Last updated: 7 December 2003
Sent: Sunday, December 7, 2003 05:01:25 From: firstname.lastname@example.org (Michael Morris) Thanks for the indispensible web site. Please could you post the attached bit of info about how to make a simple, cheap sun finder for an ETX wherever you think most appropriate on you web site. Thanks Michael Morris
Home made Sun Finder.
For a long while I have been trying to find a small sun finder to fit onto my ETX 90EC. The ideal one appeared to be the Televue Sol-Searcher (www.televue.com), but at around £25 + mount + p&p this seemed a bit expensive for something that would only be used occasionally. Also it would require fitting a mount to my already crowded ETX tube assembly. Then along came the excellent BC&F Engineering producing a simple sundial-type finder that fits over the ETX finderscope for only £19.99 + p&p. Looking at pictures of the BC&F Engineering sun finder on their web site (www.astro-engineering.com) made me realise it would be quite easy to build my own. The key to this simple device is the Eyepiece Barrel Cap (Item# STCAP) from Scopetronix at $1.25 (www.scopetronix.com). I bought mine from Greenwich Observatory Limited in Cambridge, UK via mail order. They had to order it especially from the U.S. but they still only charged £1.25 + p&p. I carefully drilled a small hole through the centre of the cap. I then used a small threaded brass tube (from a kitchen cabinet joining fitting) and put 25mm washers on either side and secured the whole assembly with a small bolt. The Scopetronix cap is made of quite soft plastic and easily distorts so it is important to use the large washer on the back as well to stiffen the whole assembly.
Inside of Sun Finder – Note large washer inside to make cap rigid and gaffer (duct) tape to ensure a snug fit on the finder scope. Be careful that securing bolt does not protrude too far or it may damage objective lens of finder.
Obviously you can use any narrow bar or tube with either an external or internal thread on it instead of the kitchen cabinet joining bolt, but you must be very careful that the end protruding inwards is not so long as to risk damaging the objective lens of the finderscope.
The front washer was painted with a couple of coats of matt white enamel paint (Humbrol). Finally, I put a thin strip of gaffer tape (duct tape) around the inside of the cap to make sure it had a snug fit to hold it firm and prevent it falling off. As I already had the washers, kitchen cabinet joining bolt, paint and tape, so my only expense was the Scopetonix cap.
The sun finder simply slips over the front of the finderscope (before pointing the scope anywhere near the sun) and you are ready to go. One simply moves the scope until the shadow disappears. I tried it out earlier today (using a Scopetronix white light sun filter on the front of the ETX 90) and found that it was quite difficult to use it to get the sun in the field of view (FOV) of a 26mm eyepiece every time. However, the sun was never more than one FOV away so it was still much easier to acquire the sun than with out the sun finder and it never took me more than a few seconds to get the sun in the field of view. This compares with it sometimes taking me up to 5 minutes by my previously used method of using the shadow of the scope on the ground.
Front of Sun Finder – Left: Sun finder in place, note shadow of post on white disc of washer. Right: Telescope moved to align with the sun – no shadow.
Please note that this sun finder was fitted to an ETX 90EC with a retro-fitted Meade #825 8x25mm right-angle finderscope. However, Scopetronix advertise the STCAP eyepiece barrel cap as fitting the front end of the standard ETX 90EC straight through finder scope as well.
PS: I also bought the Scopetronix Eyeguard and Finder cap (Item# STLCAP- $1.25) which works very well as a cap for the eyepiece end of the Meade #825 8x25mm right-angle finder scope.
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