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Posts Made By: David Tarshis

December 24, 2003 09:47 PM Forum: Equipment Talk

Merry Christmas and Happy New Year!

Posted By David Tarshis

Right back at ya bob, the 3 wise men will probably bring my ed80 (epifany), I'll be leaving my shoes out on Jan 6. Cheers!

January 19, 2004 02:41 PM Forum: Equipment Talk

You know you need to buy more astro gear when

Posted By David Tarshis

It's funny you mention that. I have cupboards full of little cardboard boxes. My wife wants to know what I'm going to do with them. I'd rather take up a little garage space, than have to scramble for a shipping container.

March 30, 2004 11:26 AM Forum: Equipment Talk

ClearSky Problem?

Posted By David Tarshis

I have no problem.

April 22, 2004 09:34 AM Forum: Telescope Making

First night with John Dobson (long)

Posted By David Tarshis

The room is quite full, the mirrors range from 6” to 14”. John walks around the room giving instruction’s to individuals as they need it. I pay attention to these individual instructions, and managed to not get yelled at all night. There is quite a buzz in the room. Everyone seems to be exited to get started. After a while, John wants the attention of the room once more. It takes a raised voice and a “shut up” from John to get the room silenced once more. We were warned about his yelling at one of the pre class meetings, now we get to see it first hand. Johns yelling is quite harmless. Although his voice is raised, it’s not very loud. After some new instruction, and more stories, we continue to grind some more. It doesn’t take long before I have to take off my sweat shirt. Looking around the room, others are doing the same. The class is mixed, in one corner is a father and son team with a mirror each, next to me on my right is a husband and wife team on one big mirror, it looks bigger than my 12.5, and I guessing it’s a 14. My friend Dan is across from me, we trade notes back and forth as we get new tid bits of information. By the end of the night, we seem to get the hang if it. Two and a half hours later, more the half of the class has left to go home. We check our mirrors with a straight edge, there is a curve in this chunk of glass that we been grinding on! There is only a couple of die hards left. A gentleman with a 6 inch checks his curve with a straight edge. John needs a dime. He lays it on the glass, the straight edge clears the dime. Evidently, too much curve. Sean checks the focal length with a flash light. It’s about a f6. This is the gentleman’s first telescope, and doesn’t quite understand the difference between a slow and fast mirror. Sean explains the pro’s and con’s, he seems to be content on his work. This guy rough grinded a 6 inch mirror in one night. This gives me hope that I can finish my 12.5 this year. We clean up our mess and head home. It was a long night, but we didn’t notice. It’s 10pm. Dan and I talked about the previous 3 hours the whole way home. I was in bed an hour later, it felt like the first night after xmas day. I was exited about this whole adventure. Thanks for reading, DaveT

I know this was a long post, the others will be shorter.

April 26, 2004 11:20 AM Forum: Telescope Making

First night with John Dobson (long)

Posted By David Tarshis

Or I should say, the second night of grinding. The second night with John was less hectic. There were a few no shows. We arrived a little early and examined our mirrors that we had worked so hard the few nights before. I noticed that my efforts had not reached the edge of the glass. I looked for John, but he hasn’t arrived yet, as I was informed, “it’s 3 minutes to 7, he should be down soon”. I found out later, everything was fine. Doing a 12.5” mirror as a first mirror makes me a little nervous. Within a few minutes the class was a buzz again, everyone grinding away. It didn’t take long for the sweat. The only things missing are blood and tears. I noticed the fan was not in the room this time. I went upstairs to look for Sean, there was the fan, trying to pull the air out the back door. The weather was beautiful. I found my new grinding spot, on a slab of concrete behind the church, outside. By the time I got my bench and glass outside, I was joining another grinder from the class. There were no clouds and a slight breeze, I couldn’t wait to see what the seeing was like in this rural part of Washington. I didn’t get a much grinding done although the conditions were great. It turns out I was moving my lips more than my arms. After the sun set, we joined the others in the basement. As I came down the stairs, there was John, helping one of the students. He was working the water and grit as the student grinded away vigorously. She seemed to enjoy the help, John seemed to enjoy giving the help. As for the rest of us, it was yelling as usual. I watched as John poured the grit on the glass, more grinding and then gave “two” rinses of water. I tried that method on my glass, it seemed to work pretty good. She finished rough grinding her 10” that night. By this time it seems that the 6 and 8 inch mirrors are completed with the rough grinding. I’m still grinding away at my 12. A lot of people were checking the focal lengths before the sun set completely. My friend Dan’s 8 inch is at approximately 6 feet. I’m eager to check mine tomorrow. (cont)

May 12, 2004 12:31 PM Forum: Telescope Making

12.5 mirror cell vender list

Posted By David Tarshis

Wow, looks cool. What’s the price? And yes, I'm building a Dob. He also happens to be the instructor of the class. This will be a later upgrade from the original John Dobson plans. The Dob I'm building at the moment, will be in a 14 inch sonotube. Thanks to all who replied.

May 19, 2004 04:32 PM Forum: Telescope Making

Mirror Scratches

Posted By David Tarshis

I have a feeling you will get multiple answers on this. Here is my experience on my 12.5. I have reworked several times now. I have a total of about 20 hours into the grinding/polishing time. I hope to start parabolizing soon. I know the defects that are/were in the mirror. With the money I have spent on the mirror so far, I'm doing everything possible to get it right. As far as small scratches go, probably invisible at the eye piece. As far as pride? That’s up to you. You will always see those scratches when you look down the tube or box and wonder....just how much time would it have taken me to go back a step to get that right? Remember, the aluminizing will bring out all defects. Good luck, DaveT

May 29, 2004 01:00 PM Forum: Telescope Making

scratches in mirror surface

Posted By David Tarshis

Aluminizing will enhance any surface damage of the glass. Can you tell if the scratches go beyond the coating? Shine a flashlight from behind (if the back is clear) and see what the damage looks like. If the scratches dont go through coating, get it re coated. Secondary's are cheap enough. Check out L&L's price list: http://www.llopt.com/as.html
If it was me, I would remove the coating to look see. Did you buy it in this condition? Just wondering. BTW, is this a diagonal for a SCT or a dob? I'm guessing dob. If it's for a SCT, don't know what to tell you. Maybe compare with another diagonal in the scope and see just what kind of difference there is. Good luck

May 31, 2004 09:25 PM Forum: Deep Sky Observing

observing in Hawaii

Posted By David Tarshis

In answer to your question, yes, you can see as "far down" as the Crux. Will you be able to see the Crux? Answer is no. It is above the horizon during the day when you will be there in Aug. Right now it's above the horizon at night. Check out the pic I included, it is a screen shot of Starry Night Pro with Hawaii for a location, at about 11:30 at night looking south on the ninth of August, almost the middle of your trip. I labeled planets, brightest ngc objects and messier's. Let me know if that helps. Have a good trip.

May 31, 2004 09:32 PM Forum: Deep Sky Observing

observing in Hawaii

Posted By David Tarshis

Here is the Crux as it looks tonight in Hawaii.