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Topics - James Gruber

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Does anyone know what's going on in the ortho market? Clicking on University Optics' website brings up the message: "Thank you for visiting, but this web site has been closed down at the request of its owner."

Going to Agena's website shows that AstroHutech orthos and Kasai Trading Co.'s eyepieces are on closeout - all sales final, no returns accepted.

My understanding is that basically all of these orthos and other Japanese eyepieces are all made in the same factory in Japan. Is it possible that there's something going on at that factory? Are orthos done? Does anyone know what's going on here?

ATM, Optics and DIY Forum / A SOLID 30 mm F/10 Schmidt Cassegrain
« on: December 29, 2017, 01:43:02 AM »
About fifteen years ago I wanted to make a very small Schmidt-Cassegrain out of one solid piece of BK7, just to see if it could be done. So it became a 30 mm F/10 instrument, just small enough to fit ín an eyepiece! Thought it would be nice to share here...Here's what I did:I drilled a cylinder of 30 mm diameter and made one end convex spherical (the primary mirror) and the other end flat (the corrector side). In this side a small concave sphere was made, being the secondary mirror. I calculated the needed aphericity of the Schmidt-corrector (21 microns!),ground and polished this deformation into the surface and made corrections using flexible polishing tools. In the middle of the spherical primary I made a concave sphere to bring the focus far enough outside the 'telescope' to be used in combination with a CCD or eyepiece. To prevent straylight I drilled cylinders around the secondary and into the primary mirror acting as light baffles. Then the mirrors were coated with aluminum. Although it was meant to be used ínside an eyepiece I never actually made a barrel where it could fit in. However, I have made two larger ones, with 40 mm diameter and I kept this little one as a nice memory.... Unfortunately I have no pics of these large ones.The pictures below show you the size compared with an 1 1/4 inch eyepiece and I did some Photoshop to give you a realistic idea of what it would have looked like ;-)Thanks for watching!CheersRik

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Mounts Questions & Expirience / Advice on Mount Upgrade
« on: December 27, 2017, 10:10:25 PM »
For the last six months I have been imaging with a SkyWatcher EQ-6 (same mount as Atlas EQ-G) with both a Nikon 600mm f/4 lens and a Meade 2120 SCT.  I am very pleased with the EQ-G when using the 600mm lens. With the ~20lb load of the lens and an Orion 60mm guide scope, I can guide with an RMS error of less than 1 arc-sec if I do a good polar alignment and carefully balance the mount. (Oddly I usually get better than 0.5 arc-sec in Dec and about 0.8 arc-sec in RA). At 600mm the ASI 1600 has 1.34 arc-sec pixels, so I get pretty crisp pixels.

However, the EQ-G is not up to the Meade 2120 - or I suspect any long focal length OTA. First, the 2120 is itself 32lbs, and with a guide scope and camera I'm right at the 40lb limit of the mount.  Even with a perfect polar alignment (no Dec pulses observed) and careful balancing, I can't get an RMS guiding error less than 2 arc-sec.  The 2120 - with a focal reducer - has a focal length of 1600mm - giving about 0.5 arc-sec pixels with the ASI-1600, so my guding error smears four pixels together.

What is the collective wisdom of this board on a suitable mount for a 10" SCT - and perhaps eventually a 12" RC? And what type of guiding error should I expect to achieve? Instead of upgrading the mount should I add AO to compensate?

I have been looking at the Losmandy G11GT as a likely upgrade candidate. With a 75lb rated load it should easily handle a 10" SCT or 12" RC with camera and guide scope. It claims a +/- 5 arc-sec periodic error, so unless it happens very unevenly I should be able to get down under 1 arc-sec in RA with a combination of PEC and guiding. What do people with this mount achieve in practice?

Does anyone have any experience with the Orion HDX-110? With the SynScan Goto system this has to be the Synta SkyWatcher EQ-8 mount. Is it like the EQ-6 but with a 110lb rated load? It claims +/- 3 arc-sec error before PEC.

The other options - from Software Bisque and AP - are *much* more expensive. What does one get for the added dollars?

Anyone use their SkyQuesr without attaching the Correct Tension spring?

Does it work? Does the scope stay balanced?

I'd move the scope in two parts and rather not putter with attaching the springs, especially in colder, frost-bite inducing weather!


I have a Baader T2 Zeiss Prism which has an aperture of 34mm. (The famous Baader Planetarium 7-Layer Multi-Coatings ensure the image is bright and contrast and the oversized prism provides an oversized full clear aperture of 34mm / 1.34").Baader T-2 90° Prism Star Diagonal Body with Carl Zeiss Prism # T2-01B

The field stop of a 26mm Nagler T5 is 35mm, weights 1.6lbs and will provide a TFOV of0.99 degrees and1.4 degrees if I ever manage to extend my ADM Dovetail to fit an Edge Focal reducer which is 51mm long without counting the threadings. I currently have 40mm of space left between my diagonal and Nexstar 6/8 SE mount sitting on a sturdier Evo 8 Tripod but am planning to extend the dovetail, I believe ADM has a solution for this fix...anyhow back to the topic.

The 31mm Nagler has a field stop of 42mm which is the same as an Edge 8's field stop but much larger than my current diagonal. It weights 2.2 lbs and is also 1 inch longer than the 26mm for measuement sakes. (5.4 to 4.5"). It will show a TFOV of 1.2 degrees and 1.7 degrees if ever used with an edge focal reducer.

These, and either a 20mm or 22mm Nagler are the only 2-3" eyepieces I'm interested in. If I were truly able to use the 26mm Nagler in my current diagonal mentioned above, would'nt be wise to just get the 26mm as to avoid having to buy a 2" diagonal, etc etc..or is the view from the 31mm really that much more worth it? I also binoview a lot, as much as monoviewing actually, so I'm also thinking about versatility/ease of use. Unless there is a good method to binoview with a 2" Baader clickstop diagonal...

If I've made any mistakes please correct me, thanks. Any advice appreciated.

ATM, Optics and DIY Forum / Relatively quiet power tools?
« on: December 24, 2017, 05:18:11 PM »
What power tools are there which won't bother the neighbors?
I consider a Crapsman drill push on low to be "quiet" and usable (700 rpm).  A Ryobi jigsaw on low will burn up the motor according to the manual so I use it on medium-high for wood.  It does a funny sonic boom effect that I do not hear ear protection, however I am sure my neighbors do.  I just cut metal with it when somebody is mowing the grass or snowblowing, or performing similar stuff.
Proxxon IBS/E (Dremel-like instrument) is quiet at 5000 rpm, but that's too low in contrast to recommended rpm for the burrs that I utilize.
A generic oscillating instrument in 12k oscillations sounds like a rocket and there's no rate controls.

CO2 lasers are out due to security reasons.  A plasma cutter will problably trip the circuit breaker...

Beginners Forum / "Shooting Star" question
« on: December 24, 2017, 01:09:32 AM »
How does one tell the difference between a bona fide meteor and space debris?

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