Introduction: Smartphone Finderscope

About: I had been interested in DIY activities since my childhood. One of my DIY activity - astronomy and telescope making took me on a path to join professional body of astronomers.

This one is a simple smartphone hack that can be used as a finder scope. We made this way back in 2013 and we used it to locate Venus in broad daylight. It was Friday, 6th of Sept 2013.

The telescope is 100 mm Newtonian, home-brewed by Pooja Tolia (who is looking at Venus, in this photograph). In the background are (from L to R) Smruti, Mayank, Hrishikesh, Jayshree and Arunima.

All that is needed is

1. Smartphone (of course) with sky map installed.

   I am using Samsung Galaxy with Google Sky Map app.

2. A cassette cover

3. A piece of wood - about the length and width of the cassette cover

4. I am using - a ball and socket attachment with 20 TPI 1/4 inch bolts for the camera.

5. 20 TPI 1/4 inch nut

Step 1: Nut to the Wooden Strip

A hole was drilled in the centre of the wooden strip and the 20 TPI 1/4 inch bolt was fixed to it.

Step 2: Wooden Strip to the Cassette Cover

The wooden strip was now fixed to the cassette cover. 

Note: You have to file away the cassette holding tabs on the cover. 

Step 3: Attachment Goes to the Telescope

Now the phone is inserted into the cassette cover - fixed to it by rubber bands and the attachment goes to the telescope

I had a ball and socket attachment that I could fix to the telescope tube but one should be able to work out an appropriate arrangement.

One possibility, that I had used in past is to use the ball and socket part of the rear-view mirror used in automobiles or use the camera holding part of the camera tripod.

Step 4: Aligning

For the first time, when you are using this setup try when the Moon is up there in the sky.

Begin with aligning the optical finderscope and the main telescope. Look at a distant object through the telescope and then aligned the finder scope (you know what to do).

Next, put the phone on camera mode and centred the same object in the square of the screen.

Open SkyMap app. Then point the telescope to the Moon. Check the postion of the Moon shown on the screen of the smartphone. Using a sketch pen mark the position of the Moon on the smart phone.

Now say you want to search Jupiter. SkyMap search mode to find Jupiter. A direction arrow will appear on the screen. follow that arrow using slew motion. Once Jupiter appears on the screen of the smartphone get in the centre of mark that you made earlier. Jupiter will be there in the optical finderscope but might not be exactly in the centre of the crosswires. Get it in the centre and there it will be in the eyepiece of the main scope.

We used this to find Venus in broad daylight.

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