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Posts Made By: Mike Damato

November 1, 2005 11:25 AM Forum: Eyepieces

Selling NEAF blem eyepieces

Posted By Mike Damato

Hi all,

I have a couple of NEAF blem ep's that I've had for about 4 years (purchased in 2001 at NEAF) that I want to sell. I can't figure out if this practice is frowned upon or considered unethical. I did purchase them for personal use - and used them alot - but now I want to get away from the heavier EP's and I could use the money to finance an ATM project. I'm probably going to sell a couple of used Pentax XL's also.

I figured I would charge a bit less than I paid and throw in a couple of plastic bolt cases.

Is there anything wrong with doing this? Is there any sort of classified ad rule against it? Just looking for clarification here. I read all the rules and can't find a definite answer anywhere.

Thanks,

Mike

November 21, 2005 05:00 AM Forum: Telescope Making

Vendor for 6" f/6?

Posted By Mike Damato

Hi all,

I want to build a 6" newt OTA for use on a small equatorial mount I have (Stellarvue M4, equivalent to old Orion Sky View Deluxe). I'm trying to pay close attention to weight issues in order to get away with it on this mount - aluminum tubing, helical focuser, etc...

Anyway, I can't find anyone who makes 6" f/6 mirrors. I'd love to use Discovery but does anyone know if they would accept custom orders?

Or does it sound like I might get away with a 6" f/8 on this mount anyway?

I know some of the high-end people (Royce, Mark Harry etc.) would take a custom order like this but a $500 mirror for this scope seems like overkill...I want to see if anything inexpensive is available first.

Thanks,

Mike

November 24, 2005 03:33 AM Forum: Telescope Making

Tube material vs. cooldown?

Posted By Mike Damato

Hi all,

I've been perusing this forum and whatever other ATM information sources I can find on the web, and it seems that there is some disagreement about the effect of tube material on cooldown issues.

Some people seem to think that an insulating tube material is best (sonotube, fiberglass, etc.) whereas others favor a high thermal conductivity material such as aluminum. In my case I'm leaning towards aluminum because of weight issues anyway, but it seems to me intuitively that initial cooldown will be faster, and ongoing thermal effects throughout an observing session less disruptive, with a material that conducts heat readily.

Is this an old controversy that has already been settled? Can anyone point me to an article or something that definitively settles it? I'm inclined to think that the more thermal conductivity the merrier, and in fact I'm thinking of using an aluminum tube and leaving the outer surface unpainted altogether. I can't get away from flocking the interior - aluminum is awfully shiny! - but finishing the outside seems unnecessary.

Am I all wet here?

Thanks,

Mike

November 30, 2005 07:01 AM Forum: Telescope Making

Mirror mounting

Posted By Mike Damato

Hi All,

Another topic that I'm pretty sure there's no consensus on - but I'm interested in hearing everybody's thoughts.

I know that large / thin mirrors have to be properly mounted or there will be very significant performance degradation. However, if you're dealing with a small and full thickness mirror, say a 6", can you get away with the "silicone blob method" without problems? I've seen some experts make disparaging comments about "bathtub caulk" but it's not clear whether they apply to small mirrors.

It's not so much that I don't want to spring for a proper mirror cell, it's that I'm building an OTA that will ride on an EQ mount so I want to have the mirror firmly mounted without diffraction effects from retainer clips. As far as I can tell there is no way to avoid the clips if you use a free-floating mirror design. (Am I mistaken?)

Also: What thickness spacers are to be used during gluing to ensure the "blobs" set at the right thickness? 1/8"?

I will most likely be using Discovery optics and according to their website the back of the mirror is properly ground flat. (I don't know if that matters or not...).

Thanks,

Mike

December 17, 2005 09:05 AM Forum: Eyepieces

In-focus question

Posted By Mike Damato

Hi all,

Maybe this is a dumb question, but I couldn't find a direct answer from using a search.

Which eyepieces from any of the major lines require the greatest amount of in-focus? I'm designing a reflector for minimum focuser height and I want to be able to cover a "worst case" scenario. I figure I can always use an adaptor for EP's that require more out-focus.

In my collection it is UO orthos that require the most in focus but is there anything out there that requires more? Tak LE's maybe?

Sorry if this was answered a million times already.

Thanks,

Mike

December 21, 2005 05:52 PM Forum: Telescope Making

Curved spider question

Posted By Mike Damato

Hi all,

I'm planning out a 6" f/6 OTA and I was going to use one of those curved spiders from Protostar. I realize that there will still be diffraction effects from the spider but that it will be in a sort of halo around the target rather than spikes.

My question is, for planetary contrast purposes, does the curved spider actually make matters worse? Is a three-vane spider a better option? Or is it strictly an aesthetic preference? I never tried both in the same scope.

Thanks,

Mike

December 28, 2005 07:29 AM Forum: Telescope Making

Help with damaged mirror

Posted By Mike Damato

Hi all,

I recently got a nice 6" f/6 Parks mirror that was damaged in shipment, and looks all scratched up (photo below).

I haven't disassemled the tube assembly yet to get a closer look at it because I have to deal with the postal insurance claim first. However - how can I tell if the damage is only to the coating or if the scratches actually affected the glass surface? Obviously it would be nice if I could fix this thing by just getting it recoated.

Also - if the scratches did penetrate to the glass, will the mirror still work well if recoated, or does it need to be refigured? Supposedly the mirror had a very nice figure on it already so it would be great to avoid refiguring.

Thanks,

Mike

January 17, 2006 12:45 PM Forum: Refractors

New technology from Lockheed

Posted By Mike Damato

Hi all,

Is this technical announcement of any interest? Or has this topic already been covered here in the past? It is from the official magazine of the International Society for Optical Engineering (SPIE)

>>>>quoted text:

Researchers at Lockheed Missiles and Space Company (Palo Alto, CA) have developed an optical color correction technology that will enable optical designers to create high-performance camera lenses and telescope optics with superior color correction and very high resolution at greatly reduced costs. The technology, which uses liquids to replace some lens elements, was devised by the Optical Design Lab at Lockheed's Palo Alto Research Labs. It is now available for license.

>>>end quoted text

Here's a link to the rest of the announcement (It's not really long enough to qualify as an "article"). I wonder if anyone knows more about it.

http://www.spie.org/web/oer/july/lockheed.html

Thanks,

Mike

January 21, 2006 05:21 AM Forum: Telescope Making

Glass ID

Posted By Mike Damato

Hi all,

I know there was a thread about this pretty recently, but I can't find it.

Is there a way to quickly and easily determine whether a mirror is Pyrex, without resorting to density measurements? The one I'm looking at has a greenish tinge, but it is very faint. IIRC plate glass has a rather strong green tint. Is that always the case? Will it only be a completely reliable determination if I measure density?

Thanks,

Mike

January 28, 2006 12:48 PM Forum: Telescope Making

Question about Hastings tubing

Posted By Mike Damato

Hi all,

When you get the ends rolled, does the lip protrude into the ID of the tube? I plan to make a mirror cell with an intact outer rim and bang it into the mirror end. I'm thinking this will help push the tubing into true round a bit (I know that's not terribly important in this application, but still...). If the rolled lip goes into the ID a little, though, I'm going to have to leave the mirror cell end unrolled.

Does just getting the ends rolled help push it into true round a little bit, anyway?

Thanks,

Mike