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  #341  
Old 16-06-2018, 03:21 PM
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sopticals (Stephen)
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Quote:
Originally Posted by pixelsaurus View Post
Cheers. Sorry for the delay. Will it also remove any overcoating as well?
Yes.

Stephen
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  #342  
Old 16-02-2019, 06:55 PM
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sopticals (Stephen)
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Any body out there?

Hi guys, you got any new mirror grinds on "the make"?

I've been so enjoying the full 2 degree wide views of Milky Way with my 10" Zhumell (one of my two "grab and go" scopes) using a Nagler 31T5 that for a "more intense" experience at the 1200-1250mm focal length I have decided to grind out a 12 1/2" blank I have sitting spare, to approx f4. Exit pupil at the 40.3x is close to 8mm, but my dark adapted pupil opens pretty wide at 7mm plus so won't lose much light.

Have played with 6"f8, 8"f6, 10"f5 (all around 1200-1250mm fl) so why not try 12.5" f4 for the same size FOV?

Anyway started the project today. See picture.
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  #343  
Old 19-02-2019, 09:11 AM
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pixelsaurus (Mike)
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No grinding at the moment. A friend has given me a complete 225mm diameter Dall Kirkham mirror set ,which need to be coated, plus a transfer lens. I need to find a tube or summit. This after flocking my 12" newt and building an EQ platform.
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  #344  
Old 20-02-2019, 09:26 AM
Stefan Buda
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Another one alive in Melbourne:
A couple of 250mm, f2.7 CDK primaries in the making.
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  #345  
Old 09-04-2019, 10:57 AM
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Lognic04 (Logan)
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Bump! Is anyone still out there making mirrors? I'm working on a 10 inch f3 then next a 16 f3
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  #346  
Old 09-04-2019, 05:33 PM
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DaveGee (Dave Gault)
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I finished a 10"F3.something a few years ago but never tubed it. However I've started on a scope to house it. No secondary, video camera at prime focus.

Here are some photos. The filenames say 10f3 but I don't remember the context of what I was doing at the time (~2006)

I observe occultations and this is primarily to observe asteroid occultations, pre-point and drift while I sleep.
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  #347  
Old 09-04-2019, 05:46 PM
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Lognic04 (Logan)
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Hi Dave, good to see someone working on a mirror! Just a fair warning, your mirror shows quite bad Stig (see the tilt of the Ronchi bands changes.

But, I'm excited to see the finished scope!
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  #348  
Old 03-07-2019, 01:07 PM
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sopticals (Stephen)
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Progress on second 33" mirror.

Just finished a 12 1/2" f4.14 mirror (well ready for final star testing). The second of my 33"ers, this one a f3.95 is going through corrective figuring to
correct a "rolled edge" defect. Did manage to get the inside 30" to an acceptable level of performance, but need to do better.All my work is done by hand, no machinery of any kind, (except did do the edge bevel with a belt sander).
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  #349  
Old 12-08-2019, 12:21 PM
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sopticals (Stephen)
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Dob structure for star testing.

Recently threw together a cheapy Dob assembly to star test mirrors from 6"f8, 8"f6, 10"f5, 12 1/2" f4 (currently "housed") to 14 1/2" f3.6.

Construction cost was minimal as only used "stuff" I had lying around from
previous projects. Didn't have enough of same type of wheels for cart, so use a pair from a discarded child's toy for rear. Will get a matching
pair in due course.

Stephen.
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  #350  
Old 13-08-2019, 01:55 AM
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Does anyone know if there are any groups still doing mirror making/grinding in the Ballarat area? I think the local observatory used to but I don't think they do now?

I'd love to give it a go but would rather do so under supervision.


Thanks for any help.
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  #351  
Old 15-08-2019, 06:12 PM
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sopticals (Stephen)
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Seemingly "no response" to your request. Maybe they have "all died".

Mainly just a few of us "old timers" left out there. Gone are the days when one "had" to fabricate ones own optics. All to easy now to buy affordable Chinese scopes.

Stephen.
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  #352  
Old 16-08-2019, 04:45 AM
Rod
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Hi

I was active in Ballarat way back in the 90s when a few of us were making mirrors. I've lost touch since moving from there so not sure what's happening there now.

I notice you are in Melbourne. There is an active group of mirror makers now within the ASV who are part of the Instrument Making section.

Stefan and Logan are two whose posts you may have seen.

Regards

Rod
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  #353  
Old 09-09-2019, 10:42 PM
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Is there anyone in Perth that still does mirror making and want's to be annoyed by a 37 year old noob that has no idea but is keen?
I work week on week off so I can spend a good solid amount of time learning.

Even if there is some sort of formal training courses I could do with testing and making optics would be great.

I've talked to Logan on CN and he might be refiguring my mirror for me but if there was someone closer that I could lean from and do it myself then all the better.
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  #354  
Old 10-09-2019, 09:28 AM
Startrek (Martin)
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Try Palmway Optical
Located mid north coast NSW
See attached
Cheers
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  #355  
Old 31-10-2019, 03:02 PM
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sopticals (Stephen)
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Aluminizing in NZ

Hi, if you are looking for someone to aluminize/re-aluminize your mirror at a very reasonable price, contact Andrew at scopes@scopesnz.com

I have had a number of mirrors,(6"-12.5") coated by Andrew. Didn't cost "an arm and a leg". Most recent was the 12 1/2" at a cost of NZ$75 plus GST.
At present his chamber can handle up to 18", but he is thinking of building a larger vacuum tank able to manage possibly up to 700mm (27.5").

Doesn't offer an overcoat at this point in time,but is looking to include this option.

Oh! thought I might take the opportunity to drop a couple of Ronchi pics of where I'm up to with my 33"f4 mirror.

Stephen
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  #356  
Old 26-11-2019, 08:36 AM
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Hi Stephan,

are you only using the 12" subdia lap on the 33", or do you use a bigger one also?

My in-house polishing area (front half of living room) has been "annexed" (we replaced carpet on concrete floor with floorboards, so I polishing is banished from there), so I am setting up in the basement. I am considering making a subdia lap as I found progress slow and difficult with the full diameter 22" lap. Hopefully I will get restarted in the next few days (coming back to parabola from sphere(ish!). But mainly I have been busy with the renovation, work and family life (and made a safe, unobstructed solar dobsonian in time for the mercury transit. No sunspots now so it's a bit useless for the moment. :-(

Cheers,
hamish
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  #357  
Old 26-11-2019, 03:01 PM
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sopticals (Stephen)
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Hi Hamish,

Although I have previously used 22",17",11" down to 7" "subby" laps on each of the two 33" mirrors, I decided to just use the 12 1/2" lap used for polishing my recent 12 1/2" mirror (first time I used a full sized lap since early 1960's).
With the full sized lap on the smaller mirror I found I had an almost perfect sphere on coming out of the polish. From there figured if I dug out my old 7" lap it would be "easy peasy" to parabolize. Well couldn't have been easier, as it took only 3 1/2" hours to get a good parabola without any edge defects. My testing was simple, just 133 lpi Ronchi grating (bench testing) at ROC and Ronchi 133 lpi eyepiece star test to get the "jail bar" straight line (null) going through focus.

So on this second attempt at figuring this 33 I decided to "put in the yards" to remove the wide rolled edge using just the one lap (12 1/2") for the whole job. Had to go back to a sphere (or pretty close), which just seemed to happen as I removed the "shoulder" where rolled edge started. Once the edge was corrected I used the same strategy as for parabolizing the smaller 12 1/2".

Stephen
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  #358  
Old 15-06-2020, 08:09 PM
hamishbarker
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As Stephan has already seen on "the other forum" and by email ( and who deserves big thanks for selling me the fine ground blank and giving me the (rather out of date now but they worked!) silvering chemicals.) I decided that my 550mmf4.6 was done. i read in a book that opticians often don't declare a mirror done, it is just that the mirror gets taken away from them. It was the second time (well, third if I count the time I was close except for a terribly turned outer 25mm.) that it was ready to go. I measured it at about 1/8 wavefront error a few weeks back and hubristically decided I could better that, and ended up overcorrected so had to go backwards a bit. Then I proceeded slowly, just 80 strokes and then testing, pretty much every day for a week or two.



Now it's nominally 1/5 wavelength, but a lot of that is a bit of turned down edge. maybe when I have more experience (and hubris) I'll attempt to fix that at some future recoating occasion.


yesterday was home silvering in the garden. Lots and lots of scrubbing with cotton balls, precipitated chalk and demineralised water. and then another scrub. Finally the tin chloride spray, a thorough rinse, then the magic couple of minutes with the silver solution and reducer in hand spray bottles.



There's a patch of frosty coating, so I need to redo the coating, but we had a little first light celebration with a friend and couple of beers and managed to see alpha crux through a tiny cloud hole, as well as thoroughly inspect the red anticollision lights on the nearby radio tower a couple of km away while collimating and star testing.


what a journey. I can't wait for some proper observing!


To anyone who is contemplating attempting their first mirror, go for it. one key thing I learned is the importance of having somewhere to be able to work on the mirror without needing to set up each time. I progressed a lot faster then. Also, procrastination is easy.



Hamish
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  #359  
Old 15-06-2020, 09:13 PM
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Sunfish (Ray)
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Thanks for that encouragement. I have three Pyrex mirror blanks given to me to work on. A rough ground 100mm f5 for practice . An f7 200 mm which I would like to regrind to F4 . And finally , once I can work out what I am doing , a blank 12 inch which may be sometime before I can get to.

I have just received my grinding materials, 80 , 220 , 600 silicon carbide , 25 micron and 14micron aluminium oxide as that was what I could get locally.

I have made a mirror cell for an old finished 8 inch f7 so I can the tube assembly and secondary assembly process sorted out.

Any tips starting out or advice about my mirror cell?
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  #360  
Old 15-06-2020, 09:23 PM
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Sunfish (Ray)
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It would be interesting to see how your silvering turned out. Any images yet?
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