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Quantum Telescopes

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#1 jonnyastro

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Posted 26 March 2007 - 06:40 PM

What exactly were these, i just sawa picture of one for the first time, looks like a Questar. Were they good optically?

#2 BHunt

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Posted 26 March 2007 - 06:45 PM

Check 3 lines under this post!
Bill

#3 Eric P

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Posted 27 March 2007 - 08:43 AM

There is a good write up on Quantum in Rod Mollise's used SCT guide.

http://skywatch.brai...ed/used_sct.pdf

#4 Clive Gibbons

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Posted 27 March 2007 - 09:58 AM

Short synopsis:

Optically as good as Questars. Both Questar and Quantum optics were manufactured by Cumberland Optical.

The Quantum 4 is brighter and has better resolution than a Q3.5, due to the Quantums larger aperture.

The Quantum's "single arm" fork mounting isn't as stable as Questar's dual arm design.

The Quantum 4 used a rubber belt drive in it's focus mechanism. The rubber would dry up and break. It's a repair that's commonly required by Q4 owners. Upgrading the belt to a metal chain is the usual fix.

The Quantums didn't employ Questar's integrated finderscope design. Instead, used a normal finder mounted on the side of the OTA. Less elegant solution, but brighter finder images.

Relatively few Quantums were sold during their brief existance. So, they're rarer and perhaps, more collectible, for that reason.

#5 Glassthrower

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Posted 27 March 2007 - 01:55 PM

Sounds like a Quantum four on dual-arm fork/wedge with a metal drive chain and a nice aftermarket finder would be the way to go for someone wanting superb optics in a small package - and I assume less worry about "keeping it all original" which we understandably see with Questars. Personally, I would rather use my own finder than an integrated one - more options that way. But that is just me, and I am one 401k account short of owning either one. ;)

Regards and clear skies,

MikeG

#6 Don W

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Posted 27 March 2007 - 03:38 PM

I had a 4" Quantum and felt it was one of the best scopes I've ever owned. Unfortunately the mount left some to be desired. The sold some 4" OTAs and I would love to get one of those.

#7 jonnyastro

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Posted 27 March 2007 - 06:22 PM

I was a bit taken aback by how attractive i found them when i first saw a pic last week. To me it has a more business like appeal than the beautiful Questar.

#8 petrogeoman

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Posted 27 March 2007 - 08:47 PM

Actually the rubber focusing belt on the Q4 is fine. The problem is that OTI used the same diameter/thickness belt for the Q6, so it was stretched a couple of inches more and tends to wear out.

My Q4 (pic below) surpassed my Questar 3.5 (now sold) in resolution, contrast and image brightness. Although it likely was the aperture difference and longer focal length that accounted for most of the difference, if one looks through old OTI literature, apparently the optical specs for the Quantums were more stringent than for Questar. (I've read 1/20 wavefront at the eyepiece for the Quantum as opposed to 1/10 wave for Questar.) There are rumors on various web sites that optical standards suffered towards the end. Alan Kerro told me a while back that there wasn't a degradation in optical quality, just in cosmetic finish.

My only real issue with the Q4 is the mount. It's very sturdy -- I don't have any vibration problems with the single fork. I don't know how one could given that the assembly is so big and heavy. Really overbuilt. I picked up an orange C5 (fork mounted) for use as my travel scope after I realized this Q4 was never going on a plane!

Just my two cents -- there are some real experts on OTI and Quantums on here. Definitely a unique collector's scope if you can find one!


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#9 petrogeoman

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Posted 27 March 2007 - 09:00 PM

And one more pic of having fun with the webcam...

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#10 Glassthrower

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Posted 28 March 2007 - 02:28 PM

Nice looking scope and rig! :)

Yes, that single fork looks very sturdy. This is the first time I have seen one.

What is the focal ratio on that Q4?

Regards and clear skies,

MikeG

#11 Steve_M_M

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Posted 28 March 2007 - 02:55 PM

I cut and pasted this from a word doc. so I apologize for formatting errors. I will attach a couple of the imbedded pictures this evening.

Optical Techniques Quantum 6 Restoration

I would like to thank Allan Keero at Davro Optical, Phil Houston, and Paul Feffer for assistance with my restoration.

I must apologize for the poor, incomplete pictures. I got started and did not think about pictures. Then, after I decided to write this, I just could not get myself to un-collimate the scope just for pictures sake. Hopefully, my write-up is detailed enough if you need to reference it.

Interesting story (short version)….I collect and restore vintage telescopes. In August 2006, a listing was posted on Ebay for a Quantum 6 telescope. I bid on it. Turned out the auction was a fraud (what’s new for Ebay?) A few days later I got an email from an Ebay member saying he had a Q6 and wanted to sell it locally. Yeah right! I thought. I figured there was a 50/50 chance of seeing a scope and getting mugged. Keeping this long story short….I drove to downtown LA high rent district and bought the scope from the original owner (I later learned he was a principal at Lunday Thagard Oil Co who OTI has as the original owner).

When I brought the scope home, I had my usual thought of whether I could bring this back to life. All of the aluminum had corrosion, the primary needed recoating, the diagonal was tarnished, and there was no power cord or lens cover. Further testing revealed the Barlow was set wrong, the diagonal was misaligned, and the slow motion on the dec axis was stiff. But, nothing was broken, the tube was in GREAT condition, and I could tell the scope had little use and needed restoration.

My parents have always said I like to take things apart and see if they float. I guess that is what took me to mechanical engineering. Nowadays, I take things apart and actually fix them. I have disassembled and restored about 50 scopes. No Maks. No Questars. NO Quantums. But, since this all came out happy in the end, I thought I would give some tips to future owners of Quantum telescopes.

OTI became Davro Optical. For 25 years Davro has serviced the OTI scopes. As of today, 10/17/06, I have been told that Davro no longer services the Quantums. The reasons are not important, business is business, and may change in the future. So, you may ask “where does one get parts?” A better question is “Will you ever need original parts?” Probably not. But, if you need them you can check with Allan Keero at Davro, Warren at Photon Instruments, me, and a host of others who have acquired parts over time. But, read on….

The first order of business was clean up. I use automotive aluminum paste polish. All of the knobs are easy to remove with a hex head set screw. I took them all off and polished them until I was blue in the face. Good for some, not for others. If you are really having trouble, I suggest 0000 steel wool. Then, re-polish to take out the fine scratches. For fine work where you do not want paste all over, I recommend Eagle One Never Dull Aluminum Wadding Polish. This is just a can of wadded up cloth with Magical powers. Lots of polishing. I use a toothbrush, steel wool, or wire brush to clean the edge grooves of the knobs. Start with less harsh and move up only as necessary.

The tube looked great, but the dewshield was really scrapped up. Duplicolor Ford Midnite Blue T218 is the color OTI used for the scope. NAPA ordered it for me and it arrived next day. I repainted the dewshield. Note here is that although I shook the can well, the paint color was not an exact match. I bought a second can, same result. I would not suggest using this paint as a touchup.

Time to go nuts and get the primary mirror out. I first tried my spanner wrench to remove the corrector. Ouch. Too tight. So, the way to get at the primary is to have someone hold the control box and turn the entire OTA counterclockwise. Once you make that first turn, but sure to put the scope vertical with the control box on the floor/table. It will take several turns, but it will come off. When you pull it off, pull it straight up or else you will hit the mirror and damage it.

Using your tool of choice, mark the placement of the mirror with respect to the control box or the focus shaft. See the Springs? I hate it when I encounter springs. Do not worry. The mirror is held by the large aluminum plate as seen here. The springs provide no support minimal support.



This plate is threaded and the black tube threads into the plate. Turn the focuser until the mirror is furthest from the control box (opposite what is shown above) (this will help reduce pressure on your next steps) Hold the plate and slowly unscrew the black tube counterclockwise. Try to keep the aluminum plate with downward pressure. Do NOT let the mirror be pressed back up into the tube. It is being forced that way. Do like I did and take a long look at this before you start. After a few turns, the mirror will be freed. Note the O-ring and retainer under the mirror. Note the few parts here. All, springs, O-ring, and retainer could be found from McMaster Carr and other sources. The order of things is black tube, mirror, O-ring, retainer, plate.



Send your mirror off to QSP/Infinite Optics in Santa Ana, CA. I spent a lot of time and did quite a lot of research to determine the composition of the original coating. I spoke with Dwight Cumberland at Cumberland Optics (original manufacturer), Allan Keero, and others. I ended up speaking extensively with the coatings engineer at QSP. The mirror came out AWESOME. QSP provides a nice graph, mine at 98%. QSP said the mirror was extremely smooth and easy to work with.

While the mirror was out, I checked the corrector from inside the tube. A little bit of pressure and I was able to get the retainer off. Index the position. Use a spanner wrench. Edmund sells a nice one. Mine was in superb condition as was the secondary. OTI guys suggest placing a .070 O-ring cord underneath the corrector to provide support, ease collimation, and provide a better seal from moisture. I had already replaced the corrector when I learned this so I can not say if it works.

Now, you are going to want to get into the control box. First off, the hex head on the bolts is the crazy 7/64 hex wrench. You will not find that one on your Huffy set. You will take all the bolts off and then the control box will not come off. Ok, screw them all back in :- ) In the picture above I have marked the retaining clip. You can only see this when you turn the focuser clockwise as far as it will go (as in picture). Pop this off with a flathead screwdriver. Now, go back and remove the bolts holding the control box to the mirror assembly support. Whoola! The box comes off, the brass threaded sleeve below the retaining ring flies off, the springs jump. All is good. Ok, no springs flying 

The Barlow is available for cleaning, same goes for the diagonal. The Pictures below shows the set screws that are used to align the Barlow and diagonal. No idea how these could get off, but you can use those screws to realign everything. Here you can also see the focuser belt. The piece everyone says is bound to fail. Well, mine was original and looks great. To determine this, use a 10x loupe with a flashlight and examine the edges of the belt to look for fraying. I currently have extras if you need them. But, you will not. Just another easy part to get. If you are reading this 20 years down the road, know that the belt is a sewing machine belt and can be had at https://sdp-si.com/e...asp?GroupID=213 Choose 48 as number of groves and then any of the first 3 work. Urethane Polyester looks like an exact match. Replacement is easy once you have gotten this far.




Hopefully you are looking at this and saying “Direct drive would be easy” I agree, drill a hole in the back of the control box, extend the threaded focuser shaft, provide a support sleeve for the longer shaft, a couple bearings…easy. I have not done this as I like the focuser on the side. But, Warren at Photon (not recommended) will do it for $350. I will do it for $100.

Replacing the focuser belt at this point would be a matter of marking the location of the gear on its rod with a permanent marker. Do the same for the position of the set screw sleeve you would have to remove to be able to slide the focuser belt over the gear on the gear pictured in the back. The one in front is easy as you can just place the belt over the gear.

Notice that with a little research, there is hardly a part in there that could not be replaced. Maybe the diagonal mirror, but even then you could use the axial port. But, even the diagonal mirror could be found.

Put the control box back together. Push the brass focuser sleeve from aluminum mirror plate into place. The position is not important at this time. The springs should still be attached at the top and make sure they are in the set hole on the control box. Leave the clip off the focuser shaft.

Hey, the mirror is back! Oh my, never collimated a Quantum before. No worries. Ok, most likely no worries. Notice the incredible machining tolerances of the parts. The black tube slides over the center post. You can not jiggle it at all. Put the black tube into the mirror center hole. Notice the tight tolerance. Ok, screw the focuser all the way back out so the plate is furthest from the control box. The springs should be exerting minimal pressure. This is a bit tough. Line the retaining ring up over the hole in the aluminum plate. Do the same for the O-ring. Place the mirror over the center post and set in gently over these two parts.

Ok, new paragraph for a reason. Slide the black tube over the center post. Come down to the mirror and look at all sides to make sure you will not hit the mirror. Notice you can not see the threads for the aluminum plate. Do not disturb your original set up. Push the black tube through and thread it into the aluminum plate. You will most likely have to take several tries to get it all lined up correctly.

YOU ARE WORKING WITH ALUMINUM. IT IS EASY TO CROSS THREAD. DO NOT FORCE THE PARTS!

Thread the tube into the plate. Just before it hits the mirror, time for some measurements. Use a digital caliper and measure the distance all around from the top of the control box to the top edge of the mirror. It should be the same all around. Notice you can move the mirror slightly to raise or lower a side. Set your mirror at your alignment points from before. I know, what kind of collimation/alignment method is this? Well, more to follow.

Screw the black tube down until the mirror is just slightly hard to turn. You focuser shaft should be aligned in the middle of the hole and at 90 degrees to the control box. If not, note that the brass sleeve can be shifted. Do so to align. Check mirror. Check spring for vertical alignment. Turn the focuser clockwise to raise the threaded focuser shaft just above the brass sleeve. Replace the retaining clip.

Now you have to put the OTA back on. Place the control box face up on a table. Have someone hold it level. Place the OTA over the center post and SLOWLY over the mirror. Thread it onto the control box. This is NOT easy. The threads are VERY fine. It should thread easy.

YOU ARE WORKING WITH ALUMINUM. IT IS EASY TO CROSS THREAD. DO NOT FORCE THE PARTS!

Time for a star test. I suspect you will be shocked how close it is. The reason is that Quantum set the scope up so that the machining controlled the alignment. I am sure you noted that there are no collimation screws, bolts, shims, nothing. But, you may well be off a bit. Amazingly, the process is long, but simple. Collimation is done by rotational alignment of the corrector and primary. This takes time, but you need to rotate the corrector little by little, retesting after each rotation. An artificial star will make this a whole lot easier. If this does not do the trick, you get the next stage. Rotating the mirror in the same manner. I did this and then rotated the corrector a full circle for each 1/16 turn of the mirror. A little over ¼ around the mirror, the spot hit. Make sure your black tube is now semi-tightly on the mirror so it cannot turn, but at the same time does not put stress on the mirror.

Note: Lumicon 6.7” Vinyl dust cover ($9.95 at scope city) fits perfectly over the dew shield

#12 Bob Abraham

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Posted 28 March 2007 - 03:05 PM

Thanks so much Steve... what a great post! I've got an old Q-6 and this is just what I needed. I'm really looking forward to seeing the pictures once you embed them. Thanks again!

Bob

#13 Steve_M_M

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Posted 28 March 2007 - 05:42 PM

Just PM me with your email address and I can send you the entire document.

#14 Glassthrower

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Posted 28 March 2007 - 06:27 PM

Steve,

Have you considered submitting this excellent How-To to the article-side of CN?

I bet Quantum owners would love to have access to this.

Regards and clear skies,

MikeG

#15 Clive Gibbons

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Posted 29 March 2007 - 08:30 AM

Excellent article, Steve! :applause:

You mentioned how to collimate a Quantum.
A similar procedure can be used if one's Questar delivers a problematic star image. The Questar's corrector lens is able to rotate freely in it's cell (by design). If your Questar displays some astigmatism or coma, rotate the corrector in small increments and keep checking the resulting star image, until you see a "textbook" quality diffraction image.


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