81 replies to this topic

[deSitter]

I could do a fair 6" shootout with what I have on hand right now:

 

Parks 6" f/6 Newtonian

Orion 6" f/12 Maksutov

Jargers 6" f/15 Achromat

Yes!

 

-drl

[starman876]

I could do a fair 6" shootout with what I have on hand right now:

 

Parks 6" f/6 Newtonian

Orion 6" f/12 Maksutov

Jargers 6" f/15 Achromat

Roland claimed the color correction on the 6" F8 was equal to F25 achromat.  

[Bob S]

I still have the Astrophysics 6" f/8 that I bought in 1986. It was corrected for visual use. They also came corrected for photographic use. I also still have the Astrophysics 706 mount. It originally had a pier, a number of years ago I got a Manfrotto mount for it, it's a bit lighter that the pier, but the mount is pretty heavy. The counterweights screw on, which makes it a pain to use, but the views through it are still worth the troubles.

[Defenderslideguitar]

Great find     very nice work on your restore   

 we say  what a great find   but I say    "sometimes  a scope finds you"

   clearly, this is true in your case since that scope needed you to find it   and to pick it up and do  proper job            keep us posted as you do   " A Proper Job"

 

 someone once said  that some folks say....".these older ap scopes are really good but not as good as.... blah blah blah "  

 " until you actually look through one "                   and    Oh my word 

    sign me up for a regular older AP  

     

   I have a 1991      A P   6 inch f 12 Starfire    the optics are wonderful   legendary Planetary views       Admittedly, it is almost too much to handle     I need help just to mount it   

    so the older  AP  6 inch  F 8 or  f 9  was really what I had been looking for 

     but   the F 12  found me..............

Edited by Defenderslideguitar, 06 December 2024 - 04:45 PM.

[jragsdale]

Great find     very nice work on your restore   

 we say  what a great find   but I say    "sometimes  a scope finds you"

   clearly, this is true in your case since that scope needed you to find it   and to pick it up and do  proper job            keep us posted as you do   " A Proper Job"

Thank you for the kind words, it means a lot to hear that I'm doing a good service to these vintage instruments. And I can't help but liking to take everything apart to clean every spec of dust from every dark crevice, replace every rusted fastener, relubricate the parts that need it, and get it functionally back to close to the day it left the shop. I'm still shocked that the ad had 1000 hits and I was the first one to take the leap. But like you said, maybe fate had a role to play? DPAC tomorrow hopefully! Not expecting anything other than straight.

[ccwemyss]

It's interesting to see that the focuser tube is blue (anodized?). Mine is gray. And the tailpiece is an intermediate form. On the earliest ones, it was raw aluminum with a cross-hatch knurling, and a long, thin thumbscrew. Now it looks more like yours but has three clamping knobs to handle higher loads and enable centering.

 

I replaced mine with the current version, but discovered that the 2.7" female threads were cut too small -- later they enlarged them slightly to accommodate the anodizing on the tailpiece. I ended up filing down the anodizing with a needle file until it was close, and then worked it in and out until it was possible to screw it all the way in with a nice snug fit. Of course, that's now on the Jaegers 6" f5. 

 

The one down side of replacing the focuser is that I also have the original field flattener, which was designed for the original focuser. Its tube had an extra hole to put a screw through to engage a v-groove in the barrel of the flattener. (I've seen one from just a few scopes later that has a more secure mounting. They were really experimenting at the beginning.) Maybe some day I'll take it to a machine shop and have it reworked to fit the new focuser.

 

Chip W. 

[jragsdale]

It's interesting to see that the focuser tube is blue (anodized?). Mine is gray. And the tailpiece is an intermediate form. On the earliest ones, it was raw aluminum with a cross-hatch knurling, and a long, thin thumbscrew. Now it looks more like yours but has three clamping knobs to handle higher loads and enable centering.

It almost looks like a Teflon wrap around the outside of the tube? I bet I could peel it right off but it seems to be working fine, so I won't do that.

Attached Thumbnails

• 
• 

[jragsdale]

DPAC tomorrow hopefully! Not expecting anything other than straight.

As expected, an excellent DPAC with some minor Chromatic Aberration visible with blue suffering the most while green in focus.

 

Inside focus: 

 

 

Outside focus:

 

 

Color channels separated out: 

 

Edited by jragsdale, 07 December 2024 - 10:44 AM.

[deSitter]

As expected, an excellent DPAC with some minor Chromatic Aberration visible with blue suffering the most while green in focus.

 

Inside focus: 

 

20241207_075940.jpg

 

Outside focus:

 

20241207_080315.jpg

 

Color channels separated out: 

 

20241207_081242-COLLAGE.jpg

I think that is spherochromaticism more than chromatic aberration. Interesting that such results likely prodded RC to attack that part of the problem. Should be a great performer.

 

-drl

[jragsdale]

I think that is spherochromaticism more than chromatic aberration. Interesting that such results likely prodded RC to attack that part of the problem. Should be a great performer.

Yeah, from what I've read, there's a choice an optician has to make between chromatic abberation and spherochromaticism. I'm still muddy on how to tell them apart in a DPAC though. But you can kind of tell that this lens will be excellent, very sharp, with minimal CA, but slightly visible on brighter objects and will manifest in blue/violet.

[deSitter]

Yeah, from what I've read, there's a choice an optician has to make between chromatic abberation and spherochromaticism. I'm still muddy on how to tell them apart in a DPAC though. But you can kind of tell that this lens will be excellent, very sharp, with minimal CA, but slightly visible on brighter objects and will manifest in blue/violet.

The bowed bars mean spherical correction in blue is not as good as in green and red. It will be interesting to compare it to a known good achromat where spherochromaticism is less of a problem. Johann says RC claimed this scope was equivalent to f/25, so F/D = 4 and you should get performance equal to a 4" f/16 finest achromat, like the Edmund 4".

 

-drl

[jragsdale]

The bowed bars mean spherical correction in blue is not as good as in green and red. It will be interesting to compare it to a known good achromat where spherochromaticism is less of a problem. Johann says RC claimed this scope was equivalent to f/25, so F/D = 4 and you should get performance equal to a 4" f/16 finest achromat, like the Edmund 4".

It would be interesting to focus it for blue then repeat the DPAC to see what influence chromatic abberation has on the results. 

[RichA]

Yeah, from what I've read, there's a choice an optician has to make between chromatic abberation and spherochromaticism. I'm still muddy on how to tell them apart in a DPAC though. But you can kind of tell that this lens will be excellent, very sharp, with minimal CA, but slightly visible on brighter objects and will manifest in blue/violet.

Seems to be a lot smoother than lesser six inch scopes that have been tested, modern ones.  Many of the ones from Asia (except Japan) seem to have (if over  five inches) machine-polish patterns, roughness in the bands, the "phonograph record" look to them. 

[starman876]

As expected, an excellent DPAC with some minor Chromatic Aberration visible with blue suffering the most while green in focus.

 

Inside focus: 

 

20241207_075940.jpg

 

Outside focus:

 

20241207_080315.jpg

 

Color channels separated out: 

 

20241207_081242-COLLAGE.jpg

That is the same way mine tested.  Excellent lens.   Great deal for $1200.   You will have excellent viewing.

Edited by starman876, 07 December 2024 - 12:58 PM.

[TG]

As expected, an excellent DPAC with some minor Chromatic Aberration visible with blue suffering the most while green in focus.

Inside focus:

20241207_075940.jpg

Outside focus:

20241207_080315.jpg

Color channels separated out:

20241207_081242-COLLAGE.jpg

You can see from the asymmetry in the blue channel image that blue has a different focus than red/green. Indeed, that was the shortcoming of the first "apos" that AP made from short flints, the famous 1-off Corning "NASA glass" RC bought from NASA. To get a sense of spherochromatism, you'll have to DPAC using color filters or different color LEDs.

Edited by TG, 07 December 2024 - 03:50 PM.

[Idaho_Skies]

Had the pleasure of stopping by Jordan's place this afternoon and seeing this scope personally.  Great find, and it is in great hands for any restoration desired

[ccwemyss]

You can see from the asymmetry in the blue channel image that blue has a different focus than red/green. Indeed, that was the shortcoming of the first "apos" that AP made from short flints, the famous 1-off Corning "NASA glass" RC bought from NASA. To get a sense of spherochromatism, you'll have to DPAC using color filters or different color LEDs.

According to Thomas Back's history of early Astro-Physics lenses, the 6" f8 was after they ran out of NASA glass and switched to a Kz-FSN-4 abnormal dispersion flint. He says it wasn't quite as well corrected.

 

There were only 24 of the 6"f9 made with the NASA glass. It also went into 4"f6, 5"f6, and 5"f12 models (he doesn't say how many) and a few of the early 6"f12 super planetary scopes. It would be interesting to know if Barry's 6"f12 is one of them. 

 

Chip

[jragsdale]

According to Thomas Back's history of early Astro-Physics lenses, the 6" f8 was after they ran out of NASA glass and switched to a Kz-FSN-4 abnormal dispersion flint. He says it wasn't quite as well corrected.

How much was the glass type vs how much was the slower f/9 speed?

[ccwemyss]

He doesn't say specifically. But he does say, "By-the-way, this "NASA" flint glass was the ultimate in short KZ flint glass. No manufacture supplies a flint glass that can match its abnormal dispersion properties today." So I would assume it is a combination. 

 

Chip W. 

[jragsdale]

Very nice! Looks like the dew shield straightened up reasonably well. 

 

Hope you get some clear skies to try it out soon.

The original dew shield did not straighten out at all (yet). I also have Christine at AP hunting around their backstock for vintage dew shields this size to see if they have any spare.

 

In the mean time, I wanted a fun project so I 3D printed a replacement dew shield. This is a slip fit with enough tension to hold on at all angles. 8" OD vs 7" of the original, about 30% lighter weight, and chunky baffles printed on the interior for stray light suppression. Printed with PETG-CF, so quite sturdy and matte. A fun temporary solution.

 

 

 

I also had some clear skies for a couple hours, the first in weeks as we've had a ruthless inversion here in Boise lately. I was able to get views on Venus, Saturn, Vega and Epsilon Lyrae before the fog rolled back in. Venus was very turbulent down low, but I tried some lucky imaging on it with a 5x barlow, ASI290MM and a green CCD filter: 

 

 

Saturn at the meridian was EXCELLENT at 300x (50x/inch), 4 moons readily apparent with glimpses of the Cassini division. The fog rolled in before I could break out the color camera.

 

Vega had some expected color, but a very sharp defined and even airy disk. I just focused in and out, over and over and over marveling at the identical diffraction patterns.

Epsilon Lyrae was no challenge at all naturally, but it's so satisfying to see them with such tight and compact airy disks. Can't wait for some time on Jupiter and Mars with this scope next, this was a good first light!

Edited by jragsdale, 09 December 2024 - 11:08 PM.

[starman876]

The original dew shield did not straighten out at all (yet). I also have Christine at AP hunting around their backstock for vintage dew shields this size to see if they have any spare.

 

In the mean time, I wanted a fun project so I 3D printed a replacement dew shield. This is a slip fit with enough tension to hold on at all angles. 8" OD vs 7" of the original, about 30% lighter weight, and chunky baffles printed on the interior for stray light suppression. Printed with PETG-CF, so quite sturdy and matte. A fun temporary solution.

 

20241209_155903.jpg

 

20241209_155925.jpg

 

I also had some clear skies for a couple hours, the first in weeks as we've had a ruthless inversion here in Boise lately. I was able to get views on Venus, Saturn, Vega and Epsilon Lyrae before the fog rolled back in. Venus was very turbulent down low, but I tried some lucky imaging on it with a 5x barlow, ASI290MM and a green CCD filter: 

 

final.jpg

 

Saturn at the meridian was EXCELLENT at 300x (50x/inch), 4 moons readily apparent with glimpses of the Cassini division. The fog rolled in before I could break out the color camera.

 

Vega had some expected color, but a very sharp defined and even airy disk. I just focused in and out, over and over and over marveling at the identical diffraction patterns.

Epsilon Lyrae was no challenge at all naturally, but it's so satisfying to see them with such tight and compact airy disks. Can't wait for some time on Jupiter and Mars with this scope next, this was a good first light!

I can just imagine the first time in 1985 when someone who was used to looking through achromats first looked through the 6" F8 AP at high power and how breathtaking it must have been,  

[firemachine69]

The original dew shield did not straighten out at all (yet). I also have Christine at AP hunting around their backstock for vintage dew shields this size to see if they have any spare.

 

In the mean time, I wanted a fun project so I 3D printed a replacement dew shield. This is a slip fit with enough tension to hold on at all angles. 8" OD vs 7" of the original, about 30% lighter weight, and chunky baffles printed on the interior for stray light suppression. Printed with PETG-CF, so quite sturdy and matte. A fun temporary solution.

 

20241209_155903.jpg

 

20241209_155925.jpg

 

I also had some clear skies for a couple hours, the first in weeks as we've had a ruthless inversion here in Boise lately. I was able to get views on Venus, Saturn, Vega and Epsilon Lyrae before the fog rolled back in. Venus was very turbulent down low, but I tried some lucky imaging on it with a 5x barlow, ASI290MM and a green CCD filter: 

 

final.jpg

 

Saturn at the meridian was EXCELLENT at 300x (50x/inch), 4 moons readily apparent with glimpses of the Cassini division. The fog rolled in before I could break out the color camera.

 

Vega had some expected color, but a very sharp defined and even airy disk. I just focused in and out, over and over and over marveling at the identical diffraction patterns.

Epsilon Lyrae was no challenge at all naturally, but it's so satisfying to see them with such tight and compact airy disks. Can't wait for some time on Jupiter and Mars with this scope next, this was a good first light!

 

 

 

I'd vinyl-wrap that dew shield, then get an auto-shop to match to as close as possible. The lighter weight is a huge benefit on a scope that size.

[jragsdale]

I'd vinyl-wrap that dew shield, then get an auto-shop to match to as close as possible. The lighter weight is a huge benefit on a scope that size.

Why vinyl wrap before paint? You can paint directly onto 3D filament.

[TG]

The original dew shield did not straighten out at all (yet). I also have Christine at AP hunting around their backstock for vintage dew shields this size to see if they have any spare.

 

In the mean time, I wanted a fun project so I 3D printed a replacement dew shield. This is a slip fit with enough tension to hold on at all angles. 8" OD vs 7" of the original, about 30% lighter weight, and chunky baffles printed on the interior for stray light suppression. Printed with PETG-CF, so quite sturdy and matte. A fun temporary solution.

 

20241209_155903.jpg

 

20241209_155925.jpg

 

I also had some clear skies for a couple hours, the first in weeks as we've had a ruthless inversion here in Boise lately. I was able to get views on Venus, Saturn, Vega and Epsilon Lyrae before the fog rolled back in. Venus was very turbulent down low, but I tried some lucky imaging on it with a 5x barlow, ASI290MM and a green CCD filter: 

 

final.jpg

 

Saturn at the meridian was EXCELLENT at 300x (50x/inch), 4 moons readily apparent with glimpses of the Cassini division. The fog rolled in before I could break out the color camera.

 

Vega had some expected color, but a very sharp defined and even airy disk. I just focused in and out, over and over and over marveling at the identical diffraction patterns.

Epsilon Lyrae was no challenge at all naturally, but it's so satisfying to see them with such tight and compact airy disks. Can't wait for some time on Jupiter and Mars with this scope next, this was a good first light!

Very nice dew shield! I think this will be better than anything vintage A-P is going to be able to find for you. I'd spray a flat black paint on the inside to get rid of glancing reflections. I especially like Krylon Chalkboard Black, it's very black and tough as well, meant to be used on chalkboards.

[Terra Nova]

Wow! And a fairly rare bird too. Nice find at a great price. Congrats!