What is an aperture mask for a telescope

Posted on June 25, 2021 by Reviewer

Often integrated into a telescope lens / OTA cover, an aperture mask reduced the effective diameter of the main objective lens or mirror. Although you lose resolution, you also reduced the effects of atmospheric turbulence under bad seeing conditions. Also reduced brightness of the full Moon, which will be very bright and dazzling through a large telescope. If your telescope cover does not have a built in aperture mask, they are easy to make out of cardboard.

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Celestron astromaster 102 AZ review

Posted on June 25, 2021 by Reviewer

The Celestron astromaster 102AZ is a great example of a telescope that proves high magnification and large aperture are not an essential requirement when starting out in astronomy. If you are starting out, the simple AZ mount and straight though optics (refractor as apposed to a Newtonian reflector ) make for easy set up in minutes with no polar alignment and balancing the OTA with counter weights. On top of this, the erect image diagonal with left / right orientation with a combination or a wide field of view (20mm eyepiece) makes finding objects in the night sky easy. Finder scope is a standard red dot finder.

Do not think this is a telescope for astronomy only. It is ideal for terrestrial use, including looking at ships at sea, views over distant landscapes, but also with a close focus of around 8 metres can also be used for looking at birds in the back garden. For the DSLR / mirrorless camera users, there is a built in t-ring for prime focus photography.

The short tube 660mm f6.6 102mm lens gives very good contrast, considering it is fully coated optics. Chromatic aberration is visible on high contrast subjects. But a simple upgrade to multi-coated plossl eyepieces will help reduce this. Eyepieces included are modified achromatics of 10mm and 20mm, which give 33x and 66x. These magnifications are perfect for finding you way around the night sky, and from dark sky locations will reveal many of the brighter galaxies and nebula. This scope will also make the colours of stars more vivid.

The focus is very smooth to use, and adds to the ease of use. On the subject of the focuser, it has a a built in 1.25″ adapter. This can be removed to accept 2″ diagonals for a picture window FOV. But note that a diagonal 2″ mirror will not get infinity focus. So you will need to get a mirror version.

No point in a getting a telescope with an insufficient mount. No worries here, as a combination of a good quality aluminium AZ tripod and short tube OTA makes it very steay.

Over all a nice starter package to get you started in astronomy, with the added benefit of being a great choice for terrestrial use.

Available to purchase HERE

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Hawke Endurance ED 8×25 monocular review

Posted on June 10, 2021 by Reviewer

The Hawke Endurance 8×25 ED monocular is an ultra compact solution, weighing only 150g. Ideal for keeping in a pocket or hanging from your wrist with the strap included. Can also be attached to a belt , using the soft nylon case included. Other features and a twist eye cup and lens caps , which has a stay on , drop down objective cover.

So what about the optics. You get fully mulit-coated ED glass with phase corrected BAk-4 prisms. End result is big optics performance from a compact monocular. The image is very sharp for around 80% from centre, where it gets a little softer (and I mean a little) towards the edge. Unless you know what you are looking for, chromatic aberration is hardly evident. Looking into heavily back lit branches in trees show virtually no colour fringing. Another plus point is the total lack of internal reflection.

Field of view is 119m @ 1000m with an AFOV of 54 degrees. Eye cup is twist type with 13mm eye relief. The focus wheel is small, but turns easily. Close focus is 5m and is fully nitrogen waterproof.

All in all and cracking little monocular that will be a great take anywhere solution.

Plus points – Very bright image with extremely low levels of CA

Minus points – 5m close focus and short eye relief

Available to purchase from Northern Optics

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Sigma 21-35mm f3.5 – 4.2 first impressions, with sample images

Posted on February 15, 2021 by Reviewer

Bought an early 80s Sigma 21-35mm f3.5 – 4.2 from a vintage lens shop for the princely sum of just £39 + postage. On top of this I needed to get an OM to EOS adapter so I could use it on my 1100D (apologies to film camera users).

This particular lens was priced so low because it was described as having a sticky zoom and focus. But as the optics seemed OK (on the images) I went for it. So when it arrived, the first thing I noticed was the build quality. Compared to my stock EOS 18-55mm stock lens, the sigma felt and looked in a different league. It felt so solid, and weighty for such a compact lens. But I saw this as a good thing. From an optics sellers myself, I never say heavy. I say well built.

Visually, the optics were externally and internally free of dust and fungus. This from a 40ish year old lens. Boy that front lens element looks impressive. Will need to get a 77mm UV filter at some point. When when out on walks and cycle rides, the lens cap goes on in between all photos. The lens hood remains permanently in place.

This is one of those rare wide angle zooms with a push pull zoom action. So the description said the zoom action and focus is stiff. I found the focus fine, and smooth with no tight points. But yes, the zoom action is VERY stiff. But no problem, as there is no rush with landscape photography while you slowly get to the desired focal length.

So what about image quality. At first I found focus quite tricky getting right. First photos, despite looking through the camera where anything but sharp. But then it all fell into place when I went out and about to do some landscapes. I quickly realized that using at 21mm f8 , you simply turn the focus to infinity until it turns no more. Then take the photo, to find the incredible depth of field makes every thing pin sharp from around 6ft to infinity. Problem solved. As I will be taking most images at 21mm f8, there is no need to worry about focus. Simply point and shoot. BTW when I say move the focus to infinity, I mean I am guessing its infinity, because the focus and DOF scales have worn out. I personally found minus one stop exposure compensation is needed for correct exposure.

On the subject of aperture. From 3.5- 4.2 there is 3 clicks, with then half stops from there on in up to f22 . The aperture adjustment, just like the zoom is a little stiff to use with this example. But I`m in no hurry, so its not a problem So am impressed with my little Sigma. 100% yes . Below is the lens itself, together with a couple of images. The landscape is set on infinity 21mm f8 , where the astro image was around f5.6 for 15 seconds. Just a little coma smearing in the corners, but not obvious unless you zoom in. Once I have had this lens a while longer, I may give a more long term review, and no doubt share any tips , plus and minus points I have picked up along the way.

Sigma 21-35mm f3.5 – 4.2
21mm f8 400 ISO . Check that depth of field
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Hawke Endurance ED 12×50 binoculars. Blog post 2nd Aug 2020

Posted on August 4, 2020 by Reviewer

A customer came to the Northern optics Optics weekend looking for a set of good quality binoculars for birdwatching. Knowing the reserve they visit, I was aware that they needed a little extra magnification without reducing image quality.

After try 8x and 10x options, they tried the Hawke Endurance ED 12×50 binoculars. There was an instant WOW reponse from the buyer, who had no hesitation in purchasing. The clear view with reduced chromatic aberration ticked two very large boxes.

With a field of view at 105m @ 1000m , plus a 60 degree apparent field, these give a very comfortable and wide view for such a high magnification set. The new 2020 design not only looks the part, but are very easy to hand hold despite weighing just over 800g.

Focusing is very easy , with a better than expected 2.5m close focus. This means they are not just for ling distance observations.

FMC optics with ED glass and silver coated BaK-4 prisms, together with larger 50mm objective lenses give excellent brightness with minimal chromatic aberrationn. Click HERE to buy

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Hawke Endurance ED 12×50 binoculars. 2020 update

Posted on June 26, 2020 by Reviewer
Hawke Endurance ED 12×50 binoculars

The Hawke Endurance ED 12×50 binoculars have made a come back in 2020, featuring a brand new body design and look. Available in black or green , with a textured rubber finish for easy handling. Despite weighing 805g, I found them very easy to hand hold. On paper 5.2 degree FOV may seem narrow. But with a generous apparent field, the view seems wider than expected when you look through the eyepieces.

ED stands for low dispersion glass. This helps reduce the effects of colour fringing , but not fully eliminating chromatic aberration, with just a little showing around high contrast subjects. With an exit pupil of just over 4mm and 50mm objective lenses, the image is very bright with punchy contrast. A little fall off towards the edges, but well within tolerances.

Overall build quality is excellent. This extends to the solid but comfortable twist eye cups. With eye relief of 15mm, they may not suit all spectacle wearers, so best try a set if in doubt. The focus wheel is a little stiffer than some, but not an issue. Close focus is very good for a set with 12x power.

Accessories include a semi soft case, padded strap and lens covers. Warranty is the now standard but excellent life time offering.

12×50 is a great choice for looking at distant wildlife, ships at sea and plane spotting, where a wide field of view is not at the top of the list. But make no mistake, they are just as capable looking at wild life in the back garden or when out on bird watching walks.

Click HERE to buy

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Hilkinson 8×25 monocular review

Posted on February 13, 2020 by Reviewer
The Ultra compact Hilkinson WP 8×25 monocular

Entry level 8×25 monocular from Hilkinson. Being only 131g and 110mm long , they are perfect for wildlife watching on the go. So lets take a closer look.

The monocular comes in a plain box show the brand name and bar code. Inside we find a very basic nylon soft case with belt loop and a useful leaftet showing how to care for the product and a simple to understand glossary.

Taking the monocular out the case, the wrist strap is already attached. The monocular itself feels very solid and has a rubber covering with finger grips. Looking at the controls, the focus moves very smooth with no tight spots. Unlike some with an internal focus, this one extends outwards from the body as you focus closer. One minor potential issue with this, is that dust may gather on the extended section and risk penetration. But keep dust at bay with a dust blower after use, and this should not be a problem.

The eye cup is twist type. It only quotes as 13mm eye relief, but I found I could easily get full field of view with spectacles on. One thing to note, that with the focus and eye cup twisted out, the monocular will be too long to fit back in the case. So simply return the focus to the start position and it will fit.

At 105 m @ 1000m (6 degrees), it may not be as wide angle as some 8×25 monoculars (The Helios nitrosport for example) . But what you do get is better eye relief and a much flatter field. Edge of field sharpness is outstanding for optics in this price range, with very low levels of barrel distortion. So what you lose in FOV, you gain with the extra eye relief and image sharpness.

Colours and contrast are very good for optics in this price range, with chromatic aberration well within tollerences. Lastly a great feature of the Hilkinson 8×25 monocular is the close focus. On the body it shows as 1.6 metres. Elsewhere I see quotes of under 2m and 1.2m. On testing I actually found I could focus down to 1.1m. This is perfect if you like looking at Butterflies and Bees etc without disturbing them.

Now discontinued

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Viking traveller 8×21 binoculars review

Posted on February 7, 2020 by Reviewer
Viking Traveller 8×21 binoculars

The Viking traveller compact binoculars are aimed at the beginner. So lets have a look to see how the build quality and optics perform for such a low price (around £25 – £30 at the time of this review)

First thing you will notice is the plain outer box, showing minimal info such as the logo, name of binoculars , bar code and address of the importer. No tech spec or image is shown.

Opening the box, you are greated with a basic nylon strap and soft case. No surprises here considering the price. The case also has a handy belt loop.

When you take the binoculars out, the first thing you notice is how solid they feel. The slightly textured feel is better than many in this price range. They are a compact double hinged body which stays nicely in place once the IPD is set. A nice feature on a sub £30 set is the twist eye cups. They feel well built and operate smoothly. Does not seem to be much in the way of 2-3 clicks, just in or out. On the subject of eye cups, the eye relief is quoted as 17mm, which in theory should be enough for spectacle wearers. Sadly with the eye cup in a down position I could not get the full field of view with glasses on. But saying that, people wear different types of spectacles, so may differ from one user to the next. Lastly with regards handling, the focus wheel is a little small, so may be tricky to use with large gloves on. But small focus wheels are on most compacts. That`s just the nature of the beast. The right eye dioptre adjustment is very easy to use and smooth in operation.

So to finish things off lets have a look at the optics. These are Bk7 prisms and fully coated optics. So do not expect the same cutting edge sharpness of a £100 set. But what you do get is a clear view considering the price. Compared to some budget binoculars I have tested, there is very little fall off in sharpness towards the edge. Also there is very little evidence of chromatic aberration in the centre, with hardly any purple colour fringing when looking at back lit branches.

Summing up. Very good optics for the price with low levels of CA and better than expected build quality. Slight minus point, the short eye relief for (some) spectacle wearers and the small focus wheel. Very good value for money.

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North Lincs Astro meeting 3rd February 2020

Posted on February 4, 2020 by Reviewer
Will Man ever walk on the Planet Mars ?

We had a great turn out, including a new face , to watch John Dunthorne give an excellent talk at the February 2020 North Lincs astro society meeting. His talk entitled The challenge of transporting Man to Mars.

This was a well presented talk, lasting over an hour, with some excellent facts and figures, backed up with some stunning images and videos. Who would have thought there were so many barriers to clear, from the effects of radiation, to handling isolation and the mind blowing $$$s needed to fund such a project.

Skies were clear. But the blustery conditions made using the telescope a difficult task. But we got some delightfull views of the Moon.

Thank you as always to Malcolm and Glenys for the refreshments , and the Lincolnshire wild life trust for the use of the venue.

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Olivon PC-3 8×34 binoculars. Blog post December 2019

Posted on December 31, 2019 by Reviewer
Olivon PC-3 8×34 binoculars

A customer visited the Northern Optics Optics weekend looking for a good quality set of binoculars. And I would imagine they would also need to be lightweight for travels on his bike.

He looked at a couple of 42mm models in 10x and 8x magnification. But when he tried the Olivon PC-3 8×34 binoculars, they were an instant hit. The customer mentioned they gave a brighter and sharper view than the 2 larger sets tested. Just to prove quality can outperform size when it comes to optics.

The buyer liked the lightweight body , long eye relief (for use with cycling glasses) and the handling. Phase coated BaK-4 prisms and FMC optics give excellent contrast and colours, with an acceptable level of chromatic aberration.

I also pointed out the size (width) of the eyepieces, which I would say are wider than the average in this class. This makes them very user friendly. The Olivon PC3 8×34 come with a soft carry case with strap, and a high quality padded neck strap.

They have one of the smoothest focus wheels in binoculars in this price range.

Available to purchase from Northern Optics

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