Sunday, August 2, 2009

Is There a Perfect Finder Scope???

(NOTE) This question is sort of like asking, "what is the best flavor of ice cream?". You will get many different answers. So to a beginner, this might lead to a confusing situation. Here is where I get a chance to straighten out the road a bit for you.

You have bought a nice scope and it came with this little teeny tiny telescope. What the heck is that for? That is the finder scope. It will assist you in getting your scope aligned with the night sky. Some folks use a finder all night long as they move there scope manually across the sky, star hopping to their next target. Some folks use it to setup their electronic motorized goto scope and never look through it for the rest of the night.There are those of us that have put our finder scope in the box and never get them out because we have other means of getting the scope aligned. This can be in the form of a red dot finder or even a Telrad finder that uses a recticle with a bull's eye pattern to get you aligned or star hopping. To get this thing straightened out we will look at the different finders and their application to each scope type.

This is your typical finder scope found on most telescopes it is a straight through design The image will be inverted upside down. It will take a little time to get comfortable using an inverted image finder when you are looking in the finder and every fiber of your being is telling you to move the scope right to center the object. You must go left. This can be mind bending when star hopping but you will get used to it. Probably... I have seen straight through finders on every scope practically made. As with all finders the bigger, the better the light gathering. Keep this in mind if you are getting another finder for your scope. Finders are wide angled so they see a bigger chunk of the sky than the main scope. That is why we use them to kind of whittle the sky down to where your target lies.What Telescope(s) would be best for this venerable design? Catadioptric ( SCT, Maksutov etc.) and refractors are best suited for the simple reason the eyepiece is in the same direction as the main scopes eyepiece no jumping around the scope to align it. There is a little twist to this finder scope. It can come with a illuminated recticle (Cross hair) which is a huge plus in the deep dark of night.

The right angled finder is a wonderful design if you are more worried about a stiff neck. When you are trying to find something high in the sky you will notice your straight through finder has become very difficult to use. You must get down on the ground and look up through the eyepiece. The older I get the more this rings true. The right angled finder has been the savior for many a neck and knee low these many years. There are two schools of thought on right angled design One is the corrected image camp. This system makes aiming your telescope easy by showing an upright, non-reversed image. This is pretty easy for the brain to digest. Right means right. right? So if confusion is the issue when aligning your scope then this is the one to get plus your neck will be happy.The other camp will tell you while the simplicity of moving the scope has been improved with the correct image it is not showing the same image as what is in the Catadioptric scope. The solution is the right-angle first-surface mirror diagonal. It gives images that are upright, but mirror-image reversed, just as they are in the eyepiece of a catadioptric telescope. This makes the finder very useful with Schmidt-Cassegrain scopes, as the image orientation of the finder matches the upright mirror-image orientation you see in the main scope’s eyepiece. This is just something you as Joe/Josephine Consumer will have to figure out which one is best for you. If you use your scope for birding etc get the correct image right angled finder. You will find Right angled finder scopes on all scope but I highly recommend them for Newtonians

Red dot finders do not magnify. For anything that you can see at night they rock. when aligned with the scope it is a simple thing to align the scope especially with goto scopes center the dot on what ever star and go to the next one very quick no out thinking your brain when it comes to moving the scope right is right up is up. they are usually in line with the direction of the scope. Objects high in the sky can be a pain to align with.There are some red dot finders designed with a mirror so they can be used as a right angled unit that's a nice feature Some red dot finders have circle recticles for star hopping these do very well. One draw back is they take batteries. They almost always use the disk type. Running over to the handymart to get a battery might be a problem. You will find these very handy for any scope out there. I also see them sitting right beside their magnified finder scope cousin right on the same scope. They will be a great addition to your scope stuff.

Last and far far from least is the reflex site. A Telrad ( the brand name) for many many astronomers was and is the answer to many a prayer. It is a simple yet very effective siting mechanism for aligning your scope. Like the red dot finder, they employ a red led. I use a Telrad and only a Telrad on my Celestron CPC scope. The mounting mechanism is so that you unscrew the keepers and the Telrad comes right off the base. You may put it right back on the base and not have to align it with the main scope again.It will be very close to right on. It takes more time to put my finder scope on and get it aligned to the main scope than to just throw the Telrad on and align the main scope period. Using the Telrad, I can have my scope very accurately aligned using three star alignment in under 5 minutes with usually 3 minutes being the average. Now when it comes to star hopping with a Dobsonian mounted Newtonian telescope you can not beat the Telrad. The Telrad projects a series of concentric red rings (4 degrees, 2 degrees, and one-half degree in diameter) on a tilted clear viewing plate at the top of the finder. These circles make it easy to starhop from object to object. If a galaxy is 10 degrees north of a known star, for example, two 4 degree Telrad jumps and one 2 degree jump from the known star will take you to that galaxy in seconds. The red circles can be seen from almost any distance behind the Telrad, 2"" to about 2 feet so eyeglass-wearers can use the finder. Rigel also makes a reflex site also but for almost everyone the Telrad is the one. You can find this jewel on the scope of most seasoned telescope owners. Draw backs are some people can not seem to get lined up with the image and keep losing it I have not ever had that problem it is just a matter or moving your head slightly till you find it. they also make a right angle attachment for them to help on neck breakage. This puppy takes a 9Volt transistor battery The battery lasts forever it seems unless you forget to turn it off. Telrads will be found on all scopes but mostly on Newts and Cats. They are kind of big so they look a little odd setting on a small refractor.

So the choice is yours. There is no perfect finder out there but the Telrad come close in my book. Unless you are made out of money and just buy them all and decide ( Wife would not go for that idea) Do the research ask your fellow stargazers what works for them and why. Does that fit your needs. I am in love with my Telrad and always will be but I will never tell you that is what you need to get unless you look through one and say this is so cool!Then I might. You need to fit to the finder. Make a good decision and go have some fun . and if you are not happy with that finder scope send it back and get something else like say a ........ Telrad.

Clear skies and great seeing too,

Steve T


  1. Steve:

    MiniBorg 60ED. :-)

  2. Awesome post.

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