Posts Made By: Steve Gibson

Hi Brian

i was a bicycle mechanic for several years, and the best degreaser i came across was Simple Green. it's labeled as an "all purpose cleaner" but it does a great job as a degreaser when used full strength. as a bonus it's also non-toxic and biodegradable. you can pick it up at Canadian Tire.

Steve

hey Tom

is your scope balanced on the mount? it looks like you have it mounted right near the focuser, which would mean it's out of balance if your achromat has a long tube (unless you're using a heavy star diagonal and eyepiece). if the scope is out of balance i would expect the mount to give jerky motions, especially in altitude.

hope this helps..

Steve

hi Robert

I have one of these scopes. When I bought it (new) about 15 years ago it was known as the SPC6 since it came on the Super Polaris mount.

First off, I have to say that I have had lots of great views through this scope. I do visual observing only, so I don't have any astrophotos to show you that I have taken through the scope.

There are a few things that you should know, however. The focuser is of the "sled" type and only accepts 1.25" eyepieces. It is a sliding plate that has the secondary attached to it via a wide, single stalk. To focus, this sled moves the secondary towards and away from the mirror.

The sled does tend to slip when the scope is pointed near the zenith, and this is only with an eyepiece and a barlow. It does have a tension/locking screw, which works for me, but this might be more of an issue with a camera attached.

One thing to note is that I did try to attach an SLR to it once via a T-adapter, and the camera would not reach focus. The focuser has tubes of different lengths which screw into the sled, but even with the shortest one supplied it would not reach focus.

As well, it has a huge 2" secondary. This maybe be fine for imaging, but is not so great for visual observing as far as diffraction effects and decreased aperture are concerned. And it is not an easy matter to swap in a smaller secondary due the size and design of the secondary single stalk support.

Finally, I think the main mirror is astigmatic. This is obvious during a star test. When the mirror cell is rotated, the star test image rotates with it, so it's not the diagonal. One thing I wonder about is that the problem might be with the moving secondary. The focuser is simply bolted to the tube; if it is not properly aligned the secondary will not be moving along the optical axis during focusing. One thing I'd like to try is shimming the focuser to ensure that it is moving the secondary on-axis.

Anyway, a bit long-winded but I hope this helps.

steve

hi Tim

I have the same problem with my Firstscope 80 (achromat, f/11). I've added a 2" diagonal, and now I don't have enough 'in' travel to reach focus with a couple of my eyepieces. I think the problem is that these scopes were designed for beginners, and it was assumed that the owner would only use the 1.25" diagonal that was supplied with them (I had to machine an adapter to get the 2" diagonal to fit on the focuser). 2" diagonals are larger and use up more of the focal length (as do binoviewers), which is why the focuser's range of motion is now too far forward. (I apologize if you already know this)

As far as I know, the only way to fix this is to shorten the tube, as you mentioned. The best way to do this is to shorten the focuser end of the tube. This will leave the baffle in the right place. Most focusers are attached to the tube with three bolts, so you would 'just' have to cut the tube square to the right length and redrill the three holes. However, this is generally not recommended, since you can never go back. If you shorten the tube, it may not have enough 'out' travel to be used in it's original configuration without the 2" diagonal.

Personally, my scope is just a 'grab and go', so I haven't shortened the tube - I just put up with the fact that I can't use a couple of eyepieces with it.

Hope this helps.

Steve

hi Mitch

It sounds like it might be a custom secondary heater you have there. Are there any sort of numbers or markings on the 'transistor'?

Hopefully the system wasn't designed for 9V only (9V batteries have quite low amp-hour ratings). The power put out by the heater will be determined by the equation:

Power = (Volts^2)/Resistance

This means that if you increase the voltage from 9 to 12 volts, you increase the power by a factor of 1.78 (or more, since most 12V batteries sit at 14V when fully charged). Depending on the design of the heater, this might be a problem. If the heating elements are resistors, this might put them over their power rating - meaning they will get too hot and burn out. Are you able to see any of the heating elements, or are they hidden within the secondary holder?

Hope this helps...

Steve

hi John,

There was an article in Sky and Tel a few years ago that described setting up a solar-powered observatory. It's in the Sept. 2002 issue.

Steve

hi Stuart,

The fasteners you need are widely used on mid- to high-end bicycles. They are used to attach the handlebar and stem to the fork, and go by the name 'star-fangled nut'. For bikes they come in two sizes, to fit either 1" or 1.125" tubes (OD). Any good bike store should have some in stock.

McMaster-Carr (as Bill suggested) will probably be the cheaper option, but I thought I'd let you know of this just in case.

Steve