RDF vs Finderscope

[Asur84]

I currently have an RDF on my scope but am wondering whether or not an actual finderscope would be better on my little Astromaster 76.

What, if any, are the differences between the two, and what are prefered by the masses on this great community?

Thanks in advance guys and girls.

[Mark at Beaufort]

If it helps I use both a RDF and a 9x50 on most of my scopes. I never use a goto and rely on star hopping. The RDF finds the best finder star and then I switch to the correct image right angle finder to access the correct star field.

Whether you need both might depend on the FOV you are using with your current scope. If it is a rich field frac you might get away with just the RDF.

Mark

[John]

Most of the time I use an RDF only but sometimes having an optical finder alongside it is helpful, as Mark says. So the ideal situation is to have both if possible.

[Alan_B]

I have both on my C8, but find I only need an RDF on my 80mm frac as it's used mainly for wide field or planetary

[Asur84]

In that case my question now turns to how and where would I then mount the finderscope as my RDF sits at the front end of my scope and does sit quite high also.

[michael.h.f.wilkinson]

You might wonder if a super-wide 24mm EP would not do almost as well as adding a finder scope. The RDF gets you in the right area, the 2.33 deg field of view may be enough to star hop. On my 80mm I really do not feel the need for a finder, although I might add an RDF.

[smudgeball]

Hi

I prefer the RDF.

I previously had a finderscope on my old newt.

It's really well aligned and works great......especially now that I changed the flat battery from a couple of weeks back

Neil

[MjrTom]

I only use RDF on my refractors and use a wide angle eyepiece in my telescope so in effect the scope becomes a big finder scope with far more. Light grasp than a 9x50 for instance.

Need to pick up a new RDF for my new to me 102mm refractor.

[sbooder]

I prefer a finder scope to the RDF, I have a little notebook and I use the finder scope to jot down the pattern of stars in the 9x50 so if I am looking for a faint without GOTO I pull out my little book and look up the object slew to the constellation and point the scope in the area I need and use the finder to get the pattern in the FOV.

It may sound complex but it works well for me. I got the idea from playing MYST.

[Damo636]

I have both but find i rarely use the 9X50 finder. As suggested above a nice wide angle low power ep will do the job once in the vicinity with the rdf.

[JamesM]

Red dot finders are fine assuming you can see enough stars to help point the scope which under light polluted conditions might prove difficult. That is why I would agree with the comments above recommending the additional use of an optical finder. I also agree that using a large eyepiece in a refractor can also replicate the benefits of a finder scope though if used in a newtonian, would replicate the view as seen in a straight though type of finder which provides an upside down AND back to front image making star hopping more difficult than it need be. The solution can be found in a right angled optical finder, which provides only provides a back to front image and is certainly more comfortable to use when compared to a straight through type that can give you neck ache after a while!

James

[michael.h.f.wilkinson]

Red dot finders are fine assuming you can see enough stars to help point the scope which under light polluted conditions might prove difficult. That is why I would agree with the comments above recommending the additional use of an optical finder. I also agree that using a large eyepiece in a refractor can also replicate the benefits of a finder scope though if used in a newtonian, would replicate the view as seen in a straight though type of finder which provides an upside down AND back to front image making star hopping more difficult than it need be. The solution can be found in a right angled optical finder, which provides only provides a back to front image and is certainly more comfortable to use when compared to a straight through type that can give you neck ache after a while!

James

Better still, get a right-angle correct image finder, or replace the regular diagonal of the finder with a 90 deg Amici-prism (cost 42 euro or so).

[Brinders]

I use both an RDF on my SCT and the finderscope, but an RDF only of my Megrez 72. I find the RDF more intuitive than the finderscope to get into the right area of the sky on the SCT, then home in onto the target with the finderscope.

With the little Megrez, the RDF alone is sufficient because of the scope's wide field of view.

Brinders

[Asur84]

Thanks all for the suggestions all, I'll be sure to have a look and try a few.

[LukeSkywatcher]

I dont use either. I have both but dont use them. I prefer to start out with a 30mm EP and get to the correct star field then i slowly increase the magnification until i am on target.

[MjrTom]

I dont use either. I have both but dont use them. I prefer to start out with a 30mm EP and get to the correct star field then i slowly increase the magnification until i am on target.

How do you know which star you have in your field of view?

[LukeSkywatcher]

I dont observe single stars per say (a 30mm EP doesnt allow you to observe a single star). I refer to the many star charts i have in books etc to get me in the general area of DSO's and then i narrow it down from there by increasing magnification.

Yes, in most cases one star looks the same as the next. I look for patterns of stars that appear in the charts i use and take it from there.

I really am a star hopper by nature.

[MjrTom]

Fair enough

I struggle to positively identify the star without the RDF showing the ball park area.

[Dave Dubya]

Depends on the telescope. With my dobbo I prefer using finderscope - just seems to work well for starhopping.

But with the refractor it's an RDF and with the SCT it's a little of both.