How to Look at the Sun With a Tellescope Without a Solar Filter

Introduction: How to Look at the Sun With a Tellescope Without a Solar Filter

before we start i would like to say, never, ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever look directly at the sun without proper equipment! and seeing  as were not making the proper equipment lets keep to this saying.  with this method you will be able to see sunspots although i have never seen a CME (Coronal Mass Ejections for those that are not astronomically minded)
so without further ado


1. telescope
2. telescope lens
3. poster board
4. sunglases

Step 1: Aim for the Sun

to aim for the sun, get the scope pointed in the general direction. then, put your finger close to the lens, (but not touching!) and make the light on your finger the brightest it can be , there should be a little light dot that you can see on the lens and won't blind you. also this wont burn your finger as long as your using a reasonable lens, your 6mm, will burn your finger. 25mm not so much, 40mm even less. it really dosn't matter what size lens you use. sorry for the sudden tangent.

Step 2: Add an Aperture Cover.

Step 3: Veiw

hold the poster board up to the telescope with the projection of the sun shining on it. move the poster board farther away and closer to the telescope to make the image bigger and smaller. note: the bigger the projection the dimmer the picture. adjust the focus and there you have it! this is also where the sunglasses come in.

thanks for building!

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    4 Discussions


    8 years ago on Introduction

    As an amateur astronomer for nearly 50 years, I would advise against this technique because of the amount of heat going through the eyepiece lenses. Given that the sun is so bright, a much safer method is to at least place a mask over the tube. In this mask are two small holes placed at opposite sides of the inner diameter of the tube. This will greatly cut down on the amount of light passing through the scope, from the mirror to the eyepiece. I have known of some people to use the full aperture method as you show here to actually have so much infrared passing through the eyepiece that some of the lenses cracked or the cement (in cemented lens sets) to vaporize explosively resulting in small glass fragments. While I'm told this is rare, it does happen and it sure kills your investment in eyepieces.

    A safer bet: Splurge on mylar filters for a reduced aperture mask. It will make both you and your telescope much happier!


    Reply 8 years ago on Introduction

    Thanks for the advise, could I cover the aperture in black construction paper and then put the two holes in it?


    Reply 8 years ago on Introduction

    Yes, that would work so long as you have some way to make sure it doesn't slide around. You also want to make sure no stray light leaks in between the mask and the edge of the telescope tube because that will degrade your viewing. Your scope looks to be about a 4-6 in diameter mirror, so I would suggest making the two holes each about 1/2 in to 1 in in diameter. Make sure you arrange them so they don't intersect any of the support members for the diagonal in order to minimize unwanted diffraction effects. For example, if you have the diagonal on a single arm (as in many smaller scopes), simply place the holes at the 3 and 9 o'clock positions assuming the support arm is at 12 o'clock.

    One often sees scopes with a mask using a single hole that is 20-30% of the aperture diameter of the mirror. This is satisfactory but slightly degrades the resolution that can be had by using the full diameter of the mirror. Hence, two small holes on opposite ends of a diameter.

    Seriously, you should splurge for the aluminized (or other coated) mylar filter. You can still do projection but you will have a much cooler, safer scope and view! You can find plenty of ideas on the telescope makers web sites all across the internet.

    All the best! Keep looking up!