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Messages - Adam Rice

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1
ATM, Optics and DIY Forum / Re: String Telescopes
« on: February 02, 2018, 08:28:46 PM »
Mark

thank you for the link. Very interesting. Its extremely well thought through and superbly illustrated web site so definitely worth a closer look. Don is obviously an engineering purist. But I'm immediately struck by his tensegrity design and his arguments around it; Don directly addresses the issues I raised with respect to the relationship between tension/mass/flexure, so I've no doubt his design would work very effectively. But of course...note the example in this link, it has six members in compression plus the strings. Why not stick with a six member truss?
Here is the real minimalist telescope,although as he concludes the 4 pole design is more practical.
I'm not disputing that these designs will work. I think they are excellent fun.
What I don't see is any evidence or reason why either of these designs are more efficient than a similarly well executed 6 pole truss. Despite the improvements that reduce tension, these designs are still working against greater forces than a simple six pole truss, and they have more components. What I see is added complexity.
I will concede that as professional telescope engineers push the boundaries they have moved to more complex trusses, obviously in an effort to reduce mass, such as Gemini here. So its true that added complexity can reduce mass while maintaining adequate stiffness.
But I still don't see strings.
OK, granted the MacDonald 82 uses thin crossbars in tension so yes OK a string design. So such things exist and on that technicality I stand corrected. But that only amplifies the point; if it worked, if it was a great solution, why don't we see more? Why don't the newer larger lighter telescopes that push the engineering envelope use strings if strings offer a stiffer solution for a given mass? I still think the answer is because they don't, and all the arguments on Don's website only serve to illustrate why.

2
Reflectors Telescopes Forum / Re: Elliptical secondary mirror cover?
« on: January 31, 2018, 12:29:05 PM »
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One prominent forum member here had his secondary damaged by a plastic bag in a windstorm.

That was quite a wind storm. The wind blew 40-50mph for a day and half...  About a day and a quarter into it, I thought about the plastic bag over the secondary, I went to look, it did not look good.

Regardless of how it looked, once the wind died down, the views were excellent.

When I took the secondary to Terry Ostahowski for a recoat, he gave it the tape test, the coating just pealed right off. In that wind, anything would damaged that coating.. The safest thing to do would have been to bring the scope inside or at least remove the secondary. I still use a plastic bag but I am more careful about the wind.

Around here, dust is the issue, I don't worry about moisture.

Jon


3
I observe in the midwest (Minnesota) and we have heavy dew at my favorite site. When it's cold enough, we get frost all over our scopes....... I made dew heater bands out of nichrome wire bought at a surplus store, a bit of textile ingenuity and some old speaker wires with RCA plugs. I bought a 4-channel controller from a guy in my astronomy club who sold it cheap because it caused electrical interference with his astrophotography somehow. And I bought a 12-v power supply at Harbor Freight. I use 4 bands on my 10" dob - on the objective and eyesight of my finderscope, on my reflex finder, and on my finder eyepiece. I left the wires long enough that I can set the finder ep aside, band still attached and then use a higher magnification ep, without unwiring everything. Since the higher-mag ep is only used temporarily, it doesn't dew up. The whole set-up looks messy but works great - and I could clean it up if I ever felt it necessary. I do have several fuses in the electrical chain, just in case. I still want to improve on the battery life - I would like enough juice to observe for every night for a week (at a star party) without any external power supplied. Solar recharger may be part of the answer. I also have a 120-v to 12vdc power supply that I can use when electricity is available.

4
Beginners Forum / Re: ONE filter
« on: January 31, 2018, 11:28:04 AM »
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Morning Alice, if you do get a 2" diagonal but it is an SCT specific, in other words secures to the back of the scope without the use of a visual back adapter then the filter would have to secure to the barrel of the eyepiece, this isn't a down side because most likely you'll only be using 1 or maybe 2 low magnification 2" eyepieces when using the filter for DSO hunting.
I think you're searching for an end to the decision between the 1.25" and 2" star diagonal, let me help, get the 2" sct specific, it will be the most versatile diagonal for the 8" Edge, I know I stated otherwise in previous post's but I was making that decision based on my scope which is older and the ota is fixed to the base, I believe the Edge ota can be adjusted fore & aft on a rail for balancing & base clearance.
I just tested my 2" sct GSO dielectric diagonal adapter to see if a 1.25" 32mm TV plossel would strike the 2" filter in the adapter, it didn't touch the filter, it was close, but it didn't touch, so the 2" diagonal can be used with the same 2" filter for use with 1.25" 32mm to 40mm plossels, always check the barrel length of any of these to make sure it won't touch the filter when you're swapping around eyepieces at night. I used a very inexpensive color 2" filter for this test btw.

 LOL Mike, the diagonal is already on order, I was planning to test it out and return it if need be.  The lure of the wider field EPs was too great for me, plus I really like the versatility aspect.  Yes, the OTA will slide back-and-forth on the mount. I will balance it carefully.  I can’t remember which one got ordered at the moment, I am away from home, but it is SCT specific.  I’m glad you reconsidered your advice, that definitely relieves me about this purchase.

5
ATM, Optics and DIY Forum / Re: Focuser rotator for newt?
« on: January 31, 2018, 09:06:26 AM »
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I did a bit more work on my rotator last night. I anodised the two main parts, just one more bit to go and I think I'll do it blue. This was my first time anodising anything and it turned out really nice.

IMG_4210.JPG

IMG_4211.JPG

IMG_4212.JPG

This looks great !
cheers
Gary

6
General Astronomy & Observing / Re: And I'm Goin' to Arizona . . .
« on: January 31, 2018, 01:48:37 AM »
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I've been looking at the Big Bend area of Texas and may be headed there for a scoping trip this month or next, 60 deg or so in the day and 40's and 30's at night. Arizona's tempting, even better 70's daytime and 50's at night.
I don't know if it's possible to find a place with a pleasant climate all year long. Southern Texas, New Mexico and Arizona are fine during the winter but the summers are brutally hot. There's a reason snow birds do what they do. They may have the best solution.
It depends on the altitude. Flagstaff is ok. I needed a jacket on during summer night there. And just across the border in Gallup, NM it was cool enough in July you could see your breath in the morning. I wasn't thinking of going to either place, Texas or Arizona, during the summer, just possible trips in winter, fall,or spring.

7
Am I the only one who thinks fully illuminating center of the field of a commercial 300mm F/5 telescope with a 35mm secondary is not possible?

Every other post I read seems to be acting on the assumption that it is possible..
Jon

8
ATM, Optics and DIY Forum / Re: Figuring, Warm Press
« on: January 31, 2018, 12:42:30 AM »
Gee guys Im not trying to say Im a master mirror maker here, Im just sharing my expericances, and looking for feedback. I have a little confidence in my testing because I have a Zambuto 8" to play with, I have tested that a few times at 1/15th- 1/16 wave, Seems like thats probably about right? Also did a series of Ronchis on a 12" that performs pretty well and they matched up well with expectations.
How does a guy make a mirror then if you cant belive your tests at all?I'm not going to believe my "best" test, rather my worst.First youhear "anyone can do it, its not that hard", then "you cant believe your tests".I dont think my tester is a complete pile, its a dual micrometer X-Y stage with a .0001" digital dial indicator. Sorry if I came off like I was bragging, Ive been busting my butt for months and it seems like I'm finally getting somewhere. Is there a reasonably priced way to get this tested, when I think I have it done? Sorry if I sound like I'm crying but you kinda busted my bubble.......maybe that's what I need

9
General Astronomy & Observing / Re: How do you approach a farmer
« on: January 31, 2018, 12:39:21 AM »
Try FarmersOnly.com....all the babes are smoking hot!

Just kidding...

Perhaps you can offer to set up a scope for them one evening and do a little star party. A "picture" of Saturn is worth a thousand words...

10
I passed through Flagstaff as a teenager in 1974. OK, I was almost 20. Anyway is was January and there was lots of snow on the ground. I remember it being a nice town then.

My financials will play a big part in my retirement living arrangements. A small place with a bed and a place for the telescope will be about it! Seriously, I will have to be prudent in how much I can afford.

11
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Looking to get a little better diagonal than the amici prism diag that came with my meade refractor, whats the difference in these two? Seems the dielectric mirror is more money..

thanks

By now you've prolly made your choice but so's you know- I bought a NIB Orion 2" dielectric for $89 delivered, on Ebay. Haven't seen one since, but they can be had for less than list if you look. I love mine!

12
Inside the cage:

Filter slide has an open position without filter then two spots for an O3 and a UHC filter. Though you could put in any filters you want.

The four fender washers have felt under them and keep the filter slide in position. A spring loaded click stop allows for accurate positioning between filters.

Can't wait to give it a try!
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13
Mounts Questions & Expirience / Re: Time to Upgrade
« on: January 28, 2018, 10:36:28 PM »
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When I install the IEQ45 drivers in ASCOM I just get basic controls, it doesn't tell me RA and DEc or anything like most mounts in ASCOM do.
I've heard the G11 wasn't all that great for Astrophotography but I've never personally tested it out. I've heard about the Celestron CGX and it looks very nice. Quality looks pretty good too but it's very new.

The G11 Is showing its age looks wise. No through mount cabling and the motors look like after thoughts, but to each their own. You can do a lot of tweaking to it if your that way inclined.
The CGX has potential but I'd wait a while for early adopter glitches to get solved.

14
ATM, Optics and DIY Forum / Re: Book Recommendations
« on: January 26, 2018, 08:33:36 AM »
I have both books that have been recommended and they are fantastic. You might need other resources when it comes to mirror grinding should you do that in the future but until then, these are perfect. Only if you choose to do a string telescope could I suggest another. You will be well covered with these.

Frank

15
Reflectors Telescopes Forum / Re: Moonlite + Paracorr type 2 vs SIPS
« on: January 26, 2018, 05:57:52 AM »
My take:

It does essentially parafocalize all your eyepieces but the adjustment of the Paracorr is not as precise as the focuser so some slight refocusing is required. Truly parafocalizing eyepieces at F/3.5, not really possible..

Jon

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