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#1 kcoles

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Posted 13 July 2020 - 06:25 PM

I'm gratified to find such a useful forum and to join. Briefly, I have several projects lined up and my current, um, focus is these mirrors (making them into telescopes will come a bit later):

 

1. A 6-inch f8 I started at the 2006 Delmarva workshop. It is polished out, but I had to leave the workshop before getting it fully figured.

 

Three mirrors from telescopes sold to me fairly cheap by a retired acquaintance:

2. 6-inch f/7, came with a home-made Dob tube but no base

3. 7-inch f/10, ditto

4. 12.5-inch about f/5 in a home-built truss Dob. Very rickety and out-of-line the one time I tried looking through it so I don't know how good the figure might be.

 

5. A mirror and mount from a 10-inch about f/6 that someone gave decades ago to the university where I teach science. The mirror was stripped at some point but has unknown figure. A very heavy steel OTA also, but I'm leaning to making this into a lighter Dob (no sign of the original GEM). This looks like it could have been a commercially made scope.

 

I've just finished making a tester and mirror stand from the plans on the Stellafane page, and I can see figures of some sort! (both Foucault and Ronchi) So far I've only set up and looked at the three smaller mirrors. All five are polished out, numbers 2-4 have degraded coatings that likely need to be removed and redone. So I have plenty to do but this summer and fall I have more time than usual to tackle it all. The first one at least needs figuring. I don't know about the others yet, but that is what the tester is for.

 

I'll post specific questions separately, but want to say thank you for all the good info I've already found here.

 

Ken

western Pennsylvania


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#2 jelloptic

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Posted 13 July 2020 - 07:06 PM

Welcome to the forum, Ken.  That's quite a line-up.  Indeed, start by assessing the surface figure of each mirror.  The fact that #2 thru 5 were coated means that someone thought that they were adequately figured.

regards,  kbl   



#3 kcoles

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Posted 13 July 2020 - 07:35 PM

Welcome to the forum, Ken.  That's quite a line-up.  Indeed, start by assessing the surface figure of each mirror.  The fact that #2 thru 5 were coated means that someone thought that they were adequately figured.

regards,  kbl   

 

That's exactly my thinking. I don't know what I'm doing yet, but mirror number 2 looked decent on the tester (like the photos in the books) and the coating is not too bad, so I plan to reassemble that OTA, lean it on a bush or something pointing at Polaris, and see how a star test looks.

 

I can see how this telescope making can reel one in! Cheers,

 

Ken



#4 kfiscus

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Posted 13 July 2020 - 09:17 PM

Welcome!  Post pictures of the stuff that you want advice on.



#5 Pinbout

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Posted 13 July 2020 - 09:50 PM

Where in pa are you?



#6 kcoles

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Posted 14 July 2020 - 09:53 AM

Pinbout, I'm between Johnstown and Pittsburgh. I've been a member of the big club in Pittsburgh (Amateur Astr. Assn. of Pgh., AAAP) for some years. A couple of the older members used to do a lot of telescope making and have offered to help, though they are not active on the internet. Under present circumstances we don't see each other in person very often.

 

kfiscus, I will include pictures as I get my feet on the ground - good suggestion. Thank you.

 

Ken


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#7 cuzimthedad

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Posted 14 July 2020 - 01:19 PM

Welcome to Cloudy Nights and the ATM forum Ken! A wealth of information is to be found throughout the site. Enjoy!




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