Ascension 80ed User manual

PLEASE READ THIS FIRST!

TAKE CARE WHEN HANDLING YOUR

TELESCOPE. TELESCOPES CAN BE LARGE

AND HEAVY AND CAN CAUSE DAMAGE IF

NOT HANDLED CORRECTLY. ALWAYS SEEK

ASSISTANCE IF IN DOUBT.

TO GET THE MOST OUT OF YOUR

EQUIPMENT TAKE THE TIME TO READ

THROUGH THIS MANUAL.

NEVER LOOK AT THE SUN WITHOUT THE

CORRECT EYE PROTECTION. LOOKING AT

OR CLOSE TO THE SUN WITH OR WITHOUT

AN OPTICAL INSTUMENT AND WITHOUT

PROTECTION WILL PERMANENTLY DAMAGE

YOUR EYES. CHILDREN SHOULD ALWAYS

BE SUPERVISED BY A RESPONSIBLE ADULT

WHILE OBSERVING.

Introduction

Congratulations on the purchase of this premium Ascension apochromatic

refractor telescope. Your new Ascension refractor is very well suited for

both astronomical and terrestrial observation. Its Japanese FCD1 triplet

objective lens, solid construction and medium focal ratio make it also ideal

for deep sky imaging. The 80mm Ascension refractor in particular is

extremely well suited as a wide angle imaging instrument, guide scope or

spotting scope.

Please read through the manual to familiarise yourself with your telescope

so that you can get the best use of the equipment. This manual details the

setting up, operation, specification and optional accessories of the

Ascension triplet air-spaced apochromatic refractors.

Parts

Depending on the model the following items are included with the telescope

unless stated otherwise.

Ascension 80mm F6 Refractor

Optical tube assembly with 1:10 Precision focuser and dovetail

2” drawtube with 1.25” adapter.

High quality 2” dielectric diagonal (99%reflectivity)

Two 1.25” wide-angle 70O, high-contrast eyepieces (10mm and 20mm)

High quality telescope and accessories aluminium case

Twenty page printed manual

Interferometer report with HP models (optional with Premium models)

Ascension 80ED triplet refractor

Ascension 102mm F7 Refractor

Optical tube assembly with 1:10 Precision focuser

2” drawtube with 1.25” adapter.

Pair of mounting rings with carry handle and mounting dovetail

High quality 2” dielectric diagonal (99%reflectivity)

Two 1.25” wide-angle 70O, high-contrast eyepieces (10mm and 20mm)

High quality illuminated 8x50mm finder scope with bracket

High quality telescope and accessories aluminium case

Twenty page printed manual

Interferometer report with HP models (optional with Premium models)

Ascension 127mm F7.5 Refractor

Optical tube assembly with 1:10 Precision focuser

2” drawtube with 1.25” adapter.

Pair of mounting rings with carry handle and mounting dovetail

High quality 2” dielectric diagonal (99%reflectivity)

Two 1.25” wide-angle 70O, high-contrast eyepieces (10mm and 20mm)

High quality illuminated 8x50mm finder scope with bracket

High quality telescope and accessories aluminium case

Twenty page printed manual

Interferometer report with HP models (optional with Premium models)

Mounting the Telescope

The telescope can be mounted on a

telescope mount as illustrated in the

picture on the left.

Depending on the weight of your

telescope a light mount will be required

for the 80mm, a medium/heavy mount

will be required for the larger 102mm

and 127mm refractors. When the

102mm and 127mm optical tubes are

used as part of a complete imaging

system a heavy mount is recommended

with a capacity of 18Kg for the 102mm

and 20Kg for the 127mm tube.

A complete imaging system would consist of a main imaging telescope,

guide telescope, cameras and platforms.

Using the Finder-scope

If your telescope includes an Ascension 8x50 finder scope please read this

section to understand how to get the most out of it. The Ascension finder

scope is a high example showing a desirable right way-up image when you

look through it.

Finder-scope Assembly

To adjust the finder-scope you will need to focus the cross-hair as well as

the finder-scope itself.

To focus the crosshair first separate the dioptre-focusing-ring from the

dioptre-locking-ring by holding one firmly and turning the other, loosen them

enough to allow a good adjustment range. Look through the finder-scope

and adjust the dioptre-focusing-ring so that the crosshair looks sharp, finally

tighten the dioptre-locking-ring against the dioptre-focusing-ring.

To focus the finder-scope separate the finder-scope-focusing-ring from the

finder-scope--locking-ring by holding one firmly and turning the other, loosen

them enough to allow a good adjustment range.

crosshair

dioptre

focusing ring

dioptre locking

ring

finder-scope

focusing ring

finder-scope

locking ring

collimating

thumb-screws

bracket

blue/red bracket

support collar

bracket holding

screw

protective

cap

protective

cap

illuminator

Look through the finder-scope and adjust the finder-scope--focusing-ring so

that you can obtain a sharp view, finally tighten the finder-scope-locking-ring

against the finder-scope-focusing-ring.

Finder-scope Illuminator

The Ascension finder-scope uses a red LED

variable illuminator to light up the crosshair.

You can adjust the brightness of the built-in

LED by turning the brightness-adjustment-

knob on top of the illuminator.

Always remember to switch of the illuminator

to save on batteries at the end of a session.

You can switch off the illuminator by turning

the brightness-adjustment-knob clockwise

until the LED goes off, this will be confirmed

by an audible click.

The illuminator requires two 1.5V LR41

batteries to operate. These can be found at

camera shops and electronics suppliers.

Finder-scope Alignment

To assemble the finder-scope first remove the illuminator by unscrewing it

form the finder-scope. Slide the finder-scope in its bracket as shown in the

above picture and gently tighten the three thumb screws to hold it in place,

take care not to over tighten the thumbscrews. Screw the illuminator back in

place.

Make certain that you first tighten collar locking thumbscrew, this is a second

large thumbscrew on the other side of the supporting collar. Mount the

assembled finder-scope to the telescope and secure it in place by tightening

the bracket holding screw collar holding screw. Attach the telescope to a

mount/tripod.

To align the finder-scope please perform steps 1 through 9 as outlined

below, we recommend that the telescope is first aligned during daytime.

Please note that view through the main telescope would appear mirrored

and/or flipped.

LR41 1.5V

brightness

adjustment

knob

1. Attach the finder-scope to the telescope.

2. Mount the telescope to a photographic tripod or astronomical mount.

3. Place a low to medium power (i.e. 20mm) eyepiece in the telescope’s

diagonal. Secure the eyepiece in place.

4. Loosen the movement locks of your mount/tripod, this will allow the

telescope to move freely.

5. Point the telescope to a distant land object (i.e. the top of a lamp post,

tree or chimney). You will notice that the image will appear mirrored

and/or upside down through the telescope, this is normal for an

astronomical telescope. The image will by correctly oriented when

looking through the finder scope.

6. Turn the focuser knob to bring the target in focus and centre the object

in the eyepiece.

7. Re-tighten the tripod/mount movement locks so that the telescope

remains stable during the finder-scope alignment procedure.

8. Look through the finder-scope.

9. Use the three collimating thumbscrews on the finder scope’s bracket to

align the finder scope so that the cross-hair is precisely over the same

object in the eyepiece.

The finder-scope is now aligned to the main telescope. You can check and

refine alignment on a night sky object like a star if required. If you do not

use a diagonal you may need an extension tube to reach focus.

Telescope

view

Finder-scope

view,

aligned

Finder-scope

view,

not aligned

Setting-up your Ascension Refractor

If you are new to observing it is advisable to first use the telescope during

daytime to learn how it operates. First mount the telescope on a tripod or

telescope mount. Once the optical tube has been mounted and has been

balanced attach the finder-scope, then attach a diagonal and low/medium

power eyepiece i.e. 20mm. Make certain that all parts are secure and

remove the lens cap by carefully unscrewing it taking care not to hit the lens

behind the cap.

Now it is a good to extend the telescope’s dew-shield. If your telescope has

a retractable dew-shield pull the dew-shield slowly and away from the

telescope using both hands.

If your telescope has a removable dew-shield un-tighten the two silver

thumb-screws on the periphery of the dew-shield and carefully pull the dew-

shield slowly and away from the telescope using both hands. Reverse the

dew-shield and place it over the front of the telescope. Use the two silver

thumb-screws on the periphery of the dew-shield to secure it in place.

Simply choose a distant target to observe, like a large building or large tree.

Point the telescope towards the target so that it roughly lines up with the

target.

Look through the finder-scope, if you have not aligned it already this is a

good time to do so before you proceed. Move the telescope until the target is

visible in the finder-scope and positioned under the cross-hair.

Once the object is lined up in the finder-scope you will be able to observe

the target through the telescope’s eyepiece. Look through the eyepiece, turn

the focuser knob to bring the target into focus.

Terrestrial Observation

You can use the telescope for terrestrial observation for which you need a

prism diagonal, otherwise the image will appear mirrored and/or upside

down. In astronomy it is not relevant if the Moon is say upside down, what is

important is to capture as much light as possible and image correctors take

some of this valuable light away.

Astronomical Observation

When observing at night your first target should be the Moon as it offers a

wealth of detail, it is large, bright and easy to locate. Spend some time with

the Moon, high magnifications will show a wealth of detail. You will see

mountain ranges, craters and evidence of volcanic activity when the Moon

was mainly composed of molten rock. You will need a neutral density filter to

observe the Moon, a 13% transparency filter is recommended for medium

magnifications, a 25% for high magnifications.

Once confident with the Moon the planets would be the next target. Planets

are easy to identify as they are bright and do not twinkle unlike stars do.

Please note that when a planet is out of focus and it becomes very dim you

may not be able to see it.

Use the finder-scope to place the planet in the centre of the field of view,

then look through the eyepiece and use the telescope focuser to bring the

planet into focus. Planets that are easy to observe include Venus, Mars,

Jupiter and Saturn. You will get the most out of the planets at high

magnifications.

Even at high magnifications planets will look like peas, they will however

reveal lots of detail to the trained eye. Jupiter will show banding and the Red

Spot and you will be able to observe the Galilean Moons.

Saturn is probably the most exciting planet to observe through a telescope.

While surface detail is subtle its rings are a unique sight and you should be

able to observe the Cassini division which appears as a black gap between

the rings.

Mars also known as the Red planet will reveal a good amount of detail when

close to Earth. Its orange colour is prominent and surface markings are

visible as are the Polar caps when present.

Venus can be observed early in the morning before dawn or just after

sunset. Venus appears quite large in the telescope but its atmosphere will

hide any surface detail.

Deep sky observation greatly depends on the prevailing sky conditions. City

lights, low sky transparency and the presence of the Moon will greatly affect

what you can see through the telescope. From a dark site and under

favourable conditions you will be able to see several deep sky objects

including star-clusters, galaxies, nebulae and comets. Such objects with the

exception of stars will appear as feint clouds of matter in monochrome,

human eyes are not able to pickup colour. Cameras on the other hand can

reveal colour and considerable amounts of detail.

Good deep sky objects to look for with a small telescope include the Orion

Nebula, the Trifid nebula, the Ring nebula, the Andromeda Galaxy and a

number of star-clusters among various other objects.

Observation Skills

In general it is easier to locate a target with a low power eyepiece i.e. 25mm.

Once the target has been located centre it in the field of view before

replacing the 25mm eyepiece with a higher power one and so on.

There are many factors that will affect the quality of the image through the

eyepiece; such factors include sky quality in terms of the level or light

pollution, sky transparency and the presence of the Moon if you are

observing deep sky objects like galaxies and nebulae. If you use an

equatorial mount make certain that the telescope has been balanced and

that all screws are reasonably tight.

You will always be limited by the type, size and the optics of your telescope

in what you can see. However there are other important factors to consider

that can substantially improve the experience. Let the optics cool down for

best results, this varies depending on the size and type of the telescope but

typically an 80mm triplet refractor like the 80mm will need around 30 minutes

to properly cool down, the 102mm 60 minutes and the 127mm around 90

minutes. Having said that the telescope will offer reasonably good views at

half the quoted times.

Please keep in mind that targets near the horizon will not look as sharp,

targets near the zenith will look substantially sharper. Avoid setting your

telescope on concrete; wood and grass are better as they do not release

heat. Your line of sight should ideally not pass just over a warm house as the

rising heat will substantially affect the quality of the image.

When conditions are not favourable the maximum useful magnification for

most scopes will be around 25-35 times per inch of aperture. Otherwise high

quality apochromatic refractors like the Ascension ED triplets will offer the

highest magnifications per inch of aperture under favourable conditions to a

maximum of around x100 per inch. Such conditions are rare in the UK.

Dew shields are useful as they cut stray light entering the telescope; they

also protect objective lenses from dew building up on the optics. The

Ascension triplets come with dew –shields that should always be used.

Observing the Sun

Special precautions need to be taken when observing the Sun with a

telescope. A full aperture filter must be used to dramatically reduce the

amount of light that enters the telescope, only use filters designed to be

used for Solar observation with a telescope. A second filter can also be used

at the eyepiece end in conjunction with a full aperture Solar filter to increase

the level of surface detail i.e. Solar Continuum Filters. Such filters work very

well with digital cameras in particular and will reveal additional detail

otherwise not visible to the human eye.

Always check the integrity of any Solar filter before using it with any

telescope. A hair-line scratch on a filter is enough to damage your eyesight.

If in doubt seek professional advice and never point a telescope towards the

Sun without a suitable Solar filter.

Visual Accessories

Depending on what came with your telescope you may need a number of

extra eyepieces which will provide a wider range of magnifications. For

example high magnifications are required for the Moon, planets and

planetary nebulae. Low magnifications are useful for observing extended

objects and for locating targets. Ninety degrees star diagonals are necessary

as they make astronomical observation comfortable. For terrestrial

observation forty-five degrees prism diagonals are preferred, such diagonals

will also offer a corrected view unlike star diagonals.

A Moon filter will be necessary to observe the Moon with almost all

telescopes including the Ascension refractors, light pollution filters can also

help by reducing sky glow and incoming light from other local light sources.

Imaging Accessories

When imaging with a camera attached to the telescope infra-red (IR) block,

nebula (UHC) and narrow-band filters (O3, H-alpha, S2) are recommended

depending on requirements.

For colour imaging an IR block filter will work well to decrease the levels of

background noise and reduce star bloating. Alternatively a UHC photo-visual

filter can be used to block unwanted light wavelengths and effectively act as

a light pollution filter.

When imaging in monochrome Ultra-Violet (UV) and IR

blocked LRGB filters will allow you to create composite

images. In addition narrow-band filters can be used to

create images that remind of the ones captured by the

Hubble telescope. However a lot of experience and time

is required to produce high quality pictures when

imaging in monochrome.

Ascension triplet ED refractors are ideal instruments for wide field deep-sky

imaging due to their high quality apochromatic ED Japanese triplets, solid

structure and Precision Focusers. They are very well suited for deep sky

imaging when coupled with a camera like the Opticstar DS336 XL TEC-

DS-616C XL

cooled camera which supports long exposures in

conjunction with very low noise levels.

The small camera pixels of the DS336 XL closely match

the focal length of the 80mm Ascension refractor to

produce unusually high definition images.

The 80mm Ascension refractor can also be used as a guide scope for auto-

guiding motorised/GOTO telescope mounts in conjunction with an

appropriate guide camera and auto-guide controller. Complete auto-guide

kits include the Opticstar AG-130M CA, AG-131M CA and AG-131C CA.

Such kits consist of a guide-camera, auto-guide controller, cables, adapters

and software to auto-guide with.

The 102mm and 127mm Ascension triplet ED refractors are excellent for

observing at any magnification and make excellent imaging telescopes when

coupled with a high quality camera like the 3.3mp Opticstar DS-336 XL and

especially the large-format 6mp Opticstar DS-616 XL.

The Ascension triplet refractors can be used with the Ascension optical

corrector to produce a flat field of view free of any distortions. The Ascension

corrector has been designed specifically for the Ascension ED triplet

refractors and will also work well with other F6 to F7.5 triplet apochromatic

refractor telescopes.

An adapter may be needed to attach the corrector to a camera, filter-wheel

or other imaging accessory.

OPTICSTAR

DS-616 XL

OPTICSTAR

PL131C CA

C to T-thread

adapter

Ascension corrector

T-thread (M)

2-inch nosepiece

DS-336 XL

APPENDICES

APPENDIX A: Magnification & Field of View

Appendix A outlines the most important aspects of a telescope in terms of its

focal length and focal ratio. These values are important as they dictate

magnification, exposure times when imaging and fields of view.

Practical Magnification

The focal length of a telescope can be calculated by multiplying the focal

ratio of the telescope with its aperture i.e. an f6 refractor with 80mm of

aperture will have a focal length of 480mm (6x80=480).

In a telescope, magnification is the number of times an object appears larger

to the observer when compared to what the observer can see with the naked

eye. There is no real limit to the amount of magnification possible in a

telescope, but practical magnification is limited by the optical system and is

normally around 35-40 times per inch, and up to 100 times per inch of

aperture for very high quality apochromatic refractors.

Maximum useful magnification from a city with most telescopes is around

x35 per inch of aperture, this is due to light pollution, thermal currents and

other environmental factors. Expect much higher magnifications from a dark

site when using the same telescope.

Eyepieces and Magnification

The actual magnification capability of a telescope will vary depending on the

eyepiece attached to the telescope. Magnification can be changed by simply

exchanging eyepieces.

Magnification depends on two factors. The focal length of the telescope and

the focal length of the eyepiece used. To calculate the magnifying power an

eyepiece gives, simply divide the focal length of the eyepiece into the focal

length of the telescope.

Magnification = telescope’s focal length / eyepiece’s focal length = F/f

For example a telescope with a focal length of 480mm and an eyepiece with

a focal length of 5mm will magnify its target 100 times (480/5=96).

FOCUSER

FOCUSER DRAWTUBE

OBJECTIVE LENS

EYEPIECE

INCOMING LIGHT

Barlow lenses can be employed with an eyepiece to increase magnification.

To calculate the magnifying power of an eyepiece in conjunction with a

Barlow lens, divide the focal length of the eyepiece into the focal length of

the telescope and multiply the result by the Barlow’s magnifying power.

Magnification = telescope’s focal length / eyepiece’s focal length x Barlow power

For example a telescope with a focal length of 1000mm used with an 10mm

eyepiece and x2 Barlow will offer a magnification of x200 (1000/10x2=200).

Focal Ratio

The focal ratio represents the speed of the telescope’s optics; the focal ratio

can be calculated by dividing the focal length by the telescope’s aperture.

Telescopes with faster/shorter focal ratios like the Ascension 80mm F6 ED

triplet benefit from wider fields of view, and a subsequent increase in

brightness and image resolution. Fast f/4 focal ratios are generally best for

lower power wide field observing and deep space imaging. On the other

hand slow f/10 focal ratios and above are better suited to higher power lunar

and planetary observation as well as high magnification imaging in general.

For example when imaging extended deep sky objects like nebulae and

galaxies an f/4 telescope will capture four times the mount of light in the

same time period when compared to a telescope with an f/8 focal ratio. The

same does not apply to single point light sources like stars where aperture

alone dictates what you can see.

Field Of View

The field of view is the portion of the sky that is visible through the telescope

and depends on the focal ratio of the telescope and eyepiece used. In

general higher magnifications result in smaller fields of view.

Short focal ratios (f/4) with wide fields of view greatly favour deep sky

viewing and imaging, where focal ratios of f/10 and above are better suited

for planetary and Lunar observation. Focal ratios in between these values

(f6) may be considered appropriate for general use. It is possible to calculate

the field of view of a telescope given a certain eyepiece using the following

formula.

where Magnification = Telescope Focal Length / Eyepiece Focal Length

Consider a telescope with a focal length of 500mm and a 40mm eyepiece

with a 70 degrees Apparent Field of View.

Magnification = 500/40 = 12.5 ~ Actual Field of View = 70/12.5 = 5.6 degrees

APPENDIX B: Optics

Optics Care

Lenses and corrector plates can be treated as

camera lenses for cleaning purposes. What

makes them difficult to clean is the large size of

such optical elements.

The general rule is not to touch the optics and

only clean them when absolutely necessary; dust

on the objective lens could be removed with very

gentle strokes of a camel hair brush available at

camera shops.

Another way to remove dust from an optical surface is with compressed

photographic air which is free of contaminants. Be careful and always make

certain that the nozzle is propellant free. Hold the compressed air-can the

right way up as otherwise they can discharge liquid propellant which will

stain the optics. Stains on optics can be removed with optical cleaners used

to clean photographic lenses. Always use compressed air at very low

pressure as contaminants that may have landed on the lens could scratch

the glass surface, never rush the cleaning process.

Condensation

When temperature drops rapidly condensation may form on the objective

lens of the telescope. This happens over time and its effects become

noticeable as condensation builds up and the target becomes dimmer and

appears as if it is out of focus.

Condensation can be removed from the optics with a hair-dryer set to ‘cold’.

Otherwise bring the telescope inside and let condensation to dissipate

before putting on the cover. Place the telescope on a table and not on the

floor where most of the dust can be found. Never try to remove condensation

using a cleaning cloth or similar, this will most likely smear the optics.

APPENDIX C: The Focuser

Focuser Adjustment

The Ascension comes with a 1:10 dual-speed focuser

that has been adjusted at the factory. In certain cases it

may be necessary to regulate the tension to improve

performance by adjusting the two silver thumb-screws

below the focuser. This may be required if the focuser

was adjusted at room temperature and then used in sub-

zero temperatures.

Also as the focuser is worked-in over time surfaces smoothen out and the

focuser may need slight re-adjusting. When done for the first time this

procedure requires patience and time.

We recommend only adjusting the focuser beyond simply re-adjusting the

two silver thumb-screws, as outlined below, if there was a real need. The

focuser has been designed to be fine-tuned externally by the user.

It is also possible to re-adjust the

internal clutch of the focuser

mechanism to regulate the tension

on the focuser drawtube for which

the clutch will need to be removed

for the adjustment to take place.

Please keep in mind that this is a

rather difficult procedure to

perform without experience and

the right set of tools.

To set the tension on the focuser drawtube follow the instructions below:

1. Remove all accessories from the telescope drawtube

2. Tilt the telescope to say 60 degrees and pointing to the sky

3. Loosen thumbscrew A

4. Loosen thumbscrew B

5. Tighten/adjust thumbscrew Bin very small increments till you obtain

the preferred focus tension

6. Attach a heavy accessory to the focuser like a 2-inch diagonal and

eyepiece.

7. Go to step 4and repeat the process until the tension is right.

8. Lightly tighten thumbscrew A until it comes in contact with the

The above procedure should resolve any focuser adjustment issues. Once

the correct tension has been set thumbscrew A can then be used to lock the

focuser in place as and when required.

The tension can be regulated further by adjusting the two sets of three

screws D1, D2 and D3. This is however needs a lot practice and experience

to get right.

To set the tension on the focuser drawtube follow the instructions below:

1. Loosen thumbscrews Aand B

2. Use a hex key to loosen the two larger

centre locking screws D1 on the top of

the focuser on either side

3. Adjust the two pairs of screws D2 and D3

on either side of the focuser in very small

increments until you obtain the preferred

focus knob tension

4. Use a hex key to tighten the two locking

screws D1

5. Screw Bback into place and adjust until

you obtain the desired tension on the

focuser’s drawtube as described earlier in

this document.

Acan then be used to lock the focuser in place as and when required.

Note that if you over tighten the screw pairs D2 and D3 the drawtube will

‘stick’, if the screws are too loose the drawtube will not hold in place.

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