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Messages - skelevchasul

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1
ATM, Optics and DIY Forum / Re: New dedicated topic on wire spiders
« on: February 09, 2018, 08:55:14 AM »
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A very cheap way to tension the wires is to use violin tuning pegs, 2 bucks for 4 pieces and free shipping. You would need to drill a tapered hole.

FWIW Itried a wire spiderand it worked but was never as rigid as a vane spider, always had some vibration. I concluded that a 3 vane spider (if you make it) can use as thin or thinner vanes than guitar strings, has less obstruction and 6 spikes are faint and unnoticed except on the brightest star.

That's cool. The guitar adjuster have the advantage of a worm gear that provides finer adjustment.

Three vane spiders allow some rotation of the diagonal along the tube axis. Four vanes with the >o< configuration eliminate this. Some people use curved spiders which ought to be pretty floppy if they are thin.

I haven't heard that rigidity complaint about wire spiders before. Anyone else?

2
I have an 80ED and a 8" SCT. After reading soooo many posts about people using Dobs, I decided to get one to see what all the fuss was about? So I got a 10" Dob to just take out and cruise the sky with a low power wide angle eyepiece. Pointed it up to the Cygnus and wow, so many stars and a nice wide view. Finally found the elusive Viel nebula in it! Star clusters are among my favorite objects to observe and this scope is great for that. I added a green laser along with the 8x50 finder and I can find things pretty easily, most of the time.

The weight of it is just at my limit, so that's good. Great investment and a fun scope to use.

3
Mounts Questions & Expirience / Re: AVX Mount Alignment - Pick the Stars?
« on: February 04, 2018, 10:30:31 AM »
I don't think there is anything special about the alignment stars offered by the HC. They are just the brightest stars up there at fairly high altitude - so you are free to change them as you wish. You just don't want stars that are very close to each other.

If you don't like scrolling a lot, then you can aim to choose names that are near each other in the alphabet. And note that you can go 'up' to get to the z's, y's etc. because it "wraps" as you go through the list.

If you aren't sure of star names you can use the Celestron SkyPortal app and enable its compass so you can hold it up to the sky and basically read off the name. Then use the up/down keys in the hc.

This is helpful for me in the southern hemisphere because I don't know the star names here well - but unfortunately the star names in the app are often different from the ones offered by the HC. So you have to be prepared for that.

The most important thing to avoid, if you don't know the stars well, is to align on the wrong star. If the alignment really gets confused you may need to do a factory reset. That's why it can be good to use double stars like Almach to give you confidence you have the right star.

Frank

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ATM, Optics and DIY Forum / Re: Cant afford vantablack?
« on: February 03, 2018, 06:33:04 AM »
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and many black things (especially anodising) cease being black beyond the very deep red.
Yep, but I have found a company that has a anodizing recipe that is black into NIR, Pioneer Metal Finishing does it.

5
ATM, Optics and DIY Forum / Re: Another simple homemade collimation tool...
« on: February 02, 2018, 10:36:13 PM »
Well, it's taken nearly another year, but I made a 2" version of this "Conimator" (CONical collimator) for myself and am planning on making a slightly shorter one tonight for an observing buddy who recently acquired a classic 8" f/4.5 Coulter dob.

I did it in much the same way as with the 1.25" version, but with O-rings that have a 1 7/8" OD (from Menards at $0.59/each) that are stretched to provide about 2.010" OD measured softly with calipers. I waited until I had upgraded my focuser to a low profile Antares 2" focuser make one for myself to verify each of the length dimensions.

This is what it looks like:And when plugged in to the underside of the drawtube in my scope:It works great! The 1/4" through hole slightly stops down the diverging beam of my laser, but still produces a spot a couple inches in diameter on the primary. The return shadow is very easily seen from the end of the scope due to the conical shape of the target.

I also took a green laser pointer, wrapped it in a couple yards of electrical tape until the tape collar was about 0.130" and stuffed that directly into the barlow for a bright daylight-visible shadow of the center ring. The tape provided enough friction that I could easily tip and align the laser to illuminate the center of the primary, and it didn't need to be held to stay there. After first collimating in the dark with a red laser collimation tool in a barlow and pointing through the device, I verified it with room lights on with the green laser pointer! This means precise barlowed laser collimation of a primary can be done with a laser pointer, some tape, a barlow, a piece of turned wood, and a couple of O-rings!

I can see how this would work really well with a truss dob without a shroud. The centering of the shadow on the cone could be seen from the base of the scope while collimation is being tweaked.

The pulley-shaped collar makes it easy to grip when installing and removing this "stopper". The length of the portion that goes into the drawtube is just short enough to avoid interference with the bottom of the barlow inserted into the other end. The wood is turned about 0.005" (1.995" diameter) undersized to ensure the O-rings center it well when slightly compressed. The 7/8" length at the intermediate diameter is just for clearance through my 3/4" focuser board, which has a 2.5" through hole. Depending on the scope this could be shorter, or eliminated--as I'll do tonight for Steve's dob.His drawtube extends slightly into the inner wall of the OTA. My focuser drawtube barely reaches the outer wall. Longer would work, but in extreme cases may create clearance issues to the secondary for installation and removal. Steve's will look more like my design sketch a few posts back since he has only a few inches between the bottom of the drawtube and the secondary.




6
So, this is a continuation from a topic that I posted about this refractor, the Explore Scientific ED102 APO. My one issue is that I need a good mount, I had decided on the Vixen Porta 2 but everyone else said that it would not work with this scope of around 13lbs with everything on it. My other options were the Orion VersaGo, and the... that was really my only other idea, I'd like to get a nice Alt/Az mount around $200 or so dollars and is should be able to carry at least 15lbs of weight. I have really only seen the VersaGo as a good option but I know I'm still cutting myself short so I would like your advice. Anyway, I would really appreciatesome advice and would love some suggestions for a good mount, I thank you for the help and look forward to learning more about the mount I will get.

7
Beginners Forum / Re: children using telescoop (on equatorial mount)
« on: February 02, 2018, 07:25:05 PM »
The Skywatcher Skyliner 150P breaks down into two components: the optical tube, and the alt-azimuth base. The optical tube weighs 5.8 kg, or 12.8 lbs; and the base weighs approximately 10 kg, or 22 lbs. The heavier base is necessary for the stability of the telescope kit overall, and when observing. If the weight seems a bit too much, there are ways of moving it about, with a garden-cart or other.

In future, to get the widest field-of-view and the lowest magnification with a 6" f/8 Newtonian, this 2" 32mm 70° eyepiece would be an ideal; to help enable the telescope, and the observer, find things more easily; and pictured here on the right...

http://www.firstligh...-eyepieces.html

Once an object is spotted, but is too small to see any details, then an eyepiece of higher magnification can be put in its place for a closer look.

The 2" 32mm compared to a 1.25" 25mm, the latter supplied with the telescope kit...
In seeing the 32mm, one might imagine just how wide and wonderful the views through it would be; for observing the Andromeda galaxy and the Pleiades in winter, and for cruising the Milky Way in summer. It would probably be the only 2" eyepiece ever needed or desired. All of the shorter eyepiece focal-lengths below 32mm can perform quite well in the smaller 1.25" barrel-format.

The 32mm(38x magnification), the 25mm(48x, included with kit) and the 10mm(120x, included with kit) would serve well in the beginning.


8
We fix our light problem with a small cheap laser. When ever i view, I take a small red laser (the one i use to torment my cat) mount it to a chip clip and aim it at the photo cell of the street light....works like a charm. When I'm done observing it returns to normal operations with 30 seconds. Just sayin

9
Reflectors Telescopes Forum / Re: Simple secondary dew prevention for Dob
« on: February 02, 2018, 03:53:20 PM »
Yeah, $200-$250 is about right. The heat strips are going to cost about $25 each and you need at least 3 (eyepiece, telrad, and secondary). Controller is $100ish. Battery $30-$50. Charger maybe $30 or less. 12v dryer $15.

Try a simple homemade dew shield to start and the 12v dryer. Maybe it'll work out well for you for a few hours. But the telrad and eyepiece dew can shut you down for the night. So back to dew equipment.

I have 2 identical 17mah sealed batteries and a battery charger that I use for star parties. One is a backup battery just in case I forget to charge a battery or one dies.

The upside is that not every not is going to be a dew filled evening.

10
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Is there a situation where a Plössl would be a better choice for viewing than a Nagler? It seems to me that a Plössl can't do everything a Nagler can do, but a Nagler can do everything a Plössl can do - better. Is this wrong?

No, you are not wrong as far as I am concerned.

I was using Plossls many years ago when I couldn't afford Naglers, but there is absolutely NO situation today where I would select a Plossl over a Nagler -especially for planetary viewing - unless my budget was too tight to afford one.

Why? Because aside from the atmosphere - which we cannot control - the bestthing a planetary observer can control is their personalComfort. You have to be comfortable to sit quietly and study the planet for many, many minutes at a time in order to catch those faint breaks in the atmosphere that give you the best view.

I have owned and used CZJ orthos, ZAO-I and ZAO-II orthos, Plossls, and any number of other "minimal glass", super tight eye reliefeyepieces and they don't help me as much as a nice comfortable Nagler, Radian, Pentax XW, Delos, DeLite, or Ethos when it istime to sit down and study a planet.

My .02,

Ron
Sometimes I read a post and it is right on the money and I think everyone should read it twice.. Ron did good with this one.

Jon

11
Definitely strange behaviour. After 15-20 stars usually I obtain deviations of around 5" RMS in the model.

Are you sure there is no movement somehow inside the scope (mirrors, lenses) while doing the alignment? That can seriously mess up any model.

D.

12
Reflectors Telescopes Forum / Re: Dobstuff Base for a 12" Lightbridge
« on: January 30, 2018, 03:51:44 AM »
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<p class="citation">QuoteI would not be surprised to find strategically placed, sized, and shaped holes in a professionally designed plywood base that minimizes weight while making the base every bit as rigid and stiff as it needs to be to do its job, but not more so.
I am sure the majors use CAD systems to design the factory bases, but i doubt there's much rigorous engineering work done to specify rigidity/stiffness and achieve this specification at minimum weight. They have great deal of practical experience though, so they know what works and doesn't work, but are not too concerned about what works best.
I doubt that the small shops that build aftermarket bases do this kind of rigorous design work either. One small manufacturer that I spoke with touted the beauty, longevity, and light weight of his bases, but couldn't say how much the finished base would weigh.
I agree that it without significant engineering analysis it would be difficult to quantify the numbers but I think it's pretty straightforward to build a base that is significantly lighter and stiffer than the commercial bases, if only because of the advantages of proper construction and a superior material.
[/quote]
I agree. As i said, it's probably reasonable to expect a line-for- line copy of a factory particle board base executed in high quality plywood to weigh less and be more rigid and stiff than a factory base.

It will be better and sometimes better is good enough. However, someone who needs a base that meets a set of specifications for lightness and stiffness will not be satisfied with a base that's lighter and stiffer, but not sufficiently light and stiff to meet specifications. For this person, it's an crapshoot.

Put another way, I don't want to merely make my telescope better (lighter and stiffer) than it is today, my goal is to make it better than another telescope that i own, which requires meeting specific requirements. If I can't improve the telescope enough to meet my goal, i have no need for it and intend to sell it.

13
Beginners Forum / Re: Power/Aperture question
« on: January 26, 2018, 01:38:06 AM »
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Saturn was the clearest at 48X. At higher magnification it was not much larger yet moved more rapidly. I need to work on planetary skills.

M13 was nice at 120X. High enough to see individual stars on the rim while still showing a bright center of the cluster. Any higher and yes it filled the eyepiece but turned into a dark grey blob. That being said I very much enjoyed M13 at a bright 48X right next to it's two buddy stars. I guess I was surprised to see the image dim so quickly with increasing magnification considering it is bright enough for a beginner like me to easily find it with cheap 10x32 binoculars.


Last week I saw M13 for the first time, and it was truly magnificent. I viewed through my 8" dob with 120X magnification and could see many individual stars across the whole field. Then a few days ago I looked at it again and saw only several individual stars against a blob of whiteness; less spectacular, though if I hadn't previously seen it looking much better I think I would still have been impressed. Same equipment, different nights. It can make a big difference. I'm trying to slow myself down in the hunt for new things and spend more time with each object and go back frequently to things I have previously found, and learn many things including the importance of atmospheric turbulence.

As for Saturn, I have viewed it at 48X and 120X (my only current options) and find that the view is crisper at 48X, but more detail can be seen at 120X, such as the Cassini division. Under good conditions the higher magnification provides the more interesting view (to me, but my 10mm eye piece has 100 AFOV, so things stay in view for quite a while), but if conditions are not so good the color tends to wash out.

I'm pretty new at this, but since we seem to be looking at the same things with similar equipment I thought I'd chime in. Cheers!

14
Beginners Forum / Re: A very tough decision on my second scope!
« on: January 23, 2018, 06:36:26 PM »
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I think I'm beginning to lean more towards the C8 as it seems to be more versatile overall and can give me pleasing views of fainter objects, but I'm just not 100% sold. On the other hand the convenience of the frac is really hard to overlook and I'm sure it could keep me busy on the objects it could show me. Are there any other 100ED fans out there that could beat some sense into me?

Have both;100ef on manual az-el is hard to beat for quick into action.
An older C8 on wedgepod mount is also quick to set up-cooldown can be a modest delay.
Modern 8SE or similar with computer and goto is a bit more demanding of time and power and alignment but can potentially show you the most.

A universal tool is one that does all jobs equally poorly....

15
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...Realistically what you've described results in a well aligned scope. Theoretically offset is in order regardless of f/ ratio but so small it doesn't matter in reality in a lot of cases. While orthogonality may be a concern mechanically, it doesn't matter to collimation. Tilt of the eyepiece to the optical axis matters. Being able to see the whole objective matters. Doesn't matter if the secondary isn't centered as long as it's large enough to intercept the primary light cone....


In practical collimation, you (preferrably, at least) use the focuser center axis as the starting "point" or rather line, for the intended collimated optical axis. If this is what you do, the focal plane will by definition be perpendicular to the focuser and thus parallel to the focal plane of the EP, or (hopefully) to the detector chip.

Please note: this is precisely why "squaring" of the focuser is not critical!

"Optical centering" of the secondary, or more precisely expressed, centering of the fully illuminated field, is an entirely independent and different thing. So is centering the optical axis within the tube (or more exactly making the optical aim perpendicular to the altitude or declination axis).
Nils Olof

Exactly. The focuser defines the eyepiece, and thus defines the optical axis, to which everything else must conform. Collimation is all about bringing the primary mirror's optical axis into alignment with the eyepiece's optical axis. Of course its a relative relationship, but as the primary mirror generally has collimation adjustment and the focuser generally does not, then its most logical to think of the focuser as defining the optical axis.

Confusion arises, I think, because the human brain tends to get distracted by the telescope tube's mechanical axis, against which all the mechanical adjustments for setting the optical axis work. To make it worse, each component in the optical train have limited axis of movement, requiring non-intuitive combinations to achieve collimation. A stewart platform hexapod truss system cures that misperception by making the tube itself the only variable; and with no less than 6 axis of movement available, collimation is achieved very simply and intuitively, bring all axis together - optical and mechanical - in one simple step.

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