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16 Years old and still going strong




I like a bit of recycling and so, after I realised that I had not used my old ETX90 RA for at least two years, I decided to get it out of its fabric carry-case and give it 'the once over'. I have to say that little scope is a robust little beggar and optically as sound as the day my partner Toot purchased it for my fiftieth birthday. The fork mount is definitely passed its sell by date but the OTA is definitely too good to waste sitting on a shelf in a bedroom.

So today I decided to remove the OTA from the forks so that I could use the ETX on my recently acquired Star Adventurer equatorial mount or otherwise piggy-back on my 127mm.refractor. Being a bit cautious, I consulted the relevant pages of Mike Weasner's site and after a bit of a rumage around to find the right sized imperial allen key, I threw caution to the wind and set about separating the scope from the forks.  Once the four hex screws were removed it only required a bit of brute force to slide the two bits apart. 'Houston we have separation' and the jobs a good un!

The next part I really enjoyed, a quick trip to Maplins to buy a flight case to house said OTA. I really like pulling out the precut sections of foam etc. However, I have relunctantly come to the conclusion that I have run out of items of furniture in our sitting room behind which I can  hide the now seven flight cases from Toot. I have also covered most of my backyard with sheds and if I put anymore stuff in the loft, I will inadvertently convert my house into a bungalow.

I'm really pleased that I shall be using the ETX again. It will be good for imaging brighter comets and white light solar work.  Hopefully, I will be able to use it to watch the transit of Mercury.

On a more positive note, less cash or space intensive, a piece of transmission diffraction grating film arrived mail order from Israel this morning. So next week on rainy days I will be working on my Mark2 DIY filter or the 'VCS'  (aka a very cheap spectrometer).  I made the COAA version using an Epson printer to print lines on acetate sheet and this works quite well  (image in one of my albums) but number of lines per millimetre limited by the printers operating parameters.  I have been reading Jeffrey L Hopkins 'Using Commercial Amateur Astronomical Spectrographs' published by Springer.  It is an excellent practical read on spectroscopy particularly suitable for someone like me.  I sit firmly on a spectral line somewhere between 'reasonably untechnical' and 'complete numpty'.

mak 006.JPG

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Just in case it is relevant to/for you but these people do a cheap diffraction grating:


About 4/5 way down the Optical Components, comes in 6"x1.5" offerings it seems. They say they do larger pieces and it was actually those that I saw about 2 years back. Think they were talking of A4 size then. Thought is that I suspect the item from Isreal is better but for building up a prototype where it is easy to get fingers and marks on items maybe some of this and a pair of scissors would reduce the blood pressure .

Also, and my curiosity, what is the handset that is in the OTA image? I thought that the 90 RA did not have a handset, just taking 3 AA and the motor in it drove only in RA.

Just realised where they are located, I am at Hoddesdon once a week, may have a look for them next time.

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