New Edition of Hints on Silver-Glass Reflecting Telescopes Manufactured by Mr. G. Calver, F.R.A.S. / with Directions for Silvering, Adjusting, &c.

Adjustments.

These instruments are always sent out in correct adjustment, and with moderate care during transit, and afterwards, will remain so, but as the performance of the instrument greatly depends on the accuracy of the adjustments the following instructions will enable the observer not only to ascertain whether they are perfect, but also to render them so if found defective. These adjustments are by no means difficult, and will be easily understood by attention to the following remarks:—

Into the draw tube screw the “adjusting piece,” which is a small brass circle with a hole in its centre about 1/20 of an inch in diameter. (The draw tube should be in about the same position as when at focus with an eyepiece.) Place the large mirror in its cell in the tube or body of the telescope, taking care that the three bayonet-joint pins are correctly placed, that is, with grooves pointing downward. They will be found to drop easily into their corresponding holes; care must however be taken that the grooves have gone well home. Both the speculum and small mirror, or “flat,” must be uncovered. On looking through the aperture of the adjusting piece, if the mirrors are in correct adjustment their reflections will be seen as follows:—the small oval mirror being placed at an angle of 45° will appear circular, and reflected exactly in the centre of this circle will be seen the bright image of the large mirror with a dark round spot in its centre, as shown by Fig. 1. This dark spot is the double reflection of the “flat,” and should be concentric with both the bright reflection of the large mirror and the circular outline of the “flat.” All these should also be perfectly concentric with the circle given by the stop in the draw tube. Should these circles not be all central the adjustments are not perfect and must be rectified as follows.

To adjust the “Flat” or small diagonal Mirror.

If the bright reflection of the large mirror is seen as a perfect circle, but not exactly in the centre of the “flat,” the latter requires adjustment; for this purpose loosen the milled head screw at the middle of the back of the “flat” which in large instruments is made sufficiently heavy to act as a counterpoise to prevent vibration. This will allow the “flat” to be rotated by the hand vertically with respect to the tube of the telescope. Bring the bright circular reflection of the mirror exactly central in this direction, and fasten in position by screwing up the milled head screw or counterpoise. If the circular reflection is quite central no further adjustment is required, but if not, then, after completing the vertical adjustment, as described, proceed to make the horizontal adjustment by turning in one or other direction the milled head of the horizontal adjustment screw, situated in front of the vertical adjustment screw; this will bring the circle of light exactly into its proper horizontal and central position, and the adjustments are then completed.

If the bright reflection of the large mirror is not seen as a perfect circle, and the small dark spot not in the centre, the speculum is out of adjustment, and consequently the adjustment of the “flat” is best performed by removing the large mirror or speculum with its cell and so arranging the body of the telescope that on looking through the “adjusting piece” a large sheet of white paper spread on the ground a short distance from the open end appears as a white circle of light reflected in the “flat.” Now bring this white circle exactly into the centre of the flat precisely in the way described above, and on this being accomplished replace the speculum uncovered with its cell, and proceed.

To adjust the large Mirror or Speculum.

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

When in perfect adjustment the large mirror viewed through the “adjusting piece” should appear as before stated, as a complete bright circle, with the image of the “flat” as a smaller dark circular spot exactly in the centre (Fig. 1). Should this not be the case it must be rectified by means of the three adjusting screws at the back of the cell. Proceed as follows:—First unloose (by a few turns) the small clamping screws which pass through the larger hollow adjusting ones; then, on looking through the adjusting piece the relative position of the image of the “flat” should be carefully noted. If the dark spot is nearer the bottom, and consequently more of the top part of the bright circle is seen (Fig. 2), the mirror reflects too much of the upper part of the tube, and therefore the top of the mirror leans too far back and must be pushed more forward by screwing in the top adjusting screw (a Fig. 1) a little at a time till the dark spot is central. Should the spot be towards the top (Fig. 2 inverted), the reverse holds good and the top adjusting screw (a) must be unscrewed or the two other adjusting screws turned in. Should the spot be towards the left (Fig. 3), screw up the right adjusting screw (c Fig. 1). If towards the right (Fig. 4), screw up the left adjusting screw (b Fig. 1). The dark spot is always furthest away from that part of the tube which is too much reflected, and from the adjusting screw that must be turned in to correct it.

When all the adjustments are considered perfect, as in Fig. 1, the small screws are to be clamped up to keep the adjusting screws in position. If, after the greatest care has been taken in adjustment, a flare should appear on looking at a star (say of the second magnitude) with an eye-piece of a high power, and the diffraction rings are not quite concentric, it can generally be rectified by turning the large screws of the mirror round in cell a little at a time. If this does not remove the flare the adjustment of the “flat”. is not sufficiently correct and must be altered by means of the screws at its back. If the flare is at the top or bottom of the star the “flat” must be very slightly revolved by the hand, after unloosing the middle screw, and when correct reclamping it. If at either side, namely, in the direction of the major axis of the “flat” and in a line with the tube, the “flat” must be altered by the long screw. It is always advisable to leave the telescope for a short time undisturbed, especially if, on first looking at a star, a flare should appear, as these appendages often vanish when the instrument has been for a short time in the air. These adjustments may at first appear somewhat difficult, but are rendered remarkably easy by observing how the different screw movements alter the positions of the reflections. A useful test as to the correctness of the adjustments may be obtained by viewing a star with a high power eye-piece out of focus. When in the centre of the field it should appear as a bright luminous circle with a circular dark spot in the centre, the size of the bright circle diminishing as the focus is approached and the dark spot remaining central.

The cell mount of the large mirror can be removed from the tube and replaced without disturbing its adjustments, but it is very advantageous if the entire instrument can always be left undisturbed when not in use in an observatory of light construction, having a skeleton revolving dome, covered with well oiled canvas or calico, and made with a wide opening and large shutters. The Rev. E. L. Berthon has described in the “English Mechanic,” October 13th, 1871, an observatory of this kind most admirably suited to shelter a reflector, as the temperature inside would be as nearly as possible that of the external air, and no annoyance from damp would be experienced. Where an observatory is not practicable the telescope might be protected by a close fitting covering of like make. Both the large and small mirrors should be protected by their covers (with which they are provided), when not in use, especially if left in the open air. The larger sized tubes have a door large enough to admit the cover and so allow of its being put on the large mirror without the necessity of the speculum being removed from the body of the telescope.

To Adjust the “Finder.”

Direct the telescope to any bright star (the Pole-star being by far the best, as it has very little apparent motion), and bring this star into the centre of the field of a low-power eye-piece. Now adjust the “finder” by means of the three screws bearing on it, till the star is bisected by the cross wires seen in the focus of the eye-lens of the “finder.” Change the low eye-piece to a high one, and perfect the adjustment as before described. Any well-defined terrestrial object at a distance can be employed in the day-time to roughly adjust the “finder,” leaving the final adjustments to be made by a star.

The use of Stops.

A stop 1/4 inch less in diameter than the speculum, is often useful, in order to cut off the internal reflections of the tube.

With mirrors 6-1/2 inches in diameter and under stops are seldom required; with the 6-1/2 inch a 5 inch stop may however sometimes be used with advantage on very bright objects. With an 8-1/2 inch mirror a 7 inch stop often improves planetary definition.

With larger sizes than 8-1/2 inches several stops of different diameter may be used, when experiment will determine what size is best suited to the condition of the atmosphere, and the character and brilliancy of the object to be observed. These stops can be easily cut out of thin cardboard and afterwards blacked with Indian-ink or lampblack.

On Observing the Sun.

No larger aperture than 4-1/2 inches should be employed for solar observation, except with a specially constructed “Solar Eye-piece,” as even a 4-1/2 inch speculum often concentrates sufficient heat to crack the coloured glass of an ordinary sun-cap, if exposed for any length of time. If a “solar eye-piece” is employed, the whole aperture may be used. In viewing the moon a slightly tinted glass is often most useful, especially to persons with weak sight, as it takes off a great deal of the glare.

To Silver and Polish the Specula.

The cost of silvering is trifling, and with cleanliness and ordinary care very little difficulty will be experienced. The apparatus and chemicals required consist of the following articles:—

Apparatus.—A Silvering Vessel:—This should be a flat-bottomed circular glass or glazed dish, 1 inch or more larger in diameter than the speculum to be silvered, and sufficiently deep to allow of a stratum of fluid of an inch or rather more between the face of the mirror and the bottom of the dish, the top of the mirror being nearly level with the edge of the dish.

A Mixing Vessel:—A 40 oz. glass measure will answer well, but care should be taken not to scratch the sides whilst stirring, or the glass is liable to fly. Should a measure not be procurable, any receptacle of sufficient size may be used, but a glass one is best, as it will allow of the action of ammonia being better observed.

A Box of Scales and Weights.

A Glass funnel and filtering paper.

Two Glass Rods for Stirring purposes.

A Five-ounce Glass Measure.

A Test tube 3/4 or 1 inch in diameter.

Some Clean Cotton Wool.

Some very fine Wash-leather.

A Support of Wood, on which to cement the speculum, described further on.

All these articles should be perfectly clean and free from dust, and the Glass ones well rinsed with distilled water just before using.

Chemicals.—Nitrate Silver.

Potash pure, precipitated by Alcohol.

Sugar of milk powdered.

Nitric Acid, pure.

Liquor AmmoniÆ.

Distilled water, pure.

Pitch.

Fine Rouge.

Turpentine.

Procure a strip of wood an inch or so less in diameter than the mirror, and of sufficient length to rest securely on the opposite sides of the silvering vessel. Pour on this piece of wood some melted pitch, and whilst it is still hot, place on it the back of the speculum moistened with a little turpentine; when cold, reverse, and lay the cemented speculum face downwards, suspended in the dish. Should the distance between the face of the mirror and the bottom of the dish be less than an inch, raise the mirror by means of thin wedges, placed between the strip of wood and the edges of the dish. But if, on the contrary, the mirror should be considerably more than an inch away from the bottom, which will occur if the silvering vessel is very deep, the speculum must be cemented to a block of wood of sufficient height, screwed to the suspending strip, instead of being cemented directly to the strip itself.

When the speculum is properly placed in the dish, namely, with the front surface about one inch from the bottom, pour in water till the fluid reaches about 1/4 inch up the side of the mirror. Measure this quantity, as it will indicate the total amount of the silvering solution required to be prepared.

To prepare the Silvering Solutions—make 3 standard solutions as follows—

No. 1.{	Nitrate Silver in crystals	100	grains.
No. 1.{	Distilled water	4	oz.
No. 2.{	Potash pure by alcohol	1	oz.
No. 2.{	Distilled water	25	oz.
No. 3.{	Powdered sugar of milk	1/2	oz.
No. 3.{	Distilled water	4	oz.

Solution No. 3 must be made just before using. The others will keep if the distilled water employed in their preparation is pure, and the solutions, when made, are kept in glass stoppered bottles.

Suppose it is desired to silver an 8-1/2 inch mirror, proceed as follows:—the total amount of solution required having been ascertained, as before described, pour 2 ozs. of solution No. 1 into the mixing vessel previously well washed and rinsed with distilled water, and cautiously add Liquor AmmoniÆ. A grey precipitate will be formed; continue to add the ammonia, drop by drop, till the precipitate is just dissolved and the solution becomes clear. The solution should be well stirred with a glass rod whilst adding the ammonia. Now add 4 oz. of solution No. 2, and re-dissolve the brown precipitate which is produced with Liquor AmmoniÆ as before described. There will now be about 6-1/2 oz. of solution. Subtract the 6-1/2 oz. from the total amount previously ascertained to be required, and the remainder will be the amount of distilled water to be added. Add half this quantity of distilled water to the 6-1/2 oz. of solution, and add a drop at a time of solution No. 1, till there is a slight precipitate, which cannot be re-dissolved by a considerable amount of stirring (say for 2 or 3 minutes); then add the remaining half of distilled water and cover up from dust the vessel containing the solution, so as to allow the slight precipitate to settle. There is a point of importance to be attended to, namely, that no more ammonia is employed than is absolutely necessary. The total amount of ammonia required in the 6-1/2 oz. of solution is about 2 drs.

To Clean the Mirror.

Fill the end of a test tube with cotton wool, leaving plenty outside the tube. Having poured a small quantity of strong nitric acid on the front of the mirror, rub the acid well all over the front and sides with the cotton wool brush. Place the speculum under a water tap for a few minutes till the acid is washed away, and finally well rinse with distilled water; then place it in the silvering vessel (previously thoroughly cleansed) and pour in distilled water till it reaches 1/8 inch up the side of the speculum.

To Mix the Solutions.

The precipitate having settled, pour into a clean vessel all that is clear of the solution, leaving about 2 oz. behind, which will be turbid with the precipitate, and therefore useless. The total amount will be afterwards made correct by the addition of the same quantity of solution No. 3. Having filtered solution No. 3, warm it to about 100° F. by allowing the bottle to stand in warm water, or by heating in a small flask. When everything is quite ready, add 2 oz. of the filtered solution No. 3, whilst warm, to the clear solution described above, and thoroughly mix.

To immerse the Mirror.

Remove the mirror from the distilled water, taking care not to touch the surface of the mirror, and wipe the back and edge with some clean cotton wool. If this precaution is not taken the water is liable to drain down the sides of the mirror whilst silvering, and cause streaks at the edge of the film. Having poured away the distilled water in the silvering vessel, substitute the mixed solutions, and directly the solution becomes slightly inky, gently immerse the mirror, taking care that no air bubbles, or specks of any kind, remain between the surface of the mirror and the solution. The mirror should not be removed from the bath until all the silver has been exhausted from the solution. This may be known by the solution being clear below the silver film on the surface of the liquid. The time required will vary from 45 minutes on a hot summer’s day, to 90 minutes when the thermometer shows a low degree of temperature. In the latter case it is better to have the silvering bath in a warm room. Immediately the mirror is removed from the bath, the silvered surface should be well washed by allowing ordinary water to flow on it from a tap, for five minutes or more, then finally rinse with distilled water and place the mirror to dry with the silvered surface resting on some blotting paper. It is as well if the mirror can be left undisturbed for a day or two, as the film will be firmer, but it may be polished, if desired, after drying for a few hours.

To Polish the Silvered Surface.

Make a couple of polishing pads by filling two pieces of very soft wash-leather about six inches square loosely with cotton wool, and tie them into balls. Gently remove any dust that may have settled on the film with some loose cotton wool, and then go over it with one of the pads in small circular strokes for about 15 minutes. This will consolidate the film and fit it for polishing. Spread a little of the finest rouge on a sheet of writing paper, and impregnate the other pad with it. Go over the film with the rouged rubber with the same circular strokes till it is perfectly polished, which will take another 15 minutes or so. Never commence with the rouged pad, as the surface may be injured. When once the film has been consolidated it will remain so, and can be repolished many times with the rouged pad should it get tarnished. The pads should be kept from dust in wide-mouthed bottles for future use. With care the film will last for a long time, especially if it is not allowed to get damp, and consequently the mirrors should never be brought uncovered from the cold air to a warmer temperature.

The “flat” may be silvered and polished in the same way as the speculum, using a smaller appropriate vessel for the silvering solution.

To Separate the mirror from the Wooden Support.

Should the mirror be attached directly to its support, insert a chisel between them, when one or two gentle blows will cause them to separate, but, should the mirror be cemented to a block, stand the mirror on edge, when a slight tap on the block will detach it. Scrape off any pitch that remains on the back of the mirror, using finally some turpentine to wipe it clean. Great care should be taken not to finger the film.

Martin’s process for Silvering.

Prepare four solutions of any quantity. Keep in stoppered bottles.

Solution 1.—Dissolve 175 grains of pure nitrate of silver in 10 oz. of distilled water.

Solution 2.—Dissolve 262 grains of pure nitrate of ammonia in 10 oz. of distilled water.

Solution 3.—Dissolve 1 oz. avoirdupois of pure caustic potash (prepared by alcohol) in 10 oz. of pure distilled water.

Solution 4.—Dissolve 1/2 oz. avoirdupois of pure sugar candy in 5 oz. of distilled water, then add 32 grains of tartaric acid and boil in a flask or other clean glazed vessel for 10 minutes, when cool add 1 oz. of alcohol and then dilute with distilled water, so as to make up the volume to 10 oz.

For silvering use equal parts of each, mix solutions 1 and 2 together, and 3 and 4; when the mirror is ready mix the whole together in the silvering vessel and quickly suspend the mirror.

In the summer time, if the solution cannot be kept in a very cool place, the mirror must be quite ready to be placed in the bath, as the solutions turn instantly when mixed together.

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SELECTED TESTIMONIALS

11, Wellington Park Terrace, Belfast,

July 7th, 1876.

Dear Sir,—The night before last was a clear night and I got the 6-1/2 inch out, and though the air was not good when using a 3-1/4 inch refractor, I was much pleased with the performance of the mirror.

Mr. W. came up about 11 o’clock and stayed till one, we got it on Saturn, and although rather low it was really a fine sight, Mr. W. was much pleased.

The moon being near to full we could not do much with faint points of light.

Yours sincerely, W. E. Parkinson.

Mr. G. Calver.

74, Hagley Road, Edgbaston,

November 27th, 1876.

Dear Sir,—I have now got the 5-inch speculum fairly into adjustment, and I am well pleased with it. Last night, the sky being clear for a short time, I turned it on the moon, the definition of minute craters was all that could be desired. I hope to have better opportunities.

I am, Yours truly, F. G. L.

Mr. G. Calver.

74, Hagley Road, Edgbaston,

November 21st, 1876.

Dear Sir,—I have mounted the 5-inch speculum on a simple equatorial and it works well. I am sure it will turn out a fine glass and I shall not regret the time and pains I have spent over it. It is not quite in adjustment yet, when it is it will afford me a treat. I have just tried it once on the Orion Nebula and Trapezium, details of Nebula well seen, and the 5th star in Trapezium easy.

I am, Yours truly, F. G. L.

Dowlais,

December 27th, 1876.

Dear Sir,—I have thoroughly tested the speculum, and am pleased to tell you it stood its trials well.

Yours truly, D. C. C.

Mr. G. Calver.

St. Denies, Southampton,

August 14th, 1876.

Dear Sir,—With reference to your enquiry as to the performance of the 6-1/2 in. reflector. I have pleasure in stating that I am perfectly satisfied. It readily divides the test objects and shows delta Cygni with as low a power as 160. The comes to Sirius may be considered an atmospheric test, perhaps, but I have repeatedly seen it. Your stand I find very steady and convenient; altogether I can fairly say that I consider that I have an instrument of considerable power at a comparatively small cost. I now find the attempt to observe with a refractor the reverse of pleasant.

The owner of a 3-inch refractor, after using my reflector, writes that he envies me its power, ease, definition, and comfort in observing.

I am, Dear Sir, Yours truly, A. H. S.

Hilgay Rectory,

February 20th, 1877.

Dear Mr. Calver,—The sky last night cleared up in places and enabled me to try the 10-inch; there was a slight haze, but I never saw discs so perfect and neat. I felt certain it would divide anything divisible. Clouds came up and put an end to work.

I am, Dear Sir, Yours sincerely, St. V. B.

25, Hamilton Terrace, St. John’s Wood,

May 26th, 1877.

My Dear Sir,—I have much pleasure in informing you that the very first time I saw Saturn through your 6-1/2-inch reflector, the definition of the planet was far superior to anything I had observed before, even with a good 4-1/4-inch refractor; and on another occasion I was greatly pleased with the clear and easy view of the “Comes” to e BoÖtis. But even without including the stars, the views of Saturn and Jupiter through my 6-1/2-inch mirror do alone (in my opinion) well repay the cost of the telescope.

Yours truly, Wm. L. Lancaster.

Mr. G. Calver.

37, Eaton Rise, Ealing,

February 13th, 1877.

Dear Sir,—I like the 18-inch speculum, and I think it as good as it can be, and if the larger one is as good I shall be delighted with it. It gives beautiful star images: I see Sirius as a brilliant dot, a glorious object without ray or flares of any kind. I never saw it so well before.

Yours truly, A. A. C.

Mr. G. Calver.

37, Eaton Rise, Ealing,

February 3rd, 1877.

Dear Sir,—I have tried the 18-inch speculum on some tests, and especially the satellites of Uranus, and it appears fine, very fine. What I have done in photography promises well.

Yours truly, A. A. C.

Mr. G. Calver.

Southend on Sea,

March 17th, 1877.

My Dear Sir,—Circumstances have prevented me from making many observations of late, but I am more confirmed in my opinion that my telescope of your make is a very fine instrument. (A 6-1/2-inch.) I heartily wish you success, which I feel sure you will obtain, as you are so painstaking and turn out a thoroughly reliable article. I shall be curious to compare my brother’s telescope with mine.

Sincerely yours, J. L. L.

Mr. G. Calver.

Gorlestone,

March 30th, 1875.

Dear Sir,—You have asked me for my opinion of the 10-inch speculum. I have tested it, and can speak in the highest terms of its performance. Definition in good air is as near perfection as it is possible to imagine. Such tests as ? Cancri, ?² AndromedÆ are well divided. The 6th star in the trapezium stands out well clear of its brighter neighbour. On the moon any power may be applied, only lessening the light, but retaining sharpness of outline. I have tried a good many telescopes, but never yet saw these 10-inch mirrors surpassed. The image of a star disc expanded on each side of the focus is of as nearly the same appearance as possible.

Yours truly, W. P. Matthews.

416, Brixton Road,

April 20th, 1875.

Dear Sir,—In compliance with your request, I send particulars of my observation on f Draconis. It was about 12.45 this morning when I directed my 8-1/2-inch to this object, the air was very unsteady, in fact not nearly so good as some nights lately, and I well divided it with a power of 450. I then used a 6-1/2-inch stop, which I found very much increased the steadiness of definition.

Yours very respectfully, P. H.

10th July, 1874.

Dear Sir,—I tried the 6-1/4-inch mirror I had from you for the first time last night. The night was not a good one for definition, but I was very much pleased indeed with its performance.

Yours truly, C. H. W.

Honiton Rectory,

Dec. 23rd, 1874.

Dear Sir,—I have been wishing to tell you how pleased I am at the performance of your mirror. Many thanks for your kind offer to change the mirror if needful, but I think it could hardly be better than it is, its performance on different double stars is most excellent. I have examined nearly 100 of these since September with the 6-1/2-inch, most of them very difficult, but the mirror came out well under all tests. I send you a list of some of the objects I have examined.

Yours truly, H. Sadler.

p AquilÆ.—Divided, power 80. 14-^m. Webb might have been rated 15-^m. [6-^m., 7-^m. 1·5.]
d AquilÆ.—[a3-1/2, b16, c14, a-b96, a-c194.] Comites easy, 3 other excessively minute ones, not shown by the 11-in. refractor with which P. Smyth measured B.C. Found 6-1/2-in. Sept. 12th, est. ± 17 mag. 100 to 110.
? Persei.—My friend “Linea” sees two minute stars with 4·28-in. Wray, not in Webb, and Wray himself sees an excessively difficult companion. I see these 3 stars easily with 6-1/2-in. (Wray says his companion is “very difficult with 7-in. refractor, really only a glimpse star, even with the best atmosphere”), and have added two more stars to the group.
Delphini.—Close double discovered by Burnham, est. 0·7. In contact 6-1/2-in., power 430.
? CoronÆ Borealis.—Very low, long past meridian, in contact 164 power.
Equalei.—[a5-1/2, b13, c14, b16: a-b35, a-c50, b-B3.] 16-^m. not seen, Webb 9-1/3-in. Just divided 164, easy 430 power. Two other companions (not seen by Smyth or Webb?)
AndromedÆ.—The 16-^m. comes, a very difficult test, easy; other comites (not seen by Smyth or Webb?) seen.
Companion to Vega pretty easy, Nov. 12th, 37m. after sunset.
P. 178 xx. Delphini.—[a7-1/2, b8, c16, b9: a-b14·3, b-b0·7, a-c20.] Smyth 16 by evanescent glimpses; easy 164 power, 6-1/2-in. 8-^m. well elongated in direction of 230°, power 430.

Regent Road, Great Yarmouth,

October 24th, 1874.

Dear Sir,—Doubtless you have anticipated hearing from me, relative to the 10-inch telescope, but the weather has been so indifferent for delicate astronomical work that it has not yet had a fair trial.

In middling good air, when I could use a reduced aperture with satisfactory results, the star images reminded me of the 6-1/2-inch, which I considered so superb a mirror that nothing could surpass its fine performance either on stars or planets.

With the recollections of the truly splendid views I had of Jupiter last season, I count much to see him with the 10-in.

Yours truly, H. Blyth.

Regent Road, Great Yarmouth.

February 2nd, 1875.

Dear Sir,—In reply to yours, I have not had a really good night to test severely the defining powers of the 10-inch mirror, but judging from the few difficult objects I have seen, the mirror promises well, and I have no doubt of its excellence.

I had a fine view of the grand nebula in Orionis, and noticed that the 5th and 6th stars were quite plainly seen, when the aperture was reduced to 5-1/2-inches. I consider your stand a great improvement, being very convenient and steady.

Yours truly, T. Ayers.

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