Barride Optics achromatic objective in cell D=210 mm f=1800 mm

Achromatic objective in mount for do-it-yourself refractor telescope construction

Making your own astronomical telescope is exciting. You can build a telescope according to your own ideas, a unique specimen, which exists only once. This objective allows the construction of an achromatic refractor.

The dimensions of the cell can be taken from a drawing, which is available as a PDF:
achromatic-lens-d210-drawing.pdf

DIY project with this objective

A customer has built an impressive refractor with this objective and posted a video about some of the construction phases and some of the results on YouTube, the link can be found here.

Customer´s Test Report

Our customer Andreas Daus treated his old refractor to a new objective lens and wrote down both conversion and testing:

"Testimonial
Barride Optics 210/1800 refractor objective

About 12 years ago I built an 8" refractor together with my father, which now after all these years should get a new optics.
For a long time I was looking for a suitable objective lens and with the help of Teleskop Service I found it at Barride Optics in China.
Ordered was a 210/1800 F/9 objective in mount, delivery time about 3 months.


On 04/26/22 a super packed product was delivered to me:
Inside the large box was a second box and inside that was the objective, which was very well protected by huge amounts of bubble wrap, foam wrap, etc.
The objective lens is well made and makes a robust impression.
The first thing I noticed compared to my old objective was the blackened lens edges.


Also, a good and sturdy aluminum lens mount. The lenses themselves are clear and free of dirt or other contaminants, and have a slightly greenish coating


Now for the installation:
This is relatively quickly made. There are three holes each for M5 tension and compression screws.


I first put the objective flat on the tube flange and screwed it tight, to find out afterwards that (due to the precise construction of the tube) no adjustment was necessary.

The First Light:
At new moon on the Großer Feldberg in the Taunus.
Already at the alignment a great optics was to be guessed at the star Arcture, which was visible as a beautiful pinpoint star without deformations or tails. Only a slight blue fringe - but I remind again, it is and remains an achromat.
After everything was set up, I used the time until complete darkness to cool down the telescope.

As first object I then headed for h+x in Perseus.
The result, together with a TS 38mm 70° eyepiece, was simply incredible: very fine stars, the likes of which I had never seen in my reflectors. It felt like floating in space.

Next I went east to M13:
Observed with a 13mm Baader Hyperion like little diamonds on a black background - clear, distinct, and clearly resolved all the way to the center. Simply a pleasure.

At the end of the first light I wanted to determine the intensity of the chromatic aberration and turned to Vega: As expected a blue-violet halo around the star, but less than I had feared. The intensity of the blue fringe is hard to describe, because it is a very subjective impression. I don´t mind the small chromatic aberration of the 210/1800 F/9 - I have seen much worse. More important to me is that Vega can be seen as a clean, pinpoint dot of light that shows no tail, bulges, or other defects that could be attributed to an optical problem.

Conclusion:
I am impressed and this objective lens has exceeded my expectations.
It is truly recommended from both a mechanical and optical quality standpoint. Good workmanship and a clean image intra- and extrafocally - all within the scope of an achromat, of course. Of a very good achromat!

Thanks to Wolfgang Ransburg and his team for doing everything they could to get me this great objective lens. An excellent service - as always!

Your Andreas Daus"