Author Topic: Sharpstar 15028 reducer - tool  (Read 77 times)

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JohnH

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Sharpstar 15028 reducer - tool
« on: Nov 08, 2020, 11:45:39 »
My images from my 15028 show a definite coma. I have had a bash at refining collimation which has improved the look of my flat frames (less vignetting) but I haven’t tested it on real stars yet.

I have found a review in Sky & Telescope which suggests moving the reducer 1 - 2mm closer to the sensor. My problem is that the reducer screws into the focusser and requires a tool to remove it, when I received the telescope the tool was missing. I was told that someone had been performing an adjustment and the tool had disappeared.

The tool consists of two prongs which fit into corresponding holes which can be used to turn the reducer to unscrew it. I have tried a piece of bent fencing wire but that was too flexible.

Can anyone tell me what the two pronged thing is called and where I might get hold of one? Alternatively, has anyone a suggestion for making something which will do the job?

Thanks,

John

The Thing

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Re: Sharpstar 15028 reducer - tool
« Reply #1 on: Nov 08, 2020, 12:02:08 »
We're all guinea pigs in the laboratory of life. Better a fluffy guinea pig than a lab rat!
¯\_(ツ)_/¯ (Gallic shrug :))

JohnH

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Re: Sharpstar 15028 reducer - tool
« Reply #2 on: Nov 08, 2020, 13:51:23 »
Thanks,

I’ve immediately found and bought one.

John

NoelC

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Re: Sharpstar 15028 reducer - tool
« Reply #3 on: Nov 09, 2020, 12:27:07 »
A very interesting scope you have there John.  Lots of chat about loose screws, flopping mirrors and difficulty getting all the bits to be concentric on the forums as well as the correct spacing.  But they are talking in terms of +/- 0.3mm!:-
https://www.cloudynights.com/topic/663055-new-sharpstar-15028hnt-initial-impression-with-pics/page-5
As you suggested, collimation seems to be pretty critical with these beasts.
Interesting that the secondary position can also affect it (but logical I suppose). 

Lots of luck
Noel
Synta mount, a bunch of telescopes and a shed (on wheels).

Mac

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Re: Sharpstar 15028 reducer - tool
« Reply #4 on: Nov 09, 2020, 14:20:10 »
Quote
difficulty getting all the bits to be concentric on the forums as well as the correct spacing

Aluminium foil is your friend.
Standard household foil is typically 0.016 mm
Very very adjustable, especially for shims.

Mac.
Never, ever, argue with an idiot. They'll drag you down to their level and beat you with experience.
If you argue with an idiot, there are two idiots.

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Re: Sharpstar 15028 reducer - tool
« Reply #5 on: Nov 10, 2020, 08:30:58 »
Also you can take leaves off a feeler gauge and have known thickness shims which are much more solid - they are dirt cheap on ebay.
We're all guinea pigs in the laboratory of life. Better a fluffy guinea pig than a lab rat!
¯\_(ツ)_/¯ (Gallic shrug :))