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Topics - Jim Snyder

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I'm an almost exclusively visual observer, who occasionally throws my wife's DSLR in the mix for some quick (~30s) unguided shots, mostly just for fun, but also to bring out details in the faint fuzzies that I don't have enough aperture to see with my own eyes. My current EQ mount is the Orion-branded Synta EQ-3 (i.e. Orion AstroView). I used to hate it, thinking that the 150mm f/5 it came with was woefully undermounted (huge vibrations that take too long to dampen), but once I added the dual-axis motor kit (I got the Celestron version off of Craiglist; probably would have bought the Celestron version new since it's a little cheaper than the Orion one) my perspective on the mount totally changed. It still takes just as long for the vibrations to dampen, but once they do, whatever you're looking at stays dead center in the FOV for as long as you care to look at it. I am now a big fan of the mount, as it's relatively portable and offers decent performance for what I do. The one thing that really bugs me about it is that the RA axis has no clutch, so it isn't an easy matter to switch it to fully manual operation if for some reason I wish to do so.

Call me a luddite, but I don't like the idea of needing power in order to observe. I have no qualms with taking advantage of it when available, but I don't want it to be an absolute prerequisite. Batteries can run down, break, or neglectfully uncharged; any number of things can go wrong with motors and their control systems; I just like the idea of being able to easily fall back to manual. Even when everything is working, I like the idea of being able to center with the manual slo-mo controls, then tighten the clutch and let the RA motor track, and just letting the hand controller sit on the accessory tray and not having any reason to need to pick it up and fiddle with it.

I'm not actively in the market to upgrade my mount, but I know I will eventually, and like to sort of idly think about it from time to time. The obvious upgrade would be one of the many clones of the Vixen GP (or a used Vixen GP, since the Vixen AP just doesn't do it for me), all of which could be fitted with a dual-axis drive system with clutches to allow easy switching to manual slo-mo on *both* axes. But I'd like to know if there are any other decent options out there for manual-capable mounts. It sure doesn't seem like it. I'm guessing that the glut of inexpensive and reasonably capable EQ-5 type mounts makes it difficult for anybody else to justify making engineering the ability to use a mount with fully manual controls for the few of us who want that capability.

The EQ-5 type mounts that I have been able to identify so far are:

Astrozap AZ-3000 (it took me forever to realize "AZ" probably refers to "AstroZap" and not "AZimuth")
Bresser / Explore Scientific EXOS-2
Celestron CG-5 (no longer produced)
Meade LX70
Meade LXD-75 (no longer produced)
Orion SkyView Pro
Sywatcher EQ-5

And of course the original: Vixen Great Polaris and derivatives (no longer produced)

IIUC, these are all based on the Vixen GP design, and should all be reasonably compatible as far as motor options are concerned. They all look completely identical apart from color, with the exception of the SVP, which has more sculpted lines and has the setting circles in a different location. I believe some are made by Synta and some by Jinghua?

Anyway, I guess my actual questions are:

* I'm assuming not all of the above options are created equal, despite looking pretty much identical. For example, even though I've never actually used a Celestron CG-4, I sort of assume that despite it being pretty much identical to my Orion AstroView, the CG-4 would be slightly better just due to the fact that it comes with a more substantial tripod. Also, I hear the original Vixen mounts were made to tighter tolerances than their clones ever were, and I imagine there might be some variability between the currently produced clones as well. Do any of these mounts clearly stand out from their peers?
* I'm assuming I've missed some other, let's call them "GP compatibles". Have I? Which?
* I'm hoping that the "GP compatibles" aren't truly the only option for mounts that are both dual-axis and manual capable, where switching between the two doesn't require a screwdriver. Please tell me there's other possibilities. I'm intrigued by the Losmandy GM-8 and G-11 design, which as I understand uses friction clutches that let you just repoint by hand, but having never actually seen one, I don't have a good idea as to whether it's sensitive and smooth enough to be acceptable for fully manual use when the occasion calls for it. (I would sort of imagine tracking manually by just gently nudging the counterweight shaft to move in RA without moving in DEC, but worry that it would be hard to nudge gently enough to avoid overshooting at high power.) Any thoughts on other EQ mounts that can easily switch between motorized and manual control?

I have a 10in f4.66 that will be converted to a dob, and the new carbon fibre 10in f4 will be used as my main deep sky imaging scope and I will also use it viewing rich fields.I do have some coma correctors ,>> the old Lumicon CCFF is attached to my 48mm Lumicon EzyGuider>> a Baader MFCC>> a Tele Vue 2" tuneable top Paracorr ... a recent acquisition>> also have a 2in Tele Vue 2x PowerMate .... a recent acquisitionI'm thinking either Vixen SSW eyepieces (5mm, 10mm, 14mm these are all 1.25in) and maybe NLVW 30mm (2in)orPentax SMC in similar fls 5mm to 15mm as 1.25in eyepieces.I don't mind spending to get very good quality in my eyepieces which will have to do me out , it's taken me years to get to this point.I will likely want to try eyepiece projection once the scope and ROR observatory is installed.Til now my best eyepieces have been RKEs, these may be OK using the Paracorr on the f4.66 dob but I have my doubts about using these even with the Paracorr on the f4.Comments on my eyepiece choices for the f4 Newtonian would be greatly appreciated.

I could use some advice on the scope/mount connection. Bisque recommends rings, so I tried Parallax rings for my C11 but find that I can't position the OTA forward enough to get dec balance without loads of extra counterweights and/or custom machine work. (The versaplate, rings, and OTA are as far forward as they'll go.) If you're using an SCT on this mount, I'd really appreciate hearing how you connect it. Pictures would be great. Thanks.


ATM, Optics and DIY Forum / Interferometer isolation techniques
« on: December 27, 2017, 10:55:26 AM »
I really like what LIGO is using, a suspended multi-part pendulum. See

and the explanation

One wonders how closely the masses have to match, it could be used, possibly, to suspend an entire interferometer, optical bench and all, under a couple of sturdy overhead beams.

Light Pollution Topics / Estimating light pollution at a new site
« on: December 24, 2017, 08:23:59 AM »
The following two nights I will attempt to estimate the light pollution at a potential observing site.  I really don't have the experience to simply look up and say something meaningful.  The place is close Ranger, TX.  Astronomical twilight is about 4:30 a.m. and 8:30 p.m on Aug 17 and 18. Moonrise is roughly 7 and 6 a.m., and moonset is at 7:05 and 7:45 p.m. on Aug 17 and 18.  So moonlight is not an issue.I strategy on photographing the horizon in all directions at 9 pm, 10 pm, 11 pm, and midnight each night, clouds permitting.  I am hoping to locate two places near each other, one having a clear view of the horizon, and also one more enjoy an observing field with trees enclosing it.I hope to see evident strong light pollution out of D/FW covering ESE through NE.  I hope to see the lights of Abilene into the west, so much weaker.  Other than that, I hope it is not too bad.I have a Canon 40D and also intend to use a 17-55 2.8 lens on a tripod.  I am unsure what exposure settings are most helpful.  That is the sole objective instrument I've at hand.I will also do some standard naked eye observations, but my eyes aren't so good, and not calibrated against anyone else's.  Advice most welcome about how to get data which may be shared at a purposeful way.Lee

Yesterday evening I got out with my 50mm f/10 Galileoscope.  It had been used with an inexpensive 17mm Plossl eyepiece providing a magnification of 30x and a genuine field of view of roughly 1.85 degrees.  The telescope has been used without a star diagonal on an inexpensive camera tripod.  My avatar shows the telescope and tripod that has been utilized.

Observations and Notes:

M51 -- around, diffuse patch of light with a comparatively large, somewhat brighter center.
NGC 5195 -- smaller companion of M51, seemed to be only barely in contact with the outside 'halo' of M51.

M101 -- big, round, diffuse patch of light of uniform brightness - without central heating.

M33 -- big, fat, elliptical, diffuse patch of light with a slowly, little brighter, center.

M31 M32 & M110 -- Wonderful!  M31 was a really large (bigger than the scope's FOV) highly elliptical diffuse glow, very slowly - then much more abruptly much brighter middle.  M32 was a little, bright, somewhat 'fuzzy', around companion.  M110 was a little more distant companion, significantly bigger than M32, elliptical, of uniform brightness

M97 & M108 -- (Note: these two objects were in an altitude of just 16.5 degrees in the time of the observation).  M97 (the "Owl Nebula") was a small, round, diffuse patch of light.  M108 was a fainter, elongated, diffuse patch of light.

Mizar -- has been a beautifully split double celebrity.  Colors were subtle.  The primary appeared to really have a slight yellow tint.  The secondary appeared to really have a slight greenish tint.

Cor Caroli -- (Note: thing was at an altitude of just 11 degrees in the time of the observation).  This dual was readily split, but colours were unsure due to the very low altitude.  Finest guess is white for the two, but atmospheric effects sometimes said differently.

Perseus Double Cluster -- Nice set of open star clusters, easily fitting within the FOV.

M13 -- Large, quite bright, round, gradually brighter middle; appeared to present a marginally 'mottled' appearance - perhaps hinting at this globular's true nature.

M92 -- Like M13 only smaller, less bright, and without any suspected mottling.

M57 -- Small, but very nice!  Even at 30x that the ring-shape was obvious.  It looked like a tiny, fairly bright, bagel in the sky!

Albireo -- Wonderful!  Broad, bright double star.  Yellow-orange primary, blue secondary.

It was a pleasant and fun session.  M31 would have profited from a 24mm wide-field eyepiece.  M57 would have profited from magnification.  But I wanted to keep things somewhat crude and easy.  As it was, I had Galileo's scopes greatly out-classed.

M31 & family was the highlight!  I can't envision what Galileo would have thought if he would have seen such a sight!

Yes, a little 50mm 30x telescope might be enjoyable to use and may show lots of interesting sights in the night sky -- and not just show them but really show them nicely!

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