Posts Made By: Sean Clarke

Hello,

This is my first question to the mounts forum.

I have recently obtained an EQ 6 mount (not GOTO version) for my excellent 8.5 inch (F6)planetary reflector.

On the first night, observing Mars, I found that at higher powers (250X +) vibration from the drive was VERY obvious and was seriously derimental to the image (image was very sharp when drive switched off. I have no reason to believe that the drive is faulty.

The mount was set up on concrete with no vibration suppression units.

Has anyone else experienced this problem?

If so what was the remedy?

Many thanks Sean

Hello,

This is my first post to this group.

I have a rather worrying task ahead of me and would welcome any advice before I commnence.

I have obtained an 8 inch triplet lens, made by Cooke, Troughton & Simms. It has a nice cell, glass looks very good and has an F ratio of about 15.

The problem is that it has been cemented with Canada Balsam. I would like to separate the elements, and have it re-figured if necessary.

I know that in the past, elements have been separated by 'boiling' the lens in a pan hot water (slowing bringing up the temperature of the water to prevent any suddern shock to the lens).

Has anyone out there undertaken this proceedure? What is the ideal temperature that the basam will start to flow?

I hope someone can help.

Many thanks


Sean

Many of you reading this may recall a thread that I started earlier in 2006, with the above title - this title did make a few readers cringe, like chewing on silver paper!

Just to recap - I asked advice on how to separate the three elements for an old 8 inch Cooke,Troughton & Simms Photo-Visual triplet lens that had been cemented together with canada balsam (in the mists of time, by a previous owner).

The consensus of opinion was that the lens should be soaked in a tub of Xylene, to dissolve the cement.

Well, today (27th December 2006) I now have three (whole!) separated elements - taking around 5 months to separate.

In 2007 I'll begin work on building a 'folded' refractor to hold the F17.5 lens.

Thanks once again for everyone who 'steered' in the right direction on this.

Happy New Year to you All!

Sean

The old timers of this forum should remember my worrying title from a year or so ago when I had to separate the 3 elements of an old Cooke, Troughton & Simms 8 inch lens that had been balamed together. Well, after a very long xylene bath the elements were eventually separated and this old photo-visual triplet is nearing completion. Please see attached picture. The tube is from an old 12 inch revelation reflector. I will keep you all posted when first light occurs, sometime over Christmas.

Thanks Tom,

It is a Photo-Visual lens. On the cell is marked Number 81. I believe it was made around 1940. Lens technology is now vastly improved - this one has a few bubbles in the glass!

I don't know why it was cemented - it may have been for a non astronomical purpose - the elements are separated by foil spacers.

This was definitely not a periscope lens!

Hello Rex and list,

I own a 20 inch Newtonian with a slightly misplaced flat :S . The only way I can achieve perfect collimation is to slightly tilt the focuser to the tube. This means that the flat is reflecting light from the primary mirror by slightly more than 90 degrees into the focuser. The purists out there will say that the shallower an angle (albeit small) a light beam is reflected from secondary will be more destructive on the wavefront. I will eventually reset the secondary - another little job I have to do