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Topics - grountentaybrig

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One radical option I had been poking once - the "lay along" mount. Which is basically a narrow bed with the scope mounted in parallel above it (eyepiece down) on a motorized Alt/Az mountwith ellipticalAlt rails. But might be too comfy to resist sleep all night...
Oooooohhh ! NICE.
For these cold winter nights, you crawl into a sleeping bag, just in case you do nod off.
No doubt someone will object to body-heat thermals; for that you cover the bag with a space blanket !
Last problem would be the people standing in line to try it out (Hey when do I get my turn !!! Is that snoring I hear in there ??! )

Seriously I like it, it solves all the issues of observing comfort I can think of, One heck of agiant leap past standing on a ladder
Not sure about portability, but you do have me thinking

Hey all, another newbie here,

I'm looking to add another barlow lens to my collection with the goal of getting the highest magnification feasable from my 8" f5 reflector when using an ES 82° 6.7. That's roughly 150x and I already have "shorty" type 2x barlow for a hearty 300x. I'd really like to get Jupiter and its moons as big as possible, pushing 50x-60x per aperature inch when conditions are good, or either a 2.5x (375x) or 3x (450x).

I bought the 2x (meade) when I bought the telescope without much knowledge about the mechanics of barlows or eyeieces because it was cheap and now that I'm purchasing nicer eyepieces I'd like to get the most out of them. It's actually nice enough and serves it's purpose, and there's 3x version I could pick up, but there are obviously many other options at various price points.

Would it be worth the additional cost to buy a better quality barlow? How do you determine the image quality of a barlow lens when looking at its specs? There are 2 element designs all the way up the 5 element designs, all those lens must serve some purpose. Also, would using a 2" lens with 1.25" eyepiece affect the image at all or would the end result be the same as a 1.25" lens?

What do you fine folks think would be best for me and my equipment? I'm not in much of hurry to make a purchase, since there haven't been many clear nights lately, so I could hunt for used ones for awhile if that's best.

So , now that we've covered what one thinks the smallest big dob is, what's the largest one you've owned or had the chance to look through?
How did views compare to scopes in the 12-16" range?
How does performance compare between a dark site vs in light pollution? (And between large & small under those conditions?)

How did Galaxies,Globular clusters and nebulae views differ in those situations?
For instance, globs can take more light pollution than nebulae,etc.

For me , Looking through my friend's 25" F5 Obsession was quite the treat at a dark site in the Adirondacks. Globulars definitely resolved more stars, and Galaxies more spiral structure than my 12" and 14" or the AAR 16". Averted vision was less necessary than on my 12" on the brighter DSO's for sure, but still helped.
However when we looked at Comet Jacques, the difference was less pronounced compared to my 12"...
Ive looked through Rob Teeter's 20" sub 4 ( bino view), globs were very big and bright.

M42 through s 20" Obsession at the Sterling mine was very impressive, but not much different than through the 12"....

Your thoughts?

Hey everyone,

So a couple days ago, I found my first ever DSO: M13. I haven't had my equipment for too long and haven't put much effort in DSOs so far, mainly due to the lack of a good finderscope/telrad (which I'm anxiously awaiting by the end of this week!), but now I'm hooked and will be looking for more!

90% of my viewing is from the backyard in a red zone, so not the best for DSOs, but I'll be extremely motivated to do the 45min drive to the nearest yellow/green zone more often.

Anyways, it was a pretty nice and rewarding feeling finding the faint M13 for the first time, and practicing averted vision, which brought up a bunch of little stars around the faint smudge of the cluster!

So that was using my Vixen 70mm refreactor and a 25mm Plossl.

I immediately thought, wow, if I can see this object with the 70mm, it will be much brighter with the 130mm reflector, so I quickly switched OTAs on the mount and finally spot M13 with the reflector....... hmm, pretty much the same faint smudge as with the 70mm...

So my question is, is it safe to assume that in a sky polluted area, larger apperture doesn't mean brighter objects that are pretty faint in the first place?
I guess the aperture difference will make a big difference in dark skies, but in a bad sky, will not help much if at all?

For what its worth, the refractor is a 70mm f/13 and the reflector a 130mm f/7, same eyepiece used on both.I'm leaving this Saturday morning for a 6 days/nights fishing trip in a "dark grey area" and the weather forecasts so far are looking very good.... I can't wait for doing some DSO observation in a real pitch black sky!!!!

Mounts Questions & Expirience / How big is an arcsecond?
« on: December 31, 2017, 03:13:54 AM »
Okay, so... this posting is born of an observation of other postings here. I think people might sometimes have a casual expectation of mount accuracy, in pointing or guiding or pole alignment, or other issues where the measurements are in arcseconds, which don't seem to take into account just how small an arcsecond actually is. We throw around numbers (and expectations!) for sub-arcsecond guiding and so on, but I think it's wise to keep in mind just how difficult that challenge is.

It is not my intent to stir up controversy, as oh-so-occasionally happens here on Cloudy Nights. My intention is to merely to remind us how small an arcsecond is, in the hopes that when we have problems to solve, we realize just how difficult they are, and perhaps readjust expectations for the amount of effort that's going to have to go into them, or of how to evaluate the results as bad or good.

So it's a sixtieth of a sixtieth of a degree, or 1/3600 of a degree.

One way to think about this is the movement or "width" itself, when we project that angle out across a lever arm or other distance. The tangent of (1/3600 degrees) gives the ratio of an arcsecond -- it establishes the relationship between the length of the "arm" or distance over which we're acting, and the amount of motion or the size across the end of that distance. So let's say we have a telescope that's a meter long, and 1000mm times the tangent (0.000004848) gives us a lateral motion of 0.0048mm per arc second. So if we want sub-arcsecond tracking, we need to be able to control the lateral motion of the telescope to less than 1/200 of a millimeter. So... get a knife, make two marks on a piece of wood that are 1mm apart, and then divide that space into 200 parts. If the telescope is pivoted in the middle on the mount, you get half that amount of motion at the front end, and the other half at the back end of the telescope -- 0.0024mm. Urgh!

At 100m away, an arcsecond represents a lateral size of 0.4848mm. Half a millimeter. I don't know about you, but that makes me think "Wow! And we can expect sub-arcsecond accuracy?"

From one side of my country to the other, let's say 3000 miles or 4828 km, the width of an arcsecond is about 23.4 meters.

Across the diameter of the earth, it's about 61.8 meters.

At the moon, it's about 1864 meters. (This is perhaps why you can't see the flag!)

Another perspective on it is rotationally,dealing with the angles directly, leading toward control of the mount's axes and such things. Pick up a protractor, angle guage, whatever you've got, and divide the degree marker into nearly four thousand parts. They're tiny.

The circle as a whole is divided into 1,296,000 arcseconds. They're tiny.

If your mount uses a shaft or other direct-reading encoder that didn't cost thousands of dollars, let's say the resolution is 1024 ticks per revolution of the mount. That's 1266 arcseconds per tick. That'll never do for anything precise. If the encoder has 10000 divisions per revolution and quadrature reading gives us 40000 ticks per revolution, that's 32 arcseconds per tick. Much better, but still not so great.

Now what we can do is put it further back in the gear train, on the motor before the motor is geared down. If we had a factor of a hundred gearing, for example, with 40000 tick encoders, we'd effectively get 4,000,000 ticks per revolution, which is a third of an arcsecond, so that would be pretty awesome, except that... well, the slop in gear train is probably much greater than that. And most encoders on motors are much lower resolution than that, say 64 pulses to what, I don't know, 512? With quadrature, we get to multiply that by four, so let's ballpark it and say we have 1024 ticks at the motor, 100x in the gear train, and that gives 12 arcsecond per tick. Hm. Let's bump up the gear ratio a bit more, and we'll be in the ballpark, but to get sub-arcseconds at a low-to-middle cost... that's going to be a challange.

My main point is that sometimes doing a little math can help define reasonable expectations, give a better sense of the difficulty of the problem at hand, help define "good" and "bad" in a particular context, and so on. We always want better, for sure, but... reality will always get in the way, and should always be considered.

Why did you choose an alt-azimuth mount rather than a equatorial mount? Are Equatorial mounts becoming obsolete? Thanks to you all.

Eyepieces Questions & Recommendations / Homemade Eyepieces
« on: December 29, 2017, 04:14:00 AM »
So I was looking online to try and see if I could find some guides as to how to design and make your own eyepieces. All the ones I found where very rough and cheap alternative eyepieces. Using pvc pipe and old film container style of DIY. Since I have access to a very good metal and wood shop I thought it could be fun to make my own high quality EP. Does anyone know of any books or articles that show you down to design different EPs and how to construct them? I was not very successful with my google searching, though it was only during lunch so I will search some more later after work. But thought I'd ask around and see of anyone knew of any. Thanks.

ATM, Optics and DIY Forum / Interpretation of Star Test
« on: December 29, 2017, 02:25:35 AM »

I've attempted to illustrate as closely as possible what I saw doing a star test on a 90mm, f/13.8 Mak.
I always get confused as to what means what, so maybe someone might give an opinion...

Here is the illustration:

[attachment=708797:star test 90mm Mak.jpg]From the little I know, It appears to be some king of over or under correction.

And, does the fact that a Mak has a 30% central obstruction mean that with a near perfect scope, the inside and outside focus patterns will not be exactly the same? Or in a near perfect scope they should be the same regardless of the CO?

The scope shows good images to over 150x in good seeing. And the in-focus Airy pattern is nicely formed.

Thanks for your time and opinions,


Has anyone solved my issue below? I've read all the forum posts on this issue, but haven't seen anything that seems it would fix this significant issue yet.

I just purchased a Sky-Watcher AZ-EQ5 mount to use in AZ mode with the new Stellarvue Access SV125, I figure around 20 lbs with finder and diagonal/eyepiece. Main reason for the mount choice is AZ capability and light weight that I'd be willing to put in my sedan without hurting my back. On paper it's the perfect choice. The AZ-EQ6 is just too heavy, I'd never go anywhere with it. It would just sit there like my NexStar 11 GPS 110 lb beast.

Mount looks great and indoors the electronics seem to work as expected and personally I think the sound is cool.


I finally have my new scope on it, and using it indoors, it's been too cold out, the wobble/bobbing/bouncing is unbearable. 5-7 second settle down time with the pier extension on it. It's really like a wave, it starts from the scope through the head into the pier and back again. I can watch the wave happen externally, don't even have to be looking through the eyepiece. Up to 7 seconds in AZ mode, 5 seconds in EQ mode.

Trying to focus is almost impossible. Just touching the scope gets the scope bobbing and weaving. I'm picturing any amount of wind keeping this thing bobbing all night. I've read people that are happy with their 8" newts and 127 refractors on this thing, you think it could handle my 125 refractor. I've also read of people with 80mm refractors and 8" SCT's that have an unacceptable wobble.

There doesn't appear to be much if any backlash when using the controls, so I'm not sure that doing the worm gear adjustment procedure mentioned in our forums would help, or at least help enough. Or would it?

After consulting with my vendor, I can reduce the wobble by removing the pier extension and using it in EQ mode. I've gotten it down to a touch more than 3 unpleasant seconds, but it still wobbles too much during focusing. But I'm not going to use it without the pier or in EQ.

I would really truly appreciate help from anyone who has solved the wobble/bobble/bouncing issue with this scope before I decide to return and upgrade to a larger mount. There may be something that some of us are just overlooking because it works well for others.

Thank You! TK

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ATM, Optics and DIY Forum / Possible Problem beyond Collimation
« on: December 26, 2017, 07:07:22 PM »
Hi all,
I have submitted on the Reflector forum a difficulty I am having using a 6" F5 Newtonian I purchased second hand, here is the link;


I had the odd experience last night while attempting to focus on Jupiter of the picture seeming to split into three as I defocused it!

I have tried quite a number of things to correct the issue of not having the ability to bring the extent to focus.

I suspect the first issue was a bent spider / secondary holder, then an offset secondary in which it is glued into the ali slug that screws the spider.

 I am totally foxed as to what's up.

Any canny info?


Chris (UK)

Mounts Questions & Expirience / 10Micron tripod
« on: December 24, 2017, 07:20:38 PM »
Hi, are there any recommendations about a fantastic tripod for your 10Micron 1000.  There certainly is the Aries but it sounds very pricey and bulky.  Has anyone tried the Avalon Tpod 110 ?  It is rated for 100kg, works directly with the 10Micron 1000hps and looks fantastic (plus Excellent reviews) and is mild (7kg)
Thank you

Reflectors Telescopes Forum / hubble optics UL18"
« on: December 24, 2017, 06:32:27 PM »
I only wanted to know if this scope isn't any good.  Its just $3000.  Its a great bargain if its worth it.  Much cheaper than an obsession.  Whats the difference in views between a 8" and 18"

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