Celestron 80mm f7.5 ED Refractor
Submitted: Monday, 21st March 2005 by Mark Hodson
This Telescope is a new offering from Celestron in the U.S. and is actually made in China.
Most people are not even aware of its existence as Celestron does not seem to saturate the market with the advertising that other companies do. Celestron does however, market it as a Spotting scope with Astronomical capabilities. This appears strange as the only similarity to a spotting scope is the 1 1/4” erecting diagonal supplied. For all intent and purposes it looks like an Astronomical Telescope.
Celestron does offer a dedicated 80 mm Ed Spotting scope called the Ultima 80 Ed and this does look like a spotting scope.It appears optically to be the competition to the Orion 80mm Ed with the same focal ratio and from those who have seen and compared both, the lenses appears to be the same or same quality. I have seen an Orion but have not compared them side by side.
My main purpose for this scope is as a “Grab and Go” scope.
I will however be using it to piggy back on my Newtonian for wide field CCD photos, as a guide scope and as a finder scope.
Ok so what’s in the box?
Well it is packed the same way as any other Chinese scope, in that, it is pack in a box in a box , but the catch here is it comes packed inside four boxes.
Unpacking it was like getting one of those gag gifts people made by putting a small gift in several layers of boxes and paper , you keep unwrapping until you eventually get down to the gift.
It was however unmarked and well supported considering it has come from China via the States to Sydney and up to Brisbane.
The lens is an 80mm two element with a focal length of 600mm and one lens made of low dispersion (Ed) glass.
This eliminates a lot of the blue or green halo seen around bright objects common in fast achromatic refractors.
Coatings are a very rich green blue and it appears to be some pink thrown in as well on the inner lens.
It comes with a 2” focuser with 1 1/4” adapter and built in T-Adapter.
It has a rack and pinion focuser which is the best Rack and pinion focuser from China I have used. This unit does not have as much rock and roll and side play of standard rack and pinion focusers and although it is not a Crayford focuser, it works well.
The finder scope is a 6x30mm erect image unit on a quick release dove tail and the usual two adjuster screws and one spring tension pin.
The diagonal supplied is an erect image 1 1/4" Amici prism which I will discuss later on.
The tube mounting bracket is also excellent in that it is removable and has a dove tail built in as well as a ¼” thread for photo tripod use.
One problem you will discover when using a 2”diagonal and 2” eyepieces is you can’t get the scope far enough forward in the cradle to balance it properly.
Some form of counter weighting the tube will be required.
Also included is a silver 25mm plossl eyepiece of typical Chinese origins.
With the eyepiece supplied the eye relief is quoted as 20mm and a true field of view of 2.2 degrees and a linear FOV of 114 feet at 1000 yards. Near focus is thirteen feet (14m) and the weight is 4.5lbs (2.05kg).
With a 30mm 80degree AFOV 2” eyepiece you should get 20x @ 4 degrees TFOV.
The lens shade is not of the typical rolled steel or aluminum but heavy cast aluminum.
The lens cover however is too loose and if the scope is pointed to the horizontal, it will fall out.
Now for some preliminary tests to ensure things are pointing where they should be.
Using a laser collimator in the eyepiece holder of the Amici prism diagonal showed that the beam did not exit to centre in the front objective. It was out of centre by 25mm and this showed up in the eyepiece as not being able to find the best focus position at high powers. Things did not seam as sharp as they should when viewing.
First suspect proved to be the culprit and that was the erect image diagonal.
Placing the laser collimator straight into the 2”-11/4”eyepiece adapter by-passed the diagonal and brought the laser smack bang in the centre of the objective.
The focuser appeared to be well aligned.
Now for the Cheshire Collimator to check the objective collimation and this was perfect, to my sigh of relief, as the cell like the Orion, is non adjustable.
I did a bit of modification to the diagonal by taking the back off it and placing a shim between the prism and the side of the inner housing to bring the laser spot to centre. This was an easy task but took about half an hour to complete and several thicknesses of shims tried to get a perfect result.
For the tests however I used a 2” mirror star diagonal which was also checked and adjusted for collimation.
So now with every thing lined up including the finder scope, I mounted the scope onto my EQ 6 for some testing.
A bit of over kill here in the mount, but man is it sturdy.
After a long wait for the “new scope rain” to clear I was eventually able to do some tests on the scope.
My first target was Sirius and it was about 70 degrees up.
After all the rain we have had, the atmosphere was fairly steady for the star test, although the dew eventually got the better of us.
Graeme (Saturn%25) gladly volunteered his time to have a looky in the scope and give his opinion.
No processing on the images was done except to convert the inside and outside focus pictures to grey scale to increase contrast of the rings.
They are a single frame extracted from a ToUcam with filter removed for the inner and outer pictures.
I found with the NIR filter in the camera, outside focus pictures showed the focused star silhouetted on the filter surface.
The rings showed no pinched optics, zones or Astigmatism in optics but just nice round concentric circles. Collimation proved to be excellent.
The star snapped to focus very easily and only the faintest of blue halo could be seen around the star.
Satisfied with the optics we then could not wait to try our first ever look at Comet Machholtz with a 30mm 80 degree eyepiece.
Finding it was easy and only took seconds. Graeme thought I was joking at how quick it was to find and had to see it to believe it. I think it was more luck and the wide FOV offered by the eyepiece, than anything else.
The real test came with a rising Saturn which was by this time only about 40degrees up. This was evident with some turbulence in the view.
However with a 4X Powermate and 12.5mm orthoscopic eyepiece giving 192X Saturn was easy to focus and showed the ring divisions as well as the shadow from the main disc.
This proved a clearer image than I can remember getting with my old 6" f8 achromatic refractor with MV20 filter. This surprised me considering the aperture difference.
Yes it was brighter in the 6” but not as sharp or clear and the false color was always a bother over 180X for me at least.
I would say that with Saturn over head magnification up to 240x would be possible but remember this is only an 80mm scope and 240X is most probably really pushing the limit.
I think that if you’re in the market for a quality colour free small scope, whether for travel or as a main scope but have a limited budget this could be what you need.
As a birding scope or general terrestrial viewing it will excel once you toss the supplied prism diagonal. The following photos were taken with a 2” star diagonal, 40mm kellner eyepiece and a Minolta D7 afocal.
The Celestron has its small problems and I can’t understand why a 2” diagonal was not included instead of the poor quality erect image thing supplied. It is not up to the quality of the optics for day time viewing.
I see that William Optics has a 2” Amici diagonal and this might be a better quality proposition than the supplied unit and would allow the use of 2” wide field eyepieces for terrestrial viewing.
The finder position was a little too far back for Graeme's liking, as he hit his head on it a few times during the night.
You may find it hard to find a price on this scope in Australia at the moment as no one knows much about them. Mine was ordered through Lee Andrews from Andrews Communications and he might prove to be the best local price available. He was the only one willing at the time to order one straight away for me.
They sell here for a similar price to the Orion (approx $900) but have the included accessories mentioned.
All in all I am very happy with my choice.
Comments directed towards the forum are most welcome.Review by Mark Hodson. Discuss this review at the IceInSpace Forums.