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

my 10in f3.27 uncoated mirror test.

  • Please log in to reply
12 replies to this topic

#1 macleod

macleod

    Vostok 1

  • -----
  • topic starter
  • Posts: 195
  • Joined: 21 Sep 2014
  • Loc: Napier, New Zealand, 4110

Posted 22 March 2019 - 10:27 PM

In final stages of mounting my 6x point flotation cell to my OTA.Been testing uncoated mirror in hot bright daylight, looking at Yachts and people in the bay.The mirror is , to me amazing ! Of course I,m biased ,having achieved an 10in f3.27 19mm thick mirror that works very well, having only done an 8in f8 60yrs ago. And as an Octogenerian too - so much for the " old and greys", we still have a life, and can use it  !

Focus is sharp, and abrupt - despite not being properly collimated , as the mirror cell is only friction fitted to cell , until all eyepieces focus.My 24mm focuses sharply, as does my 14mm, but cannot get focus ( in daylight ) on my 6.7 and 4.7 eyepieces .Weather is clearing so I,ll try tonight .Not sure whether I have too much or too little" IN FOCUS " for the shorter f eyepieces. This mirror has real potential inspite of it,s short focal length , in fact I,d be pleased with it as a terrestial scope to look at cruise ships entering our port, and yacht races etc. So Danny and others, you have all done a great job of advising me inspite of my terrible Ronchi photos ! Thank you macleod.


  • davidpitre, Pinbout and Mike Spooner like this

#2 petert913

petert913

    Mercury-Atlas

  • *****
  • Posts: 2816
  • Joined: 27 May 2013
  • Loc: Portland, OR

Posted 22 March 2019 - 10:31 PM

It's gonna be a great one once you get the aluminum on it.  Keep us posted !



#3 TOMDEY

TOMDEY

    Soyuz

  • *****
  • Posts: 3797
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 22 March 2019 - 10:38 PM

Nice! Those are big exit pupils, though: 7.3mm at 35x and 4.3mm at 59x. So, bright daytime... would be using a lot less than the entire 10-inch of aperture. Night use, at higher mag, will be a more severe test.

 

Nevertheless - very good! I'm only 71 (going on 72) and still making telescopes, too.    Tom


  • Pinbout and Garyth64 like this

#4 macleod

macleod

    Vostok 1

  • -----
  • topic starter
  • Posts: 195
  • Joined: 21 Sep 2014
  • Loc: Napier, New Zealand, 4110

Posted 31 March 2019 - 03:03 AM

Frustrated by "new telescope curse" - beautiful warm days, but evenings clouded over, sometimes clearing early morning.However managed a few minutes tonight between banks of fast flowing alto- cirrus cloud.Generally stars look suitably sharp, and coma looks no worse than my f4.7 scope with a "top" mirror.I had to test before the mirror was acclimatised - to even get a view between the cloud. So called breakout looks same both sides of focus , although this was a rushed test and I,m NOT saying its a fair test.Did notice at higher power that OUTSIDE of focus the central shadow was very black, with one bright ring around it.However as I,ve said, all I can assume from this brief foray is - the scope focuses sharply, coma is not bad for f3.27 in my book, and the whole thing has promise.More tests when sky clears later in April !!

One "rave " I do have - the "offset "spider vanes are superb at holding the secondary firmly, and the Ross Sackett / Strock mirror holder design ( as shown on Pinbouts 3D design page) , is both very lightweight and easy to adjust, and holds collimation.Success story there ! I,m making an offset spider to hold my Astrosystems mirror holder on my other scope, I,m so rapped by them.More later, Macleod.



#5 ccaissie

ccaissie

    Surveyor 1

  • *****
  • Posts: 1718
  • Joined: 13 Sep 2010
  • Loc: Whitefield, Maine

Posted 01 April 2019 - 06:28 AM

You might try Ronchi at the eyepiece to get one more test input. Straight lines.  Should agree with other tests.  Check out the Solar system objects with the uncoated.


Edited by ccaissie, 01 April 2019 - 06:29 AM.

  • sopticals likes this

#6 macleod

macleod

    Vostok 1

  • -----
  • topic starter
  • Posts: 195
  • Joined: 21 Sep 2014
  • Loc: Napier, New Zealand, 4110

Posted 11 April 2019 - 04:01 AM

Well clear skies at last ! All my comments are subjective, in that I,m in no position to interpret star tests. So my 10in f3.3 mirror is , in my opinion a keeper, thank goodness.The mirror is UNCOATED.

Moon very sharp, mountain tips on terminator sharply silhouetted against dark sky background.Uncoated mirror reduced glare, so detail on lunar surface was spectacular.Orion Nebula extensive,much better than I thought it would be uncoated, and I could see all 4x trapezium stars at 100x . Similarly Eta Carina nebula was visible , and enjoyable.Scanning the Milky Way was fun and amazingly for f3.3 coma was not at all bad ! Not what I had been led to believe by any means. My simple cheap GSO Coma corrector ( modified as per above in pinned posts) cleaned it up nicely ! So much for " cheap Chinese optics" ! Attempts at star testing were "dismal". Mirror looked better outside of focus than inside, although the shadow of the secondary looked similar both sides. About all I can say - this is NOT the best mirror on the block, but it works to me very well visually up to 250x , however the view is pretty dim at this magnifcation uncoated, so really cannot fully judge.This mirror is 19mm float annealed glass, mounted on a 6x point cell in a 12in epoxied Sonotube.No signs of astigmatism fortunately.So what is my reaction to fast mirrors, after 6yrs using a 10in f4.7 Zambuto Dob, home built ? You obviously can,t compare the optics, Carl,s mirror is supurb on Planets and stars etc.But the f3.3 is still very good for wide field Milky Way cruising, and DSO hunting , and does NOT disappoint me in any way - in fact I get great satisfaction as an 83yr old , to think I made a fast thin mirror that works as well as this does, and it took only four months to grind/figure start to finish.The real test will be the Planets later in the year - I,m not getting up early morning in a NZ winter to view them ! However this scope was built for Deep Sky cruising and not Solar System stuff - the Zambuto is for that.

One thing I noticed immediately I used the fast optics was how CRITICAL focus is, it is right there, no " give and take " a fraction, its either in or out of focus sharply.In fact its at the edge of usefullness of my GSO Micro Edge focuser, but I,m leaving my Feathertouch on the Zambuto scope.So I,m happy with the mirror, and It,s off to be coated. Don,t think I,ll " be allowed" to make another one, as the house needs a touch up paint job, and guess whose doing it ! MACLEOD


  • PrestonE and Dale Eason like this

#7 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22412
  • Joined: 22 Feb 2010
  • Loc: Montclair, NJ

Posted 11 April 2019 - 06:01 AM

 

! Attempts at star testing were "dismal". Mirror looked better outside of focus than inside, although the shadow of the secondary looked similar both sides

is that with the cc in the focuser or not. 

 

what eyepiece, if it has a built in barlow, it will add correction to the reading.

 

 

and how far in / out did you place the eyepiece

 

too close to the caustic gives false readings, too far out is too insensitive.

 

 

similar CO but inside blown out? over HSA

 

10in f3.5 hsa.JPG


Edited by Pinbout, 11 April 2019 - 06:13 AM.


#8 tommm

tommm

    Messenger

  • -----
  • Posts: 421
  • Joined: 16 Dec 2015

Posted 11 April 2019 - 11:21 AM

Happy to see you enjoying it! That's what matters. Congrats!



#9 macleod

macleod

    Vostok 1

  • -----
  • topic starter
  • Posts: 195
  • Joined: 21 Sep 2014
  • Loc: Napier, New Zealand, 4110

Posted 11 April 2019 - 07:56 PM

Hi Danny, I tried star test just de- centering both ways until I got initial break out.Probably .5mm both ways. Used a 6.7mm ES eyepiece @ 123x. Could not get anything approaching your pics ! I,m not sure about my old eyes - I,ve just had Cataract surgery 4 weeks ago, corrected to infinity, and it has "changed my life ", literally. I can see amazingly into distance, and colours great. But in past out of fun / curiosity I,ve tried to star test my Zambuto mirror , but still got rubbish views ! I do recall clearly in 1965 when I was 30yr old and my eyes young , I star tested my own 8in f8 mirror, and clearly remember seeing several concentric rings as you show - but never managed it since. By way NO c.c when I tested.All I could get was the central black dot, and one bright ring . Thank you for taking an interest Danny, and all the advice you gave me, I really appreciated it. In the long run this optic does what I want deep sky, so I,ll get it coated.

Thank you Tommm, it,s been a great exercise , making a turntable first, then the mirror work. The testing Ronchi I had to learn, and Dannies help on using the lap edge to figure was a learning curve. I,d like to do another, but I have other less interesting maintenance jobs to do !! Thank you all , MACLEOD

ps :- the "Strock style" focuser is fantastic, so solid, easy to adjust and holds collimation. I have just replaced my Astrosystems spider with an offset job I made with a 2in x 2in block of aluminium drilled for the 3/8 bolt, and with 4x offset vanes.What a differance- solid as a rock, where the bolt on the original Astrosystems spider was a very sloppy fit in it,s hole in the spider, and was a curse to align! The 3/8 bolt was loose in the square section tube of the spider, and I was told to " just wedge it with toothpicks or matchsticks" ! Not very inspirational to say the least !.MACLEOD


  • Pinbout likes this

#10 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22412
  • Joined: 22 Feb 2010
  • Loc: Montclair, NJ

Posted 11 April 2019 - 09:55 PM

Btw 

 

this is more typical

 

med_gallery_106859_355_647849.gif



#11 macleod

macleod

    Vostok 1

  • -----
  • topic starter
  • Posts: 195
  • Joined: 21 Sep 2014
  • Loc: Napier, New Zealand, 4110

Posted 11 April 2019 - 10:31 PM

Yes Danny, thats about what I see, but centre about same size in and out - perhaps a small bit smaller inside. MACLEOD



#12 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22412
  • Joined: 22 Feb 2010
  • Loc: Montclair, NJ

Posted 12 April 2019 - 04:59 AM

That’s an imported 8” f6 about a 1/4~ overcorrected  in north great seeing. I should’ve used a 33% CO

 

theres a lot of star test images in the gallery under star test/ reflectors 



#13 Arjan

Arjan

    Viking 1

  • -----
  • Posts: 931
  • Joined: 21 Jan 2009
  • Loc: Netherlands

Posted 12 April 2019 - 08:01 AM

Macleod, congratulations, well done!


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