Posts Made By: George Golitzin

Clausing ( http://www.clausing.com/main.html ) used to do the secondary for a very minimal fee if you were having your primary done...But have you looked into it? I should think any of the reputable coaters would take your secondary--for example L&L ( http://www.llopt.com/as.html ) specifically advertises coatings for secondary mirrors, and everybody seems to like them...
George

Inge, did you notice a remarkable asterism just off the southwestern tip of 134? It is a square of roughly equal mag 10 stars, about 5 minutes on a side, with a little mag 12 or so star smack in the middle. An arresting sight next to the fine galaxy.

Regarding 253, I have often had the same emotional response at the eyepiece from my dark site at hyampom (http://www.cleardarksky.com/c/HympmCAkey.html?1)
--with a 13" or my 16", the mottling, dark lanes, and eery glow find expressions in my journals such as "mind-blowingly beautiful" (9/03/05) "fabulous!" (9/20/04) and "incredible" (10/24/03)--a photo (no offense floyd--that's a nice photo!) cannot touch the experience at the eyepiece..so often I come away from these encounters refreshed in spirit, and thankful.
--george

Hey Bob,
I have had a UO cell pass through my hands and had a good look at it--but I've always only used my home-made cells. But I'll try and answer your questions....

"The UO mirror cell appears to provide centering adjustments by means of its mounting screws. Can anyone confirm whether this is true?"

YES.

"Also, the cell retains the mirror with rubberized (?) metal clips. Will the clips cause distortion of the image created by the mirror?"

NO, if you're careful. The clip height is adjustable--I would set it just above the mirror surface, so as to catch the mirror if for some reason you tipped the scope below horizontal. Or you could follow Royce's advice and just eliminate the clips (they were removable on the model I had), and install a stop on the rocker box to avoid tilting the scope that far. Now you could bring the clips in contact with the mirror, and most likely any contraction in the metal would be absorbed by the rubber, but I don't think that's necessary.

"The mirror is attached to its backing plate in the current cell with adhesive of some type; possibly RTV. What's the best way of seperating the mirror from its plate? "


REMOVE the cell with mirror. place a clean cotton cloth on a table and put the mirror face down on top of it. Cut the atv with a thin gauge wire or long knife.

"This scope has never collimated the way it should and performs rather poorly on close double stars. I'm hoping to correct these problems by centering the mirror in the tube and re-collimating. Is this reasonable, or should I look elsewhere?"

You cannot have any idea of the quality of the optic until you have collimated it properly, so I would try something like the above first.

best wishes,
george

Hey Keith,

At half the price of a 6" D&G lens, that looked like quite a deal--I'm looking forward to hearing about the views through your new scope, particularly planetary, once Mars and Saturn show up--keep us posted.

BTW, that material looks like a tile backer-board (?)--just curious...

--George

Can't speak about the Royce but I'll throw in my 2 cents on Discovery--I had an 8" f/5 that was a little gem, and a 10" f/5.6 that was a dog. Ok the 10" was a pretty old mirror and maybe they improved their QC, but...

To me, a primary reason for building my own scopes was to take the savings and put it into the best optics I could afford. At $1350 or so, Royce, Stevens and Swayze all represent good buys on a 12.5" f/5, albeit a good $500 over the discovery. I imagine Zambuto is yet somewhat more. I suggest you have a look at these other two guys as well as Royce:
http://home.europa.com/~swayze/pricelist/pricelist.html
http://www.stevensoptical.com/mirrors.htm

Good luck!
George

I'm rooting for the bad guys!

Inge--
That's funny, I recently started compiling a list of favorite ngc entries, with "best spirals" as a sub-category. I have 11 entries too--the same 11 entries! But I also made a note to check 4536 from a dark site--I think it might show its two arms. As for having seen the best spirals, have you viewed 2997, the fine spiral in Antlia? (mag 9.4--same as m74 fwiw)--I haven't seen it, and I wonder how it stacks up against the others...

--George

Inge--

albert highe has a big page on this topic, it's one of his chief observing projects--here's a link to a finder chart from him:
http://pw2.netcom.com/~ahighe/A426F.jpg

and here's a link to the page on the perseus cluster:
http://pw2.netcom.com/~ahighe/a426.html

You can enlarge the jpeg and it's pretty nice.

--geo

p.s. check out the observing list for the cluster on the main page.

I'm no filter expert, but I'll make a couple of suggestions.

In general, you should note that filters, while cutting down on the admitted light, will not lessen resolution, but usually enhance it by increasing contrast. However, it's easy in a small scope to filter out more light than you want to, resulting in a dim image, particularly at high power.

Your scope will show some color on the moon and planets, so your fringe killer filter, by suppressing the unfocused violet on the moon, might well boost your resolution on that target. I personally don't see the need for a moon filter per se at that aperture (probably others will disagree)--my reasoning is that one generally likes to take the power up as far as possible on the moon, and in a 4.3" refractor, the resulting small exit pupil will be plenty dim without further filtering it.

For Mars, you might consider a #21 Orange filter--very inexpensive. It lets in plenty of light (the red and light red filters might be too dark at that aperture) but will really enhance albedo features. For Saturn you might also try a #82A light blue, if anything. The light blue is also good on Martian clouds/ice.

I'll let someone else speak to the light pollution issue.

For more on filters check this link--there's also some good articles at CN.
http://sciastro.net/portia/advice/filters.htm

--George

I'm surprised at the lack of power in some of the above posts... well here's my current collection, and I've been quite happy with it. My dobs are f/5 and f/5.6, and I recently picked up a 102ed at f/7.

27 pan with 2.0 dioptrx
16 t5
11 t6
7 t6
2x and 2.5x TV barlows

and that's it! don't you all admire my self-restraint?

I guess that's cheating with the extra barlow--but sometimes I want that extra bit of power.

--sooo, should I change out the 27 pan for a 26 t5? or maybe it and my 40mm(rarely used) for a 22t4 and a 35 pan? should I dump the 16t5 for the 17t4? Yeah, the eye relief's a little tight, and I do have astigmatism, but the contrast on that 16mm is incredible...And I still can't imagine a 1.5 lb eyepiece on my lightweight 10" truss dob.

--george