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Posts Made By: Dan Lamoreaux

July 5, 2006 10:03 AM Forum: Solar System Observing

Urban heat island effect on planetary observations

Posted By Dan Lamoreaux

I have always wondered what the urban heat island effect has on lunar and planetary observations. It is impossible to simultaneously compare the view I get from my driveway setup viewing planets to what it would be like if I were at my dark sky site some 30 miles away. Right after dark there is a lot of heat rising from the city, but I have never heard anyone speculate on its effect to the seeing conditions. Is it significant or inconsequential when added to the high level atmospheric turbulence that normally causes poor seeing conditions? Would the viewing be noticeably better at any given time outside the city? Light pollution is not a significant concern as Jupiter and the moon are plenty bright enough to overcome that. I am just trying to figure out if it is worth loading everything and getting out of town when clear sky clock says it is going to be a steady night for viewing. What does everyone think?

DanL

August 24, 2006 10:50 AM Forum: Telescope Making

Source for carbon fiber tubing

Posted By Dan Lamoreaux

Does anyone know a source for large diameter carbon fiber tubing? I am in need of some with a 9" o.d. for a ongoing scope project.

Thanks in advance,
Dan Lamoreaux

February 26, 2007 11:29 AM Forum: Eyepieces

Pentax 40XW v TMB 40 Paragon v Televue 41 Panoptic

Posted By Dan Lamoreaux

I am interested in a comparison or these 3 eyepieces and anyone that has had a chance to view through them side by side or even particular aspects about one of them that you have or have looked through and liked or disliked. I currently own the Pentax and TMB and have had only minor opportunities to do an A-B comparison of the two. I have been hoping for a chance to get a small group of experienced observers together and to do a controlled match up hoping to bring a 41 Pan into the mix as well. Since I have had the two I possess, observing times have been few and far between this winter and I have not wanted to spend a lot of time doing equipment comparisons, but preferring to actually observe. So far, I have not been able to discern a difference optically between the two. Each has some features to them that I like. I prefer the Pentax when star hopping with my dob. I wear glasses normally and need to keep them on when I am constantly looking up at the sky then down through the dob. The Pentax has the necessary eye relief to do this. I like the TMB eyecup because it is large and you seem to be able to get your eye down into it and really block out all peripheral light. It is also noticeably lighter than the Pentax. If I am using my goto sct, I will take off my glasses and set them aside preferring to view without them and then I go with the TMB. I really want to get a group comparison going to see if anyone can tell an optical difference. One of the best features of the TMB is the price, it being about $200 less than the Pentax. I am not sure the current price of the Nagler. I have a friend who says he has done a comparison between the 30 Pentax and the 31 Nagler and putting aside the afov issue felt the Pentax had an obvious edge over the grenade in contrast. He is one I want to include in the comparison of the 40s. Anyway, I just want to hear what others may have experienced with these eyepieces or ask me other questions about the two I have compared.

DanL

March 16, 2007 07:31 AM Forum: Eyepieces

Speaking of 31 Naglers...

Posted By Dan Lamoreaux

I'm sure many of you will enjoy this little ditty-

I regularly view in my driveway when I have limited time to pack up and travel to our observatory. Because I live in the city, I have constructed some light screens to block streetlights and passing car headlights. Due to a series of unfortunate events I had one of those Rube Goldberg moments. You know the ones where you start a ball rolling at one end and after a number of various contraptions it drops an ice cube into your drink glass or some such thing. Here's how it went for me. I have a LX200 14" fork mount that I have modified to accept various scopes with a G11 style saddle. This night I had my TEC 140 on it. Mistake number one. I had not anticipated any strong wind gusts that night so I had not run the ropes with tent stakes on the end to hold down the light screens so of course up came a puff just enough to push the screen into the dew shield of the TEC. Normally no big deal however this started the ball rolling. Mistake number two. I had not sufficiently tightened the dec. clutch knob which allowed the scope to swing up to about 70 deg. in elevation. Again no big deal except for mistake number 3. I had failed to properly tighten the saddle plate clamp knob which when suddenly tilted upward allowed the TEC to start sliding out of the saddle bracket. I reached for the scope and caught it with about a half inch to spare before it came completely out and I had a free falling apo on my hands. So far so good. I am managing to stay ahead of the ball until mistake number 4. I had just taken out my Nagler 31 and put in another eyepiece. I started to set the 31 on a tv tray I had set up next to me to hold various items, but I thought to myself that might not be such a good idea as I might accidentally bump into the flimsy tray and allow the nag. to fall to the concrete below. So now where to set it. Yes, up on the nice big flat area between the forks of the LX200 mount which is well protected and rigid from movement in case I bumped the tripod it would not budge. Ah yes, here comes the ice cube you say. As I grab the tilting and slipping scope thinking all is saved, I hear a distinct thud on the driveway at my feet. After thinking what the hell was that, it took only a few seconds for my mind to retrace my previous actions to realize the focuser end of the scope had cleared the fork base just enough to punt the Nagler off the mount almost like an extra point attempt right through the uprights. My immediate though after that was the irony of my wisdom of not placing the eyepiece on the tv tray to better protect it on the mount. The flagship of the fleet now set battered and bruised. The only good thing that happened was the Nagler survived optically having landed first on the chrome 2" sleeve forbidding it from ever holding filters again. That plus a fair amount of pavement rash to the black body as it rolled several feet more. The driveway did require patching however. 8O I now only allow myself to bring it out in the dark so as not to painfully remind myself of my cranial rectal insertion moment. I am sure at this point many of you are thinking that this man should not be allowed to be near high end astronomical equipment and are considering getting restraining orders before going to your next star party in the event I am there as well and not allow me within 50' of your site. I as well expect to be barred from the premises at NEAF after recounting this story.

DanL

September 4, 2007 08:28 AM Forum: Solar System Observing

Shoemaker-Levy 9

Posted By Dan Lamoreaux

I was watching something over the weekend about NEOs and they were talking about the impact S/L-9 had on Jupiter. I was not active in astronomy during the time this occurred. I was just curious if there was anything observable from average amateur class telescopes visually not photographically? I have seen many of the photos from professional observatory class instruments. Did anyone out there in amateurland actually see anything?

Cheers,
DanL

September 13, 2007 09:37 AM Forum: Eyepieces

Just placed the order...now the wait begins

Posted By Dan Lamoreaux

Thanks to a lead on another forum I found a vendor that has an Ethos in stock not committed. I placed the order and it is scheduled to ship today. Most of the other vendors I checked said they were not in stock yet or back ordered but could put my name on a list. I was hoping to have one in hand for an upcoming star party next month on the 6th. Looks like I will now. I figure if I put up a sign saying "ETHOS - 25 cents a look", I might recoup a sizable portion of my investment. wink

December 18, 2007 10:58 AM Forum: Refractors

Color corection vs. operating temperature

Posted By Dan Lamoreaux

In the case of a well designed and manufactured apo triplet, is there any significant changes in color correction if the scope is being used say at ambient 100 deg. F as opposed to 0 deg. F assuming the scope it throughly temperature stabilized? Do all the elements equally expand or contract along with the lens cell to keep everything in balance and harmony or is there a specific temperature that the correction is optimized for and a correction curve is generated for + or - that temperature? If it does shift, in which direction of the spectrum does it shift for higher or lower temperatures?

DanL

January 15, 2008 05:38 PM Forum: Refractors

The Zerochromat???????????

Posted By Dan Lamoreaux

Welllllllllll I have to say when I came across this scope in the latest issue of Astronomony Technology Today my curiosity was peaked. I went to their website to find out more about it. The site was not a wealth of information, but it did explain what is going on. So is this the next step in the evolution of the refractor or just a new twist on old ideas. I know folded refractors have been around for quite a while. What makes this scope so interesting to me is the simple design of the objective. Here we have an 8" color free refractor with all its benefits of unobstructed aperture without the nose weight of a triplet lens group in cell at about 2/3 the price. Collimation issues? I don't know. Maybe they are able to fix the mirrors in place and they never need to be adjusted. Some of the negatives I see is there doesn't seem to be much in the way of options. It looks like the diagonal is integral so dielectric upgrades may not be possible. The focuser may or may not be replaceable if it is lacking in smoothness or weight carrying ability. It appears to be a single speed. The light cone makes 3 passes through the tube like an SCT so tube currents come more into play, but the cool down time of the objective may make that a push. The overall weight is much less than a comparable APO triplet of equal size. The weight savings comes in making the color correction at the small end of the light cone. This probably won't appeal to many imagers as it is slow at f/12. It kinda makes me think of a MCT minus the central obstruction. So is getting rid of the c.o. worth about 3X the expense? That's certainly worthy of debate. So whatdayall think? Is this just an oddity to be relegated to the astronomy hall of obscurity or the perfect compromise between the high dollar APOs and the long focal length reflectors?

DanL

January 25, 2008 05:55 AM Forum: Solar System Observing

Mars images

Posted By Dan Lamoreaux

Does anyone know a website either amateur or professional where current images of Mars are being posted for this apparition?

Thanks in advance,
DanL

February 18, 2008 08:20 AM Forum: Equipment Talk

Re: Meade LX200 tripod

Posted By Dan Lamoreaux

I do believe that the threaded shaft for the tripod spreader on the LXD75 and LX200 are the same size and thread pitch. That said, I can think of a couple of reasons I wouldn't try it. Number one is the LXD75 tripod is designed to mate with the base of the LXD75 mount which is I believe a 60 mm. dia. recessed hole about 20 mm. deep. The challenge of setting a 10" LX200 on top of the LXD75 tripod which would only have a flat surface about 4" in diameter and balancing it while trying to secure the spreader bolt would be a challenge and you would risk it falling off if trying to do so by yourself. The other reason is if your tripod is like the one I have with 1.5" legs, it would be woefully undermounted for the weight of your 10". I thought I had heard somewhere that the newer LXD mounts had 2" legs but am not sure. If that were the case, the stability would be improved, but the physical mating of scope to tripod would not be something I would want to attempt. You will need a tripod designed for the large mating surface of the base of the LX200 and I only know of Meade tripods for that purpose. They show up on astromart from time to time in the $150-$200 range. That may not solve your immediate needs however.

DanL