Telescope Finders

Why is finding what you want to see so bloody hard?

In my equipment list you’ll see that I have a number of different finders for use with my telescopes. The biggest problem when you get under a dark sky (and it’s not cloudy) is finding out what on earth you’re looking at. There are a few things I use to help me out.

The item that’s used the most is an app called SkySafari Pro which runs on my iOS devices. I usually use it outside on my phone as it’s small and compact to grab when I need it. The app itself is fantastic and amazing to use. There are loads of features, and I admit that I only scratch the surface with what this app can do. I’ll write another post about it soon.

I’ve learned some of the main constellations, but if like me you struggle to balance work (I work shifts), other family demands and the weather to do some of your astronomy-related hobby, it’s VERY difficult to learn all of the constellations and to remember which star is part of which constellation – particularly as they have the cheek to move around throughout the year!

It amuses me when I read on the myriad of forums out there on the internet that in order to enjoy astronomy you must “only get binoculars and learn the night sky first” – yep – I’d love to do that, and maybe when I retire I’ll find the time – but I want to get out and see what I can now, not in x months time when I’ve done my homework first!

Another item I use is a great book called “Turn left at Orion” – I think it’s available electronically now, but I would recommend getting a paper version. It has easy to understand maps of the night sky for different times of the year and shows you what you should expect to see based on the type and size of telescope you have. When I started I didn’t know if I was going to see just pinpricks of light or Hubble-like images, so this was an excellent resource to set my level of expectation.

I’m a lover of go-to or push-to systems as they give me the ability to see and do so much more on the limited nights of viewing that I have. Yes they take some setting up, but I have found the set-up time on my new Celestron AVX mount far less than on a previous mount I owned.

So if I have go-to and push-to, why do I need a finder? Well you need to set these bloody things up, don’t you! Celestron has got a device called StarSense which is a camera which supposedly does all of the goto alignment for you. I’ve heard mixed results on its performance, but new software is coming out all of the time for it.

Considering telescopes have been around since Hans Lipperhey invented them in 1608 you might have thought that setting them up was a bit more slick than it actually is. In fact being “into” astronomy feels in the main like you’re a constant beta tester testing out, tweaking, adjusting and finding work arounds for things that one might reasonably expect to work off the shelf.

Anyway, I digress. Finders.

There are two main types of finders. Ones that act as a small telescope and magnify what you see, and ones that don’t.

Both types have their uses and it seems to me that someone could design and invent a magnifying finder that has some sort of pop-up reticle, or non-magnifying element to serve both tasks.

Magnifying finders. Like telescopes and binoculars these come in different sizes. They have numbers which don’t seem to mean much to the uninitiated, but these numbers are important. A popular collection of numbers against a finderscope is 9×50. The ’9′ bit refers to the magnification (9 times magnification) and the ’50′ refers to the size of the lens at the front, known as the aperture. The aperture is important as it determines how much light gets in and governs what you’ll be able to see. Why you’d want anything more than 9x magnification in a finder I don’t know – and why 9 seems to have become the standard I’ve no idea either. Why not 6x, 7x, or a nice round 10x?

You see, the problem with a magnifying finder is that when you look through it all you can see is a field of stars, and it’s very difficult to try and look along the telescope with your eyes and work out what you think the thing is pointing at, then look through the finder to see this detailed field of stars, then relate that to what you thought you were looking at in the first place. Yes, some things are a bit easier than this (bright planets, bright stars, etc.), but generally I find it very difficult.

This is where the non magnifying ones come in… There are various different types of these, a Rigel quick finder, Telrad or a multi-reticule finder. They’re slightly different in their construction, size and marketing hyperbole but they do a great job in being able to help you aim your telescope and magnifying finder at the correct part of the sky. For me it’s kind of a four step process:

1. Find where what you want to look at it using a smartphone app or chart

2. Use the non-magnifying finder to point your telescope and other finder at your target

3. Use the magnifying finder to accurately point your telescope at your target

4. Look through the telescope and hopefully see what you wanted to see!

Of course, if you want to set up your go-to system, you’ve got the whole alignment process and the mystically entitle “polar alignment” to do first. That’s the subject of another post….

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