Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Seeking Suggestions for Preserving Inspection Signatures on Moldy Lens

  • Please log in to reply
37 replies to this topic

#1 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 26 March 2020 - 10:35 PM

Hello Classics CNers. Hoping you and your love ones are all healthy and happy.

On Super Bowl Sunday, I found a Tasco on FB Marketplace with moldy lens in a collimating cell, and was successful in dismantling the objective cell assembly.

 

41A76DBA-F524-4F8F-91FC-8878694329BB.jpeg

 

86AE76A5-E16C-44A1-BFE0-2B4DD277B172.jpeg

The cool thing I found is that both the flint and crown bear, I assume, an inspector’s signatures. I was going to soak the lenses in a 1:1 hydrogen peroxide and ammonia bath. However, in my limited experience, I have found that the baths usually washes away the stacking order marks. I would like to preserve the signatures and marks, and of course clean the lenses. My question, is there a way I can cover the signatures with clear tape, painter’s tape, nail polish (my wife’s), or perhaps a thin smear of Elmer’s glue? ShouId I soak the lenses or spray the solution on and let it sit and then hand wash repartition? Have you had a successful experience with something similar?

 

Many thanks in advance for your time and sage words of advice. 
 

Healthy days and clear nights to You All. 

 

My

 

 

 

 

Attached Thumbnails

  • 32BF902C-7ABB-4C55-8022-766325C5DA6D.jpeg
  • 46E03AE6-09F8-4E60-B1B7-D3C48415CB6D.jpeg
  • 2BEF5CAE-0976-407E-B825-78A4AB9F421D.jpeg

  • AstroKerr likes this

#2 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 27 March 2020 - 09:13 AM

 I would use a clear paint like nail polish. The glue used on  the tape may not hold when wet and if you pull the tape off, some of the writing may come off with it. Most of the Elmers glue products are also water soluble so not a good choice as well.

   What is critical once you get the elements clean is not so much getting the alignment marks to line up,  With modern day lens, they don't have wedge so the marks don't do anything but to get the air gap uniform and of the correct thickness. So be careful when cleaning the elements to not lose the spacers or distort them. 

   To check that the air gap is uniform, place the assembled lens under monochrome or semi monochrome light. A cheap CFL bulb will work fine. You should see interference rings between the two elements. They should be round and centered. If not be sure the spacers are at 120° centers placed the  same amount inward from the edge. If they are correct in their position and the  rings are not centered  and or round, you can  push down slightly on the glass just above a spacer to move the rings until they are. Once you get the lens back in the cell check them again. Also double check that you got the lens element in the correct order. Don't assume that how you took them out is correct. You never know what was done to the scope in the past and it is common to find one flipped over or the whole cells backwards in the cell. I have seen it many times and others here as well have found the same. 

   Here is a picture of what you should see. I'm using  my desk  lamp which has a CFL bulb in it.

 

           - Dave 

 

  lens interference pattern CFL bulb.jpg              


  • madeline, PawPaw, Kasmos and 2 others like this

#3 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 27 March 2020 - 12:49 PM

Thank you Dave! This is very helpful. I had always thought that the alignment marks were critical. Prior to disassembling the cell, I did a quick check of the interference rings and they were completely off center. 
 

My



#4 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 27 March 2020 - 03:33 PM

 In the old days like the 1800's when lens were ground by hand the elements could  have wedge ie one side was thicker than the other. So you would measure the edge thickness and find the low and high spots on both elements and place the high on one over the low on the other to try to cancel it. If a lens has too much wedge stars turn into short spectra. This is called lateral color.

With machine ground lenses the tolerance can be held much tighter so wedge in the elements is not that big of concern but one can get wedge many time what is in the glass from uneven air spacing.  So there is nothing wrong with aligning the elements to the marks IF they have real meaning. I have seen antique lens that have been marked in the past be someone that disassembled them and the marks been   totally off from what they should be. So I never trust alignment marks I test everything. 

 As I said the air gap issues can be many time worse than the edge  wedge issues. The problem is information about alignment marks keeps getting emphasized be those that are trying to  help but really don't understand what is going on and miss the point about the air gap uniformity.

   By the way, I looked at the picture of lens out of the cell and what I'm seeing is the bottom element is the crown and the top is the flint. So I'm sure you load the lens into the back of the cell so the crown is facing the sky.  Just be sure when you  get ready to put it back in you get the element in the correct order on the stand.  I have loaded  lenses backward a couple of times and the you don't get an image that is fuzzy mess. The images is actually OK but not nearly as good as it could be so just double check things. I know of antique lenses that were but in backwards for many many years and not questioned because someone did it in the past and the next person found it that way and just repeated the mistake. Take nothing for granted when working on old telescopes since you never know what was done to them in the past.

 

                      - Dave 


Edited by DAVIDG, 27 March 2020 - 05:42 PM.

  • AstroKerr and Van Do9:3 like this

#5 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 27 March 2020 - 04:57 PM

Dave,

 

You are correct. In order to remove the lens, I lowered the cell assemble onto the tissue roll tube with the crown on bottom and flint on top. Is it an axiom that the crown is thinner than the flint?
 

Thank you, 

 

My


  • AstroKerr likes this

#6 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 27 March 2020 - 05:46 PM

Dave,

 

You are correct. In order to remove the lens, I lowered the cell assemble onto the tissue roll tube with the crown on bottom and flint on top. Is it an axiom that the crown is thinner than the flint?
 

Thank you, 

 

My

 The crown is thinner because of  the combination of the refractive index of the glass and the design being positive while the flint is negative.   A majority of the time the crown faces the sky but there are design like a couple of Brashear lenses that have the flint forward. So you can't assume that the crown always faces the sky.

 

               - Dave 


  • AstroKerr and Van Do9:3 like this

#7 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 28 March 2020 - 11:13 AM

Cleaned the lenses late last night with great results. I first painted over the alignment marks and the signatures with a book repair PVC glue. My preference would have been clear nail polish but none could be found.

 

I had cut the bottom of a milk jug for a tub and placed the infected lenses on cotton make up remover pads for their bath. I first sprayed the lenses with ‘Rejuvenate’ neutral ph soap scum cleaner and let is sit for the recommended 3 minutes. That removed a lot of the surface crude without having to wipe the surfaces. Then I threw out the old pads and cleaned the milk jug for the hydrogen peroxide (H202) and ammonia (NH3) solution. I mixed 80ml each part. Letting the lenses soak for about an hour, I wiped the cell assembly with alcohol wipes (70% isopropyl C3H80) to disinfect. 
 

After swipes with a Qtip cotton swabs and diluted Windex, and mineral water rinse, a very serviceable RAO objective:

 

C4B7B203-74C2-44A6-86D9-CBC85B9C89A3.jpeg

3E49F84F-5F84-43EB-86F2-0BFCF82A1F92.jpeg

 

And my sad attempt at capturing interference rings. They are hard to photograph. Does the light source need to be far away from the lens?

376CA451-DA4E-4524-A82E-F79EB62283BA.jpeg

 

Will retake better interference photo but next is an attempt at collimating the cell. Never done collimating so fingers crossed. 
 

Thank you for helping me as the cleaning, disinfecting, and restore progresses. 

 

My
 

 

 

 

 


  • PawPaw likes this

#8 ccwemyss

ccwemyss

    Viking 1

  • *****
  • Posts: 933
  • Joined: 11 Aug 2016
  • Loc: Massachusetts

Posted 28 March 2020 - 06:57 PM

I find that alignment marks are really useful -- as I'm rotating a lens to see if there is any difference due to orientation, they tell me when I've gone all the way around. Otherwise I wouldn't know when to stop. And when there actually is a difference, they tell me how far off the original alignment was. smile.gif

 

But seriously, I've only found a few lenses among the loaner set (which just goes back to about 1952) where rotation made a difference, and that was usually due to old spacer residue or clam chips interacting with new spacers. Getting the spacers right is more significant than the rotation. 

 

Chip W. 


  • PawPaw and Van Do9:3 like this

#9 PawPaw

PawPaw

    Mariner 2

  • *****
  • Posts: 218
  • Joined: 05 Jan 2013
  • Loc: West Central Missouri

Posted 28 March 2020 - 07:12 PM

Cleaned the lenses late last night with great results. I first painted over the alignment marks and the signatures with a book repair PVC glue. My preference would have been clear nail polish but none could be found.

 

I had cut the bottom of a milk jug for a tub and placed the infected lenses on cotton make up remover pads for their bath. I first sprayed the lenses with ‘Rejuvenate’ neutral ph soap scum cleaner and let is sit for the recommended 3 minutes. That removed a lot of the surface crude without having to wipe the surfaces. Then I threw out the old pads and cleaned the milk jug for the hydrogen peroxide (H202) and ammonia (NH3) solution. I mixed 80ml each part. Letting the lenses soak for about an hour, I wiped the cell assembly with alcohol wipes (70% isopropyl C3H80) to disinfect. 
 

After swipes with a Qtip cotton swabs and diluted Windex, and mineral water rinse, a very serviceable RAO objective:

 

attachicon.gifC4B7B203-74C2-44A6-86D9-CBC85B9C89A3.jpeg

attachicon.gif3E49F84F-5F84-43EB-86F2-0BFCF82A1F92.jpeg

 

And my sad attempt at capturing interference rings. They are hard to photograph. Does the light source need to be far away from the lens?

attachicon.gif376CA451-DA4E-4524-A82E-F79EB62283BA.jpeg

 

Will retake better interference photo but next is an attempt at collimating the cell. Never done collimating so fingers crossed. 
 

Thank you for helping me as the cleaning, disinfecting, and restore progresses. 

 

My
 

I have found by trial and error that if you can get the CFL light to have a light colored background, white works well.    (ie: bouncing off toward the lens) it enhances the abiltiy to capture the newton rings.  Here is a pic I took yesterday on my 4 inch unitron.  The CLF light is approx 3 inches away from a white wall.  I have the lens (in this case in the OTA cell) pointing toward the light and the wall approx 3 feet away.  Give it a try.

Attached Thumbnails

  • 20200327_145407a.jpg

  • Van Do9:3 likes this

#10 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 28 March 2020 - 11:17 PM

Thank you Chip and Don for the great advice. Will do them both tomorrow. 
 

Chip, hope you and your students are well and able to complete the semester online. 
 

Don, the 4” Unitron is gorgeous. Fantastic find. 
 

My



#11 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 29 March 2020 - 09:29 AM

 If you have a laser collimator it is very easy to get your lens perfectly aligned. Place the laser in the focuser and make a paper mask the same diameter of the lens and with center marked. Place the mask over the lens so it is exactly centered. The laser should hit the center mark. If not adjust  the  tip and tilt of the focuser so it does. Now you have the mechanical axis of the focuser aligned  with the lens.

  Remove the paper mask  and point the scope at a wall a couple of feet away. You'll see a laser spot on the wall and if your lens is out of alignment a number of other spots above and below it. Adjust the lens so those spots merger into the center one. Now your lens is perfectly aligned.

 

                - Dave 


Edited by DAVIDG, 29 March 2020 - 10:01 AM.

  • Van Do9:3 likes this

#12 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 29 March 2020 - 10:05 AM

Dave, I do not have a laser collimator but have been interested about how they worked and now I do, thank you. I do have a refractor collimating eyepiece. Would the principle be similar but with visual align of the paper target mask?

 



#13 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 29 March 2020 - 10:32 AM

Dave, I do not have a laser collimator but have been interested about how they worked and now I do, thank you. I do have a refractor collimating eyepiece. Would the principle be similar but with visual align of the paper target mask?

 Your alignment eyepiece should work the same with the paper mask it place. I would also suggest that  try to do the alignment in the daytime using a glint of sunlight off a distance object like an insulator on a power pole or off a piece chrome on a car. The glint won't move vs a star at night and during the day you can easily see the screws on the cell. Also slightly defocus the glint so it will be easier to tell when you have adjusted the lens so it is round. Use a fairly high powered eyepiece and  also put the eyepiece directly into the focuser vs using a star diagonal.  Make sure the focuser doesn't have a lot of play in it.  The diagonal can be out of alignment or causes the focuser tube to flex out of alignment and you can get it all collimated up and then try it out at night and find that it is out because things flexed. 

 

       - Dave 


  • Van Do9:3 likes this

#14 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 31 March 2020 - 09:34 PM

Apologies for the delayed update. Made a mask with 140lb water color paper. The drafting compass pierced a pinhole in the center which was very useful as a bright centering target. Slipped  in the collimating eyepiece and rotated it so the reflective flat captured the bright sunlight filtering in from the window.

 

Peering through the eyepiece pinhole, I could see a distinct reflection of the flat to the left of the objective center and a dimmer reflection on the right. It was pretty cool to see the flat reflections move as I adjusted the push/ pull screws of the cell. This white paper on refractor collimation was very instructive, link.  After a few minutes, the reflections overlapped at center. 

 

E4173AC5-BF29-41C1-9E9D-3C7FC47BF0AD.jpeg

 

AB268548-8B0D-424C-B875-55331EB91094.jpeg
 

BD264F7C-0869-47FA-97E9-A161A20A56DB.jpeg

 

B52B0830-8966-45B5-B16A-64B7C2946F56.jpeg

 

Sadly, clouds and rain so no star tests tonight. 

 

 


  • deepwoods1, PawPaw and Kasmos like this

#15 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 01 April 2020 - 08:39 AM

 Excellent ! With the interference rings centered and the lens collimated I'm sure it will give an excellent image. If the scope had a soul I'm sure it is very happy that you are taking good care of it and it will soon it will  be under the stars vs living in a moldy box in some dark basement.

 

              - Dave 


  • PawPaw and Van Do9:3 like this

#16 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 01 April 2020 - 09:27 AM

Thank you Dave for your kind words. I am extremely grateful for yours, and other wonderful CN community members, advise and consideration, in restoring this wonderful Tasco.

 

You are right, there is a very satisfying feeling bringing these classics back to life. No matter how little or much that we spend on acquiring these telescopes, to me, it’s a priceless experience because I learn from fellow amateur astronomers, and experiment and gain hands on experience. Life is learning and something we can share.  
 

Again, many sincere thanks for your insight and help. Will report on the night observations. Looking clear and beautiful today. 
 

Cheers,

 

My


  • PawPaw likes this

#17 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 01 April 2020 - 10:59 AM

 The Tasco is great double star scope., Check out h3945 in Canis Major which is the "Winter Albireo"  It is very pretty double star of  orange and blue colors There is also Castor  and Rigel Rigel is good test of seeing and your optics.

 

                  - Dave  


  • Van Do9:3 likes this

#18 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 01 April 2020 - 11:12 AM

Dave, 

 

Thank you for the double star objects. These sound interesting and are not ones I have observed.  Would you know what number Tasco this telescope is? I don’t see any number on the labels. 

 

Best,

 

My



#19 PawPaw

PawPaw

    Mariner 2

  • *****
  • Posts: 218
  • Joined: 05 Jan 2013
  • Loc: West Central Missouri

Posted 01 April 2020 - 11:57 AM

Apologies for the delayed update. Made a mask with 140lb water color paper. The drafting compass pierced a pinhole in the center which was very useful as a bright centering target. Slipped  in the collimating eyepiece and rotated it so the reflective flat captured the bright sunlight filtering in from the window.

 

Peering through the eyepiece pinhole, I could see a distinct reflection of the flat to the left of the objective center and a dimmer reflection on the right. It was pretty cool to see the flat reflections move as I adjusted the push/ pull screws of the cell. This white paper on refractor collimation was very instructive, link.  After a few minutes, the reflections overlapped at center. 

 

 

Any suggestions on where to find a collimating eyepiece like the one you show?  I guess it is possible to make one?   Very good post!


  • Van Do9:3 likes this

#20 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 01 April 2020 - 01:08 PM

Thank you Don. Surprisingly, several collimating eyepieces showed up on the CN and Astromart Classifieds. You will need to confirm if they work for a refractor:

 

https://www.cloudyni...ating-eyepiece/

 

https://www.cloudyni...to-choose-from/

 

I like this one:
https://www.cloudyni...ser-collimator/

 

This is the one I have:

8441561F-BFB0-4BAC-A2C8-81B6E1402C12.jpeg

Again, confirm with the seller that it also works in a refractor. 
 

Good luck,

 

My



#21 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 01 April 2020 - 01:10 PM

Any suggestions on where to find a collimating eyepiece like the one you show?  I guess it is possible to make one?   Very good post!

 They are called  cheshire eyepieces. you can get them off of ebay . Ebay also has laser collimators for not much money. If you get laser collimator make sure to test that it correctly aligned by splnning it in a V block and watch the position of the laser dot a wall  a couple of feet away. It should not move. https://www.ebay.com...L0AAOSwBt5ZN2CL

 

         - Dave 


  • Van Do9:3 likes this

#22 PawPaw

PawPaw

    Mariner 2

  • *****
  • Posts: 218
  • Joined: 05 Jan 2013
  • Loc: West Central Missouri

Posted 01 April 2020 - 01:49 PM

Dave....Which do you prefer cheshire or laser?

 

Don



#23 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,313
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 01 April 2020 - 07:27 PM

Dave....Which do you prefer cheshire or laser?

 

Don

 I prefer a laser with the Cheshire like 45° cut out since I can use it on a Newtonian, Cass. my Schupmanns ,  my Schiefspeigler  or my refractors. WIth a refractor I do the mask setup  to check the focuser and then point the scope at  a wall without the mask  and look to see if I have multiple spot or not. 

  I have one like this https://www.ebay.com...-4AAOSw3-xdb6Vy

  No matter what laser collimator you buy check to be sure it is correctly aligned. It does no good to have an  alignment tool that is out of alignment  itself  Almost all the ones  I have checked have been out. I mount mine in a lathe and project the beam onto a wall about 10' away. I then rotate the chuck  holding the collimator by hand  If it is correctly aligned the spot will stay stationary. What I usually find is that the spot will make a circle sometime as large as 6" in diameter. I mark out the circle that the laser is tracing and estimate it's center. Then I adjust the laser to move the spot closure  to center by 1/2 the diameter and rotate the laser again. It takes a couple of tries but you can adjust it so the runout is no more than the diameter of the laser spot.  There are usually three aligned screw on the barrel of the laser and most of the time they are cover over with glue or wax so you have the dig that out to get the heads of the screws.  

 

           - Dave 


Edited by DAVIDG, 01 April 2020 - 07:27 PM.

  • PawPaw likes this

#24 Van Do9:3

Van Do9:3

    Ranger 4

  • *****
  • topic starter
  • Posts: 320
  • Joined: 02 Sep 2018
  • Loc: Charlotte, NC

Posted 02 April 2020 - 08:20 AM

The focuser was in terrible need of degrease, clean, and grease. I did this maintenance late yesterday so by the time I got under the stars there was only a 5 minute window for observing before the blanket of clouds rolled in. Yes, I have angered the celestial gods. 
 

I did a quick star test on a bright and dim star that were visible. Both showed airy disks in and out of focus and then bright pin points. I did notice the center half of the field of view was the nice deep darkness of space but it seemed the outer half appeared a little dimmer. Again, only 5 minutes to view so will need to spend more time observing. But is this possibly due to pinched optics with the retainer ring too tight? Or perhaps glare from the first quarter moon? 
 

The focuser was a little jerky and did not move smoothly. I used Super Lube but do I need to give it more time and several full movement for the Super Lube to set in?
 

Thank you for your advise and hope to have better observations tonight. 
 

My



#25 PawPaw

PawPaw

    Mariner 2

  • *****
  • Posts: 218
  • Joined: 05 Jan 2013
  • Loc: West Central Missouri

Posted 02 April 2020 - 08:38 AM

"I did a quick star test on a bright and dim star that were visible. Both showed airy disks in and out of focus and then bright pin points. I did notice the center half of the field of view was the nice deep darkness of space but it seemed the outer half appeared a little dimmer. Again, only 5 minutes to view so will need to spend more time observing. But is this possibly due to pinched optics with the retainer ring too tight? Or perhaps glare from the first quarter moon?"

 

I have learned the hard way that letting your instrument acclimate (cool down) is paramount to good visual results this includes your eyepieces.   I give mine at least 1 hour.  This time of year you can setup 1 hour before twilight without absorbing too much heat from the sun.  Sometimes I throw a white sheet over my scope to keep the surfaces from absorbing heat in the early evening.  My guess on half of your fov having different contrast is a nearby bright object.


Edited by PawPaw, 02 April 2020 - 08:39 AM.

  • Van Do9:3 likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics