Posts Made By: david roberts

And then there were escrow accounts. may be too much trouble. but if serious about a 4k transaction, then maybe not so much.

I had the same thought. A larger one is located in the botton left. The smaller ones are all over the place. Are the reddish round fuzzies galaxies??

regards

dave roberts

Over the past few years it seems hundreds of car stereo installation shops have opened up, almost on every corner in the larger cities. My bet is that they must have leftovers, discards, etc of all shapes and sizes. May give a few of them a try?

regards

david roberts

I had a similar rude awakening. I wanted to sell my old Olympus 35 mm camera with zoom lens. I had got a digital camera for Christmas. A guy at Wolfe camera said the 35mm body and lens should bring at least $150. He thought the lens alone was worth $150. So I took the camera body and lens to a large camera shop in town (Houston) known to buy second hand cameras.

The person behind the counter pointed to about 200 second hand 35-mm cameras in glass cases and said that its all about digital now. A 35mm would have to be in perfect shape for him to even consider buying it.

By the way, he had at least twice as many lens for sale. He admitted he will take a beating on the 35mm stuff.

I walked away with the camera in hand. It makes a great paperweight these days.

sincerely

david roberts

Thanks for all the responses. There were several questions regarding the method of cementation, collimation tools used, etc. I'll try to answer each.

The coma image is in the middle of the ep. The mirror clips are not used. I don't believe the secondary is pinched.

I used GE brand silicon bought at the local hardware store. I started to use spacers made of wood but thought the spacers were to thick (about 1/4 inch) so at the last minute I pulled them out, with no Plan B. The mirror rests on the mirror cell with minimal air space (less than 1/8 inch). I probably used to much silicon as well. It will be difficult to cut through all the silicon. I read here that dental floss works well for sawing through the silicon. Is this the method of choice?

I use a laser to align the secondary, making the laser point hit the donut by adjusting the secondary. Then I use a cheshire to align the primary. It works just like the Mel Bartel's page and some other collimation pages. This is the reason I think I'm pretty dead nuts on for collimation, except for the offset thing which I really don't understand well.

Someone mentioned pinched optics, which is an option since the mirror sits directly on the mirror cell with only an 1/8 or less silicon/air inbetween. The mirror may be touching the screwheads used for collimation.

I'll try collimation one more time when weather permits and if that doesn't work I'll take the mirror off again. Man I don't want to do that but the star image is just unbearable. I have no real ability to split stars.

Any other clues would be appreciated.

Sincerely

David Roberts

I had a friend who owned one of those. It's a duel purpose lawnmower, vacuum cleaner, air compressor, hot water heater, beer keg, skeet, telescope apparatus. But his didn't have a pressure gauge like that shown near the bottom. Maybe that's why he blew himself up one night.

I just wonder if a 6" scope would completely throw it out of balance. Could always use a broken toaster weight to fix that, I guess.

regards
DCR

You might try The STScI Digitized Sky Survey:

http://archive.stsci.edu/cgi-bin/dss_form

I typed in KUV 18217+6419 in the Object Name box at the top of the page and clicked Get Coordinates and got the ra and dec. Then I changed the File Format box from FITS to GIF and clicked Retrieve Image. There's no arrow pointing to the object :S

Good Luck

DCR

Been there, done that, and I've had no problems. I believe it is the accepted way of mounting your mirror to the mirror cell. You can cut the clip at the 90 degree bend using a hack saw. Then I placed three dabs (about 1 inch square)of silicon (GE brand from Home Depot)on the cell and lowered the mirror onto the silicon. Be sure to place three or four stacks of pennies (3 or 4 to a stack) around the edge as spacers. When the silicon dries, remove the pennies. Then place a dab of silicon between the side of the mirror and the vertical part of the clip. I've never had a problem with the mirror while driving over surface streets. Can't say what would happen in a rough off-road situation.

$500 for the Coulter 17.5 is a bargain. I bought a Coulter 13.1 for $550 two years ago, and most Coulter 13.1s showing up on Astromart classified range from $450 to $600 as originals.

A thin mirror can show astigmatism not only due to optics quality but also due to mounting. A thin mirror will sag and can be deformed by its own weight. I had that trouble with my 13.1.

The cell, if original (and it appears to be all original) is the sling type, which can exaserbate any built-in astigmatism.

Coulter also had a problem with turned down edges, but that problem can be fixed by masking a portion of the edge. This will reduce the overall effective area of the scope but it may not be so bad.

One last thing, the original secondary is larger than needed I believe, and a smaller secondary will help reduce obstruction.

Our astro club owns a 17.5 inch Coulter that we are happy with. But forget about transporting unless you've got a trailer and 4 hands minimum. Ours is stored in a closet which we roll out onto a deck during star parties.

Swayze Optical - Refiguring Service will test and refigure for an advertized price of $570 and send it to Spectrum for recoating for $230 (doesn't include shipping or taxes). He may charge more if it is really poor optically. Not a bad deal at all. I plan on giving Swayze a try this winter. A new Swayze 18 inch is $2,280.

Swayze is in Portland, OR at:

http://www.europa.com/~swayze/

best of luck

DCR

Half of a WW2 surplus (or garage sale) 7x50 bino.