Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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An older Cloudy Nights posting mentioned that a piece of foam rubber held the primary mirror in collimation, and I thought a few photos may interest the forum
This 1980 (made in USA) model showed flaring on stars, and I was aware that the primary was not correctly positoned.
An easy test to determine if the foam has lost it's support is to invert the scope and gently shake it. If you hear the primary moving, the foam most likely has seen it's day
Removing the circular spring ring holding the secondary window is fairly easy, as is removing the window. The window has a groove that mates with the housing, so replacing it leaves no guesswork
I cut a 4.1" circle of poster paper to cover the primary while removing the circular spring clip that holds it in place. The primary will lift right out of the tube
I had wondered about the thickness of the primary in these scopes, and was quite surprised to see that it is 5/8" thick
The grey foam that we are all familiar with has little resiliency after 29 years. You can see on the left where I pressed my finger into it before taking the photo.
After replacing the foam (gave the mirror a bath first), and reassembling the scope, a simple check with a lasermate was promising. Tonight I star tested the scope with a 9mm orthoscopic, and was rewarded with an identical pattern both inside and outside of the focal point. I count 3 diffraction rings and the same image of the central spot, and suspect it is a very good mirror.
I am aware that the 9mm only yields 49x in the scope
The writing on the back of the mirror shows the date (Nov 18, 1980), the diameter of the mirror (4.25"), and I can not quite guess what the 5/4 would represent?
I am so impressed with the improvement, that I now wonder what it would cost to have the mirror resilvered?
Well, that is my story. Perhaps this may encourage others to take a second look at that old Astroscan.
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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2nd photo
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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Final photo
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helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2659
Loc: Phoenix, AZ
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great work! how are the views?
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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I was impressed with the views after the repair.
Stars now focus to pinpoints across the FOV on this particular model, using the 28mm RKE eyepiece. After looking at the optics firsthand, I have changed my initial opinion of the build quality of the early models.
Naturally you have to admire any telescope that you can so easily carry and set up. The sphere mount was pure genius. Being able to rotate the scope in the mount to better position the EP is a feature that few scopes offer.
The Astroscan certainly fills the void between binoculars and larger scopes. Compared to giant binoculars on a tripod, the whole package is more portable and definitely has a more comfortably viewing position, as well as a much larger field of view (which I personally enjoy in a scope)
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helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2659
Loc: Phoenix, AZ
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post a pic of the entire set up!
i always wanted one of those... back in the days of Edmund Scientific's red tube, fork mounted 8" scopes!
there is a member here from Philly that still has one of those!
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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Not sure what you meant by the entire setup photo?
If you meant a photo of the Astroscan, that is easy.
I did not take any more photos of the repair process. About the only other item of interest would have been the large split rings that hold the window and primary in place, but they are just large metal split rings.
One helpful hint about replacing the lower split ring would be that I held it closed with a single piece of cotton string, bound across it's diameter. When I had it in place in the lower part of the scope, a swipe with a razor released it to spring open. The primary mirror was still covered with the circular piece of poster board during this time. A few presses around the split rings circumference then snapped it into the notches that hold it in place
This was the simplest method that I could think of to replace the lower split ring. The upper is much easier to work with, as you can see what you are doing
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Mike Rapchak
professor emeritus
Reged: 11/17/06
Posts: 568
Loc: Indiana, USA
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Ken,
I found your presentation delightful - mainly because I owned one of these wonderful little 'scopes; got it as a Christmas present in 1980.
This thing was beyond reproach; for as small as it was it yielded wonderful views. No problems with the optics (and those RKEs are great EPs)! And that ingenious globe mount was a joy (we used to call the 'scope 'The Big Red Hair Dryer').
You are fortunate to have one of the earlier, high-quality versions. I never knew that the primary was supported by foam! If I still had mine I'd have found your posts invaluable.
Many thanks for sharing your experiences with us! 
Mike Rapchak Jr.
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helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2659
Loc: Phoenix, AZ
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yep, that's the pic! ...of the scope it's self.
how big of a fov can you get?
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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Mike,
Thanks for the kind words. I did not know if there would be any interest in the Astroscan repair, but since I found little info searching, I thought I would share what I have learned
For Helpwanted, the FOV with the std 28mm RKE EP is 3 degrees. Even more interesting is the FOV with a TV 7.4mm Plosssl is 0.8 degrees....quite impressive at the given 60x power. I find it necessary to use the eyecup with the 28mm EP, as your eye has to be centered for that particular EP
I have seen satellites (thorough the EP) before while observing, but rarely. Using the Astroscan last night, I counted 9, including one pair travelling together, side by side
While scanning through Sagitta last night, I noticed one star that looked like a double at 16x. At 60x, the Astroscan clearly showed the pair. Lacking any way to measure the seperation, I could only estimate that perhaps 4 stars could have fit into the space between the pair, and I was impressed with the optics on this view.
One thing I would like to add here. I find that the little scope is such a joy to use, that the "quick look" I had planned turns into a 2 hour session. It is partly because of the nice wide views, and partly because of the simplicity in scanning with the scope. The name was well though out, as was the design
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desertrefugee
Pooh-Bah
Reged: 08/06/07
Posts: 1220
Loc: Arizona
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You're killing me, Ken. I recently sold an Astroscan that had been in the family for a couple of decades. It rode in our RV for years as the kids were growing up.
I've regretted it ever since and now even more.
BTW, nice work on a very delicate procedure - with ample opportunity for "messing" it up.
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"Illimitable ocean, without bound, Without dimension, where length, breadth, and height, And time, and place are lost." - Milton
-Darrell
Reflectors - 76 to 305mm (f4.7 to f9.2)
Refractors - 50 to 120mm (f5 to f16.7)
Binoculars - 6x15 to 22x100
N. Phoenix, AZ
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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Darrell,
Thanks for the additional comments. I was looking for something to fill that step between binoculars and pulling out the larger scope for a quick look
I considered sending the scope back to Edmunds for repair, but have always wondered exactly what that primary mirror was like. I had suspected that it was just a thin, inexpensive piece of glass, and was quite surprised when I had it laying on the counter.
Once I saw the mirror firsthand, I suspected that it could do much more if properly aligned. I see no coma at all in the FOV through the scope now, and the stars focus into pinpoints. The low magnitude double pair was quite a surprise. I have searched through my SkyAtlas 2000.0, but that area is filled with doubles, and I cannot identify them
I had not intended to promote the older Astoscan reflectors, but feel they do not deserve the "Rodney Dangerfield" reputation that they seem to have. This particular scope certainly has merit
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Astraforce Paul
Carpal Tunnel
Reged: 04/05/05
Posts: 1879
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Ken, I've owned several, and used several more, nearly all vintage ones, and they've worked like a charm.
You are absolutely right-- the sphere mount is a delight and makes the scope an incredible joy to use. I use mine on an Edmund tripod, which is lightweight. The whole set up is a quick grab 'n' go and the views are very satisfying. Your comment that they bridge the gap between binocs and larger telescopes is spot on. In fact, I'd recommend that people start with a 'Scan rather than binocs because it is more versatile.
As to make-overs, for the non-DIY and faint of heart, Edmund will clean and collimate your scope for $35 and that includes return shipping! A great deal.
By the way, adding a piece of teflon tape to the inner edge of the focuser turns that into a smooth, easy to tweak operation--and resolves any of the jump issues with the push/slide focuser!
I always wondered if the little red ball wonder was the inspiration for the Port-a-ball line of scopes. I also wish that someone would put out a 6" f/5 2" focuser scope with a sphere mount.
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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Astraforce Paul
Thanks for the teflon tape advice. My focuser works fine, but I will remember that tip
I was aware of the tune up at Edmunds for $35, and do recommend it over doing it yourself. In my case, I wanted to see the mirror in the scope firsthand, just to see for myself what Edmund installed. Once I had it out, I knew the photos would be interesting for others. The manual for this scope says that the mirror is Pyrex
I admire the 8" Portaball scopes, and imagine they are a joy to use. The $3,000 price holds me back, but they are made in the USA, and I give the company credit for their quality. I would also like to see them venture into a 6" model
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proud uncle
Carpal Tunnel
Reged: 01/22/07
Posts: 1576
Loc: Central Texas
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Ken,
Did you use the same foam, or replace it? Where would you get replacement foam? You said the old foam had lost it's resiliency. How did you collimate it without a center spot on the primary; or did you center spot the primary? How easy was it to adjust the secondary position and tilt?
It sounds like you had an interesting project!
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Kenneth
Zhumell 10" Dobsonian (f/4.9)
2" 32mm WA eyepiece
9mm, 12.5mm, and 20mm Plossls
6mm TMB/BO Planetary
2" 2x ED Barlow
Nikon 10x50 binocular (6.5 deg FOV)
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proud uncle
Carpal Tunnel
Reged: 01/22/07
Posts: 1576
Loc: Central Texas
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Quote:
By the way, adding a piece of teflon tape to the inner edge of the focuser turns that into a smooth, easy to tweak operation--and resolves any of the jump issues with the push/slide focuser!
I just noticed that Edmund has incorporated teflon into their newest version of the Astroscan. They've also added a red dot finder. Everything else looks the same. I wish they would return production to the USA, at the same standards as before.
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Kenneth
Zhumell 10" Dobsonian (f/4.9)
2" 32mm WA eyepiece
9mm, 12.5mm, and 20mm Plossls
6mm TMB/BO Planetary
2" 2x ED Barlow
Nikon 10x50 binocular (6.5 deg FOV)
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Ken Haydu
member
Reged: 12/21/08
Posts: 57
Loc: Southport, NC
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Kenneth
The original foam was of no use anymore. I replaced it using the type of foam that is sold for use as both exercise pads and for laying under camping bags. Comes in a blue sheet 1/2" thick at Walmart's sporting goods section.
I used contact cement for a secure bond of the foam to the mirror, which appeared to be the original method
Once the disc of foam was bonded to the mirror, I used a sharp razor blade to trim it into the proper shape. This type of foam is more easy to shape than foam rubber, and also makes a nice liner for eyepiece cases as it is easily cut with a 1.25" circular drill hole saw, to make holders for your eyepieces.
The Edmund design uses the pressure of the slightly compressed foam to press the mirror up against the retaining ring. When the foam does this, the mirror is square to the tube and the mirror was in collimation.
The secondary mirror and it's holder is cemented to the glass window. There is no adjustment there, and if the secondary were out of alignment, it would be another chapter. Fortunately, the bonding epoxy that is used seems to continue to do it's job over the years; it is just the foam under the primary that gives out
Hope that answers your questions
Edited by Ken Haydu (07/07/09 01:17 PM)
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Astraforce Paul
Carpal Tunnel
Reged: 04/05/05
Posts: 1879
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I thought the Astroscans were made in Japan for many years--and those are the much coveted ones.
Given the increasingly incredible and high quality mass-produced mirrors coming out China, however, maybe even the new 'Scans are providing great views.
While the vintage ones I've owned and used could handle high power well (some nice views of Saturn and its Cassini Division), they've always excelled at low power, rich field views-- and, from what I've read, even the ones with less than top quality mirrors still do pretty good at such views.
In any event, impressive work Ken!
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RAK on Tour
member
Reged: 11/12/07
Posts: 32
Loc: Sedalia, Missouri
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My old Astroscan also lost the resiliency of its foam "mirror mount." Years ago I took the circular spring ring out from the optical window, but the window wouldn't budge! It looks to me like it's glued in place. Am I missing something on removing the window? Mine is an older model made before they started supplying the scope with an RKE eyepiece.
Since the scope was so poorly collimated with the sagging foam, and I couldn't get the optical window out at the front, I did what any 10-thumbed do-it-yourself-schmuck would do. I took a hacksaw to the globe and cut a hole big enough to get to the mirror. Out came the steel spring ring that secures the mirror and out came the saggy foam and mirror. Now it's time to recoat the mirror and put it into a conventional tube (I used a shipping tube). I bought a smaller secondary from Orion and used a mirror cell design from a book. Once the mirror is re-coated I'll put it all together. But hey! If someone can tell me how to get that optical window out, maybe I'll remount the mirror in the original body, patch the old globe and have another go at using it as originally designed. I got some amazing views from that scope, including the best of the Andromeda galaxy I've ever had (Joshua Tree National Monument after a clearing rainstorm).
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Roger
Celestron C4-R 102mm achromat
Skywatcher 80mm F/5 achromat
Zhumell 10" Dobsonian
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KerryR
Pooh-Bah
Reged: 12/05/07
Posts: 1172
Loc: SW Michigan
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Great to hear you had such great success with this repair!
I have an older Japanese 'Scan that I replaced the foam on, as well as added teflon tape to the focuser a while back.
Mine's collimated quite well, and handles reasonably high power, though I usually only use it with a 32mm Plossl.
I 'made' my own PFT tape for the scope with teflon pipe wrap from the hardware store and double-sided scotch tape. Worked like a charm.
I love these scopes!
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Kerry
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