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Flattener 3" manufacturer ?

equipment optics accessories astrophotography
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#1 Astrofriend

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Posted 21 August 2016 - 03:58 PM

In the future I plan to add a bigger flattener to my TS 130mm (5.2")  APO refractor.

 

This Riccardo 2.5" flattener is what I have today:

http://astrofriend.e...-refractor.html

 

Very good quality but it can't handle a fullframe sensor, only up to about APS-H format sensors.

 

Now I'm thinking of this 3" flattener:

http://www.altairast...refractors.html

 

Does anyone know who is the manufacturer of this flattener where I can get more detailed data of it? This was the most important part of my question.

 

I have seen it under many different names, Altair, TS, Orion and maybe more.

 

I guess they are all of the same optical design but with difference in the camera adapter. Camera adapters can have variations in length (depending of what telescope they are adapted to) and have connection to M42 or M48. But I have also seen adaptors to the old medium format Pentax 67. There is also one derivate to RC telescopes, but maybe only the camera adapter that has a different length?

 

And is there anyone that use this flattener and can tell if the optical quality is good enough for todays high resolution sensors, fullframe or bigger format?

 

/Lars

 

 

 

 



#2 mfarrell

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Posted 22 August 2016 - 12:58 AM

Hi Lars,

 

I've made a few posts in the Refractor forum that may help you out:

 

http://www.cloudynig...q-85/?p=6475823

http://www.cloudynig...dslr/?p=5850002

 

Basically, I have both the large Riccardi reducer, as well as a 1.0x flattener made by William Optics which I believe is similar if not identical to the one you've referenced in your post.  My scope is a TMB130SS which at 130mm f/7 Triplet is similar if not identical to your TS version.

 

As you'll see in the posts I've reference, I've been able to get pretty good stars out to the corners of my full frame DSLR, so I suspect you may not have quite the right spacing for your setup.  In particular from looking at your webpage, you probably need to reduce your spacing slightly, since you tried 74.7mm which was worse than 73.2mm.  As good as the Riccardi is, it's still asking a lot to be able to get a 0.75x reduction on a full frame sensor with good stars in the corners.  My experience is that a good 1.0x flattener will give even better images in the corners. 

 

To answer your questions more directly,

  1. I don't know who actually manufactures the flattener, but I think WO may have been the first to bring it to market as the FLT flattener, assuming it is in fact the same optical design as the one marketed by Altair, Orion, etc.  I don't know if they still do, but at one time I believe WO stated it was designed by Thomas Back and matched to the WO FLT refractors also designed by Thomas Back.  This link for example: http://agenaastro.co...attener-68.html shows spot diagrams labeled with WO and TMB and repeats the claim in the item description.  See also http://www.williamop...ttener_spec.php
  2. Yes, I can confirm that this flattener works very well on a full frame sensor and 130mm f/7 refractor, assuming it is the same optical design as the WO flattener I have (which is roughly ~2009 vintage, although I purchased it used with my scope).

 

I hope this information is useful.

 

-Matthew


Edited by mfarrell, 22 August 2016 - 01:13 AM.


#3 Astrofriend

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Posted 22 August 2016 - 01:05 PM

Hi Matthew,

Very interesting to hear about the 3" flattener from someone who has it and use it.

 

Yes I know, a 2.5" flattener with reducer will not match my fullframe sensor, a lot of vignetting, even after my modification of camera adapters. But it come together with the telescope, a new Riccardi with 3" 0.75x  is very expensive.

 

I also could have some advantage of the Orion 3" flattener with none reducing (1x) which give me a better match of the pixelscale but less light. Very good to hear thet the 3" x1 flattener works so well. Just wonder, who is the manufacturer of this device, must be somewhere to fiend more information from them who made it.

 

Thansk a lot for the information you share !

 

/Lars


Edited by Astrofriend, 22 August 2016 - 05:39 PM.


#4 Astrofriend

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Posted 23 November 2016 - 02:31 PM

Today I got my new 3" flattener, very exiting. It looks very good with it's 68 mm lens opening.

 

 

Now a lot of works waiting to adapt it to my system. First i will do some test, then built a new bigger off-axis adapter. This will be slowly progress project. I will add some text and photos on my homepage for you who find it interesting to follow.

 

http://astrofriend.e...-flattener.html

 

I will come back here when I have more new things to tell.

 

/Lars



#5 Astrofriend

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Posted 28 November 2016 - 10:42 AM

Now I have come a bit further. I have disassembled my old adapters and flattener, veryfied what threads they have and start thinking of next step.

 

I must decide if I shall build it with an off-axis guding or a guide telescope, or maybe no guiding at all, instead a high precision mount.

 

But i take it step by step. Now I got to assemble it together so I can start test how it works and if the quality is enough to proceed with this new equipment.

 

I'm not sure how much DIY this will end up with, but as usual I think it will be a lot :-)

As usual I have tried to document what I do on my homepage if you find it interesting to follow:

http://astrofriend.e...-flattener.html


/Lars




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