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The Year-Long 60mm Telescope Challenge

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#51 jrbarnett

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Posted 09 April 2013 - 09:57 AM

Yup. The range permitted in the article is any aperture from 60mm to 69mm, so the Zeiss is definitely a valid tool for the attempt based on the guideline.

In fact, I would even accept a well-constructed argument that a considerably larger catadioptric (such as a 90mm MCT) was inefficient enough to deliver actual light grasp on par with a much smaller unobstructed scope. If folks want to come up with a calculation of equivalent unobstructed light grasp for small catadioptrics, I'd have no objection.

If I do this with my Celestron C90 (aluminum with SiO2 overcoat on primary and secondary, multi-coatings front and back on the corrector) here's what I come up with: 90% reflectivity for each mirror surface, 99.5% transmission for each surface of the corrector (the corrector is not XLT coated, but rather standard Synta multi-coated), and a secondary obstruction of 10% by area, I get something like a 75mm fully multi-coated refractor equivalency. You'd still need to stop the average 90mm MCT down to meet the requirements, but by something more like 7-8mm rather than 30mm.

Regards,

Jim

#52 t.r.

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Posted 09 April 2013 - 01:15 PM

Well, I have taken this challenge seriously after Jim suggested piggybacking my 60 on my primary scope so as to not miss out on valuable observing time with my larger scope. But, I feel I need to upgrade the focuser to accomodate the better 1 1/4" format eyepieces and really let my Towa lens loose and perform to it's full potential. So, just got off the phone with Dan at Crawmach about a focuser and extended flange assembly to get the extra long focal length required to reach focus with my Jason(has the inner drawtube which sags). He has done one of these "longer" focusers before and said once my measured specs are received, about a month build time. Of course rings will be ordered too! :grin:

http://www.crawmach.com/



#53 Astrojensen

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Posted 09 April 2013 - 03:30 PM

I've found a piece of aluminum tube that fits a custom cell for one of my Zeiss C63/840 objectives perfectly. Most interestingly the Baader/Zeiss M68 extension tubes also fit perfectly inside this tube, so that with a few such tubes, a readily available adapter and a few other off the shelf items, I can build a C63/840 with true 2" focuser.

I can already use 2" eyepieces on my Zeiss Telemator, but it does vignette a bit. The extremely fine focus of a 2" crayford with microfocuser would also be most welcome at high magnifications. I sometimes use 380x on my Telemator when studying planetary nebulae, so a superb focuser would not just be a rarely needed luxury, but a very useful item.

This idea has been ruminating at the back of my head since I found the aluminum tube, but perhaps I should see this project as a sign to do something about it.


Clear skies!
Thomas, Denmark

#54 jrbarnett

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Posted 09 April 2013 - 03:52 PM

Right on, Tim.

Sometimes you can find mass-produced R&P direct replacements for vintage 0.965" focusers too.

For example:

http://www.ebay.com/...ER-your-Eyep...

I'm using Anatres model FOCR2s on my three Cartons. I don't know if Antares offers these any longer, but of they do, they're actually a very smooth R&P unit. I think I paid about $29 each for these focusers.

Welcome aboard, matey!

- Jim

#55 Jim Romanski

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Posted 10 April 2013 - 09:39 AM

In fact, I would even accept a well-constructed argument that a considerably larger catadioptric (such as a 90mm MCT) was inefficient enough to deliver actual light grasp on par with a much smaller unobstructed scope. If folks want to come up with a calculation of equivalent unobstructed light grasp for small catadioptrics, I'd have no objection.


Hmmm...what if I let my AT72 get REALLY dirty so that it cuts down on light throughput? :throwveg:

#56 jrbarnett

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Posted 10 April 2013 - 02:19 PM

Works for me Jim. Or perhaps add an 85% transmission ND filter to the diagonal. :grin:

- Jim

#57 Gardner

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Posted 10 April 2013 - 06:40 PM

This looks like lots of fun! Last year at our Messier Marathon I paired my FS60 and C9.25 on my G11. Lots of stuff is beyond the limiting magnitude of myself and the FS60, but it was fun to try anyway.

Would it be possible to publish the list as an observing list downloadable to Sky Tools 3? The double star list looks intriguing. :)

#58 jrbarnett

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Posted 10 April 2013 - 10:12 PM

You bet, Gardner. I'm all Mac here at home, but tomorrow at work I'll fire up ST3 and upload the list in ST3 format to this thread.

Regards,

Jim

#59 Glen A W

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Posted 11 April 2013 - 08:51 AM

I've done a lot of those on the list, back when the 60mm was all I had. Hey, I figured it was a perfectly good galaxy telescope at the time. And, it's amazing how much I saw. I am not sure I would want to go back to one, though. I just don't get that much enjoyment from it, now. Glen

#60 Chuck Hards

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Posted 11 April 2013 - 09:08 AM

I'm using Anatres model FOCR2s on my three Cartons. I don't know if Antares offers these any longer, but of they do, they're actually a very smooth R&P unit. I think I paid about $29 each for these focusers.


It's a terrific focuser for a small refractor. I bought 5 of them some years ago, down to just two left that aren't dedicated to a project or already in use. IIRC, they had two models, one with a short drawtube, one with a long one. I grabbed the long ones. If anyone knows if they are still available, I'd sure appreciate hearing about it.

#61 jrbarnett

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Posted 11 April 2013 - 03:00 PM

Yep, Chuck, the FOCR2s have the 150mm long drawtube barrel and the FOCR1s had a shorter drawtube barrel. I wish I'd picked up a couple more when I was buying them, too. The quality was decent for the price, and they work well as direct bolt-on replacements for most 60mm vintage achromats. Which reminds me, I may swap one onto the Sears scope pictured in the article to see how this focuser works with a 900mm focal length scope.

Regards,

Jim

#62 Chuck Hards

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Posted 11 April 2013 - 03:18 PM

I lathe-turned one down for the 50mm f/20 scope I'm using for this project, to fit 2" OD aluminum tubing. There was just enough material left to tap some threads in the casting.
Then I got fancy, and installed a pair of those "mag wheel" knobs that Orion used to sell.

It's like pimping a Geo Metro.

#63 jrbarnett

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Posted 11 April 2013 - 05:58 PM

Hi Gardner.

I was just kicking around in ST3. It will allow me to export the file in either simple text format or Sky Safari format. Do you want either of those formats, or is there another way for me to export list files from ST3?

Let me know.

Regards,

Jim

#64 Gardner

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Posted 11 April 2013 - 06:30 PM

Jim,

I think text is fine. It looks like ST3 can create an observing list from text, but I've never done it. I'll talk to my local ST3 users and see what they have to say about it.

Thanks again for this cool idea and list. I like visual challenges! :jump:

#65 jrbarnett

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Posted 11 April 2013 - 10:07 PM

Okay, I'll post the simple text version tomorrow and you can give it a try.

I think next year, after this project is concluded, I'll do something similar with the ubiquitous C8. :grin:

Regards,

Jim

#66 buddyjesus

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Posted 12 April 2013 - 12:20 AM

that list might get a bit too long!

#67 Gardner

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Posted 12 April 2013 - 12:19 PM

Jim,

I talked to a friend who is much more fluent in ST3 than I am. He provided detailed instructions on how to share lists in the format ST3 can export and import. With his permission, I'm sharing his pics and instructions here.

It is really easy. Here are some screen shots.


Click Data
Click Share Lists
Click the list you want to share
Click Share


You will get a window prompting you on where to save the STX. From there, just email or post. Others can then down and import into Skytools.

Attached Files



#68 Gardner

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Posted 12 April 2013 - 12:22 PM

pt. 2

To Import.


[i]Click Data
Click Import Shared Data Tab
Click Browse local/network files
Click Browse to navigate to the location of the STX file
Click Import


Attached Files



#69 Gardner

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Posted 12 April 2013 - 12:29 PM

One thing I would add is that you need to click on the file you want to import (it will then highlight) before you click Import.

This process worked for me. I shared the AL Double Star to my desktop, then deleted it from ST3. I then imported it back from the desktop and it was like it never left.

#70 jrbarnett

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Posted 12 April 2013 - 01:51 PM

Gracias!

:grin:

- Jim

#71 jrbarnett

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Posted 12 April 2013 - 02:39 PM

Gardner unfortunately CN doesn't let me upload the ST3 ".stx" format files. :( There is a notice that pops up warning that .stx is not one of the permitted attachment formats.

PM me your e-mail address and I'll e-mail you the list in .stx format.

Regards,

Jim

#72 Vesper818

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Posted 12 April 2013 - 02:59 PM

Ok! Ok! I'm in!
We've finally cleared out and have some gorgeous clear weather! And now a really serious project to work on too!
Thomas I am going to print up yours and Jim's lists and put them all in a binder to work on.
I'll bring the pink Swift 60mm f9 and a Towa 60 F6.7 on Saturday night to Fisher Lane in Sonoma. Jim, please pm me with the address again so we get there before dark! My computer's on the fritz and I don't have your email ...
Clear skies and apple pies!
lc Carol

#73 DOTrevino

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Posted 12 April 2013 - 03:06 PM

perhaps my nominal vixen 70 is really 69.99 mm in aperture :-) and therefore qualifies for the challenge

#74 desertstars

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Posted 12 April 2013 - 06:25 PM

I haven't been logging on to CN as much as once was the case. An understatement - but the day job crowds the writing time, leaving not much left over for passtimes. Thought I'd take a look at this when the 60mm folks on Yahoo started talking about it.

Interesting list, interesting concept, and about darned time, if you ask me.

My approach would reflect how I organize observing projects in general, a divide and conquer principle that sorts objects between dark skies and suburban conditions. By way of example, I work double star lists at home, and hunt for galaxies and various nebulae from dark sky locations in the desert. Star clusters are a grey area; some show up well from my Tucson home, others need a bit of darkness to help them. I try things at home, and shift objects from one list to the other as needed.

"Year long"? More like "year 'round," for me. That time crunch business again. We'll see how it goes. ;)

The Old Scope has been idle of late. I believe that's about to change...

#75 jrbarnett

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Posted 12 April 2013 - 08:38 PM

If it's a little dirty, or you put a skylight filter in the diagonal to attenuate the throughput by 2% or so, you should be in like Flynn. :grin:

- Jim






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