MIRROR BLANKS AND TOOLS


Telescopes & Astronomy Mirrors
Galaxy Optics Mirrors
Nova Optics Mirrors
Standard Mirrors

Plate Glass: Plate Glass is the least expensive material to build a mirror from.  The thicker the 
glass, the less is will bend out of shape if the mirror is to be large.  Thinner 
glass is perfectly well to work with as long as the glass is supported properly in the finished
 telescope.  Thinner glass is less expensive and reduces the overall weight of the telescope.
To reduce the cost further, the Tool Glass doesn't have to be as thick as the Mirror Glass.
Sizes available: 1" (100mm) to 25" (635mm) diameter.

PLATE GLASS
150mm (6") diameter x 25mm (1") thick $50
150mm (6") diameter x 19mm (3/4") thick $45
200mm (8") diameter x 25mm (1") thick $75
200mm (8") diameter x 19mm (3/4") thick $68
254mm (10") diameter x 25mm (1") thick $110
254mm (10") diameter x 19mm (3/4") thick $99
305mm (12") diameter x 25mm (1") thick $162
305mm (12") diameter x 19mm (3/4") thick $145
330mm (13") diameter x 25mm (1") thick $170
330mm (13") diameter x 19mm (3/4") thick $155
457mm (18") diameter x 25mm (1") thick $365
457mm (18") diameter x 19mm (3/4") thick $335
457mm (18") diameter x 16mm (5/8") thick $315
500mm (19.6") diameter x 25mm (1") thick $425
600mm (23.6") diameter x 25mm (1") thick $480

SUPRAX GLASS (LOWER EXPANSION THAN PYREX - REALLY GOOD SHINE)
100mm diameter x 23-26mm thick $58
148mm diameter x 24mm thick $65
175mm diameter x 28-31mm thick $125
198mm diameter x 30mm thick $145
250mm diameter x 30mm thick $220

Other Materials, Diameters and Thicknesses available, please enquire.

Pyrex: Pyrex has a lower expansion rate than glass.  When there is a change of temperature, 
either by the conditions where the telescope is being used or by the heat generated by the 
hands while grinding or polishing, pyrex will be less effected.  Since Pyrex is harder than 
glass the grinding and polishing time is longer.  Pyrex blank thickness is a ratio of 6:1 
which is the theoretical thickness best suited for mirror making.
Sizes available: 1" (25mm) to 40" (1016mm)

Pre-generated Pyrex:  These blanks have the focal ratio curve already made so minimal grinding 
needs to be done.  It also aids in obtaining the correct curve which can be difficult for the 
beginner mirror maker.  The tool supplied is a matching curve.
Sizes available: 1" (25mm) to 40" (1016mm)

Fused Silica: Larger diameter mirrors tend to bend under their own weight.  
Fused silica between thin blanks supports the mirror and also keeps the weight to 
a minimum.  These blanks have the lowest expansion rate and are also the most 
expensive.  Flat surfaces or pregenerted blanks are available.

Light Weight: Thin Pyres blanks are available which are less than 
the recommended theoretical 6:1 ratio thickness.

Pyrex Schmidt-Cassegrain:  It doesn't take much more to make a 
Schmidt-Cassegrain mirror.  Blanks are supplied with a started hole in the 
middle eliminating having to drill.  The primary mirror is a full parabola and the 
secondary is a hyperbola.

Custom Blanks: Different shapes and sizes are available.  Let us know your specifications.

GRINDING AND POLISHING MATERIALS
Aluminium oxide grinding powder per kilo				$40AUS
Tin oxide grinding powder per kilo				$30AUS
Pumice grinding powder per kilo				$30AUS

80 Grade grinding powder per 8" mirror				$2AUS
120		"		"			$2AUS
220		"		"			$3AUS
320		"		"			$4AUS
500		"		"			$6AUS
1000		"		"			$8AUS
1600		"		"			$8AUS
Cerium Oxide		"				$8AUS
Lap resin kit		"				$15AUS


SECONDARY/DIAGONAL MIRRORS
Secondary Mirrors available in all sizes from 15mm to 215mm.  All measurements are taken across 
the narrow diameter (minor axis) of the mirror.

CHOOSING THE CORRECT SECONDARY/DIAGONAL SIZE
The size of the diagonal is measured by its width across the mirror (minor axis).
To work out what size Secondary Mirror is needed for the telescope, things need to be worked 
out in order. Knowing the diameter of your Main Mirror. Firstly, find the focal length of the 
completed mirror.  Secondly, work out the height of your focusing unit.  The focuser needs to 
be wound out about 25mm (1") (roughly where you expect the focus or eyepiece to be) then take 
the height measurement.  Thirdly, the outside diameter of the telescope tube (where the focuser 
will go) needs to be measured and halved.  Having these measurements, the Secondary Mirror size 
can now be worked out.  Add the height of the focuser to the halved outside diameter of the 
telescope tube. This gives the distance from the Secondary Mirror to the eyepiece.

The formula now used is:

Main Mirror diameter divided by Focal length times the distance from the diagonal to the eyepiece.

eg. Main Mirror Diameter 200mm (8")
    Focal Length = 1000mm
    Height of Focuser = 70mm
    Outside Diameter of Tube = 230mm divided by 2 (half) = 115mm
    Total distance from Secondary to Eyepiece = 70mm + 115mm = 185mm

Using Formula:

eg. 200mm divided by 1000mm times 185mm = 37mm diameter Secondary Mirror.

Take note that the diameter of the diagonal across the Minor Axis is about 1mm less 
due to the glass being beveled

Most common Secondary Mirror bought in Bulk
34mm Standard Secondary Mirror, Coated		$35AUD

Highest Quality Pyrex 1/10 Wave Secondary Mirrors with Enhanced Coatings
Commonly kept sizes:
25.4mm (1") dia				$55AUD
28mm (1.1") (dia				$60AUD
31mm (1.25") dia				$65AUD
32mm (1.33") dia				$68AUD
33mm (1.29") dia				$70AUD
35mm (1.37") dia				$75AUD
40mm (1.57") dia				$80AUD
42mm (1.65") dia				$85AUD
46.5mm (1.83") dia				$95AUD
50mm (1.97")") dia				$105AUD
50.8mm (2") dia				$109AUD
62mm (2.44") dia				$160AUD
63mm (2.48") dia				$165AUD
65mm (2.56) dia				$180AUD
70mm (2.76) dia				$220AUD

Standard Quality BK7 1/6 Wave Secondary Mirrors with Coating
Commonly kept sizes:
28mm (1.11") dia				$35AUD
31mm (1.22") dia				$40AUD
41mm (1.62") dia				$45AUD
50mm (1.97") dia				$50AUD
63mm (1.33") dia				$60AUD
70mm (1.29") dia				$70AUD

SECONDARY HOLDERS
3 Vane Secondary Holder and Spider 6"				$70AUD
4 Vane Secondary Holder and Spider 6"				$75AUD
3 Vane Secondary Holder and Spider 8"				$75AUD
4 Vane Secondary Holder and Spider 8"				$80AUD
3 Vane Secondary Holder and Spider 10"				$80AUD
3 Vane Secondary Holder and Spider 10"				$85AUD
3 Vane Secondary Holder and Spider 12.5"			$110AUD
4 Vane Secondary Holder and Spider 12.5"			$120AUD
2 Vane straight Secondary Holder straight type over 12.5" start at	$90AUD

FINDERSCOPES
S/H 60mm Refractor lens, F/11.6, Screw type 			$30AUS
S/H 6x30mm Finderscope mount, 6 screw, 2 screw attach 		$25AUS
S/H 6x30mm Finderscope mount, 3 screw, 2 screw attach 		$10AUS
S/H 5x24mm Finderscope mount, 6 screw, 4 screw dual attach 	$10AUS
S/H Tube tripod legs, Heavy steel, Extendable, 4'6" (115cm) 		$15AUS

OPF630 Optex 6x30mm Finderscope				$95AUS
OPF850 Optex 8x50mm Finderscope				$130AUS
Siebert 10x50mm Finderscope with 90 degree diagonal		$285AUS
Siebert 6x50mm Red lighted illuminated reticle,
	90 degree diagonal, With high eye relief eyepiece		$430AUS
Siebert 10x50mm Red lighted fibre optic reticle,
	90 degree diagonal, With high eye relief eyepiece		$490AUS
Meade 5x24mm Finderscope and mount 				$35AUS
Pin hole finderscope 						$5AUS
5x24mm Finderscope mount, 3 screw scope, 2 screw attach 		$10AUS
Tasco 5x24mm Finderscope mount, 3 screw adjust, 2 screw attach 	$15AUS
STFS850   8x50 Black Finder 				$112AUS
STFB850   50mm Dovetail Bracket 			$74AUS
STFS630   6x30 Black Finder 				$85AUS
STFB630   30mm Dovetail Bracket			$65AUS
STLS      LightSight Red Dot 				$68AUS
STLSB     Extra Base for LightSight 			$9AUS
Telrad 1x, illuminated reticle bulls eye, Excellent device		$82AUD
Telrad Dew Shield					$28AUD
Mounting Base only					$18AUD
Telrad Pulser						$39AUD
Telrad Dew Shield+					$42AUD
(w/mirror for 90° viewing)
Telrad 2” Riser Base				$32AUD
Telrad 4” Riser Base				$32AUD
Reticle						$8AUD
Lens							$16AUD
Combining Glass (clear or tinted)			$12AUD
Potentiometer					$12AUD
Thumb Screw (steel w/plastic knob)		$2AUD
Thumb Screw (brass)				$3AUD


FOCUSING UNITS
There are many types of Focusers available in 32mm (1.25") or 50mm (2") diameters. Heavy duty 
"Crayford" style Focusers are recommended if the weight of a camera is to be attached to the 
telescope.

The lower the profile of the Focuser, the smaller the secondary mirror.  Firstly, smaller 
mirrors are cheaper and secondly, they create less obstruction to the main mirror giving higher 
definition (clarity).

Reflector Slide 1.25" $40AUS
Reflector Rand and Pinion (small) 1.25" $70AUD$ or $43US$
Reflector Rack and Pinion (large) 1.25" $90AUD$ or $54US$
Reflector Rack and Pinion 1.25"/2" $110AUD$ or $66US$
AstroSystems Phase 1 Low Profile Crayford Type 1.25" Teflon Bearings $150AUS
AstroSystems Phase 4 Low Profile Crayford Type 1.25"/2" Steel Bearings $250AUS
STNF125   * 2" Newtonian Focuser			$112AUS
STNF2125  * 2" to 1.25" Newtonian Focuser		$134AUS
STRF125   * 1.25" Refractor Focuser			$118AUS

VARIOUS PARTS
8" Single arm, Aluminium, Secondary mirror holder, 2 screw adjust	$10AUS
6"x7/8" (153x22mm) Blank and tool 				$75AUS
Secondary mirror, 1.33" (33mm), 1/10 wave, Enhanced coating 	$75AUS
Secondary mirror, 1.83" (46mm), 1/10 wave, Enhanced coating 	$90AUS
6" Mirror box, Posting etc. 					$10AUS
6" Mirror cell, Aluminium 					$40AUS
Teflon Bearing Kits suit 8" Dobsonians				$45AUS

TUBES
All sizes available.  Please specify optics to be used for compatability.
Carbon Fibre Tubing is now available for telescope builders.  Let us know your requirements 
including length, diameter and wall thickness and we'll quote.  Don't forget your location if a 
shipping quote is needed.

ALUMINISING AND SILVERING
The aluminium coating placed onto the surface of the glass returns about 90% reflectivity.
The overall reflectivity combined with the secondary mirror drops down to about 80%.
Different enhanced coatings brought out by manufacturers can bring this figure back up to 
around 90%. It is possible to get more reflectivity from a mirror by using silver for the
coating. The reflectivity can go up to 95% overall but there are disadvantages. Silvering, 
although cheaper, is messy to do yourself and will only last up to a year or two. In comparison
aluminising will last up to ten years. If you wish to silver your mirror, do it just before 
you have a big session of observing to get the most out of it before it fades.

The following aluminsisng prices include enhanced overcoating for maximum reflectivity.  Mirrors, 
once recoated, need to be sent back to their owners in a mirror box.  This prevents the coating 
from being scratched or rubbed off.  We can supply a mirror box if you don't have one, or we can 
tell you how to make one easily.

We also have a refiguring service.  Many Chinese telescopes have a spherical shaped mirror 
instead of a parabolic shaped mirror.  The difference in shape isn't much, but the result of 
the image is, especially using high magnification.  Some mirrors are just not accurate enough 
to produce good images.  We can refigure the mirror to the correct shape before adding the new 
coating.  Please inquire.

ALUMINISING
Enhanced, Multi-Coating
4.5" (114mm)	$150AUD$ or $104US$
6" (153mm)	$165AUD$ or $114US$
8" (200mm)	$180AUD$ or $124US$
10" (254mm)	$200AUD$ or $137US$
12.5" (318mm)	$240AUD$
16" (406mm)	$290AUD$
18" (457mm)	$360AUD$

SILVERING
4.5" (114mm)	$60AUD$ or $42US$
6" (153mm)	$75AUD$ or $51US$
8" (200mm)	$90AUD$ or $50US$
10" (254mm)	$110AUD$ or $76US$
12.5" (318mm)	$140AUD$
16" (406mm)	$180AUD$
18" (457mm)	$230AUD$

Please inquire for larger size mirrors.

MOUNTS
DECENT MOUNTS FOR ACCURATE TRACKING
Having a decent mount for accurate tracking is becoming more popular as they become more
 affordable.  Accurate mounts are used for a number of things including computer guided 
telescopes, accurate encoder locating (see below) and astrophotography.  Of course, you only 
get what you pay for, although with right know how, many mounts can be improved to greatly 
increase their accuracy.  Once these mounts are improved the Vixen SkySensor 2000 PC can be 
attached.

VIXEN GP-DX
One of the best mounts available is the Vixen GP-DX.  The mount comes as the 'mount head only'
 with a tripod or pier needed to complete it.  Included with the mount head is slow motion 
controls, polar alignment scope, bubble level and built in illuminator.  The GP-DX can have a 
dual axis drive added.  The mount can handle upto 10kg easily.  Vixen SkySensor can be attached
 to the GP-DX (see below).

SKYWATCHER EQ5
There are a few copies of the Vixen GP-DX mounts available.  The EQ5 comes complete with 
tripod.  It can have single or double axis motor drive attached.  Standard features of the EQ5 
include a built-in holder for polar scope, a latitude adjuster with micrometer scale, an 
azimuth polar-alignment adjuster, slow-motion tracking controls, and a bubble level.  The EQ5 
can be greatly improved and the best way to do this is to follow the guidelines set out by 
AstroBoy at his site:

http://www.astronomyboy.com/

Once the EQ5 has been improved, the Vixen SkySensor 2000 PC (see below) will work accurately 
and can be attached without difficulty (bolts straight on).

SKYWATCHER HDEQ5MNT
This is the heavy-duty version of the EQ5 mount and is a smaller version of the sturdy EQ6 
mount. It is able to handle around 12kg. (up to 10" reflector)  The HDEQ5MNT includes dual axis
 drive, built-in polarscope for both North and Southern Hemisphere use, large R.A. and DEC. 
locking clamps and retractable counterweight shaft and counterweight.  The tripod has 1.5"-
diameter steel legs.

Once again, when the HDEQ5MNT has been improved, the Vixen SkySensor 2000 PC 
(see below) will 
work accurately and can be attached without difficulty (bolts straight on).

SKYWATCHER EQ6
This is the largest and heaviest mount. This mount can handle a 12.5" Reflector or similar (up 
to 18kg).  Features include built-in polarscope for both North and Southern Hemisphere use, 
large R.A. and DEC. locking clamps, dual axis drive, and retractable counterweight shaft and 
counterweight.  The field tripod has adjustable height, incorporating 2"-diameter steel tripod 
legs.

Same again, once the EQ6 has been improved, the Vixen SkySensor 2000 PC (see below) will work 
accurately and can be attached without difficulty (bolts straight on).  Further information 
about the SkySensor and the EQ6 can be seen on this site:

http://www.iteastronomy.com//products/accessories/overview.php?p=EQ-6+MOUNT

CELESTRON CG5
The Celestron CG5 is basically the same as the EQ5.  The CG5 has the Polar Alignment tool as 
an optional extra.  AstroBoy gives the CG5 a full going over on his site:

http://www.astronomyboy.com/

Same again, once the CG5 has been improved, the Vixen SkySensor 2000 PC (see below) will work 
accurately and can be attached without difficulty (bolts straight on).

Call or email for further information.

CELESTRON CG5 COMPUTERISED MOUNT
This is the same mount as the CG5 with computerised GOTO and object database.  Celestron has 
all the specifications on the following page:

http://www.celestron.com/prod_pgs/tel/c8sgt.htm

CELESTRON CGE COMPUTERISED MOUNT
This is Celestron's top of the line mount.  I haven't seen one personally yet, although, going 
by the reviews it is a very good mount indeed.  The largest telescope Celestron place on it is 
the 14" Schmidt-Cassegrain which weighs 20kg (45 pounds).  This doesn't include any extra 
accessories which could be an extra 2kg.  The best way to see the specifications is to go 
straight to Celestron's web page:

http://www.celestron.com/prod_pgs/tel/cge_index.htm

Any additional information can be obtained from us.

VIXEN SKYSENSOR 2000 PC
Probably the best update to the GP-DX is encoders (see below) or the Vixen SkySensor 2000 PC. 
 SkySensor enables the telescope to be attached to a PC to use astronomical software 
(see below also).  SkySensor has many features including:

- high speed search of objects
- 13,942 objects in data base plus 30 additional
- remote auto centering
- periodic error correction
- compatable with any optical tube
- automatic tracking of satellites
- atmospheric correction

Vixen's web site:
http://www.vixen-global.com/

Telescopes and Astronomy's Vixen Pages:
http://www.telescopes-astronomy.com.au/vixen103.htm
8" Dobsonian mount unassebled, unpainted, with bearings $230AUS
10" Dobsonian mount unassebled, unpainted, with bearings $280AUS

EYEPIECES, BARLOWS ETC.
6601 1" (25.4mm)dia.	4mm Huygen			$43AUS
6620		"	5mm Huygen			$43AUS
6605		"	9mm Huygen			$43AUS
6607		"	12.5mm Huygen			$43AUS
6608		"	20mm Huygen			$43AUS
3514		"	10mm Kellner - Japan		$158AUS
3515		"	20mm Kellner - Japan		$158AUS
3516		"	25mm Kellner - Japan		$158AUS
6610		"	25mm Kellner - Taiwan		$68AUS
6602		"	4mm Orthoscopic - Japan		$198AUS
3511		"	9mm Orthoscopic - Japan		$179AUS
3512		"	12.5mm Orthoscopic - Japan		$179AUS
3518		"	25mm Orthoscopic - Japan		$224AUS
3671	"	Vixen K25mm,	"	"		$132AUS
6631 1.25" (31.7mm)dia.	6.3mm Kellner			$85AUS
Special 9mm Kellner 1.25"					$50AUS
Special 25mm Kellner 1.25"					$50AUS
6632		"	12.5mm Kellner			$85AUS
6633		"	25mm Kellner			$85AUS
6636		"	7.5mm Super Plossl			$125AUS
6637		"	17mm Super Plossl			$125AUS
6633		"	25mm Super Plossl			$125AUS
OPP4		"	4mm Plossl			$69AUS
OPP6		"	6mm Plossl			$69AUS
OPP9		"	9mm Plossl			$69AUS
OPP15		"	15mm Plossl			$79AUS
OPP25		"	25mm Plossl			$79AUS
OPP40		"	40mm Plossl			$89AUS
3668		"	18mm Orthoscopic			$158AUS
3683		"	25mm Orthoscopic			$158AUS
VIXEN LV SUPER VIEW
3714		"	2.5mm Lanthanum			$264AUS
3715		"	4mm Lanthanum			$257AUS
3716		"	5mm Lanthanum			$237AUS
3717		"	6mm Lanthanum			$224AUS
3864		"	7mm Lanthanum			$237AUS
3718		"	9mm Lanthanum			$237AUS
3719		"	10mm Lanthanum			$224AUS
3865		"	12mm Lanthanum			$237AUS
3756		"	15mm Lanthanum			$237AUS
3757		"	20mm Lanthanum			$264AUS
3758		"	25mm Lanthanum			$336AUS
3777		"	8-24mm Lanthanum			$336AUS
3759		"	30mm Lanthanum			$356AUS
3745		"	50mm Lanthanum			$283AUS
3707		"	K70mm Lanthanum			$290AUS
VIXEN LVW SERIES
3856		"	3.5mm Lanthanum - Long eye relief	$442AUS
3857		"	5mm Lanthanum - Long eye relief	$442AUS
3895		"	8mm Lanthanum - Long eye relief	$411AUS
3896		"	13mm Lanthanum - Long eye relief	$430AUS
3897		"	17mm Lanthanum - Long eye relief	$442AUS
3898		"	22mm Lanthanum - Long eye relief	$442AUS
3727		"	42mm Lanthanum - Long eye relief	$586AUS
3759 2" (50.8mm) dia.	30mm Lanthanum - Long eye relief	$415AUS
3745		"	50mm Lanthanum - Long eye relief	$330AUS
3707		"	70mm Kellner - Long eye relief (30.6mm)	$330AUS
VIXEN PLOSSLS
3625		"	7.3mm Plossl			$135
3626		"	9.5mm Plossl			$135
3627		"	13mm Plossl				$143
3620		"	26mm Plossl				$150

PENTAX XL EYEPIECES
Extra low dispersion (ED) glass, super multi-coatings, 65 degree apparent 
field of view, 20mm eye relief.
Pentax	5.2mm					$CALL
Pentax	7.0mm					$CALL
Pentax	10.5mm					$CALL
Pentax	14mm					$CALL
Pentax	21.0mm					$CALL
Pentax	28.0mm					$CALL
Pentax	40.0mm					$CALL

TELE VUE EYEPIECES - Please inquire
6619 1" (25.4mm) barrel, 1.5x Erecting image tube/lens		$30AUS
6621 6-18x Zoom erecting image tube/lens			$62AUS
3530 Vixen 25mm dia. 2x Barlow				$85AUS
3531 Vixen 25mm dia. 3x Barlow				$103AUS
3677 Vixen 32mm dia. 2x Barlow				$113AUS
3678 Vixen 32mm dia. 3x Barlow				$138AUS
3674 Vixen 32mm dia. 2x Barlow DX				$245AUS
3709 Vixen 50.8mm dia. 2x Barlow				$390AUS
Siebert 1.25" (32mm)7mm, 4 element, coated, 65d FOV., 6mm E.R	$130AUS
Siebert 1.25" (32mm)12.5mm, 3 element, coated, 65d FOV, 7mm E.R	$125AUS
Siebert 1.25" (32mm) 18mm, 4 element, coated, 65d FOV, 7mm E.R	$125AUS
Siebert 1.25" (32mm) 21mm, 3 element, coated, 80d FOV, 7mm E.R	$125AUS
Siebert 1.25" (32mm) 29mm, 6 element, coated, 52d FOV, 25mm E.R	$199AUS
Siebert 1.25" (32mm) 32mm, 6 element, coated, 52d FOV, 27mm E.R	$199AUS
Siebert 1.25" (32mm) 35mm, 6 element, coated, 50d FOV, 27mm E.R	$199AUS
Siebert 1.25" (32mm) 45mm, 6 element, coated, 42d FOV, 29mm E.R	$220AUS
Siebert Binoc. viewer, high quality, 2x 21mm SWA Eyepieces free!!	$999AUS
Siebert 1.5x Barlow for Binoc. viewer, 1.25" (25mm)		$442AUS
Siebert 1.5x Barlow for Binoc. viewer, 2" (50.8mm)			$499AUS
Siebert 2" (50.8mm)19mm Wide angle, Coated, 75d FOV, 8mm E.R	$335AUS
Siebert	"	 32mm Wide angle, Coated, 67d FOV, 24mm E.R	$335AUS
Siebert	"	 35mm Wide angle, Coated, 62d FOV, 26mm E.R	$335AUS
Siebert	"	 38mm Wide angle, Coated, 60d FOV, 26mm E.R	$335AUS
Siebert	"	 45mm Wide angle, Coated, 57d FOV, 27mm E.R	$335AUS
Siebert	"	 51mm Wide angle, Coated, 52d FOV, 27mm E.R	$335AUS
6635 25mm to 32mm Diagonal prism eyepiece adaptor		$23AUS
6630 25mm to 32mm Eyepiece adaptor				$6AUS
6631 32mm to 25mm Eyepiece Adaptor sleeve			$2AUS
Eyepieces 1" dia., Inexpensive replacements, Huygens, 4,8,12.5mm	$10AUS
Barlow eyepiece 2x, 1" dia., Inexpensive replacement 		$10AUS

STWA14    * 14mm WA Eyepiece/Adapter (Nikon)		$EMAIL
STWA18    * 18mm WA Eyepiece/Adapter (Nikon)		$EMAIL
STZ721    * 1.25" Zoom Eyepiece 7-21mm			$EMAIL
STMV40    * MaxView 40mm Eyepiece/Adapter			$EMAIL
STPL04    4mm ST Series Plossl				$EMAIL
STPL06    6mm ST Series Plossl 				$EMAIL
STPL09    9mm ST Series Plossl				$EMAIL
STPL15    15mm ST Series Plossl 				$EMAIL
STPL25    25mm ST Series Plossl 				$EMAIL
STPL30    30mm ST Series Plossl 				$EMAIL
STPL40    40mm ST Series Plossl				$EMAIL
ST2EP26   26mm ST Series 2" Eyepiece				$EMAIL
ST2EP32   32mm ST Series 2" Eyepiece				$EMAIL
ST2EP40   40mm ST Series 2" Eyepiece				$EMAIL

ASTROSYSTEMS PARTS FOR LARGER TELESCOPES

Eyepiece Adapter 50mm to 32mm, threaded for 48mm filters		$CALL
Low eyepiece adaptor 50mm to 32mm, extra 13mm lower		$CALL
Heavy Duty Spiders						$CALL
Secondary Holders						$CALL
Lower Truss Fasteners					$CALL
Upper Truss Clamps						$CALL
Pivot Kit							$CALL
Teflon Bearing Kits						$CALL


WHAT'S THE BIG IDEA?
The larger a telescope is, the higher the light gathering power, resolution 
and magnification capabilites.

Prices Go Up and Down. Please Call or Email to confirm Price and Availability.
		

TELESCOPE MIRROR MAKING
WHAT'S INVOLVED WITH MAKING A TELESCOPE MIRROR?
The reflecting type telescope mirror can be made at home easily and inexpensively.  Making your 
own mirror also allows the builder to choose their own focal ratio.  The finished mirror will, 
hopefully, be better than the average mirror bought commercially, or with TIME, PRACTISE and 
PATIENCE, a hell of a lot better than obtained commercially. TIME - The longest and 
harder part about making a mirror is the polishing and repeated testing of the mirror until a 
sphere shape is reached.  An 8" diameter will take up to 50 hours of polishing which must be 
completed in no less than 1/2 an hour sessions. PRACTISE - To aquire the final shape 
(parabola) of the mirror a few minutes of accurate polishing work needs to be done right at the 
end.  PATIENCE - If you're not happy with the final shaping, the mirror is polished a 
bit more until its returns to the sphere shape and another attempt is made to reach the 
parabola.  Its perfectly ok to fluke it too as long as you started with a sphere.

BUT WHAT AM I ACTUALLY DOING?
Rubbing 2 disks of glass together.  If you have a look at the "Web Making Ring" link at the 
bottom of the page you will see a pair of hands working at it.  If the top piece of Glass 
(mirror) overhangs the bottom glass (Tool) by half (center over edge), as the top piece moves 
around the edge of the bottom piece the top one will wear in the middle and the bottom one will 
wear on the edge.  Eventually one will become concaved and the other will be convexed.  
Depending on what type of stroke is used between the 2 pieces of glass, determines where the 
glass is removed for us to obtain a sphere.  There are only 3 general strokes used.

BUILDING TIP:
Many keen telescope builders make a 6" or 8" first off.  This is excellent practise for making 
a larger mirror.Don't try to make your secondary mirror, its not worth the time effort and 
expense.

STARTING THE PROCESS OF GRINDING MIRROR:
First things first!  As the mirror is ground and then polished we use finer compounds.  This 
means once the first grade of compound is finished with, the whole area and mirror needs to be 
cleaned, throughly, so none of the first grade contaminates next finer grade and causes a 
scratch larger and deeper.  The cleanup it done after each grade.  When it comes to the final 
process of polishing, its important that nothing contamintes the process.  The smallest 
particle of dirt, grinding compound or even dust can cause a scratch or put a sleek on the 
mirror surface.  If its a nasty, deep, large scratch or sleek, going back to fine grinding 
(1600) will need to done to remove the scratch.  The mirror will have to be polished again.  
Don't take the chance with cleanliness, as it will result in heart ache and time.

GRINDING AND POLISHING MATERIALS
Aluminium oxide grinding powder per kilo				$40AUS
Tin oxide grinding powder per kilo				$30AUS
Pumice grinding powder per kilo				$30AUS

80 Grade grinding powder per 8" mirror				$2AUS
120		"		"			$2AUS
220		"		"			$3AUS
320		"		"			$4AUS
500		"		"			$6AUS
1000		"		"			$8AUS
1600		"		"			$8AUS
Cerium Oxide		"				$8AUS
Lap resin kit		"				$15AUS

RESIN  LAP  PREPARATION
For polishing the tool is replaced by the Resin Lap.

Tropical Lap
This lap was initially introduced by Dr. C. Tenukest at the Optical Department of the 
University of New South Wales.   We have uesed it for many years and find it superior 
to most pure pitch laps.

Use good ventilation when preparing resin.

Using an old saucepan or similar, on low heat, gently heat and stir all of the resin until 
fully melted.

Add all of the woodflour and mix in thoroughly.

Mix in Castor Oil, 30ml (8" diameter lap) to start with, and progressively test the hardness 
of the mix before pouring the lap.  A bottle top or bottom of drink can is ideal for pouring 
a test sample.

The thumb nail test over about 30 seconds should produce an indentation with slight raising 
of the surrounding area.  If the lap is too hard, add more Castor Oil and gently melt and 
stir the mix for a few more minutes.  Make sure it mixed properly.

Make sure the mix is liquid enough so it doesn't solidify while being poured onto the Tool.  
A thickness of around 5 or 8mm is fine.

Two thicknesses of paper will be enough, as a wall around the Tool, to stop it running over 
the side.

Once the lap is cooled, the paper can be torn off.

Looking After Your Lap
The lap needs a series of channels running horizontal and vertical impressed or cut into it.  
These channels hold the polishing
 paste while polishing and also help cut into the mirror for faster polishing.  The channels need 
to be offset from the center of 
the tool as this will cause a repetative polishing action in the very center of the mirror.  Polishing 
has to be evenly random all over.

The lap resin needs to be warm before any manipulation can be done.  This can be done by 
sitting the tool and resin in hot water for several minutes.  The channels can be made by different 
methods.  Firstly, cutting "V" shaped channels with a knife.  Secondly, using a flat peice of metal 
around 3mm thick to press the channel lines one at a time.  Thirdly, using a grid, made of plastic, 
rubber or Nylon, press the lines into the lap resin by placing the mirror face down, sandwiching 
the grid.  Weight can be added.  It's important to coat the grid, lap resin and mirror with 
polishing paste so they don't stick together.













Channels cut into the lap resin

As the polishing process flattens out the lap resin, the channels need to be re-cut or impressed.  
Also, as the lap resin flattens out, it gets wider than the diameter of the tool.  It is important to 
keep the resin lap trimmed as least 2mm less than the tool diameter.  Not keeping the lap resin 
trimmed will cause the the hardest to correct fault in the mirror - the "turned down edge".

Hot and Cold Pressing
Once the resin lap is channeled and trimmed, hot or cold pressing needs to be done.  The
 idea of the pressing is to get the mirror to fully contact the lap resin for polishing.  This is 
important for even polishing.  Hot pressing is quickest, although it may press flat all your 
channels if done for too long.  This is trial and error.  Hot pressing is done after the lap resin 
is sat in hot water with the channels and trimming complete.  After taking out of the hot water, 
firstly, coat the mirror or lap resin in polishing paste so it doesn't stick.  The mirror is pressed 
onto the lap resin for a sufficient amount of time as to establish full contact between the mirror 
and the lap resin.  Weight can be added.  For hot pressing, it may only take 1 or 2 minutes 
for full contact.  Cold pressing may take 20 minutes or more.  With the coating of polishing 
paste between the mirror and the lap, good contact can be seen through the glass.

note:  even though the lap resin seems quite hard when it is cold, leaving the weight of a pen 
will depress the resin after a length of time, maybe days.

Hot pressing is generally used for freshly channeled and trimmed lap resin since it needs 
the most flattening out.

Cold pressing is done most often after a session or days polishing to ensure good 
contact is continued.

Notes about using the Lap Resin
- Never polish while the lap resin is warm.
- Never let the mirror dry on top of the resin lap since they will stick together and will be 
highly difficult to get apart.  When polishing is finished for the day or session, wrap the 
mirror and tool together in a wet towel or cloth.  Another way is to put a shopping bag 
between the lap resin and mirror.  Make sure the bag is clean from grit contamination first.

If the mirror and resin lap ever do accidently stick together, soak both mirror and resin lap 
in hot water until they are able to slide off each other slowly, under a fair bit of hand 
pressure.  Don't cause any chips in the glass.

Polishing
Now you will have worked your way through the powders finishing with the 1600 and 
the blank will have an even texture surface without any blemishes in the form of scratches, 
stars or sleeks.

In fact the surface is now of a quality that you would expect to reflect light, but in fact it 
cannot.  The surface is very fine but it is not smooth and reflected rays of light are still 
scattered randomly.

The next step is to polish the surface to a reflective surface and the required shape, 
called the "figure".

Polishing can be divided into two segments.

The first to produce a fully polished mirror with a spherical shape and the second to 
parabolise the shape.

Polishing is the most important and exacting part of making the mirror, particularly as 
we are using interference patterns of light rays (more about this later,) to measure 
the accuracy of the mirror.

We will still use a technique known as the Ronchi test to observe the polished area, 
however it is a mistake to try and correct any apparent faults in the mirror until the 
surface is completely polished.

Once the surface is polished out the Ronchi tester will be used to guide the polishing 
action so that a true spherical shape is produced.  During this phase we will learn 
about other undesirable shapes, how to recognise them and how to correct them.

At this stage it would be useful to review the difference between a sphere and a 
parabola.  This can be found on pages 11 and 12 in this book.

After a spherical surface is produced we then enter the final stage, that of parabolising 
the surface, again using the Ronchi tester.

The polish used is cerium oxide, which is an extremely fine white or pink powder not 
unlike rouge in texture, but fortunately not as messy or as difficult to prepare.

The process of polishing is similar to grinding in that the diametrical or narrow "W" 
stroke is used (about 1/4 overhang), the powder is lubricated with water and the 
utmost care is observed to avoid contamination of any kind.

Firstly, a major performance to clean up the work area and put all of the grinding 
materials well away.

If you thought you were fussy with cleanliness when grinding, now become 
obsessive, but not quite neurotic.

Instead of sprinkling the cerium oxide onto the lap and adding water as was done 
for the grinding operation, the cerium oxide is mixed with water first and the mixture 
is put on the blank.  Mix about half a teaspoon of cerium oxide into a half full 35mm 
film container of water and spread this mixture over the blank with a small, fine, 
clean brush.  An art brush is ideal.  A 35mm film container is the right size and 
importantly it has a good seal.

TELESCOPE MIRROR POLISHING

TURNED DOWN EDGE
One of the bigget errors encountered by the telescope mirror maker is the Turned Down Edge 
Usually this is caused by the stroke being too long.  Short strokes with 1/4  to 1/8 overhang 
(that's 2" to 1" overhang on an 8" diameter mirror), will fix this and also many other defects 
in the mirror's shape.

Since the Turned Down Edge defect is such a small area, (just round the outer edge) compared to 
the rest of the mirror, it is hard and time consuming to correct since the rest of the mirror 
now needs to be lowered to the Turned Down Edges level.  A Turned Down Edge cannot be seen with 
the eye since it is very minutely different in shape.  Correction is slow and requires 
short strokes and a hard Resin Lap which is trimmed around the edge to be less diameter than 
the mirror.

Other problems causing the Turned Down Edge are the Lap Resin being to soft or thick.  This 
causes the edge of the mirror to plough into it.

HOLE IN THE MIDDLE
A Central Hole in the middle of the mirror can be corrected by using shorter, narrower strokes.  
A second way is to place Wax Paper, cut out in the shape of a star and the same diameter as 
the hole.  Cold Press the wax paper star until it leaves an indent in the middle of the Lap 
Resin.  The mirror will not rub on this part of the Lap Resin for a while getting rid of the 
hole.

EDGE NOT POLISHING OUT
The mirror's polish process starts in the middle and makes its way to the outside edge.  This 
becomes slower and slower and the very edge seems to take forever compared to the rapid rate of 
polishing the middle.  This of course is because of the area becoming polished getting larger 
and larger.  Somtimes the edge just doesn't want to polish out at all.  If this occurs, try 
turning the mirror upside down with the lap on top and polishing that way for a while.

POLISHING WITH THE LAP ON TOP
If an error just won't dissappear, turning the process upside down with the lap on top will 
usually give results especially if you've reached a stale mate with the mirror on top.

BUILDING:
The size of the diagonal is measured by its width across the mirror (minor axis).
To work out what size Secondary Mirror is needed for the telescope, things need to be worked 
out in order.  Knowing the diameter of your Main Mirror. Firstly, find the focal length of the 
completed mirror.  Secondly, work out the height of your focusing unit.  The focuser needs to 
be wound out about 25mm (1") (roughly where you expect the focus or eyepiece to be) then take 
the height measurement.  Thirdly, the outside diameter of the telescope tube (where the focuser 
will go) needs to be measured and halved.  Having these measurements, the Secondary Mirror size 
can now be worked out.  Add the height of the focuser to the halved outside diameter of the 
telescope tube. This gives the distance from the Secondary Mirror to the eyepiece.

The formula now used is:

Main Mirror diameter divided by Focal length times the distance from the diagonal to the 
eyepiece.

eg. Main Mirror Diameter 200mm (8")
    Focal Length = 1000mm
    Height of Focuser = 70mm
    Outside Diameter of Tube = 230mm divided by 2 (half) = 115mm
    Total distance from Secondary to Eyepiece = 70mm + 115mm = 185mm

Using Formula:

eg. 200mm divided by 1000mm times 185mm = 37mm diameter Secondary Mirror.

BUILDING:
The lower the profile of the Focuser, the smaller the secondary mirror.  Firstly, smaller 
mirrors are cheaper and secondly, they create less obstruction to the main mirror giving 
higher definition (clarity).

BUILDING TIP:
"How do I work out the distances of the optics inside the tube?" Install the Main Mirror Last.
Firstly, work out the Focal Length of the completed mirror. 
Secondly, install the Secondary Mirror and Focuser to the tube. 
Thirdly, work out the distance from the Secondary Mirror to the Eyepiece 
(see Secondary Mirrors below). Fourthly, take the distance of the Secondary Mirror to the 
Eyepiece away from the Focal Length of the Main Mirror.  This figure is the distance the Main 
Mirror should be from the Secondary Mirror. Finally, install the main mirror the correct 
distance from the Secondary Mirror and cut the excess of the tube off.

BUILDING TIP:
Keep the Secondary Mirror covered, once its installed, until the telescope is ready to be used.

BUILDING TIP:
- with the tube standing vertical, Secondary Mirror end up, make a block the correct length so 
that the Main Mirror, connected the Main Mirror Cell, sits in the correct position where it is 
to be attached.  As long as the tube end is square (and the block) the mirror will be attached 
squarely.
- you may want to remove the Main Mirror before cutting the end off so no saw dust etc. goes 
onto the mirror.

BUILDING TIPS:
- To align a finderscope, find an image in the telescope first with fairly high magnification 
  then adjust the Finderscope to match.  Finderscopes are much easier to align in the day time.
- Smaller Finderscopes with a single arm stay in position better when some tape is placed over 
the arm and Finderscope together.



OTHER RESOURCES FOR TELESCOPE MIRROR MAKING

A FASTER WAY TO GRIND MIRRORS

MIRROR MAKING

MORE MIRROR MAKING

MORE MIRROR MAKING

MORE MIRROR MAKING

RONCHI TEST PROGRAM

EXTRA LARGE AND THIN MIRRORS

MORE EXTRA LARGE AND THIN MIRRORS

TELESCOPE MAKING WEB RING

FAQ'S (Frequently asked questions)

HUMUNGUS MIRROR