Sunday, October 19, 2014

The Galileoscope Revisited - Doing More

The Galileoscope has been with us now for five years. Some in the amateur astronomy community have embraced the small 50mm telescope, while others still view it as an educational tool only, and only a mediocre telescope at best. Personally speaking, I sort of belong to both groups, having found that the telescope has plenty of use, but far from mediocre.
I have used my telescope for a number of projects, and have even extended its use. In that time, I have learned the following.

1. Other eyepieces - Since the Galileoscope uses the standard 1 1/4" diameter, other eyepieces can be used. Caveat: weight. Since the eyepieces are simply a friction fit, it is crucial to limit weight.
2. Diagonals - Not exactly. You can use a diagonal if you use a Barlow ahead of the diagonal. Again, the problem is weight. While I converted a commercial eyepiece by adding a 29mm plano concave lens, this isn't always practical. The Galileoscope could of course be modified by shortening it up, but this is probably more trouble than it is worth. Best avoided.
3. Barlows - Yes. The Galileoscope already comes with a simple Barlow, and other commercial units can be used. In the image, a small inexpensive (and lightweight) Meade 2x Barlow is being used. Again, the biggest problem is weight. 

4. Solar work - Certainly. While I caution users about problems with the projection method, others have reported success. My preferred method is with a solar filter. Baader film is inexpensive, and it is easy to build a solar filter. 
5. Tripod and other mounting systems - The Galileoscope works best as a straight through, traditional telescope. Depending upon what you plan on viewing, you could find yourself being contorted into some extremely odd angles. When it comes to tripods, the taller, the better with the Galileoscope. Using a chair to effectively sit under the telescope is recommended. A tripod will probably be the single most expensive purchase you could make in conjunction with this telescope. Certainly, there are probably other ways you could mount this telescope, depending upon how imaginative the user is.

There are still plenty of projects planned for my Galileoscope. As the top image shows, recently, it was used in alongside my main sunspot telescope, a Monolux 60mm f/7.5 I call "Bianca", and it performed flawlessly. Who knows, I may one day use it for a Messier hunt. As an experimenter's telescope, I believe that it is without peer for its small size.

Monday, October 06, 2014

The Celestron FirstScope Reevaluated

Being an advocate for smaller telescopes is sometimes a daunting task. I am as guilty as others when it comes to the aperture game. When I had larger aperture telescopes at my disposal, the smaller instruments just didn't seem up to the task. It took some retrospect to once more find utility in those smaller telescopes.
My definition of "small" is anything less than 200mm (8 inch) aperture. This means that the great bulk of amateur telescopes falls into that category; professionals have another definition for small, of course. "Smaller" is anything with less than a 152mm (6 inch) aperture. This is the realm of most beginner telescopes, including the nearly ubiquitous 60mm.
60mm has its limitations, of course, and some companies have endeavoured to create beginners telescopes of a larger aperture whilst keeping the price down.
Thus enters the 76mm Celestron FirstScope, and similar Orion FunScope.
My initial assessment of the FirstScope was perhaps a little flattering. It was the first telescope I had purchased new in some time, even if it was a bit  less than $50 USD. It was a design I like; in effect, a tabletop Dobsonian. It was cleverly designed and seemed sturdy enough. I looked forward to putting it to immediate use.
Which is what I did, after a cursory test of the optics. 
The one eyepiece I was certain was going to give me grief on the little telescope was the 4mm SR (which I wrote about not long ago). It was put aside. I did try the 20mm Huygens, and it performed well enough, I thought, but it too was to be put aside. Instead, the FirstScope was used with some of my better Kellners, an 18mm and 20mm. That has been the situation ever since, and I have been quite happy.
But that is not an honest assesment of the telescope out of the box.
After reading a few more reviews for the FirstScope, most of which agreed with my findings, though a couple were particularly critical, I decided it was time to reevaluate the little scope with both of its original eyepieces, and then with some of the least expensive commercial eyepieces available.
I should stress that my FirstScope still lacks a finder. For the low magnification that it is used at, it is easier to look down the tube and use a lower power eyepiece to help locate the target.
However, the first test was with the 4mm (actually 5mm) SR. As expected, poor. It was extremely difficult to focus. Even with an inexpenive Meade 2x Barlow (the kind one finds in their smaller telescopes), "forcing" a longer focal length, it was still difficult, even for an object like the Moon. That eyepiece is best with longer focal length telescopes.
The 20mm H was better (not really that hard, considering), but had distortion near the edges. No surprise again; I've used this eyepiece with my longer focal length refractors and it works better, though still with a narrower field of view. With the 2x Barlow, it performed slightly better, though only slightly.
My next eyepieces are typically found in some of Meade's smaller telescopes, starting with the Meade 17.5mm MA (Modified Achromat). This eyepiece performed far better than expected. The field was much better, though a little distortion persisted again towards the edge. With the Barlow, that distortion was even less. Color was good as well. 
The final eyepiece was a Meade 20mm Kellner. This performed well, though I thought it possessed more edge distortion than the MA. This was alleviated somewhat with the Barlow.

Conclusion - 

What did I learn from this? 
For one, the FirstScope performs better with better eyepieces, bottom line. While Celestron included two eyepieces that would normally be found in their inexpensive 60mm telescopes, they were not suited for this telescope. As some of the others have observed, I could not recommend the accessory kit for the FirstScope as well. The money spent for that would be far better spent on obtaining better eyepieces. The other option would be to buy the almost identical Orion FunScope. According to reviews, it includes a couple of three element eyepieces that are far better performers. Also included in the price is a red dot finder, which is a far better choice for this design. In the end, however, I maintain that this little telescope is a fine performer, as long as its limitations are understood.