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Red dot or 9x50


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Hi all

Now I am thinking about buying a red dot finder for my scope but having no experince with them I was hopeing you guys coud help me.

Whitch is better red dot or the 9x50 I got with the scope thankyou all

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The 9 x 50 is more accurate and increases the limiting magnitude of the objects you can see but a RDF is very intuitive to use but yields a limiting magnitude of slightly less than the unaided eye. The significance of this is that with the 9 x 50 you can locate dimmer objects.

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I found that it depends on how much light pollution you have.

My Mak came with a RDF but my skies were too bright for me to see many of the guide stars (in Turn Left at Orion for example) without magnification. Also my RDF was a cheapo supplied-with one which was more of a red splodge finder. I'm sure a quality RDF would perform better.

I upgraded to a combination of a 9x50 finderscope and a Rigel Quikfinder. I find that the Quikfinder can get me in the general area (it uses concentric red rings which are easily adjustable for brightness) and then I use the finderscope to locate my target. I also use the same combination on my Dob.

HTH

Andrew

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Thank's alot guys LP hear is not that great so the 9x50 is probably the safer bet.

Hi Paul I've just started in astronomy so I don't no anybody in the hobby around the flintshire area only one guy and he's at the same stage as me.

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RDF's really work for me but some people hate them

I'm firmly in the "hate" camp ... the point here is that a decent magnifying finder allows you to "star hop" using stars much fainter than those you can see with the naked eye (or through a RDF) but with a much bigger field of view than you can possibly get with the main scope. 9x50 is a useful size for most amateur scopes though a bit small for the larger ones, where you may need a combination of large & small finders.

A magnifying finder (when accurately aligned) also hits the field of a high magnification eyepiece, something which is very hard with a finder that doesn't magnify - so you have to swap between low & high power EPs and may lose the target whilst doing so - especially with lightweight "beginners scopes" which are more likely to be hudged off target than heavyweight solidly mounted scopes.

Of the unity magnification finders, the Telrad type which project a grid rather than a dot are much to be preferred. The issue with the dot is that it obscures the object you're trying to point at!

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The trick with finders is being able to make the transition between finder and eyepiece views, and still know which direction is which so you can identify the correct field.

There are 3 issues in this- orientation of the image in the finder compared with the scope, field of view of finder compared to scope and finally how good your brain is at mangling all the factors.

Your brain will get better with practice, but I think you could help yourself by getting an low power eyepiece with a wider field of view. your current 25mm will show you around 1 degree of sky compared with about 5 degrees for your finder. I had a similar set up to you at one time (10 inch flex tube) and found things a lot better with a cheap 30mm ultra wide eyepiece. Stars weren't great at the edge of the field of view, but for me it made it so much easier reconciling the finder and eyepiece views.

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Hi Andy

I use a Telrad and a 9x50 on my dob and find both work well.

I would agree with Catburglar that a wide field eyepiece works really well.

I wouldn't buy a really cheap one though as i think you will find it ideal for big faint fuzzies.;)

good hunting

Steve

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I use a Rigel and the 6x30 that came with the scope. I use the combination just like AWR says. The Rigel is a lot smaller than a Telrad, which is why I chose it for my 150mm and it comes with a spare base that is now on my Skymax. The Telrad has three rings instead of two though and should fit fine on your 250px.

Rik

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I prefer a simple RDF instead of the 9x50 that came with my telescope.

It has variable brightness so I can dim it right down so I can still 'see' through the dot to my target, and it is so intuitive to use (in keeping with my dob) ;)

The 9x50 shows more than the RDF but I often found that difficult to get to grips with. A bit like on a poor night only the brighter stars show, so I can easily pick our Cassiopia etc..., whilst on darker nights more stars are visibile, sometimes 'masking' the constellations I'm looking for - if that makes sense?

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It does twotter - I found at really dark sky sites the optical finder was so full of starts I coukldnt work out which one I was supposed to be navigating by.

I have both...I use the red dot to get me in the general area and the optical 9x50 to zero me in and also for very wide angle views.

My 9x50 is a telescope in its own right and can generate some good wide field views without using the main scope.

Mostly I dont have to bother navigating using finders as I use the GoTo BUT the finders can be very useful for GoTo alignment. I set my optical fincer up accurately to the main scope optics and use the finders cross hairs to centre the alignment stars on. It gives excellent GoTo alignment results.

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.... and finally how good your brain is at mangling all the factors.

.

Catburglar gets my vote for SGL quote of the month.

At first i thought it was a typo, but no mangled is quite an apt description.:p

My brain certainly gets mangled sometimes. when up is down, left is right...Can't find the coffee flask sometimes! ;)

Still prefer a finder to rdf, unless at a dark site.

Shame they don't make all finders correct ,erect image though- would make life a lot simpler.

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