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A TELRAD story to TEL


stolenfeather
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I have had my 10" Sky-Watcher for many years now and its accompanying buddy, the TELRAD.  The other day, when I was sleeping, I heard a "thump" which woke me up with a start.  I made my way to the location of the noise to find out that my finderscope (TELRAD) had fallen off my telescope.  I purchased a double sticky tape and reapplied it to the scope but after a recent romp amongst the stars, saw that my TELRAD had undergone the same fate.   This time, however, the TELRAD fell off of the telescope and because of the dangling tape, actually landed on my primary mirror with a loud "thud"!  I nearly had a heart attack!  Was the mirror cracked? 

NO. :rolleyes:

I was quite surprised with this outcome since the TELRAD seemed quite sturdy when I glued it with the double-glue tape.  I think I might have taken my telescope outside in the cold too soon after applying it to the scope (I waited about 5 minutes).  Tell me, what is the best way to re-affix the TELRAD to my telescope?  Thank you for all of your help.

Isabelle

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Thank you for coming around Alan.  I was so relieved when I saw that the mirror was intact.  I wonder how fragile it really is?  Usually, a double stick tape works right?  I guess I should be more patient the next time I take it out.  Apply the TELRAD one night and wait till the next night to use it.  I'm sure that 24 hours will be sufficient but I am afraid of it falling unto my primary mirror once more.

Isabelle

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Oh my gosh!  I just picked up my TELRAD to see where I can put the screws on and....  well, it's not normal that something is loose in there is it?  I guess something did break and it was NOT my primary mirror.  The mirror on the bottom under the light seems to have fallen off.  I guess I will have to glue this as well.  Oh man...  would it be simpler just to purchase a new one?

Isabelle

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Ha!  Screws it is!  I don't know why I was "shying away" from something permanent!  Thanks!

Isabelle

Remember to keep the OTA horizontal and use a piece of paper/ card to shield the mirrors from the metal swarf ;)

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Before reapplying with double sided tape, make sure all surfaces are free of dust and greasy residue. Clean with something like ascetone or nail polish remover being careful not to get any near your optics. After applying the telrad, put a large "cable tie" (or join a few smaller ones) around it as a kind of belt and braces on the off chance it comes off again. don't make the mistake of buying "budget" double sided tape. you get what you pay for :). hope this helps.

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Thank you Scott.  I did indeed clean the area before applying the double sided tape.  A cable tie is a great precaution and I should have thought of it sooner.  I am lucky that my mirror suffered no damage.  The double-sided tape that I purchased was the most expensive one at the store,  I will try again using your precautions but I first have to fix the TELRAD since it seems that the small mirror under the red light has come off.  Probably due to falling twice I'm sure.  I will also wait a full 24hours before heading out into -30m (or so) temperatures.

Isabelle

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Thank you for coming around Alan.  I was so relieved when I saw that the mirror was intact.  I wonder how fragile it really is?  Usually, a double stick tape works right?  I guess I should be more patient the next time I take it out.  Apply the TELRAD one night and wait till the next night to use it.  I'm sure that 24 hours will be sufficient but I am afraid of it falling unto my primary mirror once more.

Isabelle

Just to be clear - I trust you were using double sided foam tape? There are many types available (in Europe), with various strengths and some advertised as indoor, outdoor and 'permanent'. Brands like 'No more nails' or 'Ni clou ni vis'. Clearly you need to use the strongest, outdoor type, and don't forget to clean the tube surface and the part of the Telrad base where the tape will adhere with methylated spirits or isopropyl alcohol.
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As I was writing this I noticed this has already been suggested  - consider reinforcing the telrad base plate with plastic tie-wraps (cable ties) widely available, such as through Amazon etc. You will need to combine a few to wrap around - encompass the circumference of the o.t.a. A simple, cheap and secure solution to the very cold temperatures that you are experiencing, which may be affecting the glue on the sticky tape.

Edited by scarp15
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  • 4 weeks later...

Thank you for your input Michael.  Fortunately, I was easily able to screw my Telrad in a few weeks ago.  However, with this cold spell we are under, I don't think I will be heading out any time soon.  This -40 prison has to stop!

Isabelle

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I have to tel you Michael, I am really looking forward to spring.  I have a couple of weeks off at the end of April and planning in going somewhere SUNNY and WARM!

Isabelle

Hey Isabelle...for somewhere warmer I suggest going south...like down in my neighbourhood.

it has been a balmy -25C more often than not!

Nice that you got the Telrad thing under control.

I never had an issue myself at a temp. -28c.

Here's to an early spring...like maybe JUNE!!!

*L*

Regards

Bob

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