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[ATM] Rough grinding, focault test
Hello,
Thank you Bob May for your reply to my linear resolution question. I just
saw a post a few emails ago about a focault test at the rough grinding
stage, I think(dangerous). Anyhow, I am at 120 w/ very smooth surface. How
can I focault here? Is a headlight being used to get reflection? Please
help. Would like to take a peek as I have been @ 120 for awhile, which I
consider rough grinding. Could I have misread? Cannot find email, may have
deleted. Is there a way to check myself at this point?
Thank you all,
Miguel
----- Original Message -----
From: <atm-request@atmlist.net>
To: <atm@atmlist.net>
Sent: Wednesday, July 19, 2006 11:00 PM
Subject: ATM Digest, Vol 31, Issue 18
> Send ATM mailing list submissions to
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> Today's Topics:
>
> 1. Mirror-O-Matic (Eric J. Shrader)
> 2. Re: Mirror-O-Matic (Sonya Gaskell)
> 3. Re: New site (vladimir sacek)
> 4. Re: New site (Aki L?tj?nen)
> 5. Re: New site (vladimir sacek)
> 6. CassGen (Richard)
> 7. Refractor baffling (Attila Schn?)
> 8. How round and how square should it be (blank mirror)
> (Roman Toledo)
> 9. Rough 360 linear resolution or 300lp/mm (Miguel)
> 10. Re: Rough 360 linear resolution or 300lp/mm (Bob May)
> 11. Re: Refractor baffling (Bob May)
> 12. Re: New site (Bob May)
> 13. Re: How round and how square should it be (blank mirror) (Bob May)
> 14. Re: How round and how square should it be (blank mirror)
> (Thomas Janstrom)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 18 Jul 2006 20:10:13 -0700
> From: "Eric J. Shrader" <eric.shrader@comcast.net>
> Subject: [ATM] Mirror-O-Matic
> To: atm@atmlist.net
> Message-ID: <44BDA295.60004@comcast.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hello Elbi,
>
> There are plans available to order at mirror-o-matic.com. They are only
> $15 for a CD-rom. I have built the mirror-o-matic 20 from the plans
> and have been very happy with it. I am an engineer and I usually find
> things to modify as I build them but I found this to be very well
> designed for what it does and I didn't change anything.
>
>
> Cheers, Eric
>
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 18 Jul 2006 23:24:24 -0400
> From: Sonya Gaskell <sonya@ggms.com>
> Subject: Re: [ATM] Mirror-O-Matic
> To: "Eric J. Shrader" <eric.shrader@comcast.net>
> Cc: atm@atmlist.net
> Message-ID: <44BDA5E8.4030602@ggms.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
> For Commercial Viabulity's sake, I suggest the following:
>
> A name change from Mirror-o-matic to Miromatic(tm).
>
> PS: It's registered , Ill sell it to you,
>
> jk. : )
>
> Sonya
>
>
> Eric J. Shrader wrote:
>
>>Hello Elbi,
>>
>>There are plans available to order at mirror-o-matic.com. They are only
>>$15 for a CD-rom. I have built the mirror-o-matic 20 from the plans
>>and have been very happy with it. I am an engineer and I usually find
>>things to modify as I build them but I found this to be very well
>>designed for what it does and I didn't change anything.
>>
>>
>>Cheers, Eric
>>
>>_______________________________________________
>>ATM mailing list http://www.atmlist.net/
>>
>>
>>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 19 Jul 2006 10:55:25 -0400
> From: "vladimir sacek" <vla@toast.net>
> Subject: Re: [ATM] New site
> To: <atm@atmlist.net>
> Message-ID: <001201c6ab43$5f15a390$1042fa04@Handsome>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> Thanks, Roman. I agree, there's nothing to like about coma, or anything
> that
> looks like it :). Texareau is a very good reading. For learning about
> aberrations in a telescope, Suiter's "Star testing astronomical
> telescopes"
> is probably the best.
>
> Vlad
>
> ----- Original Message -----
> From: "Roman Toledo" <rtoledo2002@yahoo.com>
> To: <atm@atmlist.net>
> Sent: Monday, July 17, 2006 8:26 PM
> Subject: [ATM] New site
>
>
>> Vlad, very nice web site, as a new user who's reading all I
>> can find.
>> I found it very refreshing specially the pages on airy disk and
>> defraction. I'm currently reading Texareau's book.
>>
>> I beleive I now know what I did not like about a telescope I
>> just sent back. (coma like crazy) Also not having the trained eye of
>> the experts on this list, I know enough to say the 3" tele i have has
>> quite good optics "all things being equal" after colimating it with a
>> laser, and finally having a good night to see thru.
>>
>>
>> thank you for passing on the knowledge.
>> _______________________________________________
>> ATM mailing list http://www.atmlist.net/
>>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 19 Jul 2006 18:13:26 +0300
> From: Aki L?tj?nen <aki.lotjonen@phnet.fi>
> Subject: Re: [ATM] New site
> To: Guy Brandenburg <gfbrandenburg@yahoo.com>
> Cc: atm@atmlist.net
> Message-ID: <44BE4C16.1040204@phnet.fi>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi Guy,
>
> It's sounds not good if you have that kind of experience! Mean I am now
> grinded my new lenses with carbo 220 and seriously have thought to
> trepan them after polishing. My own experiences with a biscuit cutter
> and loose abrasives have been quite positive. Only time consuming. Last
> time I managed to break off one small piece from the center edge of the
> R1 surface. But then I trepaned the lenses after 220 carbo. To use a
> diamond cutter I know nothing.
>
> Rgds,
> Aki
>
>
> Guy Brandenburg wrote:
>
>> I am working my way up to doing the trepanning on our LHN project.
>> I'ms scared - after doing some experimenting with some diamond bits, I
>> see now that you can easily flake off really big chunks if you are not
>> careful. I think I will pitch some pieces of glass to both sides
>> before doing this.
>> Guy
>> *//*
>>
>>
>> Guy Brandenburg
>> Washington, DC
>> My home page:
>> http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Wed, 19 Jul 2006 11:32:56 -0400
> From: "vladimir sacek" <vla@toast.net>
> Subject: Re: [ATM] New site
> To: <atm@atmlist.net>
> Message-ID: <002001c6ab48$9c917050$1042fa04@Handsome>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Ken Hunter wrote:
>
>>It's the cost of the glass that makes the Houghton not acceptable to most
>>ATM's.<
>
> Not versus Maksutov corrector. Still, Maksutov is more
> popular in both ATM and commercial arena. What is it
> about it? Is it that if you make 1mm error in one of the two
> radii, you have a disaster? And the same 1mm radius error
> will not produce discernible aberration with the Houghton.
> Or because 1mm error in the thickness for given radii makes
> the Maksutov unacceptable, while having no effect with the
> Houghton? Or because it always has more uncorrectable
> residual spherical than either Schmidt of Houghton? Or
> because relatively small lower-order spherical in the
> Houghton can be cancelled with adeqate element spacing,
> while there is no way to do it with the Maksutov?
> Hope this doesn't sound as anti-Maksutov campaign;
> those are simply the facts.
>
> Vlad
>
> ------------------------------
>
> Message: 6
> Date: Wed, 19 Jul 2006 16:56:45 +0100
> From: Richard <cnc@cncservo.co.uk>
> Subject: [ATM] CassGen
> To: ATM List <atm@atmlist.net>
> Message-ID: <404495109.20060719165645@cncservo.co.uk>
> Content-Type: text/plain; charset=us-ascii
>
> Hi ATMers,
>
> New version of CassGen uploaded
>
> http://www.atmlist.net/contrib/cnc-at-cncservo-dot-co-dot-uk/CassGen.1.3.2.21.zip
>
> Fixed bug of Ks not changing when configuration changed
> Fixed incorrect evaluation of Ds
>
> --
> Best regards,
> Richard in the UK
>
>
>
> ------------------------------
>
> Message: 7
> Date: Wed, 19 Jul 2006 21:21:51 +0200
> From: Attila Schn? <yolo@chello.hu>
> Subject: [ATM] Refractor baffling
> To: atm@atmlist.net
> Message-ID: <456069314.20060719212151@chello.hu>
> Content-Type: text/plain; charset=Windows-1250
>
> Hello,
>
>
> Is there anybody, who has knowledge about how to design and calculate
> baffles for a refractor?
>
> Does exist any software or site, where I can find information about
> it?
>
> Thank's!
>
> Clear skies!
>
>
> --
> Best regards
>
> Attila Schn?,
> mailto:yolo@chello.hu
>
>
>
> ------------------------------
>
> Message: 8
> Date: Wed, 19 Jul 2006 14:33:25 -0700 (PDT)
> From: Roman Toledo <rtoledo2002@yahoo.com>
> Subject: [ATM] How round and how square should it be (blank mirror)
> To: atm@atmlist.net
> Message-ID: <20060719213325.23165.qmail@web84104.mail.dcn.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> Hello gents, here's another noob question.
>
> How round does the blank have to be and how square should the side be.
>
> I've read how some mirrors use a sling or piano wires on the bottom
> edge once mounted on it's base.
>
> I have one piece that was done without trepanning and is "close" to
> being round, I'm working on putting a good 45^ dege on it before I
> continue to wet grind the edge (I know at this rate it will take even
> longer)
>
> this question even scares me ;) but I'll ask, if you plan on a 9 point
> base and a piano wire sling.
>
> Would it be a good idea to cut a "slight" 1/16"deep groove on the
> glass edge's center so the wire stays put? or is this too great a risk
> to damaging the mirror?
>
> also do you have a good source for polarized film so I can test this
> glass before I waste time on a useless piece.
>
>
> ------------------------------
>
> Message: 9
> Date: Wed, 19 Jul 2006 18:00:06 -0400
> From: "Miguel" <emiliarodriguez@bellsouth.net>
> Subject: [ATM] Rough 360 linear resolution or 300lp/mm
> To: <atm@atmlist.net>
> Message-ID: <000801c6ab7e$b1de4240$0200a8c0@fastlane>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hello All,
>
> Thanks in advance for replies. I am at a critical junction in rough
> grinding. Have 20.5 inch and I am at .215 sagitta. I do a comparison at
> stellafane.com and only diff between f5 and f6 is linear resolution. 300
> vs. 360lp/mm for the faster f5. Which is best for detailed views. Don't
> care about height of scope.
>
> I recall being at Jonathon Dickenson Park (West Palm Beach) w/ the local
> astronomy club and guy next to me w/ 18" custom was perplexed by the fact
> that his bigger 18" appeared to look same magnification as my 13" inch
> custom, w/ the same eyepiece. I was surprised. Same focal length both
> scopes also I think. Of course I was maxed out and I believe he had juice
> to spare. I compared the two at stellafane and based on 4.6 focal ratio
> both had the same linear resolution although angular was .25 arcsec vs.
> .344 for the 13".
>
> Which would be best for cranking in the high mag detail? 300lp/mm @ f6 or
> the 360lp/mm @f5? Hope it is not a dumb issue...just don't know. Thanks
> all.
>
> Migz
>
> ------------------------------
>
> Message: 10
> Date: Wed, 19 Jul 2006 15:50:40 -0700
> From: "Bob May" <bobmay@nethere.com>
> Subject: Re: [ATM] Rough 360 linear resolution or 300lp/mm
> To: <atm@atmlist.net>
> Message-ID: <002501c6ab85$c2fe8ce0$ddadfea9@amd>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Miguel, you have to remember that magnification is a function of
> focal length so if you have the same focal length as another
> scope, the magnification will be the same for a particular EP
> with both scopes. Resolution, on the other hand, indicates how
> fine a detail can be seen with any particular scope and this is
> limited by the diameter of the scope (provided that it is a
> perfect scope) so your 13" scope won't have the resolution that
> his 18" scope will have and thus the larger scope can go to a
> higher magnification to see that finer detail available to him.
> Bob May
> bobmay at nethere.com
> http: slash /nav.to slash bobmay
> http: slash /bobmay dot astronomy.net
> Replace the obvious words with the proper character.
>
>
>
> ------------------------------
>
> Message: 11
> Date: Wed, 19 Jul 2006 15:57:21 -0700
> From: "Bob May" <bobmay@nethere.com>
> Subject: Re: [ATM] Refractor baffling
> To: <atm@atmlist.net>
> Message-ID: <002801c6ab86$b1c9d640$ddadfea9@amd>
> Content-Type: text/plain; charset="Windows-1250"
>
> Simple. Draw a line from the edge of the objective to the
> focuser on the same side on a plan of the scope. Then follow the
> rules for plotting a Newtonian scope baffles using that line as
> the limit for incursion of the baffle to the light path. Draw a
> line from the opposite side of the focuser (input end of the
> tube) to the objective and where the limit line and the crossing
> line cross is where the first baffle goes. From there, the base
> of each baffle is used as the end point for the crossing line
> from the focuser to determine the next location.
> Bob May
> bobmay at nethere.com
> http: slash /nav.to slash bobmay
> http: slash /bobmay dot astronomy.net
> Replace the obvious words with the proper character.
>
>
>
> ------------------------------
>
> Message: 12
> Date: Wed, 19 Jul 2006 16:02:59 -0700
> From: "Bob May" <bobmay@nethere.com>
> Subject: Re: [ATM] New site
> To: <atm@atmlist.net>
> Message-ID: <003501c6ab87$7b746c80$ddadfea9@amd>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I'd rather use a diamond hole saw for trepanning the center hole
> into a finished lens as this won't spread grit about that can
> scratch the surface of the lens.
> I got a 65mm OD hole cutter off of eBay for $18 total along with
> a 125mm one for another project for $30. There's a Hong Kong
> supplier that is selling diamond hole saws for really cheap
> prices.
> I'll note that both of the cutters had some diamonds that really
> stood proud so I'd do some grinding on scrap glass before going
> and cutting a good piece of glass - something that should be done
> with any diamond cutter as well as sandpaper of any kind so that
> the clumps of grit get knocked off before the real work is done.
> Bob May
> bobmay at nethere.com
> http: slash /nav.to slash bobmay
> http: slash /bobmay dot astronomy.net
> Replace the obvious words with the proper character.
>
>
>
> ------------------------------
>
> Message: 13
> Date: Wed, 19 Jul 2006 16:10:00 -0700
> From: "Bob May" <bobmay@nethere.com>
> Subject: Re: [ATM] How round and how square should it be (blank
> mirror)
> To: <atm@atmlist.net>
> Message-ID: <004201c6ab88$7620c980$ddadfea9@amd>
> Content-Type: text/plain; charset="iso-8859-1"
>
> The sides merely need to support the front of the mirror and can
> be at about any angle. Some people (and companies) build
> telescopes with a cone shaped backside for light weight with the
> edges of the blank being a lot thinner than the center of the
> mirror.
> As to roundness, the blank should be reasonably round so having a
> blank that is 1" different in diameters is a bit much but you
> don't have to go to 0.001" roundness to be considered round.
> Grinding the front surface won't be affected by the oblateness of
> the blank so don't worry about that. The sole effect of being
> oblate is that the Airy disk won't be round but rather oblate in
> the same ratio as the difference in the mirror.
> Bob May
> bobmay at nethere.com
> http: slash /nav.to slash bobmay
> http: slash /bobmay dot astronomy.net
> Replace the obvious words with the proper character.
>
>
>
> ------------------------------
>
> Message: 14
> Date: Thu, 20 Jul 2006 09:57:12 +1000
> From: "Thomas Janstrom" <thomas@moiler.com>
> Subject: Re: [ATM] How round and how square should it be (blank
> mirror)
> To: "'Roman Toledo'" <rtoledo2002@yahoo.com>, <atm@atmlist.net>
> Message-ID: <000a01c6ab8f$18841460$0b01a8c0@Mylaptop>
> Content-Type: text/plain; charset="windows-1250"
>
> Hi Roman,
>
> I would suspect that because you managed to trepan the glass OK that you
> can
> skip the polariser film, but if still want to get some, Surplus Shed
> (www.surplusshed.com) usually has some in their miscellaneous items
> category, another place is Willman-bell (I don't think you can order it
> online, and I don't know their contact numbers as I haven't dealt with
> them
> personally). I'm sure there are many other suppliers out there, if all
> else
> fails you could always use an old pair of Polaroid sunglasses, one lens at
> your light source the other between you and the glass. Just rotate the one
> you're holding to find the right axis.
>
> Cheers, Thomas.
>
> -----Original Message-----
> From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf
> Of
> Roman Toledo
> Sent: Thursday, 20 July 2006 7:33 AM
> To: atm@atmlist.net
> Subject: [ATM] How round and how square should it be (blank mirror)
>
> Hello gents, here's another noob question.
>
> How round does the blank have to be and how square should the side be.
>
> I've read how some mirrors use a sling or piano wires on the bottom
> edge once mounted on it's base.
>
> I have one piece that was done without trepanning and is "close" to
> being round, I'm working on putting a good 45^ dege on it before I
> continue to wet grind the edge (I know at this rate it will take even
> longer)
>
> this question even scares me ;) but I'll ask, if you plan on a 9 point
> base and a piano wire sling.
>
> Would it be a good idea to cut a "slight" 1/16"deep groove on the
> glass edge's center so the wire stays put? or is this too great a risk
> to damaging the mirror?
>
> also do you have a good source for polarized film so I can test this
> glass before I waste time on a useless piece.
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>
> --
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>
> ------------------------------
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>
> End of ATM Digest, Vol 31, Issue 18
> ***********************************
>
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ATM mailing list http://www.atmlist.net/