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  #221  
Old 15-01-2019, 01:39 PM
darkage (Gareth)
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Awesome project and amazing build quality. Dare I say how much did this end up costing you ?
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  #222  
Old 16-01-2019, 11:53 AM
Stefan Buda
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Quote:
Originally Posted by Atmos View Post
Itís fantastic to see this coming along so well Stefan!

If you do want to test out a larger sensor than the QHY8 I have an ASI094 you could borrow; Full Frame 36.3mp sensor.
Thanks Colin for the offer, but first I want to make a new front end with hefty linear bearings. I managed to come up with a design that stays within the original physical envelope.

Quote:
Originally Posted by darkage View Post
Awesome project and amazing build quality. Dare I say how much did this end up costing you ?
Thanks Gareth,
It cost less than an equivalent size Newtonian built with off the shelf components, plus a few hundred hours of labour.
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  #223  
Old 20-01-2019, 02:13 PM
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A good looking scope that performs well. Congrats
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  #224  
Old 29-01-2019, 07:57 PM
Stefan Buda
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Originally Posted by Troy View Post
A good looking scope that performs well. Congrats
Thanks Troy.

I'm about one month behind with this project, but finally ready to take it to a dark sky location.
I made a completely new/redesigned front end (focuser + spider assembly) and it seems to work incredibly well. Visually I can't detect any image shift when I reverse focusing direction. Maybe the camera will see a couple of pixels but it won't be an issue. It would be very interesting to hear from Diego about his super duper secondary focuser in this regard.
I also made the dew shield and rigged up a guide scope.
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  #225  
Old 10-02-2019, 12:05 PM
Stefan Buda
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I did take the scope to a dark sky location for testing but I had to evacuate the place, because a total fire ban was issued for the area, before I had a chance to capture a good image set. However I did a number of tests and I'm very happy with the new front end. The focuser has a backlash of only 4 or 5 steps and the image shift is so small that I had to turn off the drive and capture star trails, while pushing the focusing buttons back and forth, to make it show up as a discontinuity on the trails.

The only issue I had was the inadequate guiding. PHD was producing an oscillation index of half a pixel, which at the CDK focal plane contributed about two extra pixels to the star sizes. The guide scope is less than a third the focal length of the main OTA. So I decided to knock up an OAG for the next test and try to improve the PHD settings in a way that will stop it from trying to chase the seeing. It will be interesting to see if my old EQ6 mount can deliver.

On another front I entered all my notes into Excel tables and worked out a very detailed costing. It turns out that the OTA, including dovetail plate and camera adaptors, contains exactly 280 parts, down to the last screw.
Calculating with a rather low hourly rate, the price worked out to $8805 including GST but without the focuser control box and dew shield. The controller will take the price to around the $9000 mark.

I would like to hear some feedback on what you guys think about commercial viability at this price. Keep in mind that this is a very user friendly, compact and capable instrument without collimation/field flattener/focuser nightmares.
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  #226  
Old 10-02-2019, 12:59 PM
AstroApprentice (Jason)
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Full specs

Hi Stefan,
The scope looks amazing! Could you please list the full specs, including optical parameters, dimensions, weight etc?
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  #227  
Old 10-02-2019, 01:08 PM
glend (Glen)
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Stefan, that figure is your cost right? So what profit bargain are you going to put on your materials, effort, etc? Given usual retail markup, I suspect you would need to charge $15k minimum.
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  #228  
Old 10-02-2019, 01:44 PM
Stefan Buda
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Quote:
Originally Posted by AstroApprentice View Post
Hi Stefan,
The scope looks amazing! Could you please list the full specs, including optical parameters, dimensions, weight etc?
Aperture 250mm
Focal Length 1450mm
f:5.8
Fully Corrected Flat Field Diameter 42mm
Secondary Obstruction 50%
Quartz overcoated mirrors
Broadband AR coated lenses
Back Focal Length (From Field Rotator to Focal Plane) 133mm
OTA Diameter 299mm
OTA Length (without Field Rotator) 496mm
OTA Weight (including Rails, Field Rotator, Dovetail Plate and Adaptors) 10Kg
Built in primary and secondary heaters

Quote:
Originally Posted by glend View Post
Stefan, that figure is your cost right? So what profit bargain are you going to put on your materials, effort, etc? Given usual retail markup, I suspect you would need to charge $15k minimum.
I did not apply any mark-up for design and development cost recovery because I would have made this instrument anyway for my own use, and I wanted to make the price as affordable as possible. If I start making them for sale, then I will have to find ways of making them more efficiently in order to recover those initial costs.
Just to clarify: The Price I worked out includes both the labour and the cost of materials.
Also no retail pricing applies because I do not intend to make them available for retail. At least initially I intend to make no more than a couple per year as I have commitments in the laser industry.

Last edited by Stefan Buda; 11-02-2019 at 07:45 AM.
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  #229  
Old 10-02-2019, 03:34 PM
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Hi Stefan,

If you built a 12" or 14" I would be certainly interested. I expect the price would be reflective of the size but I am interested.
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  #230  
Old 10-02-2019, 06:28 PM
Stefan Buda
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Hi Paul,

One of the reasons for 10" aperture is that my machinery is limiting me to that size. A larger one would require outsourcing parts, with all sorts of quality control and cost issues.
Also I think that there is a bit of a gap in the market at the moment for portable 10" astrographs.
This one travels nicely on the back seat with room left for an Esky.
So, I'm afraid I can't commit myself to designing a larger one at this stage, but who knows what the future will bring.
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  #231  
Old 10-02-2019, 06:46 PM
AstroApprentice (Jason)
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CDKs

Hi Stefan,
Just wondering if you could comment on how you think your design compares to other CDKs of same aperture? I note yours has faster f ratio than these two:
http://www.hubbleoptics.com/cdk.html#_
http://agoptical.com/10-imaging-dall-kirkham/

Also, Whatís the central obstruction %?
Thanks.


[QUOTE=Stefan Buda;1416138]Aperture 250mm
Focal Length 1450mm
f:5.8
Fully Corrected Flat Field Diameter 42mm
Back Focal Length (From Field Rotator to Focal Plane) 133mm
OTA Diameter 299mm
OTA Length (without Field Rotator) 496mm
OTA Weight (including Rails, Field Rotator, Dovetail Plate and Adaptors) 10Kg
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  #232  
Old 11-02-2019, 08:16 AM
Stefan Buda
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[QUOTE=AstroApprentice;1416188]Hi Stefan,
Just wondering if you could comment on how you think your design compares to other CDKs of same aperture? I note yours has faster f ratio than these two:
http://www.hubbleoptics.com/cdk.html#_
http://agoptical.com/10-imaging-dall-kirkham/

Also, Whatís the central obstruction %?
Thanks.

I added a few more things to the specifications list.

My CDK design is 1.9 times faster than the Hubble one and 1.33 times faster than the AG Optical.
Mine is significantly lighter and more compact than those.
Mine has larger central obstruction than the Hubble and smaller than the AG.
My design is limited to 42mm diagonal sensors, the others were designed to work with larger ones.
Mine has built in heaters while for those it is optional extra.
Mine uses a secondary focuser, allowing a very clean, rigid and precise imaging train.
Mine comes with a precision camera rotator while the others have it as optional extra.
I can't comment about the mechanical build quality for those, but mine is as good as it gets.
Last but not least my price seems to be better too and you are dealing with a local manufacturer that is eager to help you out if you get stuck.
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  #233  
Old 12-02-2019, 09:54 AM
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strongmanmike (Michael)
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[QUOTE=Stefan Buda;1416235]
Quote:
Originally Posted by AstroApprentice View Post
Hi Stefan,
Just wondering if you could comment on how you think your design compares to other CDKs of same aperture? I note yours has faster f ratio than these two:
http://www.hubbleoptics.com/cdk.html#_
http://agoptical.com/10-imaging-dall-kirkham/

Also, Whatís the central obstruction %?
Thanks.

I added a few more things to the specifications list.

My CDK design is 1.9 times faster than the Hubble one and 1.33 times faster than the AG Optical.
Mine is significantly lighter and more compact than those.
Mine has larger central obstruction than the Hubble and smaller than the AG.
My design is limited to 42mm diagonal sensors, the others were designed to work with larger ones.
Mine has built in heaters while for those it is optional extra.
Mine uses a secondary focuser, allowing a very clean, rigid and precise imaging train.
Mine comes with a precision camera rotator while the others have it as optional extra.
I can't comment about the mechanical build quality for those, but mine is as good as it gets.
Last but not least my price seems to be better too and you are dealing with a local manufacturer that is eager to help you out if you get stuck.
Holy cow, now that is a compelling and convincing sales pitch

Mike
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  #234  
Old 12-02-2019, 01:17 PM
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multiweb (Marc)
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Quote:
Originally Posted by Stefan Buda View Post
Also I think that there is a bit of a gap in the market at the moment for portable 10" astrographs.
Agree. These should sell like hot cakes.
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  #235  
Old 13-02-2019, 08:02 AM
Stefan Buda
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Thanks Mike and Mark for the feedback.
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  #236  
Old 13-02-2019, 01:23 PM
bratislav (Bratislav)
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You should add that :

- primary is precision edge ground with zero wedge, and will never require collimation after it is factory assembled
- no tools of any kind are required for secondary collimation, just fingertips
- both primary and secondary are heated and can be kept dew free, greatly enhancing the longevity of coatings
- secondary focusing combined with ultra rigid back plate means no flexure/tilt whatsosever, even with heaviest cameras, off axis guiders, adaptive optics devices and filter wheels

and most importantly:
- guaranteed optical quality, with every unit tested via intereferometry as well as Roddier on real sky. No ifs, buts or excuses of any kind
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  #237  
Old 13-02-2019, 03:08 PM
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Atmos (Colin)
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For the quality of what you’re making it’s a very good price Stefan.
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  #238  
Old 13-02-2019, 08:21 PM
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Having seen the scope Stefan has built, I can categorically say itís a very impressive instrument and way above anything commercially available. Everything is over engineered.

Stefanís passion for making impressive optical instruments is second to none and he recently completely refurbished and rebuilt a second hand scope for me to take the instrument to another level.

To top it off, Stefan is a great guy who will go out of his way to help others in the amateur astronomy scene and above and beyond just making something for them.

John K.
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  #239  
Old 13-02-2019, 09:09 PM
Stefan Buda
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Quote:
Originally Posted by bratislav View Post
You should add that :

- primary is precision edge ground with zero wedge, and will never require collimation after it is factory assembled
- no tools of any kind are required for secondary collimation, just fingertips
- both primary and secondary are heated and can be kept dew free, greatly enhancing the longevity of coatings
- secondary focusing combined with ultra rigid back plate means no flexure/tilt whatsosever, even with heaviest cameras, off axis guiders, adaptive optics devices and filter wheels

and most importantly:
- guaranteed optical quality, with every unit tested via intereferometry as well as Roddier on real sky. No ifs, buts or excuses of any kind
Thanks Bratislav,
I didn't want to make the reply too long.
Yes, basically it is possible to have the primary removed and then put back without upsetting collimation.
The mirror coatings are not quite as reflective as the multilayer dielectric coatings claimed by the other brands, but the protected aluminium coatings, in mine, can be redone while for the others it's the end of the road if they deteriorate.

Quote:
Originally Posted by Atmos View Post
For the quality of what you’re making it’s a very good price Stefan.
Thanks Colin for the feedback.

Quote:
Originally Posted by John K View Post
Having seen the scope Stefan has built, I can categorically say it’s a very impressive instrument and way above anything commercially available. Everything is over engineered.

Stefan’s passion for making impressive optical instruments is second to none and he recently completely refurbished and rebuilt a second hand scope for me to take the instrument to another level.

To top it off, Stefan is a great guy who will go out of his way to help others in the amateur astronomy scene and above and beyond just making something for them.

John K.
Thanks John for the kind words.

Last edited by Stefan Buda; 18-02-2019 at 05:56 AM.
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  #240  
Old 15-02-2019, 08:37 AM
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traveller (Bo)
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Quote:
Originally Posted by John K View Post
Having seen the scope Stefan has built, I can categorically say itís a very impressive instrument and way above anything commercially available. Everything is over engineered.

Stefanís passion for making impressive optical instruments is second to none and he recently completely refurbished and rebuilt a second hand scope for me to take the instrument to another level.

To top it off, Stefan is a great guy who will go out of his way to help others in the amateur astronomy scene and above and beyond just making something for them.

John K.
I will second what John said. Stefan is a all round nice guy with an designer's eye for detail and an engineer's demand for precision.
I've been following this thread and it's an impressive piece of work!
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