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Post by jimcurry on Jul 3, 2011 6:59:37 GMT -5
Moments ago I placed an order for a 6" f/12 lens. I'll be building an OTA over the next month or so.
I chose the f/12 ratio to achieve some degree of compactness with the scope. I'm moving away from the "green" skies of Maine to the white skies of a major midwest city for a few years and I want to house this in a reasonably sized observatory. I'm thinking a 10'er will work. I'm assuming my observing will be restricted to dbl. stars, lunar and planetary. Galaxy hunting will be restricted to one hour drives into the country vs. stepping out into the front yard. I've got all major materials on order and I'm machining up the dew shield ring as we speak. With my experience with the 4" build and a little time on my hands I'm hoping to pull this off in a month or so.
There are 3 major parts to machine, the dew shield ring (this is what I call the most skyward ring I put on the dew shield to reinforce that end a little), the lens countercell and the backplate. I'll be using an AP 2.7" R&P focuser for which I'll machine a 2 piece rotatable backplate. I haven't laid out the light path yet but I think I'll put 4-5 baffles in the tube. I'll cut them from aluminum and use wood dowel spacers.
When I get some photos I'll document the build here on the Iclub site.
Jim
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Post by Watcher3 on Jul 3, 2011 8:04:14 GMT -5
Great news Jim! Sounds like another quality build is on the way. Sorry that your observing conditions are in for a downgrade, but I think you have made a good choice to make the best of it.
If you haven't seen it yet, Neil English did a review of the F/10 version in Astronomy Technology Today, that compared it to a Meade 5" F/9 Apo. Even the F/10 Looks like it would be no slouch for your purposes. F/12 should be pretty sweet. Keep us informed.
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Post by plyscope on Jul 3, 2011 18:09:53 GMT -5
Thats good news Jim. Looking forward to your building progress reports.  Andy |
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Post by Mike on Jul 3, 2011 20:53:37 GMT -5
Joe, actually Neal's review is in Astronomy Now. It's a so so review. I don't really understand the whole comparison with the APO. There are a couple erroneous statements about aberration that are also puzzling. I have to look at the review again but I think it was concerning spherochromatism. This "condition" is inherent to a degree in any achromatic design. Our master optician is scratching his head on this one wondering why Neil made it an issue. I have a copy of the review in PDF format. I guess I could upload it to my personal web site and then create a link on a post if anyone wants to read it.
Mike
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Post by Watcher3 on Jul 3, 2011 23:12:30 GMT -5
Sorry. Wrong magazine. I don't subscribe to either, and just sent for a copy when I heard about the review.
I came away with a more positive impression of the review. Don't have it in front of me, but I thought he at least alluded to the fact that the spherochromatisism was typical in an achro , and did say it was very good for this type of lens. I was a little puzzled about the "touch of astigmatism" he reported, without really quantifying it. You're right though, it's kind of bizarre that he muddied things up by throwing a 5" Apo into the review. The observation reports did confirm that it was a very capable scope. It did better than the Apo where it should have, and not as well where the Apo under any circumstances should have been better. The whole comparison thing perhaps make the ISTAR appear to be a little "less good" than it is.
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Post by Mike on Jul 4, 2011 14:05:01 GMT -5
I agree the review does have more good than bad. It's just when you leave it you don't know whether you feel good about buying the scope or bad about it's short comings.
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Post by jimcurry on Jul 5, 2011 6:05:23 GMT -5
Mike:
>Well, at least it gave the ambulance chaser on CN some ammunition. <
Which thread was that?
If you have a pdf of the article I'd like to read it.
Jim
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Post by Mike on Jul 5, 2011 20:11:07 GMT -5
I decided to post the Perseus 150-10 review under "General Discussion" so more people will find it.
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Post by jimcurry on Jul 18, 2011 6:25:03 GMT -5
It's here.....extremely well packaged. Attachments:
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Post by jimcurry on Jul 18, 2011 6:35:06 GMT -5
Gathering materials... Attachments:
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Post by jimcurry on Jul 18, 2011 6:36:47 GMT -5
Day 1. Machining the focuser rotating ring. I'm only putting in 2-4 hrs. of work on this per day. I've got some evening spare time while the cat is away so...... Attachments:
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Post by jimcurry on Jul 18, 2011 6:48:07 GMT -5
Day 2, the ring is done. The 24tpi threads are cut and it fit the focuser first time. Jim Attachments:
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Post by borispider on Jul 18, 2011 7:40:53 GMT -5
Nice work there Jim
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Post by Watcher3 on Jul 18, 2011 18:52:09 GMT -5
What I wouldn't give for a lathe,,,, or even the room to put one! Very nice Jim. Looking forward to your daily progress. By the way, What kind of lathe do you use?
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Post by jimcurry on Jul 18, 2011 19:04:22 GMT -5
Thanks, Boris.
Watcher, I have a South Bend 10". It's a lathe I picked up last year, stripped it down to its basic components, rebuilt it and painted it. It looks VERY new but it's actually 40 years old or so. Unfortunately, I can't build an 8.5" scope on it. An 8.5" requires a 10" tube with an 11" dewshield, too big. I think those parts would be too big to swing. I'm working with 7" and 8" diameter parts now and it's taxing the lathe a little. Could just be my non-machining skills.
Jim
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