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

Which one?

  • Please log in to reply
11 replies to this topic

#1 stargazer32864

stargazer32864

    Ranger 4

  • *****
  • topic starter
  • Posts: 326
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 27 June 2020 - 10:36 PM

    Ok, I have a question about refractors. I know there are ones that have to be collminated. But which ones?? Triplett?? Doublet?? I'm not good at collmination, unless it's reflectors which is a piece of cake, but refractors are a new ballgame. I'm wanting to buy the new refractor that comes out on the Astronomics website, ( Astro-Tech 100mm EDL), but do I have to line up the lens? I have no experience in that.

 

~Robin



#2 Couder

Couder

    Mariner 2

  • *****
  • Posts: 224
  • Joined: 24 Feb 2014
  • Loc: Missouri Ozarks

Posted 27 June 2020 - 10:46 PM

I've hauled my 3", 4",  and 6"refractors from St. Louis area to Indiana, Chicago many times, Kentucky, all over St. Louis area many times, now we live in the Missouri Ozarks and I've hauled them back to Chicago and all over the area here and never had to collimate. If that tells you anything.



#3 Heywood

Heywood

    Apollo

  • -----
  • Posts: 1,247
  • Joined: 03 Jan 2009

Posted 27 June 2020 - 10:49 PM

A refractor is collimated at the factory and should never need to be collimated again unless it suffers a sharp blow during transport.  smile.gif

 

NOTE:  The correct word is "collimation," not "collmination."  "Collmination" is not a recognized word in the English language.


Edited by Heywood, 27 June 2020 - 10:53 PM.


#4 TOMDEY

TOMDEY

    Fly Me to the Moon

  • *****
  • Posts: 6,753
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 27 June 2020 - 11:20 PM

Yes to the above. A refractor should hold good alignment indefinitely, hopefully ~forever~ aka as long as it will matter to you. The one thing I check for (especially when buying used) is big dents or scrapes that might indicate that the OTA was dropped or suffered a severe blow. Ummm... and also any indication that previous owner(s) dismembered the objective assembly. Some ham-handed amateurs do that and can muck things up terribly. Look for internal signature finger prints, "cleaning" marks or chewed up alignment screws. Other than that... alignment of the objective cell to the tube itself can sometimes be tweaked into better centered/squared. I wouldn't go beyond that, unless I had the OTA in the lab, on an interferometer... which I have done!

 

So, that's really the big advantage of a nice refractor. Should never need tweaking. Reflectors, and catadioptrics, on the other hand... most of those need constant babysitting and adjusting. One exception is permanently-mounted in a good observatory, and treated with religious regard its entire life. That's actually the biggest reason I have my scopes in domes. Once good - always good!    Tom



#5 stargazer32864

stargazer32864

    Ranger 4

  • *****
  • topic starter
  • Posts: 326
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 28 June 2020 - 12:33 AM

I've hauled my 3", 4",  and 6"refractors from St. Louis area to Indiana, Chicago many times, Kentucky, all over St. Louis area many times, now we live in the Missouri Ozarks and I've hauled them back to Chicago and all over the area here and never had to collimate. If that tells you anything.

Yes, it does. Thank you. I won't be so scared now. If I have any problems, I will be back on here, seeking advice.



#6 stargazer32864

stargazer32864

    Ranger 4

  • *****
  • topic starter
  • Posts: 326
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 28 June 2020 - 12:34 AM

A refractor is collimated at the factory and should never need to be collimated again unless it suffers a sharp blow during transport.  smile.gif

 

NOTE:  The correct word is "collimation," not "collmination."  "Collmination" is not a recognized word in the English language.

Sorry, it was dark in the room when I typed it. Babysitting my granddaughter and she had to go to bed.
 



#7 SeattleScott

SeattleScott

    Cosmos

  • *****
  • Posts: 8,085
  • Joined: 14 Oct 2011

Posted 28 June 2020 - 04:29 AM

Doublets are less likely to need collimation tune up than triplet. Some brands don’t have collimation adjustments. Like Televue and Vixen.

Scott

#8 Eigen

Eigen

    Vostok 1

  • -----
  • Posts: 187
  • Joined: 26 Jul 2012

Posted 28 June 2020 - 05:15 AM

Doublets are less likely to need collimation tune up than triplet. Some brands don’t have collimation adjustments. Like Televue and Vixen.

Scott

I would say lens cell design trumps whether the lens is a doublet or triplet.

 

As an example, the old Borg doublets were notorious for losing collimation due to their light weight cells, while an oil-spaced triplet that is taped up with kapton, like a TEC140, will likely have its glass shatter before losing collimation.



#9 Rutilus

Rutilus

    Mercury-Atlas

  • *****
  • Posts: 2,581
  • Joined: 17 Dec 2010

Posted 28 June 2020 - 06:47 AM

I have always found doublet refractors easier to set-up than reflecting telescopes. I have a couple of

doublets that I set-up 40 years ago and they are still in perfect alignment even after rough handling.



#10 stargazer32864

stargazer32864

    Ranger 4

  • *****
  • topic starter
  • Posts: 326
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 28 June 2020 - 11:38 AM

I have always found doublet refractors easier to set-up than reflecting telescopes. I have a couple of

doublets that I set-up 40 years ago and they are still in perfect alignment even after rough handling.

That is so true. I'm planning on having a Dob reflector for DSO. A cass for planets and DSO. And I'm definitely getting at least two refractors for planet and luner observations. And somewhere down the line, after I have learned more, astrophotography.



#11 Echolight

Echolight

    Ranger 4

  • -----
  • Posts: 386
  • Joined: 01 May 2020
  • Loc: Texas

Posted 28 June 2020 - 01:26 PM

Got my C6R that was lost in transit for a month and came with a little dent in the tube and a bent ring bolt. But puts up perfect circles in my purely amateur star test.

I think collimation is good. Focuses to nice, tight, high contast images as far as I can tell.

Collimation, or the lack of need for it, is one of the reasons I started out with a large achro instead of an 8 or 10 inch dob.


Edited by Echolight, 28 June 2020 - 01:27 PM.

  • Heywood likes this

#12 Echolight

Echolight

    Ranger 4

  • -----
  • Posts: 386
  • Joined: 01 May 2020
  • Loc: Texas

Posted 28 June 2020 - 01:41 PM

That is so true. I'm planning on having a Dob reflector for DSO. A cass for planets and DSO. And I'm definitely getting at least two refractors for planet and luner observations. And somewhere down the line, after I have learned more, astrophotography.

I'm trying to keep my eventual final inventory of scopes down to three.

 

Started with the 6" f8 achro on a goto mount for the bortle 7.5 outer edge of the light dome backyard scope.

So far, this has been a great scope for planets, lunar, and bright stars. And will soon be expanding it's roll to include doubles and open clusters.

 

Now looking at buying an 80mm ED refractor on a lightweight manual mount for grab and go/quick look/widefield scope. 

 

And will probably eventually replace the old Nexstar 8 I bought while impatiently waiting on the AVX/C6R to show up. Thinkin an 8 or 10 inch solid tube dob for a grab and go to a dark site scope. The C8 just doesn't have the field of view to use without goto that I would want for a travel scope.

 

Thinkin my "astrophotography" will mostly be limited to snapshots with a phone or pawn shop DSLR. No stacking and photoshopping for me. At least no plans for it.


Edited by Echolight, 28 June 2020 - 01:45 PM.



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