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Finder scope vs red dot?

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#1 PJ007

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Posted 28 October 2020 - 03:25 PM

Newbie question. About to purchase a small refractor in the 70-100mm aperture range, mostly for lunar/planetary viewing and some terrestrial viewing. I have noticed that some people have finder scopes (20-40mm aperture) attached to their scopes, while others use red dot finders. What are the advantages of each?  Thx.



#2 Mike G.

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Posted 28 October 2020 - 03:37 PM

personal preference mostly.  I swapped out all my powered finders some time ago and converted everything over to 0 mag finders (red dots/MRFs).  they work well for me as in most cases, my skies limit my useful magnification in scopes to under 150x.  so I don't need a 8x, 9x finder to find some very dim object next to something I can't see at all.  a big ol' red dot and a 35mm Panoptic and I can find everything I want.  but if I had pristine skies and operated at mags over 200x, then I would likely need something with some magnification to find those really small, dim objects.


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#3 havasman

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Posted 28 October 2020 - 03:52 PM

I don't care for a finder scope with my refractors and prefer an RDF. 4" f5.4 and 4.5" f7 scopes both show wide enough fields for me to use finding and hopping around. I use an Astro-Tech multi reticle RDF and a Baader Skysurfer V on the different scopes and they both work well for me.


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#4 cst4

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Posted 28 October 2020 - 03:53 PM

I'm definitely a red dot guy.  Much easier to quickly point and shoot at anything that you can see with the naked eye or know about where it is.  Even at 250x I usually have no problem aiming and getting the object in my field of view.  Larger magnified finders are good for finding DSO's that you can't really see or don't know exactly where they are at.  In those cases an 8x50 right angle correct image finder can get the job done.  Correct image is nice so it is close to what you see in the sky when you look up, which makes it easier.  But 95% of the time a red dot is just easier and quicker... and the other 5% of the time I put in a low power eyepiece and search for the object that way instead of using a magnified finder.


Edited by cst4, 28 October 2020 - 03:54 PM.

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#5 Redbetter

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Posted 28 October 2020 - 03:57 PM

For small refractors I don't see any need for a traditional or RA/RACI finder.  A simple RDF is all that is needed.  The possible exception is some long focal length small refractors, because their true field of view with 1.25" format eyepieces can be rather narrow; but even with 900mm focal length in 1.25", a 1.7 deg true field of view is possible.  

 

For refractors with short focal lengths and 2" focusers/diagonals/and 2" eyepiece capability, traditional finders really don't make much sense.  


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#6 Dave Mitsky

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Posted 28 October 2020 - 04:01 PM

I agree with Redbetter.  If the refractor has a short focal length, a red dot finder is all that's really necessary.  RDFs are useful on mounted giant binoculars too.


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#7 Ihtegla Sar

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Posted 28 October 2020 - 04:20 PM

Newbie question. About to purchase a small refractor in the 70-100mm aperture range, mostly for lunar/planetary viewing and some terrestrial viewing. I have noticed that some people have finder scopes (20-40mm aperture) attached to their scopes, while others use red dot finders. What are the advantages of each?  Thx.

For lunar, planetary and terrestrial, a red dot finder will be a lot more convenient.  If you start tracking down fainter objects, like DSOs, double stars, carbon stars or anything that is too faint to be seen be seen in a red dot, then I find an 8 by 50 RACI to be very useful since you can star hop in the finder using a star chart to get where you need to go.

 

Although Redbetter is correct that smaller refractors have relatively wide fields, depending on the focal length, I find an 8 by 50 RACI to be very useful for star hopping.  I find 1.7 degrees to 3.7 degrees to be rather narrow for star hopping and personally, I cannot star hop in a mirror image because its just too confusing for me. I don't have a good sense of left vs right in general and the only way I can star hop through an eyepiece is by holding a mirror up to my star chart, so for me a RACI is mandatory for star hopping and a five degree field of view makes it a lot easier than a 1.7 degree field.  An 8 by 50 RACI is just right for star hopping with the Sky and Telescope Pocket Atlas since it will show all stars in the chart without showing any background stars that aren't on the chart.  So, I have an 8 by 50 RACI on my 100 mm f7.4 and f/9 apo refractors but not on my 80mm f/4 achro.  

 

But just for planets, lunar and terrestrial, a red dot is the way to go regardless of the focal length/field of view.


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#8 bobzeq25

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Posted 28 October 2020 - 04:35 PM

Red dot plus a star map.


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#9 Arthur NY

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Posted 28 October 2020 - 05:43 PM

Red dot.

 

I use a widefield 90mm refractor as a finder scope on my rig!



#10 vtornado

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Posted 28 October 2020 - 06:12 PM

For planets and lunar there is no need for a magnified finder.  They are so bright they can be seen in the reflex finder and quickly centered.

In my bortle 7 skies, I have so few guide stars that a magnified finder is necessary for finding most objects.  The distance between

guide stars can be greater than 20 degrees. 



#11 Jethro7

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Posted 28 October 2020 - 06:48 PM

Newbie question. About to purchase a small refractor in the 70-100mm aperture range, mostly for lunar/planetary viewing and some terrestrial viewing. I have noticed that some people have finder scopes (20-40mm aperture) attached to their scopes, while others use red dot finders. What are the advantages of each?  Thx.

Hello PJ007,

It is a mater of preference. I use a Televue Starbeams and prefer them over a small refractor finder scope. I find the intermittent red dot of the Starbeam is faster and easier for me. But I also use my AT102ED as a Super finder scope when I am looking for DSO's  for my C8 scope. I guess you need to try both and see what platform works best for you. Many people have both types mounted on their telescopes. The red dot for a quick rough alignment and the refractor starfinder scope for fine alignment. Just like my use of the AT102ED.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro

 

20201019 092633
20201019 092727

 

 


Edited by Jethro7, 28 October 2020 - 07:11 PM.


#12 PJ007

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Posted 28 October 2020 - 07:02 PM

Thanks all. Very helpful.



#13 Dennis Tap

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Posted 28 October 2020 - 07:07 PM

blabla, mostly for lunar/planetary viewing and some terrestrial viewing. ..blabla

For this a red dot finder is sufficient.
 



#14 brentknight

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Posted 28 October 2020 - 08:41 PM

I like my GLP...

 

Orion and Sirius - Small Mint.jpg



#15 makeitso

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Posted 29 October 2020 - 07:57 AM

For me, when I’m using either my Meade LX70 R5 (120/f8.3) of my AT102ED f/7 refractors, I use an RDF. If I’m using my 12” dob, I have a telrad and an 9x50 RACI.

 

I’m looking for different objects with the dob than I am with the refractors. For planets and brighter objects I don’t need the RACI in either case. For dimmer stuff, the RACI helps me star hop. Lots of times, I’ll search around with the AT102ED, when I find something of interest, I point the dob at that spot for a closer look.

 

Jack


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#16 rhetfield

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Posted 30 October 2020 - 08:14 AM

For me it is a red dot to find the visible stuff and degree circles for the dim fuzzies.  My mini dob is well suited to having big high res degree circles and has up to a 2 degree FOV with the stock EP's.



#17 therealdmt

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Posted 31 October 2020 - 10:01 AM

For my F9 refractor on an alt-az mount, I have a 8x50 right angle, correct image (RACI) finderscope plus i bought a red dot finder (RDF) — but I have just one mounting bracket, and it’s holding the RACI. I might get a double bracket adapter later so as to include a second finder of some sort, but for now it just has the one. I did buy a second mounting bracket to stick on with 3M tape (intended for the RDF or a laser, etc.), but after that bracket came unstuck I haven’t re-mounted it so far because...I’m finding I don’t really need the RDF (or a laser, etc.).

 

Basically, by judging the azimuth by looking along the top of the scope and aligning it with my target, and then bending or kneeling down and sighting along the side of the scope to match the elevation of the target above the horizon, I’m finding that I can almost always get the scope pointed at the intended target close enough so that it’ll show up in my finderscope. From there, I can position it in the finderscope so that it’ll appear in my telescope’s eyepiece at just the right position and angle for a long transit of my field of view - even when directly starting out with high eyepiece magnification.

 

Anyway, I’m a noob so take that for what it’s worth, but I’m finding there’s no point where I’m wishing the RDF were back on. One aspect is, as it’s a longish refractor and an RDF is a straight through instrument, for any target that’s not pretty close to the horizon, you really have to crane your neck back for straight through viewing from the rear of the scope. Accordingly, I mounted my RDF up the tube and to the side a bit so it was out of the way of my finderscope and where my main eyepiece didn’t block the view, but then I had to turn my head kinda sideways to get in position to use the RDF and that was bothering my neck a bit, too. In contrast, just eyeballing it top ‘n side to get the scope pointed close enough to transition to the RACI means I don’t have to spend time with my neck bent way back or over.

 

ymmv (as may mine - I absolutely still might experiment more, but the desire is decreasing as I get better at just sighting along the scope itself)


Edited by therealdmt, 31 October 2020 - 12:22 PM.

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#18 brentknight

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Posted 31 October 2020 - 10:33 AM

I know of a couple people who don't use any finder and just sight down the tube.  I've done it occasionally with my F7 refractor.  Whatever works for you is just fine.

 

I think Dobs are a little harder to use without some type of pre-finder like a Telrad, dot or laser.


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#19 John Carlini

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Posted 31 October 2020 - 12:09 PM

I use both red dot and different types of magnified finders depending on what I'm doing that evening. I like red dots and straight correct-image finders when I'm taking images with the DSLR (minimal head movement) and use RACI finders when doing visual observations on DSOs (more light). I also have a solar finder and laser pointer to complement the mix. So, I think "the more the merrier" when it comes to finderscopes...


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#20 river-z

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Posted 31 October 2020 - 03:29 PM

I use a RACI finderscope on my 12” Dob, but on my 80mm refractor I got a 40mm eyepiece that functions as a finderscope. It works good for me and I like it a lot since I can also see stuff like M31 and the Veil Nebula that require a wide FOV.

#21 Paul Sweeney

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Posted 31 October 2020 - 04:23 PM

Any straight through finder, red dot or finder scope, is a pain to use near the zenith. Currently, the planets are all low or at medium height in the sky, so it doesn't matter which you use. I use both, and swap the out depending on what I am planning to observe.
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#22 JohnnyBGood

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Posted 02 November 2020 - 09:34 AM

It's a matter of personal preference and what strategy people like to use to find things to see. I like to star hop using modest, paper charts and/or my copy of Turn Left At Orion, which I find easier to do using a traditional finder scope. A finderscope helps me see stars that are otherwise too faint to see on my own, so it's easier to follow along with the chart. So the process is like this: find a bright, easy to locate star near what I want to see. Move from it to another star closer to goal, then another, then another. "Okay, I start from this bright star, then I look for a little flat triangle to the east, then I follow the short leg of the triangle about twice the length of the triangle and I should be right on target." More often than not, the target is right there in the eyepiece. I find this useful for looking for really hard to see things because I'm pretty confident I'm in the right neighborhood so I look harder and don't have to pan around much.

 

A red dot, on the other hand, doesn't help me see things I can't see with my eyes. In fact, I can see *fewer* things through the little screen. So the strategy there is different. "Okay, let me put the red dot in about the same spot between these other stars as it is on the chart and hope it's close". It's certainly quicker, but I usually have to pan around for a while in little circles to spot the target. If it's something dim I often go right past it. Green laser pointer is the same strategy. Some people combine strategies and use a much more detailed star atlas on an electronic device to star hop using their main eyepiece. Some people use both and have a red dot or GLP to line up on their first star hop target for their optical finder.

 

Some people love red dots, but the first thing I do with a new scope is remove the red dot and put on a 6x30 finder. Neither one is right or wrong or better than the other, which is why they sell both.


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#23 Bowlerhat

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Posted 02 November 2020 - 05:51 PM

Differs for each person, but RACI does the job for me. You can rotate it as well, which is a plus. It's easy to collimate, no need to bend your neck to look it straight through.

 

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#24 Arthur NY

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Posted 02 November 2020 - 06:25 PM

I like either a telrad or a superfinder. I'm not using a "conventional" finder on any of my setups.



#25 KBHornblower

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Posted 03 November 2020 - 11:45 AM

There is no vs in my case.  I use both as needed.  Actually I am using a Telrad, but the principle is the same, a non-magnifying reflex sight I can aim at a naked-eye object.  From there I can star hop with the 9x50 finder, which is much quicker than doing it with the main scope when the target is many degrees from the nearest visible star.




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