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Equipment Discussions >> Cats & Casses

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pdfermat
scholastic sledgehammer
*****

Reged: 11/12/07

Loc: Wisconsin
Cheap but acceptable diagonal? new
      #6077727 - 09/12/13 09:04 PM

I'm looking for an affordable diagonal to use for visual use in my c8. Eventually I'll be using it almost entirely for ap, but while I learn the in's and out's of the mount (and researching/saving money for a ccd), I'll be doing a lot of visual. I'd like to purchase a diagonal that will be acceptable for visual use, but won't break the bank, since I don't see it getting much use once I'm full-on ap.

Any suggestions would be very welcome. Will $50 get me home?


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pdfermat
scholastic sledgehammer
*****

Reged: 11/12/07

Loc: Wisconsin
Re: Cheap but acceptable diagonal? new [Re: pdfermat]
      #6077730 - 09/12/13 09:08 PM

I should mention that my c8 ota currently has a 1.25" visual back, and that I'm looking for (I think) a "refractor style" 1.25" diagonal, since it would be able to easier accommodate the variety of ep positions my mount (Orion Atlas) will put it in.

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shawnhar
Post Laureate
*****

Reged: 06/25/10

Loc: Knoxville, TN
Re: Cheap but acceptable diagonal? new [Re: pdfermat]
      #6077738 - 09/12/13 09:14 PM

http://www.cloudynights.com/classifieds/showproduct.php?product=87347&sor...
35 bucks


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pdfermat
scholastic sledgehammer
*****

Reged: 11/12/07

Loc: Wisconsin
Re: Cheap but acceptable diagonal? new [Re: shawnhar]
      #6077753 - 09/12/13 09:21 PM

I saw that, as well as the cheap Orions, but I'm worried if those are the diagonals people say to immediately discard upon receiving your new scope. I don't need Televue quality, but I also don't want something that is going to be the glaring weak link in my optical train.

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Whichwayisnorth
Pooh-Bah
*****

Reged: 07/04/11

Loc: Southern California
Re: Cheap but acceptable diagonal? new [Re: pdfermat]
      #6077945 - 09/12/13 11:04 PM

http://store.explorescientific.com/replacement299reflectivityesdiagonal.aspx

Get a 2 inch visual back for your OTA. The diagonal comes with a 2" to 1.25" converter so you can use 1.25" eyepieces.


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*skyguy*
Carpal Tunnel
*****

Reged: 12/31/08

Loc: Western New York
Re: Cheap but acceptable diagonal? new [Re: pdfermat]
      #6078000 - 09/12/13 11:31 PM

If you want cheap but acceptable ... try one of these star diagonals from Telescope Warehouse on eBay:

Astrovisioneer Diagonal


Meade deluxe economy star diagonal

I've actually tested the Meade Deluxe Economy Diagonal and was surprised at how good it was. Collimation was spot on and when star tested at 220X against a much more expensive diagonal ... I couldn't detect any difference! However, the housing is 100% plastic, so I wouldn't want to use it with any heavy eyepieces!

BTW ... Telescope Warehouse is a good company to do business with ... orders are promptly shipped and arrive within a few days after placing them.


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barbarosa
scholastic sledgehammer


Reged: 04/11/10

Loc: "lamorinda", CA
Re: Cheap but acceptable diagonal? new [Re: pdfermat]
      #6078146 - 09/13/13 01:49 AM

Quote:

...I'm worried if those are the diagonals people say to immediately discard upon receiving your new scope.




People who write that about the stock Celestron diagonal are, and not just in my opinion, seriously overstating the alleged flaws in this prism diagonal. I sometime wonder if they understand how a prism works and why it might be accepable for your SCT or my smaller and larger versions. (Remark not applicable to any CN memeber in good standing--only intended for emphasis). We should ask why Celestron hasn't switched to a 1.25" mirror? There are many servicable and cheap versions made in China.

Read this brief report by Gary Hand

Two inch EPs change the game---a two inch prism is expensive. And for what it might be worth, I have a TV diagonal and really don't see much gain when using 1.25" EPs. But I wasn't much good with the difference between tabaco notes and rasberry-earthy notes in wine.


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T1R2
Pooh-Bah


Reged: 06/11/13

Loc: NeverWhere
Re: Cheap but acceptable diagonal? new [Re: pdfermat]
      #6078160 - 09/13/13 02:19 AM



As for using them visually, I really like my $40 celestron 1.25 prism, it has a great view through it, just as good if not better than my $189 AT Quartz 2", though sometimes you have to adjust the flat spring to get them aligned properly.

Edited by T1R2 (09/13/13 02:20 AM)


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brianb11213
Postmaster
*****

Reged: 02/25/09

Loc: 55.215N 6.554W
Re: Cheap but acceptable diagonal? new [Re: barbarosa]
      #6078211 - 09/13/13 04:26 AM

Quote:

We should ask why Celestron hasn't switched to a 1.25" mirror?



The main issue with the cheapo 1.25" prism diagonal supplied with Celestron SCT OTAs (apart from the restriction on the FOV compared with a SCT threaded diagonal, or a 2" refractor diagonal in a 2" fitting visual back) is that the eyepiece retaining screw rapidly wears its thread. Optically it's not great, but it is OK, unless you want to image in the ultra violet, and for imaging you really don't need a diagonal at all.

Personally I don't see why Celestron package a cheap diagonal and a cheap eyepiece when they could package something far more useful instead (active cooling fans, a corrector plate dew heater strap and, most importantly of all, a dew cap) but, as usual, you get what the marketing department wants to dump on you, not what you might find useful.


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Jon_Doh
professor emeritus


Reged: 09/16/11

Loc: On a receiver's back
Re: Cheap but acceptable diagonal? new [Re: brianb11213]
      #6078366 - 09/13/13 09:01 AM

Here is a cheap one: http://www.amazon.com/gp/offer-listing/B0078V9F7I/ref=dp_olp_0?ie=UTF8&co...

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Locoman
scholastic sledgehammer
*****

Reged: 03/09/09

Loc: Abilene, Kansas
Re: Cheap but acceptable diagonal? new [Re: pdfermat]
      #6078507 - 09/13/13 10:43 AM

$20.00 more but! Link . Or $10.00 more but! Link

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pdfermat
scholastic sledgehammer
*****

Reged: 11/12/07

Loc: Wisconsin
Re: Cheap but acceptable diagonal? new [Re: Locoman]
      #6078511 - 09/13/13 10:47 AM

I think those might be the winner. It seems they get acceptable reviews from a number of different sources.

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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Cheap but acceptable diagonal? new [Re: barbarosa]
      #6078520 - 09/13/13 10:53 AM

Quote:


People who write that about the stock Celestron diagonal are, and not just in my opinion, seriously overstating the alleged flaws in this prism diagonal.




I agree.

Optically, the Orion/Celestron 1.25 inch prism diagonals are plenty good, mechanically, they have their issues but are certainly acceptable mechanically. I find the corresponding Orion/Celestron 1.25 inch mirror diagonals are often miscollimated (easily fixed) but the prism diagonals are quite good in this regard.

The diagonal is close to the focal plane, it's flatness is not as critical as an optical component that distant from the focal plane (Newtonian Secondary) since any part of the image only sees a small portion of the diagonal.

Jon


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Joe Aguiar
Carpal Tunnel
*****

Reged: 02/10/07

Loc: none of your buss
Re: Cheap but acceptable diagonal? new [Re: Jon Isaacs]
      #6078555 - 09/13/13 11:21 AM

i was gonna say get a 2" model and it comes with the 1.25" adptor to use the ep you already have,and you can use 2" ep as well.
You can find these good quailty ones with 99% dielectric for like $80 or so, but if you wanna stick to the 1.25" visual back with a 1.25" diagonal get a astro teck used model 99% dielectric you may find them just abit over $50 but will be worth it.
joe


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Cheap but acceptable diagonal? [Re: pdfermat]
      #6078574 - 09/13/13 11:35 AM

Get the GSO Quratz Dielectric with SCT threaded attachment.

http://agenaastro.com/gso-2-90-99-quartz-dielectric-sct-mirror-diagonal.html

You can but a refractor nosepiece for it, and swap it between the SCT and a refractor should you later add one to your stable.

- Jim


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T1R2
Pooh-Bah


Reged: 06/11/13

Loc: NeverWhere
Re: Cheap but acceptable diagonal? new [Re: jrbarnett]
      #6079813 - 09/14/13 04:43 AM

Whatever you get stay away from the 45* erect image diagonal their ok for terrestrial viewing, but not for astronomical, I stomped my brand new 45* into 100000000 pieces, because the supplier did not have a 90* hybrid that I wanted, so I got one of those to get me by until they came in, their useless for anything over 40* alt. and the stars all had 2 diffraction spikes shooting out the sides. Not good at all.

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