{"id":27756,"date":"2022-01-06T13:57:50","date_gmt":"2022-01-06T13:57:50","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=45858"},"modified":"2022-01-06T14:10:16","modified_gmt":"2022-01-06T14:10:16","slug":"a-guide-to-finderscopes","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/a-guide-to-finderscopes\/","title":{"rendered":"A guide to finderscopes"},"content":{"rendered":"

<\/p>

By Steve Richards\n \t\t<\/p>

Published: Thursday, 06 January 2022 at 12:00 am<\/p>

\n\n

A finderscope is a simple but invaluable accessory that attaches to your telescope.<\/p>\n

The smaller optical tube provides a wide field of view to help you locate celestial objects before observing them through your main telescope, but it must be aligned accurately to your telescope before use.<\/p>\n

There are two types, those with a right-angle finder and those with a straight-through view.<\/span><\/p>\n

A right-angle finder is more expensive but is more convenient to use.<\/span><\/p>\n

\""Finderscopes\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>\n

Remember that you will also need to buy and install a finderscope bracket for the optical tube.<\/span><\/p>\n

An accurately aligned finderscope makes locating objects much easier, but aligning it at night can be frustrating.<\/span><\/p>\n

To set up a finderscope, start aligning in the daytime by finding a very distant object using your telescope, centring that object in your telescope eyepiece<\/a> as accurately as you can.<\/p>\n

When doing any sort of observation during the day, make sure not to look directly at the Sun without specially-designed solar filters<\/a>, or this could seriously damage your eyesight.<\/p>\n

How to set up a finderscope<\/span><\/strong><\/h2>\n
  1. Locate a distant daytime object (not the Sun!) through your telescope and centre it in the eyepiece<\/li>\n
  2. Now turn to the finderscope and centre the same object on the crosshair<\/span><\/li>\n
  3. At night, locate a bright star in the centre of your finderscope<\/span><\/li>\n
  4. Look through the main telescope and centre the star in the eyepiece<\/span><\/li>\n
  5. Return to the finderscope and adjust until the star is centred on the crosshair<\/span><\/li>\n<\/ol>

    For help with this, read our guide on how to polar align using the Sun<\/a>.<\/strong><\/em><\/p>\n

    Follow our DIY Astronomy guides to make a smartphone finderscope<\/a> or a finderscope illuminator<\/a>.<\/strong><\/em><\/p>\n

    \""Sky-Watcher\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
    Sky-Watcher 9\u00d750 right-angle finderscope<\/span><\/figcaption><\/div>\n\n

    What finderscope is best for a Newtonian?<\/strong><\/h2>\n

    There are two main types of optical finder, those with a straight-through view and those with a right-angled view.<\/p>\n

    Since Newtonian reflectors have the observing eyepiece on the side of the optical tube close to the front of the telescope,<\/span> a right-angled finder is by far the most comfortable to use.<\/p>\n

    \""Right-angled\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
    Right-angled finders are better for Newtonian reflectors.<\/span><\/figcaption><\/div>\n

    If you were to use a straight-through finder, you would have to angle your face down the side of the telescope to see through it.<\/p>\n

    An illuminated crosshair makes it so much easier to centre objects.<\/p>\n

    Both the Celestron illuminated RACI 9x50mm finderscope or the Altair 10x60mm<\/span> right-angled illuminated finderscope should be on your shortlist.<\/p>\n

    Do you need a finderscope if you have GoTo mount?<\/strong><\/h2>\n

    \u00a0<\/p>\n

    \""William\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>\n

    Once upon a time we were lost without them. The trusty optical finderscope allowed us to get a wide field of view to visually home in on targets, or help us star hop<\/a> to the next one.<\/p>\n

    Now don\u2019t get me wrong, in terms of any basic or manual telescope, the finderscope still serves that purpose very well, and is a necessary piece of kit.<\/p>\n

    But when it comes to GoTo systems, it becomes a little less clear just how useful a finderscope can be.<\/p>\n

    \u201cWhat?\u201d I hear you cry, \u201cyou still need it for the initial alignment for the GoTo to work accurately don\u2019t you?\u201d\u00a0Well I think the answer is yes and<\/em> no to that.<\/p>\n

    If your initial polar alignment<\/a> is rough or you have a system that you need to move around a lot, perhaps for public outreach, then I agree that the finderscope remains useful, but only<\/em> for the alignment phase of setting up.<\/p>\n

    After that, if your polar alignment and star alignment is accurate then your target should always be in the view of a wide field eyepiece if not bang in the centre.<\/p>\n

    However, if you are able to conceive a permanent setup for your mount, you can get polar alignment very accurate indeed.<\/p>\n

    Once done, you will likely find you hardly ever use the finderscope, as the target should be in the centre of the view or imaging system you are using every time.<\/p>\n

    But today manufacturers have spotted an opportunity amongst all this, and we are now seeing finder\/guidescope combinations.<\/p>\n

    In other words, the fact that many astronomers are now using the finder as a guidescope for deep-sky astrophotography may well mean we haven\u2019t seen the last of the finderscope just yet!<\/p>\n

    Choosing a finderscope<\/strong><\/h2>\n
    \""Finderscope"\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>\n

    When choosing which finder is best for your telescope, there are a few things to take into consideration:<\/p>\n

    Overall construction<\/span><\/strong><\/h3>\n

    Is the finder solidly constructed? Are any parts loose and can the bracket be attached to it easily? <\/span><\/p>\n

    Optics<\/strong><\/h3>\n

    Is the front lens free from aberration and is it sharp across the field of view? Are any of the lenses multicoated and does the front lens have a hood that prevents it dewing up?<\/p>\n

    Focusing<\/span><\/strong><\/h3>\n

    Is the finder easy to focus and can it then be locked in position? Is the adjustment front or rear, and is there any play while focusing?<\/span><\/p>\n

    Holding bracket<\/span><\/strong><\/h3>\n

    Is the bracket well constructed and does it allow for easy alignment? Are the screws soft-capped to prevent them scratching the finderscope tube? <\/span><\/p>\n

    Crosshairs<\/span><\/strong><\/h3>\n

    Are the crosshairs in focus, sharp and centred in the field of view? If illuminated, are they too bright or dim?<\/span><\/p>\n

    8 of the best finderscopes<\/strong><\/h2>\n

    Right angled finderscopes<\/strong><\/h3>\n
    1<\/span>

    Celestron 9\u00d750 RACI<\/h3>\n<\/div>

    \u00a0<\/p>\n

    \""Celestron\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>\n

    The Celestron 9\u00d750 Right Angle Correct Image (RACI) Illuminated Finder offers 50mm, 9x magnification and a 5\u00b0field of view.<\/p>\n

    It displays celestial targets right-side up and left-to-right correct, which makes it easier to slew to objects and track them as they move across the sky.<\/p>\n

    It features a double-crosshair reticle etched into the eyepiece that can be focused separately from the finder.<\/p>\n

    A nice touch is the battery-powered illuminator that brightens the crosshair with a red glow to make it easier to see during dark, moonless nights. This is adjusted with an on\/off switch.<\/p>\n

    This finder also comes with a bracket comprising two rings and a dovetail. Align adjustment is carried out with thumbscrews.<\/p>\n

    • <\/li>\n<\/ul>