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Bushnell Northstar 4.5" GOTO telescope
Submitted: Wednesday, 10th January 2007 by Colin Hutchison
northstar.jpg

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Bushnell Northstar 4.5" GOTO telescope

The Bushnell Northstar I have is a 4.5" Newtonian reflector approximately f8 with an advertised 675 x magnification. It cost about AU$275 on special. It was an impulse buy after a half day of research on the web. It was not a Tasco, and "Rubbish" does not turn up the same results as "junk"! My first scope. In retrospect it was a poor choice.

Anyway, it comes with an aluminium tripod and electronic GOTO alt/azimuth mount with "Real Voice" output. Having said that the specs for the telescope did not include focal length, and have been calculated from the eyepieces provided and checked against the physical dimensions of the telescope itself. For those who are unaware, the Tasco website ultimately lists Bushnell as the owning company, however there is no indication of the existence of Tasco on the Bushnell web pages. (see here: on the TASCO site  takes you "about us" to here: Bushnell) Bushnell provided no email support, nor did they answer any of my questions to their email address when I eventually found it. The telescope's electronics have a very limited warranty. Things may have changed since August 06 when I last checked.

The OTA itself is constructionally identical to a second-hand 1996 Synta corporation 4.5" telescope reviewed on "cloudy nights". It has the secondary mirror held on a single arm with three adjustment screws, and one retaining clip intruding over the edge of the secondary mirror.

A few comments on this remarkable telescope. When first bought the controller did not work. The shop where it was purchased exchanged the whole assembly for a complete new unit. The new box had lots of labels on it for sale in Australia which contained all sorts of caveats not on the original box advertising...

Assembly really was straight forward, a nice touch. Two bolts for the finder scope, two for the OTA, plug in a battery and clip in the stabilising accessory tray between the tripod legs. Finally, take off the covers and slot in an eyepiece.

The mount is too light and it is easy to knock the telescope over even with the legs fully extended. The stabilizing accessory tray does not positively sit down in its lugs meaning it has little value except as a tray.

The friction bolts needed tightening to avoid having the telescope slide downward with a heavy lens in it! The two star alignment is a bit inaccurate, and the telescope really does have to be dead level for the "goto" to work well. The rig runs on a 9 volt battery, and a good alkaline lasted quite some time (this surprised me). I ended up buying rechargeable NiMH ones anyway. It worked fine with 8.4v 170 mAh and 9.6 volt 200 mAh types. It did not work with super heavy duty carbon-zinc batteries. Another option would be to purchase a 9 volt transformer.

The hand held controler has no proper mount to hang it on as such and this is annoying. The "real voice" audio cannot be turned off as such, only ended early by hitting the back key. I found this very irksome. The GOTO system uses a two-star alignment which is not terribly accurate. The system also goes to sleep after 10 minutes which can be annoying. I believe the telescope can track objects, but does not indicate current time so who knows. The "goto" system gets confused easily, and I once set it up only to find myself in some kind of error-checking mode with fascinating headers like "check sum", "alt azimuth test", "rewrite" etc appearing on the display. Only after rotating the telescope on its mount through 360 degrees did it reset itself. I have had the telescope track Jupiter, but unless the alignment is very good, it tracks empty space.

How does it go? Optically, well at 4.5 inch and 900mm long it is about f8 which is not bad. The telescope came with a 4mm SR and a 20 mm Huygens. Both work after a fashion, and gave clerar shots of the moon, but eye relief and lens size are so small as to make the former hard to use and the latter nearly impossible. It also came with a X3 plastic Barlow (including misaligned lens). When used, even on the moon, the images were so dull and blurry that it performed no useful function. I eventually cut it up and used it as a camera mount. Views of the stars and Jupiter were good, within the limitations described above. I eventually got some plossels and a x2 Barlow from those nice people at the Bintel shop as well as some sound advice. The new plossels (a 25mm and 9.7mm) and barlow (x 2) made a world of difference.

The focuser was way too tight and using it inevitably dragged the mount from its target, This was loosened and re-greased with something less gooey.

The red dot finder scope is tinted with blue and yellow, this makes it rather hard to see any stars unless they are very bright. Attachment is by two lock nuts with fine adjustment in elevation and azimuth. The problem is that it is very easy to knock the finderscope out of alignment, although it is not difficult to fix this.

Fine control on the hand controller is not. The system works such that the longer you hold down the button the faster the mount traverses until you reach top speed. The speed varies between fairly slow and slow. However, trying to keep fast moving planets in view with alt/azimuth controls is hard work for me - especially when the lightest touch moves the mount so much. It really needs a variable speed dial of some kind. I use /Cartes du ciel/ which enables me to see what I am missing, and also tells me where to pint. Quite a nifty program that.

I finally got a chance to see Saturn whilst on holiday in the southwest. I got a five star rating for the alignment (the best possible) - which still resulted in stars being out of the field of view of the 25mm plossel (fov approximately 1.5 degrees) - mainly due to the mount not being truly level. Anyway I found Saturn, tiny but clear, in the 25mm plossel by knowing where it should be, observing it with the naked eye, and then bringing it into view. Adding the Barlow made it looked bigger, and I could just get it with the 9.7mm plossel and Barlow as well but not keep it in view. Even so a it was effectively impossible to get it back into view when lost by using the finder scope. Partly this was due to terrible condensation on the finder scope, partly the wretched low speed gearing being not fine enough, and partly slight misalignment of the finder scope. Even at x 180 it was still a rather small image. After a while I set about testing the star hopping, which was okay within limits, and it gave crystal clear views of the milkyway etc.

Conclusion

A nice OTA with poor quality focuser on poorer mount. The lack of level compensation in the mount is a real weak point, shipping with substandard optics. Light, portable, and with potential for adequacy with some better eyepieces and a little patience.

 

Review by Colin Hutchison (colhut). Discuss this review on the IceInSpace Forum.
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