Posts Made By: Gary Weber

Continued from part 1...

After an hour we came out and hooked up the battery and it powered the fans at their low setting just fine. Once again, it took about 15 minutes or so to get to 450x, but it worked and the image was very steady. After about 20 minutes the battery gave out and the fans quit. This was noticeable as the image deteriorated and at 450x was not sharp at all. We commented on this and placed the battery on charge again and went in for more tea.

About an hour later, my brother went to bed and I went out for more observing. Jupiter was high enough to try viewing at this point. The pattern repeated itself – about 15 minutes to get to high power while running the fans. Saturn was rock steady at 450x and Jupiter was steady only about 25% of the time. In the first 5 minutes of this session, Jupiter was not sharp at all at 310x. I could only focus a sharp image at 450x after running the fans for 15 minutes or so. After viewing both planets for about 20 minutes, I was chilled so I packed up and went to bed.

My preliminary conclusions are that running the fans indeed makes quite a difference in the ability to use high power. What would normally be considered limits due to seeing conditions can be mitigated by running fans in this configuration. Without the fans, 310x was effective part of the time. After running the fans for 15 minutes, 450x was rock steady on Saturn and moderately effective on Jupiter. The part that still confuses me is that there was no change in the ambient temperature during our observing session – it may have dropped a degree C during the two hours prior to our observing. The telescope had been outside all day and was fully cooled when we began observing.

Although this is not a comprehensive test, it certainly has sold me on the value of operating fans to get the most out of high power viewing.

Gary Weber

Although there are no duties owing on US manufactured goods (none on any astro geat I have ordered), there are other charges. GST (Goods and Services Tax) at 7% and whatever Provincial sales tax applies for the destination. Then there is the rather steep import brokerage fees charged by the carrier.

All these are the responsibility of the purchaser to pay upon receipt of the product. Why Fed Ex did not require payment when the goods were delivered is simply their mistake. When I receive goods from outside Canada, I am always required to pay ALL fees before the goods are handed to me (even Fed Ex).

The fact that they claim it's their "policy" to go back to the shipper for the unpaid fees is just their way of passing their mistake to you. Unless you have an account with Fed Ex that you want to protect and keep in good standing, I would challenge their legal authority to recover the fees from you. There is no reason you should have to pay for their poor administration.

You may also wish to contact the purchaser. If he knows the fees fall back to you, he may be more interested in coming clean on the transaction.

Gary Weber

I recently had a night of damn good seeing (not superb) and could make out the Enke Minima at 450x with a 8" f/8 reflector. Apparently, ( I say this not from experience, but from reading elsewhere) the Enke Division (or Keeler Gap depending on your preferred nomenclature) can be seen with an 8 inch reflector during nights of superb seeing and powers of 500x or more.

I think there are claims of this feature being observed in smaller apertures (Apos), but I am not aware of any confirmations - nor have I sought to find them. My chances of observing through a 7" Apo is pretty miniscule.

Gary Weber

I have compared the UO 40mm Mk 70 and the 40mm pentax XL in my 12.5 f/6 dob. The Pentax is the superior EP in my opinion. Although it has a smaller AFOV, the "usable" FOV is actually larger than the UO. What I mean is the amount of field with stars that are sharp is larger in the Pentax. The Pentax also has superior contrast. There were galactic details visible in the Pentax that were not visible in the UO. Many other visual points were first seen in the Pentax and then subsequently seen in the UO so I would say the difference was not that great, but the nod went to the Pentax. I also prefer the eyecup of the Pentax, but I don't have the eyecup for the UO so this may not be significant.

For f/6 or better, if making a choice based on performance, I would choose the Pentax. If a good deal came up for the UO on Astomart, I wouldn't hesitate to jump on it. If however you plan on using this EP in a scope faster than f/6, I would select the Pentax because of it's superior edge fidelity.

Gary Weber

Over the course of a year, all objects visible from your location will pass to the south (or straight up). Having an unobstructed southern view will maximize your viewing opportunities. Having a view to either eastern or western horizons for comets, Mercury, Venus and planetary groupings is also nice to have.

Gary Weber

Keep in mind that the focal point will remain in the same position regardless of the secondary or the focuser. If you go from a 3" high focuser to a 1.5" high focuser, you may require an extension tube so your EPs are out (away from the secondary) far enough to get to the original focal point. This may be what you need in order to use the bino-viewer.

If you want to move the focal point in (closer to the secondary) you will either have to use the travel in your collimation adjustment, or move your primary mirror cell further from the secondary (as suggested earlier). I'm not sure there is enough room at the lower end of the tube to move the mirror mount very much.

Do download and play with Newt.
http://home.att.net/~dale.keller/atm/newtonians/newtsoft/newtsoft.htm
It is a good overall program with quite a bit of information and by playing with the different parameters, you will come to a better understanding of what's going on.

Gary Weber

102 f/6 refractor - Nagler 3-6 zoom

12.5 f/6 Dob - 17 Nagler

8" f/8 dob - 13 Nagler (T6)


Gary Weber

I own a Starplitter that I bought used from a local member. I did a lot of research and although it is from what is considered a "premium" builder with options for various premium mirrors, there is little said about them on any discussion board. For a while there was a Yahoo group dedicated to Starsplitters, but I think it died to to a lack of activity

I have no sense of how many have been built and shipped, but the web references are few. I certainly like mine and have had no trouble tracking with one thumb and forefinger at 450x on nights of good seeing.

Gary Weber

I'm not sure this is your problem, however one critical element that cannot be done with a laser is to center the secondary in your focus tube first. This is what the sight tube is for (or a cheshire). You can also do this with a plastic 35mm film cannister. Trim the rolled lip off the cannister and drill a small hole in the bottom, then inset it into your focuser with the little hole for your eye.

Here is a link with some illustrations that may help with centering the secondary.
http://makeashorterlink.com/?B6F911E87
One of the things I have found that helps with this task is to lay a sheet of paper in the tube oposite the focuser. This provides a contrasty background and makes it easier to focus your attention on the position of the secondary while you're trying to center it in your view.

I think once this task is done, your laser should bring the rest of the system into alignment. I used to use a laser for collimating my dob and then I bought the Tectron tools for collimation and ended up selling the laser.

Good luck.

Gary Weber

I tried flocking a dew sheild with one single roll of flocking paper. I was a miserable experience. Later I flocked the tube of an 8" f/8 and I used a partner and layed a series of strips lenthways in the tube. It worked very well.

Gary Weber