easily make out the propeller in M13 with that scope.

A bit slow for imaging, but the right reducer will make it more manageable.  I learned to do DSO astrophotography with this scope, and as long as you don't mind a little purple-fringing around stars, it'll do a fine job.

 

Clear Skies,

Phil


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#4 coopman

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Posted 18 May 2021 - 08:55 AM

Awesome Dave.  I'm happy for you.



#5 Phillip Creed

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Posted 18 May 2021 - 11:39 AM

Here's a photo of NGC 2903 I shot with the 6" f/8 AP that's in our club observatory.  Blue bloat, yes, but not bad all things considered.

Clear Skies,

Phil

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  • NGC 2903.jpg

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#6 Tyson M

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Posted 18 May 2021 - 03:27 PM

Congrats. A beautiful classic deserves to be used.



#7 Bonco2

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Posted 18 May 2021 - 03:49 PM

The dumbest thing in astronomy I ever did was selling my AP 6 inch f/8. Enjoy yours.

Bill 



#8 bobhen

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Posted 19 May 2021 - 09:21 AM

I believe the early 6" F8 AP's could be ordered either better corrected for visual or better corrected for film photography.

 

Bob



#9 Cotts

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Posted 19 May 2021 - 09:35 AM

I believe the early 6" F8 AP's could be ordered either better corrected for visual or better corrected for film photography.

 

Bob

Concerning the 'violet fringe' in those images - would inserting a Minus Violet filter take care of it?  I have one....

 

 

Dave



#10 sanbai

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Posted 19 May 2021 - 09:55 AM

Concerning the 'violet fringe' in those images - would inserting a Minus Violet filter take care of it?  I have one....

 

 

Dave

The Baader semi-apo cuts all extreme violet and 50% of indigo, plus the (small) advantages of neodymium glass. There is a small increase of contrast in DSO observing (negligible in urban skies...). Also good for planetary work, although the Baader Contrast Booster filter is *reportedly* better and offers a bigger cut in short wavelengths . Both give natural-looking colors in planets. The moon is warmer with the semi-apo, but you get used and it isn't weird at all. 


Edited by sanbai, 19 May 2021 - 10:06 AM.


#11 sanbai

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Posted 19 May 2021 - 10:02 AM

The Semi-Apo transmission is the red line
Dark blue: OIII lumicon Gen 3
Cyan: DGM NPB
 
plot.jpg

 


Edited by sanbai, 19 May 2021 - 10:03 AM.


#12 GSBass

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Posted 19 May 2021 - 10:48 AM

Do they still retain a premium price even with modern scopes being corrected at a higher level? I’ve alway been curious about that, although they were the best you could buy in the time period is it still a good buy today?


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#13 Phillip Creed

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Posted 19 May 2021 - 11:14 AM

Do they still retain a premium price even with modern scopes being corrected at a higher level? I’ve alway been curious about that, although they were the best you could buy in the time period is it still a good buy today?

They still do, though not as insane as other AP scopes.  You could probably find a 6" f/8 pre-ED Astrophysics triplet for less money than a 105mm Traveler.  I've seen them go as low as $3,500, but $4,000 - $5,000 seems more common.  Given the lens figure, it's honestly a steal if you're a visual observer.

It doesn't have perfect color correction, but it's not BAD and it's perfectly suitable for visual use.  Polychromatic Strehl is really the *only* deficiency the scope has.  Better than Sidgwick, but not quite as good as Conrady standard.  Probably in the 0.85-range polychromatic Strehl.

Where it shines is lens figure, and that's as close to perfect as you'd expect from Astrophysics.  One look through an old 6" f/8 AP triplet will leave no doubt that Roland Christen designed the optics.  We were looking through this scope at our club's observatory last October during the Mars opposition.  I have NEVER had a better view of Mars than I did that night.  The scope is like a bottomless pit; you can chuck as much magnification into it as you want if it's a steady night and it won't even break a sweat.

A mild minus-violet filter is really all you need.  Anything stronger than a Baader Fringe Killer (i.e. Baader 495nm longpass) is overkill.  Our club has a mild filter in the Lumicon Minus-Violet filter that's just left in the diagonal and it reduces purple fringing on 1st-magnitude and brighter stars by about 50%, though there really isn't much fringing to begin with.  A Fringe Killer would probably eliminate any residual purple, but unlike the Lumicon, the FK would visibly affect the color balance.

If you could find one, I think the best overall MV filter out there is the long-discontinued William Optics VR-1.

 

Clear Skies,

Phil


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#14 Cotts

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Posted 19 May 2021 - 11:20 AM

Do they still retain a premium price even with modern scopes being corrected at a higher level? I’ve alway been curious about that, although they were the best you could buy in the time period is it still a good buy today?

About $3500 CDN for mine.....   In rough agreement with a new APM 6-inch ED doublet apo ($2500EUR = $3690CDN ) .  Would be an interesting "shoot-out" I think..  

 

 

Dave
 


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#15 Cotts

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Posted 19 May 2021 - 11:23 AM

They still do, though not as insane as other AP scopes.  You could probably find a 6" f/8 pre-ED Astrophysics triplet for less money than a 105mm Traveler.  I've seen them go as low as $3,500, but $4,000 - $5,000 seems more common.  Given the lens figure, it's honestly a steal if you're a visual observer.

It doesn't have perfect color correction, but it's not BAD and it's perfectly suitable for visual use.  Polychromatic Strehl is really the *only* deficiency the scope has.  Better than Sidgwick, but not quite as good as Conrady standard.  Probably in the 0.85-range polychromatic Strehl.

Where it shines is lens figure, and that's as close to perfect as you'd expect from Astrophysics.  One look through an old 6" f/8 AP triplet will leave no doubt that Roland Christen designed the optics.  We were looking through this scope at our club's observatory last October during the Mars opposition.  I have NEVER had a better view of Mars than I did that night.  The scope is like a bottomless pit; you can chuck as much magnification into it as you want if it's a steady night and it won't even break a sweat.

A mild minus-violet filter is really all you need.  Anything stronger than a Baader Fringe Killer (i.e. Baader 495nm longpass) is overkill.  Our club has a mild filter in the Lumicon Minus-Violet filter that's just left in the diagonal and it reduces purple fringing on 1st-magnitude and brighter stars by about 50%, though there really isn't much fringing to begin with.  A Fringe Killer would probably eliminate any residual purple, but unlike the Lumicon, the FK would visibly affect the color balance.

If you could find one, I think the best overall MV filter out there is the long-discontinued William Optics VR-1.

 

Clear Skies,

Phil

I have the Lumicon Minus violet, 2" which i could put in the diagonal and fuggeddaboudit..... 

 

Dave
 



#16 Phillip Creed

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Posted 19 May 2021 - 11:38 AM

About $3500 CDN for mine.....   In rough agreement with a new APM 6-inch ED doublet apo ($2500EUR = $3690CDN ) .  Would be an interesting "shoot-out" I think..  

I have the Lumicon Minus violet, 2" which i could put in the diagonal and fuggeddaboudit.....

 

Dave

 

Dave,

At roughly $2,900 USD, that's a *fabulous* price for a scope of that capability and vintage.

The Lumicon MV should serve you well just threaded into the diagonal and left there.

 

Clear Skies,

Phil



#17 RichA

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Posted 19 May 2021 - 01:53 PM

About 8 or 9 years ago I acquired this scope, put a beauty Feathertouch focuser on it.  I used the scope for about 3 years then sold it to a guy in my club.  It's optics are superb, every inch an AP....there wasn't a thing wrong with it.

 

He hasn't even unpacked it!  It has been sitting for 6 years!

 

I knew this and, needing a complimentary scope to my new 20-inch Dob, asked him if he would sell it back to me...  He agreed, same price....

 

I'll have it in a few weeks....I've asked him to unpack it and check everything.... 6 years in a box.....

 

I'll put it on my new EQ6 mount which I am picking up today.....Primary use will be double star viewing as well as video lucky imaging and maybe some DSLR imaging.....public outreach when it returns to us....

 

Dave

 I sold an AP 120mm back in the day because I had aperture fever. Now, if I were to try to get it back, it's price would be about twice what I sold it for.



#18 Tyson M

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Posted 19 May 2021 - 02:56 PM

I think I care more about figure than poly chromatic strehl. I've seen, and currently own a phenomenal achromat which is very enjoyable despite the false color.

 

Edit: besides, I wouldnt be able to afford a large refractor with amazing polychromatic strehl (like a Zeiss APQ 150 just bigger)


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#19 Bonco2

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Posted 19 May 2021 - 04:05 PM

Had a sharp contrasty view of two Jupiter moons eclipsing at 600X with the AP 6 inch f/8. Could see one moon's disc superimposed on the other. Never seen anything like that. 

Bill


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#20 Wildetelescope

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Posted 19 May 2021 - 04:07 PM

About 8 or 9 years ago I acquired this scope, put a beauty Feathertouch focuser on it. I used the scope for about 3 years then sold it to a guy in my club. It's optics are superb, every inch an AP....there wasn't a thing wrong with it.

He hasn't even unpacked it! It has been sitting for 6 years!

I knew this and, needing a complimentary scope to my new 20-inch Dob, asked him if he would sell it back to me... He agreed, same price....

I'll have it in a few weeks....I've asked him to unpack it and check everything.... 6 years in a box.....

I'll put it on my new EQ6 mount which I am picking up today.....Primary use will be double star viewing as well as video lucky imaging and maybe some DSLR imaging.....public outreach when it returns to us....

Dave


F8 or F9?

Jmd

#21 Wildetelescope

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Posted 19 May 2021 - 04:28 PM

F8 or F9?

Jmd

CC07E66B D014 4E20 84EB 59BE2F643CE2

 

Mars.  AP 152 mm F9 starfire, circa 1989.  Pre ed triplet.  Taken with a QHY 290 Color camera, zwo ADC and 1.5X Brandon Barlow.  According to Roland, if you do narrowband imaging, there should be no real difference between these scopes and the new ones.  Broad band and OSC will of course show a little color, but nothing horrible, in my experience.  Below are a couple images taken with my 5 inch version taken with my zwo 294 pro OSC.   Good enough for me:-).  But visual use is where I really enjoy using these scopes.  The images just pop, even in my light polluted back yard.  Glad you could get yours back!  Have fun!

 

alnitak calibrated master stack
M42 Calibrated 2020STVersion1
 
Taken with AP 127 f8 Starfire pre ed triplet.  Zwo 294 pro camera, Baader semi-apo filter and for Alnitack, the 27 TVPH reducer/flattener.
 
JMD 

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#22 Wildetelescope

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Posted 19 May 2021 - 04:35 PM

 
June 30 2019 jupiter
io transit July 20 2019

 

 
Jupiter taken with AP 152 pre ed triplet with 2.5 x Barlow and zwo 294 Pro camera.  No ADC correction. 
 
JMD

Edited by Wildetelescope, 19 May 2021 - 04:41 PM.

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#23 Tyson M

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Posted 19 May 2021 - 04:38 PM

I dont see any issues with color correction here! Amazing mars image



#24 Cotts

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Posted 19 May 2021 - 04:53 PM

It is an f/8....

 

I know it is a good price - it was a good price when i sold it to the guy who seemed so keen.....

 

Oh well, plus ça change.....

 

Dave



#25 Wildetelescope

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Posted 19 May 2021 - 05:25 PM

It is an f/8....

 

I know it is a good price - it was a good price when i sold it to the guy who seemed so keen.....

 

Oh well, plus ça change.....

 

Dave

The F8’s are a real piece of history.  They used that famous special NASA glass and Roland’s first commercial iteration of the design.  Most folks do not remember that before AP, commercially available Triplets were for the most part non-existent.  AP initiated the design that is now ubiquitous with imaging refractors today.  It is really quite remarkable that at the time, THEY were the value priced option to the Tak and Vixen Fluorites.  Funny how things go.....

 

JMD


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