Celestron FirstScope Test Accessories

FirstScope Project: Test Accessories

Finally this is what we are all waiting for! Project Test, More Eyepieces, Focal Reducer, Barlow Lens, Focus Test, RFT Results

First, for our main tests we used the 10mm 62 degree Aspheric eyepiece from Svbony, which is the best performer in the Celestron FirstScope. The Celestron is an RFT with a focal length of only 12-inches and a defective secondary mirror. Nevertheless, the small Moon appears extremely bright.

In keeping right on budget, none of the accessories exceeded $14 in cost.

The big problem encountered was the handheld iphone could not adjust for all the light coming through the eyepiece. A Moon filter could not reduce the light in any significant amount and was set aside. Next I tried a polarizing filter. Still the moonlight was far too intense. Finally the tests were shot with the overexposed Moon. The first image shows the Moon image scale through the 10mm 62 degree Aspheric eyepiece.

The next image shows the Moon with the same eyepiece and an attached Svbony .5x focal reducer screwed to the bottom of the eyepiece.

In the third image, the eyepiece and a 2x Svbony Barlow were used. The Barlow screws to the bottom of the eyepiece. The change in image size is apparent.

Next, a 32mm and 40mm focus Plossls were test and they did not do well with the scope. The Moon had the image of the mirror and eyepiece superimposed over it. These fast eyepieces just don't work in this telescope. The final photo shows another type of obstruction defect that occurs, blocking out most of the Moon.

In all tests, the full uncropped size of the iPhone camera is retained.

Finally a really big problem surfaced. Due to the fast f3.9 focal ratio of the mirror, and perhaps inclusive of the subpar optical system, the focus could not be achieved over the entire region of the Moon. Thus focus had to be interpolated and approximated. Even a Bahtinov mask could not help this probem.

In conclusion, aside from the inherent problems with the Celestron FirstScope:

* Aspheric eyepieces with medium focal lengths do well with the f3.9 system
* Images are small and bright
* The focal reducer is working well
* The 2x Barlow is working well
* The telescope produces Moon images that are too bright for iPhone imaging
* The scope may have its place with deep sky objects

All experimental project Moon images were shot on the night of Friday, September 4th, 2020.

Celestron FirstScope - Index
https://otisastro.blogspot.com/2020/08/celestron-firstscope-index.html