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Messages - Aaron Romano

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1
Beginners Forum / Re: Which Telescope to get for Christmas
« on: February 09, 2018, 09:06:46 AM »
Take a look at post 20 for things to look at and how to find them when you get the scope.

2
Thanks Danny.
I've yet to see if the tool edges are thick enough so the edges can thin and extend to its central depth without too much thinning, and with the edge sufficient to provide the thickness for the F5 depth required, but this hogging with the mirror on top will be quite and effort towards reducing from the12.5 F8 to the deeper F5.
jim

3
Beginners Forum / Re: Looking for New Telescope
« on: February 08, 2018, 07:07:21 PM »
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Another factor is that the Dob base tends to protect the mirror from the ground as well as the observers body heat. With a GEM or ALT-AZ mounted Newtonian I sometimes find that the open tube bottom is near my legs or feet and my body heat is affecting the view.

Personally, I prefer the Dob mount because of its inherent stability. In the larger sizes, it is really the only practical way to mount a Newtonian. Some observers mount an 8 inch on a Tripod and Alt-Az mount, never seen a 10 mounted that way.

Jon

4
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I need an artificial star so I can test indoors without the atmosphere, though near focus would be an issue.

There is no seeing in a couple hundred feet of air. Use a Christmas tree ornament or a ball bearing about 200' to the north to catch a reflection of the sun.
This will make a nice bright "artificial star" to use for both optical evaluation and collimation.
You will typically see multiple diffraction rings in focus and your out of focus image will show errors easily.
I once tried using Jupiter for a star. All the waves averaged to a single even disc. I have my doubts about a Christmas ball.

Why would you bother trying it with Jupiter and why would you have your doubts about a Christmas ball? In the case of the 1st one I gather you figured out it doesn't work and in the case of the second one it has worked quite well for me for more years than I can remember.

5
Beginners Forum / Re: Collimation
« on: February 03, 2018, 10:37:59 AM »
How to Collimate an Orion Dob using a Collimation cap or laser
https://www.youtube....h?v=YAVGcGEBmCE

I use the cap. Very easy.  I did buy a laser but sent it back and decided to stay with the cap.

6
I'm getting ready to buy a fixed length focal length eyepiece or two for use in both a 140mm-f/7 refractor with a 980mm focal length and also in a 100mm-f/9 refractor w/ 900mm focal length and in research "exit pupil" size is referenced. Is that the same as the size of lens of the eyepiece? Is there an optimal exit pupils size and if so how is that figured out?

thank you!

7
Reflectors Telescopes Forum / Re: pv wave & rms
« on: February 02, 2018, 06:24:42 PM »
I sould say this too. The RMS figure and the PV figures you have are out of whack and the .021 figure seems suspect to me.

If the PV rating is .139, it would be hard to see how the mirror could have a Strehl of .98 because that is the Strehl you would get if you convert the RMS of .021 to Strehl.

Still, that is the problem with PV. It can be horribly misleading.
And that is the problem with RMS. It does not produce an "Intuitive" evaluation of quality because of the fractions can be somewhat abstract.

Anyway, converting the .021 RMS figure to Strehl gives .98, and that would be an amazingly good mirror, though with a PV of only .139, I would be curious as to where the big PV variation was.

That is why having a wavefront simulation is valuable, but if the RMS number is accurate, then it does not matter because the mirror is essentially prefect.  In fact, almost too perfect.  But those are your numbers and we have to assume that they are correct for purpose of this conversation. And if they are, you have one of the most perfect mirrors I have ever seen a test for.

8
Beginners Forum / Re: Need to pull eyepiece out just a little to focus
« on: February 02, 2018, 05:24:07 PM »
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While not necessarily common, it is not unusual to have to hold your eyepiece out a bit to get it to focus.

If all your other eyepeices are usable and your focuser is not too far out, it certainly is not a problem.

One of the most common causes for this is that your primary mirror may have migrated up the tube a bit thrugh the years.

Aftereachcollimation, the mirror is in a slightly different location. If you usually start with the same adjustment screw, and move the mirror up in doing so, you then go for the other screws, and the net effect is that the mirror comes to collimation a touch further forward.No big deal,just move your focuser tube out a little. But through the years, it adds up.

Check your mirror cell. How far forward is your mirror. How far screwed in are the adjusters. Just move them all back. they probably have half an inch or more of travel, and if at the most forward extreme, could be readjusted to remove a half inch ormore of focuser (or in your case, make it so the 12 mm eyepiece needs to be fully in the tube. Don't move it so far your closest focusing eyepiece cannot come to focus.

Alex

Good to know. I have found this to be an issue with my reflector also.

9
Light Pollution Topics / Re: Senior home light behind my house
« on: January 31, 2018, 09:38:11 AM »
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There's a small senior home behind a small amount of trees next to my house. The lights from the windows and whatnot aren't annoying, but there's some sort of spotlight or whatever on the right side of their parking lot. Recently a lot of trees between us and them have been cut, and with the leaves gone the light shines directly onto my property and blinds me a lot while I'm observing.

My parents have basically told me that all efforts to ask them to shield it, etc. are futile because it's a senior home (they've gotta keep their residents "safe") and it's not shining in our windows (so we have no legal grounding). Is there anything I can do to get that light to stop shining onto our property without having to have an annoying screen or shield two feet in front of me all the time while observing?

Who decided to cut the trees? I find that horrendous that someone would do that. Don't put up a screen, buy some really tall evergreens and put them up as a natural barrier on your property and/or a large mirror to reflect the light back at them.
Evergreens would either be too expensive or take too long to grow. A giant Mylar reflecting mirror.... where would I get that?

<p class="citation">caveman_astronomer, on 14 Nov 2017 - 11:58 AM, said:<a href="https://www.cloudynights.com/index.php?app=forums&amp;module=forums&amp;section=findpost&amp;pid=8212942" rel="citation">[/url]<blockquote class="ipsBlockquote built" data-author="caveman_astronomer" data-cid="8212942" data-time="1510653516">

Not enough is known in this case to offer anything but advice on using tarps. Complicating the discussion is the fact that the OP is not the owner or renter of the property being trespassed upon. The good news for the OP is that in a few years it will be feasible to choose a better place from which to observe if any still exist by then.

That said, if I owned the house, and the senior home cut down trees, leading to light trespass, I would definitely approach the owners of the senior home about the situation. They're being thoughtless, not necessarily malicious, and should be approachable. I would not tell them that I am an astronomer, as that is not the issue here. There would be ways for them to light their property without lighting mine, and the residents would have enough light to see by, safely.

There might even be some laws, codes or ordinances requiring a buffer of trees between a business (senior home) and a residence.

[/quote]
Hmm, I'll try looking up ordinances to see if there's anything. My parents have basically shrugged off the issue with "well, there's always going to a dark site a few times a year", "we're not suing", and "it's not shining in the windows so we don't care".

Another problem with the light is that it doesn't just illuminate my yard, but also the tops of the trees, which it bounces off of. Forgot to mention that.

EDIT: Have looked through zoning, ordinances, etc. with no luck. Seems our city regulates everything BUT lighting.[/quote]
So you haven't talked to the people themselves? I think you should, because it seems like you care more about this issue than your parents do. But if you're a minor, you can't bring forth a lawsuit on your own, so that suggestion might not work for you in case they deny your request.

10
Mounts Questions & Expirience / Re: CGEM DX Optical Encoder-broken
« on: January 31, 2018, 09:18:23 AM »
Funny how I am just now finding out my bore size on the encoder I received in Sept is too big and wondering what to. Also RLF55, can you be more specific on the wiring, that had me worried also if it was just a matched cut and splice.

11
Reflectors Telescopes Forum / Re: Orion Starblast 6i Intelliscope
« on: January 31, 2018, 06:57:03 AM »
Not much into satires.  My experience was that for bellow $450, it was a very cost effective 6in grab and go choice.  But it isnt a premium scope. Unless you want to kneel, you need to put in on something.  It has very good alt-az movement for a modified budget dob, but it ain't a teeter! Tracking at high mags with such a short focal length on a one armed bandit took me some practice and patience.  And the focuser is what it is, a r and p on a one armed bandit.  Takes time to settle at higher mags.  But with the price point considered, these innate deficiencies are easily overcome by the sweet views it offered. Compromises.I still regret getting rid of it.Clear skies, cjm

12
Beginners Forum / Re: Have to focus all the way out?
« on: January 31, 2018, 02:22:31 AM »
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If it's not focusing at all, then you need to collimate it.

I collimated It after I adjusted the mirror. It’s possible I was I was trying to focus on an object too close. I tried again on a tree farther away and I think was able to focus.

It’s also possible to adjust the mirror such that the focus plane falls outside the range of the focuser though, right?
You would need several inches of movement for that to happen. I don't think you're in danger of that.

13
Mounts Questions & Expirience / Re: AVX Question
« on: January 30, 2018, 01:08:22 PM »
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Remove the plastic ring under the saddle, you mean?  I've seen that suggested, and also replacing it with a much thinner one (so it is just a space filler, not load bearing).  (Earlier in this thread, in fact.)  Hmmm... I want to test it the way it is first.

Yep, that's exactly what I mean. I didn't notice any thread locker but I do remember the bolts "popped/cracked" when I loosened them. I just didn't understand why when I put the saddle back on the dec axis got so tight. I did back them off a bit but could never get good free movement that didnt leave the saddle a bit loose. That's when I took the plastic bearing out and things got way better.
This is the way I see it...
If you notice, the 4 bolts screw into center part of the drum that sits slightly higher than the outer ring. The only time that bearing comes into play is when you release the clutch such as when balancing. When the clutch is tightened then both pieces are locked together and the bearing does nothing. If removing the bearing causes metal to metal contact, I'm sure my Dec axis wouldn't move as freely as it does and I only put a small coating of Super lube on the outer ring before putting the saddle on.
I know this goes against the "norm" and can seem a bit radical but it only takes a minute to try.

14
Eyepieces Questions & Recommendations / Re: Did I make a mistake?
« on: January 25, 2018, 10:14:54 PM »
Well you certainly did not make a mistake buying that scope. That Celestron 9.25 is a real sweet spot. And the zoom's a fine match for it. The short focal length ep may be a bit of a stretch but when that night comes along where conditions are just right and you pull in a planetary nebula at that mag, all will be forgotten except the killer view. It may seem odd but the southern plains can have much better high magnification viewing conditions than the mountains, which can generate high levels of turbulence. When the jet steam hangs up north and a cold front passes through leaving a still, clear air mass in its wake, tiny exit pupil observing can be very rewarding indeed. IMO, planets are best @ 175-250x but those PN's and some galaxy clusters really can take the mag. From the club dark site in SE Oklahoma, observing at 446x is not uncommon and we recently had a fine view of M57's CS at 600 and 839x.

Don't minimize the value of supplying yourself with the widest field your scope can manage. That ES68 40mm would be a fine match for many larger objects and show low surface brightness objects well.

So I say no, y'all haven't screwed the pooch yet. Not in the least. Now you just need to find a dark site and go observe. Try to wear all that new gear out.

15
Mounts Questions & Expirience / Re: USED CGEM problems with Power Jack.
« on: January 23, 2018, 04:16:24 PM »
Hello Wayne,

Hey good job straightening that shunt lever.

No, I have not swapped it out yet. I measured the dimensions and they are very close. Total length as measured 0.930 (ref. 0.915), the sleeve thread is a match 5/16. Sleeve length as measured 0.339 (ref. 0.315). The terminal measurements are very close also. I just held the jack up to the board solders and the terminals match exactly.

The Switchcraft jack appears to be a "little" more heavy duty. The pin is definitely thicker. In comparing the new jack to the installed one I can see how crushed the + pin is on the old one, so I've pried it open with a tiny screw driver, as mich_al suggests. (I was afraid to do that cause I was afraid it might break, however it did not).

I also got some matching lock plugs, the plugs are Switchcraft P/N 767K. The 767K plugs also match the stock jack well, they lock nicely, mate well. They are much heavier and finer, nice build.

There is also a rubber plug cap I bought too. Switchcraft P/N 502-JCAP. This plugs the jack when not in use.

I can't solder this, no way. If the epoxy doesn't work out I'll pay someone to solder the new jack in, I have a few shops who would do it. Estimates are running $30.00 - $50.00 (I supply the new jack part.)

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