Posts Made By: david roberts

Should I be able to resolve individual stars in M3 on a dark night, with M3 sitting about 40 degrees above the horizon, using an old coulter 13.1 inch, f4.5 newtonian with a 9mm plossel ep? In the same vain, should I expect to see any structure in the larger and brighter Messier galaxies, other than just a fuzzy lump?

I understand you have the Orion or look-alike Adorama wide angle eps and are satified. You responded to my post about my current dissatisfaction with the eps. Since you are familiar with the performance of the eps in a large aperture fast scope, I may have gotten hold of a bad batch or my mirror is screwed up. I've collimated the scope many times. I rarely need to turn a screw more than an eighth to quarter turn to bring the cross-wires of the cheshire tube back to the center of the little circle on the primary. BTW the secondary has a dot which also aligns.

My proposition is to send you a couple of the eps, namely the 9 and 15. You check them out on a steady night. If they don't work for you, I know the problem is with the eps. I you find no problem, then I have the local telescope dealership here in Houston take a look at the scope.

I pay for shipping and insurance both ways. There no good to me now and some resolution can help me move on with this and decide the next step. If this is something you would be willing to do, please let me know and I'll exchange email or address with you.

Even though Adorama gave good customer service, they may be slightly bias. I need objectivity.

Appreciate you thinking it over.

I bought a 13.1-inch Coulter a few months back. I've heard Coulter made some good mirrors and not so good mirrors. I worked up the courage to take the base of the scope off - the mirror cell with the mirror. The cell was fairly new according to the previous owner. The mirror was secured with silicon or similar product. The mirror measured 5/8 inch thick and the number '#328' was written on the side with a felt marker. A minus 2, as in '-2', enclosed in a circle was also written twice with a felt marker. Now the question is, was this one of the better or not so good mirrors? What does the -2 stand for? Is it possible to date the mirror based on its number? I haven't tried high magnification, such as 300 or above. I was just wondering how this mirror would rate in the universe of Coulter mirrors. Does anybody know???

Thanks

David Roberts

I'm considering the purchase of a holographic laser collimator (Howie Glatter maybe ???). More important to me at this time than the manufacturer is whether a holographic collimator is right for me, and will give better collimation on a 13.1-inch primary at f4.5 reflector. A friend used a pinpoint lazer collimator to set my seondary and primary, and now I'm thinking of buy a laser collimator for my own use and to help others. Would I be just as satified with a simple laser collimator. Is the holographic component that much better. I've been using a cheshire and would continue to use it as a backup. Appreciate any advice.

Coming back to stargazing has been a lesson in frustration and patience. I've out of the picture for the past 7 years. With the seemingly ever-present nightly overcast, city light pollution, and now smoke-filled skies from the burning of Mexico fields, I'm about to burst wide open. One night I packed up my gear and started to drive in search of clear skies. I made it 170 miles before giving up. In February I bought a used dobsonian light bucket with no eps from a very nice man, Ben Hugens. I quickly bought a 32mm plossl and 2x barlow from Telescope Warehouse, lets say quite inexpensive, but not cheap. I picked up a Telrad and was ready to spend my nights under the stars. If it sounds to good to be true, watch out. Since February, I've spent maybe 6 or 7 decent sessions observing, and I guess I'm lucky, considering some of the posts I've read lately.

But instead of being depressed, having a new toy, with nothing to see, I decided to get ready for summer. I purchased a 13.8 and 18mm swa Meade from the Astromart classifieds and a Meade 4000 26mm, and a Cheshire collimator. I purchased Brent Watson's two volume 'Finder Charts of the Messier Objects' for Telrad users, Nightwatch by Terence Dickerson, The Star Guide by Robin Kerrod, SkyAtlas 2000.0 by Wil Tirion, and the National Audubon Society Field Guide - Night Sky. I've printed most of what is offered on the SEDs website, which equates to a stack of paper about 1 foot thick. I had forgotten much more than I remembered. I hear that happens to old people!

I've made lists of what to look at, where to look, and when to look, marked pages, drawn in the constallation lines on the SkyAtlas, underlined the M and several NGC objects, joined the local astronomy club, and have volunteered with the telescopes on wheels group. Most of my successful sessions have been volunteering, so much of my time, at least until 10:00 was spent keeping Jupiter and Saturn in the ep for the young and old alike. The oohs and aaahs are worth it. One kid pulled out my ep out of the focuser thinking I had drawn Saturn on it. Both ep and child are safe now. I've been really frustrated as I started astronomy in the desert of southern California. No humidity, no clouds, not much light pollution. I was spoiled rotten. I thought that was the way it was most places. Living now on the Gulf coast is a challenge, but I guess seeing in most of the US is a problem nowadays. All I can say is if its overcast during the upcoming new moon, I'm headed west as far as I can drive in 10 hours and make it back for work Monday.

May clear skies be with you

David Roberts

I have an old coulter 13.1 inch dobsonian with a seemingly hugh secondary attached to a thick metal bar. Its original. I'm considering replacing the secondary and holder. I understand somewhat that the size of the secondary is related to the size of the primary, something to do with the lightcone. I'm not sure at all. I thing this original secondary obstructs someting like 30 percent or so. It looks like a monster when defocused. And it will show it if not in dark skies. Does anyone have any suggestions about a good replacement? What is the minimum size I can use. Thanks

What is a field stop. Is it a baffle in the ep? Does it limit the FOV. Why have a field stop. I don't have a clue and was just wondering what its all about. Thanks

Last night was the first time I saw the Airy disc and concentric circles as viewed through a 9mm Nagler in a 13.1 inch newton. I had tried before but I guess the seeing was poor. I was kind of thrilling, see those tight concentric circles for the first time. But the scope was way out of collimation as the center was skewed to the left. I have lost the link to a website that shows photos of airy disc, in and out of focus / collimation. Does someone know of a good site. Thanks in advance.

David Roberts

David Roberts

I drove 75 miles tonight to a wonderful dark site. Clouds were moving in while driving and the chances of good seeing were gonna be less than 50/50. By 10:00 I gave up with about mag 2 skies. I can get that in my backyard! All geared up and nothing to see. Bur prior to departure, I worked on collimating my coulder 13.1 f4.5 dob. I don't know which is more frustrating, overcast skies or collimating a fast scope. I'm learning about collimation. Today I fiddled with the secondary. The previous owner has placed a very small dor on I assume the optical center, althouth it may be the mechnical center. I guess I could measure to find out. I could not get the dot in the crosshairs of my cheshire. I could get it on the horizontal line of the crosshair and just a smidge to the lest, but not on center. I then centered the donut on the primary and I must say, this is the best it has ever looked through the cheshire. Practice, practice, practice! The secondary is attached to a thick steel bar, original to the scope. Tonight was the first time I say two distinct spikes when viewing Jupiter (about the only object visible). I assume the secondary is lined up properly now because I've read that 4 spikes are seen with a 4-vane spider. Is this a correct assumption? Also the airy discs were much more prominent and better centered. I have a laser collimator on order. Should better results that with a cheshire? Any collimation gurus out there. Thanks in advance.

David Roberts

Does anyone know of a star chart publisher that issues a star chart, sky chart, etc., that is reversed, similar to what you see in the ep of a newtonian? Having to perform mental gymnastics, especially after 1:00 is hard on my remaining gray matter. If not, maybe I should talk to Wil Tririon (sp)! There should be a market. I'd pay a premium. Would you?