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Difference between revisions of "Diving the Cape Peninsula and False Bay/Star Wall"

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(Hazards)
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===Position===
 
===Position===
S34°02.466' E18°18.087' (Shallowest point)
+
*S34°02.466' E018°18.087' (Shallowest point on top of the main outcrop)
 +
*S34°02.426' E018°18,191' (M&M Cave)
  
 
About 200m roughly south west of the offshore rock at Duiker Point.
 
About 200m roughly south west of the offshore rock at Duiker Point.
  
This site is in a Marine Protected Area (2009). A permit is required.  
+
This site is in a Marine Protected Area (2004). A permit is required.  
 
The site is entirely within the Karbonkelberg Restricted Area.
 
The site is entirely within the Karbonkelberg Restricted Area.
  
[[Image:South_east_face_at_Star_Wall_DSC00131.JPG|thumb|The south east face of Star Wall (left of photo)]]
+
[[Image:South_east_face_at_Star_Wall_DSC00131.JPG|thumb|The south east face of Star Wall (left of photo) at about 27m depth]]
 
===Name===
 
===Name===
 
The name "Star Walls" was probably chosen with reference to the adjacent site "Kanobi's Wall", as an allusion to the movie series "Star Wars", and to the vertical granite cliff face that constitutes the main feature of the site. The site was discovered and named by BlueFlash charters in 2006.
 
The name "Star Walls" was probably chosen with reference to the adjacent site "Kanobi's Wall", as an allusion to the movie series "Star Wars", and to the vertical granite cliff face that constitutes the main feature of the site. The site was discovered and named by BlueFlash charters in 2006.
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The north side is more indented and broken up, and slopes down less steeply, to a bottom depth of between 15 and 21m. There are several small caves and swimthroughs in this area, particularly toward the east, and though there is no massive wall, the topography is varied and complex, with large boulders, gullies, crevices and overhangs.  
 
The north side is more indented and broken up, and slopes down less steeply, to a bottom depth of between 15 and 21m. There are several small caves and swimthroughs in this area, particularly toward the east, and though there is no massive wall, the topography is varied and complex, with large boulders, gullies, crevices and overhangs.  
  
'''Reef to the north of the wall outcrop''' — The reef is continuous above 18m to Kanobi's wall to the north, with a number of high pinnacles, some of which are shown on the map.
+
'''Reef to the north of the wall''' — The reef is continuous above 18m to Kanobi's wall to the north, with a number of high pinnacles, some of which are shown on the map.
  
 
On the west side the reef is divided by deep gullies or gaps running from west to east, and eventually continues as far as the east side of Kanobi's reef. This part of the reef is virtually unknown.
 
On the west side the reef is divided by deep gullies or gaps running from west to east, and eventually continues as far as the east side of Kanobi's reef. This part of the reef is virtually unknown.
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The reef to the north of the east wall is an area of deep gullies, high pinnacles, huge boulders, overhangs, holes and occasional swimthroughs.  
 
The reef to the north of the east wall is an area of deep gullies, high pinnacles, huge boulders, overhangs, holes and occasional swimthroughs.  
  
Just north of the east wall, a gully forks and turns west behind the star wall outcrop,and is obstructed by a huge boulder with a hole under it which looks big enough to swim through. This may come out at the east end of the more open gully cutting across the reef from the west. The gully continues north for a moderate distance.
+
Just north of the east wall, a gully forks and turns west behind the Star Wall outcrop, and is obstructed by a huge boulder with a hole under it which looks big enough to swim through. This may come out at the east end of the gully cutting across the reef from the west. The gully continues north for a moderate distance.
 +
 
 +
There is a very high profile area north of the main outcrop, with lots of cracks and high points concentrated in a fairly small area.
  
 
The east branch of the gully opens up as it continues north. Eventually if you remain at 18m you will get to the east side of Kanobi's reef, passing several high pinnacles on the way, and if you go deeper and further east roughly opposite the second pinnacle, you may find the M&M cave, which is slightly deeper.
 
The east branch of the gully opens up as it continues north. Eventually if you remain at 18m you will get to the east side of Kanobi's reef, passing several high pinnacles on the way, and if you go deeper and further east roughly opposite the second pinnacle, you may find the M&M cave, which is slightly deeper.
  
'''M&M Cave''' — Somewhat to the north east of the wall at S34°02.426' E018°18,191' there is a cave swimthrough large enough to turn a scooter inside. The position is shown on the map as M&M cave, which is the initials of the divers who found it and marked its position.  
+
'''M&M Cave''' — Somewhat to the north east of the wall at S34°02.426' E018°18,191' there is a cave swimthrough large enough to turn a scooter inside. The position is shown on the map as M&M cave, which is the initials of the divers who found it and marked its position.  
  
It is very close to the edge of a large sand pach at about 24m depth. The cave is between 22 and 24m deep and has access from several sides. It is under a large flattish boulder propped up agains other large boulders in a small group. The top of the highest of these boulders is probably about 19m deep.
+
It is very close to the edge of a large sand patch at about 24m depth. The cave is between 22 and 24m deep and has access from several sides. It is under a large flattish boulder propped up agains other large boulders in a small group. The top of the highest of these boulders is probably about 19m deep.
  
 
There is a smaller and lower swimthrough which is several metres long a short dittance to the west along the edge of the sand.
 
There is a smaller and lower swimthrough which is several metres long a short dittance to the west along the edge of the sand.
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'''Currents''' — At times there is a slight current along the wall, which has been known to run opposite to the prevailing south easterly wind. Currents may also develop across the wall, over the reef, probably due to local winds, as they are short lived and unpredictable, and progress against the current will be relatively strenuous, but the main strength of the current is usually at the surface and down on the reef it is usually much weaker. It can be quite tricky to pick up divers from the water if the swell picks up during the dive, specially if the wind or current is setting you onto the blinders at Kanobi's reef to the north. A current of approximately 1km/h setting magnetic south has been measured on a day of light south eaterly to easterly wind, and two days later a north setting current of similar strength, also with a south easterly wind.  
 
'''Currents''' — At times there is a slight current along the wall, which has been known to run opposite to the prevailing south easterly wind. Currents may also develop across the wall, over the reef, probably due to local winds, as they are short lived and unpredictable, and progress against the current will be relatively strenuous, but the main strength of the current is usually at the surface and down on the reef it is usually much weaker. It can be quite tricky to pick up divers from the water if the swell picks up during the dive, specially if the wind or current is setting you onto the blinders at Kanobi's reef to the north. A current of approximately 1km/h setting magnetic south has been measured on a day of light south eaterly to easterly wind, and two days later a north setting current of similar strength, also with a south easterly wind.  
  
'''Temperature''' — The water will usually be cold. Temperatures are generally 12°C or less, but have not been recorded lower than 8°C. 14°C would be considered unusually warm. A thermocline of one or two degrees may occur, and this is often associated with a change in visibility.
+
'''Temperature''' — The water will usually be cold. Temperatures are generally 12°C or less, but have not been recorded lower than 8°C. 14°C would be considered unusually warm. A thermocline of one or two degrees may occur, and this is often associated with a change in visibility.
  
 
'''Seasonal variations''' — Conditions suitable for diving this site will be most common in summer, but any time when the south westerly swell is weak and low may be suitable, though visibility may be more unpredictable in winter.  
 
'''Seasonal variations''' — Conditions suitable for diving this site will be most common in summer, but any time when the south westerly swell is weak and low may be suitable, though visibility may be more unpredictable in winter.  
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==Get in==
 
==Get in==
The site can only be accessed by boat. It is about 6.6 km from the slipway at [[Diving the Cape Peninsula and False Bay/Hout Bay harbour|Hout Bay harbour]]. The ride will usually take 10 to 15 minutes, depending on the weather. It there is a strong south easter, the ride back will be relatively wet and bumpy. It is usual to fully dress in your wet or dry suit before leaving the harbour, though gloves and hoods may be left until you reach the site. Completion of kitting up and pre-dive checks are done on site.
+
The site can only be accessed by boat. It is about 6.6 km from the slipway at [[Diving the Cape Peninsula and False Bay/Hout Bay harbour|Hout Bay harbour]]. The ride will usually take 10 to 20 minutes, depending on the weather. It there is a strong south easter, the ride back will be relatively wet and bumpy. It is usual to fully dress in your wet or dry suit before leaving the harbour, though gloves and hoods may be left until you reach the site. Completion of kitting up and pre-dive checks are done on site.
  
 
==See==
 
==See==
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There is a marked difference between the benthic ecology on the more vertical parts of the reef and the flatter areas. The walls and slight overhangs in the 12m to 24m range probably have the most diverse invertebrate cover, and certainly the most colourful. There are large numbers of small gorgonian sea fans, noble corals, soft corals, hydroids, anemones, sponges, colonial ascidians, and bryozoans, providing shelter and food for more mobile invertebrates, The predominant colours are oranges and browns, with splashes of bright blues, yellows, pinks and an occasional touch of green. The depth range from about 15 to 21m is probably the most colorful.  
 
There is a marked difference between the benthic ecology on the more vertical parts of the reef and the flatter areas. The walls and slight overhangs in the 12m to 24m range probably have the most diverse invertebrate cover, and certainly the most colourful. There are large numbers of small gorgonian sea fans, noble corals, soft corals, hydroids, anemones, sponges, colonial ascidians, and bryozoans, providing shelter and food for more mobile invertebrates, The predominant colours are oranges and browns, with splashes of bright blues, yellows, pinks and an occasional touch of green. The depth range from about 15 to 21m is probably the most colorful.  
  
The high parts of the reef tend to be covered by extremely dense cover of the solitary ascidian ''Pyura stolonifera'', commonly known as Red Bait, and much of the flatter surface above 15m has split-fan kelp forest. The deeper flattish surfaces are relatively sparsely covered, with sea cucumbers and sea urchins as the more obvious cover, and a variety of encrusting sponges and coralline algae
+
The high parts of the reef tend to be covered by extremely dense cover of the solitary ascidian ''Pyura stolonifera'', commonly known as Red Bait, and much of the flatter surface above 20m has split-fan kelp forest. The deeper flattish surfaces are relatively sparsely covered, with sea cucumbers and sea urchins as the more obvious cover, and a variety of encrusting sponges and coralline algae
  
 
The Sumo crab which often carries a "hat" of the Green-moon sponge has frequently been seen on the wall.
 
The Sumo crab which often carries a "hat" of the Green-moon sponge has frequently been seen on the wall.

Revision as of 05:46, 24 January 2012

The dive site Star Wall or Star Walls is an offshore rocky reef wall south west of Duiker Point in the Karbonkelberg headland area on the Atlantic seaboard of the Cape Peninsula, near Cape Town in the Western Cape province of South Africa.

Contents

Understand

Map of the dive site at Star Wall

This site was first recorded in March 2006. It is the tallest and longest wall known in the Cape Town area and is a dive site well worth visiting, with a wide range of interesting and colourful invertebrates and spectacular topography, both on the wall itself an on the adjacent reef to the north.


Position

  • S34°02.466' E018°18.087' (Shallowest point on top of the main outcrop)
  • S34°02.426' E018°18,191' (M&M Cave)

About 200m roughly south west of the offshore rock at Duiker Point.

This site is in a Marine Protected Area (2004). A permit is required. The site is entirely within the Karbonkelberg Restricted Area.

The south east face of Star Wall (left of photo) at about 27m depth

Name

The name "Star Walls" was probably chosen with reference to the adjacent site "Kanobi's Wall", as an allusion to the movie series "Star Wars", and to the vertical granite cliff face that constitutes the main feature of the site. The site was discovered and named by BlueFlash charters in 2006.

Depth

Maximum depth at the base of the wall is 32m, and the top of wall is at approximately 8m. The pinnacle on top of the rock is at about 5m.

Most divers would be likely to spend most of the dive at depths between about 24m and 12m, as this is where there is most to see, both in terms of marine life and interesting topographical features, and it is in the relatively surge free zone. An average depth of 18 to 21m would be appropriate for dive planning.

Visibility

Visibility is variable, as with all sites in the region. On a really good day it may exceed 20m, and will then usually be very cold. These conditions normally occur in summer, when upwellings driven by the strong south easterly winds bring cold, clear, deep water to the surface. The good visibility does not often last long, and is usually followed by a plankton bloom soon after the wind dies down. More often the visibility is less than 10m, and it is quite commonly around 5 to 8m in ordinary diving conditions. Of course it can easily be worse, and may be as low as 3 or 4m, even if the conditions otherwise look good. This means that you just have to look closely at the critters, and for this a light is useful.

Topography

Star Wall is a massive and continuous almost vertical granite wall of about 25m height, extending for a length of approximately 100m west to east on the south face of an enormous outcrop, with an extra 50m length of wall on the south-east face. The bottom of the wall is on sand patches amongst large boulders. The rock of the wall is fractured by a number of joints which have weathered to form crevices and small undercuts. These joints are mostly vertical and horizontal, and a few are fairly deeply indented, providing more protected local micro-environments, and which typically are more heavily encrusted with invertebrates.

The reef to the south is relatively low, with a few outcrops extending above 27m, probably none above 24m. There is an outcrop several metres high quite near to the eastern end of the wall.

The western end of the wall makes a sharp turn towards the north, and the top is deeper in this area.

The south wall is the deepest face of a huge outcrop, which is relatively flat on top, sloping from a high point to the east at about 5m depth, down to about 9m at the extreme west.

The top is imnterrupted by a two major cracks. One forms a gully a few metres deep near the east end, wich runs from near the south east corner, to the north side, and the other is roughly parallel and about half way along the top. Both slope down to the north, as does the top in general.

The south east face is also a wall, and is separated from a somewhat lower outcrop further east by a fairly narrow gully with a slightly shallower bottom, which slopes up to the north east, then forks into several gullies.

The north side is more indented and broken up, and slopes down less steeply, to a bottom depth of between 15 and 21m. There are several small caves and swimthroughs in this area, particularly toward the east, and though there is no massive wall, the topography is varied and complex, with large boulders, gullies, crevices and overhangs.

Reef to the north of the wall — The reef is continuous above 18m to Kanobi's wall to the north, with a number of high pinnacles, some of which are shown on the map.

On the west side the reef is divided by deep gullies or gaps running from west to east, and eventually continues as far as the east side of Kanobi's reef. This part of the reef is virtually unknown.

The reef to the north of the east wall is an area of deep gullies, high pinnacles, huge boulders, overhangs, holes and occasional swimthroughs.

Just north of the east wall, a gully forks and turns west behind the Star Wall outcrop, and is obstructed by a huge boulder with a hole under it which looks big enough to swim through. This may come out at the east end of the gully cutting across the reef from the west. The gully continues north for a moderate distance.

There is a very high profile area north of the main outcrop, with lots of cracks and high points concentrated in a fairly small area.

The east branch of the gully opens up as it continues north. Eventually if you remain at 18m you will get to the east side of Kanobi's reef, passing several high pinnacles on the way, and if you go deeper and further east roughly opposite the second pinnacle, you may find the M&M cave, which is slightly deeper.

M&M Cave — Somewhat to the north east of the wall at S34°02.426' E018°18,191' there is a cave swimthrough large enough to turn a scooter inside. The position is shown on the map as M&M cave, which is the initials of the divers who found it and marked its position.

It is very close to the edge of a large sand patch at about 24m depth. The cave is between 22 and 24m deep and has access from several sides. It is under a large flattish boulder propped up agains other large boulders in a small group. The top of the highest of these boulders is probably about 19m deep.

There is a smaller and lower swimthrough which is several metres long a short dittance to the west along the edge of the sand.

The sand patch is quite extensive, and split into several tongues which extend among the boulders in several directions. It is consistently about 24m deep, and bordered mostly by fairly low boulders with low laminaria on top. In some areas the sand and boulders cover the bottom about evenly, in others the perimeter is more clear.

Sunfish Pinnacle — About 300m east of the Star Wall reef there is a pinnacle that comes up very close to the surface, withquite deep water around it. This has been picked up on sonar, but is not known to have been dived.

Geology: Granite of the late Pre-Cambrian Peninsula pluton. Occasional patches of fine white sand

Conditions

Surge — The site is exposed to south westerly swells, which can produce a strong surge over the top of the wall and pinnacles, some of which may break in moderate seas. Surge is usually much weaker in deeper areas, particularly on the face of the wall, which lies across the wave fronts of the prevailing swell.

Currents — At times there is a slight current along the wall, which has been known to run opposite to the prevailing south easterly wind. Currents may also develop across the wall, over the reef, probably due to local winds, as they are short lived and unpredictable, and progress against the current will be relatively strenuous, but the main strength of the current is usually at the surface and down on the reef it is usually much weaker. It can be quite tricky to pick up divers from the water if the swell picks up during the dive, specially if the wind or current is setting you onto the blinders at Kanobi's reef to the north. A current of approximately 1km/h setting magnetic south has been measured on a day of light south eaterly to easterly wind, and two days later a north setting current of similar strength, also with a south easterly wind.

Temperature — The water will usually be cold. Temperatures are generally 12°C or less, but have not been recorded lower than 8°C. 14°C would be considered unusually warm. A thermocline of one or two degrees may occur, and this is often associated with a change in visibility.

Seasonal variations — Conditions suitable for diving this site will be most common in summer, but any time when the south westerly swell is weak and low may be suitable, though visibility may be more unpredictable in winter.

Upwellings and plankton blooms — This is an area which sometimes has upwellings, caused by the south easterly wind, which generally bring in cold, clear, nutrient rich bottom water. This will usually develop a plankton bloom over a day or two of good sunshine, which will reduce shallow water visibility again. This means that the best times to dive are during or directly after an extended period of moderate to strong south easterly winds, and this generally happens in summer. A plankton bloom which reduces surface visibility to 2 to 5m may well only extend down a moderate distance, and the visibility below will usually be better. The depth of the bloom is unpredictable and may range from around 5 or 6m to about 20m. Light levels below the bloom are often drastically reduced, and the colour tends to be very green.

Adverse weather — Moderate to strong winds with a significant westerly component, or large swells or wind waves from the north west to the south west are likely to produce unsafe or unpleasant conditions, and should be avoided.


Get in

The site can only be accessed by boat. It is about 6.6 km from the slipway at Hout Bay harbour. The ride will usually take 10 to 20 minutes, depending on the weather. It there is a strong south easter, the ride back will be relatively wet and bumpy. It is usual to fully dress in your wet or dry suit before leaving the harbour, though gloves and hoods may be left until you reach the site. Completion of kitting up and pre-dive checks are done on site.

See

Marine life

Typical of the big reefs of the Atlantic coast. Heavy growth of red bait and kelp on top. Walls, crevices and overhangs are covered with a large variety of sponges, corals, ascidians and other sessile invertebrates, and a host of small mobile critters, many of them well camouflaged.

There is a marked difference between the benthic ecology on the more vertical parts of the reef and the flatter areas. The walls and slight overhangs in the 12m to 24m range probably have the most diverse invertebrate cover, and certainly the most colourful. There are large numbers of small gorgonian sea fans, noble corals, soft corals, hydroids, anemones, sponges, colonial ascidians, and bryozoans, providing shelter and food for more mobile invertebrates, The predominant colours are oranges and browns, with splashes of bright blues, yellows, pinks and an occasional touch of green. The depth range from about 15 to 21m is probably the most colorful.

The high parts of the reef tend to be covered by extremely dense cover of the solitary ascidian Pyura stolonifera, commonly known as Red Bait, and much of the flatter surface above 20m has split-fan kelp forest. The deeper flattish surfaces are relatively sparsely covered, with sea cucumbers and sea urchins as the more obvious cover, and a variety of encrusting sponges and coralline algae

The Sumo crab which often carries a "hat" of the Green-moon sponge has frequently been seen on the wall.


Features

The longest and highest unbroken wall dive known in the Cape Peninsula. It is about as high as a 7 floor building and longer than a football field. There are a few small cave/swimthroughs to the north of the outcrop, and a larger cave to the north east.


Photography

This is a great site for invertebrate photography. Most of the subjects will be lass than 250mm long, and there may be some much smaller, with a large variety in the 20 to 100mm size range.

If the visibility is good, there may be opportunities for som fairly spectacular scenic shots, with or without divers, and you may be visited by a seal.

Macro and wide-angle equipment are most suitable, and super-macro may also be appropriate. The reef is exceptionally colourful, particularly in the 15 to 25m depth range, where the most of the red and orange light will already have been absorbed by the water, so good artificial illumination is recommended to get the most out of wide angle shots.

Routes

Find out which way the current is running (if any) and drop in on top of the wall. Swim over the edge and descend to the depth of your choice.

  1. If you have not dived the site before, there is plenty to see on the south and east faces of the wall. Start deep and work your way up, inspecting the various zones and working your way along the face with the current. Swim away from the reef before deploying your DSMB at the end of the dive to keep clear of the surge at the top.
  2. A visit to the gulleys to the north of the wall is an interesting alternative. descend to about 18m at the face of the wall, and swim around the reef with the wall to your left. You will pass along the east wall, then turn to the west into a gully with high reef on both sides. The gully opens up to the north, but stay close to the reef to your left at about 18m depth, and you will soon come to a huge boulder with a tunnel under it. You can see through the tunnel, which appears to open slightly deeper on the other side. It is not known at this stage whether it is big enough to swim through. From here you can either go further north up the rest of the gully and then explore the uncharted areas beyond, or cross over or through the tunnel and continue around the back of the wall outcrop.
  3. If you want to try to find the M&M cave, start as for route 2, but instead of taking the left fork, go right and continue due east magnetic until you reach the sand patch, then follow the edge with the reef to your left at about 24m depth until you see a group of large rocks to the left. The cave should be under the large rock closest to the sand. A few metres further along the sand edge is another large rock with a swimthrough under it, and there is reported to be a nice pinnacle near this.

Stay safe

Hazards

The site is in a very exposed area and one should not dive there if there is big swell or strong wind. Skippers beware of the pinnacles as some of them may break unexpectedly if there is swell or a low tide. This is a particular problem when the swells are in "sets", as there may be a long period where the swells are low and well behaved, followed by a few big ones, which can lift and break without much warning, and can be quite stressful if the boat is over the top of the reef at the time.

For this reason it is quite common not to use a shotline. The wall is big and easy to find, and if the swell is marginal it is better to drop off the boat a short distance to the south of the wall to avoid the lumpy seas and strong surge on top. The wall is then found by simply descending to about 15m and swimming north. Ascent in these conditions is also safer if you swim away from the wall to the south before ascending on a DSMB

Other hazards are cold water and strong surge, especially around the pinnacle. Strong offshore winds may develop over a short time in summer, but these are usually forecast.

The currents are not usually a hazard to the diver, but they could drift you to a place where the boat can not safely approach. If this happens, you will just have to wait until you drift to a better place before being picked up. Avoid the exposed rock at Kanobis, where you could be banged around by breaking seas.

Skills

It is possible to restrict oneself to depths above 18m if one's buoyancy control is good, but most boat operators will probably insist on certification for at least 30m, as the main feature of the site is the wall, and divers who are not certified to 30m are not usually good enough at depth monitoring and buyancy control to dive on a wall. This is unfortunately also often the case with divers with more advanced certification, and anyone who is not both competent and confident of their competence at precise buoyancy control should avoid this site, both for their own safety and for the protection of the more fragile reef organisms.

Ability to deploy a DSMB from mid-water is strongly recommended, good buoyancy control is essential.

Equipment

A DSMB is useful if you surface away from the shot line or there is no shot line. It should only be deployed at a distance from the wall were it is unlikely to be dragged over the top by surge or current, which could snag the line and possibly damage the reef biota. Diving with a standard SMB is not recommended unless you have a really good reason and are adequately skilled to avoid entanglement of the line on the top of the wall. This requires constant vigilance, significant line tension, and usually reuires staying a couple of metres away from the wall.

Nitrox can significantly extend your dive time if you are well insulated, and a dry suit is recommended as the water will be cold. If you have a full face mask, it will help on the really cold days, but most divers just allow a few minutes for their face to get used to the cold.

A dive light is worth taking along, as if the surface water is turbid or the lighting is just gloomy due to depth, it may be fairly dark in the deeper areas, and artificial lighting will bring out the bright reds, oranges and yellows of the invertebrates on the face of the wall. A wide angle light beam is best, as it allows close up examination of the organisms while illuminating enough of the surface that you don.t have a tiny hot spot on a generally dim background.

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