Monday, January 24, 2011

I love tinkering.....with my uber portable Celestron 76mm Firstscope dobbie



There is only one other thing other than observing DSO's under a dark pristine skies that get my adrenaline pumping and that is trying out a new scope for the first time. Since moving to my second storey dwelling in the UCLA university apartments in Los Angeles, I have been trying to find the perfect "grab and go" scope. There are many perfect "grab and go" scopes out there, and probably the best by far is the Orion StarBlast 4.5" f/4. But the asking price of $199 (not including taxes and postage) was a bit much seeing how many scopes I currently have in my menagerie. Its old price of $149 was in my opinion a much better price point than the current price Orion sells it for seeing that it is primarily a rich field telescope (RFT). The views of planets were only eh! I considered the Orion SkyScanner 100mm f/4 (and I am not ruling out that one seeing that it has a parabolic mirror and it is only 2 lbs heavier than the Celestron Firstscope IYA), but in the end I  got the Celestron Firstscope 76mm f/3 instead. I just could not pass it up for the price. Brand new the scope can now be had for as low as about $35-$40USD with postage from Amazon. That is a pretty crazy price seeing that in the past you could not even get an eyepiece for the price! As usual I went the used route and got the Firstscope and the accessory kit (two extra eyepieces and a dinky lil plastic 5x20 finder, minus the Celestron carry bag...no biggie) for $40USD plus postage off e bay. So what are my thoughts on this uber portable and small scope...well read on!!!!



Well the scope, mini dob mount, 4 eyepieces, 5x20 finder and software arrived in a brown box, which I had to pick up from my local USPS office. Seeing that it was used, it did not come with the original box. Firstly when I picked the box up at my local USPS office, I was struck by how light the whole thing was, being used to my light but not overly light 13 lb StarBlast. This weighs next to nothing (and I am sure this will follow me on my many travels abroad in the future). Well the OTA and mount, which comes pre-assembled out of the box only weights 4 lbs (about 1.8 kgs!), as opposed to StarBlast 5.9 kg...still light in any case but not nearly super portable as it will NOT fit in an overhead luggage compartment on an aircraft. Also when turned down, the OTA does not occupy that much space on the mount, seeing that it is probably only slightly taller than 12 inches. If you look at the piccy's, the scope is about the same height as my 20x80's ;) Cool or what......plus weight wise it is really comparable to the binocs too. But I guess in the end its the viewing which count. The scope can be cheap, light and small, but if it has a lemon for a mirror then it means nothing. So how does this cute lil scope perform? Well read on and find out. I have even had it go mano el mano with my Celestron Cometron CO60 refractor. Testing was performed over several nights to take into account seeing conditions.



Well the scope performed...drumroll....rather well for a scope with a very short focal length spherical mirror. I was half expecting the images to be crap and the collimation to be out whack as I used to own a dog of a scope...one of them barlow in the focuser ones with a spherical mirror. Now don't get me wrong this scope is still a wide field RFT and it was never meant to be used as a high powered instrument for planetary and moon gazing (Heck even my old Orion StarBlast did not fare too well in the high power department and views broke down over 100x magnification) . But if you keep within reasonable limits, the scope performs remarkably well. Putting the scope side by side with the CO60 refractor for instance, the refractor clearly trounced the Firstscope in this respect. The views or the moon and Jupiter were way contrastier and showed more detail at magnifications over 100x. In fact I did not like using the scope for magnifications over 100x. My personal opinion...views of the moon and planet was the best at 50x with spherical aberration blurring the views about 100x mag. Now stars were also not as tight as the refractor, and the Firstscope had some real issues when the objects were not in the centre of the field of view. Well I was using my SWA eyepieces so I guess that was the problem too with its super wide field views.


Now for the part where the Firstscope performs way better than the CO60...well of course deep sky. 76mm is 76mm and it collects much more light than a mere 60mm. DSO's all look way better in the Firstscope than in the CO60. Well the CO60 gave more pleasing views as the background was much darker, partly due to the increase contrast, but more so due to its smaller aperture. M42, the Orion Nebula looked remarkable. Best combo for the scope is my 20mm Expanse and the Orion Shorty Plus 2x Barlow for about 30x magnification (Note that the H20 ep that came with the scope was also okay...but all of them had ridiculous FOV and eye relieve...but for the price, $40 scope with 4 ep's who can complain!). The Meade 24.5mm with the barlow at 24x also gave pretty good views...but I liked the added magnification. The un-barlowed Televue Radian at 50x also gave very good views...but I liked the views at 30x better. And yes the added aperture allowed me to use my NPB filter to good effect, teasing out details in the nebula. I never liked using my filters in the CO60 as the views were way too dark! Observing open star clusters was also a treat as I got great views of M45, the Pleiades Cluster in Taurus. Hell even the Taurus star cluster,usually hard to enjoy in scopes as it is so spread out looked good in the Firstscope. I can't wait to test the scope out on the northern summer sky, i.e. M57, M27, M17, M22 and all those wonderful objects in Sagittarius-Scorpius.


Any negatives? Well scopes, like gold clubs all serve specific purposes. That is why we astronomers have so many scopes in our menagerie ;) A scope that does well for deep sky might not be the best scope for planetary and vice versa. The Firstscope serves as an intermediate between binocular views of the night sky (rich field viewing) and slightly higher powered views of deep sky objects. For that purpose the scope fulfil's its purpose. Planetary views are fine if you are not going to push the scope to its theoretical max limit (a 3" scope has a theoretical max limit of 150x). In fact I would NOT recommend using this scope above say 50x since it has a non diffraction limited short focal length spherical mirror. You are going to be hard pressed in that department even with a parabolic mirror. My old StarBlast, while theoretically capable of 225x max magnification also did not do well in that department. So yes this is NOT a high powered planetary scope. Also the scope is very short so adults will have to find some platform to elevate the scope for use. Due to its relatively light weight, views also suffer if you place it on a non too sturdy support. So make sure you have a nice sturdy support for it. The other thing that I really found annoying was the placement of the focuser right on the top of the scope. I loved the ability to rotate the OTA of my StarBlast to a comfortable viewing position when seated. There was no way to do this for the Firstscope. Also the placement of the finder to the left of the focuser was weird for me as I am used to having my finders on the right of the focuser. Oh well small problem there. Most people found the dinky lil finder that came with the accessory kit to be stupid as it is one of them plastic 5x20 with stoppered down optics finder. I found it usesable for the Firstscope as the scope has such a wide field of view, it served as its own finder. All you had to do was get the scope pointing approximately at the right position, then drop in a low powered ep. No worries there.

So in summary I really like this super uber portable RFT. While not in the same league as my old StarBlast, which I might repurchase at some stage, it serves its purpose in the grand scheme of things. I can almost envision popping the whole shebang into my luggage bag for travel on board a plane and not having to worry about it breaking (it is so cheap and easily replaceable!). All I need is a car bonnet or a picnic table (or even sitting on a mat with a small stool!) and away I go. Plus it has a much wider range of magnifications than say my 20x80 so I can get some closeups of globulars and planetaries with the NPB and Skyglow filters in place. On top of it all its has a smooth dobsonian mount. Just look how small it is next to my 10" GS ;) Nuff said.....



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